Thread: My Ground Loop
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Old November 30th 05, 07:20 PM posted to rec.aviation.piloting
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Default My Ground Loop

But the big
(235hp) Pawnee at the glider club wanted to nose over if you just
breathed on the brakes.


Yeah, I remember that plane. It wasn't really a Pawnee 235 - it was a
normal Pawnee (originally 150 hp) that had been re-engined. Sure flew
nice. Landed nice too - the engine change moved the cg forward, so the
mains were only slightly ahead of cg. Very little tendency to come
around, and even at idle the prop blast from that big engine and
seaplane prop kept the rudder effective at very low speeds. Never did
use the brakes on it for anything other than holding it at runup or
bringing it to a stop from taxi speed. It's gone now - crashed due to
pilot incompetence, a total loss.

On the other hand, I remember a Starduster that couldn't be put on its
nose. You could hold the brakes, go full throttle on the IO-360 engine
with CS prop, push the stick full forward, and the tail wouldn't come
up. It wouldn't even get light. You had to be doing 45 kts at full
throttle to lift the tail. You couldn't wheel land the thing either.
Didn't matter what you did - you could touch down at 80 kts, and the
tail would drop immediately even with the stick full forward. Using
the brakes on landing was a routine thing - it was the only way. It
was also the only way to maintain directional control below 40 kts or
so - rudder was totally ineffective. Tina sold it, but I hear it's
still flying.

Different airplanes.

I did my own groundloop once, on takeoff.

Among tailwheel pilots, there are those who have and those who will.
Groundloop, that is. Put a wingtip in the dirt. Whatever you want to
call it. I always knew that, but when I changed groups, it was a
surprise. I suppose it always is.

The HP-11 is not really a tailwheel airplane. It's a tailwheel glider.
For those not familiar with tailwheel gliders, there are usually only
two wheels. The main wheel is on the centerline, somewhat ahead of the
cg, and the tailwheel is on the tail. On most gliders, the main wheel
is very close to the cg - close enough that if you put in a pilot
substantially over the weight limit, the glider will sit on the nose.
The HP is different. Like most powered taildraggers, it carries 5-10%
of its weight on the tail. It also has other peculiarities. The
designer, the late Richard Schreder was a mechanical engineer and
retired naval aviator, and he could get the absolute most performance
out of the available material.

The particular glider I own, a T-tail HP-11 N821Z, was designed in 1962
but was still competitive in 1969, placing third at major contests.
Truly the design must have been a wonder in its day. But to get the
performance, some things had to be sacrificed. Since the design was
for competition flying, something a novice pilot presumably would not
do, the decision was made to sacrifice forgiving handling
characteristics.

These days, the HP's are no longer competitive but aren't really
suitable for low time pilots either. They have become, in many cases,
the glider of choice for the transition power pilot. All metal so they
can be tied down outside, with reasonable performance for a fraction of
the cost of glass, they appeal to the budget conscious transition pilot
who is used to the vagaries of flying taildraggers.

The ailerons are weak. In a typical metal trainer, such as the
ubiquitous L-23, the ailerons are so effective that the glider can be
pointed into a 10 kt headwind and a pilot can practice low speed roll
control by holding the wings level, balancing on the monowheel. In the
HP-11, you can barely hold the wings level with 30 kts.

Taking off is an interesting affair. A wing runner can, at best, hold
the wing up until about 10 kts is reached. Then you're on your own.
The ailerons are little help. You start out level, and if you notice a
wing dropping, you go hard over on the ailerons IMMEDIATELY to keep it
up - and add a helthy bootfull of rudder. The goal is to induce some
yaw, get that wingtip moving quickly up - before it digs into the dirt.
The ailerons alone will not be enough.

As soon as you get the wing coming up, it's time to take some rudder
out. You're not worrying too much about staying directly behind the
towplane. It's all about keeping the wings out of the dirt while you
are accelerating. Once you get about 30 kts, the ailerons come alive,
and then all is well. You have to keep the wings from digging in until
then.

If the wing digs in, all you can do is release and stay aboard for the
ride. You're moving slowly, so unless you hit something damage is
unlikely.

The right wingtip of the one I bought was damaged years ago. Minor
dents and some riveting work in the aileron told the sad story.
Someone stayed on too long, dug in too hard. The logbooks contained
the terse entry "Right wingtip repaired after groundloop." Remember,
it's experimental amateur built, so the recordkeeping rules and other
requirements of 14CFR43 do not apply.

My first few flights in the glider were interesting, but at least they
were off a wide grass runway with little opportunity for the wing to
dig in. Eventually, I got the hang of making the large, precise
required control inputs quickly, of keeping it balanced without roll
control until I was fast enough for the ailerons to come alive, and the
takeoffs became routine.

