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Where does one find an aerospace Engineer to hire

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Marc Zeitlin

Exalted Grand Poobah
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Dec 11, 2015
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698
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Tehachapi, CA
I am most concerned about flutter nearing my desired Vne of 157kts (180mph).
I'd suggest that you be concerned about flutter at Vd, not just Vne, since that's the speed you are supposed to test at so that you can set Vne to 0.9 * Vd. So if you want a Vne of 157 KIAS (I assume you're talking IAS here, not TAS) then Vd would be 174.4 KIAS. And you'd do all your flutter testing to 175 KIAS to be able to set Vne to 157 KIAS.
 

Mad MAC

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Dec 9, 2004
Messages
653
Location
Hamilton New Zealand
Go through the PDF below and you will have done more than (WAG) 60% of the designers of homebuilt kits that have been sold. Build it conservatively using proven methods and then go fly, or hire a test pilot to fly, flutter test at increasing small increments of speed. If you have a lot of spare cash you can shake it on the ground first, but it still needs to be flown.
What HotWings didn't state is that Report 45 was up until recent revisions of FAR 23 an acceptable means to for showing compliance to flutter requirements of FAR 23, just make sure you are within the acceptable configurations / envelope for report 45.

Build a prototype, using as much or as little formal engineering as you can afford, and then physically load test it with sandbags, like they did originally. Sandbag tests were done to verify the Cub, Taylorcraft, and a thousand other airplanes. Chet Peek's book on Taylorcrafts has photos of the sandbag testing done on the prototype in 1935.
Its been done far more recently than that and is very common. I have seen a metal airframe design with the skin one gauge lighter than required and load tested very carefully. They would release the load on appearance of any failure & add little gussets etc as required. It made for a very light airframe (weather one could get a home builder to add all the little gussets would be an interesting question) I have seen people test a wing just by testing the spar assembly (I don't think it had the effect skin width even on it). I do note that the LAA specifically don't accept this method due to the frequency with which they fined the rear spars are inadequate.

Lots of certified aircraft bits also get tested by a fish scale (or a load cell), not because its hard to calculate, its just faster to take a photo of the fish scale with the load applied than it is to write up ones calculations. My old boss would load test helicopter ski baskets by getting 5 guys from the hanger to stand on the baskets, each holding a little sign with each persons weight.
 

JohnB

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HBA Supporter
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Aug 18, 2019
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I THINK we need to modify our terminology a bit. I believe for most of the discussion so far the proper consultant would be a DER (Designated ENGINEERING Rep) the Designated Airworthy Rep in my experience gets involved after all the designing, building and gnashing of teeth and presides over final inspection prior to flight.

OR I might be playing left field without a glove again John B
 

BBerson

Light Plane Philosopher
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Dec 16, 2007
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Port Townsend WA
A DER is an FAA designated person allowed to independently do some FAA tasks for hire in Type certification. Not the case here.
As stated before, designing an airplane requires a designer, with or without any letters.
 
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rbarnes

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Aug 28, 2015
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202
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Texas
I THINK we need to modify our terminology a bit. I believe for most of the discussion so far the proper consultant would be a DER (Designated ENGINEERING Rep) the Designated Airworthy Rep in my experience gets involved after all the designing, building and gnashing of teeth and presides over final inspection prior to flight.

OR I might be playing left field without a glove again John B
Not to mention that the whole DAR discussion got rolling because everyone misunderstood the original comment was about the DARCorp referenced earlier and had nothing to do with FAA inspectors 🤦‍♂️
 

geosnooker2000

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Mar 30, 2019
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Somerville, TN
Not to mention that the whole DAR discussion got rolling because everyone misunderstood the original comment was about the DARCorp referenced earlier and had nothing to do with FAA inspectors 🤦‍♂️
Not quite true, I actually brought up the question of did a DAR need to see the design calcs to sign off on a from-scratch design/build. Further, did he need to see them if the design/kit was going to be sold to the public. As people have confirmed, the answer is an amazing "no". Not that I'm complaining. I'm totally a Libertarian.
 

Mad MAC

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Joined
Dec 9, 2004
Messages
653
Location
Hamilton New Zealand
One point about finding an engineer, is to find one that is a generalist not a specialist, so someone who typically has worked in small companies & experienced in the realities of small budgets.

If one were looking to design something very similar to a Cessna airframe, one would be a mug not to get hold of a copy of Cessna: Wings For The World by William D. Thompson, just to get an insight into what issues where encountered in the flight test program.
 

geosnooker2000

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Mar 30, 2019
Messages
133
Location
Somerville, TN
It'll be interesting to hear what "the FAA" has to say about all this, if they even get back to you or even have a clue what you're asking them, whomever "them" is.
Well, just got that call-back. Mr. Ford was a nice guy who seemed to know his stuff. He informed me just what you guys have, that there is no engineering requirement, just the 40 hour testing period. He even suggested a couple of ACs. 20-27f and 90-89.
 

flyboy2160

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May 25, 2014
Messages
337
Location
california, USA
...What HotWings didn't state is that Report 45 was up until recent revisions of FAR 23 an acceptable means to for showing compliance to flutter requirements of FAR 23, just make sure you are within the acceptable configurations / envelope for report 45....
Cheers MAC! LOLOL For others considering using Report 45: it isn't as easy as it is to say 'use it.' You need the modal frequencies and, if I remember correctly, the rudder/vertical cp. If you're already that far pregnant, you may as well run a Nastran flutter analysis.
 

Marc Zeitlin

Exalted Grand Poobah
Joined
Dec 11, 2015
Messages
698
Location
Tehachapi, CA
He even suggested a couple of ACs. 20-27f and 90-89.
AC20-27F was superseded by AC20-27G back in 2009, so he's only 11 years behind - not too bad.

AC90-89B is actually VERY good as a primer on flight testing a new E-AB aircraft. It's a little light on specifics, but is good on process. While you're not talking about a canard aircraft here, I've got what I believe to be the canonical Phase I Flight Test Program document here:


third bullet point down, as written by Kevin Walsh (flies a COZY MKIV). Kevin wrote it, and I (and an Edwards AFB F-16/F-35 test pilot who also flies a COZY MKIV) edited it with him. It includes test cards, etc. Could always be made better, but can be used as a template for any aircraft test flight program, incorporating the processes from AC90-89A, Scaled, and the AF.
 
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