Polishing prop

islandboy

islandboy

Pre-takeoff checklist
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islandboy
What techniques/materials are most useful (and least harmful) in the day-to-day maintenance of the prop?

A friend of mine applies a slightly abrasive old cloth for the minor burrs, but I haven't found any comparable material.

Does anyone else have a recommendation?
 
Pledge or Plexus and a paper towel or mocro fiber cloth. Whatever's in your hand after you clean the windscreen.
 
What model prop is it? Theoretically a polished prop is not airworthy in a lot of cases.
 
You can certainly polish your prop, but you can't remove the protective coatings required by any applicable Instructions for Continued Airworthiness. So, I wax and polish my prop, just as I wax and polish most of the rest of my airplane, but I don't strip the paint from the prop, and I touch up the paint as needed to comply with the ICAWs for my Sensenich prop.

So what sort of prop do you have, and what do its ICAWs say?
 
Ron Levy said:
You can certainly polish your prop, but you can't remove the protective coatings required by any applicable Instructions for Continued Airworthiness. So, I wax and polish my prop, just as I wax and polish most of the rest of my airplane, but I don't strip the paint from the prop, and I touch up the paint as needed to comply with the ICAWs for my Sensenich prop.

So what sort of prop do you have, and what do its ICAWs say?
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Here's what the prop shop said......( I've had two polished props on old restored taildraggers, unpainted variety. ) They said only Hamilton standard props , unpainted , are legal. Many APS or AIs will not pass an unpainted prop and insist it be painted by a prop shop. If it's painted I just use mothers polish- cleanser. Works real Gud!
 
The model is: McCauley 2A34C201/90DA-(8)

My read of the ICA is that most anything other than careful cleaning ought to be referred to a credentialed few.

Ron Levy said:
You can certainly polish your prop, but you can't remove the protective coatings required by any applicable Instructions for Continued Airworthiness. So, I wax and polish my prop, just as I wax and polish most of the rest of my airplane, but I don't strip the paint from the prop, and I touch up the paint as needed to comply with the ICAWs for my Sensenich prop.

So what sort of prop do you have, and what do its ICAWs say?
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Clean soft water to denatured alcohol 10:1 takes care of just about everything on mine.

I don't know if it's congressionally 'approved' for props, but it sure spiffs up the aluminum on a polished plane very well in between polishings. And it won't hurt paint from what I can tell.
 
islandboy said:
The model is: McCauley 2A34C201/90DA-(8)

My read of the ICA is that most anything other than careful cleaning ought to be referred to a credentialed few.
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Here is the manual with the ICAW for your prop. Note the following:
(6) Do not polish propeller blades unless specifically permitted by McCauley’s instructions.
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And I don't see any such instructions for your prop in that book. Further, when repairing nicks, it says:
After filing and polishing, the damaged area should be inspected, and when possible, by fluorescent dye penetrant method to verify that all damage has been removed and the blade is not cracked. The area should then be re-protected by localized application of chemical film per MIL-C-5541 (for example, Alodine) and repainted as necessary.
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A&Ps & IAs are only allowed to do minor maintenance to propellers, Certified propeller repair shops must follow the Overhaul manual when servicing these propellers. Thus they must do the paint and final finishing to comply.

There is nothing saying that finish must stay in place while in service. Other wise when you get surface abrasions, chips and the like, or you would have a unairworthy prop.
 
islandboy said:
What techniques/materials are most useful (and least harmful) in the day-to-day maintenance of the prop?

A friend of mine applies a slightly abrasive old cloth for the minor burrs, but I haven't found any comparable material.

Does anyone else have a recommendation?
Click to expand...

Are you talking about dressing the prop edge or polishing the prop blade? For dressing the prop edges of nicks and burrs I have several sizes of half round fine cross cut files I use. The key is to remove the minimum amount of material as possible with blending out any sharp edge or other structure that can act as a stress riser. I just work them with very light strokes.

As for polishing the blades, I'm not sure that's legal, I just touch up the paint with Krylon and polish the spinners with Flitz.
 
Painted prop, just the higher end auto cleaner and spray on "wax", Lucas makes a sweet spray on wipe off stuff in a blue bottle, check auto zone.

As for polishing a prop, as in bare metal, I've seen bunches of guys with them, I was going to do it to my old plane before I got the 85, seems they all end up annualed every year. :dunno:

I just figured it's more of a higher maintenance thing compared to a real safety issue having a polished prop over painted.


