Rolling a Non Aerobat 150

Oh I dunno, it's pretty easy to reach -2G in a poorly done slow roll. You
let the nose drop a bit during knife edge flight, and then push a little too
aggressively to keep the nose up as you come over into inverted, and you'll
be pushing -2G easily. I've done it plenty of times in a Decathlon when I
was rusty.

You're probably right about the positive G's. Loops and other standard
aerobatic maneuvers can normally be done at +3.5G easily, and the difference
between 3.5 and 4.4 is more than most folks would think. The only time I
normally exceed 4.5 in my Decathlon is when I hold a straight downline with
full power and then then pull hard to level.

But then all this presupposes that the pilot knows what he is doing. Sure,
an experienced acro pilot could fly basic maneuvers in a C150 and not be at
serious risk. But a novice who watched it on TV or got some hangar flying
lessons could still easily kill himself trying it. He tries a slow roll,
panics when the engine burbles while inverted, and tries to Split S out of
it. Those wings are coming off.


The older C150s are rated at +4.4 / -1.76 g and you'd be pushing to get
anywhere over either number

On 17 May 2005 09:12:43 -0700, "Robert M. Gary"
wrote in .com::

Ever see those things on T.V. when they put the fighter pilots in the G
simulator by spinning them around in a circle. If you sat in the middle
of that machine you would feel no G's (just like the cockpit of the
airplane) but the guy out at the end of the arm (or wing tip) sure
feels some G's.

-Robert


While the rolling aircraft was inverted, wouldn't any centrifugal
force generated act against (rather than add to)any negative G forces
the wing may feel?

There doesn't have to be any neg G's in the aileron roll. It depends on
how high you start your pitch attitude and how slow the plane rolls. In
the Decathlon I'd just pitch up 30 degrees and throw the stick to the
left. At the end I was mostly zero pitch and never had to put any neg
Gs in (although you can if you'd like). A C-150 probably rolls slower
any may require less than 1 G (say 0.5 Gs) to prevent excessive nose
down, I'm not sure.

-Robert

On 17 May 2005 11:52:41 -0700, "Robert M. Gary"
wrote in .com::

There doesn't have to be any neg G's in the aileron roll.

Right.

I was just pondering if the (probably miniscule) centrifugal force add
to or subtracted from any negative G that might occur in a roll.

On Mon, 16 May 2005 at 19:08:12 in message
.com, george
wrote:

Me too. This should be interesting. Different parts of the same a/c
accelerating at different speeds.
Hey look the wing's formating with us .............

Depends what you are doing. A steady roll rate at positive 'g' overall
will reduce the AoA of one wing and increase that of the other. Thus
reducing the load on one wing and increasing it on the other. If the
aircraft as whole is flying at zero 'g' then the wing loads will be
substantially the same but in different directions relative to the wing
section

However if you have a roll acceleration (Degrees per second per second)
then there will be a different 'g' acceleration at the wing tips from
the roots..

However just noting the 'g' in that case is not a good guide to finding
the forces on the structure.

Cross posting reduced to rec.aviation.piloting,rec.aviation.student
--
David CL Francis

On Tue, 17 May 2005 at 17:00:32 in message
, B S D Chapman
wrote:

Nothing to do with that.
Not sure about 1G in the cockpit scenario, but there are separate G
limits for pure pitching verses combined rolling and pitching
manouvers.

Indeed, the 'rolling pull-out' can put extra loads on one wing.

Your lines above have something of poetry about them? :-)

Cross posting reduced to rec.aviation.piloting,rec.aviation.student

--
David CL Francis

"Robert M. Gary" wrote in message
oups.com...
However, I like you're use of the word force (which is really
acceleration since God knows that F=ma).

Although acceleration is indeed proportional to force, the difference
between them is important to pilots.

* Because Va limits *acceleration*, Va becomes lower (hence more
restrictive) when the plane weighs less.

* Because Vno limits *force*, Vno is independent of the plane's weight.

--Gary

"Tauno Voipio" wrote in message
...
Matt Whiting wrote:
Robert M. Gary wrote:

Remember that F=ma. There is no force without acceleration. There is no
acceleration without force.

