Va, Design Maneuvering Speed definition
Juan Browne
Does anyone remember the official definition of Va, Design Maneuvering Speed,
and the reference for the definition?
Thanks JB
Ron Kerlin
Juan...The official definition of Va is the maximum speed at which
maximum deflection of the controls or gust loading will not exceed
design load limits. (3.6g for normal category) This definition is found
in the Flight Training Handbook, pg. 325.
From a practical standpoint, Va is, perhaps, the single most important
number to know for any aircraft, at least if one wants to avoid
structural failure. It is calculated by taking the square root of the
design load factor times the one g stall speed of the aircraft. One can
easily calculate a Va for any standard category airplane by simply
multiplying the stall speed (flaps up) times 2 and subtracting 10. This
is a conservative speed slightly less than the "real" one and will
provide a bit of a margin for wear and tear.
A related bit of calculating fun is to calculate the g's pulled by a
max-deflection dive recovery at any speed. Simply divide the stall
speed into the dive speed and square the result. It's a real
eye-opener.
I hope this sheds some light on your question....
R.Kerlin, CFI-AIM
ker...@ligtel.com
Andrew M. Sarangan
In article <5jt4kf$q...@news.gv.net>, Juan Browne <jbr...@gv.net> wrote:
> Does anyone remember the official definition of Va, Design Maneuvering Speed,
>and the reference for the definition?
>
I don't know about "official" definition, but my understanding is that,
Va is the airspeed that corresponds to a certain angle of attack at which any
sudden updraft or turbulence will stall the wings before exceeding its load
factor limits.
A heavier airplane will fly faster at that angle attack than a lighter
airplane. Therefore, Va changes with how loaded your airplane is. Contrary
to intuitive reasoning, a heavier airplane can be flown faster into a
turbulence than a lighter airplane, ie., Va increases with weight. May be
not by much to make a practical difference, but in theory it does. What
stays constant is the angle of attack that corresponds to these airspeeds.
William L. Bahn
I'm interested in where your 'formulas' come from. I'm not saying they're
wrong, I have no idea. But, as stated, I can't see any intrinsic reason for
their validity. Also, there might be some problems with dimensional
consistency.
> From a practical standpoint, Va is, perhaps, the single most important
> number to know for any aircraft, at least if one wants to avoid
> structural failure. It is calculated by taking the square root of the
> design load factor times the one g stall speed of the aircraft.
Since a stall at one g does not imply full deflection of the controls, I
don't see any intrinsic relationship between Va and the 1g stall speed. Are
you saying that airplane designers limit control travel so that this
relationship is maintained?
I'm assuming that by design load factor, you mean the coefficient of g?
(i.e., the design load limit divided by the acceleration due to gravity =
3.6 for normal category). That would make some sense and is certainly a
reasonable definition of 'load factor' and would allow the units to work
out.
> One can
> easily calculate a Va for any standard category airplane by simply
> multiplying the stall speed (flaps up) times 2 and subtracting 10.
What are the units on '10'? Knots (most likely), mph, meters/second?
> This
> is a conservative speed slightly less than the "real" one and will
> provide a bit of a margin for wear and tear.
>
If the units are knots, it is only conservative for flap up stall speeds
less than 100kts. I imagine that covers any airplane I'm likely to fly, but
does it cover all airplanes in the GA category?
> A related bit of calculating fun is to calculate the g's pulled by a
> max-deflection dive recovery at any speed. Simply divide the stall
> speed into the dive speed and square the result. It's a real
> eye-opener.
>
I sorta-kinda see where this relationship is coming from. Could you provide
a more detailed explanation of its origin? Thanks.
Dale L. Falk
In article <3362EB...@ligtel.com>, ker...@ligtel.com wrote:
>(3.6g for normal category)
Normal category is 3.8g
--
Dale L. Falk
Robert C. Kipp
According to Advisory Circular 61-23B (pilot's handbook of
aeronautical knowledge) design maneuvering speed is the speed at which
an airplane may be safely stalled. And as pointed out above this
relates to angle of attack, whether induced by a control movement of a
gust.
Rod Farlee
FAR 23.225(c) defines the design maneuvering speed Va.
FAR 23.423 defines the maximum maneuvering loads at Va.
FAR 23.1507 defines the operating maneuvering speed.
FAR 23.1583(a)(2) requires it be in the POH.
FAR 23 Appendix A Table 1 defines the load limits.
All these and other relevant sections in http://www.landings.com
- Rod Farlee
Rich Stowell
Formulas aside, maneuvering speed, Va, is nothing more than another
STALL SPEED!
In other words, whereas Vso is the 1-g stall speed for a given airplane,
Va is the stall speed at the airplane's design structural limit: Va is
the 3.8-g stall speed in the Normal cat; the 4.4-g stall speed in the
Utility cat; the 6.0-g stall speed in the Acrobatic cat.
Vso and Va, at their respective g-loads, are but two points along the
stall curve of the V-g (or V-n) diagram. Many other airspeed/g-load
combinations can also be found that will result in a stall as well
(airspeed/g-load combos greater than Vso/1.0 are called, appropriately,
ACCELERATED STALLS).
Something to think about -- Rich
--
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~~~ Rich Stowell's ~~~~
~~~ Aviation Learning Center ~~~
~~ e-mail: rsto...@west.net ~~
~ http://www.west.net/~rstowell ~
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Hilton Goldstein
Howard Berkey wrote:
>
> Rich Stowell wrote:
> >
> > Formulas aside, maneuvering speed, Va, is nothing more than another
> > STALL SPEED!
> >
> > In other words, whereas Vso is the 1-g stall speed for a given airplane,
> > Va is the stall speed at the airplane's design structural limit: Va is
> > the 3.8-g stall speed in the Normal cat; the 4.4-g stall speed in the
> > Utility cat; the 6.0-g stall speed in the Acrobatic cat.
> >
>
> stall at before exceeding it's design structural limit. For example, if
> you are flying at or below Va in really bad weather, the aircraft will
> safely stall before a very strong wind rips it's wings off, whereas the
> same is not "guaranteed" if flying faster than Va. (Guaranteed is in
> quotes for obvious reasons.)
You want to fly quite a bit below Va before you start including the
"guaranteed" word. At Va is not safe enough.
Hilton
--
Hilton Goldstein.............................hilton@sgi.com
415-933-5254 (phone).....................(fax) 415-390-6159
M/S 1L-945, 2011 N. Shoreline Blvd, Mountain View, CA 94043
http://reality.sgi.com/hilton
"Folks, this is perfect weather for today's game. Not a
breath of air." Curt Gowdy, network sports announcer, on air
Howard Berkey
Rich Stowell wrote:
>
> Formulas aside, maneuvering speed, Va, is nothing more than another
> STALL SPEED!
