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Prop Change: Major Alteration or Not?

R

RV8R999

Well Known Member
Looking for opinions
Does switching from a FP 2-blade Wood Prop to a FP 3-Blade composite Prop constitute major alteration?

FAR 21.9 (I think) defines a major alertation as any change which changes the operating characteristics.

While performance may (or may not) change the operation (pilot actions) will not.

Curious what ya'll think?
 
RV8R999 said:
Looking for opinions
Does switching from a FP 2-blade Wood Prop to a FP 3-Blade composite Prop constitute major alteration?

FAR 21.9 (I think) defines a major alertation as any change which changes the operating characteristics.

While performance may (or may not) change the operation (pilot actions) will not.

Curious what ya'll think?
Click to expand...

Absolutely! I didn't know (exact same prop change from 2 blade wood to Catto 3 blade) and had to confess to my FSDO a couple years later. He scolded me and let me sign it off with a reference to him in my log. Worst part, in my mind, was an A&P/IA had made the change and never mentioned this requirement. But then he left a lot of problems......
 
Yes, this is considered a major change and will require some time back into Phase I. Think about major changes as those that have the potential to affect the FLIGHT characteristics of the airplane.

Vic
 
maybe not

a major alteration.

We had an RV-4 on the field that changed from a 2-blade wood prop to a 2-blade metal prop. The IA that did the work called his PMI at KC FSDO and he was told that this was NOT a major alteration considering that both props are fixed pitch. I'm sure one would get differing responses from different FSDO's.

Bill
RV-7 N151WP
Lees Summit, MO
 
billgill said:
a major alteration.

We had an RV-4 on the field that changed from a 2-blade wood prop to a 2-blade metal prop. The IA that did the work called his PMI at KC FSDO and he was told that this was NOT a major alteration considering that both props are fixed pitch. I'm sure one would get differing responses from different FSDO's.

Bill
RV-7 N151WP
Lees Summit, MO
Click to expand...

Exactly... this subject has been beaten to death before, really depends on who you ask @ the FAA. You WILL get different answers. :eek:
 
I can see where the FSDO would give differing opinions. You're looking for pilot/vehicle interface issues (none here), flight characteristics (doubt it) and W&B (maybe).

I could go either way, but would lean towards no if the weight change stayed within the CG envelope.
 
I say no also

If you carved your own original design and implemented some inflight pitch change mechanism... But an off the shelf prop proven compatible with the engine and airframe I don't even see as in the gray area of the rules. If you built the plane and have your repairman certificate you need to read the rules and implement them in a sensible way as they are written, document everything as required and move on.

Bob Axsom
 
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Here we go again with opinions. The rules are pretty specific, actually, even though different FSDO's and A&P's/IA's seem to interpret them differently. Bob, given that all of our Experimental airplanes are "hand-made" to no specific certification process, there is no basis to say that one propeller is proven on many airframes. Almost everyone one that I inspect has it's own differences and nuances, and we all see this evidenced by the numerous cooling issue posts by builders on this site alone supposedly with the same airframe/propeller/cooler combinations. To think that a change from a 2-blade to a 3 blade will not cause some differences in flight characteristics and/or engine operating parameters is not true.
I certainly wouldn't make this type of change without doing some testing and comparing, and I would question why someone else wouldn't want to do the same. Even at the cost of fuel today, 5 hours of flight testing is miniscule in the scheme of things and could probably be accomplished over a week end.
My .02. :)

vIC
 
vic syracuse said:
Here we go again with opinions. The rules are pretty specific, actually...
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Not to be argumentative Vic, but isn't your statement that the "...rules are pretty specific..." itself an opinion? After all, I'm an A&P, have read the regs, and like many other certified mechanics, FSDO personnel and other generally smart people, come to a different conclusion. Without trying to establish which side is right or wrong, doesn't that at least indicate the rules are NOT specific?

Can you provide the language in the reg that clears this all up? If I missed it I will gladly stand corrected.
 
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THE ONLY RULE WHICH APPLIES:

According to our OpLims this is the rule:

21.93 Classification of changes in type design.

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(a) In addition to changes in type design specified in paragraph (b) of this section, changes in type design are classified as minor and major. 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. All other changes are ?major changes? (except as provided in paragraph (b) of this section).

It isn't at all specific. The word appreciable is open for interpretation....

I'll call my FSDO tomorrow.
 
To further muddy the water, I have read some people that made a fairly compelling argument that it is the holder of the certificate that determines if it's a major alteration. In other words, if it's a grey area, the guy signing off the work makes the call. That seems like the logical solution, but that is EXACTLY the reason it's probably wrong in the eyes of the feds.

