I pored through the owner's manual for my 1953 C180-- no mention of best glide speed or engine-out glide ratio. These were both addressed in the 1960's & later Cessna POH's I've seen. Does anyone have a later model C180 manual with the pertinent figures?

What got me thinking about this was my new Avare gps app-- it has a feature where the airports within gliding distance in the "nearest" list are highlighted green, the ones out of range are red. Thought that'd be a pretty cool thing to have in an emergency. However, you have to enter the proper glide ratio, the example shows a C172 at 7.5:1. I kind of remember my C150 manual indicated 8:1.

Hotrod-

What would you think about trying it out and telling us the result.... maybe we could get a few data points... Stock wing, Sportsman, Wing-X. Seems like a good idea.

Thanks,
gunny

Hot rod,

If you are ever faced with that discouraging feeling caused by an engine failure, don't forget to pull that prop controll to full coarse pitch ASAP.

MTV

mtv wrote:Hot rod,

If you are ever faced with that discouraging feeling caused by an engine failure, don't forget to pull that prop controll to full coarse pitch ASAP.

MTV

This action makes a difference in drag that is hard to believe.

Scolopax wrote:

mtv wrote:Hot rod,

If you are ever faced with that discouraging feeling caused by an engine failure, don't forget to pull that prop controll to full coarse pitch ASAP.

MTV

This action makes a difference in drag that is hard to believe.

There is no #!! wieght makes it move.
Pull the prop and screw the trim all the way nose up, should get you as far as you can get.

Here is some flight test data from a 1955 cessna 180 with a sportsman stol kit. This is at gross weight. Documents glide ratios at various flap settings and speeds.

That chart is awesome. But lots to look at...... So no flaps at 80 is best glide?

bigrenna wrote:That chart is awesome. But lots to look at...... So no flaps at 80 is best glide?

Looks like 70 to me?

FWIW my 53 180 manual has a graph type performance / fuel burn power chart, I can't make heads or tails of it. I just now made a photocopy of a regular power table out of a borrowed 1957 180 manual.
My point being that I can't figure out 180driver's chart.
Judging from the two responses, I'm not the only one.

That chart looks like it addresses sink rate anyway, and best sink rate speed is not necessarily the same as best glide distance speed. Barry Schiff wrote an article about that in AOPA Pilot a few years ago, he said best sink speed was generally attained by winding in full nose up trim and letting go of the stick. That would give you the longest time in the air, but not necessarily the most distance. Kinda like the difference between Vx and Vy. I don't care too much about hang time, I want to be able to cover the most distance as I think that gives me the most landing options. I kinda recall that (generally speaking) best glide speed equates to Vy, which is around 90.

Hotrod

A personal view.
If I have a power failure there will only be ONE Nearest, and I will already know where it is - Day-VFR.
My only Rule of Thumb is don't let your thumb get lost. Got me through fifty some years of flying.
I hope your 'nearest' list comes with the closest one at the top of the list. Would not be wanting to figure out how far I could stretch and engine out situation. A strong wind might influence my decision. I have never had an engine quit completely, but have had a couple "stumble" and it was enough to cause a spasm from my rectum to my retinas. Brain did not default to arithmetic.

MTV's advise on the prop is a must. Never thought much about it when I had heavy Hatzells - Then I bought an MT. Pushing the MT prop flat can put yer chin on the panel.

Chris C

mtv wrote:Hot rod,

If you are ever faced with that discouraging feeling caused by an engine failure, don't forget to pull that prop controll to full coarse pitch ASAP.

MTV

I understand why you would do this in principle, but on a non-feathering constant speed prop isn't it impossible to keep the prop at the coarse pitch stops as the engine quits turning? The flyweights are going to bring it back to the low pitch stops as oil pressure decreases as the engine slows down.

Yes, but if you can get the prop to stop, then the drag is reduced by the propeller not windmilling.

Barry Schiff discussed this too. His thought was that if you could slow the airplane sufficiently to stop the propeller, and then resume best glide speed, your glide range could be extended. According to a bit of my memory, and my reasoning, you would employ this technique only if you had lots of altitude. You have to spend enough time gliding after slowing, stopping the prop, and accelerating to cancel the loss of altitude suffered in the manuever, and then reap the return on your investment in that following the point where you just break even on the drag saved vs. the altitude lost.

M6RV6 wrote:

bigrenna wrote:That chart is awesome. But lots to look at...... So no flaps at 80 is best glide?

Looks like 70 to me?

Im not sure.... Looks like the best data point is at 80mph / 500' per min sink (no flap) netting a 14:1 glide.

bigrenna wrote:

M6RV6 wrote:

bigrenna wrote:That chart is awesome. But lots to look at...... So no flaps at 80 is best glide?

Looks like 70 to me?

Im not sure.... Looks like the best data point is at 80mph / 500' per min sink (no flap) netting a 14:1 glide.

-425/70? Longest time in air. the 80/500 farthest glide??

M6RV6 wrote:

Scolopax wrote:

mtv wrote:Hot rod,

If you are ever faced with that discouraging feeling caused by an engine failure, don't forget to pull that prop controll to full coarse pitch ASAP.

