Vne, Va and lift?

In article ,
Robert Moore wrote:

Orval Fairbairn wrote
In the case of the firefighting plane, if it was flying level and
dropped a large weight (slurry), the wings would have the same load,
either with or without the dropped weight. Other airframe components,
such as engine mounts, fixed equipment, crew, however, would
experience a sudden increase in G loading. If the plane was flying at
too high speed, sudden updrafts/gusts could overload the wings.

Say What!!

You may know what you are trying to say, but it sure didn't come out
making sense.

From Wikipedia:
The g-force experienced by an object is its acceleration relative to
free-fall. The term g-force is considered a misnomer, as g-force is not
a force but an acceleration.

You probably meant to say "wings would have the same LOAD FACTOR".
Clearly, the load supported by the wing of a loaded aircraft is more
than the wing loading of an empty aircraft even though both are
experiencing only 1g. If the pilot doesn't reduce the angle of attack
(amount of lift produced by the wing)as the load is dropped, the wing
root will experience an increase in g-force. G-force is equal to the
actual lift being produced by the wing (at that angle of attack and
airspeed) divided by the weight being lifted.

From a aerodynamic viewpoint, the smart thing to do would be to push-
over (reduce the angle of attack) just as the fire retardant is
released, thereby reducing the g-force on the wing root. This, however,
tends to prevent the retardant from exiting the aircraft. What the
pilots seem to be doing is pulling up AND turning at the point of drop
and thereby making a bad situation even worse.

Bob Moore

It is a paradox here.

Structurally, a wing really doesn't care WHAT the G-force is! All the
structure is concerned about is the amount of stress on its components.
A wing carrying, say 200K#, which suddenly drops 100K# will pull 2G, but
the STRESS on the wings remains 200K#. Other components of the aircraft
will experience 2G, but the wing's stresses remain the same.

--
Remove _'s from email address to talk to me.

In article ,
"Morgans" wrote:

"Mike Ash" wrote

Makes sense to me. Seems like there are several potential explanations:
sudden flexing of the wings like I said, sudden pitch up like you said,
or simply CG changes causing increased load on the wing. Lots of ways
for this failure to occur given a weakened wing, but the idea of the
wings failing under constant load with more Gs due to less weight
doesn't seem to make sense.

It does seem counter-intuitive. I had problems with the concept when it
came to explaining max maneuvering speed.

I had it explained to me, something like this: You are cruising along at
low weight, and hit a strong upward air column, suddenly. With a light wing
loading, the strength of the updraft will make the machine move upward
rapidly, which will cause a G to register on your G meter.

Now, you take the same plane, loaded to max weight and going the same speed
as before. You hit the same updraft, but the plane has a higher wing
loading, and higher mass, but the same wing area, so it will accelerate
upwards more slowly. That will register a lower G on your meter. Same
force applied to the higher mass is equal to less acceleration, as shown in
F=MA.

Up to this point I agree with you. The more heavily loaded plane,
hitting the same updraft, will accelerate more slowly due to F=ma.

In thinking about max maneuvering speed, the more gradually you move into an
updraft, the less force will suddenly be applied, and I think another factor
comes into play in this. The same wing with a higher wing loading will not
be as efficient at creating more lift. It will slip, or "mush" through the
air more at higher wing loading.

Here I disagree. A more heavily loaded wing is just as efficient at
creating lift as a lightly loaded wing.

The lift produced by a wing is dependent on factors like airspeed, angle
of attack, airfoil shape, density, etc., but it is not dependent on the
loading.

No matter what the loading, the maximum amount of lift that can be
produced at a certain airspeed is the same. In the more lightly loaded
airplane this translates to more gees, and more force on structural
members holding fixed objects, but it does *not* translate into more
force on the wings themselves. The more lightly loaded aircraft may well
experience structural failure at lower speeds than the published Va for
max gross weight but that structural failure will be in something other
than the wing spars, which by definition can take the load they're
experiencing.

