Readback: August 2017

In April Killer Quiz, The Prof and the Pilot, I dont think that the answer to the last question is correct. With tailwind, one should reduce the airspeed below best glide speed, which in turn reduces the sink rate. Gliders pilots are very familiar with these concepts.Unfortunately, Cessna doesnt publish sink rates at various speeds to compute that accurately, so we are left to back-of-the-envelope calculations. We know that at best-glide speed (65 knots.

Editorial Staff

Wednesday, July 05, 2017 at 12:00 AM ET

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Key Takeaways:

A reader challenged a quiz answer, suggesting optimal glide speed with a tailwind requires reducing airspeed below best glide, which authors acknowledge as technically true but impractical for piston singles.
The decline in general aviation is primarily attributed to soaring aircraft costs due to liability lawsuits and the unwelcoming atmosphere created by airport security measures like fences.
An autopilot restriction on an ILS approach (but not RNAV) is explained by the ILS's susceptibility to terrain interference, which can cause undamped autopilots to react erratically, unlike GPS-based RNAV systems.

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Higher Math

In April Killer Quiz, “The Prof and the Pilot,” I don’t think that the answer to the last question is correct. With tailwind, one should reduce the airspeed below best glide speed, which in turn reduces the sink rate. Gliders pilots are very familiar with these concepts.
Unfortunately, Cessna doesn’t publish sink rates at various speeds to compute that accurately, so we are left to back‑of‑the‑envelope calculations. We know that at best‑glide speed (65 knots), sink rate is 730 fpm and this requires 73 knots tailwind to reach the threshold. Assuming that sink rate is 600 fpm at 50 knots, which seems realistic, flying at 50 knots would need only 63 knots tailwind.
I love your quizzes. I learn something from each one.

Thomas Daniel
Portola Valley, CA