YMMV.
 
Tom-D said:
There is nothing saying that finish must stay in place while in service. Other wise when you get surface abrasions, chips and the like, or you would have a unairworthy prop.
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However, per the ICA for that McCauley prop, when one of those minor nicks is repaired and polished (a minor repair which an A&P can do legally), the polished area must be repainted.
 
Ron Levy said:
However, per the ICA for that McCauley prop, when one of those minor nicks is repaired and polished (a minor repair which an A&P can do legally), the polished area must be repainted.
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Yeah, that happens maybe 10% of the time due to the overspray factor and the time it takes to deal with it, it only takes a minute to dress a nick. Some people will brush touch, but that looks bad quickly. Most people let it ride until annual. I used repaint props on annuals if they needed it as a little 'extra service'.
 
Yes, I was really just talking about dressing the edges. "Polishing" was a poorly chosen word in this case.

Henning said:
Are you talking about dressing the prop edge or polishing the prop blade? For dressing the prop edges of nicks and burrs I have several sizes of half round fine cross cut files I use. The key is to remove the minimum amount of material as possible with blending out any sharp edge or other structure that can act as a stress riser. I just work them with very light strokes.

As for polishing the blades, I'm not sure that's legal, I just touch up the paint with Krylon and polish the spinners with Flitz.
Click to expand...
 
islandboy said:
Yes, I was really just talking about dressing the edges. "Polishing" was a poorly chosen word in this case.
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If you dress a prop frequently (I do, I don't take off with a sharp nick in a prop, it only takes a minute to address) you should also get a dynamic balance reasonably frequently (I have added it to my list of things to do at annual). Dynamic balancing of props IMO is probably the best maintenance dollar you can spend. Not only is it cheap (I've never paid more than $125 a prop) it affects everything on the plane, including you.
 
islandboy said:
Yes, I was really just talking about dressing the edges. "Polishing" was a poorly chosen word in this case.
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The manual for your prop still says that it must be repainted after repairing a nick, notwithstanding Henning's observation about how this may be more honored in the breach than in the observance.
 
Getting it dressed is time in service critical, getting paint back on it... not so much.
 
Filing a prop to repair rock nicks is not an owner maintenance item and as much as I usually don't care about that limitation? Filing a prop is something I won't do. I will run the fine side of a Leatherman file down mine to flatten little burrs from sand or water erosion but the bigger nicks that require material removal and feathering go to my mechanic for proper dressing. As for painting? Touch-up and general paint renewal is an owner maintenance item according to Maccauley.
 
Ron Levy said:
The manual for your prop still says that it must be repainted after repairing a nick,
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Show me that in writing.

the manufacturers do not want you painting, simply because the final balance is by painting. Plus the fact if you blend a nick out and don't get all of the crack, you will cover it with paint and not see the crack progressing until the prop is toast.

Prop ICA's vary from manufacture to manufacture, and there are a great many props that have no ICAs, they were manufactured prior to the requirement.
 
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Ron Levy said:
The link to the McCauley manual with the ICA for his prop is in my earlier post (#9 above). And it covers the issues you mentioned.
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No not good enough, it does not say the paint and final finish must stay in place during service.

If it did, your aircraft would be un airworthy. Know the difference between MUST and SHOULD.

And McCauley isn't only prop producer.
 
I had a polished prop on my Pathfinder for 12 years. It looked great and my A&P mechanics liked it because they could more easily see any cracks that could normally be hidden by paint.

Never had a problem getting it signed off at annual.
 
Jay Honeck said:
I had a polished prop on my Pathfinder for 12 years. It looked great and my A&P mechanics liked it because they could more easily see any cracks that could normally be hidden by paint.

Never had a problem getting it signed off at annual.
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I remember polished props being common.
 
On a different forum the other day someone said that we can't even touch up a prop without using the SW Polane brand listed in the manual. :mad2:
 
Tom-D said:
No not good enough, it does not say the paint and final finish must stay in place during service.
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True, but that is not the issue. The instructions for repairing dings include repainting after the ding is repaired before returning to service. And no, you do not have the option to ignore the ICA unless you get another method approved by the FAA.
 
Ron Levy said:
True, but that is not the issue. The instructions for repairing dings include repainting after the ding is repaired before returning to service. And no, you do not have the option to ignore the ICA unless you get another method approved by the FAA.
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Sure you do, you have the option of just ignoring it and continuing on. :dunno:
 
What do folks think of dressing the leading edge, not dings but erosion and burrs, by rubbing it with a steel bar such as a tool handle instead of a file. It removes no material, smoothes the surface and leaves it in compression which retards the initiation of fatigue cracking.
 
