USAF H-19A paint question

Thanks John for the info. I have been side-tracked since this dicussion started and have not done much research. I find the topic interesting because while magnesium is strong and as you said and used more in the earlier days the topic got my curiosity up, because like you said, it corrodes and cracks so easily. While it is strong it doesn't have the flexibility that aluminum has. Anyway thanks much for the info and I do plan on taking some time and really researching the early uses of magnesium in aircraft production.

Charlie

Charlie, I think the use of magnesium for skin and structure was a WW II development.  I think its use was most common after the war, one use I know of is for the ailerons on early Beech Bonanzas.  As time in use developed, the short life due to corrosion and cracks became more apparent, and the use in later aircraft was discontinued.  It was used because as you say it is stronger than aluminum of equal weight, but the maintenance requirements are pretty high due to the fact that it must always be protected by a finish of some type.  Our CH-37's never got to looking too shabby, as they were refinished fairly often.  Well, except for the constant external and internal grease and hydraulic fluid they slung everywhere.  As for the early Bonanzas, almost all have been retrofitted with aluminum control surfaces.

As for magnesium on H-21's, the covers over the drive shafts are skinned with magnesium, the one we have at McClellan is under repair in that area, and the skin is toast.  Don't know about the rest of it.

John

Retired Gunpilot wrote:

From my research last night I found that magnesium products are casted products which leads me to believe that they would not be used as a skin. When I looked up aerospace magnesium manufacturing I found references for transmission cases, gearboxes, and brake parts. In the automotive industry it is used for bumper supports, seat frames and many other structural parts. Another issue is while magnesium is stron and light weight it does not flex, it cracks. So if you need any flexibility built in to your structure I would think magnesium is the last thing you would want to use. I still have more research to do but that is what I found so far. Charlie

Supercobra,

  No worries. I think we are all basically trying to say the same thing, but in different ways.  As you say, the all aluminum construction of otherwise mag parts has been well reported for Navy and Marine Hueys.  Like you I never even gave mag skin a consideration.  Sorry my language isn't more precise sometimes. Anyway, I haven't run across a paragraph in the dash 20 yet that actually refers to ANYTHING being magnesium. All the parts that they list materials for are either aluminum or steel.  However, there is no info on the major structural components materials (that I can find anyway).  Therefore, it seems like the transmission and major structural components are the only major parts left that could be magnesium.  The quest for difinitive data continues....

     Ray

rotorwash wrote:

Skin is aluminum based on the TM manuals I have.  Like I said, I thought I had this worked out. Supercobra, where did you get your data on the frame/stingers?  Is it somewhere in the dash 10 cause I didn't see it, just info on the skin of the doors and such.       Ray

Sorry, that was more of a question than a statement as it seems the conversation shifted frame mag frames, members, stringers, to mag skin.  I've read several places (and as others stated here) that one of the differences between the Es, Ks, Ls, and other Hueys was that they didn't use mag anywhere.  I assumed that the mag was structural and not the skin. 

supercobra wrote:

rotorwash wrote: "The frame/stringers are magnesium but is the skin?"  The stinger is supposed to be tubular steel.  This is from the 1972 UH-1B dash 20 maintenance manual.   Ray " border="0" /> I said stringers not stinger!  An alum or mag stnger wouldn't be much good!

 Supercobra,

Whoops, sorry about that sir!  I was wondering when I typed that why you would mention "stingers."  Geez, maybe I need glasses!

     Ray

rotorwash wrote:

"The frame/stringers are magnesium but is the skin?"  The stinger is supposed to be tubular steel.  This is from the 1972 UH-1B dash 20 maintenance manual.   Ray " border="0" />

I said stringers not stinger!  An alum or mag stnger wouldn't be much good! 

JosephOsborn wrote:

My best friend's father was an SA-16A flight engineer back in the early-mid 50's.  Those planes appeared natural metal but were painted for corrosion control and appearance.  Taking a bath in salt water was a common task for these planes.  His photos of the SA-16's and H-19's from that time show the same basic "look" to the finishes.  They aren't super-shiny like a highly-polished jet interceptor.

Thanks, that makes a lot of sense. Regardless of the material if it has pontoons it would be expected to land in the water, while obvious I had not even considered that.

I'm glad my "simple" question was able to stir up some discussion, its been too quiet in these parts lately.

