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  #31  
Old 09-28-2022, 06:46 PM
jrs14855 jrs14855 is offline
 
Join Date: Apr 2008
Location: Lake Havasu City AZ
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Default Conrad

Conrad used the Twin Commanche as a personal airplane after the record flight. It still had the tanks. I don't think anyone knew or cared what his gross weight was. If he was in NY and wanted to go to CA his inclination was to put in a bunch of fuel and go nonstop. TC will go coast to coast on a bit over 200 gallons, with IFR reserves.
Another interesting thing is that on the single and twin Commanche's the tip tank fuel gets a "free ride" gross weight goes up by the weight of the tanks and fuel. Only 30 gallons so not a big deal.
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  #32  
Old 09-28-2022, 08:11 PM
Blw2 Blw2 is offline
 
Join Date: Apr 2022
Location: Saint Johns, FL
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Default

all this talk about the design engineer owning the margin
and the idea about factors of safety.

One important reason for factor of safety that unless I missed it I don't believe was mentioned....and that's the engineer makes mistakes too.... they can't think of everything...and yes, we are very often overly conservative too.

Sometimes a larger FS is applied to some components while a smaller FS might be applied to other systems in the same aircraft. How that all meshes together is often outside the comprehension of even the design engineer. Often rules of thumb get applied that might have a tight FS for some situations but be extremely over conservative at the same time. It can be complex for sure.

We hope at least, that the designer....or more likely the design team... has considered everything that is realistically possible to consider and made the best compromise decisions along the way. Without having the full big picture someone doing a modification is making some blind assumptions for sure....but it might not necessarily be wrong/dangerous/stupid/or whatever....

I'm left remembering a term I'd heard in a seminar once a very long time ago..."Star Trek Engineering...going where no man has gone before."
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  #33  
Old 09-29-2022, 02:28 AM
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newt newt is offline
 
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Location: Sydney, Australia
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Quote:
Originally Posted by Ironflight View Post
have compassion for the folks that have to worry very day about density altitude…..
Nah.

- mark
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  #34  
Old 09-29-2022, 05:21 AM
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plehrke plehrke is offline
 
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Location: Defiance, MO
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Quote:
Originally Posted by Blw2 View Post
We hope at least, that the designer....or more likely the design team... has considered everything that is realistically possible to consider and made the best compromise decisions along the way. Without having the full big picture someone doing a modification is making some blind assumptions for sure....but it might not necessarily be wrong/dangerous/stupid/or whatever....
It all starts with what are the loads on the aircraft and then how are those loads distributed throughout the airframe. In my 37 years of aircraft design, loads can be one of the most debated things within the structural design team.
If we fly above gross weight used in the analysis then the starting load number is higher to be distributed down to individual parts. If we make mods to the original design then the distribution of the loads to individual parts changes. If you fly above gross weight with a modified design, loads on individual parts can be completely different than the analysis and testing performed on the original design.
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  #35  
Old 09-29-2022, 05:49 AM
rocketman1988 rocketman1988 is offline
 
Join Date: Jun 2010
Location: Sunman, IN
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Default How

With all the talk about engineering, I am wondering how anybody ever survived without a full structural analysis, CFD run, stability and control program, and a certified engine…

Tic
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  #36  
Old 09-29-2022, 09:40 AM
terrye terrye is offline
 
Join Date: Feb 2010
Location: Vancouver, BC, Canada
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Default Explain Gross Weight for Engine Choice

Not sure which era you are referring to. I the early era, analysis was a bit light, and the proof was in the flight testing. This was the era of the test pilot and a lot of them were killed doing the testing. Little was understood about spins and structure and control surface flutter. Later, ground based static testing started to eliminate some of the in flight failures. As more research was done, materials were better understood, as were loads, gusts and so on. Today, calculators and computers have replaced the slide rule, and CFD is used to validate wind tunnel testing and vice versa. Now, the design and analysis disciplines have a much better understanding and flight test is much safer. Engineers use all the tools available to design safe machines.

The engineering process has always been design, analyze, build, and test, then go back to the beginning as needed (but I'm sure you know this).
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  #37  
Old 09-29-2022, 02:23 PM
rocketman1988 rocketman1988 is offline
 
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Default Yep

Yes, I know, hence the Tic…
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