I believe the same factor took place in the fire fighting airplane that
pulled the wing off. With the lighter load, the wing slipped less, and
created more lift at the lighter weight. It changed direction much more
quickly, which converts to higher G's, which broke it's wing.

I don't know. I hope to always (usually?) explain things in the least
technical way possible. That is the teacher side of me trying to make
things make sense to people who are not experts in the subject that I am
attempting to explain. It makes sense to me, but maybe I'm all wet.
Something must make it true, because that is what people say who know how to
make fancy math work as related to aeroplanes.

An explanation that's compatible with what I'm saying and that's mostly
compatible with what you're saying is that the wings were caused to
generate more lift after the airplane released its load, either because
of changes in CG or because the pilots pulled back in order to start a
climb.

--
Mike Ash
Radio Free Earth
Broadcasting from our climate-controlled studios deep inside the Moon

In article ,
says...
In article ,
"Morgans" wrote:

"Mike Ash" wrote

Makes sense to me. Seems like there are several potential explanations:
sudden flexing of the wings like I said, sudden pitch up like you said,
or simply CG changes causing increased load on the wing. Lots of ways
for this failure to occur given a weakened wing, but the idea of the
wings failing under constant load with more Gs due to less weight
doesn't seem to make sense.

It does seem counter-intuitive. I had problems with the concept when it
came to explaining max maneuvering speed.

I had it explained to me, something like this: You are cruising along at
low weight, and hit a strong upward air column, suddenly. With a light wing
loading, the strength of the updraft will make the machine move upward
rapidly, which will cause a G to register on your G meter.

Now, you take the same plane, loaded to max weight and going the same speed
as before. You hit the same updraft, but the plane has a higher wing
loading, and higher mass, but the same wing area, so it will accelerate
upwards more slowly. That will register a lower G on your meter. Same
force applied to the higher mass is equal to less acceleration, as shown in
F=MA.

Up to this point I agree with you. The more heavily loaded plane,
hitting the same updraft, will accelerate more slowly due to F=ma.

Well actually, F only equaled ma up to about 1905. Then some bright
spark discovered (when speed is reasonably relative to 299,792,458 m/s),
that mass and energy are entirely transmutable, and mass changes due to
speed - relatively speaking. OK, I'll bugger off now

--
Duncan

On Sep 13, 9:54*pm, Mike Ash wrote:
In article ,





*"Morgans" wrote:
"Mike Ash" wrote

Makes sense to me. Seems like there are several potential explanations:
sudden flexing of the wings like I said, sudden pitch up like you said,
or simply CG changes causing increased load on the wing. Lots of ways
for this failure to occur given a weakened wing, but the idea of the
wings failing under constant load with more Gs due to less weight
doesn't seem to make sense.

*It does seem counter-intuitive. *I had problems with the concept when it
came to explaining max maneuvering speed.

I had it explained to me, something like this: *You are cruising along at
low weight, and hit a strong upward air column, suddenly. *With a light wing
loading, the strength of the updraft will make the machine move upward
rapidly, which will cause a G to register on your G meter.

Now, you take the same plane, loaded to max weight and going the same speed
as before. *You hit the same updraft, but the plane has a higher wing
loading, and higher mass, but the same wing area, so it will accelerate
upwards more slowly. *That will register a lower G on your meter. *Same
force applied to the higher mass is equal to less acceleration, as shown in
F=MA.

Up to this point I agree with you. The more heavily loaded plane,
hitting the same updraft, will accelerate more slowly due to F=ma.

In thinking about max maneuvering speed, the more gradually you move into an
updraft, the less force will suddenly be applied, and I think another factor
comes into play in this. *The same wing with a higher wing loading will not
be as efficient at creating more lift. *It will slip, or "mush" through the
air more at higher wing loading.

Here I disagree. A more heavily loaded wing is just as efficient at
creating lift as a lightly loaded wing.

The lift produced by a wing is dependent on factors like airspeed, angle
of attack, airfoil shape, density, etc., but it is not dependent on the
loading.

