SR111: Reality check please

Date:         05 Oct 98 00:26:51 
From:         JF Mezei <>
Followups:    1 2
Next article
View raw article
  or MIME structure

I have seen some news-releases from US law firms stating that the MD11
is capable of an emergency descent at 6000 feet per minute. Can anyone
confirm this ? If the 6000 number is not accurate, please substitute it
with the proper number in subsequent questions.

When a pilot is told that the threshold for a runway is X miles away,
does this mean that the pilot must plan to be at altitude 0 at the
threshold ? If not, how high must he be ? and how far would that
threshold be from the actual runway ?

If one is to make an emergency descent at 6000 feet/min, how far from
the threshold (and how high) must he level the plane to make final
approach ?

During a descent, how fast can an MD11 go in terms of airspeed ? During
an emergency 6000ft/min descent, how slow could that plane go ? How long
would it take to slow the plane from its descent speed to a speed
acceptable for landing? (in time or distance units).

- - - - - -

In the case of TWA800, the engines continued to run even after the plane
was decapitated (cockpit lost). On a plane of that vintage, would the
engine throttles simply stay where they were or would the fuel pumps
stop working and engines just run for a while on what is left in the
lines ?

Assuming that there was total failure in the MD11 cockpit and that the
cockpit was electrically separated from the rest of the plane. Would the
MD11's engines continue to operate at the last throttle level which was
set, or would they just exhaust whatever fuel is left in their lines ?
Do the electrical systems of an engine (fuel pump, FADEC etc) operate
directly off the engine's generator or do they feed from the airplane's
power buses ?

- - - - - - -

We know that the plane was "viable" between 22:15 and 22:26, roughly 11
minutes between the time the pilots started to act on Halifax and the
time the electrical system failed. We also know that the plane was able
to sustain a certain level of control after that (from the fact that the
plane made a tight circle - is that a correct assumption ?).

Swissair's simulator said that it would have been physically impossible
for them to land the plane without making the detour at Peggy's cove.
Lawyers state that it could have been and that the plane could have
descended faster without problem. But the question is: even if it could
descend fast enough, would it have been able to travel the horizontal
distance to Halifax ?