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glide ratio

5 to 7 to 1. Unfaired gear? Big or small tires? I do know that when I dead stick ridge soar for an hour or two, one notch of flaps helps. Fans S-7 FWIW
 
I once measured a loaded, stock, 65hp j-3 as about 7:1.

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A 727 will make it from over Providence at 10,000 feet to Boston with the throttles at idle, 42 miles! That's 22/1. :lol:
 
Has anyone figured the glide ratio of there cub? max gross sea level 70 degree day?
I haven't, and knowing so wouldn't make a difference in any practical situation given the variables. In an engine-out situation I'd be at best-glide and (here in Southern Appalachia) consider bar-room Roses sites.
 
Not trying to be smart here but why glide ratio at sea level? Aren't you already on the ground at that point?

Jerry
 
Just giving a reference, air density and TAS will very with altitude.

I was curious if you are looking for a practical number to hang your hat on or just a reference to put into a POH. The only place glide ratio has relevance in my flying is my summer flying which is mostly over water. I have settled on one mile per 1000 ft msl which gives me a simple way to estimate point of no return altitudes for water crossing. So if I have 16 miles of water to cross my crossing altitude at mid point is 8000 ft. I like it simple and practical and figuring a good practical figure to use is quite straight forward.

Other than water crossings that require a bit of altitude to make it safely to shore most of my flying is too low to rely on any glide ratio calcs so I just use many hours of engine out practice to make that lonely feeling go away when the prop stops.

Jerry
 
Have a look in Members area - Tech Articles - PA18 Flight Manual report 1054 - page 42 and 43.

Glide ratio can be worked from there for a Stock SC. - approx 8.9 : 1

Frank
 
Best glide speeds themselves are of little practical value, especially in slow airplanes. Even the average wind is a large percentage of a Cub's speed. Knowing the distance covered over height loss under given wind conditions as well as the sink rate at all speeds is a lot more useful. You might have to slow up to minimum sink rate speed - about half way between stall speed and best glide speed - (in a tailwind), or push the nose down (in a headwind) to get the best distance.

A 10K component in SC at best glide speed (58 mph) costs or buys about 20% distance. A 50K headwind means you'll be coming down vertically (actual glide ratio 0:1). But if you pick up your speed, you'll cover ground. Better yet, of course, is to look for a field downwind.

My 2c.
 
... I have settled on one mile per 1000 ft... mid point...

Sounds like a good rule of thumb, Jerry, though I would qualify it a bit.

The stock SC's sink rate, in round numbers, at 60 mph is 600 fpm and its descent gradient in still air is, consequently, 600' per mile. So 8000' AGL buys about 13 minutes and 13 miles under those conditions. No problem going either way from a midpoint in still air. It should keep your our feet dry even with a 20K component. If more than 20K, however, I'd move my minimum crossing height (or Decision Point if crossing in level flight) closer to the upwind shore, adjust my glide speed, if needed, or any combination thereof. E.g., a 25K headwind will cut my ground speed in half. If the engine quits midway, that will put me in the water 2 miles short of the upwind shore - whichever it is. To stay dry, I could move my 8000' (or Decision Point) 3 miles closer to the upwind shore (time and distance to the downwind shore would not be an issue in this case, even from over the upwind shore). Or I could improve my chances for dry feet by increasing my speed to, say, 95 mph and take the higher sink penalty. At about 1100 fpm sink rate (used here only as an example), I could just make landfall. As an added benefit, I would spend less time in strong headwinds (I get lower sooner), time - and distance - I can use to find an adequate field or shoreline.

A consideration often overlooked is the climb gradient to the planned crossing height under the conditions - e.g., climbing on course over water in a tailwind. If the climb gradient is less than the estimated worse case decent profile to at least one adequate field, then a racetrack climb will be needed to stay at or above at least one of those profiles throughout the climb. As an aside, planning the decent to a field near or on an upwind shore is also worth the effort. Starting down early (e.g., to bring CHTs down slowly) in such cases is to court Murphy's law, too. The smart money says descend in a racetrack, if needed, staying within gliding range, preferably upwind, of the field.

Don't get me wrong. I don't suggest these mental gymnastics at a time when stress levels are already high. The point I'm trying to make is that ball park figures ought to include validity limitations when warranted. So my suggestion is to append "... for wind components up to 20K. For on course climb, 600 fpm ROC minimum and no tailwind" to your rule of thumb. (I use ROC here instead of climb gradient because it's readily available off the VSI and always meets or exceeds the required 600' per mile climb gradient.)
 
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