Jay Honeck said:
I had a polished prop on my Pathfinder for 12 years. It looked great and my A&P mechanics liked it because they could more easily see any cracks that could normally be hidden by paint.

Never had a problem getting it signed off at annual.
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Yes and so did a lot of other folks.

The prop manufacturers started yelping about it, then the late Bill O'Brian used the same argument he told us at the last seminar I attended that he gave. "If there is no requirement that the paint stay on the prop to be airworthy, why can't it be removed?" If it must stay on the prop, to be airworthy, Is every prop with a chip of paint missing an un-airworthy prop"?

I wish Bill was back. He was the last A&P-IA that held the head mech job, He gave us his personal phone number, and asked us to call him if got **** from FSDO.
 
Tom-D said:
Yes it is, if there is no requirement for the paint to stay on the prop, why can't it be removed?
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Ask the folks at the Engine and Prop Directorate -- they're the ones behind this. But they are adamant about the issue.
 
Ron Levy said:
Ask the folks at the Engine and Prop Directorate -- they're the ones behind this. But they are adamant about the issue.
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That's already been done. that's wy we see no one getting busted by the folks at FSDO.

There is no written instructions that the paint must stay on the prop. The engine and prop directorate can't show you one either. If there were such a instruction / requirement every used prop in america would be un-airworthy.
 
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Ron Levy said:
Well, yes, you can, but you wouldn't be legal to do that.
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BS Ron. Show us the rule that says the prop must have the finish renewed every time the paint is damaged. Or give it up.
 
Tom-D said:
That's already been done. that's wy we see no one getting busted by the folks at FSDO.

There is no written instructions that the paint must stay on the prop. The engine and prop directorate can't show you one either. If there were such a instruction / requirement every used prop in america would be un-airworthy.
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Not true Tom.

Do a search on the 170 board. There was a discussion a while back about some FSDOs tagging props that were polished/unpainted.

Like Jimmy Cooper previously mentioned, only certain Hamilton Standard (like mine) can be legally left unpainted because they have the manufacturer guidance for polishing the prop unlike other manufacturers.
 
Fearless Tower said:
Not true Tom.

Do a search on the 170 board. There was a discussion a while back about some FSDOs tagging props that were polished/unpainted.

Like Jimmy Cooper previously mentioned, only certain Hamilton Standard (like mine) can be legally left unpainted because they have the manufacturer guidance for polishing the prop unlike other manufacturers.
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Right, there is a difference though between a stripped/polished prop, and a prop that has had the paint eroded off the leading edge. I have never seen a prop tagged for not keeping the paint touched up.
 
bnt83 said:
So we can stick-on a leading edge boot as a minor alteration but cannot remove the paint and polish it? Hmmmmmm :eek:

http://mcfarlaneaviation.com/Products/?CategoryID=135&ID=31143040&
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You can also use tape with no approval at all. 3M makes a door edge guard and rock chip panel tape that is awesome. Works great on wing and tail leading edges as well if you live in abrasive prone environments that go a real long way to preventing any blade damage and maint. You don't get small dings and chips, but it doesn't protect against the big rocks that will cause the out of service levels of dings.
 
Props didn't have a whole lot of certification requirements back then did they?

Models 1C172/EM, 1C172/MDM, and 1C172/MGM:​
Civil Air Regulations Part 14, effective December 14, 1956.​
Model 1C172/

14.0 General. 14.00 Provision for rating. 14.01 Scope. 14.02 Hubs and blades. 14.03 Testing facilities. 14.04 Military propellers. 14.05 Propeller operation limits. 14.06 Propeller identification data. 14.07 Previously approved propellers. 14.1 Design requirements. 14.2 Commercial propellers. 14.20 Data required. 14.21 Tests required for propellers other than fixed pitch wood propellers. 14.22 Tests required for fixed pitch wood propellers. 14.23 Inspection of a tested propeller. 14.3 Military propellers. 14.4 Modified propellers. 14.5 Procedure relative to type certification. 14.50 General. 14.51 Sealed drawing list. 14.52 Major changes. 14.53 Minor changes. 14.54 Reductions in diameter.
14.0 General.

