Glide Ratios

SixPapaCharlie

SixPapaCharlie

May the force be with you
Joined
Aug 8, 2013
Messages
16,415
Display Name
Display name:
Sixer
I have a friend that flies a 235 and we were talking Saturday and he remarked that "You really have to carry power all the way down. If you kill the power it drops like a rock"

I am used to lighter planes where you pull power at some point during landing. I would have guessed that any plane would have the ability to power off, glide, flare.

What is considered good, typical, and bad glide ratio and some example aircraft?

Thanks.
 
I actually enjoy landing airplanes with a little less L/D / higher wing loading. The Sonex is a good example. If you slow to 70 knots and cut the power turning base, you'll end up short. My preferred method is holding 100MPH in a descending turn, bleeding airspeed short final, and just a touch of power on touchdown for a smooth landing. I try to fly the 152 or Cherokee like that and it's just not the same, it will float forever without an aggressive forward slip. Maybe it's the helicopter pilot in me, but a 10 minute approach floating all the way down from 1000 AGL at 70KTS is boring.

Maybe one day I'll be as good as Whifferdill, he flies some sweet approaches!
 
Last edited:
Bryan tell your friend he sucks at energy management. That isn't all of it but is a part.
 
My Mooney has a glide ratio of 10.7:1 with the prop turning. I routinely pull power to idle on final. At my former home field, I would go to idle between when the numbers came into view and when I cleared the trees. Runway was 3000', and I was never near the end despite minimal braking.
 
SixPapaCharlie said:
I have a friend that flies a 235 and we were talking Saturday and he remarked that "You really have to carry power all the way down. If you kill the power it drops like a rock"
Click to expand...

It does, with full flaps. That's what I fly... but you don't need to carry power all the way down if you don't want to; just start higher up.
 
Average for a small plane is about 10:1 less than that is bad more than that is good. Real high end gliders can get around 50:1, even the average ones get around 30:1.
 
The swift is a freaking brick. Power off 180's are a cinch. Problem is when you get in the pattern with some yahoo flying a super wide pattern and you have to adapt. It's uncomfortable knowing if the engine quit you're going into the trees.




Sent from my iPhone using Tapatalk
 
Power off glide ratio in the enclosed side by side gyroplane I fly (Autogiro Cavalon) is around five to one even though it is listed at three to one in the POH.
The one of a kind open tandem gyroplane I fly it is closer to three to one.
I usually land with a little power to hit my spot but regularly practice engine at idle landings.
 
I was shocked at how good the Caravan's glide is. Depending on pod or no pod, it's a 12-14:1 ratio. The first time I actually tried landing with it feathered, I just couldn't bleed off that speed and floated a couple thousand feet.
 
My Zenith 801 had a glide ratio of about 3-1.... On a good day..:hairraise:
 
IIRC, the 235 is something like 7:1 glide ratio. In other words, you cut power...you are a rock with Hershey bar wings. :)

In my experience as well the 235 likes a little power all the way down. During my training I got to where I could do a respectable landing cutting power once I knew I had the runway made...but the squeakers in the 235 come with a tich of power and you pull what's left as soon as you hear/feel the chirp. If I was coming in power off as someone already mentioned, I'd just come in higher with a more abrubt flare...it worked but even my CFI who had (albeit many years prior) owned a 235 had to work a lot harder to deliver a 'commercially' acceptable landing that way vs just leaving in a bit of power.

For those with experience flying the 235...well, more experience than my 400 or so landings in one...you'll hear a common theme there.

And keep in mind too, that glide ratio is independent of weight. It remains constant as weight changes. Best glide speed changes with the ratio of the square root of weight divided by gross weight.
 
Last edited:
You can pull power @ the numbers and still make the runway with room to spare.
 
ive seen the same here in my PA-32-260. Definitey glides like a brick but if you are flying a relatively normal pattern power off shouldnt be too much of a problem. that said, a little power helps make the landing less "memorable"
 
"...you are a rock with Hershey bar wings"

+1 on that!!!
 
