LH A320 Rough Landing @ Hamburg

[Chris Scott]

Sidestick indication on PFD. Habsheim Accident.

Quotes from CONF iture:
1) To go back to the topic and your anecdote, how did you notice your FO was trying to steer with the sidestick ?
2) What has been your view on Habsheim and how did you deal with that event afterward ?
[Unquote]

1) In ground mode, the position of the sidestick(s) is displayed by a white cross on the PFDs.

2) HABSHEIM [off-topic, with grovelling apologies to the Moderators]

Have not read Monsieur Asseline's book. So regret that I shall not be addressing his version of events; merely recalling the scenario as I saw it on video and read in reports. You will not be getting news, I'm afraid, and the following will be almost entirely from memory.

Habsheim was a cowboy manoeuvre – no doubt flown with the best of enthusiastic intentions – poorly planned. Even a simple low flyby of the small airfield should not have been conducted with fare-paying passengers on board, regardless of the type of aircraft. It seems to have been an attempt to exploit and demonstrate several unique features of the A320, but it showed at least one fatal misunderstanding in the repertoire of flight-envelope protections.

I don't remember if the crew created a flight-plan in the FMGS for the short flight from Basel-Mulhouse to the small airstrip at Habsheim. This could have been done easily in about 5 -10 minutes. They may not have, because they seem to have overestimated the very short distance; entering the circuit on the downwind leg at an inconveniently high speed, the CFM-56 engines at flight-idle.

Presumably, the plan was to turn on to final approach at a normal speed in landing configuration, descending at approach thrust to about 50ft. Over the threshold of the runway, they would have levelled off and, without increasing thrust, allowed the aeroplane to slow down through "alpha-prot"; the nose getting higher and higher in level flight. Below that speed, the pilot would have to pull on the sidestick to stop the nose dropping. [The deceleration can be continued to alpha-max, about 5% above the stalling IAS, after which the FBW will gradually lower the nose if necessary to avoid the stall.]

However, the assumption seems to have been that, prior to reaching alpha-max, the "Alpha-Floor" function of the autothrust (A/THR) would command TOGA thrust automatically. From approach thrust TOGA would have been achieved in less than 2 seconds, and the A/C could be rotated into an even higher pitch-attitude for a steep go-around. If the pilot got it right, this extreme and spectacular manoeuvre would be performed right in front of the crowd. At any time before or after Alpha-Floor was triggered, the pilot would have the option of selecting TOGA thrust himself, by pushing the throttles forward in the usual manner.

What appears to have happened, on the day, was that their excessive speed on joining downwind led to a wider circuit than planned, to lose height and speed, while extending gear and slats/flaps. They eventually reached the point above the runway threshold at about 50ft agl, and at or just above the right IAS. Until that moment, the whole circuit would have been flown at idle thrust, and the VIDEO suggests that idle thrust was maintained as they flew along the runway at a steady height – just above the level of the treetops at the far end. The throttle levers were probably in the idle position, with A/THR disengaged. The pilot seems to have decided to allow the aeroplane to initiate the go-around at the moment of its own choosing...

I now have in front of me a copy of the A320 BCAL Flight Technical Manual, 11-50-Page 2, dealing with "ATHR ENGAGEMENT AND ACTIVATION". The page is dated 25 August 1987, the year before the accident.

2.1 ENGAGEMENT
......
By the ALPHA-FLOOR in flight if the radioaltitude is higher than 100 feet. Engagement is indicated by:
– the illumination of the ATHR pushbutton on the FCU
– the A-FLOOR message on FMA
......
When ATHR is engaged, it can be active or inactive:
· Active: Thrust is controlled by A / THR
– by setting thrust levers between IDLE and MCT......
– by the ALPHA-FLOOR condition. In this case, A / THR commands the TO / GA thrust computed by FADEC whatever thrust levers position is and until A / THR is disengaged
. ALPHA FLOOR condition is inhibited on ground and below 100 ft during approach.

The video goes on to show the A/C continuing to fly towards the forest of trees in a nose-high attitude. Just before reaching them there are signs of power increase, if memory serves (disturbed air behind the engines), but the aeroplane starts to lose height. As it descends into the treetops, they are slightly flattened by a swathe of exhaust air from both engines. The A320 descends, apparently gently, through the treetops – wings exactly level – and disappears from view. Shortly after that, the sound of the engines spooling up finds its way to the camera microphone.

Presumably, the pilot realised that Alpha-Floor was not engaging (see FCOM above, re its inhibition below 100 ft), and finally selected TOGA himself. Unfortunately, the thrust was still at idle. This in itself would not have inhibited Alpha-Floor, but the certification requirement for jet engines allows up to a maximum of about 8 seconds for spool-up from idle thrust. The CFM-56 is somewhat quicker than that...

The fuselage remained mainly intact, if memory serves, but one passenger died in the evacuation.

It was soon suggested by the usual pundits in the media that the A320 had suffered a major failure of the engines or, more likely, of the FADEC "black boxes" controlling them. Or the computer had "decided" that the A/C was going to land, and stopped the pilot from doing otherwise. These theories were eagerly seized on by many of our pilot colleagues, particularly those flying Boeings; they had been anti-Airbus since the A310 showed Boeing how a "glass cockpit" could be designed better than on the B767/757. Perhaps understandably, the crew did nothing to set the record straight, and the conduct of the French accident investigation itself left much to be desired.

Within hours, we had decided provisionally that there was no evidence of technical failure, encouraged by the video footage. We were genuinely happy to continue flying carefully, and selling the aeroplane to our customers. Our initial diagnosis proved to be sound. It did remind some of us that the A320 was, ultimately, a flying machine subject to Newtonian Physics.

We were fortunate to have no major incidents during the years that followed; but to some extent you make your own luck.