Air France Flight 296
|Date||26 June 1988|
|Site||Mulhouse–Habsheim Airport, Mulhouse, France
|Aircraft type||Airbus A320-111|
Air France Flight 296 was a chartered flight of a new fly-by-wire Airbus A320-111 operated by Air France. On 26 June 1988, it was flying over Mulhouse–Habsheim Airport (ICAO code LFGB) as part of an air show. The low-speed flyover (with landing gear down) was supposed to take place at an altitude of 100 feet (33 metres) AGL (above ground level); instead, the plane performed the flyover at 30 feet, skimmed the treetops of the forest at the end of the runway, and crashed to the ground—killing three passengers. This was the first crash of an A320 aircraft.
Flight deck crew
Captain Michel Asseline, 44, had been an airline pilot with Air France for almost 20 years and had the following endorsements: Caravelle, Boeing 707, 727, and 737, and Airbus A300 and A310. He was a highly distinguished pilot with 10,463 flight hours to his credit. A training captain since 1979, he was appointed to head the company's A320 training subdivision at the end of 1987. As Air France's technical pilot, he had been heavily involved in test flying the A320 type and had carried out manoeuvres beyond normal operational limitations. He had total confidence in the aircraft's computer systems.
First Officer Pierre Mazières, 45, had been flying with the company since 1969 and had been a training captain for six years. He was endorsed on Caravelle, Boeing 707 and 737, and had qualified as an A320 captain three months before the accident. He had 10,853 hours of flight time under his belt.
At the time of the incident, only three of the new aircraft type had been delivered to Air France, and the newest one (in service for two days) had been chosen for the flyover.
The aircraft was to fly from Charles de Gaulle Airport to Basel–Mulhouse Airport for a press conference. Then, sightseeing charter passengers would board and the aircraft would fly the short distance to Habsheim aerodrome. The captain would make a low-level fly-pass over Runway 02, climb up and turn back, and repeat the fly-pass over the same runway in the reciprocal direction (Runway 20). This would be followed by a sightseeing trip south to Mont Blanc before the passengers would be returned to Basel–Mulhouse Airport. Finally, the aircraft would return to Paris.
The pilots had each had a busy weekend and didn't receive the flight plan until the morning of the flight. They received no verbal details about the flyover or the aerodrome itself.
The flight plan was that as they approached the airfield, they would extend third-stage flap, lower the landing gear, and line up for level flight at 100 feet. The Captain would slow the aircraft to its minimum flying speed with maximum angle of attack (nose-up attitude), disable the "Alpha Floor" (the function that would otherwise automatically increase engine thrust when the angle of attack reached 15°) and rely on the First Officer to adjust the engine thrust manually to maintain 100 feet. After the first pass, the First Officer would then apply TOGA (Take Off, Go Around) power and climb steeply before turning back for the second pass. "I've done it twenty times!" the Captain assured his First Officer.
The flyover had been approved by Air France's Air Operations Directorate and Flight Safety Department, and Air Traffic Control and Basel Tower had been informed.
Habsheim aerodrome was too small to be listed in the aircraft's flight computer, therefore requiring a visual approach; both pilots were also unfamiliar with the airfield when they began their descent from 2,000 feet only 6 nautical miles (11 km) from the field. This distance was too short for them to stabilize the aircraft's height and speed for the flyover.
Additionally, the Captain was expecting from the flight plan to do the pass over Runway 02 (3,281 feet long, paved) and was preparing for that alignment. But as the aircraft approached the field, the flight deck crew noticed that the spectators were gathered beside Runway 34R (2,100 feet long, grass). This last minute deviation of the approach further distracted the crew from stabilizing the aircraft's altitude and they quickly dropped to 40 feet.
From higher up, the forest at the end of 34R had looked like a different type of grass. But now that the aircraft was performing its flyover at only 30 feet, the crew noticed the aircraft was lower than the now-identified hazard that they were fast approaching.
- First Officer: "TOGA power! Go around track!"
The crew applied full power and the pilot attempted to climb. However, the elevators did not respond to the pilot's commands, because the A320 computer system engaged its 'alpha protection' mode (meant to prevent the aircraft entering a stall.) Less than five seconds later, the turbines began ingesting leaves and branches as the aircraft skimmed the tops of the trees. The combustion chambers clogged up and the engines failed. The aircraft fell to the ground.
Traditionally, pilots respect the inherent dangers of flying at low speeds at low height, and normally, a pilot would not attempt to fly an aircraft so close to stalling with the engines at Flight Idle (minimum thrust). But in this instance, the pilots involved did not hesitate to fly the aircraft below its normal minimum flying speed because the whole purpose of the flyover was to demonstrate that the aircraft's computer systems would ensure lift would always be available regardless of how the pilots handle the controls. The Captain's previous experience flying the aircraft type at the edge of its limits may have led to overconfidence and complacency.
The official investigation was carried out by the Bureau d'Enquêtes et d'Analyses pour la Sécurité de l'Aviation Civile (BEA), the French air accident investigation bureau, in conjunction with the airline and the aircraft manufacturer.
The flight recorders were found still attached in the unburnt tail section. The Cockpit Voice Recorder (CVR) continued to operate for about 1.5 seconds after the initial impact. The Digital Flight Data Recorder (DFDR) continued to operate for about one second, then recorded nonsensical data for another two seconds. Interruption of the power occurred forward of the tail section—most probably in the wheel well area, which was heavily damaged.
