setting up ForeFlight glide ratio

[Skylarktc]

what do most folks use for the glide ratio of a Super D. I have seen on the inter webs anywhere from 7.5 to 1 to 10.0 to 1. What do you guys use?

 

[Derek Lawless]

It’s somewhere between a brick and a feather. I’m probably imagining things, but I feel like I’ve seen some documentation on this in maybe the latter AFM? I’ll try to look tonight.

 

[Derek Lawless]

It’s somewhere between a brick and a feather. I’m probably imagining things, but I feel like I’ve seen some documentation on this in maybe the latter AFM? I’ll try to look tonight.

Looked through all versions of the operating manual. No joy.

 

[Pburns]

Go up and do a measured glide over a couple of miles from a known altitude on a calm day. Then just do the math.

Pete

 

[Skylarktc]

I suppose I could do that. But I would have thought for sure someone would have done that already and had a good number for me.

 

[Bob Turner]

What will you do with said number?

 

[Skylarktc]

You can put that number into ForeFlight. Then while you are flying it provides a nice little ring around your airplane showing how far you can glide if you lose an engine. The ring is dynamic and changes based on your altitude and current winds. It is not a catch all to relieve you from knowing your airplane. But it sure is a nice backup to confirm your assumptions based on experience with the airplane. A convenient tool in your bag of tricks to use if there is an engine out emergency. The ring is based on your best glide speed and ratio. I cannot find a published glide ratio for the decathlon so I thought I would ping the resident experts here and see what you guys thought.

 

[Derek Lawless]

What will you do with said num

Go up and do a measured glide over a couple of miles from a known altitude on a calm day. Then just do the math.

Pete

Or just climb to 3000AGL, trim for best glide, and record the vertical speed. Glide ratio = (MPH × 88) ÷ FPM.

 

[Skylarktc]

Thanks, I will try that.

 

[Bob Turner]

Old school here - I have encountered Foreflight, but am not well versed. It did help with weather and TFR on two long flights last fall, and was able to tell me where we were on SWA headed home (God, I hate airliners).

I had no idea the program would compute a glide path to the scene of the crash. Good for them.

Believe it or not, even though I am rated A-320, I still prefer compass and a watch, but lately aided by distance, speed, track, and bearing on the right side of a 496.

TFR popups are nice to know about. If it quits, the last thing I am looking at is cockpit displays.

 

[Thedude]

I haven’t messed with that in ForeFlight yet but I’ll give it a go. I could see it being a useful bit of situational awareness if you keep it in the crosscheck. If the engine quits you should have recollection of a rough distance and direction of an airport, if any, that was inside that ring.

 

[JackC]

I’d guess 7-8

Also if you are still making oil pressure and can pull that prop back it’s going to make a decent improvement to your glide

Thus “depends”

 

[Bob Turner]

The Decathlon prop will "pull back" the instant oil pressure goes to zero.

 

[vupilot]

I have mine set to 8:1. The data I saw for an 8KCAB says "8:1 to 9:1." It did not say specifically Super D. I wonder if that's maybe with oil pressure and without or due to different configurations 150hp vs 180hp with different length props, intersection fairings or not etc. I like setting it to something I'm pretty certain I can make so the lower number.

 

[Thedude]

Can’t get very far if you’re low but the feature seems to work and depict a fairly accurate representation based on altitude and terrain.

 

[Skylarktc]

Whelp, I determined my glide ratio today. Yikes, I came up with 7 to 1. 75 mph best glide speed yielded 925 fpm. I plugged it into ForeFlight, used their fancy glide ring, and sure enough I successfully glided to an airport.