>
>> Those aspects are true of most aircraft to some degree, Ken, but
>>particularly of prop-driven aircraft with their propellors forward
>>of the lifting surfaces.
>
>Maybe ChrisT can enlighten us on how variable the stall speeds are on
>the overblown wing of a C-130.
>
>The era is over, but I absolutely loved watching "Fat Albert" do a JATO launch.
>
On the C-130 there isn't much variability in the stall speed (except with
two engines out on one side), and the entire concept of "critical engine"
performance was never mentioned. I didn't learn about that until I got some
instruction in a Piper Aztec.
"Critical engine" refers to the difference in stall speed that occurs when
you have a situation such as an engine out on a twin, such as a B-25. The prop
does not pull you straight forward, but instead pulls slightly to one side due
to the "relative wind" on the prop blades. If you have an appreciable angle of
attack, the blade on one side will have a higher pitch than that of the other
side, so it will take a bigger bite, resulting in pulling you to one side. You
can experience this in a single-engine aircraft by flying slow and advancing
the throttle.
The result is that you end up flying slightly cross-controlled to maintain
a straight course, and the amount of cross-control will depend on which engine
is out as you will have to apply more or less cross-control depending on which
engine is out. Consequently, there are different stall speeds depending on
whether it is the left or right engine, and the one that results in the most
adverse performance is called the "critical engine". A very detailed
explanation can be found here:
https://en.wikipedia.org/wiki/Critical_engine
An interesting historical note is that the P-38 Lightning did not have a
critical engine. Since the props rotated in different directions the stall
speed was the same regardless of which engine failed. A nice concept unless
you were a mechanic faced with two different props and gearboxes.
Chris
When the going gets weird, the weird turn pro
- Hunter S. Thompson
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