AAIB Bulletin: 12/2021 G-CIIR AAIB-26991

At the hangar the pilot and his passenger met the airfield owner who was annoyed with them and repeated that a C150 should not have landed there in the conditions. The pilot was apologetic, saying he thought someone had phoned on his behalf to ask for PPR. Given the airfield owner’s concerns about a C150 operating from Troutbeck, he instructed G-CIIR’s pilot to depart solo, with his passenger departing in the M7. He added that the pilot was to use the full length of Runway 36 to ensure all the Takeoff Distance Available (TODA) was used. This would entail a backtrack of Runway 36 from the intersection of Runway 04 before starting the takeoff roll (Figure 1); the pilot agreed. The airfield owner then had to leave, but before doing so he told the M7 pilot to ensure that he took the passenger back to Gamston and that G-CIIR used the full length of the runway. Figure 1 Plate of Troutbeck Airfield - © Pooleys 6 ©Crown copyright 2021 All times are UTC AAIB Bulletin: 12/2021 G-CIIR AAIB-26991 Both pilots walked the runway to discuss the airfield owner’s instructions, but they did not go to the threshold of Runway 36. Due to the surface condition and the positive gradient from the threshold to the intersection with Runway 04, G-CIIR’s pilot said he would go down about halfway from the intersection to the threshold before starting the takeoff roll; the M7 pilot accepted this. The accident flight G-CIIR’s pilot started his aircraft first for the return to Gamston but, due to the condition of the ground where he had parked, he had difficulty taxiing out. He was assisted by the M7 pilot who leant on the tailplane to take the weight off the nosewheel and pushed the aircraft to help it move. G-CIIR was seen to taxi along Runway 22 and, as it got to the intersection with Runway 36, turn right onto Runway 36. Its engine was heard to accelerate to full power and the aircraft commenced the takeoff roll. The M7 pilot said that the engine sounded normal and G-CIIR quickly became airborne. This coincided with the M7 pilot starting to record a video of the aircraft using his mobile phone. He estimated the wind was from about 020-030° at 6 kt. Given the short time it took G-CIIR to taxi out and commence the takeoff roll, he believed the pilot did not have time to perform his engine power checks and pre-takeoff checks. Once airborne, the aircraft was seen to drift left off the side of the runway, yawing left with its pitch angle increasing. It appeared the pilot then started a left turn during which the left wing dropped and the aircraft entered a near vertical dive from about 50 ft agl, before striking the ground in an adjacent field. The aircraft came to rest on its nose in a vertical attitude, having been airborne for just over 10 seconds. As G-CIIR entered the near vertical dive, the M7 pilot and passenger realised that it was going to strike the ground and started to run towards it. Prior to reaching the aircraft they rang the emergency services before proceeding to it to help the pilot. As they approached the aircraft there was smoke coming from the engine, which soon dissipated. The M7 pilot found the pilot hanging by his lap straps unconscious and not breathing. He believed the pilot did not have his shoulder harness secured. Smelling fuel and seeing some emanating from a hole in the aircraft’s right wing tank, he was keen to extricate the pilot in case the aircraft caught fire. The pilot was subsequently removed from the aircraft with the assistance of the passenger and another witness. As they did this, the aircraft toppled over onto its back, coming to rest inverted. They put the pilot on the aircraft’s inverted wing and, with the assistance of the emergency service on the phone, gave the pilot first aid. Paramedics, local RFFS and police were in attendance about 10 to 15 minutes after the accident and attended to the pilot. An air ambulance arrived soon thereafter. However, the pilot had sustained fatal injuries. 7 ©Crown copyright 2021 All times are UTC AAIB Bulletin: 12/2021 G-CIIR AAIB-26991 Accident site The aircraft hit waterlogged soft ground about 60 m from a conifer plantation. Marks on the ground showed that the aircraft hit the ground near vertical with the left wingtip striking the ground first. This was confirmed by the damage to the nose of the aircraft and the leading edges of the wings (Figure 2). The propeller had lifted out a divot and the spinner and engine cowl had made a hole in the soil about 0.45 m deep which had filled with water and a small amount of oil leaking from the engine. Figure 2 G-CIIR accident site The engine had been pushed rearwards distorting its firewall and severely disrupting the rudder pedals, instrument panel and surrounding components. The nose section of the aircraft had been shortened by approximately 0.75 m. The fuel selector was in the on position and the battery master switch, although distorted, appeared to be in the off position. The cabin doors remained attached but had opened in the impact. The windscreen frame and instrument panel glare shield were severely distorted, and the windscreen and roof transparencies had fragmented. Some of the personal items within the aircraft had fallen out onto the ground. The left and right seat safety harnesses were loose; the pilot’s harness was reported as being found undone by the first responders when they arrived. The nose landing gear was severely displaced and had bent rearwards, and its wheel fairing had detached. The main wheels and fairings were intact but were heavily contaminated with mud (Figure 3). 8 ©Crown copyright 2021 All times are UTC AAIB Bulletin: 12/2021 G-CIIR AAIB-26991 Figure 3 Left and right mainwheel mud contamination (aircraft inverted) Of note, the right main wheel brake appeared to be binding whilst the left mainwheel was free to rotate. The underside of the fuselage was heavily mud-spattered, and the underside of the tailplane was also contaminated but to a lesser extent. Fuel had leaked from the right fuel tank leaving approximately 5 litres. The left tank appeared undamaged and contained approximately 26 litres. A total of 31 litres was extracted during the aircraft recovery. There was no fire within or around the aircraft pre- or post-impact. The pilot’s checklist was found open at the ‘AFTER START, TAXYING and POWER’ page with mud and scrape marks on it. The ‘PRE-TAKE OFF CHECKS – VITAL ACTIONS’ were on the following page. Other pages were in a clean condition. Accident pilot’s experience The accident pilot completed his PPL(A) Licence Skills Test (LST) on 30 July 2020, and his licence was issued by the CAA on 27 August 2020. Bar the flights to Troutbeck on the day of the accident, he had flown two hours since his LST. On 8 August 2020 the accident pilot flew G-CIIR from Gamston into the M7 pilot’s private grass airstrip, which is 18 nm south-west, prior to his licence being issued by the CAA3. The airstrip is orientated approximately east/west and has about 330 m of Take Off Run Available (TORA), with