"Ted Wagner" wrote in message
news
I1Kb.17587$7D3.9225@fed1read02...
A few seconds into take-off roll today in a Pilatus B-4, while applying left
stick to correct for a dipping right wing, the right wing suddenly dipped
all the way into the ground. The glider lurched to the right, and a second
or two later popped up into the air, a good 20 feet up and 30 or more feet
out to the side. By that time I had full left rudder in addition to full
left aileron, so the glider recovered rather quickly, and I was able to
bring it to normal take-off position right about the time the tow plane
started to climb. I was amazed he had maintained his heading directly down
the runway. The winds were light and variable. It was my ninth flight on
the B-4.
After landing, the tow pilot apologized, saying it was his fault --
something about the wake turbulence. But I'm still puzzled about what, if
anything, he did wrong; it looked like a completely normally take-off roll
to me.
I had thought that maybe a sudden tail wind had reversed the effective
correction of my aileron deflection during take-off, causing the right wing
to dip harder instead of leveling off. Does this make sense to anyone with
more experience on an aircraft like the B-4?
Also, I'm curious to know how much the CG hook location on the B-4
contributed to the squirrelly sequence of events after the right wingtip hit
the ground. How many 15+ meter gliders have CG-only hooks? Are such exciting
events more commonplace with CG hooks?
Other than the wobbly tows, I'm loving the B-4, it's the first 15-meter
single-seater ship I've flown, and the first with retractable gear...
~tw
It could have been a wake encounter. If there was a slight right crosswind,
the majority of the tug's prop blast would have drifted to the left and hit
the B-4's left wing, causing it to rise. I usually expect to encounter the
tug's wake after I have rolled about 2/3rds of the rope length. Sometimes
tuggies will advance the throttle more slowly in these conditions so as to
minimize the effect. That might be what your tug pilot was talking about.
I'm always ready to stuff in some fast downwind aileron at the wake
encounter.
As for the CG hook, well, it didn't help your situation. CG hooks aren't
much of a problem for airtow UNTIL you are way out of position and then
things can go really bad, really fast. I always remind myself before each
takeoff roll that this is a CG hook and to release if things start to go
bad. I won't accept a downwind takeoff with a CG hook.
I have done many training flights with pilots planning to fly a single
seater with a CG hook. The unfortunate result of many such flights is that
the trainee comes away thinking that airtow with a CG hook is no big thing.
It isn't a big thing -- until things get out of hand and most training
flights don't dare go there.
There's a BGA write-up on CG hooks and pitch-up incidents that should be
required reading for anyone contemplating airtow with a CG hook. Maybe one
of our British friends can provide a link to it.
Bill Daniels