No matter what the loading, the maximum amount of lift that can be
produced at a certain airspeed is the same. In the more lightly loaded
airplane this translates to more gees, and more force on structural
members holding fixed objects, but it does *not* translate into more
force on the wings themselves. The more lightly loaded aircraft may well
experience structural failure at lower speeds than the published Va for
max gross weight but that structural failure will be in something other
than the wing spars, which by definition can take the load they're
experiencing.

I believe the same factor took place in the fire fighting airplane that
pulled the wing off. *With the lighter load, the wing slipped less, and
created more lift at the lighter weight. *It changed direction much more
quickly, which converts to higher G's, which broke it's wing.

I don't know. *I hope to always (usually?) explain things in the least
technical way possible. *That is the teacher side of me trying to make
things make sense to people who are not experts in the subject that I am
attempting to explain. *It makes sense to me, but maybe I'm all wet.
Something must make it true, because that is what people say who know how to
make fancy math work as related to aeroplanes.

An explanation that's compatible with what I'm saying and that's mostly
compatible with what you're saying is that the wings were caused to
generate more lift after the airplane released its load, either because
of changes in CG or because the pilots pulled back in order to start a
climb.

--
Mike Ash
Radio Free Earth
Broadcasting from our climate-controlled studios deep inside the Moon- Hide quoted text -

- Show quoted text -

Mike, dropping the load would have in itself resulted in a pitchup
even if the pilots did not pull back on the yoke. It was trimmed for
flight with one load, so the AoA would have been greater than needed
without that load.When the load was dropped that trim would have
suddenly cause a pitch up, and the sudden pitchup would have suddenly
increased lift, and the bending moment on the wing spar since the
airplane could not react immediately to new upward thrust.. That's my
story and I'm sticking to it.

On Sep 13, 7:48*pm, Orval Fairbairn
wrote:
In article ,
*Robert Moore wrote:



Orval Fairbairn wrote
In the case of the firefighting plane, if it was flying level and
dropped a large weight (slurry), the wings would have the same load,
either with or without the dropped weight. Other airframe components,
such as engine mounts, fixed equipment, crew, however, would
experience a sudden increase in G loading. If the plane was flying at
too high speed, sudden updrafts/gusts could overload the wings.

Say What!!

You may know what you are trying to say, but it sure didn't come out
making sense.

From Wikipedia:
The g-force experienced by an object is its acceleration relative to
free-fall. The term g-force is considered a misnomer, as g-force is not
a force but an acceleration.

You probably meant to say "wings would have the same LOAD FACTOR".
Clearly, the load supported by the wing of a loaded aircraft is more
than the wing loading of an empty aircraft even though both are
experiencing only 1g. If the pilot doesn't reduce the angle of attack
(amount of lift produced by the wing)as the load is dropped, the wing
root will experience an increase in g-force. G-force is equal to the
actual lift being produced by the wing (at that angle of attack and
airspeed) divided by the weight being lifted.

From a aerodynamic viewpoint, the smart thing to do would be to push-
over (reduce the angle of attack) just as the fire retardant is
released, thereby reducing the g-force on the wing root. This, however,
tends to prevent the retardant from exiting the aircraft. What the
pilots seem to be doing is pulling up AND turning at the point of drop
and thereby making a bad situation even worse.

Bob Moore

It is a paradox here.

Structurally, a wing really doesn't care WHAT the G-force is! All the
structure is concerned about is the amount of stress on its components.
A wing carrying, say 200K#, which suddenly drops 100K# will pull 2G, but
the STRESS on the wings remains 200K#. Other components of the aircraft
will experience 2G, but the wing's stresses remain the same.

--
Remove _'s *from email address to talk to me.

Wouldn't there also be a torsion moment caused by the pitch up, i.e.,
the configuration of trim for level flight would create a nose/pitch
up after release, increasing AOA rapidly and 'twisting' the wings off
at the roots? The wings would actually be trying to increase AOA
ahead of the more massive fuselage.

