On 6/3/05, Bill Dube <bdube@al.noaa.gov> wrote:
>http://www.maddyhome.com/canardpages/pages/alwick/risk.html
This is an interesting read, but a flawed analysis.
It looks like a mathematician's approach, rather than an
engineer's approach.
He compares failure rates for auto engine components operating in
an automobile with aircraft components operating in an aircraft. He then
assumes that the auto component will have the same mean time between
failures when installed on an airplane.
The speed and load profile for a car component and an airplane
component are completely different.
This would explain how he "doesn't get it" about the inherent MTBF
advantages of a rotary engine. It is quite likely that he doesn't
understand the drastic effect fatigue failure has on the MTBF as you
increase the continuous load.
As a rule of thumb, if you double the reversing load, you decrease
the the cycle life by a factor of 100. For a car engine connecting rod in
an airplane, you are not only (at least) doubling the load (torque) you are
also doubling the RPM, so the connecting rod will have a MTBF 200 times
shorter in the airplane than in the car.
The rotary has very few moving parts subject to fatigue failure
(unlike piston engines.)
Bill Dube'
Bill, I agree. This method is neither scientific, professional, objective or even sophisticated. First year medical students would do a better job of seeing fallacy (in the research sense) and applying statistical methods.
Al is right that it is important to examine these issues and his system can help clarify which issues are more important. But I sure wouldn't pay $150 to go to any seminars. The point system he uses has no reference validation, no statistical power analysis, and therefore very little meaning.
While he is right about the CAS being an issue, he seems very uninformed on other issues yet comes across as someone who feels that he is well informed. He even went so far as to presume to know the way Tracy thinks and approaches problems.