Ted,

Aside from the test pilot question, which I'm not qualified to address, I think we should be careful about drawing conclusions that a given modification is benign because it hasn't been implicated.   Most IVP's spend most of their time flying around at 1 to 1.5 G's and some don't go near Vne.    That represents almost no test coverage.    Most owners don't have the resources (e.g. multiple airplanes specially modified for egress, massive sensors, and test pilot time) to mount a serious test program.  That is why I would claim that engineering analysis is the cheapest option available.  

Colyn

On May 10, 2012, at 8:18 AM, Ted Noel wrote:

Hamid,

Your qualifications are well-established. but perhaps you are reading my comments to say something I'm not trying to say.

In any aircraft, there will be building variations. In production aircraft, the production test pilot serves to be certain that there are no deficiencies within the certified envelope. In our aircraft, there is no certified envelope. As a result, a good test pilot will attempt to establish a safe envelope. For example, the location of stall strips will be adjusted to tame the stall. With regard to the air conditioning holes, the obvious question is reduced structural integrity leading to reduced flutter margins. A good test pilot should be able to nibble at that edge of the envelope to identify a flight limitation (VNE).

We have a number of air conditioners flying, and I haven't heard of the holes being implicated in a structural failure. That doesn't mean that they won't be. But the fact that they are accumulating flight hours suggests that they may be safe.

If a structural analysis were to raise a big red flag, obviously that could not be readily ignored. But our continued flight testing suggests that that is unlikely.

Please note that I'm not declaring a settled question. Rather, I see a tendency in the data.

Ted Noel
N540TF

On 5/9/2012 1:38 PM, Hamid Wasti wrote:
> 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
>
> --
> For archives and unsub http://mail.lancaironline.net:81/lists/lml/List.html
>
>
> -----
> No virus found in this message.
> Checked by AVG - www.avg.com
> Version: 2012.0.2171 / Virus Database: 2425/4987 - Release Date: 05/09/12
>
>

--
For archives and unsub http://mail.lancaironline.net:81/lists/lml/List.html