CFI oral intel

Michael wrote:
On May 30, 3:36 am, "Hilton" wrote:
Why? Because all posts have made the (probably) incorrect assumption that
the aircraft somehow fly wings-levels to its demise. That just won't
happen. Forget dihedral, that won't stop it going into a spiral.

You're right, of course. The only way that will happen is with
artificial stability augmentation (a single axis autopilot). With a
two axis autopilot the plane will hit at stall speed. It may or may
not be wings level, depending on the stall characteristics.

See, this is what made the question such a good one. It allows lots
of room to explore different aspects of aerodynamic stability.

Michael

I would respectfully disagree with you and Hilton on this one :-)There
should be no "of course" and no autopilot issues are involved in the
question that I can see.

The aircraft, if in trim at 110 kts will be trimmed for whatever angle
of attack is producing that airspeed. Unless there is something added to
the problem and assuming all factors normal with balance and stability
issues, what should be expected normally is a phugoid starting nose low
as the engine quits to recover the trim speed. I'm assuming no fuel
imbalance or rigging issues that could cause a bank input entry into the
problem.

So using just the aspects of the problem as presented;

Where the aircraft is along that phugoid and the exact airspeed to
expect at ground impact would depend on the altitude remaining and the
dampening properties present determining the decreasing phases of the
phugoid.

Just what is it that you are expecting to happen to cause the necessary
bank/lift imbalance to enter a nose low spiral?

--
Dudley Henriques

On Fri, 30 May 2008 12:32:00 -0400, Gezellig wrote:

On Fri, 30 May 2008 19:23:11 +0800, Stealth Pilot wrote:

I'm wondering what the significance of posting
this question is. Is it because everyone should
know the answer or because on some level it is
nonsensical?

Can't speak for gatt but the I take it for both. There are nonsensical
questions that need to be prepaered for after all its about passing a
test to get to the real learning.

NOOOO NO NO.

the whole purpose of these odd questions is that you cant prepare for
them.

however if you *understand* the aerodynamic principles and principles
of flight you can work out the answers.
never be afraid to work out the answer out aloud to them. it can show
more clearly than any other method that you understand ...or dont
understand what you've been taught.

Stealth Pilot

I see your point.

No, wait, that's your head. lol

I would think the purpose of gatt's question to be to learn the logical
sequences of thinking, of putting into practice what you have learned in
theory, when that time comes for things in air that you could rarely, if
ever, practice.

When was the last time you practiced being dead?

On Fri, 30 May 2008 19:09:52 +0800, Stealth Pilot wrote:

first question the answer is 110 knots or thereabouts. when the engine
stops the aircraft will slow, lift will reduce and the aircraft will
enter a gentle dive, as the speed stabilises with the new engine power
(gravity) the aircraft will return to its trimmed speed and the angle
of decent will adjust until the aircraft is back in trim equilibrium.

Which is how to handle a stall with the proper AOA.

second question is interesting. the two conditions will tend to cause
a stall in the opposite wing. so which is better to stall with the
inner wing first or the outer wing first?
skidding will stall the inner wing so the stall will add to the
already existing forces causing the turn so you will spin.
slipping will stall the outer wing so you will roll out of the turn
into a dive.

I think I'd rather stall in a slip.

I'd rather dance in the rain.

shrunklink.com/arly

On May 30, 2:47*pm, Dudley Henriques wrote:
Just what is it that you are expecting to happen to cause the necessary
bank/lift imbalance to enter a nose low spiral?

Well, I am expecting normal behavior for a light airplane. Most light
airplanes have approximately neutral static and weakly negative
dynamic lateral (roll) stability. Thus, if left with no pilot input,
they will eventually roll into a turn. Maintaining AOA (which the
trim will do) will result in the increased airspeed.

