Apologies if it's already been mentioned, but wind is a major factor when it comes to best glide speed for max range, which is what you're usually concerned with in an engine out scenario. Let's say you're gliding at 65MPH into a 65MPH headwind: You're going down vertically just like Bobby Breeden in that awesome STOL video. If you increase your glide speed when into a headwind, or when in a "sink," you'll increase your effective glide range. With a tailwind, you'd want to reduce your glide speed instead to extend your glide.

A good rule of thumb for best glide speed is somewhere between 1.3 and 1.4 x stall in current configuration.

A fun thing to practice is estimating your glide range -- how far you think you'd be able to glide from your current location, and then pulling power and seeing how far you actually could get. For most Cessnas in no-wind situations, the glide range "circle" will be about 8 degrees below the horizon. Pretty hard to estimate initially, especially when you're up high to begin with, but a fun exercise.

Nice chart.

My drag polar for a stock 182 doesn't look anything like it, though. The L/D max for mine is between 8:1 and 9:1, averaged over a few minutes of flight. Sink rates never get below 650 fpm at just under Vx when fully loaded. L/D at that speed is closer to 6:1. I use the glide ratio feature available on any portable Garmin unit to get the numbers, and got them on a dead calm day. An SR22 doesn't even get to enjoy 14:1 glide ratios even at best L/D. Color me shocked if a Sportsman allowed a 180 to out-glide an SR22.

I tend to prefer going to Vx (close to min sink) when doing engine out exercises as soon as the LZ is identified unless I'm doing a biennial. More time in the air to get situated, attempt restart, run checklists, run the radio, and maneuver to a closer LZ is more important to me in real life than trying to see if I can stretch a glide to a farther opportunity. It is rare when a marginal LZ is obviously the better option.

lesuther wrote:Nice chart.

My drag polar for a stock 182 doesn't look anything like it, though. The L/D max for mine is between 8:1 and 9:1, averaged over a few minutes of flight. Sink rates never get below 650 fpm at just under Vx when fully loaded. L/D at that speed is closer to 6:1. I use the glide ratio feature available on any portable Garmin unit to get the numbers, and got them on a dead calm day. An SR22 doesn't even get to enjoy 14:1 glide ratios even at best L/D. Color me shocked if a Sportsman allowed a 180 to out-glide an SR22.

I tend to prefer going to Vx (close to min sink) when doing engine out exercises as soon as the LZ is identified unless I'm doing a biennial. More time in the air to get situated, attempt restart, run checklists, run the radio, and maneuver to a closer LZ is more important to me in real life than trying to see if I can stretch a glide to a farther opportunity. It is rare when a marginal LZ is obviously the better option.

That's what I was trying to say, but my speakers don't always work well!

Minimum sink rate is great if you've got a landing site within range, but want some time to try a re-start, call a mayday, or say your prayers. But if my engine quits out over the Strait of Juan de Fuca, I want max range glide to try to get to dry land, or at least minimize how far I have to swim or someone else has to boat out to rescue me.

I don't know if I agree with slowing down to minimum sink with a tailwind, to get all the free distance I can. I think it'd have to be one helluva tailwind to compensate for the shorter range. Probably better to try for best glide speed since the tailwind will still help you.

Trimtab wrote:....Hot rod: Just in case you were not told - the book #s were arrived at by the BEST TEST pilot, using a FACTORY NEW plane, on a standard temp day, flying it till the he gets the best #s for the Boss. Those are often no more than MARKETING #s. That "new plane" could have any number of options added or not added. More than one student pilot has run out of fuel by using the BOOKS BURN RATE for fuel on an old run-out 150 - 152. Empirical evidence will win every time.

I know about new clean plane, good pilot, etc.
But some info, even when iffy, is better than none.
As far as empirical evidence, it's pretty easy to figure out minimum sink speed-- just pull the power, try different speeds, and note the VSI reading.
Tougher, or at least more time consuming, to figure out best glide range speed.

There's lots of C180 pilots here, I'm surprised someone with a later model hasn't kicked in with the best glide info from his POH. I know my 1969 C150 (first airplane) POH had it, & I'm pretty sure my 1964 C150TD POH had it too. Correct or not, I'd like to get a photocopy of the similar page out of a C180 POH and put it in my 1953 owner's manual. If anyone can oblige me.

I did this exercise with my '56 180, 2 blade, sportsman/vg's, modestly loaded, power off, blade feathered, and felt I got max. distance glide at around 65mph ias.
YMMV
Gary

hotrod180 wrote:

Trimtab wrote:....Hot rod: Just in case you were not told - the book #s were arrived at by the BEST TEST pilot, using a FACTORY NEW plane, on a standard temp day, flying it till the he gets the best #s for the Boss. Those are often no more than MARKETING #s. That "new plane" could have any number of options added or not added. More than one student pilot has run out of fuel by using the BOOKS BURN RATE for fuel on an old run-out 150 - 152. Empirical evidence will win every time.

I know about new clean plane, good pilot, etc.
But some info, even when iffy, is better than none.
As far as empirical evidence, it's pretty easy to figure out minimum sink speed-- just pull the power, try different speeds, and note the VSI reading.
Tougher, or at least more time consuming, to figure out best glide range speed.

