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I’m repairing a flap on my 1959 PA-22/20 and I'm trying to identify the kind of aluminum piper used. I know the industry changed the way they identified sheet aluminum alloys from a 2 digit identifier to a 4 digit identifier somewhere along the way. I’m looking for a cross reference of some kind that would help me translate the old identification to the newer alloy identification.
The only markings I can make out on the original part are;
3S
H14 (hardness)
24S-1
.02 (thickness)
Daryl
2024 t3 is what you need . thats the closest to what was used during and just after ww2 not sure when they changed the numbersQuote:
Originally Posted by AVPacer
3003-H14 is what was used for the leading and trailing edges. 2024-T3 for the spar and ribs.
The old Aircraft Spruce catalogs used to have a chart.
Here's the chart Turtle referred to: http://www.aircraftspruce.com/catalo...s/aluminfo.php (Scroll down).
As Turtle said, 3003 is the equivalent of 3S apparently. I learned something I didn't know previously as a result of the search that turned that up :)
3003H14 is pretty soft stuff when compared to 2024T3 which feels more like a clockspring. Considering that the harder material drills and cuts better & is a lot stronger, you may want to just use 2024T3. It does cost a little more but those cauliflowered leading edges you see on Cubs are pretty much due to the use of 3003H14.
I'd use what Piper used. In most cases when someone made a part with a "better" grade, it didn't last as long as the original due to things like cracking.
Mr. Piper was almost as smart as he was cheap.
Actually, 2024T3 is pretty much approved by the FAA to replace the older grades of aluminum used in most aircraft, including Pipers. 7075 and some other less common grades excepted. Give AC43.13 a read. For a flap, 2024 is certainly the preferred material.
I will agree that Mr. Piper was cheap.
Best of luck,
Wes
N78PS
Quote:
Originally Posted by WLIU
Wes,
I am failing to find any FAA information that even suggests that 2024 can be used as a blanket substitute. Quite the opposite is true as most statements advise to using the same material both in dimension and composition as the original part. This would seem correct to me as it would be foolish to think one could alter a material at their whim with no reguard for the performance of the finished component. AC23-27 covers the subsititution of 4130 for 1020 steel, but has no such approval for any aluminum alloy. 43.13 as well does not seem to grant this approval. I am sure one could do a material change provided the appropriate design and engineering work completed for approval. How this would be worth is I dont know as it seems very straightforward to know what the part was originally designed and approved with. Another option may be to see if there has been any previous approvals done for the same application and follow suit. In any event, my guess is that this would be a major alteration as it is a structural material change. If you have any documention to the contrary you would like to share I would welcome it.
3S is not necessarily older than 2024.Quote:
Originally Posted by WLIU
The older "grades" still exist under their new numbers, just like 24s = 2024, and are still chosen today based on their properties. The hardness and memory of 2024T3 would be detrimental for a lower cowl, for example. People have done it and most cracked from vibration. Using the original 5052 solved the problem.
Then there is the issue of the law. This is a certified aircraft. AC43.13 comes in when no other data is available. In this case, we know the original materials and they are still readily available. Even the individual parts for the flap are still available. To substitute materials would be re-engineering the part. Even though the substitution might seem reasonable, I still wouldn't sign it out.
As mentioned above, although 2024-T3 is todays standard alloy for aircraft use, Piper did use softer (and cheaper) metals back then.
The 3000 and 5000 series alloys were popular due to being weldable.
A better replacement than 2024-T3 would be 6061-T6, only (about) two thirds the strength of 2024 but stronger than 3003, is still weldable and cheaper than 2024.
Many of the light end kit manufacturers use 6061-T6 these days..
Aaron Novak hit the nail on the head. His answer is right on as far as the FAA is concerned. The only thing I would suggest is that AVPacer try to verify that the "3S" sheet is the original Piper-installed material and not a later field-fabricated replacement part. Sometimes the maintenance manual specifies the materials used in various parts of the structure.
If you look at AC43.13-2B, Chapter 4, Section 4 Metal Repair Procedures, 4-53 Selection of Aluminum for Replacement Parts, you see that there is a alternative allowed as "If another alloy is being considered, refer to the information on the comparative strength properties of aluminum alloys contained in MIL-HDBK-5.". So MIL-HDBK-5 gives you the properties of modern alloys.
Then in 4-58 Repair Methods and Precautions for Aluminum Structure states in paragraph b Repairs to Aluminum Allow Members, "Make repairs to aluminum alloy members with the same material or with suitable material of higher strength.".
So the fine print of this approved data allows for materials substitutions done with appropriate justification. You can not just willy-nilly substitute one type of aluminum for another, BUT you can substitute a higher strength aluminum for a lower strength one. That is the basis for my comment that you can use 2024T3 for most parts.
