Text Box: WARBIRD NOTES #44     14 Jun 2000    (15)    
(1) Definition of torque – (Aerodynamics for Naval Aviators): “



(2) Definition of torque – (Webster): “a twisting or wrenching effect or moment exerted by a force acting at a distance on a body”.

(3) Definition of P-factor – (Aerodynamics for Naval Aviators): “ 


Torque is the reason that the left tire’s tread on a Mustang invariably wears faster than the right one.  Did’ja ever notice that?  Well, take a quick look at one the next time you see a Mustang parked at an airshow, many times you’ll find it to be so!  When I start a takeoff in a Mustang, it’s with the stick fully to the right and full right rudder before I ever add the throttle.  Initially the ailerons aren’t going to do anything but – as they start to gain effectiveness with an increase in airspeed – they’ll counteract the effects of torque. Until then the Mustang definitely will “tromp” or “twist” downwards on its left side.  That’s torque!  Also – even without wind – it’ll also want to swerve off towards the left side of the runway!  That’s P-factor, a different thing from torque.  That attempt to swerve towards the left is a common characteristic of our American-built airplanes!


I’m able to demonstrate torque in a Mustang, Corsair or airplanes like that, however I cannot in a Swift or even a T-6!  The latter two simply don’t possess adequate power to exhibit any readily noticeable amounts of "torque" effect to the student. 



Yet to write:


An abrupt change in angle-of-attack?  I.e., raising the tail during the takeoff roll.  Precession force.


Len Dolny in the back seat of a TF-51 over at STP’s Holman Field, that balked/rejected landing with the left wingtip dragging the ground.


Elevators have twice the area of the rudder; any fool can raise the tail before enough rudder is available to control yaw!  Expression out in west Texas about “getting a 90 degree change of scenery without ever moving your neck”!


Raise the tail abruptly?  Well, meb’be you deserved what you got from that rash act of yours!


In the end analysis, all the above discussion attempts to precisely define the terminology or the forces for the flight instructor to enable him to fix the correct terms in his/her student's mind.  After all is said and done, however, what we‘re really looking for here is the innate ability of the pilot to apply a copious amount of controls BEFORE needing them to keep the airplane from abruptly turning towards the left.  (Or for the Limeys in the Sea Furys, to the right!)

From the “Swift Associaton” Newsletter, Feb 02

Subject: Rudder
From: Jack Gladish <gladish@adams.net>
Hi Ed, Jack Gladish here proud owner of N3321K. My conventional gear time
here doesn't play a roll here in my question, 15000+ in just taildragger,
from Pitts to DC-3's, but something here that I'd like to bring up, I've
been flying 21K that last few days, and I'm using full right rudder, and
even had to drag a brake on takeoff... Landings are fine! I used RW 31, the
winds where 280 to 300 at 10 to 15 mph. This happened when I was raising
the tail, after a little speed was bit up, my rudder came back, but I used
a lot of right rudder during climb. Once at cruise, alls ok, a little like
my Cessna 195, it had a lot of torque, and a long fuselage...My prop is a
73-59, and I'm running a 0-300D...What do you think ED? I'm almost sure
it's just lack of rudder in a critical phase, but it doesn't hurt to
ask!!!!!!! Thanks Jack Gladish N3321K

Hmmmmmmm. The first thing that comes to mind is cable tension on the rudder
cable. Should be 70#. The thing that puzzles me is that it "comes and
goes". That would be explained though since you're having the problem in a
hi-power situation and torque enters in. You wouldn't have torque at cruise
and on landing. If the tension is off or low on the rudder cable, you would
notice it more on takeoff and in a climbing situation at hi power settings.
Another thought that comes to mind is the rudder bellcrank in the belly
being restricted by something. Pull the panel just aft of the firewall and
make sure all is the way it's supposed to be there. No obstruction or
restriction. The next thing I would check is in the aft fuselage behind the
cockpit. Open up the access and look into the tail to see if all looks
normal. If you have the bulkhead for 'carbon monoxide' installed, it
possibly could have come loose and is causing some restriction. Closing
thought, I would start with checking the rudder cable tension, but go
through the remainder of the points I mention just to make sure. I'm going
to cc this to Jim Montage and Steve Wilson and see what they might add.
Cheers...........Ed Lloyd

From: Steve Wilson <SteveWlson@aol.com>
Subject: Re: Rudder
Hi Jack (can we say that?)...
For the sake of brevity I will assume the airplane is rigged right and you
have read and heeded Ed's note.

