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.

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.

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.

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.)

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?

"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/

"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

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

"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/

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

"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/

On Thu, 08 Jan 2004 21:52:48 GMT, Orval Fairbairn
wrote:

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.

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.

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.)

Even then there is no gurantee there will be no damage from a vertical
gust exceeding 30 fps, or that is the figure used for Bonanzas. Va,
30 fps = a 4 to a 4 1/2 G load which is the load limit for the utility
category. A vertical gust greater than 30 fps at Va would give a
greater load.

If need be I can quote/copy the paragraph right out of the ABS Pilot
Proficency Training Manual.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com