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Hamid says---

"All that the flying installations indicate is that no one has done anything in their aircraft that has led to the airframe failing due to the modifications. Maybe there is enough margin that it has not compromised safety at all. Maybe it has cut deeply into the safety margin and there have been a lot of very close calls that no one has known about. Without a real engineering analysis taking the big picture in mind, no one really knows."

I disagree;

In these turbulent weather encounters and other unexplained accidents, the full science of accident investigation rarely goes into determining the initial point of failure. Often the ensuing damage by fire--or impact--or removal -- damages wreckage to the point that an accurate determination cannot be made.
And, as an aside---I would be interested in knowing the level of expertise the investigators have in regards to composite, homebuilt aircraft structures.
So Hamid --I do not believe you can make a statement regarding "No one has done anything that has led to the airframe failing due to modifications." without taking into account accidents that have not been adequately examined by properly qualified investigators. For those that have the potential failure at some lower point of stress/Flutter onset than expected. This is one of the reasons why Harry's accident is so troubling. Investigators cannot use a canned explanation.

I do agree wholeheartedly with Hamid's statement that real engineering analysis is required. Most would agree (depends upon which dog you have in the fight??)" , but point is, who's going to do it?

Charlie K.

See me on the web at

www.Lancair-IV.com

From: Hamid Wasti <hwasti@lm50.com>
To: lml@lancaironline.net
Sent: Wednesday, May 9, 2012 1:38 PM
Subject: [LML] Re: Necessity of A/C in IV-P?

Ted Noel wrote:
> 3. Flight testing with a competent test pilot.
>
> I think #3 is best since it deals with the variabilities of the installation and creates a hard VNE number.
Does it? How much margin do you have? Testing is intended to validate engineering analysis, not to substitute it.

> Also, there are a lot of A/C installations flying. This implies a degree of safety.
Does it? How does your installation compare to the flying installations? How much safety margin do they have and how much will you have? How far have they pushed their airframe (intentionally and unintentionally) and how far will you push yours?

All that the flying installations indicate is that no one has done anything in their aircraft that has led to the airframe failing due to the modifications. Maybe there is enough margin that it has not compromised safety at all. Maybe it has cut deeply into the safety margin and there have been a lot of very close calls that no one has known about. Without a real engineering analysis taking the big picture in mind, no one really knows.

Regards,

Hamid

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