Jefferson City pilots took plane to maximum altitude

The reason these engines failed is MORE COMPLICATED than the fact they
were at 41,000'. These planes can fly at 41,000'. What happened is
related to how they got to 41,000'. They got there by exceeding the
maximum climb rate. The plane was empty so it climbed very fast. But
due to some complicated factors, the engines cannot go to that altitude
that fast. They overheated. This was a published limitation. They
exceeded it. Even my simple explanation is not adquate as it is more
complicated than this. This is due to the fact that I don't completely
understand it either.

And to answer your question, yes it is safe to operate at max altitude,
if the pilot follows all of the correct procedures when operating the
plane and if the plane does not have damage and has been maintained
correctly etc. The plane has been tested there, and higher still, so
there is some safety factor.

These engine failures were from some complicating factors. Not just as
simple as flying too high.

One word of advice. Don't get your accurate information from the
newspapers. You have to go deeper to get accurate information.

Not to drag this out any further than necessary, but searching Part 25 for
maximum altitude gets me two hits, both dealing with pressurization.
Searching for maximum certificated altitude gets one hit, dealing with
electrical systems.

Bob Gardner

wrote in message
oups.com...
The reason these engines failed is MORE COMPLICATED than the fact they
were at 41,000'. These planes can fly at 41,000'. What happened is
related to how they got to 41,000'. They got there by exceeding the
maximum climb rate. The plane was empty so it climbed very fast. But
due to some complicated factors, the engines cannot go to that altitude
that fast. They overheated. This was a published limitation. They
exceeded it. Even my simple explanation is not adquate as it is more
complicated than this. This is due to the fact that I don't completely
understand it either.

And to answer your question, yes it is safe to operate at max altitude,
if the pilot follows all of the correct procedures when operating the
plane and if the plane does not have damage and has been maintained
correctly etc. The plane has been tested there, and higher still, so
there is some safety factor.

These engine failures were from some complicating factors. Not just as
simple as flying too high.

One word of advice. Don't get your accurate information from the
newspapers. You have to go deeper to get accurate information.

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

wrote
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.

That is what I suspect. In the Boeing jetliners, we didn't use
the additives (too expensive), but we did have fuel heaters on
the main filters to keep them from "waxing" over. A "one minute"
shot of hot bleed air every 30 minutes usually did the trick,
however I have had to reduce the cruise altitude and increase
the mach number to keep the tank boost pumps operating.

Bob Moore

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

Bob,

Word on the street now is that it may have been something called "core
lockup" on both engines. Bombardier claims it's never happened on an
in-service engine, however.

More he
http://www.ntsb.gov/events/2005/Pinn...its/323843.pdf

All the best,
Rick

wrote in message
oups.com...
Word on the street now is that it may have been something called "core
lockup" on both engines. Bombardier claims it's never happened on an
in-service engine, however.

More he
http://www.ntsb.gov/events/2005/Pinn...its/323843.pdf

If I read that right (and I'm not sure I did), "core lockup" is something
that happens to an engine that has been stopped. That is, it's not a cause
of engine stoppage, but rather it's a cause of not being able to restart the
engine once it's been stopped. Something else needs to stop the engine
first (eg in their testing, they shut down the engine and let it spool down,
and THEN test for "core lockup").

Pete

wrote in message
oups.com...
The reason these engines failed is MORE COMPLICATED than the fact they
were at 41,000'. These planes can fly at 41,000'. What happened is
related to how they got to 41,000'. They got there by exceeding the
maximum climb rate.

Interesting theory. Please share with us where you obtained that
information.

Your theory seems the most plausible of anything I've heard, but the NTSB
hasn't released the final report, nor have I seen any specific information
about the climb they executed. Do you actually have a reference for your
statement, or are you just guessing?

Pete

Well, the idea behind this theory is this. Engines burn fuel. Fuel
causes heat. Heat needs to be dissipated into the air (air btw, is the
only place it can ultimately go). As you climb there is less air. Heat
that was made with the more dense air some time ago needs to be
dissipated by less dense air now. Less dense air cannot dissipate as
much heat. Get the picture? We see steady state example of this in
overheating turbocharged piston engines that can be pushed too hard at
altitude. This climbing one is a little more complicated because it
involves changing air density, but same basic idea. The heat collects
in the engine. The cooling is designed for air density only so much
less than the air density that made the heat. Exceed that and you
overheat. The overheated engines seized. Climb at the rate the engine
is designed for and this wont happen. Could only climb that fast
because they were empty.

It's just a theory so far as what CAUSED the accident, but this
behavior is well known.

Heat that was made with the
more dense air some time ago needs to be
dissipated by less dense air now. [...]

The cooling is designed for air density only so much
less than the air density that made the heat.

I didn't realize that heat remembered how it was made.

Jose
--
"Never trust anything that can think for itself, if you can't see where
it keeps its brain."
(chapter 10 of book 3 - Harry Potter).
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