trees and residential houses in the undershoot and overshoot. When the accident pilot asked his supervising instructor, via a text message, if he could fly there, the instructor assumed he was going there as a passenger with the M7 pilot and Footnote 3 After a pilot has passed his LST, but before his licence is issued by the CAA, any solo flying is to be supervised by the pilot’s flying school, as if he was still a student. See the following link for more details: https://www.caa.co.uk/Flights-after-completing-a-skill-test.aspx 9 ©Crown copyright 2021 All times are UTC AAIB Bulletin: 12/2021 G-CIIR AAIB-26991 responded “Go for it”. However, the pilot planned to fly himself there in G-CIIR. Prior to departing Gamston, another instructor4 heard on the radio that this flight was preparing to takeoff and, knowing the airstrip was not suitable for a C150, was surprised to hear this. He tried to phone the pilot to stop him from going but got no reply. He therefore took it upon himself to drive to the airstrip, a distance of about 28 nm (approximately 45 minutes). The instructor arrived just before G-CIIR landed. After the pilot had landed, the instructor chastised him and made it quite clear that he had driven over because he was completely dismayed that the pilot had opted to operate a C150 into this airstrip. The instructor told him that the airstrip was not suitable for a C150, whatever the pilot’s experience, and suggested that a more experienced pilot fly the aircraft out of the airstrip. He also made his feelings known to the M7 pilot. However, the accident pilot subsequently flew G-CIIR out contrary to the instructor’s advice. A few days later the instructor spoke to the pilot and reiterated his concerns to him. He discussed the performance issues and hazards of operating his aircraft into such an airstrip. He also spoke at length about the type of flying he should be doing to gain experience with his new licence; it did not include any grass or performance limiting airfields. Comments from others involved Maule M7 pilot The M7 pilot stated that he was aware the accident pilot had flown into Netherthorpe on a number of occasions and did not remind him to ensure he obtained PPR. With regards to PPR for Troutbeck, the accident pilot messaged the M7 pilot before he departed Gamston asking whether the airfield owner would “require a call in advance?” to which the M7 pilot replied “call probably good but not essential.” The M7 pilot added that during the approach and landing at Troutbeck he transmitted on the UK’s microlight airfield frequency (129.830 MHz) and believes the accident pilot did the same. Airfield owner The airfield owner stated that he prefers requests for PPR the day before an arrival. This allows him to check that a pilot has the airfield’s plates and appropriate short airstrip experience. He also checks the aircraft type they are flying to ensure it is a “low energy aircraft”, like a microlight or a STOL capable aircraft, such as an M7 or Piper Super Cub. However, he instructs pilots to call before they takeoff so he can inform them of the current weather conditions, what the wind is and to advise the most suitable runway to use. He also advises them where to park and, in soft ground conditions, where not to park. If he has any doubt about an aircraft type or a pilot’s experience, he will not permit them to visit; this is something he has done before. Footnote 4 This instructor had flown with the accident pilot early in his training but not since. 10 ©Crown copyright 2021 All times are UTC AAIB Bulletin: 12/2021 G-CIIR AAIB-26991 The accident pilot had previously visited Troutbeck in G-CIIR, on 25 May 2020, with the M7 pilot who flew in a Super Cub. On this occasion the accident pilot was conducting a solo crosscountry flight prior to completing his PPL(A) LST. The M7 pilot requested PPR from the airfield owner, adding that he was bringing a friend, but the airfield owner was not aware of what type of aircraft he would be arriving in. Having known the M7 pilot for some time, he assumed the other pilot and the aircraft would be capable of operating into Troutbeck. However, the airfield owner was “astounded” to find out, while talking to G-CIIR’s pilot, that he was a student pilot. Had the M7 pilot mentioned this when he phoned up, the owner would “most certainly not have allowed him to land”. He stated that he would not have given him PPR on the day of the accident due to his lack of experience and the poor ground conditions at the time. On the morning of 11 October 2020, he received two calls for PPR of which one was from the pilot based at Auchinleck, near Prestwick Airport, who was known to the M7 pilot and was flying in another M7. The Auchinleck pilot asked for PPR and mentioned that the M7 pilot was planning on coming too. However, he made no mention of another aircraft accompanying him. The airfield owner did not try to contact the M7 pilot as he assumed he would be airborne. This was a concern to him because, while the airfield was pretty firm but soggy, there were some wet areas that pilots needed to be made aware of before they arrived, as he didn’t want them taxiing too far off the runway into them. The accident pilot’s instructor The accident pilot purchased G-CIIR in June 2019 when he was part way through training for his PPL(A). Thereafter he flew the rest of the syllabus in it. One of the accident pilot’s instructors, who flew and supervised most of his training flights after he had purchased G-CIIR, stated that during some of the first flights he flew with him he had a habit of not wearing his shoulder straps. From the outset the instructor asked him to put them on, which he reluctantly did. When debriefed on this, the instructor told him firmly that he would not fly with him unless he wore them. The same instructor described the accident pilot as a “good solid average pilot”, though he could be “a bit hit and miss at times”. He was also “not the most consistent student”. He described him as one of the “more aggressive, pushy students” at times. He added that during some of the first few lessons they flew together these attributes gave him cause to “reel him in” at times and he had to explain to him what was acceptable and what was not. He added that he had to be quite firm with him at times. He authorised the cross-country flight to Troutbeck on 25 May 2020 as he felt his ability was up to it, his attitude had “turned a new leaf” and he was progressing well through the course5. Additionally, he felt the conditions were suitable on the day to go into a “500 m strip”. However, he didn’t ask to see his performance calculations, though it was expected Footnote 5 Article 209 of The Air Navigation Order 2016 states that the training organisation needs to check that an aerodrome used by a student pilot is suitable and, if an unlicensed aerodrome is being used, they are required to conduct an assessment of the suitability and any hazards with operating from/to that aerodrome. 