Or, if not torsion then indeed it was more like an updraft in that the
rapid pitchup increased the AOA at such a rate as to literally 'blow'
the wings off. Picture it as an effect similar to holding your hand
outside the car window then quickly rotating it for a positive AOA.
It can quickly get away from you and give you a wrenched shoulder...
Don't mind me, I'm just thinking out loud

Here's a good article:
http://findarticles.com/p/articles/m.../?tag=untagged

In article
,
a wrote:

On Sep 13, 9:54*pm, Mike Ash wrote:
In article ,





*"Morgans" wrote:
"Mike Ash" wrote

Makes sense to me. Seems like there are several potential explanations:
sudden flexing of the wings like I said, sudden pitch up like you said,
or simply CG changes causing increased load on the wing. Lots of ways
for this failure to occur given a weakened wing, but the idea of the
wings failing under constant load with more Gs due to less weight
doesn't seem to make sense.

*It does seem counter-intuitive. *I had problems with the concept when it
came to explaining max maneuvering speed.

I had it explained to me, something like this: *You are cruising along at
low weight, and hit a strong upward air column, suddenly. *With a light
wing
loading, the strength of the updraft will make the machine move upward
rapidly, which will cause a G to register on your G meter.

Now, you take the same plane, loaded to max weight and going the same
speed
as before. *You hit the same updraft, but the plane has a higher wing
loading, and higher mass, but the same wing area, so it will accelerate
upwards more slowly. *That will register a lower G on your meter. *Same
force applied to the higher mass is equal to less acceleration, as shown
in
F=MA.

Up to this point I agree with you. The more heavily loaded plane,
hitting the same updraft, will accelerate more slowly due to F=ma.

In thinking about max maneuvering speed, the more gradually you move into
an
updraft, the less force will suddenly be applied, and I think another
factor
comes into play in this. *The same wing with a higher wing loading will
not
be as efficient at creating more lift. *It will slip, or "mush" through
the
air more at higher wing loading.

Here I disagree. A more heavily loaded wing is just as efficient at
creating lift as a lightly loaded wing.

The lift produced by a wing is dependent on factors like airspeed, angle
of attack, airfoil shape, density, etc., but it is not dependent on the
loading.

No matter what the loading, the maximum amount of lift that can be
produced at a certain airspeed is the same. In the more lightly loaded
airplane this translates to more gees, and more force on structural
members holding fixed objects, but it does *not* translate into more
force on the wings themselves. The more lightly loaded aircraft may well
experience structural failure at lower speeds than the published Va for
max gross weight but that structural failure will be in something other
than the wing spars, which by definition can take the load they're
experiencing.

I believe the same factor took place in the fire fighting airplane that
pulled the wing off. *With the lighter load, the wing slipped less, and
created more lift at the lighter weight. *It changed direction much more
quickly, which converts to higher G's, which broke it's wing.

I don't know. *I hope to always (usually?) explain things in the least
technical way possible. *That is the teacher side of me trying to make
things make sense to people who are not experts in the subject that I am
attempting to explain. *It makes sense to me, but maybe I'm all wet.
Something must make it true, because that is what people say who know how
to
make fancy math work as related to aeroplanes.

An explanation that's compatible with what I'm saying and that's mostly
compatible with what you're saying is that the wings were caused to
generate more lift after the airplane released its load, either because
of changes in CG or because the pilots pulled back in order to start a
climb.

--
Mike Ash
Radio Free Earth
Broadcasting from our climate-controlled studios deep inside the Moon- Hide
quoted text -

- Show quoted text -

Mike, dropping the load would have in itself resulted in a pitchup
even if the pilots did not pull back on the yoke. It was trimmed for
flight with one load, so the AoA would have been greater than needed
without that load.When the load was dropped that trim would have
suddenly cause a pitch up, and the sudden pitchup would have suddenly
increased lift, and the bending moment on the wing spar since the
airplane could not react immediately to new upward thrust.. That's my
story and I'm sticking to it.