 14.00 Provision for rating. Pursuant to the provisions of the Civil Aeronautics Act of 1938, as amended, empowering and requiring the Civil Aeronautics Board to prescribe such minimum standards governing the design, materials, workmanship, construction, and performance of propellers as may be required in the interest of safety, and to provide for the rating of aircraft as to airworthiness, the requirements hereinafter set forth shall be used as the minimum standards for establishing such rating for propellers for use in certificated aircraft.

 14.01 Scope.

 14.010 Airworthiness requisites. To show eligibility of a propeller for certification the propeller shall meet the requirements herein as to design, construction, and testing. The manufacturer shall comply with the requirements by the submission of technical data and by conducting tests with suitable test equipment. The applicable requirements are set forth in §§ 14.1 through 14.4.

 14.011 Type certificate. The general requirements for the issuance of a type certificate are set forth in Part 01.* The procedure relative to type certification of propellers is set forth in § 14.5.
* Note — Now in Part 02.
14.012 Production certificate. The requirements for the issuance of a production certificate are set forth in Part 01.*
* Note — Now in Part 02.
14.013 Deviations. When a propeller embodies a feature of design or construction which deviates from the practice in conventional screw propeller types, application shall be made to the Administrator for special rulings covering the feature in question.

 14.02 Hubs and blades. Interchangeable propeller hubs and blades are certificated as separate units and the word "propeller as herein used applies, where applicable, to a propeller hub and to a blade as well as to a complete propeller.

 14.03 Testing facilities. A manufacturer submitting a propeller for certification shall conduct all of the tests and supply or arrange for the testing facilities necessary to show compliance with the requirements contained herein. When, in the opinion of the Administrator, adequate and satisfactory methods of testing other than those outlined herein are available, propellers tested by such methods may be eligible for certification.

 14.04 Military propellers. A propeller of a type which has passed the regular endurance tests of and is approved by the United States Army Air Corps or the Bureau of Aeronautics, Navy Department, may be certificated in accordance with § 14.3.

 14.05 Propeller operation limits. A certificated propeller shall not be operated at a power or propeller shaft speed, or in conjunction with an engine bore, greater than the limits assigned thereto by the Administrator. The Administrator map specify short-time operation in excess of these limits for take-off purposes except that neither the power nor the speed limits will be raised by more than 10 percent without further testing.

 14.06 Propeller identification data. A certificated propeller, propeller blade, or propeller hub shall have the following information conspicuously displayed upon it: manufacturer's name; name, model designation, and serial number of the propeller; and maximum power and maximum speed for which certification has been granted. The identification data shall be permanently attached by means of a plate, stamping, engraving, etching, or other such method upon a non-critical surface of the propeller blade or hub. When such data are not visible when the propeller is assembled or installed on an aircraft, they shall also be painted or printed on the propeller blade or hub.

 14.07 Previously approved propellers. These regulations supersede the requirements for approval of propellers set forth in previous regulations. However, propellers rated as suitable for use in approved aircraft in accordance with previous requirements may be used in certificated aircraft at the discretion of the Administrator.

 14.1 Design requirements.

 14.10 Propellers shall be so designed as to operate without excessive vibration or flutter and shall be constructed of materials which are suitable for service conditions.

 14.11 The surface of a propeller blade shall be smooth and the blade shall be faired with respect to the thickness and the moments of inertia about the major and minor axes, with no abrupt curvature changes or irregularities along the blade. Critical surfaces of a metal propeller hub shall be machined smooth without tool marks and any change in cross section shall be faired with as large a fillet as possible.

 14.12 It is recommended that a propeller be so designed that the weakest portion of the propeller blade or hub may be inspected without disassembly and that excessive wear or a partial failure will precede a serious type of failure.

