Increased Gross Weight - Wood Spar Decathlons

InvertedFlightProductions

InvertedFlightProductions

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May 6, 2020
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Hey everyone,

Does anyone know of an Increased Gross Weight kit that's available for the Wood Spar Decathlons and Super Decathlons? I know you can 'upgrade' a Decathlon to the 'new' standard as per A21CE with metal wings, extended gear and the 180 HP (360) engine and have a 1950lbs Normal Category.

Also does anyone know if the fuesalage primary structure has been changed over the years? Especially around the landing gear?

Thanks!
Hugh
 
Hugh,

The gross weight increase comes from the new wings so there aren't any options to get that with wood spars, AFAIK. The metal spar STC is for Citabria/Champ airframes only so there's no STC path to metal spars and even then, the Milman metal spars don't provide for a gross weight increase.

Primary structure is basically the same but there have been small changes. I'll have a bare frame back home sometime soon and I'll post photos when it's here. There have been some gussets added to reinforce tubing clusters but nothing structural beyond that that I'm aware of. A small diameter tube around the gear leg has been modified but it is only for the purpose of providing an attach point for the fabric where the leg passes through the fabric.

Hope that helps,
Bart
 
Just be careful and have good paperwork on board. The airplane will lift almost anything you can get in it.

When I put the Greek in back (she weighs 115#) I am at gross with full tanks, no baggage. I am not going to tell you I put her 300# brother in law in the back and it leapt off the ground. Nope. Didn’t do that.

Two guys and parachutes means you need to prove the tanks were not full.
 
This comes from an IAC "Technical Tips" publication, page 105:

file:///home/chronos/u-e3fbbe814d5e28e1fa8c738be4443f8432e0dfc7/MyFiles/Downloads/technicaltipsmanualvol1_0.pdf

"Dear Fred,

I have been asked to reply to your request for comparison differences in the Citabria and Decathlon aircraft.
Unlike the Cessna Aerobat, which is basically a beefed up Cessna 150, the Citabria and Decathlon are two different aircraft designed and certified independent of each other. For this reason, it would require a detailed description of both the Citabria and Decathlon fuselage and wing structure to properly describe the differences.
The fuselage of the Decathlon shares much of the same truss design of the Citabria, but structurally it is quite different.
*The material thickness of steel tubing is increased in many areas.
*The tail section has additional truss members.
*The wing attach and carry-through members are stronger.
*The fuselage is designed for 180 HP. The wing of the Decathlon is completely different and shares very few parts with the Citabria.
*The airfoil is a NASA 1412. This, for one thing, distributes flight load differently.
*The main spar is larger (wider and deeper).
*The rib spacing is closer (more ribs per wing).
*The front and rear wing struts are larger and stronger — adding greatly to its compression strength or negative flight loads capability.
The windshield of the Decathlon is made of thicker, stronger material and is supported with a center brace.
Another big difference is in the certification and operating limitations.
The Citabria is approved for aerobatic maneuvers listed on the placard on the panel. Only those maneuvers are approved.
The Decathlon is approved for a list of maneuvers and variations or combinations of those maneuvers which does not exceed the operating limits. Only the tail slide and lomcevak are not approved.
I have enclosed a copy of the Decathlon flight manual and the Citabria owners manual as a reference for you to compare operating limits and approved maneuvers in more detail.

I hope this explanation is adequate. If not, please do not hesitate to contact me. Sincerely, BELLANCA AIRCRAFT CORPORATION Richard M. Johnson Product Manager"
 
Just out of curiosity, does anyone know why Bellanca certificated the original 8KCAB for the same gross in Normal and Aerobatic categories? Structural strength is obviously not a limitation in the normal category if you can fly acro with the same gross weight. Was there some other flight parameter they were shooting to constrain, such as takeoff distance or stall speed? Or were they afraid that if they allowed a higher gross in normal, that pilots would be tempted to do acro without checking to ensure they were under the aerobatic gross?