MTV

This action makes a difference in drag that is hard to believe.

There is no #!! wieght makes it move.
Pull the prop and screw the trim all the way nose up, should get you as far as you can get.

I had an instructor show me this technique during a BFR a couple years ago in a 172. It was a 79 model or so. Full nose up trim was close enough to best glide speed to not have to think anymore about it than that.

bushpilot490 wrote:

mtv wrote:Hot rod,

If you are ever faced with that discouraging feeling caused by an engine failure, don't forget to pull that prop controll to full coarse pitch ASAP.

MTV

I understand why you would do this in principle, but on a non-feathering constant speed prop isn't it impossible to keep the prop at the coarse pitch stops as the engine quits turning? The flyweights are going to bring it back to the low pitch stops as oil pressure decreases as the engine slows down.

Who says the engine will stop turning? Unless the engine failed due to a catastrophic internal failure that will grind things to a halt, the engine will likely continue to turn, UNLESS you intentionally stop it by slowing.
That may indeed be a good plan, if you have sufficient height and are comfortable doing so.

But, getting that propeller to coarse pitch will reduce drag considerably, while the engine is still turning. And, the engine is turning BECAUSE the propeller is driving it in the air flow. You now have a windmill (note the reference: "windmilling propeller"). The easier you make it for a given airflow to turn that engine over, the less drag you're going to experience.

MTV

I suspect Glidergeek is getting a chuckle at our expense…

M6RV6 wrote:

bigrenna wrote:Im not sure.... Looks like the best data point is at 80mph / 500' per min sink (no flap) netting a 14:1 glide.

-425/70? Longest time in air. the 80/500 farthest glide??

For a stol guy, best glide can be very counter intuitive… As slow as you can be, can be bad, as light as you can be, can be bad, and headwinds are the antichrist.

Yes re the chart bigr is correct, because in this context we are looking for distance, not time. Longer in the air won't yield that distance at a speed too slow. Best glide (LD max) for most of these airplanes will occur somewhere between Vy and Vx, since these two speeds will change with mods and drag, they will conveniently change your best glide speed to match. Knowing those speeds is going to be tremendously more efficient than trying to reference a chart, and likely far more accurate. Remember, best glide, unlike some other 'V' speeds is going to be fluid. It will change (sometimes dramatically) with weight, and will be faster as you get heavier (remember gliders have ballast to address this). And again, the headwinds that make us look like rockstars on landing will have a tremendous impact on our engine out gliding DISTANCE (not speed). Lastly, every mod you do to change the lift, or drag profile (this essentially means EVERYTHING we do to our airplanes) will effect your best glide… after all it occurs at LD Max. Consequently, if the rule of thumb I suggested isn't accurate enough for you, using a chart developed for a bone stock airplane (or any airplane other than yours) isn't going to yield any more accuracy. In this case I'd suggest a beautiful spring morning spent over a dry lake bed or malpais flat. It can be a very enjoyable way to increase your skill and consciousness of exactly what your airplane is capable of.

And yes to MTV's suggestion of pulling the prop, IF the engine doesn't lock up, and IF you didn't dump all of your oil overboard (two common occurrences in a full blown engine out), you will enjoy a much greater glide distance / speed by pulling that prop. But again, my suggestion would be to plan on pulling it, but don't paint yourself into a corner banking on it responding.

Lastly, IMHO while knowing your best glide is golden information, in a full blown engine out scenario, picking the safest place to park it immediately, is a far better plan than 'knowing you can glide "X" miles and then coming up a skosh short due to one of the zillion things that can affect your best glide, consequently parking it on the street in front of the airport

Take care, Rob

Rob wrote:.... Consequently, if the rule of thumb I suggested isn't accurate enough for you....

I guess I missed the rule of thumb you suggested?
Was it the "somewhere between Vy & Vx" comment?
Per the C180 owner's manual, sea level best rate is listed as 87 - 90 mph.
Best angle is listed as 70.
So I'd guess best glide speed is 80-ish.
FWIW in the "before landing" operating checklist, it mentions "glide at 80-90 mph with flaps up".

hotrod180 wrote:

Rob wrote:.... Consequently, if the rule of thumb I suggested isn't accurate enough for you....

I guess I missed the rule of thumb you suggested?
Was it the "somewhere between Vy & Vx" comment?
Per the C180 owner's manual, sea level best rate is listed as 87 - 90 mph.
Best angle is listed as 70.
So I'd guess best glide speed is 80-ish.
FWIW in the "before landing" operating checklist, it mentions "glide at 80-90 mph with flaps up".

But "per the owner's manual" is pretty much out the window for most of us here... For example, according to Willie, with a Sportsman: Vx => 53mph with 30deg. of flaps and Vy => 80mph. Add WingX, bubbles, big tires, etc etc etc and who the F knows....

I am going to side with a combination of MTV - ROB - & Big Renna.

PLUS add in that VX rises towards VY as alt. and temps. rise. SO, yer glide speed will be different at ten thousand feet on a hot 100 degree day than it would be at the almost useless book speeds that do not apply to most of our planes.

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.

Trim