 14.2 Commercial propellers.

 14.20 Data required. In the case of a propeller of a type which has not been previously approved by the Army or Navy, and for which the manufacturer desires the certification of the Administrator, the following information shall be submitted:
14.200
  1. Application for type certificate on a form which will be supplied for the purpose by the Administrator.
14.201
  1. A complete set of drawings descriptive of the propeller, which drawings shall be numbered and dated and shall include change letters for each revision. All details of the propeller shall be shown, including the profile and plan form of the blade, the size of blade cross sections at frequent stations, the hub design and the materials of construction. The material shall be specified on the drawings by reference to specification numbers of the Army, Navy, S. A. E., or other recognized standard whenever possible. If the manufacturer refers to his own specification numbers, details of such specifications shall be furnished the Administrator. All drawings shall be folded to a size of approximately 9 by 12 inches, with the title showing. In order to eliminate a possible source of controversy, the Administrator will not accept drawings which may be altered after approval. Blueprints, photostats or the equivalent are acceptable. If certain of the drawings required for a particular propeller are identical with drawings previously submitted and approved in connection with a prior type of propeller made by the same manufacturer, such drawings need not be again submitted.
14.202
  1. A complete parts list in duplicate, showing the drawing number, change letter, and name of each component part of the propeller. The drawing numbers shall be listed in numerical order. When only one or two drawings are submitted for compliance with § 14.201, it is permissible for the manufacturer to submit these drawings in duplicate in which case a parts list is not required.
14.203
  1. A complete log certified to by the person making the test or signed by a witnessing inspector of the Administrator, at the discretion of the Administrator, describing the manufacturer's tests of the propeller in accordance with §§ 14.21 or 14.22, as the case may be. The log shall include a detailed record of the test with dates; names of persons involved; name and model number of engine, or name, model number, and identification mark of the air-plane issued by the Administrator of Civil Aeronautics; and hours of testing with corresponding engine speeds. The report shall also include the results of a detailed inspection of the propeller after the test in accordance with § 14.23.
14.204
  1. A stress analysis when required by § 14.210 or when, in the judgment of the Administrator, the design is sufficiently unconventional to require it.
14.21 Tests required for propellers other than fixed pitch wood propellers. A propeller of such type shall be subjected to a 50-hour endurance block test on an internal-combustion engine rigidly mounted and of the same characteristics as the engine or engines in conjunction with which the propeller will be certificated for use, or on another engine acceptable to the Administrator. The test shall be witnessed by an authorized inspector of the Administrator and may be run without a stop or in periods of 5 hours or more each. The cylinder bore of the engine used for the test will determine the maximum bore of the engine with which identical propellers of this type will be certificated for use. The test shall be run at the proposed rated speed of the propeller with the propeller so adjusted as to absorb its proposed rated power. If the engine is not run at full throttle, and horsepower measurements are not possible during the test, manifold pressure readings shall be taken at frequent intervals. A suitable calibration curve shall be used to determine the power absorbed by the propeller during the test. The power rating assigned to the propeller by the Administrator may correspond to the corrected horsepower developed by the engine if the engine used for the test is of the type on which the propeller is to be certificated for use. In the case of s controllable or automatic pitch propeller, the pitch-changing mechanism shall be operated throughout the usable power range at least once for each hour of the test or the equivalent. The engine may be throttled to prevent over-speeding when changing pitch. After such 50 hours of testing, a controllable or automatic pitch propeller shall also be operated at as close to rated power and speed as possible for period of 5 minutes each at various pitch settings, i. e., at 1-degree intervals throughout the operating range when the design so permits. All variations in running characteristics of the propellers shall be recorded.

 14.210 A propeller of the above type which, in the opinion of the Administrator, is sufficiently similar to a previously certificated propeller of the same manufacturer may be subjected to a 50-hour flight test in lieu of the test outlined in § 14.21 provided that its airworthiness is demonstrated to the satisfaction of the Administrator by a comparative stress analysis submitted by the manufacturer. The stress analysis shall compare the pertinent aerodynamic, centrifugal, vibration, and torque impulse load differences between the respective propellers by a mathematical comparison, when possible, and by suitable curves plotted with the radius of the propeller as abscissa. Curves descriptive of the fairing of the propellers shall also be included when applicable. Such 50-hour flight test shall be conducted on an engine of equal or greater power and speed than that in conjunction with which the rating is requested. At least 5 hours of the test shall be run at the proposed rated speed of the propeller.

 14.211 It is recommended that metal propellers of this type also be tested by suitable methods to determine their natural frequencies within all ranges of major vibrations which are produced by the operation of the engines in conjunction with which such propellers are to be certificated for use. Such frequencies should be determined at all blade angles within the desired operating pitch range of propellers. Data covering these tests should be submitted to the Administrator in the form of curves and tables. The type of frequency should be described and the nodes located for each frequency.

 14.22 Tests required for fixed pitch wood propellers. A propeller of such type shall be subjected to a 10-hour endurance block test on an internal-combustion engine, or to a 50-hour flight test. The testing shall be witnessed by an authorized inspector of the Administrator at the discretion of the Administrator. In the case of a block test the entire test shall be run at the proposed rated speed of the propeller. In the case of a flight test at least 5 hours shall be run at the proposed rated speed of the propeller. Such flight test shall be conducted with an engine of equal or greater power and speed than that in conjunction with which the propeller is to be certificated for use.