My best friend's father was an SA-16A flight engineer back in the early-mid 50's.  Those planes appeared natural metal but were painted for corrosion control and appearance.  Taking a bath in salt water was a common task for these planes.  His photos of the SA-16's and H-19's from that time show the same basic "look" to the finishes.  They aren't super-shiny like a highly-polished jet interceptor.  

Guys,

  I also am going therough the UH-1B dash 20.  It's over 900 pages, but I'll start a new thread with as much info as i can find (or maybe Mel can start one if he gets finished first).  There is info about many structural parts and their composition.  I say the structural beams are magnesium, the skin is aluminum until further notice.  

Aaron, we have really strayed from the original question.  I'm headed to Rucker next week.  I'll check and see what i can find on their H-19's.  Good luck with the build and I look forward to seeing your progress.

    Ray

From my research last night I found that magnesium products are casted products which leads me to believe that they would not be used as a skin. When I looked up aerospace magnesium manufacturing I found references for transmission cases, gearboxes, and brake parts. In the automotive industry it is used for bumper supports, seat frames and many other structural parts. Another issue is while magnesium is stron and light weight it does not flex, it cracks. So if you need any flexibility built in to your structure I would think magnesium is the last thing you would want to use. I still have more research to do but that is what I found so far.

Charlie 

Guys,

My memory was "refreshed" by the UH-1E pilot of Collin's Foundation's bird last week when he bought up the major difference was the use of all aluminum on the "E's" versus the magnesium tail booms of the "C's".  This was for corrosion control for the shipboard operations.  I have a -20 I can read through next hitch home to see what I can find.  It may well be the main attach points and stringers were magnesium and the skin aluminum.  I've been away from it way too long.  I'll also ask Mike Gunnels, he is still active duty in the LANG and working on the last 4 Hueys out of Alexandria.

Charlie,

I'm well aware of what just 24 hrs of salt water can do to the engine and transmisson cases made of magnesium. 

From my 40 year old memory, I remember them telling us in the Huey repair school at Rucker, that the tail boom was made of magnesium.

Also when magnesium burns, it burns hot and Class A, B, and C class fire extinguishing agents will not work, it takes a Class D agent

I knew you were talking about the skin versus stringers. I was surprised the stringers might be magnesium. Until today, I thought the only place magnesium was used was on gearboxes, transmissions and a few misc parts. I guess some structural supports might have been magnesium. I just never thought about it though, until today. The discussion has brought up some interesting questions.

Charlie

Charlie,

  I always understood the skin was aluminum (as the TM i have indicates it is) but thought the structural beams and such were magnesium.  Sorry if you got the impression I was talking about magnesium skin. Anybody ever seen the beer can repairs in country?  Those were aluminum for sure!

    Ray

Man, did we start a debate or what. The burned Hueys you have photos of is what happens when the magnesium burns. It usually can not be put out and the aluminum just melts along with everything else. That is one reason I did not supect Magnesium as the skin. Maybe the stringers were a mix of magnesium and aluminum, I do  not know anymore and will need to do some research to find out. When I worked at a FAA repair station that overhauled helicopters I never saw magnesium ordered, it was always Aircraft grade aluminum. My memory slips me but I for some reason I remember the number T11 Aircraft grade aluminum. Many times we stripped a tail boom or skin off a overhaul bird and put new skin on it rather than doing a patch. Magnesium does provide strength and is light weight, but I just never heard it used for skin. That is why I asked earlier when it was mentioned to be used on the H-34 and H-19. In fact when we stripped a bird down to the skin we would pour an anolodize (not sure on speeling) on it to etch the aluminum so primer would ahere to the metal. 

BTW, have you ever noticed in most burned up helicopters, the transmission and gearboxs are usually no where to be found. Magnesium

Anyway, it is a good discussion and takes our minds off model building for a night.

Charlie

 The stinger is supposed to be tubular steel.  This is from the 1972 UH-1B dash 20 maintenance manual.

  Ray

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It doesn't help much with the magnesium vs aluminum debate but thin aluminum as used on aircraft will melt away to nothing pretty easily, in fact aluminum engine blocks on cars frequently become a puddle under the car in garage or wildland fires and even intense car fires.

I found some info to further confuse things, various aluminum / magnesium alloy blends are very common in the aerospace and high tech automotive industries. So it seems likely what one reference calls an aluminium alloy, another may call a magnesium alloy.