The CVR was read during the night of 26 June at the BEA. The transcription was later clarified with the assistance of the pilots involved. The tape speed was set using the 400 Hz frequency of the aircraft's electrical supply and then synchronised with the air traffic control recordings, which included a time track.
The DFDR was read the same night by the Brétigny sur Orge Flight Test Centre:
- 12:43:44 the aircraft begins its descent (initially at 300 feet per minute) from 2000 feet with 'Flaps 1'.
- 12:44:14 the engine power is reduced to flight idle. Three seconds later, the undercarriage is extended. A further 10 seconds later, 'Flaps 2' is selected.
- 12:44:45 'Flaps 3' is selected as the aircraft descends through 500 feet at an airspeed of 177 knots.
- 12:45:06 the aircraft descends through 200 feet at an airspeed of 155 knots.
- 12:45:15 the aircraft, now at 90 feet, begins a deviation to the right (maximum bank angle: 30°) to line up with the grass strip 34R.
- 12:45:23 the aircraft completes the deviation at a height of 46 feet and an airspeed of 141 knots. During this manoeuvre, a fluctuation in the radio altimeter height corresponds to the aircraft passing over a patch of trees. (Before and after this fluctuation, the readings of the radio altimeter and those of the barometric altimeter match perfectly). Three seconds later, the aircraft descends through 40 feet at an airspeed of 132 knots. The Captain begins to flare the aircraft (he lifts the nose 4°) to level its flight. The aircraft levels off at 30 feet.
- 12:45:30 nose-up attitude increases to 7°.
- 12:45:35 nose-up attitude is now 15° and speed is 122 knots. TOGA power is applied. Four seconds later, the aircraft begins striking the treetops.
Aircraft and engines
The investigators found the aircraft to have been airworthy, that its weight and center-of-gravity had been within limits, and that there was no evidence of mechanical or electronic systems failure.
The flight deck crew believed that the engines had failed to respond to the application of full power.
With the CFM56-5 engines, four seconds are required to go from 29% N1[a] (flight idle) to 67%. It then takes one second more to go from 67 to 83% N1. From the engine parameters recorded on the DFDR and spectral analysis of the engine sounds on the CVR, it was determined that five seconds after TOGA power was applied, the N1 speed of Nº1 engine was 83% while that of Nº2 engine was 84%. Spectral analysis of the engine sounds indicated that 0.6 seconds later, both engines had reached 91% (by this stage, they were starting to ingest vegetation). This response of the engines complied with their certification data.
The official report from BEA concluded that the probable cause of the accident was a combination of the following:
- Very low flyover height, lower than surrounding obstacles;
- Speed very slow and reducing to reach maximum possible angle of attack;
- Engines speed at flight idle; and
- Late application of go-around power.
Furthermore, the bureau concluded that if the descent below 100 feet was not deliberate, it may have resulted from a failure by the crew to take proper account of the visual and aural information available to them regarding the elevation "above ground level" (AGL) of the aircraft.
Captain Asseline, First Officer Mazières, two Air France officials and the president of the flying club sponsoring the air show were all charged with involuntary manslaughter. All five were found guilty. Captain Asseline was initially sentenced to six months in prison along with 12 months of probation. The others were sentenced to probation. During the appeal process, Captain Asseline's sentence was increased to 10 months of imprisonment along with 10 months of probation. Asseline walked free from the court and said he would appeal to France's Supreme Court, the Cour de Cassation. According to French law, Asseline was required to submit himself to the prison system before his case could be taken up by the Supreme Court.
A documentary on the National Geographic channel made a detailed claim that the flight recorder might have been tampered with and indicated that four seconds had been cut from the tape; this was shown by playing back a control tower tape and comparing it to the remaining tape. This indicated a problem with the aeroplane's fly-by-wire system rather than pilot error. It is claimed that the flight data recorders had been switched and were not the original ones in the aeroplane. Airbus, however, made a detailed rebuttal of these claims in a document published in 1991. Airbus contends that the independent investigator employed by the filmmakers made an error when synchronising the recordings, based on a misunderstanding of how the "Radio Transmit" parameter on the flight data recorder actually functioned.
On 8 March 2010, an episode of the Mayday (Air Crash Investigation, Air Emergency,'Air Disasters) TV series featuring this accident was broadcast. The episode is entitled "Pilot vs. Plane". The episode "Blaming the Pilot" of Survival in the Sky featured the accident.
- List of accidents and incidents involving commercial aircraft
- List of airshow accidents and incidents
- The speed of the Stage 1 fan of a turbofan engine, expressed as a percentage of normal maximum
- Job, Macarthur (1998). Air Disaster Volume 3. Australia: Aerospace Publications. p. 155. ISBN 1 875671 34 X.
- Accident description at the Aviation Safety Network. Retrieved on 3 February 2007.
- Commission d'Enquête sur l'accident survenu le 26 de juin de 1988 à Mulhouse-Habsheim (68) à l'Airbus A 320, immatriculé F-GFKC – Rapport Final. 1990. (Archive)
- (French) Commission of Inquiry into the accident on 26 June 1988 in Mulhouse–Habsheim (Archive) French: Commission de enquete sur l'accident le 26 Juin 1988 a Mulhouse-Habsheim
- Report on the Iberia Airbus A 320 crash