CFI oral intel

Vaughn Simon wrote:
"Robert M. Gary" wrote in message
...
On May 30, 9:00 am, "F. Baum" wrote:

I don't think a 5 hour oral is odd at all for the CFI exam. I know
some PI/DE's schedule a full day for the oral and another day for
flying. Do you really know any initial CFI oral that lasted minutes?

Mine was something less than two hours. The whole thing was probably half a
day, but that included the paperwork. (Mine was unusual in that it was with a
designee.)

Vaughn


Mine was about two hours for the oral.

--
Dudley Henriques

In rec.aviation.student Ricky wrote:
On May 29, 9:58?am, Bertie the Bunyip wrote:

gatt wrote ;

A question the examiner asked him: "You're flying cross-country
and
trimmed at 110 knots. You die, and the engine quits. At what airspeed
will the aircraft strike the ground?"

He's obviously looking at getting an answer that it will be the same
speed, but that's not correct. It probably wouldn;'t be far off it, but
the thrust line and any up or down thrust will play a big part in what
the airplane settles at after the engine dies.

Bertie

Wait, wait, wait...around 110 knots? I must be missing sumthin. Why
would the a/c hit around 110? Uhh..this commercial pilot feels really
stupid but I don't get it. My assumption is; engine quits-airplane
slows down; pilot dies, engine quits-airplane spins in but this seems
to have a bunch of "what-ifs" to it, as well.

The first two steps you mention are correct but incomplete. The real
sequence goes: engine quits, airplane slows down, airplane begins to
descend, descent causes airplane to speed up, speed decreases the descent,
airplane slows down, airplane descends more, airplane speeds up, etc.

This cycle of increasing and decreasing airspeeds coupled with slower and
faster descents is called a phugoid. It's caused by the airplane
attempting to return to the originally trimmed angle of attack and thus
original airspeed. Depending on the airplane it may continue all the way
to the ground or it may damp out beforehand.

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

In rec.aviation.student Gezellig wrote:
On Fri, 30 May 2008 01:20:04 -0500, Michael Ash wrote:

Joking aside, if your straps were loose enough that you could slump
forward, that *would* affect your CG which would in turn affect your
trimmed airspeed.

There's another issue that I just thought of that I don't think anyone has
mentioned yet, though. Won't you get into a graveyard (bad terminology for
this scenario, as you're already dead) spiral? After all, if you could
stay straight and level just by taking your hands off the controls you
wouldn't need to fear IMC with no gyroscopic instruments. So it seems that
if you start high enough, the correct answer to this question would be
whatever the terminal velocity of your fuselage is without its wings. Am I
off base here?

You fly until gassless, stall, nose down, then descend too rapidly,
striking the ground with the wings ripped off. Works for me.

You don't stall, because when the engine quits the airplane will start to
descend, maintaining approximately the original airspeed.

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

On Mon, 02 Jun 2008 23:30:12 -0500, Michael Ash
wrote:

In rec.aviation.student Gezellig wrote:
On Fri, 30 May 2008 01:20:04 -0500, Michael Ash wrote:

Joking aside, if your straps were loose enough that you could slump
forward, that *would* affect your CG which would in turn affect your
trimmed airspeed.

There's another issue that I just thought of that I don't think anyone has
mentioned yet, though. Won't you get into a graveyard (bad terminology for
this scenario, as you're already dead) spiral? After all, if you could
stay straight and level just by taking your hands off the controls you
wouldn't need to fear IMC with no gyroscopic instruments. So it seems that
if you start high enough, the correct answer to this question would be
whatever the terminal velocity of your fuselage is without its wings. Am I
off base here?

You fly until gassless, stall, nose down, then descend too rapidly,
striking the ground with the wings ripped off. Works for me.

You don't stall, because when the engine quits the airplane will start to
descend, maintaining approximately the original airspeed.

Unless the autopilot is engaged..............