>
> In other words, whereas Vso is the 1-g stall speed for a given airplane,
> Va is the stall speed at the airplane's design structural limit: Va is
> the 3.8-g stall speed in the Normal cat; the 4.4-g stall speed in the
> Utility cat; the 6.0-g stall speed in the Acrobatic cat.
>
Put another way, Va is the fastest speed that an aircraft will still
stall at before exceeding it's design structural limit. For example, if
you are flying at or below Va in really bad weather, the aircraft will
safely stall before a very strong wind rips it's wings off, whereas the
same is not "guaranteed" if flying faster than Va. (Guaranteed is in
quotes for obvious reasons.)
I always found that point interesting... one of the few times where you
damn well better hope you DO stall the wings :-)
It also makes explains the classic flight test question: Does Va go up
or down when weight is added to the plane, and why? (hint: think about
stall speeds, weight, and accelerated stalls)
-H-
Dale L. Falk
In article <5k0b6a$32...@argo.unm.edu>, sara...@unm.edu (Andrew M.
Sarangan) wrote:
>
> A heavier airplane will fly faster at that angle attack than a lighter
> airplane. Therefore, Va changes with how loaded your airplane is. Contrary
> to intuitive reasoning, a heavier airplane can be flown faster into a
> turbulence than a lighter airplane, ie., Va increases with weight. May be
> not by much to make a practical difference, but in theory it does. What
> stays constant is the angle of attack that corresponds to these airspeeds.
Actually the speed difference for different weights may be quite different.
1981 Cessna 172P
Va @ 2400 lbs ->99KIAS
Va @ 2000 lbs ->92KIAS
Va @ 1600 lbs ->82KIAS
--
Dale L. Falk
Bob Moore
In article <336670...@sgi.com>, Hilton Goldstein <hil...@sgi.com> wrote:
>Howard Berkey wrote:
>> Put another way, Va is the fastest speed that an aircraft will still
>> stall at before exceeding it's design structural limit. For example, if
>> you are flying at or below Va in really bad weather, the aircraft will
>> safely stall before a very strong wind rips it's wings off, whereas the
>> same is not "guaranteed" if flying faster than Va. (Guaranteed is in
>> quotes for obvious reasons.)
What does "bad weather" and "strong wind" have to do with Va? I believe
the criteria deals with vertical gust velocity.
>You want to fly quite a bit below Va before you start including the
>"guaranteed" word. At Va is not safe enough.
Do you have a reference for this statement? Would remaining on the
ground be safe enough?
Bob Moore
Hilton Goldstein
Now, now, let's not be sarcastic. Look in Barry Schiff's "Proficient
Pilot" books.
Jan E Brandt
>A heavier airplane will fly faster at that angle attack than a lighter
airplane. Therefore, Va changes with how loaded your airplane is. Contrary to
intuitive reasoning, a heavier airplane can be flown faster into a turbulence
than a lighter airplane, ie., Va increases with weight. May be not by much to
make a practical difference, but in theory it does.<
Va = 111 kt (2440lbs)
Va = 88 kt (1531lbs)
That's a quite remarkable function of weight.
Jan
--
Jan Brandt 10041...@compuserve.com
Stuart Law
Ron Kerlin <ker...@ligtel.com> wrote in article
<3362EB...@ligtel.com>...
> Juan Browne wrote:
> >
> > Does anyone remember the official definition of Va, Design Maneuvering
Speed,
> > and the reference for the definition?
> >
> > Thanks JB
The official definition is in the FAR's that cover design of the aircraft
.. FAR Part 23.
The rule is 23.335(c) and 23.335(d). I have enclosed them below along with
the
limit loads. It is probably more than you wanted, but that's the source.
Definitions
of terms and abbreviations are usually in FAR 1. You can download these
FAR's at the FAA's web site if interested. I got this data from the Summit
Computerized Aviation Library (credit required).
**********
§ 23.335 Design airspeeds.
Except as provided in paragraph (a)(4) of this section, the
selected design airspeeds are equivalent airspeeds (EAS).
(a) Design cruising speed, VC. For VC the following apply:
{New-96-2 Revised Feb. 9, 1996, effective March 11, 1996.}
(1) Where W/S' = wing loading at the design maximum takeoff
weight, VC (in knots) may not be less than -
(i) 33 * SQRT (W/S) (for normal, utility, and commuter
category airplanes);
(ii) 36 * SQRT (W/S) (for acrobatic category airplanes).
(2) For values of W/S more than 20, the multiplying factors may
be decreased linearly with W/S to a value of 28.6 where W/S = 100.
(3) VC need not be more than 0.9 VH at sea level.
(4) At altitudes where an MD is established, a cruising speed MC
limited by compressibility may be selected.
{Beginning of old text revised Feb. 9, 1996, effective March 11, 1996}
(1) VC (in knots) may not be less than -
(i) 33 W/S (for normal, utility, and commuter category
airplanes) {Note: According to the FAA, this should read "33 * sqrt
(W/S)...". The square root was inadvertently dropped at Amdt. 23-34. -
Ed.}; and
(ii) 36 * sqrt (W/S) (for acrobatic category airplanes).
(b) Design dive speed VD. For VD, the following apply:
(1) VD/MD may not be less than 1.25 VC/MC; and
(2) With VC min, the required minimum design cruising speed, VD
(in knots) may not be less than -
(i) 1.40 VC min (for normal and commuter category airplanes);
(ii) 1.50 VC min (for utility category airplanes); and
(iii) 1.55 VC min (for acrobatic category airplanes).
(3) For values of W/S more than 20, the multiplying factors in
paragraph (b)(2) of this section may be decreased linearly with W/S to
a value of 1.35 where W/S = 100.
