[f-AA] Champ glide ratio?

[Donald D. Walls]

ForeFlight EFB just enhanced their program with a depiction of your aircraft's potential radius of landing areas based on height above ground, the terrain, your specific glide ratio and prevailing winds. Has anyone ever computed a Champ's glide ratio? Assuming a stopped prop and optimum airspeed ( near best rate of climb speed?) it should be about the same as a C-150, but that is only a guess. It can be calculated base on distance travelled vs. altitude lost at various airspeeds, but there is no sense in reinventing the wheel if it has already been done. Anyone?
Don Walls
Sent from my iPad
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[Jerry Eichenberger]

Do you want to know best L/D or V min sink speed? Vmin sink is about 1.3 Vso. Best L/D is aboutVy.

Jerry A. Eichenberger
Eichenberger & Associates
6037 Frantz Rd., Ste. 107
Dublin, OH 43017
Voice: 614-798-1600
Fax: 614-798-1620
Website : www.ehlawyers.com
Email: jeiche...@ehlawyers.com

[Mark Peterson]

I figure 8 to 1 to be safe.... it's actually closer to 10 to 1 from what I've read.   You'd have to do a test with the prop stopped and like Jerry said, at best rate.   Tony did some actual number testing years ago so it's on the list somewhere.

"Cherish the Minnesota State Fair. Wherever you find beauty and simplicity and truth, know that there is a committee somewhere planning to improve it - don't let them do it."  
- Garrison Keillor

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From: Aeronca <aeronca...@westmont.edu> on behalf of Jerry Eichenberger <JEiche...@ehlawyers.com>
Sent: Monday, April 3, 2017 3:35 PM
To: aer...@westmont.edu
Subject: Re: [f-AA] Champ glide ratio?

 

Do you want to know best L/D or V min sink speed?  Vmin sink is about 1.3 Vso.  Best L/D is aboutVy.

Jerry A. Eichenberger
Eichenberger & Associates
6037 Frantz Rd., Ste. 107
Dublin, OH 43017
Voice:  614-798-1600
Fax:  614-798-1620
Website : www.ehlawyers.com

Columbus Ohio Aviation and Business Attorneys www.ehlawyers.com An Ohio based law firm practicing in all aspects of aviation, general business, and litigation.

[Mark Peterson]

Let me correct that..... 7 to 1.  I found one thread of the many we did on the subject:

https://groups.google.com/forum/#!searchin/f-aa/drag%7Csort:relevance/f-aa/Sy7f_gaHecI/6AHYJHNTwrMJ

Re: [f-AA] Fw: Glide Ratio of A 7AC Champ groups.google.com Posted by Jerry Eichenberger, Dec 20, 2010 3:56 AM

"Cherish the Minnesota State Fair. Wherever you find beauty and simplicity and truth, know that there is a committee somewhere planning to improve it - don't let them do it."  

[Roger Anderson]

Because of the low speed we glide at, our angle of glide is pretty steep although rate of glide might be closer to a C150 or such.   You won't cover much territory gliding at around 60.    roger

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From: "Mark Peterson" <mrpet...@msn.com>
To: aer...@westmont.edu
Sent: Monday, April 3, 2017 7:09:31 PM

[danv...@gmail.com]

The late Tony Markl tried to solve this problem by taking his L19 to altitude and measuring best the rate of descent and distance in various conditions. These included wind direction and velocity, airspeed, engine at idle, engine off, propeller wind milling, propeller stopped...  Well you get the idea.  In each test he documented his results.  Unfortunately as fas as I know he never made his data available. 

But I do recollect some of his general findings.  Among them were a caution that diving aggressively in an attempt to air start the engine without an electric starter rarely was successful. The alternative being to not try. 

Pulling the power to idle to simulate a true engine out experience is a bit unreal since the propeller turning at 500-600 rpm still provides significant thrust. So in a real event a shorter glide should be expected. 

Wind direction and strength is significant but in real life it is difficult to factor its effects into the emergency descent except in a very general way. 

His recommendation was to practice various engine out descents often and to pay attention to how your plane responds. And to be aware that the real thing will not likely be just as it was in these practice scenarios. But the more you practice the better your chances for a successful outcome. 

"Practice unusual things often," he would say. 

If Tom Holmes or Tom Roush is monitoring this thread, they most certainly would have a clearer understanding of Tony's recommendations. I just happened to be around when this subject was discussed and debated. And I don't claim and special knowledge or expertise. 

Dan v

[Galen Hutcheson]

Over 40 years of flying, I worked with licensed pilots in those types of maneuvers such as a dead engine air restart.  It is not too difficult in metal prop airplanes (though a sharp dive angle is very important) but wooden props are much harder.  On the L-16A I was flying, a near straigh down attitude is requied to get the prop rotating.  I always started the trial at least 4000' feet over the runway and, as a rule, the pilot would be hesitant to shouve the nose over into a steep dive.  I often had to take the stick and shouve the not windmilling prob almost to a verticle dive but the engine never failed to start.  Of course, it if "fuel starvation" was the cause for the engine to stop, which must be considered, then I reccommend not wasting time and altitude trying to get an airstart.  Just use the extra altitude to find a suitable landing spot and concentrate on a good glide to the field.  I prefer getting to a useable (not always the most perfect field) and the use of an agressive slip to work the plane close to the ground and recover close to the ground. I have never damaged an airplane using this maneuver.  I won't even talk about doing a deadstick landing on a starlight night in the Mark Twain Forrest flyinbg a 1929 Bird Biplane into a fescue patch and flaired when I heard the fescue hitting the gear and lower wings.  No landing is imposible, but tons of experience is required to gain the skills in these potentially dangerous situations. Remaining calm in a dead stick landing is paramount.  You do not have time to do much in the way of calcuations but you do have time to survey the best landing spot and know the wind, if you see the landing sinking If you see the landing spot rising in the windscreen, then you are not going to make the landing firld.  You must pick a field closer or you may not like the landing. On cultivated fields ALWAYS land paralled with the rows...always.

