Controlled flight into terrain involving Cessna 404, VH-OZO

flying an approach in instrument meteorological conditions (IMC), the pilot’s workload was elevated due to conducting an immediate entry into the second approach, conducting the approach in a different manner to their normal method, the need to correct lateral tracking deviations throughout the approach, and higher than appropriate speeds in the final approach segment. The pilot had the required qualifications and had been regularly logging RNAV GNSS approaches, although these approaches were almost all conducted in visual meteorological conditions. However, their workload was potentially further exacerbated by having limited recent experience in conducting RNAV GNSS approaches in IMC. The aircraft had sufficient fuel to conduct the flight from Cairns to Lockhart River and return, with additional fuel for holding on both sectors if required. In addition, there was no evidence to indicate any organisational or commercial pressures on the pilot to complete the flight, but the extent to which self-imposed pressures or incomplete knowledge of procedural requirements influenced the pilot’s performance could not be reliably determined. The aircraft was not fitted with a terrain avoidance and warning system (TAWS). Given the aircraft’s descent profile on the second approach, if a TAWS had been fitted and been operational, it would have provided the pilot with both visual and aural alerts of the approaching terrain for an extended period. There was no requirement in Australia for piston-engine aeroplanes (such as VH-OZO) to be fitted with a TAWS. Although the Civil Aviation Safety Authority (CASA) had been considering changes to TAWS requirements since 2008, the Australian requirements at the time of the accident for some types of small aeroplanes being used for air transport operations were less than those of comparable countries and they were not consistent with International Civil Aviation Organization (ICAO) standards or recommended practices. More specifically, although there was a TAWS requirement in Australia for turbine-engine aeroplanes carrying 10 or more passengers under the IFR, there was no requirement for piston- engine aeroplanes authorised to carry 10 or more passengers (an ICAO standard adopted as a requirement by many comparable countries) and no requirement for turbine-engine aeroplanes authorised to carry 6 to 9 passengers (an ICAO recommended practice adopted as a requirement by many comparable countries). However, even if these changes had been introduced in Australia prior to the accident, it is unlikely they would have resulted in an aeroplane such as VH-OZO being fitted with a TAWS. The aircraft was fitted with 2 Garmin GNS 430W GPS units that provided navigation and radio communication capability. As part of the unit’s navigation capability, there was also a terrain awareness function capable of providing visual pop-up terrain alerts. However, that functionality was not to the same standard required for a TAWS installation. It could not be determined whether this function was selected on by the pilot during the accident flight. Although the GNS 430W unit was suitable for an RNAV GNSS approach and other non-precision instrument approaches, it did not provide vertical guidance information, which would have explicitly indicated that the aircraft was well below the recommended descent profile. CFIT accidents have been a significant problem over many years, although the rate of such accidents has been decreasing. However, risk factors still remain, particularly for smaller operators. Ideally, in order to minimise the risk of CFIT, operators conducting passenger transport operations under the IFR would use aircraft fitted with a TAWS and/or have a GPS/navigational system that provides vertical guidance during non-precision instrument approaches. › iii ‹ Nevertheless, even without these systems, there are other means available for such operators to minimise CFIT risk. In this case, the operator had specified a flight profile for straight-in instrument approaches and stabilised approach criteria in its operations manual, and encouraged the use of stabilised approaches, but there were limitations with the design of these procedures. In particular, the operator’s stabilised approach criteria specified an applicable height of 300 ft above aerodrome elevation for operations in IMC. A similar problem has also been identified in multiple other operators conducting passenger transport operations under the IFR. Although an applicable height of 1,000 ft in IMC has been widely recommended by ICAO and many other organisations for over 20 years, CASA had not provided formal guidance information to operators in Australia regarding the content of stabilised approach criteria. There were also limitations with the operator’s other risk controls for minimising the risk of CFIT, including no procedures or guidance for the use of the terrain awareness function on the aircraft’s GNS 430W units, and limited monitoring of the conduct of line operations. What has been done as a result On 2 December 2021, Civil Aviation Safety Regulation (CASR) Part 121 (Australian air transport operations – larger aeroplanes) and CASR Part 135 (Australian air transport operations – smaller aeroplanes) commenced. Associated with these regulations, piston-engine aircraft being used for air transport with a maximum operational passenger seat configuration (MOPSC) of 10 or more were required to have a TAWS and operate under Part 121, with the applicable dates dependent on the MOPSC and other factors. In December 2021, CASA also published guidance material for CASR Part 121 and Part 135. This included guidance information about stabilised approach criteria, including advice regarding applicable heights for stabilised approach criteria in IMC, including an example height of 1,000 ft above aerodrome elevation in IMC. Associated with the introduction of CASR Part 135 in December 2021, air transport operators of smaller aeroplanes were required to conduct a flight crew member proficiency check at intervals of 6 months (for IFR or night VFR operations) or 12 months (for day VFR operations). Safety message All operators conducting air transport operations under the IFR should evaluate the risk of CFIT in their operations. In addition, any such operators that do not currently have a TAWS fitted to their aircraft should recognise the substantial benefits of a TAWS, and be actively seeking to install a TAWS to maximise the safety of their operations. In addition, there are many other lessons for operators of small aircraft to reduce their CFIT risk. These include: • If a TAWS is not currently viable but they have aircraft with a GNS 430 or similar system that provides a terrain awareness function, fully understand the nature and limitations of this function and develop procedures and guidance for pilots about its operation (particularly for instrument approaches or operations in IMC). • If not already fitted, actively seek to upgrade their GPS/navigational system to one that provides vertical guidance information on non-precision instrument approaches. • Develop (or review) flight profiles for instrument approaches that provide clear guidance regarding the expected configuration, speed and other requirements at key stages of the approach. • Develop (or review) stabilised approach criteria in line with best-practice industry guidance and ensure that the applicable heights or reference points are suitable for straight-in approaches and operations in IMC. › iv ‹ • Review the frequency and content of flight crew member proficiency checks to ensure they provide sufficient opportunities to monitor the way instrument approaches are being conducted during line operations (noting that such checks for IFR operations conducted under CASR Part 135 are now required every 6 months). In addition, such operators should consider options for obtaining and reviewing recorded flight data of normal line operations for continuous learning purposes. › v ‹ Contents Executive summary..................................................................................................................i The occurrence ........................................................................................................................1 Overview 1 Planned flight 1 Flight to Lockhart River 1 First approach at Lockhart River 5 Second approach at Lockhart River 7 Collision with terrain 9 Context ................................................................................................................................... 10 Pilot information 10 Qualifications and experience 10 Lockhart River experience 11 Proficiency checks and flight reviews 11 Observations of the pilot’s approach to safety 13 Recent history 13 Medical information 13 Aircraft information 14 General information 14 Seating 14 Aircraft instruments and systems 14 Altimeters 17 GNS 430W overview 18 Garmin TERRAIN function 19 Configurations and speeds 21 Aircraft maintenance 22 Terrain avoidance and warning systems 23 General description 23 Australian requirements 23 International requirements for turbine-engine aeroplanes 24 International requirements for piston-engine aeroplanes 24 Considerations of changes in Australia 25 Aerodrome information 26 Meteorological information 27 Weather forecasts - overview 27 Aerodrome forecasts 27 Graphical area forecasts 28 Weather conditions - overview 28 Aerodrome weather reports for Lockhart River 29 Automatic weather station 29 Automated weather information service 30 Weather radar information 31 Local weather observations 33 Instrument approaches 33 Overview 33 RNAV GNSS approach design 34 Approach waypoint naming convention 37 Conducting an approach 37 Descent below the minimum descent altitude 38 Lateral tolerances 38 Handling speeds 41 Instrument flying and workload 41 RNAV GNSS approach workload 43 › vi ‹ Recorded flight data 43 General information 43 Altitude during approaches 45 Lateral position during approaches 46 Groundspeed during approaches 47 Wreckage and impact information 48 Survivability aspects 49 Organisational information 50 Air Connect Australia 50 Operator proficiency checks 50 Monitoring of pilot recency 51 Regulatory oversight 52 Operational information 53 Pre-flight planning and in-flight monitoring 53 Fuel calculations 54 Weight and balance 54 Communications during approaches 54 Electronic flight bag and approach charts 55 Flight profiles 55 Stabilised approach criteria 57 Prior missed approach during an RNAV GNSS approach (22 January 2020) 60 Review of the pilot’s recent RNAV GNSS approaches 61 Controlled flight into terrain 63 CFIT accident data 63 Efforts to reduce CFIT accidents 65 CFIT mitigation strategies 65 Operator’s CFIT risk mitigation 66 Safety analysis ...................................................................................................................... 69 Introduction 69 Weather conditions 69 Conduct of the approaches 70 First approach and missed approach 70 Second approach – vertical profile 71 Second approach - lateral position 74 Second approach - indicated airspeed 75 Unstable approach 75 Factors influencing pilot performance 75 Introduction 75 Workload and monitoring 75 Instrument flying proficiency 77 Awareness of procedural requirements 77 Operational, social and organisational pressures 78 Summary 78 Risk controls for minimising the likelihood of controlled flight into terrain 79 Introduction 79 Design of the flight profile 79 Design of stabilised approach criteria 79 Fitment of a terrain avoidance and warning systems 80 Use of the GNS 430W terrain awareness function 81 Vertical guidance information 82 Monitoring of line operations 82 Hazard awareness training 83 Summary 83 Findings ................................................................................................................................. 