spoilers vs. ailerons

" wrote in message
...
Ron Natalie wrote in message
.. .
wrote:
The definition of stalled [...] is a definition based on
aircraft handling and controllability.

Says who?

The certification requirements. They do not mention in any way a specific
aoa.

They don't even define stall. What makes you think they define it based on
handling rather than AOA?

Perhaps you are confused (for example) by the wording of 23.49(a). When
they say "VSO and VS1 are the stalling speeds or the minimum steady flight
speeds, in knots (CAS), at which the airplane is controllable", that means:

"VSO and VS1 are (the stalling speeds) or (the minimum steady flight speeds,
in knots (CAS), at which the airplane is controllable)"

Or perhaps you are mistaking the FAA's requirement for how to *identify* a
stall for a definition of one. See 23.201(b). You'll note that the
requirement in 23.201(b) even applies to airplanes that don't actually stall
under the conditions described, such as the Ercoupe. The FAA is well aware
that those airplanes are not stalling.

The FAA uses the same definition for stall that everyone else does.

[...] Back to little planes. The stall varies widely, mostly
depending on weight and cg position.

True.

For example at forward cg, the stall is often determined by running out
of elevator travel.

False. Unless by "often" you mean "rarely".

The airplane isn't really stalled, but the certification requirements
say it is.

Also false. Even for the rare airplane where a forward CG means the
elevator doesn't have enough authority to create a stall, the FAA doesn't
call that situation a stall. They simply use that situation to define a
specific speed.

Don't be confused by the fact that the speed defined is often referred to as
the stall speed. It's not the stall speed, it's Vs0 and Vs1 (as
appropriate).

[...] I'm sure that I have not covered the issue well at all.

I can certainly agree with that.

It would be a good exercise pull up the certification requirements
for light aircraft and read them.

I can agree with that as well. Perhaps you should try it again, this time
reading them correctly.

[...]
One other thing. Stall speeds vary considerably with entry rate. The regs
specify a 1 knot per second entry rate. At slower entry rates, the stall
speed is higher.

So, you're saying as the entry rate approaches 0 knots per second, the stall
speed goes to infinity?

Um, seems to me you have this backwards.

[...] "There I was, turning final
above stall speed and the plane dove into the ground." Turning flight.
Slow
speed decline. It adds up.

Perhaps, but your post doesn't.

Speaking of which, maybe you could look into your whole line-lengths thing.
It is customary to either limit your line lengths to 72 characters or less,
or to not limit them at all. The former is much more common, but at least
with the latter the post is still readable in *some* newsreaders.

Pete

I said:

For example at forward cg, the stall is often determined by running out
of elevator travel.
I made an error. I should not have used the word determined.
I should have been more clear. The point is that with the elevator limited
based on the stall at aft CG, the forward cg case can be compromised.
You tend to run out of elevator which make the approach speeds
higher etc, etc.

You said:
False. Unless by "often" you mean "rarely".

I reply:
Indirectly, stall can be changed by what has happened at forward cg.
The compromises of elevator throw and cg position will change
the published speeds.
---
snips:
---
I said:
One other thing. Stall speeds vary considerably with entry rate. The regs
specify a 1 knot per second entry rate. At slower entry rates, the stall
speed is higher.

You replied:
So, you're saying as the entry rate approaches 0 knots per second, the
stall
speed goes to infinity?

Um, seems to me you have this backwards.

I reply:
I made no such inference that the stall speed grows infinitely. What I said
is correct. Try it. It's not easy to do. Count down from 10 to 1 at the same
time
you are reducing the airspeed that last 10 knots. One knot per second.
The stick input will probably be very non-linear in order to do this.
Now do the last 10 knots in 5 sec. Now do it as slowly as possible.
It takes multiple runs, since the "last" 10 knots will be redefined
depending
on the stall speed at each entry rate. The most difficult part is that last
second. That's the part that counts for data.
Touching the elevator stop, rolling off, or nose reacting in a direction
opposite
elevator input all count as stall.


Enough of this - the thread was about spoilers.

Dennis

"Matt Whiting" wrote in message ...
Mike Rapoport wrote:

Spoilers function the same as ailerons at low angles of attack and better than ailerons at high angle of attack. The
primary advantage of spoilers instead of ailerons is that it enables full span flaps. Spoilers also reduce or
eliminate adverse yaw.

I assume there must be some disadvantages of spoilers for roll control as you see them so rarely. What are the
drawbacks? Cost??

Matt


What happens when the wing is inverted? If you are pushing negative Gs then the roll control will be reversed?

" Blueskies" wrote in message
m...

"Matt Whiting" wrote in message
...
Mike Rapoport wrote:

Spoilers function the same as ailerons at low angles of attack and
better than ailerons at high angle of attack. The primary advantage of
spoilers instead of ailerons is that it enables full span flaps.
Spoilers also reduce or eliminate adverse yaw.

I assume there must be some disadvantages of spoilers for roll control as
you see them so rarely. What are the drawbacks? Cost??

Matt


What happens when the wing is inverted? If you are pushing negative Gs
then the roll control will be reversed?


It would work the same. The wing doesn't know that it is inverted, all it
knows is AOA.

Mike
MU-2

"Mike Rapoport" wrote in message hlink.net...

" Blueskies" wrote in message m...

"Matt Whiting" wrote in message ...
Mike Rapoport wrote:

Spoilers function the same as ailerons at low angles of attack and better than ailerons at high angle of attack.
The primary advantage of spoilers instead of ailerons is that it enables full span flaps. Spoilers also reduce or
eliminate adverse yaw.

I assume there must be some disadvantages of spoilers for roll control as you see them so rarely. What are the
drawbacks? Cost??

Matt


What happens when the wing is inverted? If you are pushing negative Gs then the roll control will be reversed?


It would work the same. The wing doesn't know that it is inverted, all it knows is AOA.

Mike
MU-2


The wing does know, the AOA is negative. Right side up, the spoiler is deflected and the wing drops. Turn it upside down
and deflect it, the wing still drops.

" Blueskies" wrote in message
m...

"Mike Rapoport" wrote in message
hlink.net...

" Blueskies" wrote in message
m...

"Matt Whiting" wrote in message
...
Mike Rapoport wrote:

Spoilers function the same as ailerons at low angles of attack and
better than ailerons at high angle of attack. The primary advantage of
spoilers instead of ailerons is that it enables full span flaps.
Spoilers also reduce or eliminate adverse yaw.

I assume there must be some disadvantages of spoilers for roll control
as you see them so rarely. What are the drawbacks? Cost??

Matt


What happens when the wing is inverted? If you are pushing negative Gs
then the roll control will be reversed?


It would work the same. The wing doesn't know that it is inverted, all
it knows is AOA.

Mike
MU-2


The wing does know, the AOA is negative. Right side up, the spoiler is
deflected and the wing drops. Turn it upside down and deflect it, the wing
still drops.

No. The wing is pushing the air down to keep the plane up. If the spoiler
is extended on an inverted wing, turbulence is created behind the spoiler
and air is not pushed down as effectively. Although I have never flown
inverted, I have pushed the nose over to the point of negative Gs and roll
control is not reversed.

Mike
MU-2

The first spoiler I ever saw was on the Navy's RA-5C. Found the concept
quite interesting. It's a complex system and quite pricey. The RA also
utilized full moving vertical and horizontal stabalators in lieu of
rudder and trailing vertical control surfaces on the tail of the
aircraft. The "Vigi" was years ahead of its time in design.