The ACA increase seems like a pencil drill to me. Wing spar strength is not a limitation on normal GW, so changing from wood to metal should have no effect.

The Milman wing is not available for the 8KCAB, correct?

So, 15K to rebuild and cover my wood spar wings, or 30K for ACA metal wing and a piece of paper saying a full tank and passenger won't kill me.
 
There is a fine line between obeying regulations and getting really down in the weeds with them. Just carry enough paperwork to convince a fed that you are under gross. Or your insurance agent?
 
Big Ed said:
Just out of curiosity, does anyone know why Bellanca certificated the original 8KCAB for the same gross in Normal and Aerobatic categories? Structural strength is obviously not a limitation in the normal category if you can fly acro with the same gross weight. Was there some other flight parameter they were shooting to constrain, such as takeoff distance or stall speed? Or were they afraid that if they allowed a higher gross in normal, that pilots would be tempted to do acro without checking to ensure they were under the aerobatic gross?

The ACA increase seems like a pencil drill to me. Wing spar strength is not a limitation on normal GW, so changing from wood to metal should have no effect.

The Milman wing is not available for the 8KCAB, correct?

So, 15K to rebuild and cover my wood spar wings, or 30K for ACA metal wing and a piece of paper saying a full tank and passenger won't kill me.
Click to expand...
I think you will find that the ACA installed cost with wingtips and ailerons(which you will want if buying all new recovered and painted wings) is going to run around $38,000. Which is probably worth it if you keep the plane at least 10 years.
 
I bet I can find you new metal spar wings for $38 grand with a beat-up but operable Decathlon under them for $38 k total.
I am going to guess that the difference in used price for an early metal spar conversion aircraft is no more than $2 grand more than a wood spar in the same condition.

That is strange, because the annual spar AD is $500 a pop.
 
The ACA wings eat up the majority of that gross weight increase, but at least your wallet will be lighter.
Heavier airplanes do not fly better than light ones.

Most people seem to think max gross weight is a structural thing. It's not.Trick question? Keep reading.

How preposterous is it to think that my antique 7 series airplane, rated to +5/-2 would be structurally compromised by taking off 50 lbs over gross?

Let's do some horse math. A 1650 lb max weight at 5G is 8250 lb. If we were to create a "normal category" application we can use 8250/3.8G = 2171 lbs, and the structure would have no clue we did that.

Those of us with 7 series aircraft are a prisoner to the original type certificate which established the max takeoff weight for a Champ.

The answer to the trick question can be found in FAR 23.2120, which establishes minimum climb gradient, including what by now must be a non -PC "botched landing" (aka go around). I honestly don't know what regulation was used for CAR 3 and 4 cert basis but 2120 what is used now.

I don't have it in front of me but I think the botched landing requires a climb gradient of 300'/mile. My plane can do that even with a major density altitude penalty. As it is my plane out climbs all but a small handful of piston planes at my airport.

Champion and then Bellanca could probably have increased the max takeoff weight with 7GCAA , GCBC, etc. But when doing so now you have to prove to the FAA that the plane is strong enough, which would include a gear drop, etc.
ACA can just turn around and point to the 8 series Scout and see if you're serious about hauling more.

I've read different versions, but if the factory doesn't require a change to the landing gear then you should be able to get an STC showing that ACA didn't do any structural mods to accommodate the 100lb increase, so you shouldn't have to either. If they require using aluminum gear then you might have to do the same.

This is all theory of course, as I know the good old days of field approvals are long gone, at least here in the PNW.
 
Yes - shop time around here is $110/hr. It takes an hour just to get the inspection plates off and on. If you do it properly, it can take ten minutes for each bay with a Bend-A-Light and mirror. I always back it up with a tv camera. That takes another five minutes.

Some IAs require only a photo of your aircraft. Most airplanes really do need a hard look once a decade.