84 Contributing factors 84 Other factors that increased risk 85 › vii ‹ Other findings 85 Safety issues and actions ................................................................................................... 86 General details ...................................................................................................................... 92 Glossary ................................................................................................................................. 93 Sources and submissions .................................................................................................. 95 Appendices ........................................................................................................................... 98 Appendix A – Research and guidance regarding design of altimeters 98 Appendix B – Vacuum system analysis 100 Appendix C – Detailed 1-minute weather data Lockhart River 0850–0930 102 Appendix D – Guidance to industry regarding stabilised approaches 104 Appendix E – Aurukun incident flight – 22 January 2020 108 Appendix F – Related occurrences 113 Appendix G – Flight Safety Foundation CFIT Checklist 115 Australian Transport Safety Bureau ................................................................................ 119 ATSB – AO-2020-017 › 1 ‹ The occurrence Overview On 11 March 2020, a Cessna 404 aircraft, registered VH-OZO, was being operated by Air Connect Australia to conduct a passenger charter flight from Cairns to Lockhart River, Queensland. On board were the pilot and 4 passengers. The flight was being conducted under the instrument flight rules (IFR).1 Consistent with the forecast, there were areas of cloud and rain that significantly reduced visibility at Lockhart River Airport. After arriving at Lockhart River, the pilot commenced an area navigation (RNAV) global satellite system (GNSS) instrument approach to runway 30. The aircraft descended to an altitude of about 400 ft before the pilot conducted a missed approach. The pilot immediately commenced a second RNAV GNSS approach to runway 30, and during the descent the aircraft collided with terrain. Planned flight The passengers were contracted to carry out work at the local school at Lockhart River. The client arranged with the operator for the aircraft to depart Cairns at 0730 Eastern Standard Time2 on 11 March 2020, wait on the ground at Lockhart River for about 5 hours, then depart at 1430 with the same passengers for the return flight. The operator assigned the pilot who regularly conducted the operator’s charter flights. For the arrival at Lockhart River, the forecast weather was for light winds and rain and low cloud with periods of visibility reducing to 3 km in rain. There was also a 30% probability of thunderstorms. The pilot had submitted a flight notification, which specified IFR and capability for an RNAV instrument approach. The aircraft had sufficient fuel to conduct an approach at Lockhart River and return to Cairns and hold at Cairns for 1 hour if required. Flight to Lockhart River The aircraft departed Cairns at 0719 and tracked for the first planned waypoint on climb to its cruise level of 10,000 ft above mean sea level. Based on the forecast winds, the estimated time of arrival at Lockhart River was 0852. As the flight progressed, the pilot amended the estimated time of arrival to 0904. The aircraft’s track during the flight is shown in Figure 1. 1 Instrument flight rules (IFR): a set of regulations that permit the pilot to operate an aircraft in instrument meteorological conditions (IMC), which have much lower weather minimums than visual flight rules (VFR). Procedures and training are significantly more complex as a pilot must demonstrate competency in IMC conditions while controlling the aircraft solely by reference to instruments. IFR-capable aircraft have greater equipment and maintenance requirements. 2 Eastern Standard Time (EST): Coordinated Universal Time (UTC) + 10.0 hours. ATSB – AO-2020-017 › 2 ‹ Figure 1: VH-OZO recorded flight path from Cairns to Lockhart River, Queensland Source: Google Earth overlaid with OzRunways data, annotated by the ATSB At 0836, the pilot advised air traffic control that the aircraft was approaching top of descent, then tracking direct for the runway 30 RNAV GNSS instrument approach at Lockhart River, and the pilot requested traffic information. The controller responded there was no reported IFR traffic. At 0840, the pilot reported leaving 10,000 ft on descent and, at 0842, the controller advised the pilot of the very high frequency (VHF) and high frequency (HF) radio frequencies applicable to the rest of the flight. That was the controller’s last contact with the pilot and no further routine interactions with the controller were expected.3 3 In the Lockhart River area, VHF contact with air traffic services was not generally available below 4,500 ft. Outside of VHF coverage, pilots communicated with Flightwatch using HF radio. ATSB – AO-2020-017 › 3 ‹ During descent, the pilot transmitted on the common traffic advisory frequency (CTAF) for Lockhart River to activate the runway lighting for a period of 30 minutes. At 0852, the aerodrome frequency response unit (AFRU) broadcast ‘Lockhart River CTAF, runway lights are on’. At about this time, the pilot very likely obtained weather information from the automated weather information service (AWIS) via VHF radio. Notes taken by the pilot indicated the wind was calm, visibility was at least 10 km, there was broken cloud4 at 1,800 ft, broken cloud at 3,500 ft and overcast cloud at 5,300 ft, and the QNH was 1,008 hPa (see Automated weather information service). At about 0857, the aircraft levelled off at 5,500 ft. At this time the aircraft was heading to waypoint LHREB, one of 3 initial approach fixes (IAFs) for the RNAV GNSS instrument approach to runway 30 (Figure 2). The weather information indicated that the conditions were better than the landing minima (which were a cloud ceiling of 730 ft and visibility 4,200 m).5 4 Cloud cover: in aviation, cloud cover of the sky is reported using words/abbreviations that denote the extent of the cover. ‘Sky clear’ (SKC) indicates no cloud, ‘few’ (FEW) indicates 1–2 oktas (or eighths) is covered, ‘scattered’ (SCT) indicates 3–4 oktas is covered, ‘broken’ (BKN) indicates 5–7 oktas is covered, and ‘overcast’ (OVC) indicates that 8 oktas is covered. 5 Landing minima: specified meteorological conditions of cloud ceiling and visibility. In order for an aircraft to land at an aerodrome, the actual weather conditions need to be at or above the landing minima. ATSB – AO-2020-017 › 4 ‹ Figure 2: Lockhart River RNAV GNSS runway 30 approach chart Source: Airservices Australia, annotated by the ATSB ATSB – AO-2020-017 › 5 ‹ First approach at Lockhart River Figure 3 depicts the aircraft’s recorded flight track for the first approach and missed approach at Lockhart River. The altitudes described throughout the report are truncated to the nearest 100 ft. 6 At 0859:38, the aircraft passed abeam LHREB, commenced descent from 5,400 ft and turned left to track to the runway in accordance with the RNAV GNSS procedure. At 0901:25, the pilot made a radio broadcast on the CTAF, advising the aircraft was 10 NM7 to the south-east of the aerodrome, inbound to runway 30 and on descent passing 4,000 ft. Shortly afterwards, the aircraft passed the intermediate fix (IF) LHREI at 4,000 ft. Figure 3: Flight track of VH-OZO during first RNAV GNSS approach at Lockhart River Airport with times, feature labels, and approach parameters superimposed Source: Google Earth overlaid with OzRunways data, annotated by the ATSB At about 0903, one of the passengers sent a text message that contained an image of conditions outside the aircraft (Figure 4). At that time, the aircraft was over halfway between LHREI and the final approach fix (FAF) LHREF, at an altitude between 3,100 and 2,500 ft. The photograph had been taken through a passenger window on the right side of the aircraft cabin and, although there was significant cloud in the vicinity, some terrain/coastline was visible near the intersection of the wing’s leading edge and the engine cowl. 6 The ATSB obtained data broadcast by the automatic dependent surveillance broadcast (ADS-B) equipment fitted to the aircraft and GPS data transmitted from the pilot’s iPad with the OzRunways application installed. Further information on the aircraft’s recorded flight path during the 2 approaches is provided in Recorded flight data. 7 1 NM = 1.852 km ATSB – AO-2020-017 › 6 ‹ Figure 4: Image recorded by a passenger looking forward over the right engine and sent via text message at 0903 Source: Supplied, lower section of image cropped by the ATSB The aircraft continued the descent on the approach track and passed LHREF on descent through 2,300 ft. At 0904:27, the pilot broadcast on the CTAF that the aircraft was at 5 NM and on final (approach) to runway 30. The minimum descent altitude (MDA) was 730 ft.8 The aircraft arrived at the missed approach point (MAPt) LHREM at 0906:17 on descent through about 600 ft. The descent continued to about 400 ft then, about 1,000 m from the runway, the aircraft started to climb. The aircraft was passing 600 ft as it crossed the runway threshold in the early stages of a missed approach. In accordance with the missed approach procedure, the aircraft was turned slightly right to track towards the turning fly-over waypoint LHREH. At 0907:22, the pilot broadcast on the CTAF that they were conducting a missed approach for runway 30, tracking to the west then turning back to the east and climbing towards 3,500 ft (as specified for the missed approach procedure). After passing LHREH at 0907:43 on climb through 1,200 ft, the aircraft turned right to track east as prescribed by the approach chart. 