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Best Glide @ Engine Out


Runtoeat

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Was redoing my checklist and got thinking about "best" flap setting and airspeed for "engine out" landing. I went thru our Forum and thought we had discussed this but couldn't find any threads. I see some discussion of this on the other forum but it isn't clear to me what the best flap setting and speed is? I believe that the CTSW POH recommends 15 flaps @ 63 kts but I also see that some pilots think 0 flaps with 78 kts is best? Guess that it boils down to picking an altitude and, if sink rates are known, then calculating how far one can go before meeting the ground under each condition.

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When my plane was new I made some placards for the panel. What I gleaned from the manual, at that time, was best glide is 63K with 15 degrees. I also placarded Vy with zero flaps as being 78K, Vy with minus 6 is 86K, Vx at zero is 66K, and Vx with 15 flaps is 51K.

 

For what it's worth.

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The CTSW manual has best glide at 63 KIAS without a specific flap setting. This seems to work well at -6, 0 and 15 flaps. The 78KIAS glide value comes from the CTLS manual for 0 flaps. It works ok for glide range, but if you want glide time aloft 63 is a better number. Using a value of approximately 1.3 times the stall speed in a configuration is safe, it may not give you the best glide range though.

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The CTSW manual isn't the best. In the one that came with my plane, Under Chapter 7, Emergency Procedures, it says to establish the best glide speed of 63K. Then, in the same paragraph it says to maintain 63K with 15 degrees until final approach. Then it says to select flaps 40 before touchdown but it doesn't mention reducing speed from the aforementioned 63K which we all know is too fast at this point. Then, if you look in the Flight Training Supplement that also came with my plane, in the Engine Failure paragraph it says to keep a minimum speed of 62K (not 63K) but does not mention flaps. Then it says to use flaps 40 and airspeed of 43K on short final.

 

So, between the two books it might be reasonable to deduce that best glide is either 62 or 63K with no flaps. But, it might also be reasonable to deduce best glide might be 63K with flaps 15. Maybe the thing to do is use 62.5K with flaps 7.5 degrees. (just joking!).

 

However, I've never tried 43K as a stabilized speed on short final.

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Here is a pretty simple test to try that will convincingly give you the answer that I did 5.5 years ago.

 

Plan for a long final and pbe high and go throttle idle with 0 flaps at roughly 70kts and look for your aim point.

Next dial in +15 flaps at 63 kts and you will see right away that you will fall under your original glide path as soon as you stabalize your approach again after selecting +15 flaps..

 

A great excercise for any CT pilot to try.

 

Rgds,

 

Jos

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Thanks for the replies. I'll do some experimenting next time aloft.

 

To Jos, not sure what you mean by "pbe"? I'll try this procedure if I know what "pbe" means?

 

How about my original thought. Go to altitude, trim for stabilized 63 kts @ 15 flaps and record loss of altitude over one minute. Do the same with 78kts @ 0 flaps.

If the loss of altitude is similar between the two conditions, consider using 78 kts @ 0 flaps since this allows one to travel greater distance over time.

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Thanks for the replies. I'll do some experimenting next time aloft.

 

To Jos, not sure what you mean by "pbe"? I'll try this procedure if I know what "pbe" means?

 

How about my original thought. Go to altitude, trim for stabilized 63 kts @ 15 flaps and record loss of altitude over one minute. Do the same with 78kts @ 0 flaps.

If the loss of altitude is similar between the two conditions, consider using 78 kts @ 0 flaps since this allows one to travel greater distance over time.

 

Typo with an extra p, should have read "be".

 

Timing is also an idea, but what demonstrates it best is when you actually see this happening right in front of you when you drop below your original best l/d glidepath when you dial selct 15 flaps.

 

78 kts at 0 flaps is too fast for best l/d. I believe it is just around 70kts. Minimum sink (staying up as long as you can) is around 60 kts (give or take).

 

Us experienced "old" (meaning ex) glider pilots almost automatically do this as a mental calculation when first familiarizing us in new aircraft.

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Correct me if I'm wrong, but isn't it logical to always want minimum drag for best glide?

 

I'm not too familiar with "negative" flap settings. Would that increase drag or decrease drag? It seems like if taken to extremes, negative flaps become spoilers at some point, and would hurt glide performance.

 

Right?

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I did inherit that one Tom. After 300 hrs it's a bit dog-eared but readable. Well, for my old and tired eyes barely readable.

 

I was hoping to find a homemade version put together by owners based on actual flying and that could be formatted and printed in larger type.

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I did inherit that one Tom. After 300 hrs it's a bit dog-eared but readable. Well, for my old and tired eyes barely readable.

 

I was hoping to find a homemade version put together by owners based on actual flying and that could be formatted and printed in larger type.

 

Bill ,the same checklist is in the manual. The manual can be downloaded from www.flightdesignusa.com . If you can't figure out how to enlarge it at home take a copy to a print shop and have them do it. Tom

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Correct me if I'm wrong, but isn't it logical to always want minimum drag for best glide?

 

I'm not too familiar with "negative" flap settings. Would that increase drag or decrease drag? It seems like if taken to extremes, negative flaps become spoilers at some point, and would hurt glide performance.

 

Right?

 

not minimum drag but best lift / drag ratio

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Since I started this thread and there are some wondering if there's a "custom" checklis, here's a custom checklist that I came up with. It is in MS Excel format so can be modified to fit individual tastes and is a compact size. This version is currently a "work in progress". I will laminate the four pages and insert a ring in the upper left corner. I keep this within ready reach during flight. I have tried to read posts and to gather data from FD AOI but please verify that speeds and comments shown on this list are accurate and correct per FD published data before relying on this checklist for flight.

N9922Z check list_110214.xls

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Since I started this thread and there are some wondering if there's a "custom" checklis, here's a custom checklist that I came up with. It is in MS Excel format so can be modified to fit individual tastes and is a compact size. This version is currently a "work in progress". I will laminate the four pages and insert a ring in the upper left corner. I keep this within ready reach during flight. I have tried to read posts and to gather data from FD AOI but please verify that speeds and comments shown on this list are accurate and correct per FD published data before relying on this checklist for flight.

N9922Z check list_110214.xls

 

Regarding your best glide speed I think that speed maybe referenced at total gross weight in it may be correct for that configuration (although it seems high imo), however the lighter the the load, the lower your best glide speed. Same scenario as glider flying with and without water ballast.

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