normb@tekred.UUCP (Norm Babcock ) (10/10/84)
I used a real nice Tuesday as an excuse to go flying,and
do what several people on the net suggested (thanks for the
input), which was to try power-off turns, and note the altitude
loss. The a/c was a C-152, in fair shape; the load was myself
and a CFI. The reason I took the CFI along was to record data,
and partly because of his response when I posed the question of
turning back to the field upon loss of power during take-off.
The first thing I did was to set up a glide at 5,500 (2500 agl),
and jockey around with the airspeed. I was amused and amazed that
the Cessna recommended speed of 60k produced the minimum sink
rate, which ranged from 400fpm to 600fpm, with a strong average
of 500. (Anyone know why the variation? Cool day with light
cloud and early evening, thermals should have been in bed.)
I tried and timed turns, with the CFI noting altitude loss. The
best technique seemed to be to roll briskly into a 45 bank, drop
the nose a little, and haul it around. The average altitude loss
was about 200 feet to do a 180, and closer to 300 to do a
teardrop. I found that by making a 180, and then dog-legging
back to centerline produced the best results.
It also became apparent that if you can count on 500fpm climbout
and 500fpm glide, you'll be able to make it back to the liftoff
position on the runway, barring wind. Surprisingly, a stiff wind
straight down the runway can help: for a given altitude you're
not as far from the end of the runway (lower ground speed),
after the turn, you'll cover more ground downwind due to higher
groundspeed.
In summary, it seems that if you know your plane, and the
associated parameters, turning back is an option, above a certain
agl after t.o. Any lower,straight ahead, any further, whereever
you can. But there is a window where turning back makes sense. I'd
expect that the window would get smaller quicker as the gross
weight goes up. Anyone with a 182/185 willing to experiment?
Incidentally, the CFI was opposed to anything but straight ahead,
but after messing around changed his mind. He did state that
while he would adopt turning back as a personal option, he still
would recommend to students that they go straight. Liability issue?
Norm