The STC for the 1320# upgrade is not a "paper only" change as some have suggested. There are several mods required to the aircraft before it can be signed off, including a trim tab modification, as well as the change in the elevator up-travel and other mods already mentioned. Thanks for pointing out the extensive FAA testing for approval to the STC.
Carl LaVon -- In [email protected], "Ed Burkhead" <e...@...> wrote: > > > > 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 >