You will note that all of the approved repair data in the paragraphs that follow my reference above refer to the use of 2024 sheet. I do not believe that is an accident.
You are unlikely to get Piper to tell you what material was used for a flap skin. That said, there are folks out there who will sell you FAA-PMA replacement parts and you can do the repair with those parts and not worry about justifying the material.
Best of luck,
Wes
N78PS
Wes,Quote:
Originally Posted by WLIU
I believe what they are stating is basicly common sense. If you have to substitute a material, go up in strength, not down. However this as I read it does not grant the ability to change material without formal approval. The key here is that using 2024 in place of 3003 would be a deviation from the manufacturers approved design. Tensile strength alone is but a small part of the materials properties. Changes in stiffness of a control surface can lead to flutter issues and component life issues just to name a couple. In any case, if one wanted to do a material change, do your homework, get it approved and fly safely.
Changing a control surface skin from 3003 to 2024 of the same gauge will have no effect on the stiffness of the structure, as all aluminum alloys have essentially the same elastic modulus.Quote:
Originally Posted by Aaron Novak
Substituting for obsolete material with that of greater strength is a minor alteration.
Exactly! 3003/5052 alloys are good for welding and compound forming, but as a tradeoff, have mediocre strength.Quote:
Originally Posted by Matt Gonitzke
2024T3 has excellent fatigue properties but its forming is generally limited to simple bending with adequate bend radiis - unless you go thru a heat treat and aging process (then it is called 2024T42) starting with 2024T0. If you are forced into the agony of this, you probably are making an alteration that must be approved as a major substitution.
But flat and simple bent parts can easily substitute 2024T3 for 3003 and get the benefit of better fatigue resistance and better machining and drilling. A lot say 2024T3 will crack when 3003 won't, but that flatly isn't true in most cases unless there is a considerable locked in stress or a too-sharp bend in the installed finished part. The fatigue and cracking properties of 3003/5052 are inferior to 2024T3. DAMHIK.
Elastic modulus is one part yes. The point I was trying to make is that from an engineering perspective, 2024 is not a direct substitute for 3003. Im still thinking that this being a flight surface repair, plus a change in material/design that it would fall into the Major Repair reguardless (or alteration depending how the IA wants to do it). This is where the IA and local FSDO come in. Of course if you just were to make a new part to the original specifications, then its just a major repair and the thing can keep flying for another 50 years. Sometimes more harm than good can come from "upgrading" materials.Quote:
Originally Posted by Matt Gonitzke
Interesting discussion. It touches on some legal and safety aspects of airplane repair. I don't expect it's too helpful for Daryl though. Anyway Daryl, there's one more reference you may want to check. It's from the Code of Federal Regulations, Part 43, Maintenance, Preventive Maintenance, Rebuilding and Alteration. You can access it from the FAA website:
Appendix A to Part 43—Major Alterations, Major Repairs, and Preventive Maintenance
(b) Major repairs —(1) Airframe major repairs
(xxi) Repairs involving the substitution of material
Regardless of what you read on this forum, it's your IA who will have to approve your work. It may be a good idea to discuss the question with him/her before you get too far into it.
Hey, Dude said "repair". Didn't say re-skin or replace, or rebuild. Nobody has asked yet what what type of repair. If he's asking for a material for a simple patch I would think it would be much less important than a repair of a greater magnitude. I wouldn't have any problem with 2024 T-3 for a simple patch or a doubler for a small crack if no forming were required. Let's not make a grandfather clock out of a PA-20.
True the scope of the conversation did go beyond the OP question. However it must be kept in mind that "information" given in a forum is open to the eyes of all that read it, and so when there is a statement of questionable nature given, it is the obligation of others to counter or correct it. If it were not for this there would be more falsehoods that truths floating around than there already are.
And it can be approved under 43.13Quote:
Originally Posted by Raleigh
43.13 Performance rules (general).(a) Each person performing maintenance, alteration, or preventive maintenance on an aircraft, engine, propeller, or appliance shall use the methods, techniques, and practices prescribed in the current manufacturer's maintenance manual or Instructions for Continued Airworthiness prepared by its manufacturer, or other methods, techniques, and practices acceptable to the Administrator, except as noted in § 43.16. He shall use the tools, equipment, and test apparatus necessary to assure completion of the work in accordance with accepted industry practices. If special equipment or test apparatus is recommended by the manufacturer involved, he must use that equipment or apparatus or its equivalent acceptable to the Administrator.(b) Each person maintaining or altering, or performing preventive maintenance, shall do that work in such a manner and use materials of such a quality, that the condition of the aircraft, airframe, aircraft engine, propeller, or appliance worked on will be at least equal to its original or properly altered condition (with regard to aerodynamic function, structural strength, resistance to vibration and deterioration, and other qualities affecting airworthiness).