Nope. The lift remained the same, but the weight changed, resulting in a
pitch up. Inertial/torsional accelerations came into play upon the pitch
up -- whether or not they played a significant factor in the accident
remains to be seen. According to what I read on the accident, the wings
failed at the central wing box, which had not been inspected according
to standard schedules. Apparently there were cracks in that section that
propagated and failed the wing.

Sudden gust/updraft loadings are fairly common in the vicinity of such
major fires and probably were the significant factor in the accident.

--
Remove _'s from email address to talk to me.

On Mon, 14 Sep 2009 15:42:06 -0400, Orval Fairbairn
wrote:


Nope. The lift remained the same, but the weight changed, resulting in a
pitch up. Inertial/torsional accelerations came into play upon the pitch
up -- whether or not they played a significant factor in the accident
remains to be seen. According to what I read on the accident, the wings
failed at the central wing box, which had not been inspected according
to standard schedules. Apparently there were cracks in that section that
propagated and failed the wing.

Sudden gust/updraft loadings are fairly common in the vicinity of such
major fires and probably were the significant factor in the accident.

now that last paragraph I could well believe.

to infer that the stresses increased because the weight being carried
reduced, I find implausible.

why are there no recordings of heavily overloaded ww2 bombers
collapsing on bomb release? didnt happen.
Stealth Pilot

On Sep 15, 8:33*am, Stealth Pilot wrote:
On Mon, 14 Sep 2009 15:42:06 -0400, Orval Fairbairn

wrote:
Nope. The lift remained the same, but the weight changed, resulting in a
pitch up. Inertial/torsional accelerations came into play upon the pitch
up -- whether or not they played a significant factor in the accident
remains to be seen. According to what I read on the accident, the wings
failed at the central wing box, which had not been inspected according
to standard schedules. Apparently there were cracks in that section that
propagated and failed the wing.

Sudden gust/updraft loadings are fairly common in the vicinity of such
major fires and probably were the significant factor in the accident.

now that last paragraph I could well believe.

to infer that the stresses increased because the weight being carried
reduced, I find implausible.

why are there no recordings of heavily overloaded ww2 bombers
collapsing on bomb release? didnt happen.
Stealth Pilot

WW2 bombers did not release all of their load at the same instant, and
they probably had better inspections than did this C130.

Look at the video, you will see the start of the pitch up when the
load is released, and in the next instant the wings are gone. You'll
have to slow down the video, but it's there.

In article ,
Stealth Pilot wrote:

On Mon, 14 Sep 2009 15:42:06 -0400, Orval Fairbairn
wrote:


Nope. The lift remained the same, but the weight changed, resulting in a
pitch up. Inertial/torsional accelerations came into play upon the pitch
up -- whether or not they played a significant factor in the accident
remains to be seen. According to what I read on the accident, the wings
failed at the central wing box, which had not been inspected according
to standard schedules. Apparently there were cracks in that section that
propagated and failed the wing.

Sudden gust/updraft loadings are fairly common in the vicinity of such
major fires and probably were the significant factor in the accident.

now that last paragraph I could well believe.

to infer that the stresses increased because the weight being carried
reduced, I find implausible.

Not in the wings themselves -- they carry the same aerodynamic load;
however, inertial/torsional loads from fixed equipment in the wings
(engines, propellers) transmit into the wing box structure with sudden
changes in G loading and attitude.

why are there no recordings of heavily overloaded ww2 bombers
collapsing on bomb release? didnt happen.
Stealth Pilot

--
Remove _'s from email address to talk to me.

"Stealth Pilot" wrote

why are there no recordings of heavily overloaded ww2 bombers
collapsing on bomb release? didnt happen.

Plus the fact that the average life of a bomber before it was destroyed was
17 missions, on many types in many theatres.

They were all practically new aircraft, in comparison to the C-130 in the
video.
--
Jim in NC