Accident to the Airbus AS 350 B3 registered F-GKMQ on 07/01/2019 at Puylaurens (Tarn)

Cat. 2 investigation report: simplified-format report, adapted to the circumstances of the occurrence and the investigation stakes.

As part of the construction of a tower for a telephone operator, Airplus Helicoptères was responsible for lifting and positioning by helicopter, the six sections of the tower. The pilot of F-GKMQ lifted the first three sections without incident. In order to install the fourth section, the pilot picked up the load and moved it towards the structure being built. He held the helicopter in hover in order to position the section overhead the assembly and allow the technicians to put it in place more accurately. A first positioning pin was then attached to the first anchor point of the element. The two other pins were about to be fitted when the helicopter slightly descended and then suddenly climbed with the section, separating it from the rest of the structure. The pilot lost control of the helicopter which entered a roll, striking trees before the left side collided with the ground below the tower installation zone.
The investigation was able to determine that this loss of height in hover was caused by a lowering of the collective pitch lever in the cockpit, almost certainly initiated manually by the pilot. However, it was not possible to explain why the pilot made this input on the collective pitch lever.
Some possible hypotheses are:

• A sudden aerological disturbance (turbulence, gust of wind) that destabilised the pilot and prevented him from maintaining hover.
• An involuntary action of the pilot following an unexpected occurrence in the cockpit (fall of an object, presence of an insect).
  • A temporary loss of control in maintaining hover as the possible consequence of:
     - physical fatigue from hovering with a load a few moments earlier (a manoeuvre known to be physically demanding and which had lasted several minutes), or
    - a sudden or disproportionate action.
• A temporary incapacitation of the pilot.

Immediately after this loss of height, the pilot pulled firmly on the collective pitch lever, which caused the helicopter to suddenly climb. This excessive increase in the helicopter’s height caused tautness of the sling followed by separation of the load. The absence of personnel standing straight ahead meant that the load could be released safely.
Given that all of the release hooks were operational at the time of the occurrence, it is likely that the pilot did not activate the release commands during this sequence. After this, the pilot did not manage to regain control of the helicopter, which adopted an unusual attitude when the load fell back down and until it collided with the ground.
The investigation was unable to prove that the F-GKMQ accident was caused by an in-flight incapacitation. Nevertheless, hypotheses calling into question the pilot’s state of health were examined. The investigation brought to light that the pilot had been suffering from chronic back pain that he had not deemed necessary to mention to his doctors and that he had been reluctant to undergo the further examinations recommended by the medical examiner. Moreover, the pilot, suffering from heart disease, had had numerous cardiovascular risk factors for several years which had not been sufficiently taken into account during his previous medical fitness examinations. Finally, the pilot was asked to carry out additional medical examinations at the end of his last medical fitness examination.
The BEA has addressed three safety recommendations to the DSAC aiming:

• to take better account of the cardiovascular risk factors in the assessment of the pilot’s medical fitness, by adding an annex specific to this risk summarizing the main factors to be assessed, as well as the results of the assessment of these factors.
• to work towards better coordination between the medical fitness examiner and medical practitioner, by encouraging the medical examiners to include in the medical examination report, the prescriptions for the medical examinations the pilot is asked to carry out and to accompany their prescriptions with an exchange in writing with the crew’s personal physicians when additional medical examinations are recommended.