Accident Piper PA-46-350P Malibu Mirage G-HYZA, 29 Apr 2021
ASN logo
ASN Wikibase Occurrence # 254076
This information is added by users of ASN. Neither ASN nor the Flight Safety Foundation are responsible for the completeness or correctness of this information. If you feel this information is incomplete or incorrect, you can submit corrected information.

Time:c. 15:28
Type:Silhouette image of generic PA46 model; specific model in this crash may look slightly different    
Piper PA-46-350P Malibu Mirage
Owner/operator:ZeroAvia Ltd
Registration: G-HYZA
MSN: 4636130
Fatalities:Fatalities: 0 / Occupants: 2
Other fatalities:0
Aircraft damage: Substantial
Location:near Cranfield Airport (EGTC), Bedfordshire -   United Kingdom
Phase: Approach
Departure airport:Cranfield Airport (EGTC)
Destination airport:Cranfield Airport (EGTC)
Investigating agency: AAIB
Confidence Rating: Accident investigation report completed and information captured
An electric engine and hydrogen fuel cell powered Piper PA-46-350P Malibu Mirage force landed near Cranfield Airport (EGTC), Bedfordshire, UK. The airplane sustained substantial damage. The crew were uninjured.

On the morning of the accident flight, G-HYZA was flown for approximately 16 minutes on test flight 85. The flight test team debriefed the results and prepared the aircraft for flight 86.

The plan for this flight was for the high voltage lithium (HV) battery to be switched off at the end of the downwind leg then, if able, to fly three or more circuits at 1,000 ft aal using the hydrogen fuel cell (HFC) only to provide electrical power. The flight test team discussed experimenting with combinations of higher airspeeds and propeller rpm that would reduce the aircraft angle of attack and improve the mass flow of air through the radiator which provided cooling for the HFC. This was considered as a potential strategy to manage a slow rise in temperature in the HFC which they had observed in previous flights when flying on that power source alone. The test card for flight 86 was not amended to reflect this intention.

After takeoff, the pilot turned onto the crosswind leg and climbed to the circuit height of 1,000 ft agl. During the downwind leg of the right-hand circuit, the pilot stated the power was set to 95 kW, the propeller to 2,500 rpm and the airspeed to 100 kt. Once stabilised at these parameters, which were at variance with the flight test card conditions, the observer confirmed that the HFC operating temperatures were within limits. He then instructed the pilot to reduce power to 90 kW to assess the effect on the airspeed, which reduced to approximately 95 kt. The pilot increased the power to 95 kW to regain the target speed.

The pilot set the power by reference to his display unit which was located below the throttle quadrant. When he looked up from this task, he recognised that the aircraft was in a late downwind position. He turned onto base leg and commented that they were losing speed in the turn. The observer suggested that they could increase power to 120 kW to regain the lost airspeed, then reduce power before turning off the HV battery to re-establish the test conditions. He also suggested a reduction in propeller rpm. The pilot increased power to 120 kW but did not reduce the propeller rpm. As he started to turn onto final, the pilot briefed that once he had established straight and level flight he would reduce the power slightly and turn off the HV battery leaving the electrical motors powered by the HFC. He called final on the radio and was cleared by ATC to fly through at circuit height.

Approaching the runway threshold at approximately 940 ft agl, the pilot reduced power to 90 kW, set the airspeed to 90 kt then selected the HV battery to off. Immediately, all electrical drive to the propeller was lost. The pilot and observer made several unsuccessful attempts to reset the system to restore power from the HFC with the observer stating the action to be taken and the pilot making the switch selection. The observer instructed the pilot to select the HV battery to on to reconnect the alternative power source. HV power was not restored so the observer instructed the pilot to attempt a system reset with the HFC in the off position. Electrical power was still not restored and at 440 ft agl the observer declared “the voltage is too high”, to which the pilot replied, “we’ve got to do something quick”.

The observer called for a further reset attempt and adjusted the power lever. The aircraft had now travelled the length of the runway and was at approximately 320 ft aal when the observer reported that power could not be restored.

