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03-13-2017, 07:08 PM
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Join Date: May 2009
Location: Bay City, MI
Posts: 421
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Major or minor change Part 21.93
A friend asked me a question I could not answer. After their phase I flight testing, they painted their experimental aircraft. This would affect the weight and possibly balance. Part 21.93 discusses minor and major changes, a major change requiring a limited repeat of Phase I flight testing.
21.93 says "A??minor change?? is one that has no appreciable effect on the weight, balance, structural strength, reliability, operational characteristics, or other characteristics affecting the airworthiness of the product."
Do you think painting has no appreciable effect on weight and balance or not? If it has an appreciable effect on weight and balance, it would qualify as a major change and suggest they should repeat some of phase I flight testing. What would you tell them?
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Dennis
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03-13-2017, 07:15 PM
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Join Date: Dec 2009
Location: Boulder, CO
Posts: 4,435
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I'd sure like to see some actual data on the weight and cg position, before and after painting.
Dave
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03-13-2017, 07:28 PM
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Join Date: Jan 2008
Location: Ashland, OR
Posts: 2,573
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Well, the weight and balance certainly must be redone.
If the original Phase I documented acceptable handling qualities over the c.g. range that was tested, and that range is in the POH as the applicable c.g. limits, and those limits are still applicable after painting, then I don't think any additional Phase I testing would be required.
If you wanted to revise the c.g. limits from the previously documented and tested limits, then you would need to go back to Phase I.
It is likely that a chart of sample loadings would have to be revised. But a new weight and balance doesn't automatically trigger a need to return to Phase I.
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Steve Smith
Aeronautical Engineer
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VAF donation Jan 2020
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03-13-2017, 07:42 PM
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Join Date: Jan 2005
Location: 57AZ - NW Tucson area
Posts: 10,011
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Not req. but good practice
The shop that repainted my Tiger called it "decoration" and said they never re-weigh.
Checking one of the FAA examples I found this -
Over a period of time, almost all aircraft have a tendency to gain weight. Examples of how this can happen include an airplane being repainted without the old paint being removed, and the accumulation of dirt, grease, and oil in parts of the aircraft that are not easily accessible for cleaning. When new equipment is installed, and its weight and location are mathematically accounted for, some miscellaneous weight might be overlooked, such as wire and hardware. For this reason, even if the FAA does not require it, it is a good practice to periodically place an aircraft on scales and confirm its actual empty weight and empty weight center of gravity.
- which certainly implies that a reweigh is not needed (but good practice) after painting.
From the FAA AMT Handbook chapter on Weight and Balance.
https://www.faa.gov/regulations_poli...83-30_Ch04.pdf
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Gil Alexander
EAA Technical Counselor, Airframe Mechanic
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03-13-2017, 08:32 PM
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Join Date: Jun 2007
Location: new iberia la
Posts: 768
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Re weigh
To add: Multi engine aircraft flown under Far 135 must be reweighed every 3 years. Not that this remotely applies to us but we could use this requirement as guidance to consider re weighing every 8-10 years or after a significant change to the plane.
Don Broussard
RV9 Rebuild in Progress
57 Pacer
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03-14-2017, 01:18 AM
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Join Date: Sep 2015
Location: Socal
Posts: 453
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Vans addresses this in their plans. They say that depending on how much paint you use, paint can actually have a noticeable impact on the weight/balance. It can add up to 40ish pounds and shift your cg rearward. Its somewhere in the back of the plans where it talks about engine choices and propellers.
But to answer your question. I do not think it counts as a major modification. Just reweigh it when you're done.
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Working on an RV-4
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03-14-2017, 04:25 AM
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Join Date: May 2009
Location: Bay City, MI
Posts: 421
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That was my question on the regs; does painting 'appreciably' affect the weight and balance? If it does then it is a 'major change'. If not, it is a 'minor change'. Major changes according to our flight limitations necessitate re entering a portion of phase 1 testing. Regardless a new weight and balance makes sense.
I'm thinking adding 30 or so pounds of weight to his 1640 lb airplane, or 1.8%, is not an 'appreciable change', but I don't know how the FAA defines appreciable.
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Dennis
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03-14-2017, 06:23 AM
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Join Date: Jun 2005
Location: Locust, NC
Posts: 440
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Y'all thinking too hard up there. Weigh it, log it and go fly.
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Dave
M20C
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03-14-2017, 11:42 AM
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Join Date: Jun 2012
Location: Frederick, MD
Posts: 821
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14CFR Part 21.19 refers to changes in type design. Experimental aircraft do not have a type design, and therefore 21.93 does not apply. Your limitations likely state that major changes require you to report the change to FSDO or something like that. I have never heard of painting being classified as a major change. Items that change the aircraft weight and balance but do not change the maximum allowable weight and CG envelope are not major changes on that basis alone.
I would highly recommend weighing the aircraft post painting though.
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Dan Morris
Frederick, MD
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03-14-2017, 01:02 PM
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Join Date: May 2009
Location: Bay City, MI
Posts: 421
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Great advice from all. I will pass this on.
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Dennis
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