Jefferson City pilots took plane to maximum altitude

Rick,

The Lear's you flew were turbojets with small N1 fans. They tend to
work very well at high altitudes. The CRJ is a Fanjet aircraft and has
a big N1 fan that is not the best at high altitudes. From the limited
information I have on this accident, the engines on the CRJ compressor
stalled due to the high angle of attack and low airspeed these guys put
it into trying to get to FL410. The compressor stall caused the engines
to spool down and flame out which then led to the core lock. Once in
core lock, the high pressure compressor section locked up and an
inflight relight was virtually impossible.

This type of engine works great at lower altitudes, but needs TLC at the
higher levels.

BJ


wrote:

Bob,

This one certainly has me curious as to the cause. I've got very
limited experience in fanjets, but I've flown them at max operating
altitude and consider it a normal operation. In the turbojet 20-series
Lears we regularly went to FL450 in the 23 and 24B (usually after one
hour of flight) to get the fuel burns as low as possible when hauling
freight (plus, back then, there was nobody up that high and we always
got direct). In one version of the 25 we could go to FL510 although
even when very light, the climb rate going through 490 was so slow we
wondered whether we'd make 510 before time to start down (and, as you
know, you could see the curvature of the earth).

I did lose an engine at FL450 in a 24B when the captain moved the power
levers fairly quickly and an old fuel control unit couldn't handle it
at that altitude, flaming out the engine. We got a relight at 17,000
although, as I recall, the relight envelope was supposed to go to
25,000 (let's just say maintenance at that organization was not exactly
top notch - long out of business).

As a result, I'm curious as to what would cause both engines to go
quiet - the only common system is fuel, although I don't know the CRJ
systems at all and wonder whether there is/are any procedure(s) that
must be followed above a certain altitude regarding pumps or if the
company regularly flew so low that they didn't put in any additives
such as PRIST to prevent ice in the fuel. Have to contact a CRJ
captain friend of mine and see what she says. Also wondering why the
relight was unsuccessful...just doesn't make sense, jet engines are so
darn simple in operation - add fuel, ignite and go. Also wondering why
they couldn't make an airport from 410 in central Missouri.

The overheating comment on this thread is laughable. And I thought I'd
heard all of the nutty theories of aircraft accidents. Or maybe it was
some localized heavy gravity that shortened the glide range....

Your thoughts?

Warmest regards,
Rick

Mike Rapoport wrote:

Keep in mind that it takes a long time to cool fuel in the wing. The top of
the fuel is not even touching the skin after a small portion is burned off
and the fuel does not contact the leading edge either. The fuel with the
highest gel point (Jet A) is still good to below -40C (well below if memory
serves me correctly. Fuel gelling is a problem in long range aircraft or
aircraft that have been on the ramp in Thule in Jan. for a couple of days.
I would be surprised if it applied in this case. There just wasn't enough
time for the fuel to cool sufficiently.

Yes, I'd think the issue would be fuel in a small fuel line, pump or
filter where things would cool off much more quickly than the bulk fuel
in the tank.

Matt