It would be nice just to be able to wrench on an airplane without being a lawyer as well.
 
In my opinion...

RV8R999 said:
<snip>The word appreciable is open for interpretation....<snip>
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That has ALWAYS been the problem. Interpretation could vary widely on what is "appreciable."

I might suggest that if you contact the FSDO, you get an answer in writing from them. Think about it. You contact the FSDO on the phone about changing the prop, he says it is a minor change so no Phase 1 needed, no revised For 8130-6 needed. You hang up the phone and head for the hangar.

You change the prop, but then have an accident. You make a claim and your insurance company starts looking at the logs and sees that you made a prop change. They get an expert that says that your prop change is a major change, and you didn't contact the FSDO about a test area, and didn't go back into Phase 1, and didn't submit an 8130-6. You broke the rules and now they won't pay.

At least if you have something in writing from the FSDO stating that in his opinion the change was not "appreciable", and therefore you didn't need Phase 1 and the 8130-6, you might have a chance.

I just spent the money to have my OL updated to the current version. The version on the plane I purchased stated that a major change was changing the make and model of a prop, and that Phase 1 and an 8130-6 was required. The current OL say that a major change is going from FP to CS or back. I wanted to be able to change the prop pitch and not have to worry about the 8130-6. To be on the safe side (legally) I probably would still contact the FSDO for a test area and go back into Phase 1 for the 5 hours.

Good Luck and let us know what the FSDO says...
 
A question you might ask yourself is would your insurance still cover you after an accident or incident. If after an investigation the FAA/NTSB says you made an illegal change you may be left out in the cold. This should weigh in on the decision. Just my two cents.
 
Being that most FSDO folks are not that familiar with the experimental world, most draw their conclusions and interpretations as they exist in the certified world. So if you use that as an example, a certified airplane is approved via a Type certificate data sheet (TSDS) in most cases which approves a certain combination of engine and propeller for the aircraft. If you change one or the other from the original certificated combination it would be considered a major alteration.

If you changed from a FP to a CS prop I don't there would be any question.

I would also conclude that changing to any different model of prop from what you originally certifed your experimental with would also constitute a major alteration in the eyes of the FAA and the insurance company.
 
Walt said:
<snip> I would also conclude that changing to any different model of prop from what you originally certifed your experimental with would also constitute a major alteration in the eyes of the FAA and the insurance company. <snip>/QUOTE]

If that is the case, then why the change of OL by the FAA from stating that a major change was changing make and model of prop, to changing from FP to CS, or CS to FP?
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ccsmith51 said:
If that is the case, then why the change of OL by the FAA from stating that a major change was changing make and model of prop, to changing from FP to CS, or CS to FP?
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To clarify... so folks would stop calling them on this subject. I know my insurance company does not care what prop I'm flying, and I'm pretty sure the FAA could care less too. :)

A fixed pitched Catto to another fixed pitch Catto has not set any alarms off on this end and we're working on flying prop #4.
 
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What I was told

I certified my -4 last year, and the inspection was done by the local GSO FSDO. The inspector whom signed off my aircraft went into some detail about alterations, but the example he used was in fact a prop change,as its fairly common for a hombuilt to change props once or twice to optimize performance. Since it is a component of the "powerplant" and may have effect on the flight characteristics, he stated I would need to contact the FSDO with the changes noted in the logbook, and an entry back into phase 1, and the FSDO would give me the duration of that phase 1. He stated that it would likely only be 5 hrs. or so, and then I would re-enter phase 2. As I am a holder of an A&P/IA certificate(dont want to lose it!), I will likely follow his recomendation if I do any prop changes..which are in my future plans. I like hearing others opinions on this matter, as there seems to be quite a few different views.
 
fixnflyguy said:
The inspector whom signed off my aircraft went into some detail about alterations, but the example he used was in fact a prop change,as its fairly common for a homebuilt to change props once or twice to optimize performance. Since it is a component of the "powerplant" and may have effect on the flight characteristics...
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This is the view held by a majority of FAA inspectors, from local to headquarters level. Since a propeller change can have a substantial (or, to use the regulatory term, "appreciable") effect on performance, weight and balance, and vibration (i.e., reliability and/or airworthiness) of the aircraft it would be considered a "major change". The only time it is not is if the propeller is replaced with the exact same make and model (including pitch) propeller.

Yes, there are some inspectors who may hold a different view. If you talk to your local FSDO inspector and he/she says no, it's not a major change and to go ahead and do it, I would strongly suggest that you get that statement in writing so that, if you ever have to substantiate your claim to another inspector you will have something more than just your word to go on.
 
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