8 The MDA published on the instrument approach chart was 830 ft and was based on the aerodrome forecast (TAF) QNH being set on the subscale of the aircraft’s pressure-sensitive altimeter. For this chart, the MDA could be reduced by 100 ft (to 730 ft) when using the actual QNH from an approved source. With the aircraft above the aerodrome and the actual QNH set, the altimeter indicates the approximate height above mean sea level. The aerodrome’s AWIS was an approved source for actual QNH and valid for a 15-minute period from the time of receipt. ATSB – AO-2020-017 › 7 ‹ At 0909, the pilot contacted Flightwatch9 on HF and advised: [VH-OZO] conducting a missed approach runway three zero [30] at Lockhart River, and we’ll be joining the approach on runway three zero [30], ops normal time two three three zero [2330] The middle part of this radio transmission, as recorded by Airservices Australia, was unclear, which is not uncommon for HF radio communication. Second approach at Lockhart River The aircraft continued the climb to 3,800 ft before descending to level out at 3,500 ft, heading towards the closest IAF, LHREA. At 0912:51, the AFRU recorded runway lights on, consistent with the pilot reactivating the runway lights for another 30-minute period. About 2.0 NM prior to reaching LHREA, at 0913:53, the aircraft commenced a right turn towards the IF, and initially was right of the inbound track to LHREI (Figure 5). Figure 5: Flight track of VH-OZO during second RNAV GNSS approach at Lockhart River Airport with times, feature labels, and approach parameters superimposed Source: Google Earth overlaid with OzRunways data, annotated by the ATSB At about 0914, while the aircraft was tracking towards LHREI on a south-westerly heading at 3,500 ft, an image was uploaded to social media by one of the passengers (Figure 6). The camera was oriented to the west, which was in the general direction of Lockhart River. An associated message indicated very low visibility and that the pilot was circling while waiting for a break in the weather. Another passenger sent a text message at 0914 stating that the first attempt at landing was unsuccessful, the runway was not visible and there was heavy rain. 9 Flightwatch: on-request flight information service used to provide operational information including weather, aerodromes and navigational aids. ATSB – AO-2020-017 › 8 ‹ Figure 6: Image recorded by a passenger looking over the right wing and uploaded to social media at 0914 Source: Supplied At about 0914:43, when about 2.7 NM from LHREI, the aircraft started descending from 3,500 ft. At this time, the aircraft was tracking towards the initial approach track between LHREA and LHREI (Figure 5). At 0915:50, the pilot made another inbound broadcast on the CTAF advising: ten miles [10 NM] to the south-east on descent passing three thousand eight hundred [3,800 ft] correction two thousand eight hundred [2,800 ft], straight-in approach runway three zero [30], circuit area two one [time 0921]. The recorded height was about 2,800 ft at this time. The aircraft continued descending and passed over LHREI and turned right to fly parallel to the intermediate approach track at about 2,800 ft. According to the recommended flight profile for a 3° approach (Figure 2), the aircraft should have descended from 3,500 ft at about 4.2 NM from the FAF (9.2 NM from the MAPt). At this point, the aircraft was at about 2,500 ft. The descent continued at a similar gradient to the first approach although at about 1,000 ft lower than that approach. About halfway between LHREI and LHREF, the aircraft descended below the intermediate segment minimum safe altitude of 1,800 ft and continued to descend on the same descent profile. When the aircraft passed LHREF at 0918:23, it was on descent through about 1,100 ft (below the 3° approach profile height of 2,160 ft). The aircraft was right of the final approach track and, shortly after passing LHREF, the aircraft started turning back towards the final approach track. From LHREF to LHREM, the altitude limitation was the MDA of 730 ft and, at 09:18:55, the aircraft was approaching 700 ft. The aircraft then descended below the MDA and, soon after, the aircraft’s ATSB – AO-2020-017 › 9 ‹ flight path crossed the final approach track (on a ground track about 20° left of the final approach track). Collision with terrain The aircraft’s track and descent continued until it impacted a sand dune on the coastline at about 0919:41. The pilot and 4 passengers were fatally injured, and the aircraft was destroyed. Due to the impact forces, the accident was not survivable. ATSB – AO-2020-017 › 10 ‹ Context Pilot information Qualifications and experience The pilot held a commercial pilot licence (aeroplane) with an instrument rating and multi-engine aeroplane endorsement. They had recorded a total of 3,220 hours before the accident flight. The pilot obtained the multi-engine endorsement in June 2014 (on a Cessna 310 aircraft), and had accrued 1,177 hours on multi-engine aircraft, including 399 hours on the Cessna 404 aircraft type. In June 2014, the pilot also obtained their initial (multi-engine) instrument rating, and their total instrument time was recorded as 148 hours. The pilot operated as a commercial pilot in remote locations for about 5 years. Up until March 2016, they operated single-engine aircraft. In March 2016 they received training and were found competent on the Piper PA31 aeroplane type. Between March 2016 and February 2018, the pilot conducted flights for a charter company that operated Cessna 310 and Piper PA-31 aircraft, usually under visual flight rules (VFR10) with occasional instrument flights. They were approved by the Civil Aviation Safety Authority (CASA) as chief pilot of this operator in December 2016. From October 2018, the pilot was employed by Air Connect Australia on a casual basis. Prior to joining the operator, the pilot’s recorded total flying time was 2,800 hours. The pilot completed induction then conducted a flight for type-specific training in a Cessna 421 from an independent CASA-approved flight examiner that the operator frequently used for proficiency checks. This flight was about 1.6 hours and the examiner recalled that the pilot managed the transition to the 400- series Cessna without any problems. Other than the pressurisation system in the Cessna 421, the examiner considered it was operationally equivalent to the unpressurised Cessna 404.11 Following this type-specific training, the chief pilot of Air Connect Australia supervised the pilot on 4 flight sectors in VH-OZO and conducted an operator proficiency check (OPC) over 2 further sectors on 29 October 2018. The chief pilot noted that the pilot’s planning was satisfactory, and operation of the aircraft was above standard. From November 2018 to the accident flight, the pilot was based in Cairns and conducted most of the operator’s charter flights, normally in VH-OZO. In December 2019, the chief pilot organised for the pilot to undertake some supervised flying at night with an instructor in a Piper PA-44 Seminole in order for the pilot to maintain night recency. The operator rarely conducted night flights. In the 90 days prior to the accident (11 March 2020), the pilot had conducted 59 flights (60 flight hours), all in VH-OZO. This included 4.5 hours recorded instrument flying time. In the last 30 days, the pilot had conducted 12 flights (13.5 flight hours), including 1.0 hour recorded instrument flying time. The most recent flights were on 18 February 2020. Since joining the operator in late 2018, the pilot had logged 69 RNAV GNSS approaches to various aerodromes. These included 21 RNAV GNSS approaches in the previous 6 months, 12 in the previous 90 days, and 2 in the previous 30 days (with the last on 18 February 2020). Only one of the approaches in the previous 6 months was conducted to some extent in instrument 10 VFR: a set of regulations that permit a pilot to operate an aircraft only in weather conditions generally clear enough to allow the pilot to see where the aircraft is going. 11 The operator’s operations manual stated: ‘Due to the possibility of engine damage, asymmetric training in Company Cessna 404 aircraft is to be undertaken only where strictly necessary. Abrupt or large power changes are to be avoided where possible.’ ATSB – AO-2020-017 › 11 ‹ meteorological conditions (IMC),12 and this approach resulted in a missed approach (see Prior missed approach during an RNAV GNSS approach (22 January 2020). Lockhart River experience Since the start of 2019, the pilot had flown into Lockhart River 8 times, 6 of which were logged as RNAV GNSS approaches, with the most recent being on 14 October 2019. The recorded data for previous RNAV GNSS approaches into Lockhart River were reviewed by the ATSB, with the details provided in Table 1. A review of recorded weather information indicated that none of these previous approaches at Lockhart River were conducted in IMC. For the 17 January 2019 approach, there may have been reduced visibility in the early part of the approach.13 Table 1: Pilot’s prior flights to Lockhart River 2019–2020 Proficiency checks and flight reviews The pilot conducted initial instrument flight training in 2014. During training it was noted that the pilot needed to scan faster, improve situation awareness and improve radio phraseology. On one simulator training exercise it was noted the pilot was too high on the RNAV GNSS MDA and minimum altitudes. The pilot did not pass their first attempt at attaining an instrument flight rating (in a Cessna 310) on 2 June 2014 for not maintaining altitude within +100 ft and -0 ft at the MDA, not using accepted navigation procedures, not being within half-scale deflection of glideslope, and not demonstrating sound command judgement. On the next day, 3 June 2014, the pilot passed on their second attempt. Under Civil Aviation Safety Regulation (CASR) 61.650, pilots need to have completed an instrument proficiency check (IPC) in the previous 12 months to fly a multi-engine aircraft under 12 Instrument meteorological conditions (IMC): weather conditions that require pilots to fly primarily by reference to instruments, and therefore under instrument flight rules (IFR), rather than by outside visual reference. Typically, this means flying in cloud or limited visibility. 13 The aerodrome forecast for that flight included periods of reduced visibility (3,000 m) in rain showers and cloud at 1,200 ft. Data from the aerodrome’s automatic weather station indicated the 1-minute visibility was 2,500 m at the airport when the aircraft passed the initial approach fix (IAF). However, the visibility had improved to 4,200 m by the time the aircraft reached the final approach fix (FAF) and continued to improve, to more than 10 km by the missed approach point (MAPt). There was no recorded rainfall during this period. The forecast and observed wind favoured a landing on runway 12. Date Departure location Approach type recorded ATSB comments 17 January 2019 Cairns RNAV GNSS Aircraft passed over MAPt for runway 30 at 1,500 ft and then conducted a circling approach to land on runway 12 21 March 2019 Cairns RNAV GNSS Missing flight data for the approach and landing though appeared to be heading for runway 30 IAF 23 March 2019 Cairns RNAV GNSS Flight data shows an RNAV approach to runway 30 from the FAF but missing flight data before that point 24 March 2019 Coen RNAV GNSS Flight data shows an RNAV approach to runway 30 from the FAF but missing flight data before that point 24 March 2019 Coen VFR Logged as VFR flight, so data was not reviewed 18 April 2019 Cairns VFR Logged as VFR flight, so data was not reviewed 9 October 2019 Cairns RNAV GNSS No flight data available 14 October 2019 Cairns RNAV GNSS No flight data available ATSB – AO-2020-017 › 12 ‹ the instrument flight rules (IFR). The IPC must also be done in a multi-engine aircraft of the same category. The pilot undertook 6 IPCs with 3 different independent CASA-approved flight examiners between 2016 and 2019. These are detailed in Table 2. Table 2: Pilot instrument proficiency checks 2016–2019 The pilot’s last 3 IPCs were conducted on 4 August 2018, 5 August 2018 and 7 August 2019, all with the same CASA-approved flight examiner (who also conducted the IPC in March 2016). On 4 August 2018, the pilot did not pass the IPC due to misreading the altimeter. The flight examiner recalled that they were on descent to the minima on a circling approach and, when the aircraft was at 1,000 ft above the MDA, the pilot asked whether they were visual. It then became apparent that the pilot had misread the altimeter by 1,000 ft (that is, they thought the aircraft was 1,000 ft lower than it was). The pilot successfully passed the check the following day. The pilot’s most recent IPC was conducted on 7 August 2019 and was valid until 7 August 2020. The flight examiner who conducted this check was selected by the pilot; it was not the flight examiner regularly used by the operator (and who was familiar with