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Old October 30th 04, 05:13 PM
David CL Francis
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On Fri, 29 Oct 2004 at 04:07:47 in message
, Pooh Bear
wrote:
Nope - they were using the analogue readout barometric altimeter not the more
accurate digital readout radalt ( for reasons of being easier to read whilst
rapidly changing in this instance ).

During the take off phase the radalt and baro altimeter somehow got
'misaligned' by 70 odd feet.

Hence they thought they were flying at 100ft when it was actually 30 ft.

The report I quoted from clearly states:

"A fluctuation in the radio altimeter height was evident during this
manoeuvre, corresponding to the aircraft passing over a clump of trees
on the approach path. Before and after this fluctuation there was
perfect agreement between the readings of the radio altimeter and the
barometric altimeter."

They then suddenly
realised there were trees ahead at the same height or higher than the
aircraft. They then called for TO power but it was too late. Speed had
reduced to 122k and the engines now at flight idle responded as they
should. There was then nothing anyone or the aircraft could do. 4.5
seconds after power started increasing it began hitting the trees.


Actually, increased power was called for as planned. They were indeed unaware
of the trees due to the poor briefing material.

Here is an extract from the report I used as a basis. I think it answers
both of your points. The trees were not the same hazard on rny 02.

CAPT: There's the airfield! It's there ... you've got it, have you?
COPILOT [Selecting 125.25 on VHF and calling Habsheim Tower]: Habsheim,
hello - we're coming into view of the airfield for the flyover.

(HABSHEIM) TWR: Yes - I can see you. You're cleared - sky is clear.
CAPT: Gear down!
COPILOT [to Habsheim Tower as the captain reduces power to flight idle
and the Airbus continues its descent at about 600fpm]: OK - we're going
in for the low altitude flyover.
TWR: Roger.
CAPT: Flaps 2!
TWR: QNH Habsheim 1012. QFE 984.
CAPT: 984 - put in 984.
COPILOT: 984 - QFE selected!
CAPT: Flaps 3! - That's the airfield, you confirm?
COPILOT: Affirmative!
(With the airfield now clearly in view and the aircraft at a height of
only 450 feet, the captain saw from the alignment of the airshow crowd
that the axis of the flying display was not along Runway 02 as he had
expected, but along a grass airstrip aligned northwest. As the aircraft
neared the airfield therefore, he gently banked it to the right to
re-align its ground track accordingly.)
COPILOT: OK, you're at 100 feet - watch it!
At this stage, the crew deactivated the Alpha Floor function, to prevent
the computerised control system from automatically applying power as the
angle of attack increased.
COPILOT [18 seconds later with the aircraft now only 40 feet above the
grass airstrip and still sinking slowly]: Watch out for the pylons ahead
- see them?(')
CAPT [finally levelling off at about 30 feet above the strip]: Yes -
don't worry.
(But as the aircraft continued over the strip at this height in its
steep noseup attitude, the pilots suddenly realised that the trees in a
forested area beyond the northwestern boundary of the airfield were at
least as high as, if not higher than, the aircraft itself.)
COPILOT [with alarm]: TOGA power! Go around track!
(The crew rapidly applied power, but as the engines began to spool up in
response, and the aircraft passed beyond the airstrip, the hundreds of
spectators watching the extremely low fly past were horrified to see the
underside of the aircraft's tail begin striking the treetops. Slowly the
Air-bus sank from sight into the trees. Moments later, an orange
fireball, engulfed in a column of black oily smoke mushroomed swiftly
above the trees as the aircraft, unseen, exploded in flames.)"

Exactly how and why the engines responded as they did has been a matter of
considerable debate.

Debate yes, no doubt, but the analysis showed that the engines spooled
up as they should.

That version of the CFM 56 ? was subsequently altered and units in service
'upgraded' following a compressor stall incident on another early A320 at
Geneva ? IIRC.


I have no information about that - I accept what you say.
--
David CL Francis