Before we further get off on a tangent, I was not speaking about the flight
testing for the D mod, I was speaking about flight testing for the 1320 gwi
STC. The D model was from the manufacturer and a few years before I was born.
Let's keep this in perspective. And the 1320 gwi STC does not modify
structure. People who think so are exactly my reason for not buying into it.
I never said the coupe's structure wasn't safe to fly at 1400 in clear air.
I'll even further say that I don't have a problem over gross in certain
circumstances. And by probably referencing the D weight, the holder was able
to slide the STC through. But, by what reasoning do people have to assume the
structure is safe to fly over gross? Anyone tell me? It's out there, you
know. No, it's not FAA.
I'll say it again, I just don't buy into the paper GWI STC's. Not in any of
the airplanes I own. It's a bullcrap way of getting around rules and the
designs of the manufacturer.
I think we're done. I'm not going to change my opinion on this and additional
participation fortifies the fact that not many people are getting my reasoning.
----- Original Message -----
From: Ed Burkhead
To: ety
Sent: Sunday, February 15, 2009 10:48 AM
Subject: RE: [ercoupe-tech] stc for 1320
Al wrote:
Many of the same folks that bought the STC operated over gross before they
had it. Was it dangerous on Monday before it arrived in the mail and then any
less dangerous by Saturday when the A&P with IA installed the valves in the
gear and submitted the paperwork?
Al, I think the point is, the basic structure of the C and CD model planes
is substantially similar to the 1400 lb. allowed D model. On a fundamental
level, many people contend it is as safe to fly at 1320 lb. (or 1400 lb.) on
Monday without the STC or on Friday after application of the 1320 lb. STC or
after doing the model D conversion.
The fundamentals of the plane aren't changed.
Al wrote:
So what my contention is that a paper STC has the ability to make many feel
that the airplane can do what it actually can't.
Thus, the fundamental question is: Is a Coupe safe to fly at 1320 lb. (with
STC) or at 1400 lb. (models D, E, G, Forney F-1)?
Al wrote:
I'll bet your ranch that there was no flight testing involved in the issuance
of this STC, only scientific calculations based on the D's abilities and the
politics of the parties involved. But if using the D as a benchmark for the
structure, how is it that the STC can be issued to the straight C.?
As I heard it, the FAA did **extensive** testing before approving the gross
weight for the D model. I've been told that the FAA found that the
stall/spin-proof testing of the Coupe at 1400 lb. with the 13° elevator up
travel was acceptable. But, they went on to allow for field conditions and
inaccurate rigging. The FAA added two extra degrees of elevator up travel and
judged the stall/spin-proof behavior was not adequate at 1400 lb. and 15°
elevator up travel to maintain the certificated incapable of spinning
endorsement.
As the 1320 lb. STC requires the elevator limitation to be changed to 9° up
travel, this FAA determination doesn't apply.
So, where do you feel is the danger in flying at 1320 lb. gross weight?
I'll answer this question for me. I admire the Coupe's ability to fly at
100-108 mph on 75-85 hp. It has a fairly sleek airframe for the late 1930s or
1940s. But, due to the weight and low power, it climbs slowly - marginally
slowly, IMHO.
I countered this with a 7146 climb prop on my C-85.
With that prop, I could safely get out of 1800' no-obstruction grass
airports, being off the ground often by mid field and always by 2/3rds of the
field. (One (1) exception, at 1400 lb., zero wind, temp 92° or so and grass
exceptionally long, we were at 80-85% of the field before I lifted off [no
obstructions and plenty of flat cropland to use for airspeed increase and
climb].)
With that prop, I could always get to 12,500' at 1400 lb. gross weight. (One
(1) exception, in turbulence over Nevada I topped out at 11,500' (density
altitude 14,500').)
I think it's reasonable to redefine the C-85 prop selection for Coupes to be
7146 climb, 7148 normal, 7150 cruise, 7152 not recommended unless you are
flying at light gross weights, i.e. 1260 lb.
(Side note: The sleek airplane that lets the Coupe fly 108 mph on 75 hp also
lets it gain speed VERY fast with the nose down. Those who try aerobatics in a
Coupe risk over speed and high g-load pull outs and, quite simply, death.
Aerobatics are not recommended in Coupes, even though it may not be explicitly
prohibited for the C and CD models due to the old style certification rules.)
Al wrote:
As you, if I could change the rules I would, but I'm afraid that the rules of
physics are still a bit tough at this time.
Finally, once again, let's not forget how the D mod hurt the LSA status of
the Ercoupe without adding anything substantial except a GWI. Maybe it's still
a wait and see thing for me.
To those of us who are diametrically challenged, an increase in legal gross
weigh is a substantial improvement in safety due to the increased fuel
allowance for flights.
I think the safety record of the D, E, G and all later models gives adequate
evidence that the 1320 lb. STC is not a significant risk increase - given the
correct prop to allow adequate climb.
Ed