Skin is aluminum based on the TM manuals I have.  Like I said, I thought I had this worked out. Supercobra, where did you get your data on the frame/stingers?  Is it somewhere in the dash 10 cause I didn't see it, just info on the skin of the doors and such. 

     Ray

Melgyver wrote:

Charlie, The Huey tail booms are magnesium except the E's made for the Marines were all aluminum.  I don't know what the "N's" for the Navy and Marines are made of but suspect aluminum.

The frame/stringers are magnesium but is the skin? 

Retired Gunpilot wrote:

As to bare metal, I can not find a single image of it. As I said earlier, I could be wrong and might be confusing it with another aircraft I saw when I was a kid. As to the magnesium skin I'm still researching that. I had seen the article you mentioned at Global Security but did not see any reference to magnesium usage. While I'm not doubting the information, I am just real curious to know why magnesium was used. Magnesium is normally used in components that need a lot of strenght but need to be made as light as possible. That is why you see transmission cases and gearboxes built using them. The bad thing about magensium is it can not take salt water and when it burns it can get so hot it can not be put out. Anyway, if you paint yours silver you should be authentic. Whether it was made out of magnesium is not important, just real interesting. Charlie

I suspect you answered the question, but I have not found anything to support it. Magensium was most likely used for it's strength/weight benefits in early helo's. Weight was more of a factor before turbine engined helos. Also the Navy would be the service more interested in salt water corrosion then the Army or the AF

You guys are killing me.  I thought i had this straight.  I know that the UH-1E, TH-1L, UH-1L, and HH-1K had aluminum frames as they were designed for the Marines and Navy.  However, I thought practicaly the entire airframe on Army birds was magnesium.  Please correct me here if I'm wrong in that assumption.  Here's some pics of a sapper attack on the air base at Bien Hoa from Bob Coveney's Picasa page.  I was led to believe that it was the magnesium that made a Huey practically melt down to the skids during a fire like this.  Right or wrong?  Inquiring minds want to know.

Ray

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Hey Mel that is news to me also. Have you ever seen a helicopter pulled out of the Gulf and what it did to the magensium? This is really interesting. I helped reskin a 212 tailboom with our sheet metal guy once and I remember using aluminum on it. Granted that wasn't a Huey but this thread has got me interested now on why magensium was used as skin. I'm going to have to do some serious research now, because you'll got me wondering why?

Charlie

Charlie no problem on the memory thing, I'm old enough to have had similar issues myself.   

I'm also getting the feeling that unlike fixed wing aircraft most helicopters use a variety of materials for their skin which would make an unpainted aircraft a wierd patchwork, not the attractive gleaming surface of a Mustang, Sabre etc. The H-21 is the only helicopter I have found many photos of showing a natural metal finish.

Silver it is then, thanks guys.  

Charlie,

The Huey tail booms are magnesium except the E's made for the Marines were all aluminum.  I don't know what the "N's" for the Navy and Marines are made of but suspect aluminum.

As to bare metal, I can not find a single image of it. As I said earlier, I could be wrong and might be confusing it with another aircraft I saw when I was a kid. As to the magnesium skin I'm still researching that. I had seen the article you mentioned at Global Security but did not see any reference to magnesium usage. While I'm not doubting the information, I am just real curious to know why magnesium was used. Magnesium is normally used in components that need a lot of strenght but need to be made as light as possible. That is why you see transmission cases and gearboxes built using them. The bad thing about magensium is it can not take salt water and when it burns it can get so hot it can not be put out. Anyway, if you paint yours silver you should be authentic. Whether it was made out of magnesium is not important, just real interesting.

Charlie 

It's hard to find good info on the H-19 but I finally did find a good write up at Global Security.

John, you are right, like the H-34, the H-19 used a lot of magnisium in the airframe and skin. The article says it had the highest percentage of magnisium used in any aircraft up to that point.

Charlie, according to the Squadron book the H-34 did have a magnisium skin, later versions eventually adopted more conventional materials.

Thanks

Using Magnism for skin would be the first I ever heard of. Have you ever seen what salt water does to magnesium. I have pulled a few aircraft out of the Gulf and the transmission casings and gear boxes and any other magnesium parts are immediately scrapped, because it basically melts. Normally the only thing I remember being magnesium on helicopters are gearboxes, transmission cases and some other miscellaneous parts. Of course I could be wrong and will do some research so I am not putting out wrong information.

Charlie