Now the real question is why this is the case. Airplanes could be
built with positive dynamic lateral stability, and in fact ram-air
(square) parachutes (powered and unpowered) are built that way, which
is what makes it possible for them to be flown through clouds (absent
the legalities) with no gyros at all. However, airplanes are
generally not built that way. It's been tried before, and the results
were generally unsatisfactory.

Making the airplane too stable also made it too sluggish, and because
of the yaw-roll coupling involved gave it a really nasty ride in
turbulence.

A pretty good primer on stability issues can be found he

http://selair.selkirk.bc.ca/aerodyna...ity/Page5.html

Michael

Michael wrote:
On May 30, 2:47 pm, Dudley Henriques wrote:
Just what is it that you are expecting to happen to cause the necessary
bank/lift imbalance to enter a nose low spiral?

Well, I am expecting normal behavior for a light airplane. Most light
airplanes have approximately neutral static and weakly negative
dynamic lateral (roll) stability.

I would respectfully disagree. An Extra 300, as do most high performance
aerobatic airplanes has neutral static stability, but your vanilla
Cessna or Piper with dihedral is designed with positive static stability
in mind. Even a high wing Cessna like the 190 or 195 with little
dihedral has positive static stability due to wing position.
High performance airplanes like a Pitts or Extra have neutral static
stability.
As for dynamic stability, it really isn't much of a factor in lateral
stability. The ailerons if mass balanced around the hinge line by
weight, and if comparatively free in movement, usually assure that the
pure lateral movement is heavily damped. However, cross effects in yaw
displacement can result in lateral oscillations and Dutch Roll.

I totally agree that excessive dihedral is bad. It works against good
rolling qualities and as you say, makes for an overly stable aircraft.
It's for this reason that airplanes requiring a fast roll rate like the
Extra or a fighter for example, don't have excessive dihedral.






Thus, if left with no pilot input,
they will eventually roll into a turn.

Remember, we're dealing here with a dead engine. I'm still going to
stick with the spiel :-)) that says with a light GA airplane with
positive lateral stability built in with the normal dihedral found on
such airplanes and the engine dead, we're going to need a source for an
outside the system force strong enough to offset the countering dihedral
to any roll input to initiate the roll or yaw (or coupling if you wish)
that would end up with the aircraft banked enough to counter the
dihedral correcting it back into the normal phugoid I'm expecting.


Now the real question is why this is the case. Airplanes could be
built with positive dynamic lateral stability,

If the aircraft has dihedral, it has positive static lateral stability.
I don't see dynamic lateral stability as an issue here.




and in fact ram-air
(square) parachutes (powered and unpowered) are built that way, which
is what makes it possible for them to be flown through clouds (absent
the legalities) with no gyros at all.

That's interesting. I never knew that. I knew Steve Snyder quite well. I
believe Steve had something to do with the design of the square chute. I
know he designed the sentinel as well as a thousand other things related
to parachuting. Quite a guy. I miss him. He morted in his F86 a while back.





Making the airplane too stable also made it too sluggish, and because
of the yaw-roll coupling involved gave it a really nasty ride in
turbulence.

I completely agree.

A pretty good primer on stability issues can be found he

http://selair.selkirk.bc.ca/aerodyna...ity/Page5.html

I know the site. His stuff is generally very good. I do have some very
minor issues with his presentation on a few things.
DH

Michael


--
Dudley Henriques

In rec.aviation.student Michael wrote:
On May 30, 3:36?am, "Hilton" wrote:
Why? ?Because all posts have made the (probably) incorrect assumption that
the aircraft somehow fly wings-levels to its demise. ?That just won't
happen. ?Forget dihedral, that won't stop it going into a spiral.

You're right, of course. The only way that will happen is with
artificial stability augmentation (a single axis autopilot). With a
two axis autopilot the plane will hit at stall speed. It may or may
not be wings level, depending on the stall characteristics.

See, this is what made the question such a good one. It allows lots
of room to explore different aspects of aerodynamic stability.