(4) Compliance with paragraphs (b) (1) and (2) of this section
need not be shown if VD/MD is selected so that the minimum speed
margin between VC/MC and VD/MD is the greater of the following:
{New-96-2 Revised Feb. 9, 1996, effective March 11, 1996. Was, "...may
be used."}
(i) The speed increase resulting when, from the initial
condition of stabilized flight at VC/MC, the airplane is assumed to be
upset, flown for 20 seconds along a flight path 7.5° below the initial
path, and then pulled up with a load factor of 1.5 (0.5 g acceleration
increment). At least 75 percent maximum continuous power for
reciprocating engines, and maximum cruising power for turbines, or, if
less, the power required for VC/MC for both kinds of engines, must be
assumed until the pullup is initiated, at which point power reduction
and pilot controlled drag devices may be used; and either -
{New-96-2 Revised Feb. 9, 1996, effective March 11, 1996. Was, "Mach
0.05 (at altitudes where an MD is established)."}
(ii) Mach 0.05 for normal, utility, and acrobatic category
airplanes (at altitudes where MD is established); or
{New-96-2 Added Feb. 9, 1996, effective March 11, 1996}
(iii) Mach 0.07 for commuter category airplanes (at altitudes
where MD is established) unless a rational analysis, including the
effects of automatic systems, is used to determine a lower margin. If
a rational analysis is used, the minimum speed margin must be enough
to provide for atmospheric variations (such as horizontal gusts), and
the penetration of jet streams or cold fronts), instrument errors,
airframe production variations, and must not be less than Mach 0.05.
(c) Design maneuvering speed VA. For VA, the following applies:
(1) VA may not be less than VS * sqrt(n) where -
(i) VS is a computed stalling speed with flaps retracted at
the design weight, normally based on the maximum airplane normal force
coefficients, C(na); and
(ii) n is the limit maneuvering load factor used in design
(2) The value of VA need not exceed the value of VC used in
design.
(d) Design speed for maximum gust intensity, VB. For VB, the
following apply:
{New-96-2 Revised Feb. 9, 1996, effective March 11, 1996}
(1) VB may not be less than the speed determined by the
intersection of the line representing the maximum positive lift, CN
MAX, and the line representing the rough air gust velocity on the gust
V-n diagram, or VS1 * SQRT (n(g)), whichever is less, where:
(i) n(g) the positive airplane gust load factor due to gust,
at speed VC (in accordance with § 23.341), and at the particular
weight under consideration; and
(ii) VS1 is the stalling speed with the flaps retracted at
the particular weight under consideration.
(2) VB need not be greater than VC.
{Beginning of old text revised Feb. 9, 1996, effective March 11, 1996}
(1) VB may not be less than the speed determined by the
intersection of the line representing the maximum positive lift C(n
max) and the line representing the rough air gust velocity on the gust
V-n diagram, or sqrt (n(g)) * VS1, whichever is less, where:
[Doc. No. 4080, 29 FR 17955, Dec. 18, 1964, as amended by Amdt.
23-7, 34 FR 13088, Aug. 13, 1969; Amdt. 23-16, 40 FR 2577, Jan. 14,
1975; Amdt. 23-34, 52 FR 1829, Jan. 15, 1987; Amdt. 23-24, 52 FR
34745, Sept. 14, 1987; Amdt. 23-48, 61 FR 5144, Feb. 9, 1996]
§ 23.337 Limit maneuvering load factors.
(a) The positive limit maneuvering load factor n may not be less
than -
{New-96-2 Revised Feb. 9, 1996, effective March 11, 1996. Was, "2.1 +
[24,000 / (W + 10,000)] for normal and commuter category airplanes,
except that n need not be more than 3.8."}
(1) 2.1 + (24,000 / (W + 10,000)) for normal and commuter
category airplanes, where W = design maximum takeoff weight, except
that n need not be more than 3.8;
(2) 4.4 for utility category airplanes; or
(3) 6.0 for acrobatic category airplanes.
(b) The negative limit maneuvering load factor may not be less than
-
(1) 0.4 times the positive load factor for the normal utility
and commuter categories; or
(2) 0.5 times the positive load factor for the acrobatic
category.
(c) Maneuvering load factors lower than those specified in this
section may be used if the airplane has design features that make it
impossible to exceed these values in flight.
[Doc. No. 4080, 29 FR 17955, Dec. 18, 1964, as amended by Amdt.
23-7, 34 FR 13088, Aug. 13, 1969; Amdt. 23-34, 52 FR 1829, Jan. 15,
1987; Amdt. 23-48, 61 FR 5144, Feb. 9, 1996]
John Lowry
Dear Juan and All:
I can only help you half way. The design maneuvering speed is the speed at
which the load factor limit level flight bank angle (74.7 degrees for
Normal category upright flaps up airplanes, 3.8 gs) is the stall speed when
banked that much. (That stall speed varies as the inverse square root of
the cosine of the bank angle.)
But I don't have a reference to it.
John.
Juan Browne <jbr...@gv.net> wrote in article <5jt4kf$q...@news.gv.net>...
Rod Farlee
Howard Berkey <hbe...@tenetwork.com> writes:
>Put another way, Va is the fastest speed that an aircraft will still
>stall at before exceeding it's design structural limit. For example, if
>you are flying at or below Va in really bad weather, the aircraft will
>safely stall before a very strong wind rips it's wings off, whereas the
>same is not "guaranteed" if flying faster than Va. (Guaranteed is in
>quotes for obvious reasons.)
Va is often confused with Vno (maximum structural cruising speed,
the bottom of the yellow arc on the airspeed indicator). Vno is the
maximum speed at which an FAA-defined wind gust will not exceed
load limits. Vno is typically faster than Va.
Also note Vb, the maximum speed at which the negative load limits
are not exceeded by full abrupt forward control movement. Vb is
typically slower than Va.
Va, Vb and Vno are defined in FAR Part 23; all are at maximum
certified gross weight and vary with the square root of weight (slower
speeds apply at lighter weights). As Rich Stowell says, they are all
stall speeds.
- Rod Farlee
Anton Verhulst
In article <336621...@west.net> rsto...@west.net writes:
>
>Formulas aside, maneuvering speed, Va, is nothing more than another
>STALL SPEED!
Stall speed at a given load factor - right! An interesting way to look at it,
thanks.
FYI, If the Va is not in your POH (or you just forgot it :-), a fairly good
*approximation* is to double your stall speed. Try it.
Tony V.
ben...@cds-inc.com
In <19970502180...@ladder01.news.aol.com>, rodf...@aol.com (Rod Farlee) writes:
[snip]
>Va, Vb and Vno are defined in FAR Part 23; all are at maximum
>certified gross weight and vary with the square root of weight (slower
>speeds apply at lighter weights). As Rich Stowell says, they are all
>stall speeds.
Why exactly is this? If the aircraft is at a lighter weight, there should be
less load placed on the airframe for a specific attitude, AOA, speed, etc. than
if the aircraft is heavier. I would think that things like Va in particular would
be higher for a lighter weight aircraft, although I understand that other factors
may come into play for things like Vno and Vne.......
