"Steve R." wrote in message
...
"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.

Steve: As an old Bensen pilot from the "Self Taught 60's" when dual
instruction didn't exist, I taught myself to fly the thing as well a my wife
at the time soloed also. However, the advent of the side-by-side ships
presented an aerodynamic "Barn Door" which may have had something to do with
the bunt overs, and there were sure a bunch. I flew in winds and turbulence
with mine strong enough to hover and fly backwards and never had a problem.
In fact our ship never had a ding. It is true that once while doing the
"Brock Spirals" I noticed the nose tipping over more and more. Reduction of
throttle and easing forward on the cyclic and stopping the rotation was all
that was required. Based on my experience, I think that the old Bensens
were relatively safe with their "Rock Guard" horizontal and a relatively
high thrust line. I also noticed flying the Sparrohawk prototype that the
hands off flying thru turbulence had nearly zero pitch disturbance. I guess
if I had a side-by-side gyro I would probably look much closer at the CLT.
However the helicopters have my attention now.
This issue with the scarred main rotor shaft is the fourth separate issue of
what is apparently ignorance or disregard of fatigue problems. Even when I
reference things like the Standard Handbook of Machine Design, they pretty
much ignore me. I don't understand their apparent ignoring what could be a
very nasty liability issue.

Stu