In rec.aviation.student Just go look it up! wrote:
On Mon, 02 Jun 2008 23:30:12 -0500, Michael Ash
wrote:

In rec.aviation.student Gezellig wrote:
On Fri, 30 May 2008 01:20:04 -0500, Michael Ash wrote:

Joking aside, if your straps were loose enough that you could slump
forward, that *would* affect your CG which would in turn affect your
trimmed airspeed.

There's another issue that I just thought of that I don't think anyone has
mentioned yet, though. Won't you get into a graveyard (bad terminology for
this scenario, as you're already dead) spiral? After all, if you could
stay straight and level just by taking your hands off the controls you
wouldn't need to fear IMC with no gyroscopic instruments. So it seems that
if you start high enough, the correct answer to this question would be
whatever the terminal velocity of your fuselage is without its wings. Am I
off base here?

You fly until gassless, stall, nose down, then descend too rapidly,
striking the ground with the wings ripped off. Works for me.

You don't stall, because when the engine quits the airplane will start to
descend, maintaining approximately the original airspeed.

Unless the autopilot is engaged..............

The original question specified "trimmed at 110 knots" which implies that
the autopilot is not engaged.

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

Ricky wrote in news:44a0c8ff-a313-4436-9d19-
:

On May 29, 9:58*am, Bertie the Bunyip wrote:

gatt wrote ;

A question the examiner asked him: "You're flying cross-country
and
trimmed at 110 knots. You die, and the engine quits. At what
airspeed
will the aircraft strike the ground?"

He's obviously looking at getting an answer that it will be the same
speed, but that's not correct. It probably wouldn;'t be far off it,
but
the thrust line and any up or down thrust will play a big part in
what
the airplane settles at after the engine dies.

Bertie

Wait, wait, wait...around 110 knots? I must be missing sumthin. Why
would the a/c hit around 110? Uhh..this commercial pilot feels really
stupid but I don't get it. My assumption is; engine quits-airplane
slows down; pilot dies, engine quits-airplane spins in but this seems
to have a bunch of "what-ifs" to it, as well.

Ricky


Nah, its trimmed for 110 so it will tend to stay there regradless of the
power. It'll start a dive and gravity will keep it going pretty much
that speed. My point was that trim also counteracts some of the thrust
on most airplanes since the thrustline is often a compromise, so while
110 knots woudl be theoretically the right answer, in the event it would
be a bit off that.

Try it , though. Trim hands off and then close the throttle without
touching the stick and the airplane will just dive while retaining
approximately your trimmed speed.



Bertie

Michael Ash pretended :
In rec.aviation.student Gezellig wrote:
On Fri, 30 May 2008 01:20:04 -0500, Michael Ash wrote:

Joking aside, if your straps were loose enough that you could slump
forward, that *would* affect your CG which would in turn affect your
trimmed airspeed.

There's another issue that I just thought of that I don't think anyone has
mentioned yet, though. Won't you get into a graveyard (bad terminology for
this scenario, as you're already dead) spiral? After all, if you could
stay straight and level just by taking your hands off the controls you
wouldn't need to fear IMC with no gyroscopic instruments. So it seems that
if you start high enough, the correct answer to this question would be
whatever the terminal velocity of your fuselage is without its wings. Am I
off base here?

You fly until gassless, stall, nose down, then descend too rapidly,
striking the ground with the wings ripped off. Works for me.

You don't stall, because when the engine quits the airplane will start to
descend, maintaining approximately the original airspeed.

At what point do you expect to lose the wings via "the correct answer
to this question would be whatever the terminal velocity of your
fuselage is without its wings."?

In rec.aviation.student Gezellig wrote:
Michael Ash pretended :
In rec.aviation.student Gezellig wrote:
On Fri, 30 May 2008 01:20:04 -0500, Michael Ash wrote:

Joking aside, if your straps were loose enough that you could slump
forward, that *would* affect your CG which would in turn affect your
trimmed airspeed.

