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  #41  
Old 07-08-2017, 02:40 PM
vic syracuse vic syracuse is offline
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Quote:
Originally Posted by rongawer View Post
Ok, you dragged me in...why do you care about stated time before overhaul? It's irrelavent to part 91 operations, let alone experimental where you are the manufacturer.

TBO's were relavent 50 years ago when monitoring technology was nowhere near what it is today. Free yourself from any stated TBO's and instead understand that you should monitor and service, repair or replace on condition. Condition based maintenance is much more efficient and cost effective way to ensure reliability. Case in point, my Baron has TBO's of 1700 hours per engine, but I have just over 2400 on the left one and it's in great condition and running very well - why would I overhaul it? There's not one regulatory or mechanical reason to do so and I'm thousands of dollars ahead by continuing it's operation.

That aside, the RV-10 blades you've listed are constant speed and have nothing to do with RV-12's, which is the point of this thread. Great topic, wrong location.

Ron, you are wrong on the inspection requirements for the Whirlwinds. They CLEARLY state on their website that a teardown inspection is every 400 hours or 3 years for the 3-blade and 650 hours and 5 years for the 2 blade for an RV-10.

BTW, I appreciate their short time periods while more time in the field is put on their props. Eventually I have no doubt they will be longer.

Vic
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Built RV-4, RV-6, 2-RV-10's, RV-7A, RV-8, Prescott Pusher, Kitfox Model II, Kitfox Speedster, Kitfox 7 Super Sport, Just Superstol, DAR, A&P/IA, EAA Tech Counselor/Flight Advisor, CFII-ASMEL/ASES
Kitplanes "Unairworthy" monthly feature
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  #42  
Old 07-08-2017, 03:14 PM
rongawer rongawer is offline
 
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Quote:
Originally Posted by vic syracuse View Post
Ron, you are wrong on the inspection requirements for the Whirlwinds. They CLEARLY state on their website that a teardown inspection is every 400 hours or 3 years for the 3-blade and 650 hours and 5 years for the 2 blade for an RV-10.

BTW, I appreciate their short time periods while more time in the field is put on their props. Eventually I have no doubt they will be longer.

Vic
Vic, I didn't read the website, and it's obvious to me now that you are referring to a different prop model from Whirlwind Aviation, not Whirlwind Propellers [fun fact: Whirlwind Propellers makes the blades for Whirlwind Aviation folks], but the quote I provided earlier was directly from my Whirlwind manual for the GA-UL350-3B, that I am using on my RV-12 (relevant to this thread), in the maintenance and inspection requirements. It's not wrong.

I'm sure this topic will continue, as it has for years. Some people choose to adhere directly to the time recommendation and I won't argue that it's your option to do so, but it's wrong to say that it's unsafe or foolish to continue operation beyond TBO times - nor is it unwise; this only propogates fear, uncertainty and doubt for those who may not be technically informed. Quite the opposite, I consider it wise to fully evaluate a components condition for it's remaining service life and spend your money where it's needed.
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  #43  
Old 07-08-2017, 03:17 PM
vic syracuse vic syracuse is offline
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Back to the question about a propeller for the RV-12. I have lots of hours behind 912's, with many different props. I have to say I am REALLY pleased with the Sensenich ground adjustable propeller that Van's sells for the 12. It is quite and smooth, and seems to perform really well.

I haven't flown a 3-blade on an RV-12 yet, so won't venture an opinion there.

Vic
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Built RV-4, RV-6, 2-RV-10's, RV-7A, RV-8, Prescott Pusher, Kitfox Model II, Kitfox Speedster, Kitfox 7 Super Sport, Just Superstol, DAR, A&P/IA, EAA Tech Counselor/Flight Advisor, CFII-ASMEL/ASES
Kitplanes "Unairworthy" monthly feature
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  #44  
Old 07-08-2017, 04:08 PM
Jamesey Jamesey is offline
 
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Default Thread Drift??