the Air Connect Australia operations manual and could also conduct OPCs). For each of the IPCs in 2018 and 2019, the pilot conducted a training flight with an instructor prior to the test flight, using the same Cessna 310 aircraft as in the test flights. The instructor commented that the pilot flew significantly better in 2019. Between the 2 checks in 2018 and 2019, the Cessna 310 aircraft was fitted with a GPS/navigational system and electronic flight instruments comprising an attitude display indicator (ADI) and a horizontal situation indicator (HSI). The ADI displayed aircraft attitude information, together with a secondary display of air data information (airspeed, altitude and vertical speed). The ADI and HSI each provided course and advisory vertical guidance during RNAV GNSS approaches.14 As already noted, the pilot undertook an operator proficiency check (OPC) on 29 October 2018 before commencing line operations with Air Connect Australia. This was the last OPC carried out on the pilot (see also Operator proficiency checks). Between February and June 2018, prior to joining the operator, the pilot undertook training with an airline in a multi-crew environment and high-performing (turboprop) aircraft. Although the pilot obtained high marks in theory and written tests, they did not obtain satisfactory ratings during 3 proficiency assessments in a simulator (with remedial training given after each of the first 2 assessments). A common identified problem was instrument approaches, with issues identified including inefficient instrument scan, fixation (on some parameters), speed control, workload management, insufficient situational awareness and ineffective profile management. The ATSB 14 This aircraft retained the conventional airspeed indicator, altimeter and vertical speed indicator flight instruments, which were mounted in their usual positions relative to the ADI display. Those instruments were similar to the instruments fitted to VH-OZO. Date Outcome 17 March 2016 Competent 14 May 2017 Not competent on a ground component (underpinning knowledge) with no assessment of flying capability 27 July 2017 Competent 4 August 2018 Not competent due to misread of altimeter by 1,000 ft (under-read) 5 August 2018 Competent 7 August 2019 Competent ATSB – AO-2020-017 › 13 ‹ notes that the training and checking environment at the airline was different to the pilot’s previous experience and the operational environment at Air Connect Australia. Observations of the pilot’s approach to safety The chief pilot (and managing director) of Air Connect Australia described the pilot as being a good pilot who would not have gone into an approach if they thought the weather was going to be poor, and that there was never any pressure to fly in poor weather. The pilot was trusted to make safety decisions, which would be supported by the chief pilot. This was consistent with the recollection of a previous pilot who flew with the operator, who reported that there was never any operational pressure (from the operator’s key personnel). Another pilot stated that the pilot of the accident flight had ‘good stick and rudder skills’ and that everything was done ‘by the book’. It was also reported that the pilot had not expressed any concerns about the operator, including its approach to safety. Former colleagues from when the pilot was chief pilot at a previous operator described the pilot as smart, diligent, and methodical with good knowledge of the rules and regulations. They reported that the pilot did not take shortcuts or unnecessary risks and had good hand-flying skills. With reference to instrument approaches, one pilot advised that they had many conversations with the pilot of the accident flight regarding aircraft accident reports and safety, and the pilot of the accident flight had stated that they would conduct instrument approaches using the published constant-descent profile and would not intentionally deviate below published segment minimum safe altitudes in order to get visual early in an approach. During January 2020, the pilot spent a week conducting a series of charter flights between Aurukun and Weipa, Queensland, in VH-OZO with the same group of passengers (see also Prior missed approach during an RNAV GNSS approach (22 January 2020)). Their perception was that the pilot was a good, competent pilot who was diligent, professional, and responsible and that they never felt unsafe. They also advised that they observed the pilot reviewing forecast and actual weather conditions regularly and that the pilot would delay flights due to weather conditions if necessary. Some of the passengers reported observing the pilot make weather-based decisions and did not display any indications of external pressure to fly in poor weather. One of the passengers reported that the pilot had said they would only ever make 2 attempts at landing and, after that, would return to the departure aerodrome or divert to an alternate. Recent history The pilot had recently returned from annual leave, with their last flights before leave conducted on 18 February 2020. The 3 days prior to the accident flight were reported to be uneventful. It was described that the pilot ate and exercised regularly and had been sleeping well with a standard time to sleep about 2230 and wake time about 0700–0730. The night before the accident flight, the pilot went to bed at about 2230 and woke at about 0530. There was nothing of note from the pilot’s recent history to suggest they were experiencing a level of fatigue known to affect performance. The pilot was notified about the 11 March 2020 flight a few days in advance. It was reported that the pilot had been in a good mood in the days prior to the flight and was looking forward to flying again. On the day before the flight, the pilot went to Cairns Airport and started the aircraft’s engines to re-familiarise themselves and ensure everything was ready for the next day’s flight. Medical information The pilot’s Class 1 Aviation Medical Certificate was renewed on 14 February 2020 and was valid until 14 February 2021. There were no indications of any significant medical problems in the pilot’s aviation medical records. There was no evidence to suggest the pilot had any current or ongoing medical issues at the time of the accident. ATSB – AO-2020-017 › 14 ‹ A post-mortem examination was conducted by a forensic pathologist on behalf of the Queensland Coroner. The pathologist found that there was ‘No obvious natural disease to contribute to the cause of death within limits of examination …’. Forensic toxicology screening returned negative results (that is, no alcohol or substances were detected). The sample was unsuitable for analysis for carbon monoxide. Aircraft information General information The Cessna 404 Titan is an unpressurised, low-wing, twin piston-engine aircraft with retractable landing gear. The maximum take-off weight (MTOW) is 3,810 kg, and the aircraft was certified to be flown by a single pilot. VH-OZO was manufactured by the Cessna Aircraft Company in 1980. It was reported that the aircraft was first operated in Australia before being transferred to Papua New Guinea and registered as P2-ALG. In December 2009, a CASA Certificate of Airworthiness was issued, and the aircraft was registered as VH-OZO. At that time, the aircraft’s total time in service was 28,193 hours. Seating The type certificate data sheet for the Cessna 404 stated the aircraft type had 11 total seats (2 pilot seats and 9 passenger seats). In 1980, VH-OZO was configured with a modified seating configuration with 13 seats (2 pilot seats and 11 passenger seats).15 During an audit of Air Connect Australia in June 2017, CASA identified that the Airplane Flight Manual stated a maximum of 9 passenger seats aft of the pilot seats but there was 11 on the aircraft. In its initial audit response, the operator stated that the seating change was approved many years ago and it was attempting to find supporting documentation. In a subsequent response, the operator stated that it had previously operated and would continue to operate with a maximum of 9 passengers. It noted that the extra seating would remain in the aircraft as it formed part of the aircraft’s current weight and balance data. During the investigation, the chief pilot confirmed that the operator never operated the aircraft with more than 9 passengers and normally operated with significantly less than 9 passengers. Photos taken during the accident flight indicated that no passengers were seated in the front right seat next to the pilot. Aircraft instruments and systems On arrival into Australia, the aircraft was fitted with aerial geophysical survey equipment and was operated in that configuration until the equipment was removed in March 2012. Concurrently, the aircraft were modified in accordance with an engineering order to install new types of avionics and integrate those with existing units. The post-modification avionics, including existing equipment, consisted of: • Garmin GMA 340 audio panel • dual Garmin GNS 430W GPS/Nav/Com units • dual Garmin GI-106A GPS/VOR/LOC course deviation indicators (CDIs) • Garmin GTX327 transponder • Bendix/King KR87 automatic direction finder (ADF) and Bendix/King KI-227 ADF indicator • Collins HF radio 15 A number of other Cessna 404 aircraft introduced to Australia at about the same time also had modified seating arrangements with 11 passenger seats. ATSB – AO-2020-017 › 15 ‹ • Cessna 400B Navomatic autopilot • Bendix weather radar (monochrome display). These units were still installed at the time of the accident except for the transponder, which had been replaced by an automatic dependent surveillance-broadcast (ADS-B) compliant unit in April 2017. VH-OZO was not fitted with a terrain avoidance and warning system (TAWS), nor was it required to be under legislation in place in Australia at the time of the accident. Further information is provided in Terrain avoidance and warning systems. An assigned altitude indicator was fitted to the aircraft, which was designed to be used as a reminder of the designated altitude. Altitudes could be manually set by means of individual thumb wheels and no aural or visual alerts were provided when reaching or leaving the set altitude. The aircraft did not have an altitude alerting system, nor was it required for the type of aircraft and operation.16 The 400B autopilot was one of the standard equipment options for the Cessna 404 type. It could provide pitch and roll control with heading and altitude hold (on command). A navigation function provided the autopilot with inputs from an associated CDI (the GI-106A), which in this case received data from the number-1 GNS 430W. For an RNAV GNSS approach, a pilot could ‘couple’ the autopilot for lateral navigation and manage vertical navigation by adjusting the autopilot pitch wheel to achieve the intended rate of descent. For a level segment, the pilot could select altitude hold on reaching the intended altitude. Several pilots who had flown VH-OZO advised that they routinely hand flew instrument approaches due to autopilot constraints. The aircraft was fitted with the instrumentation required for operations under the IFR. These flight instruments were conventional analogue indicators and reflected the original specifications for the aircraft. The second artificial horizon/attitude indicator and altimeter were located on the right side of the co-pilot panel (far side of the instrument panel relative to the pilot) (Figure 7). 