Cheers,
Brad
karl gruber
At the lighter weights than gross you are no longer concerned the wings
exceeding load limits at 3.8G. They DO have lighter loading.
However, other parts of the airframe are still limited by 3.8G. Such as
the motor mounts, battery box Etc.
And since a lighter airframe has less inertia it reaches the 3.8G at a
lower airspeed.
Karl
Hilton Goldstein
For the sake of our discussion, let's make a few assumptions:
1. Our wing stalls at an AOA of 18.
2. Our aircraft's max positive G is 4.
3. If AOA changes rapidly, G forces change directly proportionally
with the AOA change (this is approximately true). For example,
if AOA is 2 and we rapidly change it to 6, we exert 3 Gs on the
airframe.
Now, let's assume we're flying along at gross at Va, say, 100 KIAS.
Because of the assumptions above, our AOA will equal 4.5; i.e. we can
experience a max of 4 Gs before our wing stalls, so 18/4 = 4.5. We need
to understand that AOA is critical to understanding the meaning and
workings of Va.
Now, we boot our CFI out the door and lose 200 lbs! If that were to
happen, our aircraft would start climbing. So to reduce this lift, we
need to reduce our AOA. Let's say we reduce our AOA to 3 degrees. But
now we could expose our airframe to 6 Gs before it stalled (see the
definition of Va); 18/3 = 6 (bad!). This is a dangerous situation. OK,
so how could we get our AOA back to the safe 4.5 degrees? We could slow
down. This would cause the wing to generate less lift and we'd need to
increase our AOA to compensate. So we slow down to, say, 90 KIAS and
increase of AOA back to 4.5. So for our hypothetical aircraft, Va at
gross = 100 KIAS, and Va at gross-200lbs = 90 KIAS. Therefore, Va is
reduced when the weight of the aircraft is reduced, and vice versa.
Hope that helps,
MRGFlyer
>
> A heavier airplane will fly faster at that angle attack than a lighter
> airplane. Therefore, Va changes with how loaded your airplane is.
How about this for an explanation? An airfoil's stall speed increases
with load factor simply because an increased angle of attack is there
inducing that load factor (the weight of the aircraft and maneuvering
load) and the critical angle of attack is reached sooner. A Cessna 172's
Va at 1600 lbs is 82, if you're flying at 85 kts and increase the angle of
attack (yank her back, steep bank, or whatever) amount x, you get 4.5 g's.
Now fill the plane up with 800 lbs of Pizza Hut's totally new $9.99 large
pizzas and do the exact same maneuver at 85 kts, the angle of attack is
already increased because of the extra load (weight) on the wings, and the
additional angle of attack required to reach 4.5 g's exceeds the critical
angle so it stalls first.
-Mike
Bruno B. Lobo
Brad,
>>Va, Vb and Vno are defined in FAR Part 23; all are at maximum
>>certified gross weight and vary with the square root of weight (slower
>>speeds apply at lighter weights). As Rich Stowell says, they are all
>>stall speeds.
>
>
>Why exactly is this? If the aircraft is at a lighter weight, there should be
>less load placed on the airframe for a specific attitude, AOA, speed, etc. than
>if the aircraft is heavier. I would think that things like Va in particular would
>be higher for a lighter weight aircraft, although I understand that other factors
>may come into play for things like Vno and Vne.......
Think of the VA limit as a guarantee that the wing will stall, and
thus unload, before breaking away from the aircraft. A lightly loaded
airplane (and thus flying at lower angles of attack at all speeds)
needs a higher G-force (at any aispeed) to stall than a more heavily
loaded one. If you want to pre-set a G limit for stalling the wing
(for instance 3.8) you need to decrease VA for the lighter situation
because in this case the lower operating AOA would otherwise allow the
wing to keep flying, unstalled, above the 3.8 limitation.
To put it another way, since the AOA of a lighter aircraft is lower,
and the seeked protection comes from the wing's stalling at some
predetermined G's, the lighter aircraft needs added protection (VA
reduction), as it would otherwise fly unstalled above the design G
limit.
Regards,
Bruno B. Lobo.
S23 00 59.7
W043 27 07.2
gaflygirl (Kristy)
Hey, remember that maneuvering speed varies with weight. Many Pilot
Operating Handbooks publish Va only at max gross weight, but if you are
flying at less than max gross, your Va is actually lower than the published
figure. To figure the Va for your aircraft's actual weight:
1. Divide your actual weight by your max gross weight. This figure should
be 1.00 or less (otherwise your actual weight is more than you max gross,
and you shouldn't be flying in the first place).
2. Take the square root of the number you calculated in Step 1.
3. Multiply the number you calculated in Step 2 by the Va published for
your aircraft at max gross weight. The result is Va for your aircraft at
its actual weight.
For example, let's say your aircraft's max gross weight is 2300 lbs, and
the published Va is 110 kias. Let's also say that, today, your
weight-and-balance shows your actual weight to be 2100 lbs.
1. Divide 2100 by 2300. The answer; 0.913 (rounded off).
2. Take the square root of 0.913. The answer: 0.9555.
3. Multiply the published Va at max gross weight (110 kias) by 0.9555.
Today's Va is 105 kias.
Hilton Goldstein <hil...@sgi.com> wrote in article
<336670...@sgi.com>...
>
> Howard Berkey wrote:
> >
> > Rich Stowell wrote:
> > >
> > > Formulas aside, maneuvering speed, Va, is nothing more than another
> > > STALL SPEED!
> > >
> > > In other words, whereas Vso is the 1-g stall speed for a given
airplane,
> > > Va is the stall speed at the airplane's design structural limit: Va
is
> > > the 3.8-g stall speed in the Normal cat; the 4.4-g stall speed in the
> > > Utility cat; the 6.0-g stall speed in the Acrobatic cat.
> > >
> >
> > Put another way, Va is the fastest speed that an aircraft will still
> > stall at before exceeding it's design structural limit. For example,
if
> > you are flying at or below Va in really bad weather, the aircraft will
> > safely stall before a very strong wind rips it's wings off, whereas the
> > same is not "guaranteed" if flying faster than Va. (Guaranteed is in
> > quotes for obvious reasons.)
>
> You want to fly quite a bit below Va before you start including the
> "guaranteed" word. At Va is not safe enough.
>
Bob Webster
>>Why exactly is this? If the aircraft is at a lighter weight, there should be
>>less load placed on the airframe for a specific attitude, AOA, speed, etc. than
>>if the aircraft is heavier. I would think that things like Va in particular would
>>be higher for a lighter weight aircraft, although I understand that other factors
>>may come into play for things like Vno and Vne.......