OK, Einstein, please explain where the acceleration is when two equal
forces are opposing each other diametrically.


The point is that there is *no* net forcce then.

Right. Matt is drawing the distinction between force(s) and net force.

Consider two objects sitting motionless on your floor. The first is being
pushed in opposite directions with the same amount of force. The second is
just sitting there.

In both cases, there is no net force and no acceleration. In the first case,
however, there are actual forces (even though there is no *net* force). In
other words, in the first case, the sum of the *absolute values* of the
forces upon the object is nonzero, even though the sum of the forces is
zero. In the second case, even the sum of the absolute values of the forces
is zero.

But in both cases, there is not only zero net acceleration, but also zero
accelerations. That is, there are no actual accelerations taking place--no
actual changes of the object's velocity (that's what acceleration is)--whose
absolute values have a nonzero sum. (Although 5-5=0, it would not be correct
to say that every motionless object has both a +5 and a -5 acceleration; we
have to distinguish the numbers in our equations from the actual physical
events they designate.)

Thus, in the first case, there are actual forces upon the object, but no
actual accelerations of the object (that is, no actual changes of the
object's velocity). Robert's claim that force "is really acceleration" isn't
correct. Forces cause (or prevent) accelerations, but it's important to
distinguish a cause from its effect.

This might all be pedantic in the context of aviation, except that (as
pointed out earlier) it's actually important for pilots to understand the
difference between Va (which limits acceleration) and Vno (which limits
force) in order to understand why Va changes with the plane's weight,
whereas Vno doesn't.

--Gary

Rod wrote:
I don't necessarily think that omitting spins from the PTS is the best
move the FAA has made, but I don't know the whole story.

They had more people killed in spin training than were preventyed by the
training.


Then they were done wrong. Started out too low?

I've had one inadvertant spin in my entire flying career... back when I was
doing slow flight while working on my commercial license. The air wasn't
particlarly smooth and a wing dropped. I picked it up with rudder and
immediately snapped over into a spin. Fortunately, I'd had spin training when
finishing up my private license and once you've seen that sight picture once,
you remember it for life. I instantly knew what had happened, what to do, and
then did it. I doubt we made more than half a turn.

My instructor was shaken up though: "Let's call it a day." I guess he was one
of those "new generation" instructors who never did much with spins. It sure
showed.



--
Mortimer Schnerd, RN

VE

I was doing some training with my CFI (aka my Dad over the weekend
for power-on stalls in a Cherokee 140. Not having much experience with
power-on stalls, I was surprised at how easily that plane would spin.
We were not trying to spin, but the stall was violent enough that we did
drop a wing and were in the entry to a spin as he recovered very
quickly. Considering the most likely spot for a power-on stall is just
after takeoff, I want that spin training (which we're going to do in a
C150).

As for the people getting killed in spin training, I concur with
Mortimer. They didn't start high enough. The PTS specifically states
for stalls (and I would expect this to apply to spins) that recovery
must be completed before reaching 1500' AGL. We start our power-on
stall training at 5000' MSL (4800' AGL) because of the threat of spins.
I'm SURE we will follow that same altitude rule for spin training.
Btw, our lowest altitude after /all/ of the stall practice was at least
4500' MSL (4300' AGL).

Chris


Mortimer Schnerd, RN wrote:
Rod wrote:

I don't necessarily think that omitting spins from the PTS is the best
move the FAA has made, but I don't know the whole story.

They had more people killed in spin training than were preventyed by the
training.



Then they were done wrong. Started out too low?

I've had one inadvertant spin in my entire flying career... back when I was
doing slow flight while working on my commercial license. The air wasn't
particlarly smooth and a wing dropped. I picked it up with rudder and
immediately snapped over into a spin. Fortunately, I'd had spin training when
finishing up my private license and once you've seen that sight picture once,
you remember it for life. I instantly knew what had happened, what to do, and
then did it. I doubt we made more than half a turn.

My instructor was shaken up though: "Let's call it a day." I guess he was one
of those "new generation" instructors who never did much with spins. It sure
showed.