ForeFlight Glide Advisor

[Tip]

ForeFlight has a new feature called Glide Advisor. In order to use it, you new to input your best glide speed & glide ratio. What would be doable numbers?

 

https://foreflight.com/support/video-library/watch/?v=glide-advisor&list=whats-new

[Duane Jefts]

Best speed would be lift over drag max for your airplane weight and configuration at the time. "L/D max"

 

Does the "Glide Advisor" factor in the wind? That could be the most important factor in determining glide distance?

[Doug G.]

Yes, it factors in wind and terrain.

[Doug G.]

I used the 8:1 glide ratio and 71kts best glide for zero flaps.

[FlyingMonkey]

Garmin Pilot has the same feature. I used 10:1 and 78kt (-6 flaps). The ring is depressingly small below 3500ft.

[NC Bill]

FDUSA lists BEST GLIDE RATIO as 8.5 to 1 for the CTLSi. http://flightdesignusa.com/aircraft/ctlsi/specification/

 

FWIW when I first owned my 2008 CTLS I made 3 engine out maneuvers in one flight while attempting a constant glide speed of 72kts into the wind for 2k' of decent and had trouble averaging 8:1

 

For safety's sake I program 7.5 to 1 into FOREFLITE and SKYVIEW. Your mileage may vary. No warranty expressed or implied 

[Tip]

My first thoughts were exactly with Andy's.

[Doug G.]

I stand corrected. I did use 8.5. 7.5 sounds too conservative to me since the 8.5 represents MTOW best rate.

I think I will go to 8.0 and then (eventually) do some flight testing.

CTLS POH -

Glide angle of the CTLS-LSA can be assumed in practice to be 8.5 to 1

with flaps 0°, and 7.9 to 1 with flaps -6°. With flaps further extended this

ratio gets worse. One effect of moderately set flaps is to reduce the

minimum sink, but the speed at which the minimum sink is observed

reduces faster. This results in a reduced possible gliding distance.

[NC Bill]

I'm not the Wing Safety Officer BUT two points I offer for consideration.

 

1- Most of our time in the CT is spent at -6 degrees of flap. Will you remember to go to best flap angle of 0 degrees in an emergency. If not you won't make even 8:1

 

2- Do you think you can maintain a constant 72kts best glide speed while looking for a place to land in a true emergency. I had trouble doing it engine out (a glider instructor friend of mine in the right seat monitored a/s) as it varied between 69 & 75kts during a 2k' descent from 5k'. And I had no emergency.

 

Again your mileage may vary but whenever there's a question now I ALWAYS err on the conservative side. Then again at 73 I'm now an old, and no longer bold, pilot.

 

Truth be told my call out on climb at 1000' is "chute's alive", and in many instances my plan is to pull the chute and just return the plane to the insurance company.

 

The "chute's alive" call out is from my days flying Cirri. Not to be dramatic but I had an acquaintance who also owned a Cirrus who DIDN'T pull his chute. He had an engine failure several miles out after take off and opted to try and return to the field. He did not make it.

[Doug G.]

Just got this on FB.

https://www.facebook.com/foreflight/videos/10155032414867481/

[Doug G.]

I have it in my head 71kts at 0°. Those are the only numbers I have learned. If I am looking for 71 I am also going to zero on the flaps. It is what I do for my BFR.

I am also much more likely to go by what I see informed by ForeFlight than the other way around.

[FlyingMonkey]

Didn't FD at various points tout glide ratios as high as 14:1 for the CTSW/CTLS?  Nobody really believed those numbers, but 8:1 sounds a bit low.  But if 8.5:1 is really waht PD is not publishing, I'll use 8:1 to be conservative.

 

BTW, my -6° @ 78kt is based on my own testing, that is the setting where my airplane seems to glide farthest.