In addition to the stall stuff, look at the Gs generated in a bounce. A
lightly loaded plane has higher Gs in the same turbulence than a heavily
loaded plane. This is easier on the wing, like you say, but conside the stress
put on the engine mounting bolts, for example. Much more. Same for some other
parts of the plane.
Curtis Suter
If Va is higher for a lighter aircraft then it'd be lower for a heavier
aircraft. So a 747's Va would be about 10 knots. I think it'd stall by
then! This was a good way for me to remember how Va works.
Bob Webster <b...@viagrafix.com> wrote in article
<5lpmmu$4...@ionews.ionet.net>...
Hilton Goldstein
Hi,
Here is something I posted a while bacK:
For the sake of our discussion, let's make a few assumptions:
1. Our wing stalls at an AOA of 18.
2. Our aircraft's max positive G is 4.
3. If AOA changes rapidly, G forces change directly proportionally
with the AOA change (this is approximately true). For example,
if AOA is 2 and we rapidly change it to 6, we exert 3 Gs on the
airframe.
Now, let's assume we're flying along at gross at Va, say, 100 KIAS.
Because of the assumptions above, our AOA will equal 4.5; i.e. we can
experience a max of 4 Gs before our wing stalls, so 18/4 = 4.5. We need
to understand that AOA is critical to understanding the meaning and
workings of Va.
Now, we boot our CFI out the door and lose 200 lbs! If that were to
happen, our aircraft would start climbing. So to reduce this lift, we
need to reduce our AOA. Let's say we reduce our AOA to 3 degrees. But
now we could expose our airframe to 6 Gs before it stalled (see the
definition of Va); 18/3 = 6 (bad!). This is a dangerous situation. OK,
so how could we get our AOA back to the safe 4.5 degrees? We could slow
down. This would cause the wing to generate less lift and we'd need to
increase our AOA to compensate. So we slow down to, say, 90 KIAS and
increase of AOA back to 4.5. So for our hypothetical aircraft, Va at
gross = 100 KIAS, and Va at gross-200lbs = 90 KIAS. Therefore, Va is
reduced when the weight of the aircraft is reduced, and vice versa.
Hope that helps,
Hilton
--
Hilton Goldstein.............................hilton@sgi.com
415-933-5254 (phone).....................(fax) 415-390-6159
M/S 1L-945, 2011 N. Shoreline Blvd, Mountain View, CA 94043
http://reality.sgi.com/hilton
"I'd far rather watch a game of chess in slow-motion than a
baseball game." - Hilton
n...@thanks.com
On 18 May 97 23:15:26 GMT, "gaflygirl (Kristy)"
<gafl...@theomramp.net> wrote:
>Hey, remember that maneuvering speed varies with weight. Many Pilot
>Operating Handbooks publish Va only at max gross weight, but if you are
>flying at less than max gross, your Va is actually lower than the published
>figure. To figure the Va for your aircraft's actual weight:
>
>1. Divide your actual weight by your max gross weight. This figure should
>be 1.00 or less (otherwise your actual weight is more than you max gross,
>and you shouldn't be flying in the first place).
>2. Take the square root of the number you calculated in Step 1.
>3. Multiply the number you calculated in Step 2 by the Va published for
>your aircraft at max gross weight. The result is Va for your aircraft at
>its actual weight.
I know.
I just put it another way (in terms of the lower VA being an
additional protection comming from meeting a new [slower] stalling
speed at lower weights) because peolple can sometimes mis-interpret
the formulas and loose grasp of what they really mean, as can be seen
in the following post fragment which I was originally replying to:
>-->Why exactly is this? If the aircraft is at a lighter weight, there should be
>-->less load placed on the airframe for a specific attitude, AOA, speed, etc. than
>-->if the aircraft is heavier. I would think that things like Va in particular would
>-->be higher for a lighter weight aircraft, although I understand that other factors
>-->may come into play for things like Vno and Vne.......
In this case the poster could probably comply with the manual and do
everything right, without really knowing what was the reasoning behind
the formula. What I tried to do, was tell him the same thing without
refferring to formulas(which are available elsewhere anyway), heeding
his own request for a more conceptual explanation.
Bob Webster
The higher-lower Va changes apply to heavy-light loading in the same plane.
But it's a good way to remember.
In article <01bc6470$a155c9c0$c2c3...@suterc.enterprise.net>, "Curtis Suter"
MRGFlyer
Correct about having to be the same plane, however Va increases with
weight.
<b...@viagrafix.com (Bob Webster)>wrote:
Steve Peltz
In article <3380B5...@sgi.com>, Hilton Goldstein <hil...@sgi.com>
wrote: >1. Our wing stalls at an AOA of 18. >2. Our aircraft's max
positive G is 4.
Actually, every time I've seen this questioned (including when I didn't
understand it), the ONLY thing that was missing was that you are trying
to avoid exceeding the max G force limit. If, instead, you think only
about the load on the wing, then you'd (naively) get the opposite result
("less load on the wings, so they won't rip off as easily") or (less
naively) an unvarying result ("same speed, same max force on wings,
regardless of weight in the fuselage").
Chris Furse
I don't think the load on a wing always reduces with reducing weight for
a given G loading. For example if the weight reduction was by burning
fuel from wing tanks there may be a reduction in the load alleviation
effect of weight carried on the wings and therfore an increase in wing
bending moment even though weight is reduced.
regards,
cjf
bru...@pobox.com
>Correct about having to be the same plane, however Va increases with
>weight.
No, it doesn't. It actually decreases with weight.
MRGFlyer
>>Correct about having to be the same plane, however Va increases with
>>weight.
>No, it doesn't. It actually decreases with weight.
Ok, let me try this again... as weight increases for a given airplane, Va
increases. There were plenty of good explanations for this already
posted.
Andrew M. Sarangan
Actually, I don't think this fact (uneven weight distribution due to fuel burn)
has anything to do with how they calculate Va. As Hilton was saying,
the curious thing is that the Va limit comes from the acceleration, not
the weight. If it were limited by the weight then Va will not change with
weight.
Hilton Goldstein
Chris Furse wrote:
> Does Va vary with weight?
> No, because it is a design speed based on the computed design weight
> stall speed.
