On Sep 28, 2004, at 1:02 PM, Greg Bullough wrote:
At 01:34 PM 9/28/2004, William R. Bayne wrote:
>The factory got 127-129 m.p.h. with new planes in 1945 thru spring of 1946.
To paraphrase Mark Twain, 'there are lies, damned lies, and factory flight test results.'
Prior to the FAA's stepping in during the mid-70's, virtually every light aircraft manufacturer
routinely inflated their cruise and max speeds from 10 to 20 percent.
Whether they did so just by changing the numbers on the paper or whether they
pressured test pilots to come up with better results isn't clear. But the fact
is they did it. Most of the numbers you see in the classic aircraft books are
laughable.
127-129 in 415Cs from the factory is laughable.
We have examples of the Ercoupe today which are as good as factory-new,
little, if at all, heavier. They aren't that fast. They tend to be 105-110 MPH
airplanes.
Not to cast aspersions on Mr. Weick, but perhaps the reason he was so quiet
about it was that he was part of a system of deliberate 'marketing over truth.'
Greg
On Sep 28, 2004, at 1:24 PM, Roger Anderson wrote:
I'll second that! I've got a bunch of old Flying magazines from the 40',
50' 60's. The performance figures stated in the various manufacturers ads
are rediculous. Some of their cruise numbers so far fetched that I can't
imagine how they could explain the real numbers customers found after
purchase. Every manufacturer was guilty. Roger
Greg, Roger
I have data from some Erco factory flight tests that were made in the course of various experimental efforts by Erco that were never specifically published. I not only believe these figures accurate, but achievable today by a light, carefully prepared steel gear Ercoupe (but maybe not ALL of them).
These speeds are in line with what contemporary flight tests by presumably qualified aviation journalists of the day also observed and published.
The planes used in these tests were probably the fastest of those tested when certified, "hand picked" for the purpose and almost certainly faster than the average. That does NOT, however, make their achievements "laughable" or "rediculous" (sic).
It is true 100% that the average coupe today does well to get 105-110 m.p.h. 100 m.p.h. is what I use for flight planning purposes.
The "average" coupe today is also normally heavier than it once was (sometimes by a LOT). Many are not properly rigged, as to power-off glide speeds, etc. per factory bulletins.
The later "wraparound" main landing gear was designed with retraction in mind, so it didn't matter (or seem to at the time) that it had significantly more drag than the earlier design with the rubber doughnuts up in the wings and thinner fairings just for the vertical legs.
But none of the above changes the thrust of my earlier input, which I will repeat.
For a given airframe, average or not, any "improvement" achieved by converting a C-75 to a C-85 may be as much associated with optimizing the engine-airframe-prop combination as from changes required for FAA acceptance. The devil remains in the details.
It is not enough to see. You must understand what you see!
Regards,
William R. Bayne
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Copyright 2004
