Best glide speed and glide ratio?

[Diana]

I can’t find these numbers for my Citabria, and I looked for them on the placards and in the Pilot’s Operating Manual. Where else might I find the numbers?

My previous Citabria instructor told me to use 70 mph as best glide, and the book says for forced landing to trim the aircraft to the “recommended glide”, but they don’t specify what that is. Later the book mentions 60-65 mph, but they don’t specify that as best glide.

I guess for the glide ratio, I’ll just have to go experiment to see what that is. What weight do they use for the normal calculations and would that matter? Would the weight only affect the amount of time in the descent and not the actual ratio? The winds would have to be factored in as well. What else should I plan for, in checking this?


Thanks.

 

[spiderweb]

I'll take a stab at this:

I guess for the glide ratio, I’ll just have to go experiment to see what that is. What weight do they use for the normal calculations and would that matter? Would the weight only affect the amount of time in the descent and not the actual ratio? The winds would have to be factored in as well. What else should I plan for, in checking this?

I don't know how you would do the experiments on your own, but I do know that 1) weight affects best glide speed, and 2) winds do not, although they would affect where you want to land.

 

[Ken Ibold]

The Citabria POH/AFM is a piece of junk, isn't it? The 1979 book I have has performance charts, but my 2001 book doesn't. Go figure.

Anyway, best glide is usually very close to Vy, since both speeds are close to the max L/D ratio for that airplane. Vy in your airplane is 69 mph. (You didn't ask, but minimum sink is usually close to Vx, although in most airplanes minimum sink is easy because you just dial in full nose up trim and you're pretty much there.)

Note, though, the rather large difference between IAS and CAS in Citabrias at the low end. 70 mph indicated is 75 calibrated, by the book. Shoot for 66 indicated.

 

[Diana]

I'll take a stab at this:

I don't know how you would do the experiments on your own, would affect

Ben, I was going to try to figure out the glide ratio by using the best glide speed (which I think will be 66 indicated) and flying with the throttle back, prop windmilling and mark the ground distance and altitude lost, while factoring in the winds. Wouldn't that give me a rough estimate of the glide ratio?

 

[Diana]

The Citabria POH/AFM is a piece of junk, isn't it?

LOL! Yes, it is. At least I can get the new placards from ACA now.

Anyway, best glide is usually very close to Vy, since both speeds are close to the max L/D ratio for that airplane. Vy in your airplane is 69 mph. (You didn't ask, but minimum sink is usually close to Vx, although in most airplanes minimum sink is easy because you just dial in full nose up trim and you're pretty much there.)

Note, though, the rather large difference between IAS and CAS in Citabrias at the low end. 70 mph indicated is 75 calibrated, by the book. Shoot for 66 indicated.

Thanks Ken, I knew you'd know. Do you have the glide ratio in your book? How would you go about finding it yourself?

 

[Ken Ibold]

Do you have the glide ratio in your book? How would you go about finding it yourself?

Nope, not in my book.

I'd use about 10:1 because in "The Advanced Pilot's Flight Manual" Bill Kershner gives 10:1 for a J-3 (page 108), and that's close enough for gov't work.

 

[Rob Schaffer]

The 7GCBC Model I did my Tailwheel in, Best Glide / "Recommended Airspeed" was 65 mph.

 

[Baron2PG]

SuperCub is nominally 65MPH as well. But as both the SuperCub and the Citabria are very light aircraft the amount of fuel, baggage and people probably move that figure +/- 5 MPH or more.

Get a handheld GPS, climb to 5000 feet and figure it out.

 

[CJones]

HOLY COW!! This could possibly be the OLDEST thread every resurrected!

 

[Richard]

HOLY COW!! This could possibly be the OLDEST thread every resurrected!

And our most famous necroposter was not involved.

 

[Diana]

HOLY COW!! This could possibly be the OLDEST thread every resurrected!

Yep.

 

[Matthew]

Well???

Don't keep us waiting!

Did you get an answer?

 

[blazer003]

No answer. He must have come up short... :wink2:

 

[flyingcheesehead]

HOLY COW!! This could possibly be the OLDEST thread every resurrected!

Yep.

Nope.

 

[Diana]

Well???

Don't keep us waiting!

Did you get an answer?

Sorry, I missed this one.

I'm going with 68 MPH.

 

[gismo]

No answer. He must have come up short... :wink2:

One thing for sure, if Dianna had started gliding downhill when this thread was first started, she'd definitely be on the ground by now no matter what she used for best glide.

 

[Diana]

One thing for sure, if Dianna had started gliding downhill when this thread was first started, she'd definitely be on the ground by now no matter what she used for best glide.

I WAS going to post that for best glide now I just close my eyes, listen to the airplane, and become the airplane. :yinyang:

 

[Ken Ibold]

I WAS going to post that for best glide now I just close my eyes, listen to the airplane, and become the airplane. :yinyang:

I worked for Rocky the Flying Squirrel.

 

[gismo]

It worked for Rocky the Flying Squirrel.

Fixed it for ya.

 

[Ken Ibold]

Fixed it for ya.

Oh yeah, gee, thanks! I never personally worked for Rocky the Flying Squirrel, although I did once work for Toonces the Flying Cat. (well, donkey is more like it, if you know what I mean.)

 

[Diana]

I worked for Rocky the Flying Squirrel.

Fixed it for ya.

Thanks, Lance.

I was having the hardest time trying to figure out what Ken was saying and tried to relate it to what I was saying. I even wondered if Bullwinkle had something to do with it, like maybe he worked for Bullwinkle, too. Never woulda thought about that missing 't'.