There's another issue that I just thought of that I don't think anyone has
mentioned yet, though. Won't you get into a graveyard (bad terminology for
this scenario, as you're already dead) spiral? After all, if you could
stay straight and level just by taking your hands off the controls you
wouldn't need to fear IMC with no gyroscopic instruments. So it seems that
if you start high enough, the correct answer to this question would be
whatever the terminal velocity of your fuselage is without its wings. Am I
off base here?

You fly until gassless, stall, nose down, then descend too rapidly,
striking the ground with the wings ripped off. Works for me.

You don't stall, because when the engine quits the airplane will start to
descend, maintaining approximately the original airspeed.

At what point do you expect to lose the wings via "the correct answer
to this question would be whatever the terminal velocity of your
fuselage is without its wings."?

If you enter a spiral dive as I surmised, the wings fall off either when
you exceed Vne or when you exceed the maximum loading the wings can
support, whichever comes first. However it would seem that whether this
happens or not will depend on the airplane in question.

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

On May 30, 6:25*pm, Dudley Henriques wrote:
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.

The positive static stability, when present, is slight. More to the
point, it is only slightly positive around the zero point. Once an
excursion in roll gets past a few degrees, the stability is negative
(for a while) and the new stability point is in a significant bank (or
non-existent).

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.

And that's the point. Dynamic stability is generally mildly negative,
and once a slight displacement from zero occurs, the restoring force
from the mild positive static stability starts a very mild oscillation
that will eventually take you outside the area of positive static
stability. Once that occurs, dynamic stability is indeed no longer
important.

Even a plane with comparatively good lateral stability will eventually
wind up in a spiral once something like turbulence disturbs it. In
some cases it won't happen - combine a very stable plane with very
smooth air, and it might fly wings level for a long time. It has
happened. Also note that the stability improves with lower weight
(this is true of the longitudinal axis as well - that's why the
allowable cg range on most light airplanes is wider at lower weights)
so we do have these stories of planes without pilots flying just fine
for hours.

I recall one particular sad incident where a Pilatus Porter dropping
jumpers lost the yoke - it literally came off in the pilot's hands.
The pilot elected to bail out (which was, IMO, the wrong call - a
plane can be landed with rudder, throttle, and trim). His parachute
malfunctioned, and the pilot died. The plane eventually ran out of
fuel and 'landed' in a field. After a few minor repairs, it was flown
out.

These things do happen, but they are the exception. Under most normal
conditions, the combination of neutral or weakly positive static
stability and negative dynamic stability in the lateral axis will
eventually put the plane into a spiral.

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.

Sure - but that source will be found in the normal turbulence found on
most days. There are also additional factors.

First off, any side-by-side airplane with only one person on board is
going to be slightly out of balance laterally. Any plane with fuel
feed from a single wing tank, or a less-than-perfect 'both' feed
(which is most of them) will develop an imbalance. So what we need to
postulate is a plane that is tandem seating with a header tank (like
an old-style Champ or maybe a Cub) and then, on a really smooth day,
it might actually stay wings level.

If the aircraft has dihedral, it has positive static lateral stability.

That's not necessarily the case. There can be other factors that
affect stability that would overcome a small amount of dihedral.
Remember that most airplanes have strong yaw stability, and that
weakens roll stability because yaw and roll are strongly coupled.

That's interesting. I never knew that. 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.

I also like the site. The particular link includes much of what I
posted, including the assertion that most light planes left to
themselves will wind up in a spiral.

Of course as you mentioned elsewhere, this isn't the sort of
discussion you would have with the average FAA ops inspector. I knew
a couple who would have appreciated it in Houston. Neither one is
still with the FAA.

Michael

Below is a very well done white paper on stability by Russel Williams
that addresses much of what we have been discussing.

The long and short of it in my opinion is that positive lateral
stability is present in GA airplanes and they will tend to recover from
the sideslip coupling. Your key point addresses potential disturbances
that can indeed exceed this recovery tendency.
I agree totally with you that such a disturbance can exceed positive
stability tendencies if strong enough.

I believe you will find this paper interesting and informational.


http--soar.wichita.edu-dspace-bitstream-10057-754-1-t05045.pdf.webloc



--
Dudley Henriques