[donharvie]

This wasn't in a Champ or Chief, but rather in my Auster, (think overweight BC12 Taylorcraft).

I had a deadstick landing while giving buddy rides at a flyin last year. The engine rich cut when I reduced power to idle on late downwind.

 I confirmed that I could get power by adding air, (opening the throttle), then closed the throttle to idle and aimed directly for one third down the runway.  This was from an early base position in the circuit. With the drag from the  engine windmilling the glide was noticeably steeper - I made my touch down point and had enough energy to roll clear of the runway. (The prop stopped in the flare).

All my landings are at idle power and I habitually fly close circuits (our home airfield is in the middle of a forest). Idle power definitely extends your glide and will not give you an indication of glide with the drag of a windmilling prop.

Thanks to Tony always saying "Practice Strange Stuff"

Don H

Sent from my 'phone

-------- Original message --------

From: danv...@gmail.com

Date: 4/04/2017 1:14 PM (GMT+10:00)

To: aer...@westmont.edu

Subject: Re: [f-AA] Champ glide ratio?

[Thomas Holmes]

Yes, I'm here!  ;-)  Tony and I had some discussions around this topic!!

It's pretty easy to figure many minutes you will fly, based on whatever altitude you start at.

7:1 is pretty safe guess, at about 50 mph indicated, so for every 7 feet forward, you will lose 1 ft of altitude.  The ending distance over the ground will be modified by the prevailing wind.

That can't be duplicated with the engine at idle.

I do not recommend trying to airstart a Champ either!!  Don't ask me how I know that.

Tampa Tom

[Mark Morland]

On Mon, Apr 3, 2017 at 5:09 PM, Mark Peterson <mrpet...@msn.com> wrote:

Let me correct that..... 7 to 1.  I found one thread of the many we did on the subject:

https://groups.google.com/forum/#!searchin/f-aa/drag%7Csort:relevance/f-aa/Sy7f_gaHecI/6AHYJHNTwrMJ

​This has been an interesting thread.  Following the link above, I was rather amused at one fellow's choice to use a 60mph glide, as 55 was "too close to stall"​.  He doesn't think of Champs the way I think of Champs.

:-)

M^2

[Thomas Holmes]

If you know where the wind is coming from, you can adjust your glide speed.  I'm pretty comfortable at 50 mph indicated.

Tampa Tom

[Roger Anderson]

Whereas, I think a sailplane pilot probably really considers all of this to maximize the sailplane experience because it does make a world of difference for them, for us Champs/Chiefs, low and slow, bunch of drag, it really is just fun stuff to consider.  Whether a few mph one way or the other might slightly change sink just a bit, what you do know for sure is you will be landing in a very nearby field very shortly regardless.  And from about 2000' agl and below, it will be the first best field you see probably at no more than a 45 degree down look from where you are.  Go slow for maybe less sink rate and you don't go anywhere.  The field will still be very nearby.  Increase the speed (above about 60) and your rate of descent will super increase, but you going faster with the now higher sink rate, you will still run out of altitude  at about the same field....probably.   But...still fun to consider.   My deep thought opinion.   roger

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From: "Thomas Holmes" <thomasth...@gmail.com>
To: "f-aa" <aer...@westmont.edu>
Sent: Tuesday, April 4, 2017 8:29:57 PM

Subject: Re: [f-AA] Champ glide ratio?

[Mark Peterson]

Given the fact that a lot of pilots seem to not reach the field they aim for or stall/spin out of an engine out approach, perhaps that 55 mph was given with that in mind.   If you need that max performance out of an Aeronca to reach a field, you are running the risk higher.   If you have a lot of mental work going on, until you get to short final it doesn't hurt to have a little extra airspeed in the bank.  

Hopefully, you get to a field high enough to do some set up for a landing.   I wish Tony was still with us to give us his thoughts on 55  verses 60 verses 50.    I would like to see his data on how much the L/D changes between those airspeeds and if it makes any difference in the real world.    I think we all worry about getting caught between wishing you had just 20 feet more altitude or 10 mph more control as you get to the field.  Mushing in vs. the trees.  IMHO.  Hope we never have to use this for real.  But good to know in case.  

"Cherish the Minnesota State Fair. Wherever you find beauty and simplicity and truth, know that there is a committee somewhere planning to improve it - don't let them do it."  

- Garrison Keillor

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From: Aeronca <aeronca...@westmont.edu> on behalf of Thomas Holmes <thomasth...@gmail.com>
Sent: Tuesday, April 4, 2017 6:29 PM
To: f-aa

Subject: Re: [f-AA] Champ glide ratio?

[Jerry Eichenberger]

As a glider pilot, let me throw out some very elementary stuff.  There are 2 speeds of concern, best L/D, which is usually the speed quoted in airplane POH’s as best glide.  Then there is minimum sink speed, called Vmin sink, which is almost never published for airplanes.

At best L/D, you will glide the farthest distance, but not at the least rate of descent.  At min sink, you will stay aloft the longest time, but you won’t go as far.

So, use min sink if the field is very close, and you want time to try to restart the engine, or whatever, like the debated turn back after takeoff.

Typically, best L/D will be very close to the best rate of climb airspeed, or Vy.

Min sink is typically very close to the best angle of climb speed, or Vx.

 

Jerry A. Eichenberger

Eichenberger & Associates

6037 Frantz Rd., Ste. 107

Dublin, OH 43017

Voice:  614-798-1600

Fax:  614-798-1620

Website : www.ehlawyers.com

Email:  jeiche...@ehlawyers.com