Accident to the Piper PA-31 ”Navajo” registered F-HGPS

light, in the middle of the day. The temperature was around 16° at 5,000 ft. 2.3 Information about IMAO IMAO acquires aerial data for customers in France and abroad. At the time of the accident, the company was operating a fleet of eleven aircraft, including three PA-23s and four PA-31s, based in France or abroad. It employed five pilots. The company’s operations manual, written before it acquired the PA-31 F-HGPS, states that during flight preparation, the pilot-in-command must calculate the fuel required for the mission(8). This fuel calculation must include taxi fuel, planned trip fuel and fuel reserves. The fuel reserves shall include at least the contingency fuel, the final reserve fuel and the additional fuel in accordance with current regulations. (5) The clock is normally set to UTC time, 14:10 local time. (6) 10:11 local time. (7) As long as it is sufficiently tight, the spiral spring keeps the clock running. (8) ) IMAO operations manual, section A.8.1.15.4 Fuel calculation. 6/12 BEA2018-0610.en/June 2020 The BEA investigations are conducted with the sole objective of improving aviation safety and are not intended to apportion blame or liabilities. Section A.8.1.15.1 Definition of the operations manual defines the contingency fuel as the amount of fuel required to cover the differences between the actual flight conditions and those taken into account during flight preparation (wind, ISA, planned or foreseeable holding). It is the higher of: ˆ 5% minimum of the planned trip fuel; ˆ five minutes at holding speed at 1,500 ft above the destination aerodrome in standard conditions. The operations manual states that the final reserve fuel is the amount of fuel required to fly for 30 minutes. This is taken from the current European regulations: Part SPO – IR, paragraph SPO.OP.130 Fuel and oil supply – aeroplanes: “The pilot-in-command shall only commence a flight if the aeroplane carries sufficient fuel and oil for the following: (1) For VFR flights: (i) by day, to fly to the aerodrome of intended landing and thereafter to fly for at least 30 minutes at normal cruising altitude;” The amount of extra fuel is decided by the pilot-in-command to take account of: ˆ economic considerations (cheaper fuel at certain airports); ˆ a double trip if it is not possible to refuel during a stopover; ˆ additional margins, at his discretion, to facilitate flight management. If necessary, the pilot can add the additional fuel and the alternate fuel to this. The operations manual also specifies how the fuel should be managed during the flight(9). During the flight, the pilot must regularly check the fuel gauges in order to detect any anomalies (particularly leaks). He must know the aircraft’s average hourly consumption in the current flight configuration in order to check the amount of fuel remaining. This must be converted into flight time to check the remaining endurance. The pilot is thus able to assess the amount that will be left onboard when the aircraft reaches its destination, which must be as much as or more than the planned final reserve. The operations manual is based on current regulations. These regulations indicate in SPO.OP.190 In-flight fuel management that: “(a) The operator of a complex motor-powered aircraft shall ensure that in-flight fuel checks and fuel management are performed. (b) The pilot-in-command shall check at regular intervals that the amount of usable fuel remaining in flight is not less than the fuel required to proceed, with the planned reserve fuel remaining as required by SPO.OP.130 (…), to a weather-permissible aerodrome or operating site.” (9) IMAO operations manual, section A.8.3.7.1. Comparison of planned and actual. 7/12 BEA2018-0610.en/June 2020 The BEA investigations are conducted with the sole objective of improving aviation safety and are not intended to apportion blame or liabilities. 2.4 Pilot experience and information The pilot, aged 58 years, is the CEO of the company that owns the aircraft. He has held a CPL(A) commercial pilot licence since 23 May 2006, flew infrequently and replaced pilots according to the mission. He had about 1,250 total flight hours, including 758 hours on multi-engine aircraft. In the last two years, the pilot had flown the majority of his flights in a PA-23. His last flight in a PA-31 was on 3 November 2016 for 1 hour and 30 minutes, i.e. about 22 months before the accident flight. In the last 12 months, he had flown about 80 hours, of which 72 were in PA-23s. The duration of these flights in PA-23s ranged from 1 hour 10 minutes to 7 hours 10 minutes. At the end of the flight lasting 7 hours 10 minutes, on 24 June 2018, the pilot added 673 litres of additional fuel. Only about 30 litres remained in the tanks at the time of landing(10). The average endurance of the PA-23s used by the company is 6 hours 30 minutes. Regarding in-flight fuel management, the pilot indicated that he checks that the tanks are full before the flight. He then monitors the consumption per tank, making consumption calculations on a sheet of paper during the flight. To perform this monitoring, he uses the time indicated by his watch and cross-checks it with a digital tablet. He specified that he is not in the habit of using the aircraft’s clock. He indicated that he always finishes the mission with enough fuel for the return flight, including the regulatory reserves. He indicated he was sure he had done the fuel consumption monitoring calculations for the accident flight(11). 