Hi Larry,
And your point is...? ;<)
The manufacturing process of Ercoupes was not the basis for airframe
approval (being in conformance with the type certificate). Such
approval was the final test flight by a CAA-Designated factory
representative (certain ERCO test pilots were so certified).
No Ercoupes, Forneys, Alons or M10s left the factory without a full
spinner. The factory drawings, including that of spinners, are
considered incorporated by reference in the FAA aircraft type
certificate; including sequential changes as appropriate to a
particular airframe according to the status of said drawings when it
was manufactured and/or subsequently modified and documented by log
entry, if sufficient, or 337 or STC.
In my humble opinion, an approved 337 is necessary to remove pieces of
the airframe which were present on its acceptance flight such as the
nose strut fairing and rubber bumper or the spinner. The Ercoupe
spinner is an aerodynamic fairing which functions to smooth the air
flow that enters the cowling and cools the engine.
It does not take an aeronautical engineer to understand that increased
turbulence at the cowling intakes would reduce effective air pressure
and air flow, and that such air flow reduction directly translates into
less heat carried away and a higher engine operating temperature than
would otherwise be the case.
How much? I would guess perhaps as much as the extra sump shrouds
required on the C-85 "upgrade" contribute. The efficiency of air
cooling in each Ercoupe varies with the completeness and tightness of
its baffling and seals. There is no logical reason to knowingly
degrade the system at the air source in terms of volume and/or
pressure.
So why are there so many skull cap spinners on Ercoupes? In all
honesty, there are two predominate reasons you find a skull cap on an
Ercoupe; and neither is appearance. It is because an owner is too
cheap to replace one that needs replacement or because an owner or
his/her mechanic at one time could not realign the cowling/attachments
after disassembly such that the spinner fits or is symmetrical with the
cowling. A third "reason" is that the plane came to the present owner
that way and he/she has not ever specifically considered whether it is
proper or legal because of general "acceptance" of the practice.
A skullcap on an Ercoupe is, to me, a "red flag warning" that other
related maintenance deficiencies likely exist that careful inspection
would reveal.
Regards,
WRB
--
On Aug 26, 2009, at 13:13, Larry Snyder wrote:
Boy, if it's not there are a LOT of illegal Ercoupes out there!
On Aug 26, 2009, at 12:01 PM, Glen Davis wrote:
Does anyone know if the Skull Cap spinner is legal for use on an
Ercoupe with a metal prop?
Thanks
Glen
Glen Davis
917 297 1111
www.ishootpictures.com