SixPapaCharlie said:
I would have guessed that any plane would have the ability to power off, glide, flare.
Click to expand...
That's true, but as you move into heavier and faster aircraft, the descent rate goes up, the glide angle starts to get steep, and you need greater and greater precision for both for the point at which the flare is started and the rate at which the flare is accomplished (or you either fail to get the nose up enough and smash into the runway nose first or get on the back side of the drag curve before you touchdown and smash into the runway butt first). If you want to get an idea of what that's like, go sit near an F-16 training base and watch the simulated flame-out (SFO) approaches, or see the discussion (with pictures) here. Note that the SFO glide path for the Viper is 11 degrees compared to the normal 2.5-3 degrees.
 
Last edited:
dell30rb said:
The swift is a freaking brick. Power off 180's are a cinch. Problem is when you get in the pattern with some yahoo flying a super wide pattern and you have to adapt. It's uncomfortable knowing if the engine quit you're going into the trees.
Click to expand...
I guess you never fly more than a couple of miles from the nearest runway.
 
SmashTime said:
You can pull power @ the numbers and still make the runway with room to spare.
Click to expand...
Depends what you're flying and how high you fly the pattern. For example, with the gear/flaps down, a Glassair III loses 2000 feet making a 180 degree turn. Unless you fly a pattern like that F-16 SFO (and that creates a lot of other problems), if you lose the engine at any point after extending the gear, you are not making the runway.
 
Dropping like a rock isn't how I would describe the Navion power off approach, because it never really achieves that sort of speed. The approach angle however with power off, full flap, and the gear out is a bit steeper than most people feel comfortable with. It does allow you to get in to some tight places (and yes given the wing and the amount of power in mine, get out of them as well).

As C'Ron alludes, you're going to be further than gliding distance at some point. Don't know of many planes that will make the runway without power on a 3 degree glideslope for sure.
 
My Arrow drops like a rock once the gear and flaps come down.
 
In a 172 I would conservatively expect 1 mile per 1,000' AGL (~5:1) for emergency purposes. Any extra was margin for pilot shock and ineptitude.
 
Direct C51 said:
I actually enjoy landing airplanes with a little less L/D / higher wing loading. The Sonex is a good example. If you slow to 70 knots and cut the power turning base, you'll end up short. My preferred method is holding 100MPH in a descending turn, bleeding airspeed short final, and just a touch of power on touchdown for a smooth landing.
Click to expand...

So you found a Sonex? If so, congrats!

dell30rb said:
The swift is a freaking brick. Power off 180's are a cinch. Problem is when you get in the pattern with some yahoo flying a super wide pattern and you have to adapt.
Click to expand...

Ren, if you have to adapt to a bomber pattern guy then you're still flying your pattern too big. haha :) Yeah, you need to get into that Pitts. You can stuff it in twice as steep as the Swift and fly inside the bomber guys all day long.
 
Ron Levy said:
I guess you never fly more than a couple of miles from the nearest runway.
Click to expand...

Actually no, i'm usually not. There are 7 airports within 12 miles of me right now according to foreflight.

At my home field there are plenty of farms surrounding the airport that would make a good landing spot if the engine failed while in the pattern. But yesterday I was at an airport in the foothills and following behind a guy flying a ridiculous pattern in a 172. I was flying a base leg, miles from the threshold with gear and flaps down, nothing around me but hills and trees and no hope of making the runway from that far out.
 
14:1 glide ratio for the Lancair 360 (clean configuration, ~100kts, prop all the way back).

This assumes you have oil pressure to get the prop back, of course.
 
Its sort of funny My Arrow with Gear and Flaps down seems to have the Autorotation qualities and sight picture of flying a UH-1...not a brick like an Apache but when getting qualified my CFI was amused my love of power off 180's...but it does come down much quicker than most...
 
Power off landings are a bit of my specialty. Perhaps this is due to nearly a 1000 hrs in gliders. Or perhaps it is due to doing a lot of instruction in slow airplanes like cubs and champs where getting around the pattern quickly allows you to fit into the pattern with faster aircraft.

Of the 90 some different types of single engine planes I have flown only the Cherokee 6 and Bellanca Viking were the the ones that I thought were actually a bit challenging to to do power off landings in. The Viking manual recommends pulling the prop back to low RPM which helps a lot (for emergency procedures) I don't recall if the Cherokee 6 made this recommendation as well, but of course it would help.