2.5 Operator information The operator, aged 26 years, did not hold an aviation licence. She was an employee of IMAO and was responsible during the flight for checking that the photos were taken correctly on the different axes. She did not take part in the flight management. She indicated that she and the pilot had agreed before the flight to stop the mission once the nine photo storage hard drives were “full”. During the flight, the operator asked the pilot for the remaining flight time. He said that the aircraft’s endurance was 5 hours 30 minutes. The operator specified that, on other flights in the PA-31, the pilots had said the endurance was 4 hours 30 minutes. Since she had no aviation knowledge, this did not strike her as odd. The operator added that this was the first time the return to the airport had taken place once the hard drives were full. She indicated that the right engine stopped first, when the aircraft was near the airport. The pilot seemed surprised. However, she specified that the pilot gave the impression that he could land on the runway without any problem. The pilot then announced to the controller that the aircraft had run out of fuel. The operator indicated that she had sent a message with her phone to warn her colleagues. When the left engine stopped, the pilot asked her to check her seat belt. (10) Source: the company’s daily flights report, calculation of the quantity of fuel remaining carried out with the flight manual of F-HKHZ, the PA-23 used, belonging to IMAO. (11) No documents relating to flight preparation or fuel management were found at the accident site or in the company’s archives. 8/12 BEA2018-0610.en/June 2020 The BEA investigations are conducted with the sole objective of improving aviation safety and are not intended to apportion blame or liabilities. The operator explained that the pilot did not lose control of the aircraft. She was seated behind the camera in accordance with the instructions in the operations manual. She was not aware of an instruction regarding the use of another seat during take-off, landing or in an emergency. The instruction she had been given was to sit in the seat at the rear and fasten her seat belt(12). 2.6 Witness statement A witness on the ground, who lived approximately 500 m from the accident site, heard a very faint engine noise as if the engine were idling. He saw the aircraft fly over a hamlet at low height in a nose-down attitude. The aircraft disappeared from his field of vision and then he heard the noise of the accident. He rushed to the scene and called the emergency services at 15:27. As he approached the aircraft, he saw the pilot first and called the emergency services again. He then heard the operator who was behind. When he entered at the rear of the aircraft, having opened the door, he saw that the operator’s seat was folded forward, trapped between the camera and the lift table. He cut the seat belt and released the trolley. As he was unable to completely remove the camera, he held it until the emergency services arrived, to take the weight off the operator. 2.7 PA-31 aircraft Information The Piper PA-31 Navajo is a five- to seven-seat aircraft with two 310 hp Lycoming engines. Before its acquisition by IMAO in 2015, F-HGPS was registered OY-BHF. It was equipped with a camera for aerial photography missions. It had two front seats and two rear seats, one behind the pilot’s seat, the other at the rear of the aircraft(13). On the accident flight, the aircraft remained within the weight and balance limits established by the manufacturer. Fuel consumption The PA-31 Navajo has four wing tanks(14) with a total capacity of 192 US gallons, of which 186 are usable. Its mean endurance is about 4 hours 30 minutes, according to the company’s chief pilot. This corresponds to the mean endurance of the PA-31’s flights. Over the last twelve months, the mean endurance calculated from the PA-31’s logbook was 4 hours 27 minutes. It was noted that on photography missions, because lower engine speeds are used, the PA-31’s endurance can increase significantly, sometimes above five hours. Each engine is supplied with fuel by the inner “IN” tank or the outer “OUT” tank of the associated wing. A selector for each engine is used to choose between these two tanks. A tank crossfeed selector can be used to supply fuel to the engine on the opposite side from the tanks. This is used where necessary to balance the aircraft during flight by supplying both engines from the left and right tanks simultaneously. (12) See Section 2.7 PA-31 aircraft information, Survival aspects related to the Supplemental Type Certificate. (13) See Figure 3: diagram of the interior of F-HGPS. (14) Each wing has two tanks, one “outer” tank (at the wing tip) and one “inner” tank (near the airframe). 