I am looking at one now with an autopilot, and zero documentation, other than a log entry that says "autopilot installed." It has gone almost a quarter century without STC paperwork or a 337. It is not ignorance; at least one of the IAs involved was pretty sharp. It was just "sure - looks like a clean aircraft. Gimme that logbook -where do I sign."
 
Per ACA, the base price for metal spar wings for a 7ECA, 7GCAA or 7KCAB is $24,500. The 7GCBC wings cost $26,250. New front struts are required and they are $1450, so it's really $25,950 for the non flap Citabrias and $27,700 for the 7GCBC.

For the 8KCAB the cost is $29,500, but the strus are optional.

Ailerons for all of the above are optional but cost $3430. So now you are up to $29,380 for a 7KCAB, $31130 for a 7GCBC. The standard ailerons cost the same for the 8KCAB but performance ailerons are $4160, so now we are up to $32,930 or $33,660 for the 8KCAB.

Now we have the options:
Spades are $595 for all of the above.
Wingtips are N/A or included for the Citabrias, but cost $900 for the 8KCAB.
Sun ray paint scheme is $1500, two color starburst paint scheme is $30000 and three color starburst is $4950, (7GCBC is slightly higher $1600, $3250 and $5200).
Turn key install is $1995, (and $2450 for the 7GCBC).
Wood crate is $1250 (which makes the install a good deal).

So a 7KCAB with struts, ailerons and spades and a sun ray paint scheme installed will run you $33,470. Re-use the old ailerons and it drops to $30,040.

The 8KCAB with ailerons, spades, wingtips, and a sun ray paint scheme installed will run you $33,895, or $37,155 with the performance ailerons, or $32,995 if you re-use your old ailerons.

-----

With that in mind, when I went 7KCAB shopping last year, I found that the price difference for metal spar wings in otherwise very similar condition aircraft was about $10K.

Digging into the paperwork and receipts for the 7KCAB I bought, previous owner #1 paid $19,115 for ACA metal spar wings as part of a 2002 to 2007 airframe rebuild (and the rest of the rebuild and recover cost about $20K). He sold it for $30K with a high time engine, losing $10K in the process. Previous owner #2 bought appears to have purchased it for $30K, then spent about $25K on an engine overhaul, $5K on a new prop, and $1.5K on a new exhaust, for a total of $61.5K spent on the aircraft and the necessary power plant related overhauls. He sold it to me with 150 SMOH for $60K and almost broke even.

Realistically, the metal wings increased the selling price on this particular 7KCAB by about 1/2 of what was invested at the time - or about 1/3rd the cost if it were done in 2020.

----

That's why I went looking for an ACA metal spar 7KCAB in the first place. It's a lot cheaper to buy a plane with them installed than it is to buy a wood spar wing aircraft and install ACA metal spar wings on it.
 
Kinda like remodeling your kitchen. No way you get all your money back. But factor in use and enjoyment and it becomes viable.

I put in a cement pond (said in Jethro Bodine accent) ten years ago. Cost me $30K. Maybe I'll get an extra $10K in resale value on the house. But take a look at this photo and tell me if you think we got our money's worth.

IMG_20160529_202535.webp

So it goes with airplanes. IMO it's madness to throw a bunch of upgrades into an airplane just for the purpose of selling it. The sole exception to that statement is if you are an A&P and enjoy doing the work. Then it can be a profitable hobby. Otherwise, if you want to sell it then just discount the price for the needed repairs and be done with it. Anything else is an emotional decision.

Now putting upgrades into a plane at the beginning or middle of your ownership, to get it the way you want and fly the heck out of it, that's a different story. Likewise for buying a plane that someone else has upgraded, as long as their price reflects market value, not "what I put into it" value.

Most metal wing 8KCABs I have seen are going for 6 figures. The cheapest one I have seen was $65K, and that shocked me because was so far out of line with the other listings.