The descent rate has a lot more to do with how the plane lands power off than does glide ratio. My glider with full flaps has a 2:1 glide ratio, but is very easy to land as it touches down at about 25kts and the descent rate is still pretty low.

One of my pet peeves is pilots complaining about how steep of approach or how high their descent rate is with full flaps. That is sort of the point of full flaps. If the descent rate is to high, use less flaps. To many pilots think flaps are just to be extended for landing and really have no idea how to actually use them. I haven't found an airplane yet that isn't actually easier to land power off with no flaps. Some do trim out better with about 10 degrees of flaps. It is also true it will use more runway, but probably not more that 20% more.

The faster your airplane descends you may have to increase your approach speed (often about 10kts) so you have enough energy to flare with, By the time you touch down the airspeed will have bled off to about your normal touch down speed.

You may have to actually learn how to fly the airplane in ground effect. I am surprised at how many pilots have trouble actually just flying a couple feet off the runway while excess speed decays. They either start getting into PIO's, or balloon or try to plant it onto he runway early when all they really need to do is smoothly bring the nose up until the plane touches down on the mains (nose up attitude).

If you are flying a plane that does come down quickly it is probably even more important to practice power off approaches, since in a emergency it will be more challenging and require more skill to successfully make an emergency power off landing.

Brian
CFIIG/ASEL
 
My CTSW has a light wing loading and low inertia due to the low weight. It glides well, but it's pretty steep with the flaps in. I fly a very close pattern because of this, if the engine quits it will come down pretty steeply, and it's easy to misjudge and come up short on final. I try to come in slightly high and adjust with a slip if needed, but sometimes I have to add a little power on final to make the runway.
 
brcase said:
If you are flying a plane that does come down quickly it is probably even more important to practice power off approaches, since in a emergency it will be more challenging and require more skill to successfully make an emergency power off landing.
Click to expand...

Big +1. The fact is that most light GA singles that 95% of pilots are flying can easily fly power off approaches and landings. But these days many (most?) pilots seem uncomfortable with descent rates greater than what you see flying a 3 degree powered approach in a 172 at 70kts with half flaps because that is how they are trained. It seems silly to many of us because this same 172, power off, 60KTS, and full flaps still has an extremely low and tame descent rate compared to many other types. Pilots have widely varying comfort levels. Those with low comfort levels should seek to expand their skills with a (good) instructor. It's all about proper airspeed and energy management. You do not need to "arrest" the descent with power in most light singles. That's a pilot crutch thing for most due to the desire to stay inside a very narrow range of the performance envelope. It doesn't cost you anything to practice power off landings. But it will sure pay you back when you need to put it in a field in an emergency.
 
Pretty much every landing is a power off landing for me. I play the game of pulling the power abeam the numbers and seeing if I can land on the numbers without adding power or slipping. Don't always succeed, but its fun to try, and rewarding when I do it right. Great practice for emergency landings too.
 
dell30rb said:
Actually no, i'm usually not. There are 7 airports within 12 miles of me right now according to foreflight.
Click to expand...
So you never get more than 12 miles from home? That won't work for most pilots in 99% of the airspace in the USA.

At my home field there are plenty of farms surrounding the airport that would make a good landing spot if the engine failed while in the pattern. But yesterday I was at an airport in the foothills and following behind a guy flying a ridiculous pattern in a 172. I was flying a base leg, miles from the threshold with gear and flaps down, nothing around me but hills and trees and no hope of making the runway from that far out.
Click to expand...
So what? I'll bet if we tracked it, you've probably spend more than 95% of your flight time out of gliding rage of an airport, and a substantial portion out of gliding range of anything one would call a "suitable landing area" for a 172. There is simply no data showing the engine is more likely to fail in the traffic pattern than anywhere else, making the idea of "always stay within gliding range of the runway when in the traffic pattern" a pointless precaution if you're happy flying out of gliding range of a runway all the rest of the time you're airborne.
 
A Pc12 will go just over 2 miles for every 1k

185 amphib 1 mile for 1k

A PA28 should be able to be landed with no power, no problem.

