What is your Best Glide and Min-Sink

Updated: Dec 14, 2019

FlyWire took a look at Best Glide and Min-Sink for the A36 Bonanza using the POH Best Glide Speed. Interesting results. What we found was that if you have an engine failure at altitude your best bet would be to set Best Glide Speed (110 Knots for the A36) until you are VERY near your target landing spot. At that point transition to what Beechcraft calls the Emergency Approach Speed (81 knots), because you want to maximize your remaining time in the air. The problem with Min Sink at this point is that it is so slow you hardly have enough energy to flare, and at the Emergency Approach speed you are 1.4 x the Stall speed giving enough energy to flare and land the airplane.

Thats all well and good, but what if your POH does not tell you what the Best Glide Speed is. Or you have modified the wing considerably from stock (all legal of course). The reality is that you have to test for it. A 'close enough' test is to find Min Sink Speed and derive the Best Glide Speed. That is what FlyWire did in this video "C-180 Skywagon Determining Best Glide and Min-Sink" https://youtu.be/1iNZZgSGkCw All you need to do is collect data points for Min Sink and put them into the spreadsheet.

The Spreadsheet has two worksheets, one for airplanes that use MPH and one for Knots. Use the one for your airplane collect 4 data points during a min sink glide 4-6k' above the ground. Look for a stable glide at the slowest decent rate you can. Then every 30 seconds record the speed and descent rate. Once you have a good idea of Min Sink, multiply it by 1.316 and use that as your best glide speed. Test it again and record the descent rate. With all that fill in the Green Blanks on the Spreadsheet and you'll see your results all laid out. The only question is whether you should set an Emergency Approach speed like Beechcraft did (if so, multiply the stall by 1.3 for the Approach Speed).

Now you've got some good reference speeds to build your engine out strategy around. Good luck and keep us posted on your progress!

Excel Spreadsheet to Determine Best Glide and Min-Sink:


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