The pilot transmitted a MAYDAY call and initiated a turn to the left to position for a landing on Runway 21. Almost immediately he recognised that he did not have sufficient height to complete the manoeuvre so lowered the landing gear and selected full flap for a forced landing in a field that was now directly ahead on a north-westerly heading. The aircraft touched down at approximately 87 kt ground speed on a level grass field. The pilot applied the brakes, and the aircraft continued its movement until it struck, and passed through, a hedge during which the left wing broke away. The nosewheel and left main wheel entered a ditch and the aircraft came to an abrupt stop. The pilot and observer were uninjured and exited the aircraft through the upper half of the cabin door.

The airport fire service arrived quickly at the scene. The observer returned to the aircraft and vented the hydrogen tank to atmosphere and disconnected the HV battery to make the aircraft safe.

AAIB Conclusions
The accident occurred when electrical power was lost to both motors as the power source was changed, and the inverters locked out, at a position in the circuit where the aircraft could not safely glide to the runway. A number of factors contributed to the accident:
● Sufficient ground testing had not been carried out to determine the effect of the back voltage from a windmilling propellor on the inverter protection system.
● The emergency procedure to clear an inverter lock out after the protection system operated was ineffective.
● An investigation had not been carried out into a previous loss of power resulting from an inverter lock out, which occurred three flights prior to the accident flight.
● The risk assessment had not been reviewed following the loss of propulsion on two previous flights.
● Ad hoc changes were made to the flight test plan, including the position where the electrical power source was switched, without the knowledge of the competent person.

G-HYZA met all the requirements to be flown under E Conditions and a comprehensive dossier was produced by the competent person. However, this was a complex project, and the competent person was unable to completely fulfil his responsibilities as detailed in CAP1220. The competent person’s involvement was restricted in a number of areas due to issues within the organisational relationships, the fast tempo of the project, other work commitments and restrictions from the COVID-19 pandemic. The operator’s chief executive and the flight test director took on the day-to-day management responsibility for much of the programme. However neither individual had the necessary safety and flight test experience for that role and their focus was primarily on meeting key project targets.


7. (photo)
8. AAIB Final Report:

Accident investigation:
Investigating agency: AAIB
Status: Investigation completed
Download report: Final report
Other occurrences involving this aircraft

28 Sep 1999 N666LP Southern Aircraft Conslutancy Inc Trustee 0 Eastleigh Airport, Southampton, Hampshire sub



Revision history:

29-Apr-2021 16:24 gerard57 Added
29-Apr-2021 17:22 RobertMB Updated [Time, Aircraft type, Registration, Cn, Operator, Location, Destination airport, Source, Damage, Narrative]
29-Apr-2021 19:46 aaronwk Updated [Narrative]
29-Apr-2021 19:49 Captain Adam Updated [Aircraft type, Narrative]
30-Apr-2021 01:53 Dr. John Smith Updated [Cn, Departure airport, Source, Embed code, Narrative]
30-Apr-2021 04:01 RobertMB Updated [Cn, Embed code, Narrative]
30-Apr-2021 11:59 Aerossurance Updated [Nature]
30-Apr-2021 19:03 Aerossurance Updated [Phase, Source]
01-May-2021 09:15 Aerossurance Updated [Source, Embed code, Narrative]
02-May-2021 07:13 Aerossurance Updated [Source, Embed code]
02-May-2021 14:12 harro Updated [Source, Narrative]
28-Jul-2021 14:51 Dr. John Smith Updated [Category]
28-Jul-2021 14:52 Dr. John Smith Updated [Source]
08-Jul-2022 16:58 harro Updated [Narrative, Accident report]
08-Jul-2022 18:36 Dr. John Smith Updated [Source, Narrative]
08-Jul-2022 19:36 Dr. John Smith Updated [Embed code]

Corrections or additions? ... Edit this accident description

The Aviation Safety Network is an exclusive service provided by:
Quick Links:

CONNECT WITH US: FSF on social media FSF Facebook FSF Twitter FSF Youtube FSF LinkedIn FSF Instagram

©2023 Flight Safety Foundation

1920 Ballenger Av, 4th Fl.
Alexandria, Virginia 22314