Put RV10 stuff in the RV10 forum.
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  #45  
Old 07-08-2017, 04:35 PM
vic syracuse vic syracuse is offline
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Mea culpa. I thought I already acknowledged I missed it was RV-12.

Vic
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Built RV-4, RV-6, 2-RV-10's, RV-7A, RV-8, Prescott Pusher, Kitfox Model II, Kitfox Speedster, Kitfox 7 Super Sport, Just Superstol, DAR, A&P/IA, EAA Tech Counselor/Flight Advisor, CFII-ASMEL/ASES
Kitplanes "Unairworthy" monthly feature
EAA Sport Aviation "Checkpoints" column
EAA Homebuilt Council Chair/member EAA BOD
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  #46  
Old 07-08-2017, 05:56 PM
Azjulian Azjulian is offline
 
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Roger Lee did a bunch of testing of props, 2 and 3 blade - he found that as long as you set for 5500 WOT in flat and level there was no difference

http://www.rotax-owner.com/en/rotax-...and-more-props
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  #47  
Old 07-08-2017, 05:58 PM
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rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by rongawer View Post
In my industry, we've completely moved to condition based maintaince, which sometimes dictates overhaul earlier than you'd expect, but often much later. If you follow a good inspection program, you'll be much safer - and that's not foolish.

Furthermore, the propeller manufacturer mentioned in the post I responded to, Whirlwind, clearly states in their manual:

"NOTE: There is no specified overhaul time. The propeller parts are removed from service when they can no longer meet the Continued Airworthiness Requirements."

So, in this context, the comment could mislead someone away from Whirlwind without being fully informed.
Ok, it appears you are arguing semantics here....

Whether you call it an overhaul or an inspection, the only way to evaluate the condition of a Whirlwind propeller, which it seems you agree is the appropriate way to evaluate condition, is to disassemble it.
I believe that is what Whirlwind recommends at every 400 hours (not specifically an overhaul). Then decisions on part replacement would be made based on condition.

I have been in this business along time and have seen a lot of products for experimental aircraft come to market without having to go through a certification test program. Often times at the expense of the users.
Whirlwind has had their share of development problems just like many others. In this instance, calling for inspections at low service times is not because of lawyers, it is because it is the right thing to do with a critical component that they don't have any long term service history for.
It is false that any TBO limit is set by lawyers. It is based on in service experience, and testing, and then the limit is set conservatively to be sure to cover all scenarios.

As far as being fully informed..... People have bought W.W. propellers without knowing that it has a recommended 400 hour inspection interval. Even if you don't care, and you would be satisfied with an external visual inspection at each condition inspection after passing 400 hours in service (against the manufacturers recommendations), not everyone would.


In an attempt to get this thread back on topic......

It is not possible to say which is better (two blade or three blade) because in some instances a three blade is, and in some a two blade is. It depends on what airplane, what engine, which propeller, etc. There especially is no way to compare best prop choice for an RV-12 with a Rotax, to what is best for other airplanes with Lycomings.


Early in the RV-12 development program the 3 blade ground adjustable from Sensenich was tested to compare performance to their two blade. The two blade out performed it by a large enough margin that the decision was made to not offer it as an option (even though the tooling and plans pages for installing it had even been mostly completed).

Fast fwd a few years.....
Sensenich now has a new design 3 blade for the 912 Rotax. It has been tested by us only a small amount of time but the performance compared to the 2 blade looks to be more promising. Hopefully we will be able to provide a more detailed comparison in the future.

Hopefully this makes it clear that you can't just categorically say whether a 2 blade or a 3 blade is the best choice.
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Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.

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Hubbard, Oregon
RV-6A (aka "Junkyard Special ")

Last edited by rvbuilder2002 : 07-08-2017 at 06:17 PM.
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  #48  
Old 07-08-2017, 06:09 PM
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rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by Azjulian View Post
Roger Lee did a bunch of testing of props, 2 and 3 blade - he found that as long as you set for 5500 WOT in flat and level there was no difference
As I said already in my other post, it is not possible to generalize that all 2 blades and 3 blades will be the same.