This is wrong. BTW: There is no such thing as stall speed. You have a
'stall angle' or the critical AOA. This critical AOA does not change -
ever. At gross, with this AOA (clean), you will be able to fly level no
slower that Vs1. If you try reduce your speed, this will result in a
loss of lift. To restore this lift, you need to increase your AOA, but
this will cause you to stall - hence the determination of the Vs0 and
Vs1 'stall speeds'.
My point being, is that 'stall speed' is dependent upon the weight of
the aircraft. Therefore (according to you), so is Va.
Hilton
--
Hilton Goldstein.............................hilton@sgi.com
415-933-5254 (phone).....................(fax) 415-390-6159
M/S 1L-945, 2011 N. Shoreline Blvd, Mountain View, CA 94043
http://reality.sgi.com/hilton
80% of Americans think they're above average drivers.
Chris Furse
I suggest you re-read FAR23.335(c)
Quote:
"Va may not be LESS than Vs sqrt N"
"Vs is a COMPUTED stalling speed with flaps retracted at the design
weight...."
If the speed you calculate is less than the Flight Manual Va, by FAR
definition it is not Va. There is only one Va for a particular design
limit load.
Further, the simplified FAR23 design load criteria for conventional
single engine airplanes of 6000 lb or less maximum weight does not even
directly use stalling speed in the determination of Va min, ie:
Va min=15.0*sqrt(N1*W/S)
Where Va min is in knots,
N1 is the aircraft positive manoeuvre limit load factor,
W/S is the wing loading in lb/sq ft.
Once again if you calculate a speed which is less than this it is not Va
as defined in FAR23.
BTW at no time have I said that it is not a good idea to know at which
speed you will reach the stall at the same time as design limit G load.
This is, after all, the speed for maximum rate minimum radius turning
performance.
regards,
cjf
Chris Furse
Fair go - I didn't say anything about "uneven weight distribution" or
that changes in wing bending moments are considered in Va determination.
I made the observation that reducing weight does not necessarily mean
that the wings are under less load as indicated by some postings.
The design manoeuvre speed Va;
May not be less than Vs sqrt N.
Where Vs is a computed stalling speed with flaps retracted at the design
weight, normally based on the maximum airplane normal force coefficients
Cna.
N is the limit manoeuvreing load factor used in the design.
The value of Va need not exceed the value of Vc (design cruising speed)
used in the design.
Does Va vary with weight?
No, because it is a design speed based on the computed design weight
stall speed.
Does Vsw sqrt N vary with weight? (where Vsw is the stall speed at
weights less than the design weight).
Yes, as the weight reduces Vsw reduces.
What is this speed called?
I don't know, but by definition it is not Va.
Regards
cjf
Hilton Goldstein
Chris Furse wrote:
>
> Hilton Goldstein wrote:
> >
> > Chris Furse wrote:
> >
> > > No, because it is a design speed based on the computed design weight
> > > stall speed.
> >
So you're saying Va doesn't vary with weight. Is Va of any relevance if
I'm below gross? All texts I've ever seen say that Va varies with
weight.
FAR23.335(c) says:
(c) Design maneuvering speed VA. For VA, the following applies:
(1) VA may not be less than VS<radical>n where--
(i) VS is a computed stalling speed with flaps retracted at the
design
weight, normally based on the maximum airplane normal force
coefficients,
CNA; and
(ii) n is the limit maneuvering load factor used in design
(2) The value of VA need not exceed the value of VC used in design.
I'm certainly no aeronautical engineer, so please explain how this says
that Va does not vary with weight? Thanks,
Hilton
P.S.: I'm glad you ended this post without being as rude and sarcastic
to me as you were in the private email you sent me.
Chris Furse
Hilton Goldstein wrote:
<snip>
> So you're saying Va doesn't vary with weight. Is Va of any relevance if
> I'm below gross? All texts I've ever seen say that Va varies with
> weight.
>
> FAR23.335(c) says:
> (c) Design maneuvering speed VA. For VA, the following applies:
> (1) VA may not be less than VS<radical>n where--
> (i) VS is a computed stalling speed with flaps retracted at the
> design
> weight, normally based on the maximum airplane normal force
> coefficients,
> CNA; and
> (ii) n is the limit maneuvering load factor used in design
> (2) The value of VA need not exceed the value of VC used in design.
>
> I'm certainly no aeronautical engineer, so please explain how this says
> that Va does not vary with weight? Thanks,
>
> Hilton
> P.S.: I'm glad you ended this post without being as rude and sarcastic
> to me as you were in the private email you sent me.
> --
> Hilton Goldstein.............................hilton@sgi.com
> 415-933-5254 (phone).....................(fax) 415-390-6159
> M/S 1L-945, 2011 N. Shoreline Blvd, Mountain View, CA 94043
> http://reality.sgi.com/hilton
>
> 80% of Americans think they're above average drivers.
Let us revisit Va.
Va is the Design Manoeuvre Speed.
It is the maximum speed at which structural calculation and structural
test have shown the primary control surfaces can suddenly be moved to
the stop (in either direction) without damage (to the horizontal tail,
the vertical fin or the ailerons).
During the design stage of an aircraft the structures people decide at
what speed they want this capability (on a commuter aircraft they may
accept the minimum Va permitted, for an extremely manoeuvrable aerobatic
design the may decide on a Va around Vc or even higher).
FAR 23 shows that minimum Va can be calculated in either of two way:
(1) FAR 23.335(c) say that Va may not be less than Vs*sqrtN
where Vs is a computed stalling speed flaps retracted at the design
weight, and N is the limit load factor used in the design.
(2)Appendix A to FAR 23 permits the use of a simplified design load
critera to be used in the design of single engine aircraft of 6000 lbs
or less maximum weight. If the designer uses this method then Va min is
calculated as: Va min=15*sqrt(n1*w/s).
Where Va is in knots, N1 is the aircraft positive manouevring limit load
factor, and W/S is the wing loading in lbs/sq ft.
Up to this stage the aircraft is still on the drawing board but we have
used a computed stalling speed to calculate minimum Va. This stalling
speed may not be the one actually acheived during certification
One reason Va min is calculated using the expected flaps up stall speed
is that it would be a nonsense to calculated manoeuvre loads at a speed
below that at which the limit load can be applied.
If the designer decides to make Va=Vc then flying at the stall at Vc
will apply loads in excess of the limit load.
Now the designer has decided on the Va speed he must show the following
structural capabilities at the chosen Va.
Horizontal Tail Surfaces
(1) FAR23.423
Each horizontal tail surface must be designed for manoeuvring loads
imposed by the following conditions:
"(a)A sudden deflection of the elevator control, at Va, to (1) the
maximum upward deflection and (2) the maximum down ward deflection, as
limited by the control stops or pilot effort whichever is critical.
