Mailing List lml@lancaironline.net Message #69336
From: Douglas Brunner <douglasbrunner@earthlink.net>
Sender: <marv@lancaironline.net>
Subject: RE: [LML] Canopy Latch modeling
Date: Mon, 03 Mar 2014 10:08:20 -0500
To: <lml@lancaironline.net>

Fred,

By the way, I agree with you and want point out that I never said:

"We have the talent here to do a 3D model and some wind testing without the need to fly someone's airplane or do full power taxi tests."

 

I also agree with your prior analysis of checklist use.  Using a checklist is good but not perfect.

 

D. Brunner

 

From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of frederickemoreno@gmail.com
Sent: Monday, March 03, 2014 7:50 AM
To: lml@lancaironline.net
Subject: [LML] Canopy Latch modeling

 

"We have the talent here to do a 3D model and some wind testing without the need to fly someone's airplane or do full power taxi tests."

 

Probably not true.  The canopy system includes the gas springs which hold it open on the ground, and the spring constant and damping coefficient of those gas springs are largely unknown, variable, and thus difficult to model.

 

Moreover when the canopy opens, you have a separated air flow condition moderated by the overall aircraft transient angle of attack (it changes when the canopy swings open and closed) which is exceptionally difficult to model on a computer without corroborating evidence from wind tunnel testing. 

 

Forecasting effects on tail would be very difficult even with exceptionally competent computational fluid mechanics software and computers.  And of course, effects triggered by any impulsive pilot-induced oscillation would be entirely missed.

 

Nope, computer models won't help enough to put solid predictive capability forward for study. 

 

But we do have  DATA in the form of accident statistics.  John's analysis shows that even with all the ambiguity in such data, the accident rate is unacceptably high.

 

Best solution, and probably easiest and by far most effective: a secondary safety latch. 

 

It then becomes a question of details of design and installation.  It is here that John and his supporters have failed to gain traction in the community and also failed to get feedback from the factory.   We need to know the effect of punching some holes in the canopy arch and mating structure so latch and catch can be mounted.  With that data and some design review from the community, design improvements would emerge, and as a group we could stamp out some simple parts, install, and deal with this problem once and for always.

 

Your airplane.  Your life.  Your choice.

 

Fred Moreno

 

Image
image001.png
Subscribe (FEED) Subscribe (DIGEST) Subscribe (INDEX) Unsubscribe Mail to Listmaster