16 An altitude alerting system provides an aural alert (tone) and/or a visual alert when an aircraft on climb/descent approaches the designated altitude and when deviating from that altitude during cruise. They are generally used to assist pilots monitor adherence to the ATC assigned level in controlled airspace, rather than mitigate the risk of controlled flight into terrain. Civil Aviation Order (CAO) 20.18 required aircraft conducting IFR operations in controlled airspace to have either an assigned altitude indicator or an altitude alerting system. For piston-engine aircraft, an altitude alerting system was only required for IFR operations above flight level 150 (which is 15,000 ft measured according to a standard atmosphere). ATSB – AO-2020-017 › 16 ‹ Figure 7: VH-OZO instrument panel Source: Supplied, annotated by the ATSB A closer view of the instrument panel is depicted in Figure 8. It had the standard 6 flight instruments directly in front of the pilot’s seat on the left. These include the attitude indicator, which depicts the aircraft’s basic roll and pitch attitude, and the primary performance instruments – altimeter, airspeed indicator and vertical speed indicator (VSI). Below those were 2 (GI-106A CDI) instruments17 that provided course deviation indication provided either by the GNS 430’s digitally- tuned VOR/localiser and glideslope receiver or GPS input to conduct an RNAV GNSS approach. One CDI instrument was coupled to the aircraft’s number-1 GNS 430W GPS unit and the other to the number-2 GPS unit. The basis of cockpit design is to have the primary instruments within a small arc of the pilot’s forward line of sight. Navigation systems such as the GPS units may be located next to the primary instruments, as was the case in VH-OZO. While conducting an RNAV GNSS approach, it is imperative that the pilot includes the GPS units in the scan. 17 Second CDI is partially hidden behind control column and clamp in Figure 8. ATSB – AO-2020-017 › 17 ‹ Figure 8: Instrument panel of VH-OZO Source: Supplied, annotated by the ATSB Altimeters VH-OZO was equipped with two 3-pointer altimeters (Figure 9), including one directly in front of the pilot. They had a 100-ft pointer (long and narrow), 1,000-ft pointer (short and wide) and 10,000-ft pointer (long and thin with a triangle at the end). The diagonal hashing indicated when below 10,000 ft and was gradually covered above that height. These types of 3-pointer altimeters are very common in general aviation aircraft, including small aeroplanes used for passenger transport activities. Research has shown that such altimeters can be associated with misreading errors, including misreading the altitude by 1,000 ft, although accidents known to be associated with such errors seem relatively rare. Accordingly, such altimeters (and some other altimeter designs) are no longer allowed to be used on air transport certificated aircraft. Further information about requirements and guidance regarding altimeters is provided in Appendix A – Research and guidance regarding design of altimeters. The aircraft was not fitted with a radio altimeter, nor was it required for the type of aircraft and operation. ATSB – AO-2020-017 › 18 ‹ Figure 9: Example of the 3-pointer type of altimeter fitted in VH-OZO This altimeter shows an altitude of 1,210 ft (10,000 ft pointer indicating 0, 1,000 ft pointer indication 1,000 ft and 100 ft pointer indicating 210 ft. Source: avioelectronica.com GNS 430W overview The Garmin GNS 430W is a panel-mounted unit that provides GPS navigation, instrument landing system or VHF omnidirectional radio range navigation, and VHF radio communication. It was approved for IFR operations, including RNAV GNSS approaches, and was used in conjunction with a CDI. Although the ‘W’ designated wide area augmentation system capabilities18 that facilitated GPS approaches with vertical guidance, Australia did not have the associated satellite-based augmentation system to enable this functionality at the time of the accident. As such, the GNS 430W was approved to provide distance and track information only for RNAV GNSS non-precision approaches. Information was displayed to the pilot on an 8.4 cm by 4.6 cm (240 by 128 pixel) high-contrast colour LCD. A pilot could select the pages and menus to display relevant information during various flight stages. Those included the default navigation page and additional pages including: • a 2-dimensional representation of terrain relative to the aircraft position • information for vertical navigation of the aircraft • a moving map display • information about the status of the GPS satellite constellation • information relevant for the navigation and communication functions of the unit. When used for an RNAV GNSS approach, the navigation page would display a graphic CDI together with the active leg of the approach and 6 user-selectable data fields.19 After passing the waypoint it was tracking to, the unit would automatically sequence to the next waypoint. When approaching a waypoint such as an initial approach fix (IAF), if a turn was required, the unit would display the recommended flight path (turn) to intercept the next track segment. The unit would also display a flashing message about 10 seconds prior to the start of the recommended turn, alerting the pilot that a turn was required and the track to intercept. 18 The wide area augmentation system (WAAS) was developed by the US Federal Aviation Administration. The system provided augmentation information to GPS receivers, which improved the position accuracy and enabled localiser performance with vertical guidance (LPV) approaches to the runway. Those approaches took advantage of the increased position accuracy and were flown to a decision altitude, similar to a Category I instrument landing system procedure. The WAAS system covered most of the US, parts of Canada and Mexico. 19 The default settings for the user-selectable fields were distance to the next waypoint, desired track, bearing to waypoint, groundspeed, ground track and estimated time en route. ATSB – AO-2020-017 › 19 ‹ To use the unit for RNAV GNSS approaches, it was a requirement that the NavData card20 was valid and the approach procedure was loaded from the database. The operator subscribed to the Jeppesen NavData service that provided monthly updates. It was reported that the pilot updated the NavData card using a laptop computer in the 24 hours prior to the flight. There were no changes in the update that would have been relevant to the accident flight. The terrain, obstacle and airport terrain database was loaded on a terrain data card. The operator did not subscribe to an update service for terrain/obstacle data. Obstacle data was updated on a 56-day cycle and updates to the terrain database were released on an ‘as-needed’ basis. There was no requirement to have current obstacle or terrain databases to use the GNS 430W for flight under the IFR and/or during an RNAV GNSS approach. A June 2018 photograph of VH-OZO’s GNS 430W receivers indicated the obstacle database installed at that time was dated October 2011.21 Fault detection and exclusion was incorporated into the GNS 430W software to detect satellite failure and exclude failed satellites from usage. In addition to their experience with VH-OZO, the pilot of the accident flight had experience using GNS 430 units during their time flying Cessna 310 and PA-31 aircraft with a previous operator, which included units with a terrain awareness function. Garmin TERRAIN function Garmin TERRAIN was a non-certified22 terrain awareness system, provided as a standard feature of 400W-series units, to increase pilot situation awareness and help reduce the risk of controlled flight into terrain (CFIT). The functions required a valid 3D GPS position and a valid terrain and obstacle database. Terrain and obstacle information was advisory only and was not equivalent to warnings provided by TAWS. The Garmin 400W Series Pilot’s Guide & Reference manual stated: CAUTION: The Terrain feature is for supplemental awareness only. The pilot/crew is responsible for all terrain and obstacle avoidance using information not provided by the 400W-series Terrain feature. When the GNS 430’s terrain page was selected, it presented a 2-dimensional colour-coded display of terrain tiles and obstacles from its database, relative to the aircraft’s current position/altitude. Red (warning) indicated terrain/obstacles above and up to 100 ft below the aircraft’s current altitude, yellow (caution) between 100 ft and 1,000 ft below the current altitude, and black more than 1,000 ft below the current altitude. The terrain page would not normally be selected when conducting an RNAV GNSS approach. Terrain advisory and alert messages were provided when flight conditions met specific parameters. The advisories/alerts comprised a visual annunciation in the lower left corner of the unit’s LCD display, accompanied by a larger pop-up advisory/alert on the current display page (except the page displaying terrain). To clear the pop-up advisory/alert, the pilot would either acknowledge the message to return to the selected page or acknowledge the advisory/alert and display the terrain page. The system did not provide auditory alerts. A pilot could use an ’inhibit mode’ to deactivate the terrain advisory/alert message system and pop-up messages would not be generated. The terrain page was still selectable and would display colour-coded terrain and obstacle information relative to the aircraft’s position. Once inhibited, the terrain annunciator field displayed a ‘TER INHIB’ annunciation and the terrain alert system remained deactivated until reselected. The GNS 400W-Series manual stated that the terrain 20 The navigation and terrain data were contained on 2 removable data cards, which slotted into the front face of each unit. 21 One of the GNS 430W units was swapped with that from another aircraft in July 2018. The last terrain/obstacle database update of that unit was not determined. 