Pilots conducting parachute operations should undergo training for a specific rating, Swedish investigators are recommending, following a fatal accident involving a De Havilland Canada DHC-2.
None of the nine occupants, comprising the pilot and eight parachutists, survived the crash, which occurred shortly after take-off from Orebro on 8 July 2021.
Swedish investigation authority SHK says the aircraft’s centre-of-gravity was outside of the permitted range, but that all the pilots who flew it had been of the opinion that there was “no risk” that the aircraft could be loaded outside of the aft envelope.
SHK says there was “no system” for calculating the mass and balance before the flight.
It found that load instructions were drawn up in 1989, when the aircraft’s centre-of-mass was close to the forward limit. This led to a requirement to place fuel in the aft fuselage tank, to avoid the aircraft’s becoming nose-heavy with only a single pilot.
But the aircraft subsequently underwent modifications, including repairs, engine replacement, and installation of aft ballast. The centre-of-gravity gradually moved aft and there was no longer a need to carry fuel in the aft tank – but this was not noticed.
SHK says the routine for loading the aircraft worked “in most cases” to keep the aircraft in balance, but only when the right-hand pilot’s seat was removed, enabling parachutists to sit further forward.
But it adds: “A latent risk had been created with an incorrect instruction in a document that should help the pilot load the aircraft correctly.”
Precautions implemented during the pandemic included replacing the pilot’s seat, to distance the pilot from the parachutists. This meant two parachutists had to sit further back, increasing the risk that the centre-of-gravity would fall behind the aft limit.
“The loadsheet that the pilot received from the parachute club before the flight indicated the weight of each parachutist but not where the parachutist intended to sit,” says the inquiry. “The pilot could not know how the balance was affected by the parachutist.”
SHK says the aircraft had been operated in the same way, in the same parachute club, and this probably resulted in false perceptions of safety.
The inquiry found the aircraft had taken off with its elevator trim in an unusual position, and suggests the pilot, using memory actions rather than a checklist before departure, did not set the trim correctly.
As the aircraft rotated, the trim caused the nose to pitch up more than usual, forcing the pilot to counteract with stronger-than-normal forces. Combined with the aft load imbalance, the aircraft was unstable as it climbed and control was probably lost when the flaps were retracted.
The DHC-2 reached 400-500ft above ground before banking left – either because it stalled or the pilot deliberately banked to reduce pitch. It turned 180°, entered a dive and descended rapidly, landing heavily and skidding on its fuselage underside for 48m before catching fire.
SHK says that, over the years, the operation suffered “several safety procedural drifts” which gradually reduced safety margins. “Each individual hazard may not alone entail any immediate risk of an accident, but when they all coincided at the same time, the conditions for the accident were created,” it says.
No special rating is required to act as an aircraft commander during parachute operations, despite the significant complexity and quicker pace.
“There is reason to question whether it is reasonable to expect that every pilot conducting parachute operations has sufficient tools in order to perform a risk analysis,” adds SHK, which is recommending that the European Union Aviation Safety Agency considers introducing formal training leading to a rating for pilots undertaking parachute operations.
Skane Skydiving Club subsidiary Kalle David Flyg owned the aircraft, and leased it to Orebro Skydiving Club. After the accident, says SHK, Skane Skydiving Club developed a system for calculating mass and balance, which also considers changes when parachutists exit the aircraft. Kalle David Flyg has developed an operating manual for parachute operations including standard procedures and limitations.
