I have had an ASI failure in flight. A few hundred
feet up on an aerotow launch, I glanced at the instruments
and noticed that the ASI was reading 20 knots and slowly
falling. Realising that neither the tug nor the glider
were capable of flying at this speed, although they
were clearly doing so quite happily, I knew that it
had to be an instrument failure.

It was a very hot day, and the glider had been standing
out in the sun for several hours. What we subsequently
found had happened was that the plastic pipe leading
to the ASI had softened in the heat and slowly slipped
off the back of the pitot tube.

I decided to continue the aerotow, so I would have
some time to sort the problem out. The ASI continued
to drop until it was reading zero! Once off tow, I
slowly pulled the nose up until the pre-stall buffet
set in, so I then knew the stalling attitude. The type
of glider I was flying featured a large amount of washout
and I knew that the wingtips started bending down at
about 75 knots, so I slowly lowered the nose until
this happened. I then knew the attitudes between which
a reasonable speed could be maintained. BTW it was
a vintage glider, not mine, and I had only flown it
a couple of times before.

As it was quite a nice day, I soared quite happily
for a couple of hours, and even flew a short cross-country
flying by attitude alone. When I came into land, I
set the trimmer approximately central and flew a circuit
that would give me about a half brake approach. The
landing turned out to be a non-event, although I floated
a bit further than normal as the approach probably
erred a bit on the fast side.

I know of at least two other occasions where pilots
have suffered instrument failures and have managed
to cope with it.

Del Copeland


At 02:00 07 July 2006, Joe wrote:
I have done this to all my students prior to solo.
Almost every time,
their speed control improves by not chasing the airspeed
indicator. It
is a great confidence booster for the student and instructor.
At
least you know your student is not going to panic if
it happens in real
life. With all the bugs in summer, it does happen
from time to time in
real life.