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Thread: [IAC-L:591] Re: S-1S weight and balance
Message: [IAC-L:591] Re: S-1S weight and balance
Follow-Up To: ACRO Email list (for List Members only)
From: "Dave Pilkington" <dpilkington at asta.bna.boeing.com>
Date: Tue, 29 Jul 1997 01:27:40 UTC
Yes, you are right. If the modification is substantial such that
something like 30lb is actually required then the pitching moment of
inertia is increased significantly (both from that 30lb plus whatever
is stuck on the other end of the aeroplane) and the spin recovery
characteristics need to be examined cautiously.
Fuel in the SF260 tip tanks increases yaw moment of inertia which
requires similar considerations - difference is that this is within
the control of the pilot. So the manufacturer has already done the
work and has told us not to go spinning with fuel in those tanks.
The Beagle Pup actually had a ballast weight that you would add if
you wanted to go spinning!
> Since I'm still missing some posts, I may be speaking out of turn and/or may
> not have the story right. However, for what it's worth... when I read a post
> regarding putting 30 lbs. in the tail, I recalled having read, some time ago,
> a report on an S-1 which was in C.G. but had a lot of lead strapped to the
> fail wheel. Although, it was in C.G. mathematically, when in a fully
> developed spin, it failed to recover due to the tail weights being on such a
> long lever arm. Correct me if I'm wrong, but it would seem, and I'm no
> engineer, that calculating C.G. on a static basis give one answer, but when
> rotational momentum is added to the equation, the answer is different.
>
> I know, for instance that the Siai Marchetti SF-260 is fully aerobatic but
> restricted to no akro if there is fuel in the tip tanks, and my S-2B is
> restricted if there's fuel in the top wing header tank, I assume for the same
> reason.
>
> Might be something to consider when adding tail weight if it's literally
> added a far aft station.
>
>
> Bill Bancroft
> n77tw at aol.com
>
!
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DJP
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