Steve Ayres

Accident Analysis

With Steve Ayres

SAFETY

Normally, everything’s fine!

We are always checking, aren’t we? And when something eludes our scan, our experience always provides the wherewithal to get things back on track, doesn’t it? As Steve Ayres reports, these accidents suggest that is not always the case!

It is with thanks to our French colleagues at the Bureau d’Enquêtes et d’Analyses for publishing this month’s accident reports. Both occurred recently during the take-off phase and both led to loss of the aircraft and nearly to loss of life. Miraculously, everyone survived. 

So how was it that pilots with thousands of hours experience between them missed only one tiny action in their pre-take-off checks and that led to the flight ending in catastrophe? Could it be that there is something deficient in the way we all think?

Accident 1

The aircraft, a Cessna U206 Super Skywagon, F-HIDZ, built in 1965, was involved in an accident in 2005 while on the UK register. In 2017, the aircraft was bought by a company in France, who wanted to restore it and replace the piston engine with a turbine. 

The accident pilot, who was also the deputy Chief Engineer for the Maintenance Organisation, was in charge of the restoration work and intervened in all phases of the work. As co-director of the company he held a private pilots licence since 1992 and a Cessna SET class qualification since November 2015 with a total of 3,439 flight hours. He also held an associated Part 66 Aircraft Maintenance Technician Licence including categories A and B1 which allowed the re-commissioning of turbine-powered and piston-engined aircraft. 

According to the company’s Maintenance Organisation Exposition (MOE) document, in the absence of the Chief Engineer, the accident pilot was responsible for the execution of all maintenance work and all other interventions carried out by the technicians. As qualified personnel, he could also intervene in all phases of aircraft maintenance. For 25 years he had also been performing check flights of aircraft coming out of maintenance.

The pilot was performing the first check flight after restoration. Following the pre-flight inspection and an engine run up, the pilot carried out an acceleration-stop along the runway with the flaps retracted, before then lining up for take-off. 

“The aircraft left the centreline in a steep bank, dragging the wingtip on the ground…”

After rolling for approximately 200m, at around 54kt with the control yoke slightly oriented to the right, the aircraft began to bank slightly to the left as the aircraft rotated prior to unstick. The pilot countered to the right by turning the control yoke as far as it would go. The aircraft continued to bank (to approx 30° to 40°) and the left wingtip struck the runway. 

The aircraft deviated to the left of the runway centreline about one metre above the ground, remaining highly banked and with the wingtip still in contact with the ground. The pilot applied full right rudder up the stop and reduced the power by putting the propeller into ‘Beta’ mode. The aircraft came to a stop left of Runway 20R and the pilot evacuated the aircraft after having made the switches safe. Subsequent inspection of the aircraft in the workshop revealed the aileron control cables crossed at the wing bell-cranks.

The accident pilot had just resumed work on F-HIDZ when the Covid-19 pandemic began and lockdowns prevented further work. He then returned to work, alone, on the aircraft 10 days later. He stated that he had doubts about the correct path during the assembly of the new cables. He checked the Service Manual but the diagram was not clear and he had difficulties interpreting it.

The MOE specified that carrying out a task without independent inspection could only be undertaken if no other qualified person was available to perform and control the task. However, the procedure had to remain exceptional: troubleshooting flight-line operations or on a temporary basis. 

The pilot declared that due to the absence of someone available to carry out an independent inspection, only four employees out of 39 having returned to work, he carried out the re-inspection himself three days after cable installation. He added that he was under significant stress due to time and financial pressure and an abnormal workload due to the exceptional circumstances generated by the pandemic.

The pilot indicated that at the holding point before lining up on the runway, he ‘followed the pre- take-off checklist’ and checked the free travel of the flight controls without looking outside the aircraft to confirm the correct direction of the aileron travel.

Accident 2

The pilot stated that he made a return trip to Pointe-à-Pitre, Antigua in a Piper PA32 the morning of the accident and then ferried the PA32 to Saint-François in early afternoon for maintenance. While there, he was asked by the operator to ferry a Piper PA23 Aztec, N529EG, an aircraft he had flown regularly in the past, back to Pointe-à-Pitre as the aircraft was needed for a flight to Dominica at the end of the afternoon.

The PA23 Aztec is equipped with two 250hp Lycoming IO-540 piston engines. It was built in 1975 and had a total of 5,587 flight hours. On PA23 type aircraft, the manual elevator and rudder trim controls are composed of a crank and a central knob located on the crank. These controls are located in the roof of the cabin. Turning the crank clockwise trims the aircraft nose up, turning the central knob clockwise moves the rudder trim to the left. The two trim position indicators are also located in the roof, behind the crank. 

On light piston aircraft, the elevator trim control is normally located in the lower central area of the cockpit. N539EG was also equipped with an electrical trim system for controlling the elevator trim and connected to an autopilot. It consisted of an ON/OFF button in the upper left part of the instrument panel, a circuit breaker on the fuse panel and a switch on the pilot yoke (UP/DOWN) to control the elevator trim. This system had been deactivated several months before the accident following installation of new avionics, which had resulted in mutual interference.

On the pilot’s arrival at the Saint-François workshop, a mechanic positioned N539EG ready for departure. The pilot didn’t want to waste time as the aircraft was blocking the parking area and the taxiway to the runway. He stated that not having flown a PA23 for a long time, he had placed the flight manual within easy reach. 

The pilot started the engines, checked the flight controls and carried out an engine run with the mechanic on board. The mechanic then left the aircraft with the engines at idle while the pilot prepared the PA23 for take-off. He set the flaps at the first notch then carried out a visual check of the various other cockpit controls and checked proper closure of the door. His check did not take in the overhead panels as he was not used to including these in his visual scan and he did not use a printed checklist or the flight manual. 

The pilot stated that he applied power against brakes before releasing them and that the take-off run was normal. Upon rotation at 65kt he felt the controls were heavier than normal and that after retraction of the flaps, the controls became heavier still and the aircraft had a tendency to pitch down.

The pilot tried to use the electrical elevator trim located on the control yoke, then the manual control in the lower part of the instrument panel without finding it. Although he was initially able to overcome the nose-down moment, the load on the control column required to maintain a positive pitch attitude increased rapidly with speed. The pilot had to keep both hands on the control column to counter the forces and was therefore unable to reduce the power of the engines.

“The pilot was ejected from the cockpit area as it broke up in the 180kt impact”

Unable to prevent his descent, the pilot made a right turn above the bay of Saint-François avoiding boats and dwellings and witnesses saw the aircraft subsequently hit the water surface hard in the lagoon and sink. The investigation found that the aircraft hit the water at around 180kt. The subsequent dislocation of the cockpit area allowed the ejection of the pilot’s seat forward during the high speed impact with the sea and fortuitously spared the pilot more serious injuries or even death.

The pilot had no memory of the impact until he found himself on the water surface still attached to his seat. When he became detached from the floating seat he clung onto it as he could not swim and waited to be rescued by local boats. He believed it possible that he took off with the elevator trim incorrectly set and that time pressure due to the need to ferry N539EG promptly, as well as a need to clear the aircraft parking area, led him to ignore the printed checklist and to carry out only visual checks. 

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