22 The series of Technical Standard Orders (TSO) C151 stipulated the minimum operational performance standards that a terrain awareness and warning system (TAWS) must meet to comply with regulatory requirements for the fitment and use of those systems. ATSB – AO-2020-017 › 20 ‹ inhibit mode could be used when the advisories/alerts were deemed unnecessary by the pilot. The manual also stated: Flying VFR into an area where unique terrain exists could cause the system to annunciate a nuisance alert. Pilots should use discretion when inhibiting the TERRAIN system and always remember to enable the system when appropriate. According to the GNS 400W-Series manual, the terrain system issued a premature descent alert (PDA) when the aircraft was significantly below the normal approach path to a runway. The manual indicated that this alert would activate depending on the aircraft’s height above terrain and distance from the runway threshold (for example, it would be triggered if the aircraft was about 400 ft above terrain when 10 NM from the runway threshold, 350 ft at 5 NM, 320 ft at 4 NM, and 280 ft at 3 NM). PDA alerts were not provided when the aircraft was within 0.5 NM of the runway or less than 125 ft above terrain within 1.0 NM of the runway. Based on this information and the recorded data for the accident flight (Recorded flight data), provided that the terrain advisory/alert function was enabled, a yellow and black ‘TERRAIN’ annunciation would be generated in the lower left corner of the LCD display, accompanied by a yellow and black ‘TOO LOW – TERRAIN’ PDA pop-up alert (Figure 10), about 15 seconds prior to the terrain collision. Figure 10: Premature descent alert on the GNS 430W display Source: Garmin GNS 400W Series Pilot’s Guide & Reference The terrain system also provided forward-looking terrain avoidance (FLTA) alerts. Provided the terrain system was enabled, a FLTA terrain alert was generated when the predicted or present aircraft altitude above terrain or obstacles was below the minimum clearance value for that phase of flight. During an approach, the clearance value was 150 ft during level flight and 100 ft when descending.23 The terrain/obstacle advisory alert comprised a yellow and black ‘TERRAIN’ annunciation in the lower left corner of the LCD display, accompanied by a yellow and black ‘TERRAIN ADVISORY’ or ‘CAUTION OBSTACLE’ pop-up message. The pop-up advisory alert would be displayed on all selectable pages (except the terrain page) and remained visible until the message was cleared/acknowledged by the pilot, or the minimum clearance value was no longer infringed. If the minimum clearance value for terrain/obstacles remained, a terrain/obstacle ahead alert would be generated. The alert consisted of a flashing yellow and black ‘TERRAIN’ annunciation in the lower left of the LCD panel display and a flashing yellow and black ‘TERRAIN AHEAD’ or ‘OBSTACLE AHEAD’ pop-up alert. The pop-up alert would be displayed on all selectable pages, except the terrain page and remained visible until the message was cleared/acknowledged by the pilot, or the minimum clearance value was no longer infringed. The GNS 400W-Series manual did not specify the warning period for FLTA alerts. However, an earlier version of the 430/430A-Series manual indicated the ‘TERRAIN ADVISORY’ or ‘OBSTACLE ADVISORY’ pop-up terrain alert would be displayed when approximately 60 seconds from potential impact and the ‘TERRAIN AHEAD’ or ‘OBSTACLE AHEAD’ flashing pop-up terrain alert when 30 seconds from potential impact. 23 FLTA alerts were automatically inhibited when the aircraft was less than 200 ft above terrain while within 0.5 NM of the runway, or less than 125 ft above terrain within 1.0 NM of the runway. ATSB – AO-2020-017 › 21 ‹ On the accident flight, the descent rate when the aircraft reached 5 NM from the runway threshold (or 3.6 NM from the MAPt) is unclear (see Recorded flight data). However, soon after, the descent rate was about 1,200 ft/min and the predicted flight path would have resulted in an FLTA alert to be generated. Therefore, if the terrain awareness/alert system was enabled, an FLTA alert should have been generated about 30 seconds (or longer) prior to the collision. Air Connect Australia did not have any operational guidance or procedures regarding the use of the terrain awareness function on the GNS 430W units. The chief pilot reported that, when they were the pilot flying VH-OZO, they would generally leave the function turned on, even though it could be annoying in some locations. However, they did not regularly fly the aircraft and had not conducted the most recent flights in the aircraft. The ATSB spoke to several pilots who were familiar with GNS 430 units with a terrain awareness function. Some advised that the terrain awareness function would often be inhibited, whereas others would use the function on one 430 unit and inhibit it on the second 430 unit. None of the pilots were aware of operators having specific procedures and guidance for using the terrain function. Pilots stated that the main reason for the terrain awareness function to be inhibited was the perception that it could issue nuisance alerts, with some of these pilots clarifying that this would only occur (or be a valid concern) when conducting visual approaches at non-licenced aerodromes. One pilot advised that they had heard of some pilots in one operator being concerned about using the terrain function if the terrain/obstacle database was not current. However, 2 experienced flight examiners advised that, in their experience, these databases were commonly not current on aircraft they encountered in their roles and that having a current database was not critical; the advantages of the terrain awareness function were more significant than any potential problem with a terrain/obstacle database not being current. There was no information available regarding what the pilot of the accident flight normally did with the terrain awareness function when flying VH-OZO. Based on the available information, the ATSB could not establish if the terrain awareness function was enabled or inhibited during the accident sequence, or to what extent the pilot had previously encountered terrain alerts when conducting operations in the aircraft. Configurations and speeds The flap settings on the Cessna 404 included ‘UP’, ‘T.O. & APPR’ (take-off/approach) and ‘LAND’ (landing). The take-off/approach setting was often referred to as ‘approach flap’ and sometimes called ‘10° flap’.24 According to the Cessna 404 Pilot’s Operating Handbook (POH), which included the Airplane Flight Manual approved by the US Federal Aviation Administration, the maximum landing gear extension speed (and operating speed) was 182 kt, the maximum speed to select approach flap was 182 kt, and the maximum speed to select landing flap was 152 kt. The POH specified a recommended minimum approach speed (or Vref25) at 50 ft of 91 kt (all engines operating, landing flaps, weight 8,100 lb or 3,6764 kg). For all aircraft weights of 7,500 lb (3,402 kg) and lower, the POH stated approach airspeeds (at 50 ft) of 88 kt. Consistent with the POH, the operator’s operations manual provided values for VAPP26 (approach speed) of 91 kt at 8,100 lb and 88 kt at 7,500 lb and lower weights. 24 With approach flap selected, the inboard flap surface extended 10° and the outboard flap surface extended 8°. 25 Vref: reference landing speed. It is normally defined as the speed required when crossing the runway threshold at 50 ft given the landing weight and configuration of the aircraft. It is usually calculated as 1.3 times the stalling speed in the landing configuration and at the prevailing aircraft weight. 26 The operations manual used the term VAPP and Vref interchangeably. Often VAPP is used to refer to Vref plus additions for wind and other factors. ATSB – AO-2020-017 › 22 ‹ The POH stated the minimum control speed (VMCA) with approach flap selected was 78 kt. In addition, the one-engine inoperative best rate-of-climb speed for the aircraft type was 102 kt (flap in the take-off/approach position and gear up) and 109 kt (flap and gear up). Aircraft maintenance The aircraft logbook statement specified that VH-OZO was to be maintained in accordance with the system of maintenance developed by the aircraft owner and approved by CASA. The key elements of the system were: • daily inspection in accordance with the Cessna 404 POH • engine and airframe inspections every 100 +/- 10 hours in accordance with the Cessna 404 progressive care program (Operations 1 and 2 plus 3 and 4 completed within 12-month period) • electrical and instrument inspections every 220 hours or 12 months in accordance with system of maintenance schedules • IFR avionics inspections every 220 hours or 12 months in accordance with system of maintenance schedules • special inspections, supplemental inspection documents, and corrosion prevention control program as required • altimeter and pitot-static system inspection and test every 24 months • maintenance release issue for a period of up to 220 hours or 12 months, whichever occurred first. Scheduled engine and airframe maintenance was carried out by the CASA-approved maintenance organisation associated with the aircraft owner. While the aircraft was based in Cairns, electrical, instrument, and radio maintenance as well as unscheduled maintenance was contracted to licensed aircraft maintenance engineers. The most recent maintenance was the scheduled 100-hour inspection based on Operations 3 and 4 of the Cessna 404 progressive care program. That was completed on 16 February 2020 at 31,066 hours total time. A maintenance release was issued with the next scheduled maintenance being the oil/filter change after 50 hours operation and compass swing in July 2020. Other key maintenance was: • 19 January 2020 at 31,050 hours: inspection of the electrical, instrument and IFR avionic systems certified as satisfactory • 29 January 2019 at 30,750 hours: inspection and test of the pitot-static system and check of altimeters certified as satisfactory. The current maintenance release was not found at the accident site. Operator records showed that the aircraft had been operated for 3.8 hours between maintenance release issue and the accident flight. The operator and aircraft owner both advised that no aircraft defects had been reported. The ATSB identified that the vacuum pumps had been in service for a relatively long period and internal wear had not been inspected at the recent 100-hour inspection. Also, there was no record of testing or replacement of the vacuum manifold in the previous 10 years. Although these aspects increased the likelihood of a vacuum system failure, there was no evidence that the vacuum- powered instruments were adversely affected. Further information regarding the maintenance and serviceability of the vacuum system (associated with the attitude indicators and directional gyro) is provided in Appendix B – Vacuum system analysis. ATSB – AO-2020-017 › 23 ‹ Terrain avoidance and warning systems General description A terrain avoidance and warning system (TAWS) provides visual and aural alerting including a look-ahead terrain function. The aircraft’s height above terrain can be based on GPS or radio altitude information. TAWS is a generic term that also includes a ground proximity warning system (GPWS) with a forward-looking terrain avoidance function. A TAWS is an important tool to help minimise the risk of controlled flight into terrain (CFIT). It provides an independent and unambiguous warning of proximity to the ground or obstacles, regardless of any navigational uncertainty or error such as mis-setting or misreading the altimeter. Multiple levels or classes of TAWS are defined and internationally recognised. Class B TAWS (TAWS B) includes a minimum of the following alerts: • reduced required terrain clearance • imminent terrain impact • premature descent • excessive rates of descent • negative climb rate or altitude loss after take-off • descent of the aeroplane to 500 ft above the terrain or nearest runway elevation (voice callout ‘Five hundred’) during a non-precision approach. Class B+ TAWS also has a terrain awareness display that shows surrounding terrain/obstacles relative to the aircraft. Class A TAWS (TAWS A) has all the requirements of Class B+ TAWS, plus 3 additional alerts. Both Class A and class B TAWS have a forward-looking terrain avoidance function. To maximise its effectiveness, an aircraft operator should have standard operating procedures for the use of a TAWS and for actions to take in response to TAWS alerts. Australian requirements Civil Aviation Order (CAO) 20.18 (Aircraft equipment — basic operational requirements), which was in force at the time of the accident, stated that for Australian aircraft: 9.1C A turbine-engined aeroplane that: (a) has a maximum take-off weight [MTOW] of more than 15 000 kg or is carrying 10 or more passengers; and (b) is engaged in RPT [regular passenger transport], or charter, operations; must not be operated under the I.F.R. unless it is fitted with (c) an approved ground proximity warning system that has a predictive terrain hazard warning function… (e) if the aeroplane has a maximum