Aerobatic with 7ECA with wood wing spars - Comments

C

Cita67

New member
My 7ECA is and old one, 1967. Spars are made of wood.

Can i do aerobatic with those old wood spars? (i know the aircraft is made to do aerobatic but since it has 45 years!)
Should I limit the aerobatic figures?
Is there a limit time on wood spars to do aerobatic?

All your comments are welcome!

J-P
 
J-P

The reason wing spars were made of wood is that wood is stronger, lighter and more flexible than aluminum. Also, wood can be visually inspected for damage unlike aluminum.

As added reassurance we have an AD that requires an annual inspection of our wood spars which, if no problems are found, should give us that warm, fuzzy, confident feeling that our superior wood spars are still as good as new :D .

Ron
http://www.advancedtailwheeltraining.com
 
I have a 65 ECA that I bought last April. I have not yet done any aerobatics, but plan to do some mild stuff. Rolls, loops, spins.

We did an inspection of the spars, but the annual is due next month and I plan to participate in a thorough spar inspection as well as tending to some other issues. If all goes well, I'll put my aerobatic instructor in the back, strap on the chutes and go for it.

Dale
 
The wood spars are nicer for a lot of things, Acro is one of them. Even if you have some kind of issue (very unlikely) chances are the wood will give, but not break, allowing you to limp to an airport. Even if I find cracks in my spars (two years, no issues yet) I'd never spend money to go to metal. I'd get a set from Rainbow.
 
Thats why all the other new airplanes use wood. Oh, wait...

Edit:
Not to be mean, but you have laymen responses. If your wood wing is in good shape and has its regular inspections, and you dont start working nails out (this happens slowly, BTW), then the wood spar is fine for what the airplane is published to do. You are safe. HOWEVER, when someone says its better because its more flexible, the hair on the back of my engineer neck stands up. People need to learn some basic aeroelastics before you type. I have writen at length about the differences. Its not hype, its nerdy engineering. Its also dry and boring (I never said I was an exciting writer).

http://www.amerchampionaircraft.com/NewWings/WingEngineering.html

Now, we never expect someone to panic and drop what they are doing to convert because...well, its easy to convert, but it sure isnt cheap. Apologies if I come off badly...http://xkcd.com/386/
 
Jerry Jr,

Not sure I understand much of the article on "http://www.amerchampionaircraft.com/New ... ering.html" but If I understand something, when I do aerobatic with those wings, every thing will come loose in the wings... so not a great idea. I plan to do aerobatic with a flight instructor in March or April and from there I'll see if I like it (Will use his airplane). If I like it a lot, Replacement of the wings or the airplane will be considered!!

I don't really care about performance improvement, but I care a lot more for safety...

Interesting to see difference in opinions!

J-P
 
Well...
What's better is fact, not opinion.
What's good enough for you is the opinion. Wood can be fine for most people [who take care of it].

Taken to the other extreme: An Extra 330 is better yet at acrobatics...it doesnt mean you have to buy one to enjoy acro safely. :D
 
Jerry, believe it or not, I've read the WHOLE thing on ACA's website. It's not hard for me to justify the cost of the factory wings since I'm getting ready for a complete cover job on mine anyway. The simplistic view is that in my OPINION, the wood is better for some things. I didn't say it was stronger, or stiffer, but better.

Of all the airplanes that have had wood spars with the compression cracking issue, how many of them have had a catastrophic failure?

I like how the flexing of the wing makes the aircraft ride in turbulence. I like the field serviceability if it's damaged in off airport landings. I like that the wing will 'give' rather than snap in an overload scenario. Yes, some of the design compromises have led a couple of AD's that require repetitive inspections. Some of that could probably be overcome with AMOC's that nobody has bothered to get... for instance, using screws instead of nails to hold the ribs to the spars.

One this is very clear, if you inspect the wood spars regularly, and they are crack free with the nails firmly in place, there is no more risk doing acro in them than on a metal wing airplane. I've done +4/-1.5 a few times in mine and nothing fell off.
 
Fair enough. Like I say. We are not saying you MUST buy them. They are expensive to build and therefore purchase. Like I said, 'good enough' is the term. And if the wood is taken care of (and the nails), its fine. The all-wheel drive version of my car is better for traction, but I can live without for the gas savings. (Although, I might have said something different while driving last night...stupid Wisconsin weather!).

osxuser said:
Of all the airplanes that have had wood spars with the compression cracking issue, how many of them have had a catastrophic failure?
Click to expand...

Too many. The straw that broke the camel's back was a 22 year kid flying banners for a company. I had to talk to his mother, personally. She already had her congressman involved at that point too.
 
I'd be interested in actual numbers of in flight failures. There is a lot of mis-information out there, but was told that you've had factory metal wings fail too.

In some ways, one failure/fatality is too many.
 
No metal spar failures. Had a strut fitting fatigue once. It did not fail; I think part of the frame failed on that one. The wings were both intact. Either way, that will flag an AD with the FAA. Thus, we have one in 1996 and a redesigned fitting.

99% (if not 100%) of wood spar failures were due to previous damage to the spar that went undetected. Pretty much never happens on plain old normal flight. Stressful maneuvers like acrobatics or a pull-up after a banner pick up. But this should be obvious.

Been the accident correspondant for us to the NTSB for over 20 years. Whats the biggest killer? Accelerated stall into a spin at low altitude. Can do that in most anything though.
 
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