"Stu Fields" wrote in message
...


Surprising enough a series of hard landings were experienced by high time
helicopter pilot. Ship didn't have anywhere near 400hrs when a shaft in
the transmission experienced a fatigue failure. The focus was on the hard
landings as the cause and the stress risers of the shaft were ignored.
Another accident occurred where the builder did something not right which
caused some strong vibrations. He corrected the problem but didn't
replace a part that had a near zero radius fillet and that is exactly
where the fatigue failure occurred. This resulted in a fatal accident.
Another fatal accident occurred where another fatigue failure occurred at
a place where the fillet radius was reported as sharp. Again other
historical occurences were logged and the failure occurred at the sharp
fillet radius. Again the focus was placed on the historical occurrences
and not on the poorly machined fillet.
There are a number of kits out there that have been supplied similar
elements. The machinist for these parts had drawings which did not call
out a fillet radius. (That has been changed now.)
Another instance was called to the kit manufacturers attention where a
rubber seal was scarring (0.020 deep jagged groove) in a main rotor
shaft. The response was that they had seen this before and it didn't
constitute a dangerous condition.
To date the kit manufacturer has not sent out any warnings. They merely,
on their website, offer to inspect and replace the parts if you are
concerned about them. It sounds like they don't see a problem, but if you
the builder-flyer does, they will try to make you happy.
All of these parts are enclosed inside elements that come from the kit
manufacturer complete and closed up and evern cotter keyed. Unless the
kit builder tears these elements down and has enough of a technical
background to do a good inspection, he will not be aware of the risk that
he is taking.
Yeah the Air Command story speaks highly of someone's integrity. (We
probably know the guy). The "Center Line Thrust" was an arguable issue.
Cdr. Ken Wallis had his opinions about this and he had more than a few
hours in non "Center Line Thrust" ships. On the other hand the Stress
concentrations seen in this other kit is a well known issue to avoid.
Yeah I wish this kit manufacturer of issue would adopt the Air Command
philosphy.

Stu


Well, it certainly sounds like the kit manufacturer isn't much interested in
making this good without a lot more motivation. Considering they know the
tail drive needs updating (and has, in fact, within their organization), I'd
think they'd want to let that fact be known. It's a matter of safety and
it's disappointing that they're not stepping up on this. I assume you're
not in a position to say what company this is?

The tail drive issues are one thing. I'm absolutely flabbergasted that
they'd say that a groove being machined into the "main rotor mast" by a
problem seal "doesn't constitute a dangerous condition!!!" Good, then let
"them" fly the thing!

I understand that the centerline thrust issues was/is a hotly debated issue.
I never understood why that was. I understand that there are relatively
high time pilots out there that learned on HTL machines and have
successfully flown them for many hours but that doesn't counter the fact
that these machines are easily capable of doing the classic bunt over, or
power push over. Too many people have died because of it, including others
who were also described as "experienced" gyro pilots!! A true CLT pusher
style gyro will not do that and is inherently a safer bird because of it.
The fact that some well respected and experienced gyro pilots argued hard in
favor of the HTL side of things left a very bad taste in my mouth way back
when.

Good luck with whatever you're trying to establish with the helicopter kit
manufacturer!

Fly Safe,
Steve R.