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----- Original Message -----From: Ed BurkheadSent: Thursday, September 04, 2003 7:51 PMSubject: [COUPERS-FLYIN] RE: [COUPERS-TECH] glide ratio----[Please read http://ercoupers.com/disclaimer.htm before following any advice in this forum.]----
Alan wrote:
> Does anyone know the "glide" ratio on a Ercoupe,
> if there is one :-)) ?
> And is there any way to improve it without completely
> redesigning the airframe?
Alan,
About 23 years ago, I did serious and very careful glide testing and got definitive ratio calculations. If my airspeed indicator hadnt been lying to me, I would tell you the exact answer.
This testing was done because during my 2nd flight in my Coupe, I had gas-line freeze-up and had a forced landing and I did my approach at 5 mph above the minimum flying speed, got a steep approach, almost no flare and landed with no damage (helped by a 30 mph headwind). I personally GUARANTEE your wife, Coupes can glide quite well enough to get you down safely.
I was surprised how high the best glide airspeeds were in my testing because of the lying airspeed indicator (My ASI said 117-118 when I was really going 100 and it showed 65 mph as minimum flying speed though the replacement ASI gave me a minimum indicated flying speed of about 55 (50 with a touch of power).)
Even adjusting for the real airspeeds, the numbers are higher than Cessnas but they are in line with the similar glide speeds and ratios of the Short Wing Pipers and Hershey-bar-wing Cherokees. (You want to see a steep descent, ride with a Tri-Pacer pilot doing a low-speed approach with engine at idle on a day with a 30 mph headwind!!!!)
However, after correcting for the erroneous airspeed indicator, this is (the approximate) truth:
Remember that Hershey bar wings get a better glide ratio at a HIGHER AIRSPEED than do high aspect wings like sailplanes or Cessnas.
In your Coupe:
At 50 mph (or pulling your yoke back to the stop), youll get an impressively steep and short glide ratio.
At 65 mph, youll get a much better glide ratio.
At 75 mph, youre somewhere in the range of the Coupes best glide ratio range. Your best glide ratio will be somewhere in the range of 70-85.
(My calculations had this number at 85 and a ratio of 12:1 but thats bogus. I still feel confident the true glide ratio at true ASI of 70-85 is better than 8:1 and maybe as good as 10:1 but I no longer have a Coupe so I cant go back out and test it.) The top of the curve was pretty flat in my testing and there wasnt much difference in the glide ratios among the best four 5-mph increments.
I think youll see your best, reasonably tolerable, glide ratios at 70, 75, 80 and 85 mph. Mind you, your rate of descent is still fairly high, but you have enough forward speed that your glide RATIO is not bad.
In short, if your fan stops, keep your airspeed up about 20 mph over minimum flying speed as measured in YOUR plane with YOUR airspeed indicator and the breeze will both keep you cool and greatly improve your glide ratio in a Coupe.
If anyone wants to go out and do serious glide-ratio testing, Ill write up the procedure again.
Ed Burkhead
http://edburkhead.com/
[EMAIL PROTECTED] (remove the XXX)
-----Original Message-----
From: alan1 [mailto:[EMAIL PROTECTED]
Sent: Thursday, September 04, 2003 12:17 PM
To: [email protected]
Subject: [SPAM] [COUPERS-TECH] glide ratio
----[Please read http://ercoupers.com/disclaimer.htm before following any advice in this forum.]----Aloha nui loa,Does anyone know the "glide" ratio on a Ercoupe, if there is one :-)) ?And is there any way to improve it without completely redesigning the airframe?My wife is nervous that if the engine quits, we are going straight down into the ground....(I hope that's not true)...Thanks.O
*<==N99616==>*
/ \
o oAlan============================================================================== To leave this forum go to: http://ercoupers.com/lists.htm Search the archives on http://escribe.com/aviation/coupers-tech/============================================================================== To leave this forum go to: http://ercoupers.com/lists.htm Search the archives on http://escribe.com/aviation/coupers/
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