Design work on the BRS installation is 98% complete - the one unknown is the
exit hatch attachment, and we have a pretty good idea of what we are doing
there, but the final decision will be a test by BRS on a dummy fuselage top and
hatch - work on which will hopefully be completed in the next couple of months.
Stress analysis on the installation (maintaining airframe integrity when not in
use, and keeping the parachute attached to the airframe when deployed) is
largely complete, with the report still to be written (here in the UK we have to
get approval from PFA engineering for mods)
The installation has been designed around the "Classic" fuselage aft bulkhead -
ie with the small baggage space - although the fuselage is an XS type. the
reasoning behind this is that with close to 40lbs at the back of the cabin, the
baggage allowance will also be 40lbs - although exactly how much can be placed
there will be down to CG calculations.
The aft attach points will not transfer to the XS type baggage bay - it requires
a much higher aft bulkhead, at least to a line about 3-4" above the fuselage
split line, and the BRS is situated 50% into the (short) aft bulkhead - and
would in any case sit in the center of the XS type baggae bay.
It's not impossible to design an XS type installation - but stressing it
(absolutely essential with a possible 6G deployment load -around 4 tonnes on any
one point) costs.... we have already put better than $5000 into stress analysis,
and don't feel the desire to put any more in - however, if enough builders are
prepared to club together, I will be pleased to do the design and drawings if
the "BRS club" pay for the extra stressing work.
As for "classic" type installations - once the mod application has been
completed and the design approved by the PFA, drawings and construction
information will be available for the cost of the media - probably on paper and
CD. Aft attach fittings and some mouldings - critical components and the BRS
cabin cover will be available - all the rest of the special parts/mods are
designed to be done using temporary formers or built in place. BRS will, when
the design is 100% complete, have details of the straps, etc.
It will be possible to retrofit the conversion to a flying aeroplane - but it
will not be a pleasant job - the fuselage will have to be inverted for some
time, and doing the layups in a complete fuselage will be something of a
nightmare (but do-able). Much better to do it whilst the fuselage top is
off.......
Basic details are:
BRS attached to aft bulkhead.
primary connection to the airframe is via steel cable running down the roof,
center of split windshield (1.25" wide bar that doubles as rollover brace) to a
pair of short kevlar loops over the top engine mount stubs.
Aft connections are a pair of kevlar straps buried in channels about 6" aft of
the doors
Aft attachments are ali fittings bolted to the reinforced bulkhead - stiffened
by composite corner boxes over the fittings (forward) and reaction webs (aft of
bulhead)
the 3 connection straps/steel cable come together in a box center top, starting
aft of the rear door line. 50% of the kevlar straps are stored in this box.
BRS exit is reinforced with a substantial foam/ glass stiffener inside the rim.
exit hatch (and storage lid) is cut out from the original skin, modified, and
reattached using dry micro with a PTFE stress riser built in.
If anyone wants a .PDF drawing of the installation, email me off-group and I'll
send them out next week.
Over to you chaps.....
Miles
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