take-off weight of 5 700 kg or less, but is carrying 10 or more passengers – a TAWS-B+ system. In effect, this meant that turbine-engine aeroplanes being used to conduct passenger transport operations under the IFR were required to have a TAWS if the aeroplane was carrying 10 or more passengers or it was a larger air transport aeroplane.27 There was no requirement for a piston- engine aeroplane (such as VH-OZO) to be fitted with a TAWS. 27 Turbo-prop aeroplanes such as the SAAB 340 (maximum 37 passengers) and the Embraer EMB 120 (maximum 30 passengers) had a MTOW less than 15,000 kg. ATSB – AO-2020-017 › 24 ‹ International requirements for turbine-engine aeroplanes The Australian TAWS requirements for turbine-engine aeroplanes were consistent with the standards included in International Civil Aviation Organization (ICAO) Annex 6 (Operation of Aircraft) Part I (International Commercial Air Transport – Aeroplanes), which included a standard28 for all turbine-engine aeroplanes with a MTOW of more than 5,700 kg or authorised to carry 10 or more passengers to have a TAWS. In addition to Australia, this standard had been adopted by comparable countries, including the United States, Canada, New Zealand and Europe. In 1996, the US National Transport Safety Board (NTSB) issued a recommendation to the US Federal Aviation Administration (FAA) to require that all turbojet-powered airplanes equipped with 6 or more passenger seats have an operating GPWS installed. In 1999 it also recommended that all turbine-powered aeroplanes of the same size be fitted with a TAWS. In response, the FAA commissioned a report that examined 44 CFIT accidents that occurred between 1985 and 1994 in the US involving turbine-powered aeroplanes with 6 to 10 passenger seats. Of the 44 aeroplanes, 11 were powered by turbojets and 33 were powered by turboprops. None were fitted with a GPWS system. Computer modelling techniques used to analyse the data showed that, had GPWS been fitted, 33 accidents could have been prevented; had enhanced GPWS been fitted, 42 accidents could have been prevented. Accordingly, the FAA introduced a requirement for all turbine-powered aeroplanes with 6 or more passenger seats to be fitted with a TAWS B (in Federal Aviation Regulations 91.223 and 135.154). The requirement commenced in March 2002 for new aircraft and March 2005 for older aircraft. The FAA did not propose to introduce the same requirement for piston-engine (or reciprocating- engine) aeroplanes. In its final rule summary in 2000, the FAA stated: The General Aviation Manufacturers Association (GAMA) is against requiring TAWS on reciprocating- powered [piston-engine] airplanes because the costs would be high (e.g., “TAWS equipment would cost more than the hull value of the aircraft”), and the panel space for installing TAWS with a situational display is not available in these airplanes. The FAA did not receive any comments that would justify undertaking a new rulemaking project to mandate TAWS for reciprocating-powered airplanes. However, regarding the issue of panel space, the FAA knows of at least one manufacturer who has developed a complete TAWS unit that was designed to replace an existing panel instrument. Following the US introduction, from November 2006, ICAO Annex 6 Part I included a recommendation that turbine-engine aeroplanes with an MTOW of 5,700 kg or less and authorised to carry 6–9 passengers should be equipped with a TAWS. This recommended practice was introduced as a regulatory requirement in other countries, including New Zealand (from 2007 for air transport operations under the IFR), Canada (from 2014 for operations other than day VFR flights), and in Europe (for such aeroplanes with an individual certificate of airworthiness issued after 1 January 2019).29 International requirements for piston-engine aeroplanes Applicable from January 2007, ICAO Annex 6 Part I included a standard for TAWS B to be fitted to piston-engine aeroplanes with a MTOW greater than 5,700 kg or authorised to carry 10 or more passengers. 28 ICAO annexes specified standards and recommended practices (SARPS). 29 In its notice of proposed amendment, the European Aviation Safety Agency (EASA) noted that the absence of a TAWS had been noted as a factor in 2 accidents in Europe for these types of aircraft in the previous 10 years. It also noted that new aeroplanes were already fitted with a TAWS and that a significant number of older aeroplanes had already been retrofitted with a TAWS or equivalent system. EASA also noted that the cost of fitting a TAWS in Europe was between €20,000 to €50,000. ATSB – AO-2020-017 › 25 ‹ Subsequently, TAWS requirements were introduced in Canada (from 2014 for air transport operations other than day VFR flights), New Zealand (from 2007 for air transport operations under the IFR) and Europe (from 2012 for air transport operations) for piston-engine aeroplanes. No such requirements for piston-engine aeroplanes were introduced in the United States. Canada also introduced the same requirement for piston-engine aeroplanes with a passenger seating capacity of 6–9 conducting air transport operations other than day VFR flights from 2014. As far as could be determined, no other countries had introduced a TAWS requirement for piston- engine aeroplanes with a passenger seating capacity less than 10. In its notice of amendments about TAWS requirements in 2012, Transport Canada indicated that the cost for installing a TAWS B on small aeroplanes conducting air taxi (charter) operations in aircraft with a passenger seating capacity of less than 10 was about Can$23,000. It also noted that the expected benefits of TAWS (in terms of reduced fatalities, serious injuries and accidents due to CFITs) were significantly higher than the costs.30 Considerations of changes in Australia In March 2006, the ATSB issued safety recommendation R20060008: The Australian Transport Safety Bureau recommends that the Civil Aviation Safety Authority review the requirements for Terrain Awareness Warning Systems for Australian registered turbine-powered aircraft below 5,700 kgs, against international standards such as ICAO Annex 6 and regulations such as FAR 91.223, with the aim of reducing the potential for CFIT accidents. CASA accepted the recommendation and stated that it would examine the capital/installation costs and benefits. This work was initiated as part of CASA’s notice of proposed rule making (NPRM) 0808OS (Passenger transport services and international cargo operations – Small aeroplanes) published in February 2009. The proposed requirements included that small aeroplanes (regardless of engine type) conducting passenger transport operations carrying 6 or more passengers under the IFR to be fitted with a TAWS B. In terms of benefits and costs, the NPRM stated: The costs and benefits of mandating TAWS B equipment for IFR aeroplanes carrying 6 to 9 passengers has been assessed by CASA. Equipment and fitment costs are forecast to be approximately $23,000 per aeroplane. Options to offset these additional costs are under consideration by the Government. Benefits are expected to flow to the industry from increased public confidence with this equipment fit to small aeroplanes in which passenger operations are conducted, as the overall accident rate is expected to reduce. Accordingly, the ATSB recommendation was closed. Subsequently, CASA released a consultation draft of Civil Aviation Safety Regulation (CASR) Part 135 (Australian air transport operations—smaller aeroplanes) in 2012. This contained a requirement for a TAWS for aeroplanes conducting passenger transport operations with a maximum operational passenger seat configuration (MOPSC)31 of 6 or more. The proposed requirement’s applicability had expanded to include all flights (not just IFR flights) and was based on the passenger seat capacity rather the actual number of passengers carried on a flight. Following further consultation, the 2012 proposal was amended to a MOPSC of 10 or more. In the summary of proposed change for CASR Part 135 (published in August 2018), CASA stated: CASA had originally proposed the fitment of a minimum of TAWS-Class B for aeroplanes with a MOPSC greater than 5 which aligned with the Federal Aviation Administration of the USA (FAA) and 30 Transport Canada also noted that it had considered only introducing this requirement for turbine-engine aeroplanes (as per the US FAA) but that some stakeholders noted that some operators may discontinue using turbine-engine aeroplanes in favour of (less reliable) piston-engine aeroplanes to eliminate the cost of installing TAWS. 31 MOPSC was defined at that time as the maximum passenger seat capacity of the aircraft, excluding pilot seats, flight deck seats and cabin crew seats. ATSB – AO-2020-017 › 26 ‹ Transport Canada rules however this was changed after discussion with the Aviation Safety Advisory Panel Technical Working Group. In the 2018 explanatory statement in for the introduction of CASR Part 135, CASA outlined the options it considered (in its regulatory impact statement) regarding the implementation of TAWS. It noted that the estimated cost of installing a TAWS was about $21,000 (including about $12,000 for the system and additional costs for installation and training). One option (named option 2) was to only require a TAWS for all aeroplanes with a MOPSC of 10 or more or a MTOW greater than 5,700 kg. It was determined that this would affect 18 aeroplanes (in addition to those that already had or required a TAWS). Another option (option 3) was to require a TAWS for all aeroplanes with a MOPSC of 6–9 as well. In terms of option 3, the statement noted: The types of aircraft that are within this category include, the piston powered AeroCommander 680, Beech 95 and Cessna 421 and the turbine powered aeroplanes that include the Cessna 208, Fairchild SA 226 and Pilatus PC 12. CASA estimates that there are approximately 323 of these types of aircraft. Based on 323 aircraft within the six to nine seat range and the 18 aircraft with MTOW>5700kg of option 2 this would result in an estimated cost impact of $7.2m for 341 aircraft... [as well as $0.72m annually] The statement noted that initially CASA had proposed option 3 to industry but, following initial consultation, it did not pursue this option. Feedback associated with the initial consultation on TAWS (and other proposed regulatory changes) included that charter businesses were operating in a difficult marketplace with many not being profitable. As a result of this regulatory reform process, the Australian requirements for TAWS changed from December 2021, such that piston-engine aeroplanes with a MOPSC of 10 or more conducting air transport operations were required to have a TAWS, with the applicable date being December 2021 or December 2022 dependent on various factors (see Safety issues and actions). For VH-OZO and its seating configuration at the time of the accident, CASA advised the MOPSC was 12.32 As such, if the operator had continued operating the aircraft for passenger transport flights with that seating configuration, the aeroplane would have been required to have a TAWS by December 2022 and, from December 2024, the operator would have had to operate the aeroplane under CASR Part 121 (and conduct all flights with 2 pilots under the IFR, as well as meet additional requirements compared to Part 135). Alternatively, the aeroplane would not have been required to have a TAWS or be operated under Part 121 if some seats were removed such that the MOPSC was 9 or less.33 Aerodrome information Lockhart River Airport had one sealed runway (12/30), which was 1,500 m long and 30 m wide. It was not serviced by an air traffic control (ATC) tower and it was outside of ATC radar coverage. The airport had a common traffic advisory frequency (CTAF), which was used by pilots to advise intentions and arrange separation with other traffic. The elevation of the runway was 76 ft at the threshold for runway 30 and 48 ft at the threshold for runway 12. The runway was equipped with low-intensity runway lights, and there was no visual approach slope guidance. At the time of the accident there were 3 instrument approaches available at the airport: 32 When the aeroplane was operated by a single pilot, this included the 11 passenger seats in the cabin and the front right seat, as that could also be used by a passenger. CASA further advised that an aeroplane with 2 seats at the front and 9 seats in the cabin (such as a Cessna 404 with the seating configuration specified in its type certificate data sheet) would be considered to have a MOPSC of 9 and the front right seat would not have to be removed. 