 14.23 Inspection of a tested propeller. As prescribed in § 14.203, the log of the flight or block test shall include the results of a detailed inspection of the propeller after the test. Photographs of any failures or suspected failures shall be included. A propeller which fails during the testing is not eligible for certification unless the failure is of a nature such that the strength of the propeller is not impaired and a minor modification to the propeller will preclude the probability of future failures of the same type. Aluminum-alloy propellers shall be etched at all critical portions and then examined for minute cracks with a magnifying glass. Steel propellers shall be subjected to both a magnetic and visual inspection for signs of failure.

 14.230 A failure of a metal propeller is defined as actual breakage, cracking or permanent set of any part of any blade, hub, bolt, lock nut, spline or keyway; slipping of a blade in its clamping socket; seizing or pitting of any bearing; or jamming of an automatic or controllable pitch mechanism. A wood propeller will be deemed to have failed if the tipping pulls or cracks, if a glue joint opens, or if there is any local failure or crushing around the hub or a bolt. Similar considerations will apply to propellers of any patented composition or of other than conventional wood or metal construction.

 14.3 Military propellers. In the case of a propeller of a type which has previously been approved by the Army or Navy and for which the manufacturer desires certification by the Administrator, the following data shall be submitted:

    1. An application as described in § 14.200.
    2. A copy of the official Army or Navy endurance test report which was the basis for the military approval, signed by the Army or Navy representative who witnessed the test. It is not necessary for the manufacturer to submit this report when such report has been previously forwarded to the Administrator through official channels. When the report is being prepared by the military agency the Administrator, to expedite approval, may in the interim accept a copy of the official letter of approval of the propeller which letter shall include the military rating, the length of test, and the output and model designation of the test engine.
    3. Drawings as described in § 14.201.
14.4 Modified propellers. When a manufacturer desires the certification by the Administrator of a propeller which embodies only minor modifications of a certificated propeller of the same manufacturer, data shall be submitted as follows:

    1. An application as described in § 14.200.
    2. Drawings as described in § 14.201.
    3. Technical data which demonstrate conclusively that the airworthiness of the modified propeller is at least equal to that of the certificated propeller.
14.5 Procedure relative to type certification.

 14.50 General. The procedure and general requirements for the issuance of a type certificate shall be as prescribed in Part 01.*
* Note—Now in Part 02.
14.51 Sealed drawing list. When a type certificate is granted, a drawing list representative of the certificated propeller is impressed with the seal of the Administrator of Civil Aeronautics and is returned to the manufacturer. Sealed copies of the drawings may be used for this purpose in lieu of a drawing list. Inspectors of the Administrator may call for, and must have access to, the sealed drawing list or drawings together with any other pertinent drawings when making an inspection of the manufacturer's plant to determine whether the propellers as built conform to the approved data.

 14.52 Major changes. Any major change from the approved drawings must be approved in advance by the Administrator. A change will be deemed major within the meaning of these regulations if it adversely affects the reliability or airworthiness of the propeller. In general, a change will be deemed major when it decreases the airworthiness of a part the failure of which might prevent the aircraft from continuing flight. In all doubtful cases the decision of the Administrator shall establish the category within which a specific change will be included.

 14.520 Information accompanying a request for approval of a change to a certificated propeller shall include technical data, including (when necessary) stress analyses and reports of tests sufficient to demonstrate to the satisfaction of the Administrator that the changed propeller is airworthy. The report shall be signed and certified to by the responsible representative of the manufacturer. If the change is to a different blade shank size, engine shaft size, blade airfoil or propeller material, application shall be made for a new type certificate.

 14.53 Minor changes. On January 1 and July 1 of each year the holder of a propeller type certificate shall submit, for approval and file, drawings pertaining to all the minor changes made to the propeller during the preceding 6-month period.

 14.54 Reductions in diameter. A type certificate may provide for reduction in diameter from that of the propeller tested, provided that no increase in rating is involved. The diameter of a propeller blade may be reduced by cutting off the tip of a blade and fairing the immediate vicinity or by telescoping the outer sections of the blade. The drawings submitted shall show the details of each blade smaller in radius by 6-inch steps, which details may be shown super-imposed on a drawing of the original blade.
 
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