Desert Rat Aviation in AZ offers a wood spar wing rebuild for $15K. Or I could probably get them opened up, IRAN, and recovered locally for $10K. The way I see it, if you know the damage and stress history of the wing since it was rebuilt, then cracks are not a concern. The only real downside at that point is the cost of the AD, and all those stupid inspection panels.
 
I guess I had forgotten that the metal spar Decathlon was heavier. I think Bart addressed that. The 150C/S metal spar Decathlon I mentioned before is as fast as my 180 Hp. Only thing is, there are expensive ADs against the factory metal wing. The intergranular corrosion on the machined aluminum lift strut fittings was truly scary.
 
And my impression is that the metal spar Decathlon at my airport would not be boosted anywhere near 10 grand. I don't know what the owner wants for it, but it has sat for three years. It is capable of flight. I bet it brings 40, in the end.
 
Big Ed said:
Kinda like remodeling your kitchen. No way you get all your money back. But factor in use and enjoyment and it becomes viable.

I put in a cement pond (said in Jethro Bodine accent) ten years ago. Cost me $30K. Maybe I'll get an extra $10K in resale value on the house. But take a look at this photo and tell me if you think we got our money's worth.

View attachment 2574

So it goes with airplanes. IMO it's madness to throw a bunch of upgrades into an airplane just for the purpose of selling it. The sole exception to that statement is if you are an A&P and enjoy doing the work. Then it can be a profitable hobby. Otherwise, if you want to sell it then just discount the price for the needed repairs and be done with it. Anything else is an emotional decision.

Now putting upgrades into a plane at the beginning or middle of your ownership, to get it the way you want and fly the heck out of it, that's a different story. Likewise for buying a plane that someone else has upgraded, as long as their price reflects market value, not "what I put into it" value.

Most metal wing 8KCABs I have seen are going for 6 figures. The cheapest one I have seen was $65K, and that shocked me because was so far out of line with the other listings.

Desert Rat Aviation in AZ offers a wood spar wing rebuild for $15K. Or I could probably get them opened up, IRAN, and recovered locally for $10K. The way I see it, if you know the damage and stress history of the wing since it was rebuilt, then cracks are not a concern. The only real downside at that point is the cost of the AD, and all those stupid inspection panels.
Click to expand...
Very good point? What puts a smile on your face.👍
 
Bob Turner said:
Only thing is, there are expensive ADs against the factory metal wing. The intergranular corrosion on the machined aluminum lift strut fittings was truly scary.
Click to expand...

I cannot find any 8KCAB accidents in the NTSB database caused by wood spar failure. Not one. There were two wing structural failures, but they were clearly caused by overstress.

OTOH, there are two fatal accidents early in the metal spar era where wings just snapped right off.

I've just about convinced myself that recovering my wood wings is the way to go.
 
There ought to be some common sense in that AD. The Decathlon spars are apparently way more robust than the Citabria. Looking at every square inch of all four surfaces is a joke - which is why Rainbow sells a special skylight for the front spar outboard of the strut. Seems to me the AD would be a 30 minute deal if we inspected the critical areas and just generally looked elsewhere, like we do on early Cubs.

Yeah, Ed - these are good wings, and if your tanks pre-date the 1990s you should have very few problems. There are a few minor things in there that can break if you like violent aero - snap rolls etc - but they won't bring you out of the sky.
 
The owner of the shop I got my pre-buy done at grew up working in a shop that serviced mostly Stearmans and crop dusters. He said he had seen wood spars take massive damage and not fail completely.

I don't know much about the AD process but I assume the only counterbalance to the FAA would be the manufacturer. Since Bellanca is defunct and ACA would be happy to see wood wings go extinct, the FAA had no incentive to be reasonable. I'm sure they don't give a damn what some type club thinks.

I've dealt with federal agencies enough to know the only way to get their attention is to have a pissed off congressman on your side. If that congressman is on the committee that controls their funding, you bet they will tread carefully.
 
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