Your right, pictures are great. The problem is with the head assembled you
can't see the TT strap. I'll e-mail you some pictures from the BK117
(semi-rigid) head scanned from the Maintenance Manual and the Part Catalog
and also the same for the A109A/AII (fully articulated) head. JC

wrote in message
...

Having a picture certainly helps, but I'm still confused as to where
exactly that they go. First, are we talking about a semi-rigid or
fully articulated or other hub?

Essentially, it looks a lot like a box end wrench. However, in
function, it sounds a lot like an elastomeric bearing.

Do you know of any closeup photos with TT straps installed on the hub?

Dennis.


"Helimech" wrote:

The Tension-Torsion (TT) straps are basically 2 bushings a certain
distance
apart connected together by thousands of turns (I've heard something
like
12,000 turns) of stainless steel wire (around .020" dia.), sealed in a
plastic like covering. These straps (one for each blade) are what hold
the
main rotor blades to the rotor hub. The straps have to handle the huge
centrifugal loads (tension) of the blade but still allow for pitch
(torsion)
control inputs from the pilot. Here is a link to Lord Corporation and a
picture of some TT straps. Lord is the present manufacture of the
straps
for the BK117 and BO105. The strap that failed in Houston was made by
Bendix. http://www.lordmpd.com/aerospace/rot...ion_straps.asp

Hope this helps, I'm sure someone could describe a TT strap better but
this
is the best I can do this early in the morning. JC




Dennis Hawkins
n4mwd AT amsat DOT org (humans know what to do)

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