The Swift is a peculiar animal. I have flown numerous tail draggers, and
the Swift is like none of them! Well, maybe BE-18 has similar traits. The
stock airplane has a straight engine mount, unlike some of the higher power
versions. The airplane has a rather forward CG compared to common
taildraggers of the period. If you have experience with the C-195 you know
that on takeoff, if the cowling moves 1" to the left, the tail has moved 1'
to the right! OTOH, the nose of the Swift moves dramatically in relation to
the tail. Don't get fooled though, where the nose goes, shortly thereafter
goes the tail!

Here is what I teach newcomers to the "stock" Swift on takeoff procedure.
It doesn't matter to me how much time the "student" has in tailwheel...
Line up the airplane in the center of the runway and let it roll forward a
little to center the tailwheel. With brakes off, start with the wheel
(stick) all the way back and bring power up continually to full power.
Assuming you have a steerable tailwheel you will find just application of
rudder in the desired direction will steer the airplane OK. With
non-steerable, just a small amount of brake in the desired direction will
do the same. If you run into a problem with directional control at this
point, reduce power and regroup.

As the airplane accelerates keep an eye on the airspeed. Do not release
back pressure until you see the airspeed is alive. I've seen a lot of folks
start to rotate onto the main gear way too early! One thing to remember is
the elevator authority is much more effective on the Swift than is the
rudder at low speed. Somewhere about 40-45 MPH, you need to come forward
with the stick. Not abruptly, but with authority and continual movement
until the weight is firmly on the main gear, with the tail high. I know
that several forces are at work here... Gyroscopic effect from the prop
wanting to turn 90 degrees to the direction of rotation (which means left),
transition from tailwheel steering to rudder, Left turning tendency from
the straight mount (torque). So, you will need to feed in rudder to
counteract this turning tendency. It may vary from full right rudder and
some right brake with a strong left crosswind, to nearly neutral or maybe a
touch of left rudder in a right crosswind condition. I would not choose a
takeoff with a tailwind component (if at all possible); however, given the
choice of a left or right crosswind, I would opt for one from the right.

Here is the one place I find Many/Most people get into trouble. They do NOT
get the tail up high enough. You have to get the airplane into a negative
angle of attack! There is three degrees of incidence built into the wing,
so the nose will seem very low! Plenty of weight on the main gear! This
allows the rudder to become effective (gets it up in the breeze), and
allows you to "drive" the airplane with the rudder and if necessary brakes.
If you become aware that you are not maintaining directional control,
before you do anything else, start with more forward pressure. You probably
do not have the tail up high enough. More pressure on the man gear will
allow you to use more brake (if needed) and the higher the tail will allow
more rudder authority. May seem hard to do, but a lot of Swifts have been
lost at this point. Either you are a pilot or a passenger. If directional
control is lost, you are a passenger. Use what you have working for you! An
RTO at this point is problematical at best. Not impossible, but tricky. If
you reduce the power abruptly what will happen to the rudder authority?
Where is the airplane going to want to go? It is very easy to go from
limited control, to over-control, to loss of control in the wink of an eye!

As the airplane accelerates through 60-65 MPH you can release forward
pressure and allow the airplane to transition to a positive angle of attack
and it will liftoff. I find with my airplane, I frequently use full right
rudder during the initial phase of the takeoff roll and more often than not
a little brake to keep the airplane going straight down the runway. There
is a definite difference between the 125 HP and the 145 HP at this point!
You don't have to be a test pilot to notice the difference! I suggest use
of this technique until you are completely familiar with your airplane,
then you can modify the technique to what is comfortable to your style of
takeoff; however, in the initial learning process, you will be a "happy
camper" if you go through the takeoff procedure as I describe it. This is
regardless of wind condition.

To be completely honest, I use a little different technique myself for a
takeoff with no wind/no crosswind; however, when a crosswind is present or
anytime it is gusty, I revert back to this technique. It has served me well
for 38 years...Happy Swifting! Steve Wilson




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