160 HP engine and wood spars

AKpilot

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Oct 30, 2019
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#1
I own a 1974 7GCBC, it has wood spars and I replaced the engine years ago with the LYC O-320 B2B, I didn't realize at the time that only the metal spar 7GCBC's were approved to have the 160 HP O-320 B2B engine. Does anyone have any experience with this situation? I assume I will need to get a field approval, but I've heard it's not as easy as it used to be? Any advice or info would be greatly appreciated!

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Bob Turner

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#2
Yeah - shhh!

Check the type certificate for loopholes. There are some who insist that anything on the type certificate is legal for any aircraft. I view that with some skepticism - the PA11 is on the J3 type sheets, but I hold field approvals for wings, struts, and fuel tanks.

Sorry - I did not see your other thread. Maybe Bart can combine them.
 

AKpilot

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#3
I took the TCDS into the FSDO and asked for their interpretation of the language. They said they didn't know for sure, recommended I call the American Champion for clarification, I did and they confirmed it is required to have metal spars to install a 160 HP engine, however, it also gives you a gross weight increase. I'm wondering if there is someone out there that was able to get a field approval for the engine being installed on a wood spar airplane without the gross weight increase? It seems to me the FAA wouldn't have a problem with that being that it is less than a 10% increase in horsepower?
 

Bob Turner

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#4
You do not have to rely on others' opinions. You only have to rely on express statements.
If the TC says "160 horse is only allowed on factory aluminum spar aircraft" or worse, "only allowed on ser# x and up" then there is no room for opinion. If there is an ambiguity, interpret it in your favor.

People who write this stuff know how to make an express statement. If they don't do that, you have every right to interpret stuff in your favor.

Opinion.
 

Goodyear

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#5
I took the TCDS into the FSDO and asked for their interpretation of the language. They said they didn't know for sure, recommended I call the American Champion for clarification, I did and they confirmed it is required to have metal spars to install a 160 HP engine, however, it also gives you a gross weight increase. I'm wondering if there is someone out there that was able to get a field approval for the engine being installed on a wood spar airplane without the gross weight increase? It seems to me the FAA wouldn't have a problem with that being that it is less than a 10% increase in horsepower?
The factory metal wings give you a gross weight increase but not the Milman metal wings. You can probably buy a new plane for the cost of having factory metal wings shipped to you and installed.
 

AKpilot

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#7
Thanks for the advice and input. I decided to go with the field approval process. The FSDO was pretty helpful and the process was not as bad as I thought it would be. It’s done and approved.
 

Bob Turner

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#8
So do you suppose that service bulletin just backs up the TCDS? Or is ACA assuming that it can issue a service letter and it becomes approved data?
 

Bob Turner

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#9
I just quickly looked at the type certificate. Items 125 and 126 appear to allow the 160, installed per a service bulletin. It also references notes 13 and 15, which do not specify metal wings. So can a service bulletin become part of a type certificate? If so, can it only restrict, or can it expand what is legal?

By the way, Continental has a few early service bulletins that state, up at the top, that they are FAA/CAA approved. That is good enough for me.
 

Bartman

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#10
Thanks for the advice and input. I decided to go with the field approval process. The FSDO was pretty helpful and the process was not as bad as I thought it would be. It’s done and approved.
glad to hear it worked out for you! would you mind starting a new thread and outlining your project? details and photos that might help others to do what you've done would be very much appreciated!
 

Kmcaero

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#12
Thanks for the advice and input. I decided to go with the field approval process. The FSDO was pretty helpful and the process was not as bad as I thought it would be. It’s done and approved.
I am in the same boat as you were, wanting to increase to the 160 hp -B2B, I am in the process of rebuilding a 1970 7GCBC over the last few years. I am in Canada so will be dealing with Transport Canada on this. Could you give me some guidance on what you had to do for the FSDO and what paperwork was required? Maybe a copy of the final approval?. If I can show proof of recent FAA acceptance on this to our guys they will usually green stamp it also.