Bład pilota - power plant stall

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Bład pilota - power plant stall

Autor: pissonu 04.09.09, 18:50
To nie ptaki sa winne, a bardzo powazny bład pilota.

Bład pilota spowodował zjawisko tak zwane "engine stall" .

Jest to zjawisko z powodu którego najczęściej rozbijali sie sowieccy
piloci akrobatyczni.


en.wikipedia.org/wiki/Compressor_stall

en.wikipedia.org/wiki/Stall_(flight)


Without spending a lot of time on turbine theory, you can think of a
turbojet engine as a device that takes a whole lot of air and moves
it into a small space. A turbine engine uses four main parts. One is
a compressor to draw the air in and mash a lot of it into a little
space. Another is a diffuser which takes the compressed air and
causes a pressure rise before dumping it into a burner can. The next
is the combustion chamber, which is just what it sounds like...it
serves a function somewhat like the fuel injected combustion chamber
in a piston engine where fuel and air is mixed and burned...and
finally comes the turbine section. The turbine section is where the
exhaust gasses go. The burning or burned gasses blow across the
turbine blades, which turn a shaft...which moves the compressor. So
much for turbine theory...mashing air into a small space.

Ever go through a revolving door? Ever try to go through a revolving
door as part of a crowd of people all trying to go through the door?
The door mashes up a lot of people into a little space, and the
ability of the door to admit a lot of people depends on the folks
who pass through doing so in an orderly fashion.

Imagine someone trips, or slips,or bumps into someone else. There's
a chain reaction, people slow down, people bunch up at the front of
the door. People maybe even get stuck in the door. The chain
reaction ripples back and people get shoved and pushed, and find
that they can't get through the door. If people find they get
trapped in the door they may even react violently, pushing and
shoving not inward, but back outside into the cold street. Such is a
revolving door, and such is a compressor stall.

To help many turbine engines function properly, special "bleed
valves" or "acceleration bleeds" are installed to help prevent air
from bunching up or backing up...to help air flow smoothly through
the engine. These valves are like little side doors that might open
up in the revolving door to allow extra people through...except it's
in the engine. These valves are doors or relief ports which will
allow some of the air passing through the engine to be vented off
until a good, steady flow takes place. They mostly open and close
automatically to help "unload" the engine or relieve it of some of
the air flowing through, to prevent it from backing up or...you
guessed it...stalling.

As others have indicated, a stall is nothing more than airflow
exceeding a critical angle of attack of an airfoil, and it can
happen as easily in a turbine engine full of little airfoils as it
can to a wing or rotor or propeller...a stall is a stall. A
compressor stall is more than just an issue with angle-of attack of
individual blades, however, and is a problem with the overall
airflow through the engine (particularly the compressor)...and may
stem from multiple causes ranging from a sticky acceleration bleed
to a dirty compressor to too high an engine demand with too low
airflow, too high an angle of inlet airflow, a birdstrike, or
anything else that adversely alters airflow through the engine.

That's what causes it. What it is from the cockpit is something
else. It may be bouncing needles on a cockpit indication. It may be
a low, subtle hooting noise like an asthmatic beagle begging to be
let in, or it may bellow out there like an upset walrus. It can bang
away like nobody's business and sound like shotguns going off, or
simply chug and vibrate and shake. It may be subtle, or may be
something that can't be ignored.

Something like this, though for very different causes, can take
place in the engine of your Cessna 152. This doesn't happen because
of the propeller, but for other reasons that can range from a
slipping magneto to a sudden change in engine operation. You can get
backfiring, through the induction, or afterfiring, through the
exhuast. The closest you might get in the piston engine to a
compressor stall is a backfire...which can bark out through your
engine intake and can damage your carburetor, carb air box, air
filter, or induction.




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