11 ©Crown copyright 2021 All times are UTC AAIB Bulletin: 12/2021 G-CIIR AAIB-26991 that students would do them when visiting a new airfield. At the end of the briefing the pilot was reminded to obtain PPR, though the instructor did not check this had been done. Aircraft information General The C150 is a two-seat, all-metal, high-wing monoplane with fixed tricycle landing gear. It is fitted with a flat-four cylinder horizontally opposed normally aspirated piston engine driving a two-bladed fixed-pitch propeller. Fuel is contained in rigid tanks within the left and right wings. An on-off fuel selector is fitted on the cockpit floor and when in the on position fuel is drawn equally from each tank. It has conventional mechanical flying controls and electrically driven flaps. The flaps are operated by a spring-loaded paddle switch which self-centres on release after the chosen flap position is achieved. A pitch trim tab is fitted on the trailing edge of the right elevator and is controlled by a hand wheel in the centre console of the instrument panel. A pneumatic stall warning device is fitted within the leading edge of the left wing. It consists of a small rectangular orifice positioned in the region where a negative pressure develops with the onset of a wing stall. The negative pressure creates a vacuum, via a tube within the wing leading edge, which causes a small reed to vibrate producing an audible note in a horn situated in the cockpit near to the pilot. The main wheels are fitted with hydraulic disc brakes operated by articulated toe pads on the rudder pedals. Four-point adjustable safety harnesses are fitted for the left and right seat occupants. G-CIIR The Airworthiness Review Certificate (ARC) was valid until 27 November 20 and its annual inspection was also due at that date. The aircraft’s flight manual stated that normal takeoffs are performed with flaps retracted. Flaps 10 is reserved for minimum ground runs or for takeoffs from soft or rough fields with no obstacles ahead. The aircraft’s flight manual stated that: ‘The stall warning horn produces a steady signal…4 to 8.5 kts…before the actual stall is reached and remains on until the airplane flight attitude is changed.’ It added that stall characteristics are conventional with flaps up and down. Slight buffeting may occur just before the stall with flaps down. Table 1 shows the calculated takeoff and landing weights for the series of flights up to the accident flight. 12 ©Crown copyright 2021 All times are UTC AAIB Bulletin: 12/2021 G-CIIR AAIB-26991 Gamston to Netherthorpe Netherthorpe to Troutbeck Troutbeck to Gamston Aircraft Basic Weight 1,212.62 1,212.62 1,212.62 Fuel at start up 156 (26 US Gall) 148 (24.67 US Gall) 82 (13.73 US Gall) Pilot 1766 176 176 Passenger 132 132 N/A Baggage 9 9 9 Takeoff Weight 1,685.62 1,677.62 1,479.62 Fuel at shutdown 148 82 N/A Landing Weight 1,677.62 1,611.62 N/A Table 1 G-CIIR takeoff and landing weight calculations (Weights in Pounds) The calculated takeoff weights for the takeoffs from Gamston and Netherthorpe were 1,685.62 lb and 1,677.62 lb respectively. The calculated landing weight at Netherthorpe was 1,677.62 lb. The aircraft’s maximum authorised weight is 1,650 lb (750 kg). The calculated takeoff weight for the aircraft on the accident flight was 1,479.62 lb. The CG on the accident flight was calculated to be 847 mm aft of datum, within the permitted range of 840 to 930 mm aft of datum. Meteorology An aftercast provided by the Met Office for the day of the accident stated that there was a ridge of high pressure over the UK, leading to generally settled conditions. The METARs for Doncaster Sheffield Airport, 11 nm north-east of Netherthorpe, indicated that there was good visibility with scattered clouds at 2,600 ft aal, and a wind from 340° at 14 kt at 1050 hrs, and from 330° at 14 kt at 1120 hrs. The conditions at Troutbeck were likely to have been good visibility with scattered cloud around 3,500 ft amsl with a light wind from the north-west. The atmospheric pressure was 1027 hPa. The M7 pilot stated that at the time GCIIR landed the wind was from 360° at about 10 kt. Video evidence of the airfield’s windsock suggested that at the time of the accident the wind varied between 330° and 350° at about 10 kt. There was no evidence of any wind gusts. Footnote 6 Pilot’s naked weight as recorded at the post-mortem examination. 13 ©Crown copyright 2021 All times are UTC AAIB Bulletin: 12/2021 G-CIIR AAIB-26991 Airfield information Retford (Gamston) Airport G-CIIR was based at Retford (Gamston) Airport. It has an asphalt runway orientated 03/21 which has a Take off Run Available (TORA) of 1,199 m. Netherthorpe Airfield Netherthorpe Airfield has two grass runways oriented 06/24 and 18/36. Runway 36 has a Landing Distance Available (LDA) of 308 m and a TORA of 361 m. The airfield is ‘Strictly PPR by phone. Inexperienced pilots are to phone for advice prior to arrival and contact a member of flying staff before departure’. Troutbeck Airfield Troutbeck Airfield has three grass runways oriented 18/36, 04/22 and 09/27 (Figure 1). Runway 36 is a 450 m grass runway. The runway has a positive gradient of about 3.3% from the threshold of Runway 36 to just after the intersection with Runway 04. Thereafter, it has a negative gradient. The elevation is approximately the same at the threshold of Runway 36 and Runway 18. Runway 36 is approximately 320 m long from the intersection of Runway 04. Runway 36 has a gradient of about +0.5% over its full length. This is based on the threshold being at 290 ft amsl and the end being around 298 ft amsl. From the threshold of Runway 04, the slope along the remainder of Runway 36 is negligible (albeit slightly negative; 2 ft over 320 m). To the left of the extended centreline of Runway 36, on slightly higher ground, is a conifer plantation (Figure 4). Figure 4 View down Runway 36 showing conifer plantation 14 ©Crown copyright 2021 All times are UTC AAIB Bulletin: 12/2021 G-CIIR AAIB-26991 About halfway down Runway 36, there is a limestone soakaway, to a drain that runs lengthwise under the runway. The windsock situated in the middle of the three runways is a 15 kt windsock. This means that it flies horizontally in a wind of 15 kt or greater. As stated in Figure 1, Troutbeck airfield is ‘Strictly PPR’ and the SafetyCom frequency (134.480 MHz) is to be used for RTF communications. Recorded information Sources of recorded information The video and audio soundtrack of G-CIIR, captured by the M7 pilot on his mobile phone, started just before the aircraft became airborne, and the aircraft remained in camera view until shortly before it struck the ground. The footage included the airfield’s windsock, which was positioned about 60 m from where the aircraft had taken off. At 1342:25 hrs, a secondary radar return was recorded for G-CIIR. The radar-derived position was near to where the aircraft struck the ground. Radar data was also available for the aircraft’s two previous flights on the day of the accident. Video and audio footage of these flights was captured by a camera that the