I've never flown a plane where I NEEDED power to land smoothly, white I've added it at times when I was still new to the plane, or if I got a little gust or something.
 
coloradobluesky said:
Pretty much every landing is a power off landing for me. I play the game of pulling the power abeam the numbers and seeing if I can land on the numbers without adding power or slipping. Don't always succeed, but its fun to try, and rewarding when I do it right. Great practice for emergency landings too.
Click to expand...

What's wrong with slipping?
 
Ron Levy said:
So you never get more than 12 miles from home? That won't work for most pilots in 99% of the airspace in the USA.

So what? I'll bet if we tracked it, you've probably spend more than 95% of your flight time out of gliding rage of an airport, and a substantial portion out of gliding range of anything one would call a "suitable landing area" for a 172. There is simply no data showing the engine is more likely to fail in the traffic pattern than anywhere else, making the idea of "always stay within gliding range of the runway when in the traffic pattern" a pointless precaution if you're happy flying out of gliding range of a runway all the rest of the time you're airborne.
Click to expand...

Now you've given me something to do this evening before the monday night game kicks off. I bet you're completely wrong!

Considering a NA piston single performs best between 6-8000 feet you have about a 10nm gliding range using a 10:1 ratio. Figure that as 6000 AGL average, so 60,000 feet gliding range. about 6k feet in a NM.

Now go to skyvector.com and plan out KTTA-KMTV (my flight yesterday). Look at the 7nm rings around the public airports. In your mind, extend them to 10nm. Now estimate the percentage of your flight along that course that resides within the 10nm rings around the public airports. Does that look like 95% to you??

Now zoom in and count all the airparks and private strips. If you count the ones over 2000', I was within gliding range of an airport for nearly my entire trip.

Now go to google maps and look for all of the BIG agriculture fields. Farming. Kind of a big thing around here.

:rolleyes2:
 
Last edited:
warthog1984 said:
...even a 767 will glide decently...
Click to expand...

The 767 and most commercial jetliners have glide ratios in the 16-20:1 range which is better than just about any GA aircraft. Glide ratio however, or what we refer to as best glide, is an ideal and you wouldn't want an airplane that couldn't come down any faster than that. So at slower speeds and with flaps and such you can obtain much steeper controlled descents and that isn't considered a bad thing. It can be counter intuitive to a low time or student pilot however who rolls out onto final with power off and realizes he is way too high to pull back on the yoke and raise the nose to achieve the desired effect.

Having a "good" glide ratio doesn't necessarily mean you have a low rate of descent because it obviously depends on what your forward velocity is in relation to that descent rate. So a powerless airliner might be descending quite rapidly but it's also covering a lot of territory while doing it and therefore the ratio looks good.
 
James331 said:
What's wrong with slipping?
Click to expand...

There is nothing wrong with slipping, its just that the "rules of the game" say, if you have to slip that is one point off. If you have to add power, that is 2 points off. All from a perfect 10. (Bounces are 1 point off as well). :D

The point is, if I judge it "just right", I shouldn't have to slip. It could be argued that a slip to land on the numbers is just right, because its better to come in a little long than a little short. Hmmm. Ill have to send it to committee, might be able to get a rule change. Maybe Ron knows, he's the rules expert. :lol:
 
Last edited:
coloradobluesky said:
There is nothing wrong with slipping, its just that the "rules of the game" say, if you have to slip that is one point off. If you have to add power, that is 2 points off. All from a perfect 10. (Bounces are 1 point off as well). :D

The point is, if I judge it "just right", I shouldn't have to slip. It could be argued that a slip to land on the numbers is just right, because its better to come in a little long than a little short. Hmmm. Ill have to send it to committee, might be able to get a rule change. Maybe Ron knows, he's the rules expert. :lol:
Click to expand...

Gotcha, I've never been one to take point off for a slip, also a maneuver to practice often, as it will save your bacon at some point.
 
Ron Levy said:
Then your experience is rather limited.
Click to expand...

There are folks with lots of experience in a whole lot of different aircraft types, who have done a whole lot of different types of flying that don't necessarily include following the magenta line in bigger boring crap like Meridians or 421s or whatever else you have in mind.

I would wager YOUR experience is rather limited when it comes to many aircraft types and many other types of flying.
 
Last edited:
You must log in or register to reply here.
Back
Top