One day, after not flying a glider for over half a year, I got back in
my HP-11. In retrospect, my first glider flight in half a year should
have been in something much more docile - a trainer - or maybe a dual
flight in a powered taildragger. What's worse, both were available to
me, right there at the airport. I'm not sure what I was thinking - I
had just gotten the condition inspection done and signed off, and I
wanted to fly it. I was flying all the time - I just forgot how little
glider or tailwheel flying I had done in the past year. It was poor
decisionmaking.

It did not help that this time, the tow would be off a paved runway
only about four feet wider than my wingspan. I had flown off that
runway before - but that was when I was current in gliders and
taildraggers. Now I was current in neither. It had been over three
months since I flew a taildragger of any kind, and that time, after
over half a year of not flying tailwheel I needed help on the first
attempt, though the second landing was safe if not pretty. If I had
thought about that before flying, I might have made a different
decision.

Carefully I checked everything, strapped in, and gave the go. There
was about 7-10 kts of wind, almost all cross from the right. As soon
as I got going, I could see the right wing dropping. I put in full
left aileron, some left rudder - then a lot of left rudder. But
already I could see that it was too little, too late. I felt the
wingtip bite, and fumbled for the release. A second - and then I was
free. But I was sitting at nearly 90 degrees to the runway, pointing
into the wind.

I got out, rattled, and looked at the wingtip. I saw damage. "****.
I bent it." My wing runner, a recently minted commercial glider pilot
and FAA inspector, asked "Isn't that the wing that had the damage?" He
ought to know - he had just looked the glider over carefully, in
preparation for buying a half share in it. For a moment, I was so
shaken I couldn't remember. Then I saw the rivets and realized he was
right. I looked carefully at the wingtip. Were there new dents there,
or had it always looked like that? In my state, the damage looked
terrible, but stepping back I realized it was minor.

The real danger in damaging the wingtip of a metal ship is not the skin
- that's trivial, since almost no weight is carried there. The real
risk is damage to the spar at the wing attach points or to the flight
control system. Fortunately, on the HP-11 this is completely exposed
to the eye, covered only by a plexi shell. I looked at the spar. The
massive metal assembly stared back at me, and I realized how overbuilt
that spar was, and how much force would be required to damage it. The
skin then? I looked at the top and bottom surfaces of the wing.
Smooth as glass. I checked the movement of the ailerons. Free and
correct, smooth to full deflection. Maybe all I did was scratch the
paint?

We inspected the glider and came to the conclusion that all I did was
drag a wingtip throught the tall grass and short brush - embarassing
and rough on the paint but not actually dangerous. Then we restaged
the glider and I got back in. This time, the wing runner decided to
move to the upwind side.

On the second launch, I was READY. The moment I saw the slightest dip
in the right wing, I came in with full aileron and nearly full rudder.
I stopped it dropping, and a second later it was coming up. Taking out
most of the rudder, I waited. By the time the left wing began to dip,
I had full right stick and only a little right rudder. It was enough.
And then I was airborne.

I took a tow to 4000 ft, not sure there would be any lift and wanting
to practice stalls so I would be sure of not doing something this bad
on landing. As it turned out, I got only 30 minutes out of that flight
- I had quickly lost 1500 ft doing landing configuration (full flap)
stalls and there was very little workable lift. The landing was
uneventful though I used up almost 700 ft of runway - much too much for
my tastes.

I waited an hour, hoping the lift would improve, and took a normal tow
the second time. The takeoff was a much more relaxed affair - I knew,
once again, just how much rudder was enough. Doing it right once
brought it all back. This time, in the weak and disorganized lift, I
managed to scratch out an hour. The landing this time was perfect -
full flaps, soft, on both wheels, and stopped in well under 500 ft
without any significant braking, despite having to come in over power
lines. I was back in tune with my ship.

As I tied the glider down, I inspected it once more. Once more I could
not be sure if I had added a couple of little dents to what was already
there, but after a very careful inspection I was convinced it was in
condition for safe operation. I had thought that seeing what I did
would have scared off my potential buyer, but I was wrong. I guess you
see a lot when you accumulate thousands of hours of taildragger time.
He had seen many groundloops, including one from the inside of a
Luscombe he was flying. He understood exactly what happened, knew it
could well happen to him - and was not worried.

I got into my airplane to fly home, and I realized that a year of
flying almost exclusively tri-gear had indeed made me complacent,
willing to wait just a second more to see what would happen before
taking action. I resolved to either keep flying my HP year round, even
when there was no lift, just to keep current, or get some powered
tailwheel time on a regular basis. Skills will rust with disuse.

Michael