pilot had attached to the underside of the aircraft’s right wing, which captured a near 360° view. After landing at Troutbeck, a conversation between the pilots of G-CIIR and the M7 was recorded. The camera was not operating during the accident flight. Accident flight As the video footage of the takeoff started, a light-coloured dust-like cloud could be seen near to the runway behind G-CIIR (Figure 5), which then rapidly dissipated. Very shortly afterwards, G-CIIR lifted off at which point the aircraft yawed to the left whilst also briefly banking to the left (Figure 6), before the wings then levelled. The aircraft’s track over the ground was estimated to be approximately 20° to the left of the extended centreline of the runway, which placed the aircraft on a course towards the conifer plantation. During the next few seconds, the aircraft was observed to climb gradually whilst maintaining a predominantly wings level attitude heading towards the conifer plantation, but as it reached a height of about 50 ft agl, the aircraft proceeded to roll quickly to the left whilst also starting to pitch nose-down whilst descending (Figure 7). The final image of the aircraft (Figure 8), captured less than two seconds later, showed the aircraft’s nose was 20° below the horizon and the bank angle had reached nearly 90°. A sound consistent with the aircraft striking the ground was recorded 1.6 seconds later, which coincided with the sound of the engine stopping. The estimated elapsed time from the aircraft becoming airborne to it striking the ground was just over 10 seconds. During the recording, G-CIIR’s engine could be heard operating. There was no evidence of a problem, such as a misfire, and analysis of the audio spectrum showed that the engine speed was consistent with that expected during takeoff. 15 ©Crown copyright 2021 All times are UTC AAIB Bulletin: 12/2021 G-CIIR AAIB-26991 It was not possible to determine the position of the aircraft’s flaps or its control surfaces from the video recording as the resolution was not sufficient. Figure 5 Image of G-CIIR shortly before takeoff Figure 6 Aircraft yawing and turning left after takeoff 16 ©Crown copyright 2021 All times are UTC AAIB Bulletin: 12/2021 G-CIIR AAIB-26991 Figure 7 Aircraft banks rapidly to the left whilst starting to descend Figure 8 Image of aircraft before striking the ground 17 ©Crown copyright 2021 All times are UTC AAIB Bulletin: 12/2021 G-CIIR AAIB-26991 Previous takeoff distances At Gamston asphalt Runway 03, the flaps were selected up and a rolling takeoff was made. The takeoff run distance was about 250 m and at takeoff the airspeed was estimated to have been 70 KIAS. At Netherthorpe grass Runway 36, the pilot used a short field takeoff technique (full engine power prior to releasing brakes) with flaps 10 selected. The takeoff run was about 200 m and the airspeed at takeoff was estimated to have been 63 KIAS. The video footage showed that at Troutbeck the aircraft had lifted off about 130 m from the upwind end of Runway 36. Based on the witness evidence of where the pilot started the takeoff roll, this equated to a takeoff roll of about 230 m. Aircraft examination The aircraft was recovered to the AAIB hangar for further examination. Airframe The nose section of the aircraft and engine bay was compressed and had displaced the firewall into the cockpit area. As a result, the flying control linkages to both hand yokes and rudder pedals were displaced and jammed. Both flight control yokes were broken and had detached from their shafts. Most of the instruments had remained in place although many were damaged. No meaningful information was shown on the remains of any of the instruments apart from the barometric altimeter setting. The lower panel switches and circuit breakers had been damaged during the impact. The pitch trim wheel chain drive had derailed, and its position indicator bar was bent out of shape. The throttle and mixture control linkages had also been displaced. Both wings were displaced and had a slight rearward bend and the right fuel line at the wing route had ruptured. The leading edges of both wings had been compressed and had buckled along the entire length. The fuselage skin behind and beneath the cockpit area was also buckled. The tailplane and fin were undamaged except for a minor compression of the fin tip caused by the aircraft settling onto its back after the impact. Flying controls The ailerons were correctly attached to the wings and were free to move on their hinges. The aileron control cables had come off their guide pulleys at the wing routes caused by the wing displacement. However, there was cable continuity to the flight control yokes, although these and the mechanisms behind them were jammed by the firewall and instrument panel distortion. The elevators were free to move on their hinges and the control cables were undamaged and correctly routed. There was continuity between the elevator and hand yokes, but they were in a similar jammed condition as the ailerons. The pitch trim tab was set at 8 mm down which give a nose-up trim setting. Its control cables were also correctly routed 18 ©Crown copyright 2021 All times are UTC AAIB Bulletin: 12/2021 G-CIIR AAIB-26991 and were undamaged. The hand wheel chain drive was derailed. The position indicator was bent out of shape and could not be relied upon to be a true indication of the trim tab position. The rudder was free to move on its mountings and its cables were correctly routed and connected to the rudder pedals. Despite the damage to the firewall and distortion to the rudder pedals, they were able to provide a small amount of rudder movement. The right wing flap was locked in position by its electrically driven screw jack and was 80 mm down. The left flap was loose in its tracks because the synchronising cables had come out of their pulleys as a result of the wing displacement during the impact. The inner ribs of both flaps and associated skin were distorted. Stall warner The stall warner orifice in the left leading edge contained soil residue. Distortion of the wing leading edge during the impact had caused a crack in the plastic cup at its tube attachment point. However, when a vacuum was applied directly to the tube the warning horn sounded correctly. Engine The engine had been pushed backwards into the firewall by the impact trapping and distorting the ancillary components in the process. The engine tubular mounting frame was misshapen and some of its welded joints had cracked. A large amount of soil and debris was found within the engine cowl and around the front cylinder cooling fins. The propeller was bent and misshapen and showed the engine to have been at a high power setting at the point of impact. An examination of the spark plugs indicated the engine was in a good overall state of tune. Wheels and brakes The main wheels and brakes were examined at the accident site and a further detailed examination was carried out at the AAIB. The wheel hubs, tyres and brake friction pads were covered in a layer of liquified mud. Prior to recovering the aircraft, the layer of mud was sticky and wet, but it had dried out by the time it arrived at the AAIB. The inside of the wheel fairings was also covered in mud in the same way. At the accident site the left wheel, although stiff, could be rotated by hand whereas the right wheel was seized and could not be rotated. It was eventually freed with the application of a small amount of lubricant on the disc surfaces. Both tyres were found to be correctly inflated and the treads were well defined. The brake callipers and pads were also covered in a layer of liquified mud but underneath were generally in a good, unworn condition. Despite the mud contamination the pistons had not seized in their callipers. However, mud had been smeared onto the disc friction surfaces during wheel rotation and had accumulated on the leading face of the pad friction material. 