(b)A sudden upward deflection of the elevator, at speeds above Va
followed by a downward deflection of the elevator resulting in a
prescribed (in FAR23) combination of normal acceleration and angular
acceleration.
The conditions in this paragraph involve loads corresponding to the
loads that may occur in a "checked manoeuvre" (a manoeuvre in which the
pitching controlis suddenly displaced in one direction and then suddenly
moved in the opposite direction), the deflections and timing avoid
exceeding the the limit load factor......"
Remember that this is a design calculation exercise - followed by
structural testing. It is not part of any flight test required by
certification rules.
Also note that there is no mention of stalling at Va with fully
deflected pitch controls.
Vertical Tail Surfaces
"FAR23.441
(a) At speeds up to Va the vertical tail surfaces must be designed to
withstand the following conditions. In computing tail loads, the yawing
velocity may be assumed to be zero:
(1) With the aircraft in unaccelerated flight at zero yaw, it is assumed
that the rudder control is suddenly displaced to maximum deflection, as
limited by the control stops or by pilot limit forces.
etc'
Ailerons
"FAR23.455
(a) The ailerons must be designed for the loads to which the are
subjected-........
(2)(i) Sudden maximum displacement of the aileron control at Va.
Suitable allowances may be made for control system deflections......"
Why doesn't Va vary with weight?
(1)Because it is a structural design speed (like Vc, Vb, and Vd) used
for calculating the manoeuvre loads on the horizontal tail, vertical
fin, and ailerons. The loads are then accounted for in the stressing of
these surfaces.
(2) FAR 23.335 is quite specific in that Va may not be less than that
calculated using the design weight.
You can call any lesser speed, you calculate using a lower weight,
anything you like but by FAR definition it is not Va. It is not the
speed that the control surface manoeuvre loads were calculated from.
(3) The FAA have defined Va MINIMUM in FAR 23 (in two significantly
different ways) those definitions give you no options to use other than
the specified parameters.
The main problem here is that without the aircraft design data we have
no idea whether the aircraft was certificated to Va min FAR 23.335 or
the simplified critera. We also don't know if the Va quoted in the
manual is Va min or some higher speed. If the speed is actually FAR
23.335 Va min, then reducing speed with weight may give you "ballpark"
structural protection by stalling. I say "ballpark" because we don't
know the relationship between the "computed stall speed" used to
calculate Va min and the certificated Vs1 (flaps up, design weight). The
reduced speed is still not Va.
What people want is the equivalent of the old Vra (rough air) but it
doesn't exist in the design standards for little aircraft.
Regards,
cjf
Rick Macklem
Chris Furse (c...@fl.net.au) wrote:
[post on FAR 23 definition of Va deleted]
: What people want is the equivalent of the old Vra (rough air) but it
: doesn't exist in the design standards for little aircraft.
First off, I'd like to thank you for that last post.
It looks to me that there are two different beasts here.
1 - The Maneuvering Speed Va as defined by FAR 23
vs
2 - The "maneuvering speed" discussed in most "theory of flight for dumb
pilots" books. (I've also heard the "maneuvering speed drops with
lower gross weight" theory several times.)
I'm curious where this "maneuvering speed" came from? Is it the basic idea
that was later defined by FAR 23 as some obscure formulae for the purpose
of aircraft certification or was it an older definition out of the
predecessors of FAR 23 (CAR 3, 4?)?
Anyone have any ideas? rick
Rod Farlee
While enjoying Chris Furse's posting, I found myself musing...
Wouldn't it be neat to have an electronic airspeed indicator, which
automatically recomputed and displayed Vs0 (bottom of white arc),
Vs1 (bottom of green arc), Vno (top of green and bottom of yellow
arc). All the colored arcs would reset depending on ramp weight,
and move down during flight as fuel was burned off. Neat!
It could have two needles (no indicated, only calibrated and true), too!
And an integrated G-meter, so when we push the yoke forward and
float up in the seat, Vs0 and Vs1 would move down to zero! Yeah!
Alas, FAR 23 won't allow this, any more than recomputing the
placarded Va, even though we know aerodynamics does.
- Rod Farlee
Hilton Goldstein
Rod Farlee wrote:
>
> While enjoying Chris Furse's posting, I found myself musing...
>
> Wouldn't it be neat to have an electronic airspeed indicator, which
> automatically recomputed and displayed Vs0 (bottom of white arc),
> Vs1 (bottom of green arc), Vno (top of green and bottom of yellow
> arc). All the colored arcs would reset depending on ramp weight,
> and move down during flight as fuel was burned off. Neat!
> It could have two needles (no indicated, only calibrated and true), too!
> And an integrated G-meter, so when we push the yoke forward and
> float up in the seat, Vs0 and Vs1 would move down to zero! Yeah!
How about if we hooked up the temparature gauge and the encoding
altimeter and it also reported TAS! Katanas already have digital
temperature gauges, so it should be easy enough.
Hilton
Chris Furse
Rod Farlee wrote:
>
> While enjoying Chris Furse's posting, I found myself musing...
>
> Wouldn't it be neat to have an electronic airspeed indicator, which
> automatically recomputed and displayed Vs0 (bottom of white arc),
> Vs1 (bottom of green arc), Vno (top of green and bottom of yellow
> arc). All the colored arcs would reset depending on ramp weight,
> and move down during flight as fuel was burned off. Neat!
> It could have two needles (no indicated, only calibrated and true), too!
> And an integrated G-meter, so when we push the yoke forward and
> float up in the seat, Vs0 and Vs1 would move down to zero! Yeah!
>
> placarded Va, even though we know aerodynamics does.
> - Rod Farlee
Its been a while since I flew an A320 or B747 400 but many of the
features you would like to see in an asi are implimented in these
aircraft. The problem is to have it work properly one needs equipment
not normally found in light aircraft eg air data computers and inertial
information.
The comment I would like to make on your last paragraph is this:
FAR 23 does not require nor does it imply tha Va has anything to do with
stalling or protecting the total airframe from being overstress by
stalling first. In fact the opposite is clearly stated - there is no
regulatory upper limit on Va. If the designer has chosed Va=(say)Vc then
the stall at this speed will occur at a load greater than the limit
manoeuvre load factor.
I think that because the method of calculation of Va min people have
assumed a fixed relationship with the manoeuvring stall. This MAY occur
if the designer used Va=Va min and his computed stall speed was the same
as the speed found during flight test.
