Re: [COUPERS-FLYIN] [COUPERS-TECH] Flight test question for LSA Coupes

Hartmut Beil Mon, 13 Oct 2003 20:56:40 -0700

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Ed.

I was reading the Sport Pilot definitions again.

It calls for a 39 knot ( 45 miles) stall speed when at 1236 Gross weight. ( For some reason I believed that to be 38 knots.

I believe that the Coupe is stalling at exactly that speed when at that gross weight.

This is according to my calculations from the data of previous revisions of the TC.

I don't know how the stall measurements are professionally done. Special air speed metering equipment and a flight where extra fuel is burned off per calculations to be exactly at gross weight when doing the measurements, I guess.

So one could try to talk Univair into trying to do these measurements officially, and have them apply for the Sport Pilot Classification of the Coupes. If they don't own a Coupe one could give them one to do the testing.

For the existing Models of Coupes it would mean no further changes, other than that a weight calculation would have to be done .

415-C models stay the same - 415-D models keep their elevator limitations and from 415-E on still no changes to the airframe.

I can't speak for the Alons and Mooneys, since the stall speed measurements had been done with 1400 lbs gross or 1450 lbs gross weights, stall might be different there due to the different canopy design. But probably not.

The catch is to get Univair to do the stall measurements and to apply for the certificate.

The other catch is, like I previously mentioned that IMHO most Ercoupes will bring more than 1000 lbs onto the scale with full tanks. The payload would in some cases be less than ONE pilot needs to fly the thing legally.

But to say it again - according to my calculations, an Ercoupe would stall at 39 knots when at 1236 pounds gross weight.

So instead of fighting the impossible battle with the FAA, one could start a battle with the TC holder instead.

Hartmut

----- Original Message -----

From: Ed Burkhead

To: Coupe-List

Sent: Monday, October 13, 2003 3:05 PM

Subject: RE: [COUPERS-FLYIN] [COUPERS-TECH] Flight test question for LSA Coupes
----[Please read http://ercoupers.com/disclaimer.htm before following any advice in this forum.]----
Chris,

Theyll be looking for the true minimum controllable airspeed. In most planes that is the stall speed. In a Coupe, its just the speed youre going with the yoke back to the stops.

I do think a lot of Coupes are very close to passing the 45 mph test, especially at 1232 lb. gross weight. If the FAA made any adjustment to the required minimum stall speed, a lot of Coupes may pass.

Thats why Im interested in GPS measured speeds, both directly into the wind and directly downwind. If I were testing for myself, Id figure out the wind direction at 3,000 and do the test at least twice. Id start at 4,000 slowly cooling the engine over several minutes to avoid shock cooling till I couldnt hold altitude. Id record the GPS speed at 3,500 into the wind then turn and measure at 2,500 downwind. Then Id climb up and duplicate the measurement in the opposite directions going downwind first then upwind. Rigorous testing would do the test four times.

Then you average the speeds recorded.

Ed Burkhead

http://edburkhead.com/

[EMAIL PROTECTED] (remove the QQQ)
 
I have a feeling pretty close. I mean really, whats going to happen when an FAA inspector actually goes for a ride to confirm the stall speed of a Coupe?

I can see it now

The throttle is all the way out and the steering wheel is all the way back, your IAS is holding steady just over 40 MPH, and youre sinking at about 550 FPM. The inspector looks over at you and says OK, lets see the stall.   At which point you reply Sorry, thats as close as she gets, you pause for a minute as a grin splits your face, but while were here let me show you something. The inspector looks at you in brief alarm as you drop the right wing and roll into a steep turn. After a few seconds, having convinced himself that you are not, in fact, about to drop out of the sky, he records the numbers: IAS shows about 30mph, Sink rate is 750fpm, in a 45 degree bank and in perfect control.

Granted, you and I know that the indicated airspeed is WAY off in high AOA maneuvers like that, but what criteria are they using to define Stall Speed. If its IAS then weve got it made. If they really mean the speed below which you loose control of the plane, well, we cant really get there from here; our plane was just designed too well.

Well probably just have to wait and see where we stand when the dust settles. Im sure the Ercoupe community will find a way to get in under the Sport Pilot umbrella somehow.

Chris

-----Original Message-----
From: Percy Wood [mailto:[EMAIL PROTECTED]
Sent: Sunday, October 12, 2003 10:47 PM
To: Ed Burkhead; Coupe-List; Coupe-Tech
Subject: Re: [COUPERS-TECH] Flight test question for LSA Coupes

At 03:21 PM 10/12/03 -0500, Ed Burkhead wrote:

I m wondering just how far a Coupe at 1232 lb. and 13° up travel (20° up travel with the split elevator) comes to qualifying as a LSA under the NPRM s guidelines. Here s a challenge for you to try when you are out flying.

"A flight test is worth a thousand expert opinions" "Tex" Johnson,
Who rolled a Boeign 707 over the Seattle Hydroplane races in front
Of God, the FAA, his boss and the spectators (previous list not
necessarily in order of Power)

I have heard, Ed, that the Ercoupe stall speed was placed in the manuals
because "we need one of those," and has not really been verified. Yeah,
you're not the only one who wishes they'd forget about those 28 pounds
and let us stay in the air in one of the mosr forgiving planes ever designed.
              Percy in Portland
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Re: [COUPERS-FLYIN] [COUPERS-TECH] Flight test question for LSA Coupes

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