You can't convert the absolute minimum amount of energy into a magical climb. Yes, some conspiracy theorists like to blame "the computers" but I'd like to see them put another type into the same situation and try to get out of it.
Jetlagged From United Kingdom, joined Jan 2005, 2505 posts, RR: 24 Reply 2, posted (3 years 11 months 1 week 4 days 17 hours ago) and read 2528 times:
There's no mystery about the crash. The A320 was brand new technology and there was a perception that it was stall-proof. Possibly the crew believed it would always get them out of trouble.
The crew did a low speed fly-by at an airshow, IIRC not approved in advance. The aircraft was configured for landing. It floated down the runway at idle maintaining height with airspeed bleeding off. Without sufficient kinetic energy all the FBW could do was slowly increase angle of attack, getting ever nearer to a stall. At alpha floor, thrust automatically increases to GA power (even if the thrust levers are at idle) which would enable the aircraft to climb away. The aircraft did what it was designed to do, but because the crew did not apply thrust early enough there was no way it could climb and avoid the trees. The aircraft was simply flying too slowly.
The crew claimed the engines would not respond and the altimeters were reading 100 ft when the aircraft was actually as low as 30 ft.
Who knows whether Norbert Jacquet should have been put in mental institutions or not. There is medical evidence that he is entirely sane. There were also rumours circulating that the black boxes were tampered with or swapped to protect Airbus. However even without such recordings, the sound of the engines spooling up as the aircraft enters the trees is enough information to realise why the aircraft crashed, if not who was responsible. There was no fault with the FBW system, just human error.
[Edited 2010-01-02 13:13:45 by jetlagged]
The glass isn't half empty, or half full, it's twice as big as it needs to be.
Jetlagged From United Kingdom, joined Jan 2005, 2505 posts, RR: 24 Reply 4, posted (3 years 11 months 1 week 4 days 17 hours ago) and read 2516 times:
Quoting Kimon (Reply 3): Which type of aircraft have you flown?
Thanks for the compliments. I'm not a professional pilot, but I've worked on and flown many airliner flight simulators (most Boeings, A320, MD-80, DC-9, Fokker F.28/100/50, etc). As a simulator design engineer I have had access to a lot of operational and design data for a wide variety of aircraft, not to mention the opportunity to discuss aircraft performance with pilots and flight engineers.
The only aircraft I've flown for real are the Cessna 152, Piper Cherokee and Beagle Pup.
The glass isn't half empty, or half full, it's twice as big as it needs to be.
Starlionblue From Greenland, joined Feb 2004, 16345 posts, RR: 66 Reply 6, posted (3 years 11 months 1 week 4 days 14 hours ago) and read 2455 times:
As mentioned above, this crash is no mystery.
I will trot out a very old post by me followed by an equally old but quite excellent post by Crosswind. I keep them for when this comes up.
A320 at Mulhouse was an in service AF aircraft doing a flyby at an airshow. So what went wrong?
- Pre flight briefing was not held.
- Flyby altitude was below French regulatory minimums.
- Flyby altitude was below the level of surrounding obstacles (trees).
- Flyby runway was changed at last minute (when in sight of the airfield).
As the plane flew by, speed and altitude were still both decreasing. Engines were at or near idle. The plane's protection systems were compensating by increasing angle of attack (to maximum). But since the plane was at stall speed, once it reached the max angle of attack the only way not to stall was to descend.
When the pilot discovered the approaching trees, it was already too late. No amount of thrust would have allowed the plane to clear the trees. On the video you clearly hear the engines spooling up just in time to become woodchippers.
Pilot flying had overconfidence in the plane's control system allowing him to perform a dramatic low speed flyby. In fact, without the control system and envelope protection, the plane might have stalled (it never did). But not stalling is not enough. You also have to avoid hitting the ground.
Nothing was wrong with the plane, and all components performed according to (or beyond) specs.
And yes, if the pilot had tried the same stunt in a 737 or any other plane, there would still have been a crash. Nothing in the control systems of the A320 stopped the pilot from applying go around power and trying to fly himself out of the corner. This is when the old pilots say something like: "Use your superior skills to keep yourself out of situations where you might need to use them".
Airbi may have very cool envelope protection systems, but they can't break the laws of physics.
From United Kingdom, joined Nov 2000, 1379 posts, RR: 41
Posted Wed Apr 21 2004 21:19:54 UTC+1 and read 147 times:
Some information on the Air France A320 crash, in the hope that people will stop spouting unsupported theories about it!
The Air France A320 that was written off at Habsheim was being operated on a public transport flight by Air France at the time of the crash. The aircraft had been used in flight testing, but had been delivered to Air France several days before the accident, and was involved in a promotional flight when it crashed. The A320 was in service operating revenue flights at the time of the accident, F-CFKC was in fact Air France's 3rd A320.
Most importantly, the fly-by-wire did not "lock up" - and the plane did not "think" it was landing and prevent the application of TOGA power. The accident was classic pilot error, no fault was found with the FBW system..
Some findings of the accident investigation:
• The captain had participated as Air France's technical pilot in developmental test flying on the A320, during which manoeuvres were carried out beyond the normal operational limitations. This could have lead to overconfidence in the systems of the new aircraft.
• The flight had only been briefly prepared, without real consultation between the departments (of Air France) concerned, or with the crew.
• Descent was started 5.5nm from the aerodrome. Throughout the descent, the engines were throttled back to flight idle with the airspeed reducing.
• At 1000ft AGL the rate of descent was still ~600fpm.
• The captain levelled off at a height of ~30ft, engines at flight idle, pitch attitude increasing. He did not have time to stabilise the angle of attack at the maximum value he had selected.
• Full-power was rapidly applied when the angle of attack was 15° and the airspeed 122kt.
• The response of the engines was normal, and in compliance with their certification.
• The accident resulted from a combination of the following;
• Flyover height lower than surrounding obstacles (Flown at 30ft against the planned 100ft)
• Slow speed, reducing to reach maximum angle of attack
• Engines at flight idle
• Late application of go-around power
In summary the crew flew the aircraft onto the wrong side of the drag curve in a critical situation overflying a very small grass strip with trees above the height of the aircraft off the end of the runway, the aircraft was low, slow and at a high angle of attack - there was no residual energy to get them out of trouble. It's a basic lesson in flying, and the A320 was found to have actually exceeded it's certified performance once TOGA power was selected.
The crew had been briefed to overfly the concrerte runway 02/20 at 100ft, but unknown to them the airshow was alligned along grass strip runway 16/34. The crew were unaware of this until descending through 200ft, 24 seconds before the accident, at which time they had to chose to reposition the aircraft to conduct an overflight they had not briefed for over runway 16/34 as the height decayed to 30ft and the airspeed to 122kt...
If you're interested in the subject Macarthur Job's "Air Disaster" series is excellent - the Habsheim A320 accident is covered in depth in Volume 3.
"There are no stupid questions, but there are a lot of inquisitive idiots." - from Citadel by John Ringo