It's only good if the person asking the question intends this sort of
discussion, though. My mpression from the original context was that
they were searching for a single answer ("110kts") and wouldn't anticipate
this sort of varied response. If true, then that transforms it from a good
question to a bad question. It always drives me nuts when there's a
question on a test which has a "right" answer but is actually a very
complicated question with a lot of correct responses.

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

Michael Ash wrote:
In rec.aviation.student Michael wrote:
On May 30, 3:36?am, "Hilton" wrote:
Why? ?Because all posts have made the (probably) incorrect assumption that
the aircraft somehow fly wings-levels to its demise. ?That just won't
happen. ?Forget dihedral, that won't stop it going into a spiral.
You're right, of course. The only way that will happen is with
artificial stability augmentation (a single axis autopilot). With a
two axis autopilot the plane will hit at stall speed. It may or may
not be wings level, depending on the stall characteristics.

See, this is what made the question such a good one. It allows lots
of room to explore different aspects of aerodynamic stability.

It's only good if the person asking the question intends this sort of
discussion, though. My mpression from the original context was that
they were searching for a single answer ("110kts") and wouldn't anticipate
this sort of varied response. If true, then that transforms it from a good
question to a bad question. It always drives me nuts when there's a
question on a test which has a "right" answer but is actually a very
complicated question with a lot of correct responses.



Welcome to the world of the FAA :-))

--
Dudley Henriques

In rec.aviation.student Dudley Henriques wrote:
Michael Ash wrote:
It's only good if the person asking the question intends this sort of
discussion, though. My mpression from the original context was that
they were searching for a single answer ("110kts") and wouldn't anticipate
this sort of varied response. If true, then that transforms it from a good
question to a bad question. It always drives me nuts when there's a
question on a test which has a "right" answer but is actually a very
complicated question with a lot of correct responses.

Welcome to the world of the FAA :-))

Heh heh heh heh heh... you mean you noticed it too?

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

Michael Ash wrote:
In rec.aviation.student Dudley Henriques wrote:
Michael Ash wrote:
It's only good if the person asking the question intends this sort of
discussion, though. My mpression from the original context was that
they were searching for a single answer ("110kts") and wouldn't anticipate
this sort of varied response. If true, then that transforms it from a good
question to a bad question. It always drives me nuts when there's a
question on a test which has a "right" answer but is actually a very
complicated question with a lot of correct responses.
Welcome to the world of the FAA :-))

Heh heh heh heh heh... you mean you noticed it too?


If you're following this thread, Michael and Hilton are not incorrect
even though I've chosen to disagree with them on this issue.
It's a complicated question that can easily get mired down in terms,
especially as the terms apply to stability issues with aircraft.
Under certain conditions, what Michael and Hilton have said would indeed
be correct. I've simply chosen to deal with the question as my
experience with the FAA is telling me was their intent :-)

--
Dudley Henriques

In rec.aviation.student Dudley Henriques wrote:
Michael Ash wrote:
In rec.aviation.student Dudley Henriques wrote:
Michael Ash wrote:
It's only good if the person asking the question intends this sort of
discussion, though. My mpression from the original context was that
they were searching for a single answer ("110kts") and wouldn't anticipate
this sort of varied response. If true, then that transforms it from a good
question to a bad question. It always drives me nuts when there's a
question on a test which has a "right" answer but is actually a very
complicated question with a lot of correct responses.
Welcome to the world of the FAA :-))

Heh heh heh heh heh... you mean you noticed it too?

If you're following this thread, Michael and Hilton are not incorrect
even though I've chosen to disagree with them on this issue.
It's a complicated question that can easily get mired down in terms,
especially as the terms apply to stability issues with aircraft.
Under certain conditions, what Michael and Hilton have said would indeed
be correct. I've simply chosen to deal with the question as my
experience with the FAA is telling me was their intent :-)

Yeah, I get that. That's the whole trouble; there's a fairly large
universe of discussion about the topic but the question is apparently
intended to ignore most of it. Of course as you implied this isn't exactly
rare.

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