There's lots of C180 pilots here, I'm surprised someone with a later model hasn't kicked in with the best glide info from his POH. I know my 1969 C150 (first airplane) POH had it, & I'm pretty sure my 1964 C150TD POH had it too. Correct or not, I'd like to get a photocopy of the similar page out of a C180 POH and put it in my 1953 owner's manual. If anyone can oblige me.

My 62 model doesn't have anything about best glide in the manual that I have seen.

Here is the page from my 1976 A185 manual. Not the data that you need, but maybe will keep the discussion going in the right direction:


Correction. This is from a 1975 manual that I found on line and use for reference.

This is exactly what I was looking for. Thanks!
Per the chart, 15 miles glide from 10,000' AGL (or a mile and a half for every thousand) at 80 mph. The math works out to 7.9:1. My 180has a fair number of mods, but none that should affect the aerodynamics (STOL cuff, etc) and so should perform pretty close to the chart--minus points for dirty, maybe a bit out of rig, etc of course.

I'm curious if anyone has a similar POH chart from a different year model skywagon which shows different figures?

hotrod180 wrote:Minimum sink rate is great if you've got a landing site within range, but want some time to try a re-start, call a mayday, or say your prayers. But if my engine quits out over the Strait of Juan de Fuca, I want max range glide to try to get to dry land, or at least minimize how far I have to swim or someone else has to boat out to rescue me.

I don't know if I agree with slowing down to minimum sink with a tailwind, to get all the free distance I can. I think it'd have to be one helluva tailwind to compensate for the shorter range. Probably better to try for best glide speed since the tailwind will still help you.

Hotrod, if you are getting 425fpm at 70 mph and 500fpm at 80 mph, then a 10 mph tailwind would give you the same ground speed but you'd be in the air 15% longer. In other words you'd extend your glide range by 15%.

51C170 wrote:...Hotrod, if you are getting 425fpm at 70 mph and 500fpm at 80 mph, then a 10 mph tailwind would give you the same ground speed but you'd be in the air 15% longer. In other words you'd extend your glide range by 15%.

Can't quite figure how to do the math, but it seems to me that a 10 mph tailwind would add about the same distance to the 80 mph best glide. So 70 would still be minimum sink, and 80 would still be max range.
So my engine-out mantra is pull the prop knob, trim for 80, and turn downwind if possible.

hotrod180 wrote:

51C170 wrote:...Hotrod, if you are getting 425fpm at 70 mph and 500fpm at 80 mph, then a 10 mph tailwind would give you the same ground speed but you'd be in the air 15% longer. In other words you'd extend your glide range by 15%.

Can't quite figure how to do the math, but it seems to me that a 10 mph tailwind would add about the same distance to the 80 mph best glide. So 70 would still be minimum sink, and 80 would still be max range.
So my engine-out mantra is pull the prop knob, trim for 80, and turn downwind if possible.

Assuming 5000ft agl and the above figures, you'd get 15 miles at 90 mph gs vs 15.68 at 80 mph.

So your right in that the difference is minimal considering the real life variables and the fact that your not likely to be calculating all this during a real life emergency. Just fly the plane.

My one engine failure happened at about 200 ft after pulling up from a spray run, so not enough to time to think enough about it to mess it all up. Just landed in the next field.[emoji3]

hotrod180 wrote:As far as empirical evidence, it's pretty easy to figure out minimum sink speed-- just pull the power, try different speeds, and note the VSI reading.

Just to add my 2c here, if you want to do this with any precision, take altimeter data points at regular time intervals (30 sec, for example). VSIs are full of error.

Perhaps I should post the remaining 13 pages of the sportsman stol flight test report conducted by Flite Research... and sit back and enjoy the commentary!

180driver wrote:Perhaps I should post the remaining 13 pages of the sportsman stol flight test report conducted by Flite Research... and sit back and enjoy the commentary!

Indeed you should.

180driver wrote:Perhaps I should post the remaining 13 pages of the sportsman stol flight test report conducted by Flite Research... and sit back and enjoy the commentary!

Yes please...

Ok! Just added the rest of the report to my photo gallery. Too many images to post here. I think it has some interesting findings for sure.

Thanks for the report. Just a few pages missing (glide ratio appendix).

I took another look at the owner's manuals yesterday--
best angle is shown as 60-ish in one place, and 70-ish in another.
Turns out to be 60-ish with flaps 20 and 70-ish clean.
So best glide of 80 is halfway between VX of 70 & Vy of 90,
what Rob suggested several posts ago.
Maybe a rule of thumb to remember when no best glide info is given.

hotrod180 wrote:I took another look at the owner's manuals yesterday--
best angle is shown as 60-ish in one place, and 70-ish in another.
Turns out to be 60-ish with flaps 20 and 70-ish clean.
So best glide of 80 is halfway between VX of 70 & Vy of 90,
what Rob suggested several posts ago.
Maybe a rule of thumb to remember when no best glide info is given.

When trying to stretch out your glide, the flaps will be retracted. While flaps do generate lift, the associated drag from the flaps and higher tail loads due to elevated pitching moment will usually result in a less favorable L/D ratio.