The Australian Transport Safety Bureau (ATSB) has focused on the spin recovery technique in its investigation into the fatal crash of a Cessna A150 Aerobat last year.
VH-CYO was being used to teach spin training south-east of the Sunshine Coast in June 2021 when it crashed after failing to recover in time. Both the instructor and the student were killed in the crash.
According to the ATSB investigation, the crew climbed to 6000 feet AMSL before spinning the aircraft to the left. It remained in a spin for about 55 seconds before impacting the ground.
"Forward movement of the aircraft and the low angle of entry indicated that the aircraft was most likely in the process of recovering from the spin when it impacted trees," the ATSB said in its investigation report released today.
Although it couldn't say definitively why the Cessna failed to recover from the spin in time, the ATSB found that the instructor was very experienced on spinning Pitts, but had little or no experience spinning A150s.
" ... the ATSB established that it was likely the instructor intended to practice two spin recovery techniques," the report states. "One of these techniques, broadly known as the Mueller/Beggs recovery method, has been shown to not recover a Cessna A150 Aerobat established in a spin to the left."
Mueller/Beggs differs from the conventional power-aileron-rudder-elevator (PARE) recovery method in that it advocates for the pilot letting go of the stick completely and using only rudder and power to correct the spin.
Of the key advocates of the method, US pilot Gene Beggs, found in 1985 that the A150 would not recover from a left spin using this technique, and required forward movement of the control yoke to bring about recovery.
A second student, who was due to fly the same training flight with the instructor in the aircraft later that day, told the ATSB they believed they would be exploring both methods of spin recovery.
“The ATSB therefore concluded it was likely the instructor was either not aware, or did not recall, that the Aerobat would not recover using this method in a spin to the left," said ATSB Director Dr Michael Walker.
Walker noted that the ATSB couldn't determine which recovery technique was applied at the various stages of the spin recovery before the crash, so could not conclude if the recovery technique contributed to the accident.
“Nevertheless, this investigation presents a timely reminder that pilots should review the POH of the aircraft type that they intend to operate, and obtain instruction and/or advice in spins and recovery techniques from an instructor who is fully qualified and current in spinning that model,” Walker said.
The ATSB also discovered the Cessna was over maximum take-off weight for the accident flight, and that if the aircraft had entered a flat spin, this may have hampered recovery.
The ATSB has since issued an advisory note to aerobatic pilots and instructors, warning that:
- the Mueller/Beggs method of spin recovery does not recover all aircraft types from a spin
- the Mueller/Beggs spin recovery method limitations should be emphasised during spin theory
- the Mueller/Beggs method of spin recovery will not recover a Cessna A150 Aerobat or similar variants from a spin in some circumstances
- they should review the pilot’s operating handbook of the aircraft type that they intend to operate for the recommended spin recovery technique prior to doing spins in any model aircraft,
- they should obtain instruction and/or advice in spins from an instructor who is fully qualified and current in spinning that model.
The full investigation report is on the ATSB website.