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View Full Version : Maneuvering Speed - What does this mean to a pilot?


Faster
10th Feb 2010, 21:10
Most everybody (here) knows the definition of Va - Maneuvering Speed:

Skip the following Paragraph......
In aviation, maneuvering speed is the highest speed at which full deflection of the controls about any one axis are guaranteed not to overstress the airframe. At or below this speed, the controls may be moved to their limits. Above this speed, moving the controls to their limits may overstress the airframe and potentially cause a structural failure.

The question with which I am hoping to gain insight, was posed to me during an interview for a pilots position for which I am applying. I was asked "as a pilot, what does maneuvering speed mean to you? What comes to mind? Why is this speed so important it is required to be posted on the flight deck."

I gave the definition, related what I have learned with regard to UAL Flt 587......But I sense I may have missed the mark.

Why is maneurving speed so important so as to be required to be posted on the flight deck?

Thanks

Intruder
11th Feb 2010, 01:54
The paragraph you cite is very misleading...

Maneuvering speed is the speed below which the airplane will stall before reaching the G limit. However, in any regime, rapid control reversals may impose loads beyond design loads, and extremely rapid control input may do the same. The wing spars may not break, but control surfaces and attachment points may fail...

john_tullamarine
11th Feb 2010, 02:15
of the controls about any one axis

Change that to read something like -

.. one full input of any single control in isolation followed by relaxation of the input ...

and the intent is OK.

This covers

(a) the (usual) case where pitching is limiting and structural limit load (maximum load without something bending to the point of stretching or breaking). In this situation, accelerated stall occurs at the limit load factor.

(b) the case where pitching is not the limiting case. For instance, as I recall, the HS125 Va was rudder input limiting. Stretching the memory I vaguely recall that the problem was a yaw divergence instability.

(c) .. and don't play an organ tune on the pedals ...

extremely rapid control input may do the same

Probably not for most aircraft but certainly a potential pitching problem in aircraft with very high pitch rate capability where a vortex can be established on top of the wing with a significant overshoot of the normal stall angle.

galaxy flyer
11th Feb 2010, 02:30
Stress on "one" control--rolling G's, as in a rolling upset recovery can be VERY hard on the airframe. Some fighters are quite restrictive on rolling G's, esp. with external stores. Transport category aircraft, while the limits are not published in the AFM, can experience all sorts of damage under multiple axis loads. Think APU mounts breaking, underslung engines slung, gear uplocks broken. All have happened.

GF

Intruder
11th Feb 2010, 03:33
extremely rapid control input may do the same

Probably not for most aircraft but certainly a potential pitching problem in aircraft with very high pitch rate capability where a vortex can be established on top of the wing with a significant overshoot of the normal stall angle.
When things don't break, the alternative may be an out-of-control flight mode that is totally foreign to the pilot, and may in fact qualify him for a Guinness Book "first"...

Take, for example, the old T-2C Buckeye USNavy trainer jet. It was so docile in stall/spin manners that it was used for out-of-control training for ALL Navy tactical jets. Virtually ANY spin recovery procedure from ANY airplane could be used to get out of a spin in the T-2.

To illustrate "the alternative" created by rapid control reversals, the T-2 did a VERY nice Lumczovak (sp?) -- an inverted, 3-axis, autorotation [spin]. Combine a rudder triplet (rapid full reversal with another one added) near stall speed with cross-controlled stick, and away you go! In that airplane it was recoverable IF the pilot had enough sense to apply recovery controls; in other airplanes, recovery may not be possible...

So, maneuvering speed USUALLY keeps you from breaking the airplane, but ONLY IF you keep it flying as well!

Oktas8
11th Feb 2010, 04:49
The Va definition with which I'm familiar uses the term "full and abrupt" control movement. This implies that the aircraft actually is protected from extremely rapid (not repeated) control inputs. (Light civil aircraft experience only.)

stressmerchant
11th Feb 2010, 05:54
In aviation, maneuvering speed is the highest speed at which full deflection of the controls about any one axis are guaranteed not to overstress the airframe.
I often worry about this particular definition. If you refer to FAA Advisory Circular 23-19, paragraph 48, it clearly warns:
"VA should not be interpreted as a speed that would permit the pilot unrestricted flight-control movement without exceeding aircraft structural limts"

VA is used to design the empennage and ailerons.

A speed known as "operating speed" (VO), defined in FAR 23.1507 is probably closer to the average pilot's definition of maneuvering speed.

But to sow some confusion, the FAA "Pilot's Handbook of Aeronautical Knowledge" defines VA as the "maximum airspeed to which the limit load can be imposed (either by gusts or full deflection of the control surfaces) without causing structural damage". Which suggests that the people who design the aircraft and the people who fly the aircraft may not be using the same definition!