For those who are wondering about suddenly applying full elevator
deflection at a speed which will allow the design load factor to be
exceeded I would like to say:
This is an exercise in structural engineering calculations, the aim is
to achieve maximum pitch rate acceleration and work out all the loads
that are applied to the tail. Remember that when the elevator is
deflected (say aircraft nose up) there is a down load produced, this
down load causes a rotation in pitch which effectively increases the
tail angle of attack and so reduces the total down load initially caused
by elevator deflection. At the time of maximum pitch rate acceleration
the unbalanced tail loads will be maximum. So you can see that an
iterative approach to the engineering calculations may be required.
LOADS WHICH OCCUR AFTER THE AIRCRAFT LOAD IS CALCULATED TO BE EQUAL TO
THE DESIGN MANOEUVRE LIMIT NEED NOT BE CONSIDERED.
On the point (by another poster) of the origin of Va, one finds many
airworthiness standards written in the blood of unfortunate
pilots/passengers. I don't know, but would wager that a few aircraft
lost fins, ailerons, horizontal tails during manoeuvres within the
(then) normally accepted flight envelope. The Va requirements appear to
be unchanged at least since the first issue of FAR 23 (Jan 1965).
regards,
cjf
bru...@pobox.com
On 24 May 1997 06:27:53 GMT, mrgf...@aol.com (MRGFlyer) wrote:
>>>Correct about having to be the same plane, however Va increases with
>>>weight.
>
>>No, it doesn't. It actually decreases with weight.
OOPS.. Somewhere between reading your post and eagering to answer, it
came up the other way around.
I am sorry
>
>Ok, let me try this again... as weight increases for a given airplane, Va
>increases. There were plenty of good explanations for this already
>posted.
Yes, including my own!
gaflygirl (Kristy)
VA varies with weight! Check your Flight Training Handbook, or check any
recent AFM, which lists VA at different weights. VA increases with
increases in aircraft weight, and decreases with reductions in aircraft
weight. In other words, the lighter you are, the quicker you'll overstress
your plane. To be more exact,
VA@givenWeight = [square root of (givenWeight / MaxGrossWeight)] X
VA@MaxGrossWeight.
Aww, why would you listen to an HTML developer who just *used* to be an
instructor? Well, here's what William Kershner writes in The Advanced
Pilot's Flight Manual:
"A new maneuvering speed is necessary for the lighter weight. Since the
overall limit ... is 3.8 Gs, the maneuvering speed must be such that that
load factor cannot be exceeded -- the airplane will stall first ..."
Here's a caption from the same book, illustrating a cartoon of an airborne
pilot who just physically lost his engine, landing gear, and horizontal
stabilizers:
"Using the maneuvering speed for max certificated weight at lighter weights
can put extra stress on the fixed-weight components."
--
Kristy McClure, HTML developer
http://appliedbus.com
http://virtualactive.com
http://virtualactive.com/owners/kristy/index.html
Hilton Goldstein <hil...@sgi.com> wrote in article
<338CFD...@sgi.com>...
> Chris Furse wrote:
> >
> > Hilton Goldstein wrote:
> > >
> > > Chris Furse wrote:
> > >
> > > > Does Va vary with weight?
> > > > No, because it is a design speed based on the computed design
weight
> > > > stall speed.
> > >
> > > This is wrong. BTW: There is no such thing as stall speed. You have
a
> > > 'stall angle' or the critical AOA. This critical AOA does not change
-
> > > ever. At gross, with this AOA (clean), you will be able to fly level
no
> > > slower that Vs1. If you try reduce your speed, this will result in a
> > > loss of lift. To restore this lift, you need to increase your AOA,
but
> > > this will cause you to stall - hence the determination of the Vs0 and
> > > Vs1 'stall speeds'.
> > >
> > > My point being, is that 'stall speed' is dependent upon the weight of
> > > the aircraft. Therefore (according to you), so is Va.
> > >
> > > Hilton
> > >
> > > --
> > > Hilton Goldstein.............................hilton@sgi.com
> > > 415-933-5254 (phone).....................(fax) 415-390-6159
> > > M/S 1L-945, 2011 N. Shoreline Blvd, Mountain View, CA 94043
> > > http://reality.sgi.com/hilton
> > >
> > > 80% of Americans think they're above average drivers.
> >
> > I suggest you re-read FAR23.335(c)
> > Quote:
> > "Va may not be LESS than Vs sqrt N"
> > "Vs is a COMPUTED stalling speed with flaps retracted at the design
> > weight...."
> > If the speed you calculate is less than the Flight Manual Va, by FAR
> > definition it is not Va. There is only one Va for a particular design
> > limit load.
> > Further, the simplified FAR23 design load criteria for conventional
> > single engine airplanes of 6000 lb or less maximum weight does not even
> > directly use stalling speed in the determination of Va min, ie:
> > Va min=15.0*sqrt(N1*W/S)
> > Where Va min is in knots,
> > N1 is the aircraft positive manoeuvre limit load factor,
> > W/S is the wing loading in lb/sq ft.
> >
> > Once again if you calculate a speed which is less than this it is not
Va
> > as defined in FAR23.
> >
> > BTW at no time have I said that it is not a good idea to know at which
> > speed you will reach the stall at the same time as design limit G load.
> > This is, after all, the speed for maximum rate minimum radius turning
> > performance.
>
> So you're saying Va doesn't vary with weight. Is Va of any relevance if
> I'm below gross? All texts I've ever seen say that Va varies with
> weight.
>
> FAR23.335(c) says:
> (c) Design maneuvering speed VA. For VA, the following applies:
> (1) VA may not be less than VS<radical>n where--
> (i) VS is a computed stalling speed with flaps retracted at the
> design
> weight, normally based on the maximum airplane normal force
> coefficients,
> CNA; and
> (ii) n is the limit maneuvering load factor used in design
> (2) The value of VA need not exceed the value of VC used in design.
>
> I'm certainly no aeronautical engineer, so please explain how this says
> that Va does not vary with weight? Thanks,
>
> Hilton
> P.S.: I'm glad you ended this post without being as rude and sarcastic
> to me as you were in the private email you sent me.
clc6...@ucmo.edu
My question, to anyone who knows what the answer is to the following;
7 ways-for an aircraft to come into contact with the ground.
If you could explain this in detail steps for me.
I may not get a chance to get back on to this site so, if you could just e-mail the answer to me/
My e-mail is as follows:
cl1...@yahoo.com
Thank You,
C.L.