Glide ratio

Richard

Richard

Final Approach
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Given: single or twin engine piston for personal flight. Terrain may or may not be mountainous. To keep it simple, overflight of water is not a consideration.

Is the glide ratio of the aircraft you fly a factor in determining your altitude during flight planning?
 
Richard said:
Given: single or twin engine piston for personal flight. Terrain may or may not be mountainous. To keep it simple, overflight of water is not a consideration.

Is the glide ratio of the aircraft you fly a factor in determining your altitude during flight planning?
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Nope.

To be interesting, make it mountainous and over water, and the answer is still no.
 
Richard said:
Given: single or twin engine piston for personal flight. Terrain may or may not be mountainous. To keep it simple, overflight of water is not a consideration.

Is the glide ratio of the aircraft you fly a factor in determining your altitude during flight planning?
Click to expand...

When I was flying single engine aircraft over Lake Michigan, you betcha. With a twin it's not a dominant factor for my planning but it occasionally does get some consideration. Also I have on occasion, looked at drift down (descent from above the SE absolute ceiling on one engine) data when planning a flight in the mountains but this information is tough to come by for light twins.
 
Richard said:
Given: single or twin engine piston for personal flight. Terrain may or may not be mountainous. To keep it simple, overflight of water is not a consideration.

Is the glide ratio of the aircraft you fly a factor in determining your altitude during flight planning?
Click to expand...
In a single, yes....
 
Richard said:
Given: single or twin engine piston for personal flight. Terrain may or may not be mountainous. To keep it simple, overflight of water is not a consideration.

Is the glide ratio of the aircraft you fly a factor in determining your altitude during flight planning?
Click to expand...

If I'm not flying over water, no.

Over Lake Michigan, the lowest I've done it in a single is 12,000 feet. I also calculate the turn-back point based on actual winds aloft after I get up to 12K+.

Over land - Well, just fly where there's something landable within glide range at all times. Even in the mountains, that's not really all that hard - There's usually a river or a road at the bottom of the slope.

Now I normally will go at least as high as the first >3000 AGL VFR cruising altitude, but it all depends - like everything else in aviation. :yes:
 
Richard said:
Given: single or twin engine piston for personal flight. Terrain may or may not be mountainous. To keep it simple, overflight of water is not a consideration.

Is the glide ratio of the aircraft you fly a factor in determining your altitude during flight planning?
Click to expand...

If there's inhospitable terrain involved, then yes. But I wouldn't place myself in terribly unfavorable winds that would make range/endurance an issue, just for gliding distance sake.


Trapper John
 
Only once, last February. The temperature was single digits *F and I took a detour of about 30 miles to stay over or within gliding distance of some islands instead of crossing straight over Block Island Sound. The water temperature would have been lethal within a few minutes and there were no conveniently located boats to ditch next to.

-Skip
 
In singles I seldom think about glide ratio, but I will often deviate from a direct flight to keep more landable areas within range.

In the glider I think about it mostly because the glide angle is so flat I can often glide to locations that are out of sight. I also occasionally fly in areas where it can be 20 miles or more to the nearest landable area. Doing the math (or letting the computer do it) is the only way to ensure I don't get into a corner I can't get out of.

Brian
CFIIG/ASEL

http://www.soaridaho.com/photogallery/Mackay_2006/images/IMG_0703.jpg
 
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Yes,
and I adjust my route to minimize the time where the options are poor. Isn't this just basic risk management?
 
i love barbs approach to flying over inhospitable terrain :)
 
Here we have some terrain that is not very desireable place to land(or crash) so on some flight I make sure that I have enough altitude to glide somewhere better than I am at. When coming from any airports down south to Kiza it takes me between the two mountain ranges so I always make sure I can get over the mountain back to the coast in case of an engine out. Ocean is much better than the riverbed at the bottom of the canyon. And always remember that a plane with and engine out will glide all the way to the scene of the crash if all else fails.
 
Why I asked:

I watched a DA-20 climbing for altitude after takeoff. This after talking to the transient pilots to say for a scenic tour (which they wanted) there was no reason to climb above 1,000 field elev since the aprt is on a mesa with lowering terrain all around. Yet they continued to climb. I suspect they continued to climb out of habit rather than 'local' knowledge imparted to them. (After they returned they did say they descended to the recommended alt)

Then I thought about the C-207 I fly which has a glide ratio of a brick. Naturally I started to think of other aircraft and other glide ratios.

Of course, conventional wisdom dictates that altitude is your friend. It seemed to me the DA-20 continued the climb in adherence to the conventional wisdom which caused me to think this was borne of habit. And this brought me to the Q.

BTW: I take exception to Kent's reasoning that a road or river is most probably at the bottom of a valley. Don't count on it. Even if there is a river (a huge assumption) the river may be chockablock full of aluminum eating boulders. You will die trying to put down in that eventuality.
 