9/12 BEA2018-0610.en/June 2020 The BEA investigations are conducted with the sole objective of improving aviation safety and are not intended to apportion blame or liabilities. During contact with the tower controller at start-up, the pilot announced an endurance of five hours of flight. Spectral analysis of the exchanges between the pilot and the controllers did not detect any engine malfunctions from take-off at 10:09:20 until the last contact at 15:23:13, i.e. for 5 hours, 13 minutes and 53 seconds. As the last exchange, at 15:25:46, with the tower controller at Limoges-Bellegarde airport was too brief, it was not possible to determine whether the engines were still in operation. For the flight on the day, the consumption(15) was estimated by calculation to be 183 US GAL out of the 186 usable gallons, not including start-up and taxiing. Spectral analysis of the radio communications between the pilot and air traffic controllers during the flight indicates that the engine speed was 2200 rpm while cruising at an altitude between 6,500 and 7,000 ft. Supplemental Type Certificate (STC) A Supplemental Type Certificate (STC) is a document issued by the U.S. Federal Aviation Administration (FAA) confirming authorization to modify an aircraft or aircraft equipment. By extension, the European authorities use similar terminology. An STC describes the authorized modifications and the consequences of these modifications for the performance or behaviour of the aircraft compared to its original certification. These modifications may be the subject of additional instructions, and are then added to the flight manual as a supplement. Passenger/ operator positioning and evacuation instructions may be changed if they are affected by technical modifications. The STC also states exactly which versions of the basic aircraft model are concerned. It is issued by name to the company or design office that submitted the technical file and it bears a number. It is the property of whoever holds the technical file and it is necessary to obtain their agreement before making any modifications that affect the STC. An STC may be sold on or transferred, but the transfer of ownership must be approved by the supervisory authority. F-HGPS was modified for aerial photography by an approved workshop in 2010, before it was acquired by the company. The instructions associated with this modification were approved by the FAA in the form of an STC included in a flight manual supplement entitled “Flight Manual Supplement, Modification 2022914, Aerial Survey Equipment”. This supplement was approved by the European Aviation Safety Authority (EASA) in 2010. Since this modification, there has been a passenger seat behind the pilot and another seat at the rear facing the camera(16). Camera equipment installed onboard The camera installed onboard is a unique prototype designed by IMAO, which developed it specially for photometric photography. The camera is a floor camera, installed on a gyro-stabilized mount. The camera weighs about 85 kg and the mount 30 kg. The camera is connected to a rack comprising an image acquisition system that includes the nine storage hard disks, a computer and its screen. This modification to the aircraft was approved by the DGAC. (15) Calculation based on information from the flight manual, the flight conditions on the day and previous flights of F-HGPS. (16) See Figure 3: diagram of the interior of F-HGPS. 10/12 BEA2018-0610.en/June 2020 The BEA investigations are conducted with the sole objective of improving aviation safety and are not intended to apportion blame or liabilities. Source: IMAO Figure 5: installation of the camera equipment onboard F-HGPS Survival aspects related to the Supplemental Type Certificate In paragraph “A.8.3.12. Use of the vacant crew seat”, the operations manual states that the operator must be seated next to the systems in the rear seat. It states that during ferry flights or if the pilot-in-command becomes incapacitated, the operator may be required to sit in the right front seat. However, with the modification made in 2010 and the associated STC, instructions were added to the flight manual specifying, among other things, that during take-off, landing