My assumption was that there would be damage to the nose gear assembly or
its mounting structure and attach points before there was a catastrophic
failure that would allow a prop strike, and the stronger the cable the
greater the damage. A simple fixed pitch prop with a clutch behind it to
protect a Rotax engine and gear box would probably be a less expensive fix
than if the landing gear frame were to be torn out of the tunnel. On second
thought we better consider damage short of tearing the whole thing apart
because then not only do we get a prop strike but the nose gear is probably
going to be planted in the bottom of the engine. Of course, a more
expensive prop changes the equation significantly.
Best regards,
Rob Housman
A070
----- Original Message -----
From: "Fred Fillinger" <fillinger@ameritech.net>
Subject: Re: Trike Nose Leg Bungee Breaking.
> Very cogent analysis, Rob. Maybe it would help that everything would
> happen in a sequence. Bending of the leg, breaking of bungee, partial
> collapse of the frame's fat tubing where the cable hits, and then
> finally the cable. The final whack to the airframe, if a beefier
> safety cable survives, is thus after energy has been dissipated. Sort
> of the way they engineer autos.
>
> I agree on your final point, as also if everything lets go, slipper
> clutch or no, the engine (gearbox integral with crankcase) could
> easily become junk, especially prop strike on a hard surface rwy.
> Airframe likely repairable, or so we hope....
>
> Regards,
> Fred F., A063
>
> Rob Housman wrote:
> >
> > From the tri-gear manual, 30 May 1998 edition, page 29-12:
> >
> > Remember that the bungee does not provide the nose gear springing,
> > the flexibility of the leg does this. The bungee is to allow a
> > momentary overload to take place without over-stressing the anchor
> > point.
> >
> > If this is the purpose of the bungee, any stress that is sufficient
> > to break the bungee AND the factory specified safety cable is quite
> > likely to over stress the anchor point. Ergo, it is probably not a
> > good idea to add strength to either, and in particular to strengthen
> > the safety cable. The energy dissipated by breaking the bungee might
> > protect the anchor points from damage but I suppose that breaking the
> > cable will definitely cause some damage and breaking a thicker cable
> > would cause even more damage. Any landing bad enough to break either
> > is likely to be expensive so I guess I'm just quibbling about what
> > pieces will need to be repaired.
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