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I don't think about it extensively. When I'm in my Aztec, I especially don't think about it, but even at gross the single engine service ceiling is plenty high to keep me on IFR minimum altitudes for this half of the country.

I do have a habit of climbing higher on the basic altitude is your friend philosophy. In that case, it's less of an matter of glide ratio so much as an matter of time available. If I'm 1000-1500 AGL, in the event of an engine failure that basically gives me time to pick a spot to land and land there. If I'm 5000 AGL, that gives me enough time to pick a spot, start making my moves towards landing, and also then spend a bit of time diagnosing. When I flew out to Ames and was flying over Ohio and Indiana (this was the first time I'd spent any significant time over the flat lands), it somewhat shocked me to hear people cruising along at 2500 MSL, but that's because around here you can't do that due to terrain. Once I thought about it a bit and realized the terrain I was flying over, I then went lower since the headwinds were pretty awful.
 
Richard said:
BTW: I take exception to Kent's reasoning that a road or river is most probably at the bottom of a valley. Don't count on it. Even if there is a river (a huge assumption) the river may be chockablock full of aluminum eating boulders. You will die trying to put down in that eventuality.
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WRT rivers, it is generally a good idea to follow them (downstream) if you're suddenly flying a (lousy) glider, but that's not because the river's themselves offer good landing sites but rather that they often lead to good landing sites and virtually always run downhill (which is the preferred direction when flying a lousy glider). Roads OTOH may or may not lead to lower terrain and while in some places they offer the only plausible landing zone that's nowhere near as universal as rivers running downhill.

But your explanation also begs the question: "Would you typically climb higher/faster in an airplane with poor gliding characteristics than one that can glide a long ways?" I don't think that's the question people answered but it sounds like that's what you intended to ask.
 
gismo said:
But your explanation also begs the question: "Would you typically climb higher/faster in an airplane with poor gliding characteristics than one that can glide a long ways?" I don't think that's the question people answered but it sounds like that's what you intended to ask.
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Alttitude can be good no matter what the L/D - if weather permits. But when you are scud running, you are scud running...
 
Capt. Geoffrey Thorpe said:
Alttitude can be good no matter what the L/D - if weather permits. But when you are scud running, you are scud running...
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Ah, but in some airplanes (my Baron for instance), rapid altitude gain requires sub-optimal pitch attitudes for operation near the ground. So while altitude is normally friendly, obtaining it can turn loose some enemies.
 
jmaynard said:
What, you don't like 1500 FPM in normal climb?
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I don't like having to pitch down 30 degrees and then flaring if an engine quits early in the takeoff. 1500 FPM is achievable while still being able to see the horizon at the weight we were flying in cool air. :)
 
Richard said:
BTW: I take exception to Kent's reasoning that a road or river is most probably at the bottom of a valley. Don't count on it. Even if there is a river (a huge assumption) the river may be chockablock full of aluminum eating boulders. You will die trying to put down in that eventuality.
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Two things:

1) Boulders in a river aren't that much concern to me, if they're not obvious from above (meaning they're not above the surface or just a few inches below.) Landing on water, you're probably going to throw up some rooster tails, slow down VERY quickly and start sinking in as you slow down, and I don't think a non-obvious boulder is going to do much to you except maybe rip the gear off the plane and turn you - and at that point, I really don't care. Above the river or high in the water, it might flip you over or stop you fairly suddenly, but I don't think it's got a high likelihood of killing you during the landing.

2) In mountain flying, navigation is extremely important - You don't want to fly up the wrong canyon, because you might not get back out. With that in mind, it's a good idea to choose canyons with roads and rivers for navigation purposes. Also, if you get lost or are less than 100% sure of where you are, don't fly into a canyon without active water in it, as it is much more likely to be a box canyon. A canyon with water had to get that water from somewhere, and that probably means that there's enough room in it to be able to climb out (gotta have enough area with enough snow melt all running into the same place to create that stream of water in the first place).
 
Ted DuPuis said:
I do have a habit of climbing higher on the basic altitude is your friend philosophy. In that case, it's less of an matter of glide ratio so much as an matter of time available. If I'm 1000-1500 AGL, in the event of an engine failure that basically gives me time to pick a spot to land and land there. If I'm 5000 AGL, that gives me enough time to pick a spot, start making my moves towards landing, and also then spend a bit of time diagnosing.
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Yep, that's why I like to fly low. You won't have to think about it as long before you come back to earth! :yikes:

Barb
 
One Short said:
Yep, that's why I like to fly low. You won't have to think about it as long before you come back to earth! :yikes:
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Ahh Barb, but I love your flying! From whom else do you hear:

"Climbing to pattern altitude"

:D
 
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