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#1
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Va and turbulent air penetration speed.
Kershner's "The Advanced Pilot's Flight Manual" has the following
definition for Va. Va - The maneuvering speed. This is the maxiumu speed at a particular weight at which the controls may be fully deflected without overstressing the airplane. Now, Va is commonly taught as turbulent air penetration speed. But nowhere in the definition does it say that Va will protect the airframe from damage due to turbulence. Does slowing down even slower than Va protect the airframe from even more severe turbulence? Or is Va the best speed for turbulence penetration? Or is Va just used as a turbulence air penetration speed becauase of tradition or some other non-technically correct reason. |
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#3
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Orval Fairbairn wrote in message .. .
Va is the MAXIMUM speed (at max gross weight) at which the aircraft can be stalled without exceeding its max designed load factor. The lower the gross weight, the lower the effective Va (due to engine mounts, etc.) Where does the above definition come from? |
#4
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"Doug" wrote in message
om... Orval Fairbairn wrote in message .. . Va is the MAXIMUM speed (at max gross weight) at which the aircraft can be stalled without exceeding its max designed load factor. The lower the gross weight, the lower the effective Va (due to engine mounts, etc.) Where does the above definition come from? You'll not find it anywhere, because it is incorrect. You'll find Va covered in the FAR's for part 23 certified aircraft he- http://www.access.gpo.gov/nara/cfr/c...4cfr23_00.html The relevant sections are 23.335 (where you see that Va can be *no less than* Vs*sqrt (load factor) -- which means that _it can be greater than this_, and 23.423 where its relationship to control surfaces is discussed. Short answer: Va is defined in terms of what the *control surfaces* can handle, not what the plane can handle. However, Va must be sufficiently high to satisfy 23.335, which means (oddly) that there is no regulatory requirement that stops you from flying at Va without exceeding the load factor. Well fancy that!. -- Dr. Tony Cox Citrus Controls Inc. e-mail: http://CitrusControls.com/ |
#5
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"Tony Cox" wrote in message
. net... You'll find Va covered in the FAR's for part 23 certified aircraft he- http://www.access.gpo.gov/nara/cfr/c...4cfr23_00.html The relevant sections are 23.335 (where you see that Va can be *no less than* Vs*sqrt (load factor) -- which means that _it can be greater than this_, and 23.423 where its relationship to control surfaces is discussed. Short answer: Va is defined in terms of what the *control surfaces* can handle, not what the plane can handle. However, Va must be sufficiently high to satisfy 23.335, which means (oddly) that there is no regulatory requirement that stops you from flying at Va without exceeding the load factor. Well fancy that!. Your points are excellent, but I think the issue is over terminology. The "maneuvering speed" placarded in the cockpit is not Va. It is Vo. It is defined by 23.1507 and the placard is mandated by 23.1563. "Vs is a selected speed that is not *greater* than Vsvn". My *s. At or below Vo, the criteria that are generally (and erroneously) thought to apply below Va, do apply, i.e. the wing will stall before the positive limit maneuvering load factor is exceeded. Julian Scarfe |
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I wrote in message ...
The "maneuvering speed" placarded in the cockpit is not Va. It is Vo. It is defined by 23.1507 and the placard is mandated by 23.1563. "Vs is a selected speed that is not *greater* than Vsvn". Just to clarify, Vsvn is the way that Vs*sqrt (n) pasted from the text. n is the "positive limit maneuvering load factor". Julian |
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"Julian Scarfe" wrote in message ... The "maneuvering speed" placarded in the cockpit is not Va. It is Vo. It is defined by 23.1507 and the placard is mandated by 23.1563. "Vs is a selected speed that is not *greater* than Vsvn". My *s. At or below Vo, the criteria that are generally (and erroneously) thought to apply below Va, do apply, i.e. the wing will stall before the positive limit maneuvering load factor is exceeded. Indeed. Vo was discussed in the thread in rec.aviation.piloting that I referred to earlier. As I understand it, Vo is a more recent certification requirement. Not sure then it came in, but 23.1507 is dated 1993. My 1966 182 doesn't come with a Vo. Certainly, terminology caused a lot of confusion the last time this was discussed, and I expect it will again if the thread continues! -- Dr. Tony Cox Citrus Controls Inc. e-mail: http://CitrusControls.com/ |
#8
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At or below Vo, the criteria that are generally (and erroneously)
thought to apply below Va, do apply, i.e. the wing will stall before the positive limit maneuvering load factor is exceeded. People should make sure they see the word "POSITIVE". At Vo you can pull as hard as you want without exceeding the limit load factor (3.8 for normal category), but since the limit is much lower for negative load factor (0.4 x 3.8 = 1.52) you can't push as hard as you want. Barry |
#9
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"Orval Fairbairn" wrote in message
news In article , (Doug) wrote: Kershner's "The Advanced Pilot's Flight Manual" has the following definition for Va. Va - The maneuvering speed. This is the maxiumu speed at a particular weight at which the controls may be fully deflected without overstressing the airplane. Va is the MAXIMUM speed (at max gross weight) at which the aircraft can be stalled without exceeding its max designed load factor. The lower the gross weight, the lower the effective Va (due to engine mounts, etc.) This is incorrect. In fact, *both* definitions are incorrect (with all due respect to Kershner). For planes certified under Pt 23, flying at Va *does not* guarantee that you'll stall before exceeding max design load factor, nor that you'll not overstress the airplane. I know this will be controversial & generate a lot of heat, but check out the thread "Overweight takeoff / flight" from last November in rec.aviation.piloting. I used to believe this about Va too, but it is wrong. -- Dr. Tony Cox Citrus Controls Inc. e-mail: http://CitrusControls.com/ |
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