AOPA Pilot Magazine - August 2021 - 16

LETTERS
Reality check
Turn around or land
straight ahead?
Since I have been doing turnbacks for 30 years,
Richard McSpadden's article ( " Safety Spotlight:
The Runway Behind You, " June 2021 AOPA
Pilot) really got my attention. The results with
the Beechcraft Bonanza were interesting. I don't
think it would be because of a shorter glide
ratio. Best I can tell, it will glide farther than a
Skyhawk-1.7 nautical miles per 1,000 feet versus
the Skyhawk's 1.5. I think the results could
have been affected significantly by the climb
speed versus the glide speed. In the Skyhawk,
VY
is higher than VG
the Bonanza, VY
is less than VG
giving a lift reserve. In
making that a
big disadvantage. But on the other hand, the
climb performance is so much stronger in
the Bonanza, it seems that would more than
compensate for the low VY
speed. I was very
surprised it wouldn't return to an 8,800-foot
runway. I'm currently based at an airport with
a 3,665-foot runway-we climb to 500 feet in a
Skyhawk and have no trouble in making it back.
Of course, as you know there are many factors.
Warren Webb Jr. / AOPA 1099812
Cromwell, Connecticut
Thanks to feedback like this, the AOPA Air Safety
Institute revisited its conclusions regarding the
effects of glide ratio on the ability of an aircraft to
return to the runway. The video Reality Check:
The Runway Behind You (airsafetyinstitute.
org/realitycheck/runway_behind_you) concludes
that the turnback is not a good option for
aircraft with faster climb and glide speeds, which
travel farther from the runway. -Ed.
I enjoyed Richard McSpadden's article " The
Runway Behind You. " In the article, he mentions
that " the advantages of an engine in idle
are believed to be minimal. " I don't necessarily
disagree; among other things, it depends on
your threshold for " minimal. " But it bugged me
that no one seemed to have any actual measurements
of that, and I'd like to know what it
is for my airplane. So, on a day perfect for the
task (and above an airport), I did a large number
of long glides to measure the glide ratio at
different speeds and with the engine either at
idle or with the mixture cutoff.
16
AOPA PILOT / August 2021
The results were very consistent. The speed
for best glide (for that gross weight and center
of gravity) didn't change, but the glide ratio was
reduced by 11 percent going from idle to cutoff.
That took the ratio from 10.9:1 down to 9.7:1.
That's a loss of 1,200 feet distance in a glide
from 1,000 feet altitude, so it seems worth it to
take it into account.
Interestingly, both of those glide ratios are
well above the 8.9:1 that Cessna provides in the
POH. The airplane is stock, except that it has a
three-blade prop.
Thanks for the interesting articles, and for
all you do to promote aviation safety.
Scott Hunziker / AOPA 1103741
Des Moines, Washington
Distractions
Thanks for the great article on distractions
( " Waypoints: Distractions: Dispatch them, "
May 2021 AOPA Pilot). I've had the same
conversations with my kids and their friends
and couldn't help but smile when Thomas B.
Haines mentioned the noise from the back of
the airplane on his way home from the beach.
Thanks to Richard
McSpadden for his
great work with ASI
and articles in AOPA
Pilot. I write to ask
about his deduction
regarding root cause
for crummy turnback
performance by the
Bonanza. He explains
it by stating Bonanzas
have a shorter glide
ratio than the other
airplanes tested. An
A36 has a better glide
ratio than a Super Cub,
172, or Cherokee so I
wonder what could be
a better explanation.
For one thing, I know
failing to pull the prop
control back has a huge
adverse impact in glide
performance. Could
that have been a factor
in the tests?
John Sandvig / AOPA 729399
Seattle, Washington
https://www.aopa.org/training-and-safety/online-learning/safety-videos/the-runway-behind-you https://www.aopa.org/training-and-safety/online-learning/safety-videos/the-runway-behind-you
AOPA Pilot Magazine - August 2021

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