National Aeronca Association Bulletin Board

What are the done sideds to rebuildingng 7ac wings with the stc metal spars(I do not remember the name) I would like to hear from some one who has done this?

Down sides are that the Millman metal spars are more expensive! Course they last a long time but then a proper piece of wood spar did as well.

The reason for the spar mod was that there was a crash with a Citabria where the wing departed the plane in flight. Turned out that the spar failed.

The 7 and 11 series of planes need to be inspected once then they are legal to fly again without futher inspection unless the plane has a 90 hp engine or larger installed on it. Personally I would not mind seeing planes spars inspected every few years just to make sure they are fine.

The last time I heard there was not a large number of planes flying that had been found with any defects so most people feel that the AD and conversion to a metal spar was a CYA. Most Aeronca airplanes are not under the stresses that a aerobatic airplane undergoes so the wood spar should last for many years with no problems.

JoeA

Groundloop,
My 7AC Champ is in the final stages of a complete custom rebuild, and I had the Milliman metal spars installed. The IA doing the work said that they were one of the finest STC's he had ever seen. The quality of the workmanship and delivery ( by air ) was fast and extremely well packed. They are very expensive, compared to wood ( $6000- installed), but give me a great peace of mind for taking my family up in the future. It's been my experiance that I'll get it all back on resale some day. To date their are no AD's on the metal spars, which is a plus and I don't need all those additional special inspection holes in the wing. Their are wooden spars available for much less, that have a history of 50 years +, so you do have a choice. Good luck!
"Ole"

I'm sure the metal spars are a fine addition, although all it takes is a little extra stress and a possible crack could develop and spread. I could live with either wood or metal spars depending what's on the plane. Much depends on how the aircraft is being used and stressed, anyway. That being said, the wood spars have proved their worth and longevity over the past 50-60 years. Regarding inspection of wood spars: the key inspection points are now well known and extra inspection holes and panels are in place and the spar (like any other critical component) should be carefully inspected every annual inspection (as should have been accomplished before the AD anyway). I'm less than happy with the upper inspection holes as they could allow water to leak through on to a critical part of the spar. Kind of a "catch 22" though as it's pretty hard to inspect the upper part of the spar at the strut doubler without some opening.
Anyway, my two cents worth.

I rebuilt my champ in the 90's. I found both of the main spars cracked under the attach brackets. My guess is they were cracked when the plane was ground looped in 1947. The plane was a sprayer in the 50's and 60's, with a 115 Lycoming, and the wings never came off. During the rebuild, I put in new main spars, and another 115 Lycoming. For the annual wing inspection, we do NOT have any holes cut in the top. In my opinion, the AD for the spar inspection, is a waste of time and money.
Give me the wood spar anytime.
Don

I rebuilt both of my wings using the Millman Spars. I also purchased their leading edge kit and was very pleased with both. The rebuild was pretty straight forward and I saw no glitches. The only place where there is a question is that the top of the main wooden spar has a bevel on it and the aluminum spars do not. So you have to make allowance for the ribs to clear the aluminum spar. Once you figure that out it goes together pretty quickly. I live at Lake Norman Airpark and am lucky to have an IA as a neighbor and he has been supervising my work. It takes 30 seconds from the house to my hangar. Can't beat that.

Howard w4ppn@aol.com

Actually, the straw that broke the camel's back for the AD was an 8GCBC banner tow aircraft. Several incidents before that that were brushed off as inadequate inspection on the part of the guy signing the annual. This time, the hired pilot's mother got her congressman involved....the rest is heated debate and history

Not trying to hijack the thread, just offering history.

Jerry,

Thanks for the input. Any history would be appreciated.

Good to see someone with your experience on the board!

Joe A

I say that good spars are a good thing wood or metal. The AD for the spars was put in place to lay to rest any questions about the condition of any given Aeronca. The bad thing is that it caused a lot retrofitted holes to be put into many otherwise good-looking Aeroncas. Even the ACA factory spars, not Milman mind you, have their own AD so condition is everything. I think it's a personal choice about whether to go metal or keep with wood but unless you ground loop or put your bird on it's back, I feel there's really no need for the inspection per the AD. The Champ started out as trainer with a gross of 1220 pounds and ended up being billed as an acro machine weighing 1650 pounds (maybe more) using the same spars. I think this speaks well for the strength and integrity of the spars. However, since Ceconite coverings have become popular, it can be decades before before a wing is taken down and given a close look. I have Champ project that I bought with Rainbow spars and I am delighted with them and their lower weight and cost. Having said that, I will still put in those darn inspection holes because one day I may need to sell it and the next guy may not be so sanquine about the spars.

I have a 59 7EC that had been in california 35 years after having aircraft Spuce spars put in.It did not have a lot of inspection holes and who knows how many pencil whipped inspections had been done on it.Even using a borescope I could not see the spar in between the inspection holes it had.I wanted to have a good look at what would be keeping me from seeing the ground get near real fast so I tore the fabric of of one wing to have a look. One spar appeared to have a split in it by the lift strut attachment area. How long has it been there who knows. Would it have failed maybe. I like Life and enjoy my family and did not let the cost of the Millman spars get in the way.If I ever sell the plane It may be a big plus. It had 35 year old Aircraft spuce spars in it and I did not feel putting them back in or replacing one would make sence. Aviation is a great way to have fun. Sometimes it will cost money and One time it will cost you your life. Just my way of looking at things..

The owners don't want them, the mechanics don't have enough of them.
The best thing is, for all the owners to have an A&P+IA. That way you can
sign off your own Annual. The name of the game is SAFETY, what you
can't see could kill you. Food for thought!

Hello all,

I am in the process of installing new Milman Spars and I am working on the tip bows. How did you attach the tip bows to the ends of the spars???

All else with the STC was clean and easy.

Thanks,
Mark
NC84450

Mark,

If you either sign into the forum or leave a email address possibly we can get someone to contact you and lend a hand.

Joe A