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Old June 27th 08, 01:05 AM posted to rec.aviation.piloting
E Z Peaces
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Posts: 8
Default bouncing off the runway

Ol Shy & Bashful wrote:
On Jun 25, 10:00 pm, E Z Peaces wrote:
Yesterday I chatted with a retired man flying a model airplane. He said
he'd taken lessons in a plane with conventional gear in the 1950s. On
his third lesson, the instructor had him land. It was perfect.

After that, every time he landed he would bounce and float above the
runway. His instructor didn't know what caused it. A senior instructor
went up with him and observed that when he touched down, he didn't
continue to hold the stick back. That caused the tail to rise and the
plane to lift off.

That doesn't make sense to me. I've always understood that with
conventional gear, excess speed is the cause of bouncing and floating.
With the main wheels forward of the center of mass, your angle of attack
will increase when you touch down, and the plane will rise if you still
have flying speed.

If a pilot touches down too fast, I've understood that he needs to keep
the tail up and use the brakes without nosing over.

If the instructor had told him he was touching down too fast because he
wasn't holding the stick back far enough during descent, that would make
sense to me because a higher angle of attack induces more drag.

The man said the problem was that he had failed to keep the stick back
after touchdown. Does his recollection make sense?


Are you kidding? After nearly 60 years the recollections of a 3 hour
student have any validity? The VAST majority of botched landings are
due to flawed airspeed control and it doesn't matter what kind of
airplane. Many instructors fail to recognize that, or, fail to do
anything about it, especially when instructing. I see it all the time,
harp about it daily,and continue to mentor less experienced pilots on
this.
In the case of taildraggers specifically, if the airspeed and vertical
speed are not controlled, it will nearly guarantee a bounce with
predictable control problems. For a three point to be executed
properly, the airspeed MUST be near stall as in within Vso+ 5 mph or
less. Anything in excess of that must be dissapated during the flare/
roundout or touchdown and will result in an unpredictable touchdown
point.
Now, are you talking about a full stop landing? Then the touchdown
speed should be as low as possible. Are you talking about a gusty
cross wind? Then you have a different set of conditons to deal with.
Not to be a pushy butthead but I've got at least 6-7000 hours in
tailwheel aircraft crop dusting in a broad variety of aircraft
including twin engined and a lot of time instructing in them (couple
of thousand hrs..?)
taking a deep breath and just sitting back now .....
Ol S&B
p.s. I realize you were asking and not postulating so please don't
feel I was being gruff towards you personally?


Thank you very much! I was postulating. From what I knew, a perfect
landing with conventional gear means stalling so low that the wheels
touch down gently, and you can't rise again unless you're going too
fast. I lacked the experience to know if there was any way his
recollection of the cause of his problem could be correct.

I've never had a flying lesson. About second grade I began reading
books about the mechanics of aircraft. Through my teens I often held
papers at arm's length, curved for rigidity, to get a feel for the
relationship between speed, angle of attack, lift, and drag. I studied
pilot manuals for the Thunderbolt and the Mustang and and cockpit photos
of other aircraft. I liked to pedal to the airport and watch the
mechanic work.

In the high-school library I found a 1948 book by an instructor named
Lang, I think. It explained concepts learned from experience rather
than laymen's theory. Throttle for vertical speed, elevator for
airspeed. Ailerons for direction, rudder to center the ball. If you
want to know where you're going, watch the way the scenery shifts
against the windshield.

As a CAP cadet, I was assigned to the simulator room at an Air Force
base the summer I was 17. Those simulators had frosted windshields and
no video. Other cadets tried and failed with the F-106. I was the only
one to try the B-25. I wasn't familiar with bomber cockpits, but the
individual instruments and controls were familiar. I toured Boston by
radar, returned to the base, set the flaps, guessed a reasonable descent
speed, and followed the instruments in, using the elevator for airspeed
and the throttle for descent.

In view of my awe of flight, it was disappointingly easy. The sergeant
in the control booth played with me on my second flight. I had various
problems including an engine fire and loss of hydraulics. Books had
told me how to respond to such emergencies, and I made another adequate
landing. Then a pilot came in to log some training time.

The following October a parent in the squadron invited me flying. His
invitation was very brief. I hadn't known he had a plane because he'd
never spoken to me before. It was a Cessna 310.

At the airport, he told the other three to sit in back and me in front,
on the left. That was the second time he'd spoken to me. I figured he
wanted me in front because I was taller.

At 3,000 feet he told me, "Take over." I thought he intended to let me
guide it a minute or so, but he didn't speak again, so I spent twenty
minutes touring. I would have liked to hedgehop but refrained because I
didn't have permission.

Eventually he told me to find the airport. I knew the terrain and had a
compass, and before long the airport was in sight. When we were almost
there he said, "Traffic pattern is to the left." I'd forgotten that. I
steered right and began circling left.

Then he said, "Runway 1." That would mean a complete circle. I brought
him around to a point far enough out that I thought he'd have a
reasonable glide path. Instead of taking over, he cut the throttle to a
whisper, dropped the gear, and set the flaps. He told me the descent
speed. That was the fifth thing he'd said to me since taking off. I
think he was the last thing he ever said to me. From a couple of miles
out I could see we were overshooting the end of the runway, so I reduced
our speed slightly by raising the nose.

As we got closer, I saw a gusty crosswind on the sock. The other runway
would have been better but he said nothing. He'd know how to handle the
crosswind. He'd also know how to flare. I didn't know our rate of
descent but figured we'd crash into the runway if he didn't flare or if
he flared too soon.

We were down around treetop level when I realized there was no longer
time for him to take over. How could I flare safely without knowing our
stall speed or how the aircraft would respond? In climbing aboard I
hadn't noted the height of the window above the wheels. It seemed only
realistic to predict that in two more seconds we would be a ball of
flame. Still, I wouldn't have missed this opportunity for the world.
At least I had tricycle gear, which tolerates landing too fast and
crosswinds.

As I flared, the sock showed a big gust from the left. Would we be
drifting right when we touched down? I knew a responsible pilot would
have let the gear absorb the stress, but I was a perfectionist novice.
I dipped the left wing while kicking right rudder to stay aligned with
the runway, then picked the wing back up. That was to skid into the
crosswind. It seemed risky because I didn't know how well the airplane
would respond at that speed and with the mass of the tanks on the wingtips.

I expected a vertical bump and a lateral lurch. Instead, tire vibration
was the only clue that we had contacted the runway. I didn't need
brakes. When it was clear that we would need throttle to make it to the
parking area, the pilot took over without a word.

Beginner's luck: that deadstick landing in a crosswind was my first and
last opportunity to fly an airplane.