elevator /pitch control

[John Firth]

There was a story in S&G some years ago about a ASW 20 sucessfully landed
without damage by use of flap changes; the pilot had read the manual.
Following the fatal crash of a Cessna 150/150 hp two plane, due to
a burned throughj elevator cable, two of us tow pilots experimented
with pitch trim on the Citabria. WE concluded that a good landing is possible
(one that you walk away from) with use of trim and power. No we did not
try a landing.
Here is a reason for buying a ship with aerodynamic trim, not just
a spring on the stick.

John Firth,
Ottawa

[W.J. \(Bill\) Dean \(U.K.\).]

I was told that Eric Hamill when he was on the staff of the London Club,
Dunstable once did a complete circuit in a 150hp Super Cub without touching
the stick, to see if he could. Done of course on throttle, flaps, trim and
rudder. He was very, very current at the time.

I also heard that a Booker pilot of a 180hp Super Cub found himself with no
elevator control because of a failure in the elevator circuit, and got it
down safely.

Long live the aerodynamic trim!

W.J. (Bill) Dean (U.K.).
Remove "ic" to reply.

>
> "John Firth" > wrote in message
> ...
>
> There was a story in S&G some years ago about a ASW 20 successfully landed
> without damage by use of flap changes; the pilot had read the manual.
> Following the fatal crash of a Cessna 150/150 hp two plane, due to
> a burned through elevator cable, two of us tow pilots experimented
> with pitch trim on the Citabria. We concluded that a good landing is
> possible (one that you walk away from) with use of trim and power. No we
> did not try a landing.
>
> Here is a reason for buying a ship with aerodynamic trim, not just
> a spring on the stick.
>
> John Firth,
> Ottawa
>

[Bill Daniels]

"John Firth" > wrote in message
...
> There was a story in S&G some years ago about a ASW 20 sucessfully landed
> without damage by use of flap changes; the pilot had read the manual.
> Following the fatal crash of a Cessna 150/150 hp two plane, due to
> a burned throughj elevator cable, two of us tow pilots experimented
> with pitch trim on the Citabria. WE concluded that a good landing is
possible
> (one that you walk away from) with use of trim and power. No we did not
> try a landing.
> Here is a reason for buying a ship with aerodynamic trim, not just
> a spring on the stick.
>
> John Firth,
> Ottawa

Here's a story related to me by a jump pilot at a skydiver school. The
aircraft of choice in those days was a Howard DGA (Damn Good Airplane), a
single engine cabin monoplane powered by a Pratt & Whitney R-985 of 450 HP.
It was never an easy airplane to land even under the best circumstances.

As the pilot approached the drop zone he slowed the aircraft in preparation
of the exit of 5 skydivers, he felt a tap on his boot and the control wheel
came out of the panel - the bolt holding the control wheel tube had fallen
out. As he looked at the detached control wheel in his hands, the jumpers
looked too - and made a hasty exit.

Alone in the airplane, he re-inserted the wheel into the hole in the panel.
As he did so he felt the nested tubes catch at the burrs around the bolt
hole where the missing bolt had been. As long as he was gentle with the
elevators and ailerons, the friction held and he had control of the
airplane.

He flew around for an hour practicing gentle flying techniques and burning
off some fuel. The owner of the jump school and the Howard was on the radio
telling the pilot to just aim the old crate at an empty field and bail out.
The pilot had never been too keen on parachutes despite his job so he
insisted on a landing attempt.

Using the elevator trim for pitch control and limiting the wheel inputs he
lined up with the dirt runway. The trim proved inadequate for a full stall
landing and the DGA bounced badly collapsed the gear and bending the
propeller - but he walked away. The Howard was re-built and returned to
service.

Bill Daniels

Bill Daniels

[Andreas Maurer]

On 4 Nov 2003 16:49:14 GMT, (John Firth)
wrote:

>Here is a reason for buying a ship with aerodynamic trim, not just
>a spring on the stick.

This is the cause why an elevator trim tab is required according to
JAR 23, by the way - it's a safe backup control.

Bye
Andreas

[Robert Ehrlich]

Andreas Maurer wrote:
>
> On 4 Nov 2003 16:49:14 GMT, (John Firth)
> wrote:
>
> >Here is a reason for buying a ship with aerodynamic trim, not just
> >a spring on the stick.
>
> This is the cause why an elevator trim tab is required according to
> JAR 23, by the way - it's a safe backup control.
>

But aerodynamic trim is bad in term of aerodynamic efficiency, I think
this is the reason why all modern gliders have a spring trim. Should we
always degrade the performance for a case taht should never happen. An
exeception to this bad efficiency is the system I have seen on Robin airplanes,
i.e. a balanced all moving elevator (hinge at neutral point) with a servo (anti)tab
adjusted by the trim. The drawback of this system is that the force needed
to move the elevator from the trimmed position becomes huge when speed increases.

[Mark James Boyd]

In article >,
W.J. \(Bill\) Dean \(U.K.\). > wrote:
>I was told that Eric Hamill when he was on the staff of the London Club,
>Dunstable once did a complete circuit in a 150hp Super Cub without touching
>the stick, to see if he could. Done of course on throttle, flaps, trim and
>rudder. He was very, very current at the time.
>

I read about some wiring getting stuck in a 172 elevator
control and the CFI flying it to landing, so I experimented
with throttle, flaps, trim, and rudder only landings.

After three 172 flights, I and another CFI could land
without touching the elevator. A few more flights and
we could take off AND land without ever touching the
yoke or trim. The next flight we did it without
moving the seat either (weight shift for trim). Finally
we were able to takeoff and land without moving the seat,
without yoke, trim, or flaps (only using the throttle
for oscillation dampening, and the rudder for turns).

It was scary: we'd over-rotate on takeoff and have to reduce
throttle to keep the stall horn just on the edge of stall (5
knots over stall airspeed). On landing, because the trim
had to be so nose down for a "safe" takeoff, the perfect landing
was very flat (3-point). And this was only if the last oscillation
was nose down, then a touch of power to flare. Too much power and
the nose would come up again and then try to slam back
down. Too little power and we'd get a nose first arrival.



I wonder if the trim required for a survivable aerotow
would result in too much speed if not re-adjusted for
landing (in most gliders). Although putting C.G. further aft
reduces the need to retrim for landing, this creates
more radical oscillations for landing, so it's a
tough tradeoff/that might not be a good option...
From the very enlightening posts of others, it seems the
location of the tow hook and the angle of incidence
of the wing vs. horiz. stab would be important factors.
It also seems that winch is more forgiving (glider
ends up at high altitude with surprised pilot) of
no elevator than aerotow (where the glider just
pulls the towplane tail up, and then the glider
is off tow with a surprised pilot very close to
the ground).

Since the three assembled aircraft I've soloed have
easily inspectable external elevator hookups, this is a bit
academic, but I'd love to try dampening the oscillations with
spoilers, and then try it using rudder only. Very interesting
and perfectly suited to that calm winter air :-)