33 CASA advised that the definition of MOPSC referred to the number of passenger seats fitted to an aircraft available to be used by a passenger. An operator could not elect to limit the number of seats of an aircraft with a MOPSC of 10 or more through administrative or operational controls in order to have a MOPSC of 9 or less. Rather, seats would have to be physically removed from the aircraft. ATSB – AO-2020-017 › 27 ‹ • NDB approach to runway 30 • RNAV GNSS approach to runway 12 • RNAV GNSS instrument approach to runway 30 (Figure 2). The airport was located on a coastal plain 4.5 km west of the Lockhart River township. The Great Dividing Range was nearby with the terrain rising to over 800 ft to the south-west and west within about 8 km of the airport. Lockhart River was known to experience low cloud and poor visibility conditions. The average (mean) rainfall at Lockhart River is 2,058 mm. In the month of March, the average rainfall is 446 mm and 19.5 days have rainfall of more than 1 mm. The ATSB interviewed several pilots with experience conducting RNAV GNSS approaches, including some who had conducted multiple approaches at Lockhart River due to poor visibility conditions. The pilots had several suggestions for reducing workload for a second approach, including holding or diverting to Coen or Weipa to wait for weather to pass. Meteorological information Weather forecasts - overview The Bureau of Meteorology produced aviation forecasts, observations, warnings and advisories. As the official provider of the Aeronautical Information Service, Airservices Australia delivered the bureau’s aviation meteorological products to pilots through National Aeronautical Information Processing System (NAIPS). For the flight from Cairns to Lockhart River, the meteorological forecast information consisted of aerodrome forecasts (TAFs), graphical area forecasts (GAFs), grid point wind and temperature charts (GPWTs) and any warnings (such as SIGMETs34). These could be supplemented by aerodrome weather reports (METARs), ground-based weather radar imagery, and satellite imagery. According to the weather forecasts, the pilot would have expected mostly visual meteorological conditions (VMC)35 during the day at Cairns with some periods of rain showers and low cloud. For the arrival at Lockhart River, the forecast weather was predominantly VMC but there were overlapping periods of rain and low cloud with 30% probability of thunderstorms. Aerodrome forecasts A TAF for Lockhart River was issued at 0449 EST36 and was valid from 0600 to 1800. The expected weather conditions were: • From 0600 to 1000: wind variable at 3 kt with visibility 10 km or greater. Light rain showers and cloud scattered at 1,000 ft.37 • Between 0600 and 1000: TEMPO38 - visibility reduced to 3,000 m with rain and broken cloud at 500 ft. 34 A SIGMET provides a concise description concerning the occurrence or expected occurrence, in areas over which meteorological watch is being maintained, of en-route weather phenomena that are potentially hazardous to aircraft. 35 Visual meteorological conditions (VMC): an aviation flight category in which visual flight rules (VFR) flight is permitted – that is, conditions in which pilots have sufficient visibility to fly the aircraft while maintaining visual separation from terrain and other aircraft. 36 In aviation meteorological products, time is expressed as coordinated universal time (UTC) and the data is generally expressed in coded terms. For ease of reference, the time has been converted to EST and the data has been decoded. 37 In aerodrome forecasts and reports, the height datum for cloud is aerodrome elevation. 38 TEMPO: a significant temporary variation from the prevailing conditions previously given in the TAF, expected to last for periods of between 30 and 60 minutes. ATSB – AO-2020-017 › 28 ‹ • From 0600 to 0800: 30% probability of fog with visibility reduced to 500 ft and broken cloud at 100 ft. • From 1000 to 1800: wind from the north-east at 5 kt with visibility 10 km or greater. Light rain showers with scattered cloud at 1,000 ft. • Between 1000 and 1800: TEMPO - visibility reduced to 3,000 m with rain showers and broken cloud at 800 ft. • For the whole forecast period, 0600 to 1800: 30% probability TEMPO - winds gusting 25 to 35 kt and visibility reduced to 1,000 m due to thunderstorms and rain. This was associated with broken cloud at 500 ft and scattered cumulonimbus cloud with the base at 1,000 ft. Based on this forecast a pilot arriving at Lockhart River was required to plan for 60 minutes holding or diversion to an alternate aerodrome. The aircraft had more than sufficient fuel for that purpose (see Fuel calculations). An amended TAF for Lockhart River was issued at 0925 (5 minutes after the accident) and was valid from 0900 to 1800. The expected weather conditions were: • From 0900 to 1300: wind variable at 3 kt with visibility 10 km or greater. Light rain showers with cloud scattered at 1,000 ft and broken at 2,000 ft. • For whole forecast period, 0900 to 1800: TEMPO – winds gusting from 20 to 35 kt and visibility reduced to 1,000 m due to thunderstorms and rain. This was associated with broken cloud at 500 ft and scattered cumulonimbus cloud with the base at 1,500 ft. Graphical area forecasts A GAF was issued at 0835 and was valid from 0900 to 1500 and applicable from surface to 10,000 ft. This covered the Queensland-North region, which was divided into 6 areas for this forecast. Most of the flight including the arrival at Lockhart River was within one area that was forecast to have the following conditions: • Broken stratus 1,000 ft to 2,000 ft with broken cumulus/stratocumulus above that. Visibility reduced to 6,000 m in widespread rain. • Isolated towering cumulus from 2,000 ft, broken stratus from 800 to 2,000 ft, and broken cumulus/stratocumulus from 2,000 ft. Visibility reduced to 2,000 m in scattered rain showers. • Isolated cumulonimbus from 2,000 ft and broken status between 500 ft and 1,000 ft. Visibility reduced to 500 m in isolated thunderstorm rain showers. A GPWT forecast was issued at 0538 and was valid to 1000. Lockhart River was located near the intersection of 4 data boxes and therefore roughly equidistant from 4 forecast locations. Taking 2,000 ft as a reference height for the approaches and coastal data as more relevant, the wind was forecast to be from the north-west at 9 kt increasing to 21 kt north of Lockhart River. There were no significant weather warnings applicable to the flight. Weather conditions - overview The Bureau of Meteorology provided an overview to the ATSB of the actual weather conditions at Lockhart River on the day of the accident. It stated that a developing monsoon trough extended across Cape York Peninsula crossing the coast near Weipa and Lockhart River. A tropical low was embedded in the trough and was near Weipa at 1000, moving slowly eastward. The monsoon trough and low were causing scattered to widespread rain and isolated thunderstorms over much of Cape York Peninsula. The surface winds at Lockhart River Airport were generally light and variable. Automatic weather sensors detected rain and heavy rain reducing visibility to 800 m and scattered to broken layers of cloud as low as 1,100 ft above ground level. ATSB – AO-2020-017 › 29 ‹ Aerodrome weather reports for Lockhart River The METARs for Lockhart River were automatically generated every 30 minutes for routine reports and were issued as a special report (SPECI) at other times when one or more elements met specified criteria for degradation and improvement. For the period from 0830 to 0929 on 11 March 2020, the reports included: • 0830: nil wind, visibility39 10 km or greater with rain and scattered cloud from 3,000 ft. Temperature and dewpoint were both 25 °C. Rainfall in the previous 10 minutes was 0.4 mm. • 0900: nil wind, visibility 10 km or greater with rain and broken cloud at 2,000 ft, 3,500 ft, and 4,100 ft. Temperature and dewpoint were both 25 °C. Rainfall in the previous 10 minutes was 0.4 mm. • SPECI 0910: nil wind, visibility 10 km or greater with rain and broken cloud at 1,800 ft and 3,400 ft then overcast at 4,200 ft. Temperature and dewpoint were 26 and 25 °C respectively. Rainfall in the previous 10 minutes was 0.4 mm. • SPECI 0913: nil wind, visibility 3,800 m with rain and broken cloud at 1,800 ft and 3,400 ft, overcast at 4,200 ft. Temperature and dewpoint were 26 and 25 °C respectively. Rainfall in the previous 10 minutes was 2.2 mm. • SPECI 0929: wind westerly at 5 kt, visibility 8,000 m with heavy rain and scattered cloud at 1,200 ft, broken cloud at 1,900 ft, and broken cloud at 3,600 ft. Temperature and dewpoint were both 25 °C. Rainfall in the previous 10 minutes was 0.4 mm and rainfall since 0900 was 3.8 mm. The QNH remained at 1,008 hPa during this period. Automatic weather station The Bureau of Meteorology (BoM) provided data from the Lockhart River Airport automatic weather station (AWS) recorded at 1-minute intervals. Table 3 details 1-minute rainfall, 30-minute cloud and 10-minute visibility data for the period encompassing the aircraft’s first approach prior to the final approach fix (FAF) at 0904 to the accident at 0920. The last column in the table indicates the 1-minute visibility associated with the telephone message for the aerodrome’s automated weather information service (see following section section). More detailed information from the Lockhart River AWS for the period 0850 to 0930 is provided in Appendix C – Detailed 1-minute weather data Lockhart River 0850–0930. Table 3: Extract of 1-minute weather data from Lockhart River Airport AWS 39 Visibility reported in METARs/SPECIs was a 10-minute average. Time (EST) 1-minute precipitation (mm) Lowest cloud layer amount (oktas) Lowest cloud layer height above aerodrome elevation (ft) 10-minute visibility (m) 1-minute visibility reported by AWIS (m) 0904 0.2 2 (few) 1,800 10,000 10,000 0905 0.0 2 (few) 1,800 10,000 10,000 0906 0.0 3 (scattered) 1,800 10,000 10,000 0907 0.0 3 (scattered) 1,800 10,000 10,000 0908 0.0 3 (scattered) 1,800 10,000 10,000 0909 0.0 4 (scattered) 1,800 10.000 12,000 0910 0.2 4 (scattered) 1,800 10.000 6,000 0911 0.2 5 (broken) 1,800 10,000 1,500 0912 0.8 5 (broken) 1,800 6,000 800 0913 0.8 5 (broken) 1,800 3,800 1,000 ATSB – AO-2020-017 › 30 ‹ The first shaded area indicates when the aircraft was at the MAPt on the first approach and the second shaded area indicates the time of the accident on the second approach. The 1-minute visibility data w