19 ©Crown copyright 2021 All times are UTC AAIB Bulletin: 12/2021 G-CIIR AAIB-26991 Crashworthiness The cabin and cockpit area had retained their basic shape and the left and right seat were correctly attached to the cockpit floor. The left and right four-point harness straps were undone and hanging loosely. The first responders had extracted the pilot, to render first aid, by undoing the harness rotary release wheel. An examination of the straps found them to be in good condition. There was no evidence of overloading on the floor mounting plates of the lap straps or the cables, shackles and brackets of the shoulder straps. The control yoke, windscreen fragments, windscreen frame and cockpit instrument panel coaming showed evidence of impact damage and distortion caused by the pilot as the aircraft hit the ground. This is known as a ‘secondary collision’, whereby an unrestrained or partially restrained occupant of an aircraft, hits interior fittings and equipment during an accident sequence. It is caused by the inertial mass of limbs, torso and head moving uncontrollably, known as flailing, in this case forward, during a sudden and rapid deceleration, and it results in contact injuries. Using measurements of the distortion, 0.45 m to 0.75 m to the front of the aircraft, and an impact speed derived from the video, the rate of deceleration of the aircraft was calculated7 to be between 3 and 4.25 g. This rate of deceleration was acting on a partially restrained body. The forces of an unrestrained upper torso and head striking the aircraft structure will be much higher as the deceleration of a head hitting a non-deforming object will result in a substantially higher g-loads. Testing and research8 has been carried out into crash survivability in aircraft and vehicle accidents and has found that: ‘Prevention of the secondary collision is essential to crash survival since relatively minor crashes can result in fatal impacts with interior vehicle structures. There are many different types of belt restraint systems available today, but they mainly involve either pelvic restraint (lap belt) or upper torso restraint (shoulder belt) or a combination of both (3-point, 4-point, and 5-point systems). Lap belt only configurations (2-point restraints) permit tremendous flail of the upper torso in crashes.’ Medical information A post-mortem examination was conducted by a consultant pathologist, which revealed that the accident pilot died as a result of head and chest injuries with the pathologist commenting that he expected them to have proved to be “rapidly fatal”. Footnote 7 The figures used to derive the force assume a constant and uniform deceleration and therefore give a conservative figure. It is probable that the initial g force may have been higher but over a very short period of time. 8 Shanahan, Dennis F. M.D., M.P.H. Human Tolerance and Crash Survivability, NATO, 2004. 20 ©Crown copyright 2021 All times are UTC AAIB Bulletin: 12/2021 G-CIIR AAIB-26991 There was no evidence found from the post-mortem examination findings, or a review of the accident pilot’s medical records, of a medical condition likely to cause sudden medical impairment or incapacity. Injuries The accident pilot sustained extensive head injuries consistent with the head striking part of the aircraft. He also had witness marks to his right groin and right hip towards his navel and on his left hip towards his navel, which were generally symmetrical. These were likely to be harness marks from the lap straps. There were no fractures to his clavicular (collar bones) which may have been expected as a result of the shoulder harness being worn. There were marks on his right anterior chest (including sharp edge marks) which may correlate to harness or aircraft parts. There were multiple anterior rib fractures, but these were probably due to chest compressions during cardiopulmonary resuscitation. There were also some posterior rib fractures which are likely to be as a result of contact with part of the aircraft. Toxicological Findings Toxicology results were positive for the presence of cocaine metabolites (benzoylecgonine) in the pilot’s blood. They were positive for the presence of cocaine and cocaine metabolites (benzoylecgonine) in the pilot’s urine. They were negative for alcohol. The consultant clinical scientist and forensic toxicologist stated that the presence of a low level of benzoylecgonine in the blood, and both cocaine and benzoylecgonine in the urine, indicated it was likely that cocaine had been used within one or two days before the accident. The fact that it was only the inactive metabolite benzoylecgonine that had been found in the pilot’s blood suggested that the behaviour of the pilot would not have been directly affected by cocaine on the day of the accident. The level of carboxyhaemoglobin9 (COHb) in the pilot’s blood was 8.5%, with levels below 10% being regarded as normal. The medical evidence was reviewed by a consultant interventional cardiologist. His report stated that, in summary, there was no medical evidence that the pilot suffered any acute medical emergency at the time of the accident. Equally there was no significant evidence that he did not. Also, there was no evidence that he was incapacitated due to the ingestion of any drug or other substance. There was also no evidence that he was feeling unwell or complaining of any particular symptoms prior to the accident flight. Footnote 9 COHb is a stable complex of carbon monoxide (CO) and haemoglobin that forms in red blood cells when carbon monoxide is inhaled. COHb should be measured if CO poisoning is suspected. 21 ©Crown copyright 2021 All times are UTC AAIB Bulletin: 12/2021 G-CIIR AAIB-26991 CAA Safety Sense Leaflets Leaflet No 7: Aeroplane Performance10 Leaflet No 7 includes the following information: ‘6 TAKE-OFF - POINTS TO NOTE d) Use of available length: make use of the full length of the runway; there is no point in turning a good length runway into a short one by doing an ‘intersection’ take-off... 8 SAFETY FACTORS a) Take-off It is strongly recommended that the appropriate Public Transport factor,…, should be applied for all flights. For take-off this factor is x1.33 and applies to all single-engined aeroplanes… Where several factors are relevant, they must be multiplied. The resulting Take-Off Distance Required to a height of 50 feet (TODR) can become surprisingly high. You should always ensure that, after applying all the relevant factors, including the safety factor, the TODR does not exceed the Take-Off Run Available (TORA). If it does, you must offload passengers, fuel or baggage.’ Figures 9 and 10 illustrate these points. Leaflet No 12: Strip Flying11 Leaflet No 12 includes the following information: ‘3 OPERATING CONSIDERATIONS a) Aeroplane performance must be appropriate for the proposed strip. You must be fully familiar with the contents of SafetySense Leaflet No. 7 (Aeroplane Performance)… 5 FLYING CONSIDERATIONS i) Always start your take-off run as close as possible to the beginning of the strip, unless there are very good reasons not to do so…’ Footnote 10 Available: http://publicapps.caa.co.uk/modalapplication. aspx?catid=1&pagetype=65&appid=11&mode=detail&id=1913 (accessed 30 June 2021). 11 Available: http://publicapps.caa.co.uk/modalapplication. aspx?catid=1&pagetype=65&appid=11&mode=detail&id=1166 (accessed 30 June 2021). 22 ©Crown copyright 2021 All times are UTC AAIB Bulletin: 12/2021 G-CIIR AAIB-26991 Figure 9 Table of factors to be multiplied to the flight manual TODR from SafetySense Leaflet 7 Figure 10 Depiction of TODR and runway length available 23 ©Crown copyright 2021 All times are UTC AAIB Bulletin: 12/2021 G-CIIR AAIB-26991 Aircraft performance The AAIB made the following performance calculations for: Gamston The TORA of 1,199 m was in excess of the Takeoff Distance Required (TODR) for a C150 in still air. Netherthorpe Runway 36 The Landing Distance Required (LDR) on Runway 36 at Netherthorpe, using the relevant factors in Figure 9, with an 8 kt headwind, without the additional safety factor (ASF), was 301 m. With the ASF (+43%), it was 430 m. This compares to an LDA of 308 m. The TODR at Netherthorpe, using the factors in Figure 9, with an 8 kt headwind, without the ASF, was 302 m. With the ASF (+33%) it was 402 m. This compares to a TORA of 361 m. Troutbeck Runway 36 The LDR on Runway 36 at Troutbeck, using the factors in Figure 9, with a 10 kt headwind, without the ASF, was 420 m. With ASF (+43%) it was 600 m. This compares to an LDA of 450 m. The TODR at Troutbeck, from the beginning of Runway 36, using the factors in Figure 9, with a 10 kt headwind, without the ASF, was 439 m. With the ASF (+33%) it was 584 m. This compares to a TORA of 450 m. The TODR from the intersection of Runway 04, using the factors in Figure 9, with a 10 kt headwind, without the ASF, was 428 m. With the ASF (+33%) it was 570 m. This compares to a TORA of 320 m. The TODR at Troutbeck from the beginning of Runway 36, on a standard atmosphere day, using the dry grass and 0.5% gradient factors in Figure 9, with a 9 kt headwind, with the ASF, was 449 m. These figures are summarised in Table 2 (with colour-coding to separate takeoff from landing data for each runway). 24 ©Crown copyright 2021 All times are UTC AAIB Bulletin: 12/2021 G-CIIR AAIB-26991 Distances in m Gamston Runway 03 Netherthorpe Runway 36 Troutbeck Runway 36 full length Troutbeck Runway 36 from intersection TORA 1,199 361 450 320 TODR (No ASF) <TORA 302 439 428 TODR (With ASF) <TORA 402 584 570 LDA N/A 308 450 N/A LDR (No ASF) N/A 301 420 N/A LDR (With ASF) N/A 430 600 N/A Table 2 Summary of takeoff and landing performance figures Test and research C150 handling characteristics – test profiles As part of the investigation, a flight trial was carried out in another C150 to assess the likely handling qualities and performance of G-CIIR, with various trim settings and flap 10 selected. The flight was conducted at a similar takeoff weight and CG to G-CIIR12 by a qualified test pilot, using standard EASA CS-2313 test techniques. The assessment specifically looked at the following: 1. Normal takeoff with elevator trim set for takeoff – to establish the control column and rudder forces during a normal takeoff. 2. Short field landing - to establish the deflection of the elevator trim tab after a short field landing with flap 40. 3. Takeoff with elevator trim tab at 8 mm of nose-up deflection – to establish the control column forces with the elevator trim tab set as found on the accident aircraft. 4. Full power stalls – to establish the stall characteristics with flap 10 and full power applied. Footnote 12 The takeoff weight of the test aircraft was 1,490 lb (estimate for G-CIIR was 1,479.62 lb) and the CG was 867 mm aft (estimate for G-CIIR was 847 mm inches aft). The CG position of the test aircraft would have resulted in a negligible reduction in longitudinal stability over that of G-CIIR. 13 CS-23 is the EASA certification specification for normal, utility, aerobatic, and commuter category aeroplanes. 25 ©Crown copyright 2021 All times are UTC AAIB Bulletin: 12/2021 G-CIIR AAIB-26991 C150 handling characteristics – test results The results of the flight tests were as follows: 1. Normal takeoff with elevator trim set for takeoff A normal takeoff with flap 10 was flown. Initially the aircraft ran straight but as the speed increased a very “modest” right pedal input (about 1 to 2 cm) was required to keep the aircraft straight. A gentle aft pressure on the control column allowed the nosewheel to be lifted off by 40 KIAS with the aircraft flying off at 50 KIAS. The takeoff trim setting equated to an attitude of about 12° nose-up, which gave 55 to 60 KIAS “hands-off” with full power applied. Maintaining 55 KIAS required moderate attention and resulted in a high nose-up attitude with degraded field of view. 2. Short field landing The aircraft was flown for a short field approach and landing with flap 40 selected, with a small amount of power applied, to give a normal approach angle. The elevator trim required equated to that found on the accident aircraft. 3. Takeoff with elevator trim tab at 8 mm of nose-up deflection A normal takeoff was conducted. The aircraft flew off at 50 KIAS and the speed was maintained at 55 KIAS. With the elevator trim set to that found on the accident aircraft a “very modest push force” of 4 daN (4 kgf) was required to hold the speed. 4. Full power stalls The aircraft’s stalling characteristics were assessed at full power, with flap 10 and the elevator trim selected to that found on the accident aircraft. As the aircraft slowed it adopted a high nose-up attitude with degraded field of view. With the aircraft kept in balance, by applying a modest right rudder input, the aircraft slowed below 40 KIAS and the stall warner sounding with the stall occurring at about 30 KIAS. The stall was generally defined by a “g break” or nose-down pitch change. With no rudder applied, the aircraft yawed left and then rolled left. With no rudder this eventually led to the aircraft’s nose dropping in the turn before a full stall was achieved. However, with a modest right rudder input the stall would be achieved with a left wing drop. Overall, the full power stall characteristics were relatively benign, but the high noseup attitude would make it difficult for an inexperienced pilot to ascertain the aircraft’s attitude, and the yaw/roll might go un-noticed. 