In the past, Roger's recommendations for prop pitch didn't agree with what you have posted so he has either changed his opinion or there was a typo.

I strongly recommend RV-12 owners not set their prop pitch for 5500 RPM WOT in level flight without using a specific altitude for the check. If you do this for any altitude lower than about 10,000, you will likely setting to course of a pitch. This will cause higher oil temps, poor take-off and climb performance, etc.
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Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.

Scott McDaniels
Van's Aircraft Engineering Prototype Shop Manager
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
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  #49  
Old 07-09-2017, 08:36 AM
rongawer rongawer is offline
 
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Quote:
Originally Posted by rvbuilder2002 View Post
Ok, it appears you are arguing semantics here....

Whether you call it an overhaul or an inspection, the only way to evaluate the condition of a Whirlwind propeller, which it seems you agree is the appropriate way to evaluate condition, is to disassemble it. I believe that is what Whirlwind recommends at every 400 hours (not specifically an overhaul). Then decisions on part replacement would be made based on condition.

I have been in this business along time and have seen a lot of products for experimental aircraft come to market without having to go through a certification test program. Often times at the expense of the users.
Whirlwind has had their share of development problems just like many others. In this instance, calling for inspections at low service times is not because of lawyers, it is because it is the right thing to do with a critical component that they don't have any long term service history for.
It is false that any TBO limit is set by lawyers. It is based on in service experience, and testing, and then the limit is set conservatively to be sure to cover all scenarios.

As far as being fully informed..... People have bought W.W. propellers without knowing that it has a recommended 400 hour inspection interval. Even if you don't care, and you would be satisfied with an external visual inspection at each condition inspection after passing 400 hours in service (against the manufacturers recommendations), not everyone would.
It's not just a matter of semantics to "inspect" versus "overhaul". However you are using both terms in the same context. One refers to measuring and evaluating for remaining service life, the other requires repairing or replacement of parts that are outside of service limits to restore the component; these are different processes, both physically - and legally in a certified aircraft. I do highly advocate inspecting and doing so on a recurring basis, at least annually and then only overhauling when the inspection condition dictates. Let me put this in context of Continental engines, which I am intimately familiar with; the manual requires an inspection on various times of 50, 100, 500 hours and so on, and then states to overhaul at another time, which varies widely with the engine model.

Having been part of the process myself, I'll just have to agree to disagree with you about how the final times are set - which is really irrelavent at this point. I do agree with you that they are established on a conservative basis.

And again, your discussion of Whirlwind Propellers brings confusion - it should be applied to Whirlwind Aviation, not Whirlwind Propellers - these are two different companies and propellers. The quote I provided previously is from the WWP maintenance section of their provided manual, not a website; it's related to their fixed pitch propeller and it has NO SPECIFIC TBO listed. This thread was about fixed pitch propellers for RV-12's, not constant speed propellers.

In the end, I simply want to encourage folks to perform inspections and not blindly replace components when a timer pops up.
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- RV10, N762G, Build in progress.
- Several others that are now just great memories for me.

Last edited by rongawer : 07-09-2017 at 09:38 AM.
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  #50  
Old 07-09-2017, 09:07 AM
sailvi767 sailvi767 is offline
 
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Quote:
Originally Posted by rv6ejguy View Post
I think Tom would still be using a 2 or 3 blade if it was faster since this is Reno and it's all about speed. Every mph counts. Theory is great but it's always trumped by real world experience and results. 284mph average speed around the course with a 360 Lycoming.
Most of the racers at Reno spin their engines well beyond 2700 RPM. Many exceed 3200 RPM. A two blade prop is unusable at those speeds because the tips are supersonic killing efficiency. With a IO360 using 2700 RPM a two blade should be more efficient.
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