and in emergencies, the operator must be in the “copilot” seat to the right of the pilot, or in the seat behind the pilot’s seat. The instructions specify that a label(17) must be positioned in full view of the operator, at or near the operator’s position when taking photographs. In the flight manual supplement, this instruction has also been added to the take-off and landing checklists. Prior to 2015, two other PA-31s that had already undergone similar modifications before they were acquired by IMAO, were also in operation. Since these modifications do not have the same STC references, there are no such instructions in the flight manual for these PA-31s. When F-HGPS was acquired in 2015, the company operated the aircraft in the same way as the other two PA-31s. It had not realised this instruction existed, and therefore had not implemented it when carrying out these flights. Nor had it affixed the labels in full view of the operator onboard F-HGPS. The operator always sat in the rear seat for the entire flight in accordance with the company’s operations manual. (17) Text taken from the flight manual supplement to be displayed in full view of the operator: “OPERATOR HAS TO BE SEATED ON L/H OPERATOR SEAT (BEHIND PILOT) OR COPILOT SEAT DURING TAKE OFF, LANDING AND IN EMERGENCY”. 11/12 BEA2018-0610.en/June 2020 The BEA investigations are conducted with the sole objective of improving aviation safety and are not intended to apportion blame or liabilities. 3 - LESSONS AND CONCLUSION On the flight towards Limoges-Bellegarde airport, the aircraft found itself short of fuel. Fuel exhaustion occurred after about 5 hours and 15 minutes of flight. During the forced landing, the aircraft collided with the trees and then with the ground. The pilot and the operator, sitting in the rear, were seriously injured. When the fuel exhaustion occurred, the pilot performed the emergency actions and turned right. The tank crossfeed was found in the “ON” position. The pilot could have set it thus either to prevent fuel exhaustion or as part of the emergency actions performed when the fuel exhaustion occurred. The airport’s altitude is 1,300 ft. The altitude of the aircraft at the time of the fuel exhaustion was 1,460 ft, which meant that it could not reach the airport safely. The decision to turn right could be explained by the pilot’s attempt to reach flat fields approximately 700 m east of the accident site. The following could have contributed to the fuel exhaustion: ˆ The endurance indicated at start-up being exceeded, which may be explained by the fact that the pilot was used to flying the PA-23, which has a greater endurance. ˆ The priority of taking as many aerial photographs as possible to use up the full capacity of the storage hard drives before returning to the airport, stated during flight preparation with the operator. ˆ Although the pilot said that he did not use the clock, which was stopped at 12:10, one hour before the accident, it may have given him a false indication and reinforced his assessment of the remaining endurance. The following could have contributed to the operator’s serious injuries: ˆ Differing instructions for the operator’s seating position in the operations manual and in the F-HGPS manual, with the F-HGPS manual recommending the use of the seats to the right of or behind the pilot rather than near the equipment installed on the aircraft. ˆ The fact that the lift table was carried on a mission flight and was not secured. Measures taken by the company since the accident Following the accident, the company has implemented the following measures: ˆ Mandatory briefing before and after each flight with the chief pilot, covering fuel consumption. ˆ Introduction of a bimonthly written theory examination for all pilots on knowledge of the company’s aircraft, including in particular the performance, endurance and fuel consumption of the aircraft. ˆ Introduction of a monthly meeting with pilots and operators including the presentation and analysis by a pilot/operator pair of an incident or accident involving an aircraft doing aerial work. The event presented could be one that happened outside the company. 12/12 BEA2018-0610.en/June 2020 The BEA investigations are conducted with the sole objective of improving aviation safety and are not intended to apportion blame or liabilities. ˆ Pilot testing of a smart clock with audible and visual reminders to help monitor consumption. The test results could lead to the installation of these clocks throughout the fleet. ˆ Amendment of the operations manual to incorporate the instructions added to the F-HGPS flight manual. These instructions on where operators should sit will be applied during take-off and landing and in emergencies for all missions. ˆ Carrying of the lift table, secured in the aeroplane’s rear hold, only on ferry flights.