26 ©Crown copyright 2021 All times are UTC AAIB Bulletin: 12/2021 G-CIIR AAIB-26991 Analysis The aircraft Examination of the aircraft found no evidence of a structural failure that could have led to this accident. There was also no evidence to suggest any malfunction of the flying controls, and physical and audio evidence showed the engine was producing power until the impact. The light grey coloured dust-like cloud observed a few metres behind the aircraft before it got airborne was not considered to have come from the aircraft but had most likely been displaced limestone dust from the runway soakaway as the aircraft travelled over it. The stall warner was damaged during the impact. However, despite this, correct operation could be demonstrated under test and therefore there was no reason to doubt that it was able to warn the pilot of the onset of stall during the accident flight. The first flight to Troutbeck The accident pilot first visited Troutbeck on 25 May 2020 while still a student pilot. This was authorised by his supervising instructor who assumed he had obtained PPR, which he had not. Had he attempted to obtain PPR, the airfield owner would not have granted it, given his lack of experience and a licence. Flight planning The accident pilot was recently qualified with only two hours of flying since passing his LST. As discussed with his instructor, the plan to go to Troutbeck was beyond his experience, but having had an uneventful previous visit it may have given him the confidence to return, albeit in different conditions. The accident pilot did not request PPR for Netherthorpe or Troutbeck despite both airfields requiring it. When the accident pilot messaged the M7 pilot about calling Troutbeck before departing, he was told: “call probably good but not essential”. However, the airfield’s plates clearly state ‘Strictly PPR’. Had they prepared more thoroughly they would have known to request permission in advance. Had the accident pilot tried to obtain PPR it would have been refused and the accident could have been avoided. Similarly, the M7 pilot stated he used the microlight frequency 129.825 MHz for the approach and believed the accident pilot did the same. Assuming that the accident pilot was not on the SafetyCom frequency, as stated on the airfield’s plate, he would not have been able to receive the airfield owner’s transmissions. Had he heard them, he would have been refused permission to land and the accident would not have happened. It was calculated that the LDR for the flights into Netherthorpe and Troutbeck, with the ASF applied, were in excess of the LDA. It was calculated that the TODR for the flight out of Netherthorpe, with the ASF added, was greater than the TORA. It was also calculated that the TODRs for the accident flight, from the start of Runway 36 and from the intersection with Runway 04, with the ASF added, were in excess of the TORA. 27 ©Crown copyright 2021 All times are UTC AAIB Bulletin: 12/2021 G-CIIR AAIB-26991 It was also calculated that the aircraft took off from Gamston and Netherthorpe and landed at Netherthorpe and Troutbeck above the aircraft’s maximum authorised weight. A limitation is imposed on the maximum authorised weight at which any aircraft is permitted to operate. This limitation depends on the strength of the structural components of the aircraft and the operational requirements it is designed to meet. If these limitations are exceeded, the safety of the aircraft may be jeopardized and its operational efficiency impaired. All these findings suggest that the accident pilot had either forgotten to calculate the performance and weight and balance figures, or considered he could operate into Troutbeck again without doing the necessary planning, perhaps because he had visited before without event, albeit in better conditions and without a passenger. The accident flight The M7 pilot stated that he believed the accident pilot did not have time to perform his engine power checks and pre-take off checks in the time it took him to taxi out to the runway and takeoff. While it is not known if he used the checklist, given it was found at the ‘AFTER START TAXYING and POWER’ page with mud and scrape marks, and the ‘PRE-TAKE OFF CHECKS – VITAL ACTIONS’ were on the following page, it is probable that they were not completed. This may have been because the pilot did not want to get his aircraft stuck in the mud, as had happened after he initially tried to start taxiing. This may also be the reason why he started the takeoff run from the intersection rather than backtracking to the beginning of the runway, as instructed to do by the airfield owner, or to a point halfway between the intersection and runway threshold, as he had told the M7 pilot he would do. In either case, not using the full length of the runway for a performance-limited takeoff was contrary to the guidance in Safety Sense Leaflets 7 and 12. The M7 pilot did not believe the accident pilot’s shoulder harness was secure when he released his harness prior to removing him from the aircraft. Given that the pilot had a previous tendency to not wear his shoulder harness, he taxied out and took off hastily, and his head and chest injuries indicated probable contact with parts of the aircraft, it was concluded that the shoulder harnesses were probably not secured prior to take off. The video evidence indicated that after taking off the aircraft had some left yaw with a brief left roll component. The condition of the runway was described as sludgy and the aircraft was found with lots of mud on its underside. Additionally, the left mainwheel was free to rotate whilst the right mainwheel brake appeared to be binding. This was probably a result of the mud that was discovered on its brakes friction surfaces. With this binding brake, the right wheel would have had higher rolling resistance compared to the left, leading to a tendency for the aircraft to drift right during the takeoff. This would have required the pilot to apply left rudder on the takeoff roll to maintain the aircraft’s track along the runway centre line. If the pilot maintained left rudder after the aircraft became airborne, it would have caused the left yaw and initial left roll as observed in the video. With the aircraft heading towards the conifer plantation, the pilot would have found himself in an uncomfortable situation, and one he was unlikely to have experienced before. The increase in the aircraft’s pitch attitude was consistent with him attempting to climb above 28 ©Crown copyright 2021 All times are UTC AAIB Bulletin: 12/2021 G-CIIR AAIB-26991 the plantation, although it might also have been related to the elevator trim being set for landing, not takeoff (see Flight characteristics). It is likely that the high nose attitude caused the