[Wing] Consumer satisfaction?

[George McNutt]

-----Original Message-----
From: wing-admin at vansairforce.org [mailto:wing-admin at vansairforce.org]On
Behalf Of Rob Prior
Sent: Wednesday, June 11, 2003 8:35 AM
To: wing at vansairforce.org
Subject: Re: [Wing] Consumer satisfaction?


George McNutt wrote:
>     individuals who seem to think that their MD-RA training manual
>     supercedes the CAR's.

Hi George,

I'd be interested in knowing which parts of the training manual
supercede which CAR's.

>     (1) Gross weight increase,
 >
>     This
>     seemed to be a case of the MD-RA worrying about their own liability
>     and ignoring what the CAR's said about the subject.

According to the calculation in Appendix A of Chapter 549 of the CAR's,
the maximum permissible wing loading of an RV-6A (using dimensions from
Van's website) is about 16.5 lb/ft^2, corresponding to a gross weight of
about 1800lb.  That exceeds Van's reccommended numbers by 200 lb and 2
lb/ft^2.  Do you feel qualified to second guess the designer, even if
"everyone else is doing it"?

Remember, the CAR's are meant to be generic, they weren't written
specifically for RV's.  They list the *limits*.  They don't list what is
reasonable or prudent for any one design (or for any one specific,
modified, aircraft).  Only the designer can be doing that.

Frankly, i'm surprised Van's was ever willing to write letters
authorizing increased gross weights at all.  Do those letters come with
reduced G limits?  They should...

-RB4
-----------------------------------------
Hi Rob

To answer your questions will probably get into a great diatribe on the
subject, however it may be interesting and it is nice to see some action on
the wing website, so here goes. Remember, in my case I am speaking of rules
that existed in April 2002 and there may have been subsequent changes.

(1) The CAR's never did require a letter from Vans to set gross weight,
neither did Transport Canada, this was (only) a MD-RA requirement.

(2) I do not feel qualified to second guess the designer. Therefore I will
observe his structural loading limits, especially the aerobatic weight.
However the recommended gross for my RV-6A is not specific in the builders
manual, it states "Vans recommends a 1600-1650 pound limit" but it also
states that "the aircraft builder is allowed to specify this [gross] weight"
(Page 14-1 #2).

Certainly I could set gross at 1600 or 1650lb. (which one?) and always have
more than utility category "G" limits. However the regulations also allow
builders to set a higher weight. The beauty of the homebuilt regulations is
that a builder can increase gross weight and fly the aircraft like a Boeing
or Airbus which have flown millions of hours with a 2.8 "G" limit.

How high could I have theoretically set my gross weight, CAR's limit
homebuilt weights to 3968 pounds, and there are no structural strength
requirements in the regulations.
It is my understanding (from a telephone conversation with Maurice Simoneau)
that we actually do have one Canadian RV-6(A?) registered with a 3968 lb
gross weight, I sure would have liked to witness that climb test!!


(3) I think Terry Elgood puts it very well in his pamphlet where he states
"some of the formula in chapter 549 are next to impossible for a builder
(and a lot of inspectors) to understand".

Actually that complicated formula for wing loading that we builders must
figure out has nothing to do with aircraft gross weight, "G" loadings or
strength. It is simply a calculation to see if one needs a "High Performance
Endorsement" on his pilots licence to fly that particular aircraft. If you
exceed the specified weights you need the high performance endorsement!!
Nothing at all to do with aircraft structural safety.

(4) I agree, why would any aircraft designer give anyone a letter to
increase gross weight. Once the kit leaves the loading dock the designer has
no control over how much strength the builder has added or subtracted from
the structure. The builder is ultimately responsible.

I believe that the proposed new homebuilt legislation has had a lot of input
from kit manufacturers and they will be a big liability relief for them. It
spells out the fact that the builder is responsible for everything,
including quality of (kit) components. By the way homebuilt weights were/are
proposed to increase to around 5000 lb. do we see a bigger Murphy Moose in
the future?

Happy Building,

George McNutt
Langley, B.C.