VAF Forums

VAF Forums (https://vansairforce.net/community/index.php)
-   RV General Discussion/News (https://vansairforce.net/community/forumdisplay.php?f=2)
-   -   Major or minor change Part 21.93 (https://vansairforce.net/community/showthread.php?t=147620)

dspender 03-13-2017 07:08 PM

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?

David Paule 03-13-2017 07:15 PM

I'd sure like to see some actual data on the weight and cg position, before and after painting.

Dave

scsmith 03-13-2017 07:28 PM

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.

az_gila 03-13-2017 07:42 PM

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

cajunwings 03-13-2017 08:32 PM

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

Robin8er 03-14-2017 01:18 AM

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.

dspender 03-14-2017 04:25 AM

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.

dlloyd3 03-14-2017 06:23 AM

Y'all thinking too hard up there. Weigh it, log it and go fly.

RVDan 03-14-2017 11:42 AM

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.

dspender 03-14-2017 01:02 PM

Great advice from all. I will pass this on.

Sue 03-14-2017 07:34 PM

Paint
 
A gallon of weighs ? But after all the chemicals and aeromatics evaporate, a gallon of paint on aircraft weighs a couple of ounces

Sue 03-14-2017 08:09 PM

Paint
 
Well I don't know what paint would have 60% solids
House paint? But automotive paint say blue would
Have .03%-.1% titanium dioxide, or say black
Which would have .1% carbon black. And at 9.5 lbs a gallon
Works out to 155 OZ .01% works out to 1.5 OZ
Oops 1.55 OZ now that's for one thin coat, no primer etc

ChiefPilot 03-14-2017 09:18 PM

Quote:

Originally Posted by Sue (Post 1157867)
A gallon of weighs ? But after all the chemicals and aeromatics evaporate, a gallon of paint on aircraft weighs a couple of ounces

I was curious about paint weight, so I weighed my RV before and after. The paint added 26 pounds and shifted the CG aft by 0.9 inches.

Auburntsts 03-15-2017 05:33 AM

I could be wrong, but I thought that painters shoot a primer coat on before any color coats. If true that's got to add some weight, probably more than the color coats.

Mel 03-15-2017 06:33 AM

Quote:

Originally Posted by RVDan (Post 1157758)
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.

There is a paragraph in your operating limitations that starts out, "After incorporating a major change as described in §21.93, the aircraft owner....."
So for all practical purposes part §21.93 does apply just as part §43 applies for the purposes of a condition inspection.
Remember your op lims can reference parts of the FARs that would not normally apply. Another example is part §91.205 for night and/or IFR operations.

SgtZim 03-15-2017 07:13 AM

Quote:

Originally Posted by Robin8er (Post 1157633)
.... 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..

Holy cow! I somehow had the impression that guys were putting on maybe 3 or 4 gallons of paint and primer. How many gallons would you have to spray to add 40 lbs?

update: found this: http://www.paintcenter.org/rj/oct07n.cfm

So roughly you'd have to spray 14 gallons to add 40ish lbs. Is that what an average paint job will go through?

vic syracuse 03-15-2017 07:16 AM

I did explain this to the OP a few days ago. Nowhere can I find a reference that a paint job is considered a major change. Many airplanes get flown to paint shops all over the countries in which they reside and there has never been any discussion in any of the Orders regarding requirements to return to Pahse I testing.
However, I do think a new W&B with a logbook entry is very appropriate and should be considered necessary.

Vic

Selma 07-06-2017 04:47 AM

Quote:

Originally Posted by vic syracuse (Post 1157968)
I did explain this to the OP a few days ago. Nowhere can I find a reference that a paint job is considered a major change. Many airplanes get flown to paint shops all over the countries in which they reside and there has never been any discussion in any of the Orders regarding requirements to return to Pahse I testing.
However, I do think a new W&B with a logbook entry is very appropriate and should be considered necessary.

Vic

The paint job diminishes the actual payload? Not MTOM hopefully?

n82rb 07-06-2017 08:43 AM

Quote:

Originally Posted by dspender (Post 1157640)
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.

the most common accepted definition of "appreciably" in reference to W&B is that if it changes the envelope or the max weight limit then it is a major change, if it just adds or deletes weight, then it is minor change and a re-weight or calculated change entered in the log book covers it.

bob burns
N82RB RV-4


All times are GMT -6. The time now is 01:46 AM.