airspeed to decrease triggering the stall warner and leading to the left wing dropping as it stalled, with the aircraft then entering the near vertical dive. With any yaw applied the tendency for the aircraft to depart controlled flight was increased. Any inability to recognise the yaw to the left and to react appropriately to the stall warner (which probably sounded) is likely to be linked to the pilot’s lack of experience. Having departed controlled flight and entered the dive at about 50 ft agl, there was insufficient height available in which to execute a recovery. Flight characteristics The flight trial found that the pilot probably took off with the elevator trimmer at the same position it was after he had landed. With it not reset to the takeoff position, the aircraft would have required a push of 4 DaN on the control column to hold the takeoff attitude. While this is a moderate force and controllable, had the pilot become distracted and relaxed his hold on the control column, or suffered some form of incapacitation, the aircraft would have pitched up. This would have caused the aircraft’s speed to decrease, which, if not corrected in a timely manner, would lead to the aircraft stalling and departing controlled flight. Any yaw applied at or close to the stalling speed of the aircraft – as appeared likely in this accident – would hasten any tendency for the aircraft to depart controlled flight. The fact that the trimmer was probably not set for takeoff also suggests that the pre-takeoff checks were not completed. No single handling or performance characteristic of the aircraft was identified that would be difficult to control. However, it was still possible for the aircraft to adopt an uncomfortable and unusual attitude that, if uncorrected, would lead to the stall and associated wing drop. Conduct of the flights The flights after the pilot passed his LST and which led up to the accident flight were characterised by incomplete preparation and an apparent disregard of advice from those notably more experienced than him. It is possible that his previous visit to Troutbeck, authorised by one of his instructors, may have given him the confidence to return there. However, it appears that the chastisement and subsequent discussion with one of his instructors at the M7 pilot’s airstrip, about what type of flying was appropriate for a newly qualified pilot, was not heeded. During the takeoff from Troutbeck – an airfield on the limits of the aircraft’s performance capabilities – the pilot rushed; he did not use the full length of the runway; it is likely he used a nose-up elevator trim setting appropriate to landing having not completed his pre-takeoff checks; and it is likely he did not fasten his shoulder harness. The toxicologist stated that the pilot’s behaviour would not have been directly affected on the day of the accident by the aftereffects of his previous cocaine use. 29 ©Crown copyright 2021 All times are UTC AAIB Bulletin: 12/2021 G-CIIR AAIB-26991 The consultant interventional cardiologist stated that there was no medical evidence that the pilot suffered any acute medical emergency that may have caused some form of incapacitation. Equally there was no significant evidence that he did not. Immediately after takeoff, the aircraft yawed and rolled to the left but the wings were then levelled. This would have required control input from the pilot, suggesting that he was not incapacitated at that point. Nevertheless, the possibility that the pilot became incapacitated in the final seconds of the flight could not be excluded. It was considered likely that his conduct during the flights leading up to and including the accident are explained by an apparent willingness to trust his own judgement over the advice of others. Survivability The aircraft descended vertically into waterlogged but dense soil. The engine was at a high power setting and the rotating propeller cut itself into the soil lifting out a large divot in the process. At the same time, the engine frame and nose section became compressed until both wing edges contacted the ground, as shown by the marks in the soil. The aircraft appears have been brought to a stop in a distance estimated to be between 0.45 m to 0.75 m, based on the impact hole and shortening of the nose section. Using an impact speed derived from the video evidence, the aircraft and pilot sustained an impact deceleration between 3 g and 4.25 g. These forces are not particularly high and should have been survivable. The pilot received fatal injuries to his head and chest and there was no evidence of a medical condition likely to cause sudden medical impairment or incapacity. Given that some of his injuries were probably sustained by contacting the aircraft and it is likely he was not wearing his shoulder harness, these injuries may have been less severe and possibly survivable had the shoulder harness been worn. Conclusion The aircraft had a valid ARC and was in a good overall condition. There was no evidence of any system malfunction or structural failure that could have been causal or contributed to this accident. All the damage to the aircraft was consistent with a frontal impact with waterlogged but dense soil. The accident was caused when a high nose attitude immediately after takeoff caused the airspeed to reduce to such an extent that the aircraft stalled with a wing-drop to the left. The high nose attitude was made more likely by the fact that the elevator trim remained set for landing, probably because the pilot did not carry out his pre-takeoff checks as he rushed to depart while not becoming stuck in the muddy surface. The wing-drop was consistent with residual left yaw at the stall, a condition considered likely because of the left roll and yaw observed immediately after takeoff. The left yaw was probably a result of the pilot not reducing the left rudder input that would have been required during the ground roll to overcome the effect of the right brake binding while rolling over the muddy runway surface. 30 ©Crown copyright 2021 All times are UTC AAIB Bulletin: 12/2021 G-CIIR AAIB-26991 Pilot incapacitation in the final seconds of the flight could not be ruled out but was considered unlikely. Opportunities were missed to prevent the accident because the pilot did not heed the advice not to operate into grass, performance-limiting airfields, did not obtain PPR and was probably not on the correct radio frequency on arrival. It is likely that the pilot did not fasten his shoulder harness, against the strong advice of his instructor, and this action may have meant the accident became unsurvivable. Flying for any pilot is a continual learning process whether they are newly qualified or very experienced. However, newly qualified pilots should be very careful to make sure they fly within the limits of their experience. This accident highlights the fact that thorough preparation is essential for every flight, and accidents can happen if short cuts are taken or good advice is not heeded. Published: 18 November 2021.