Hi Dan,
Dan,
John Roach is right that 415-D flight test data the 1320 lb. gross STC
was the
basis for approval. The difference in gross is 80 lbs. (not 60 lbs.)
due to Light
Sport limits. The 9º up elevator restriction of the 415-D is entirely
unrelated to
any "danger of stalling" or "extreme risk". Such is speculation
without basis.
Fred Weick designed the Coupe under "Air Commerce Manual 04" rules and
regulations for airplane airworthiness. These standards were roughly
equal
to today's "Utility" category.
The CAB replaced above standards with "Civil Air Regulations Part 03"
11/13/45.
The new "Normal" category structural standard was less strict, and it
was further
revised effective 12/15/46. Fred did the math and quite logically
expected his
415-C design (and existing airframes) would be allowed an increase in
gross
weight from 1260 to 1400 lbs. in the "normal" category.
Unfortunately, one or more CAA people wanted the clear superiority of
the
Ercoupe design denied the commercial success it deserved. Special
sections
were inserted which unreasonably penalized its exemplary safe
performance.
One required that "Two-control (or simplified) airplanes" show lateral
stability "...
by demonstrating that the airplane will not assume a dangerous attitude
or speed
when all the controls are abandoned for a period of 2 minutes. This
demonstration
shall be made in moderately smooth air with the airplane trimmed for
straight level
flight at Vh (or at Vc, if lower)..., and with rearward c.g. loading.
OK so far!
Another required that "when it is desired to designate an airplane as a
type
'characteristically incapable of spinning,' the flight tests...shall be
conducted with:
(a) a maximum weight 5% in excess of the weight for which approval is
desired,
(b) a c.g. at least 3% aft of rearmost for which approval is desired,
(c) ...up elevator travel 4º in excess of [angle] to which...travel is
to be limited...,
(d) ...rudder travel 7º in both directions [beyond angle] to
which...travel is to be limited
Flight characteristics were STILL acceptable with the full 13º up
elevator at 1400 lbs.,
but only 9º up elevator was approved for operations at the higher gross
weight. The
effect was NOT improved safety but decreased safety...a betrayal of
public purpose.
Per Ercoupe Information Letter No. 1 dated Jan. 1., 1956, "In the
opinion of the factory,
this limitation seriously affected the landing qualities of the Ercoupe
(415-D). For this
reason the 415-CD was produced instead." (with 13º up elevator, and
1260 lbs. gross.)
Henry Berliner knew he could not fight the bureaucrats and make money,
so he pulled
the plug on the retractible, 4-place and Ercoach twin pusher projects,
laid off Fred Weick,
and sold Ercoupe assembly, sales and service to Sanders over the next
365 days.
Regards,
William R. Bayne
.____|-(o)-|____.
(Copyright 2009)
--
On Apr 21, 2009, at 21:15, John Roach wrote:
Dan,
I believe the nine degree up elevator limit in the 1329 lb STC resulted
from the same restriction in the conversion of the C Model to the D
Model. The data for the 1320 lb STC was based on the data used for the
C
to D conversion. Thus the question becomes, "Why the restriction for
the
conversion of the C to the D?" I have heard several different reasons
but I don't know if any of them are correct. For one reason or another
the FAA required the restriction when the higher gross weight was
approved. Many pilots seem to agree that the heavier plane might be in
danger of stalling with too much full up elevator and, should that
occur, a recovery might be difficult. However, I don't know if that has
ever been proven by a flight test. Another factor that could be
involved
is the amount of weight the FAA wants as a buffer over the allowed
gross
weight so that someone who misfigures and is "slightly" over gross
won't
be at extreme risk. I have had the 1320 gross since it became available
and find that the elevator restriction is not really a problem to me.
John Roach
N 2427H
Caliendo Dan wrote:
Can anyone explain the 9 degree limit with the 1320 lb STC? If you are
within
CG limits, I don't see how the extra 60 lbs play a role in 13 degrees
of elevator.
Dan Caliendo
Ercoupe Mach 0.14
3658H
