STC required?

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zed
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STC required?

Post by zed »

Just wondering...

If an aircraft for example has a standard fuel cell (for example Cessna 172N), but for that model/year Cessna offered an optional higher capacity fuel option (eg 1979, it offered a 66 gallon capacity).

Will it generally require a STC at this time to move from the standard cell to Long Range fuel cell? Not talking about going from bladder to wet wing. Or is it reasonably straightforward, from a paper perspective, to make the change?
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CID
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Re: STC required?

Post by CID »

Your first step is to see if Cessna has a service bulletin to embody that modification. If they don't then you pretty much need to go the STC route and that might not be easy.

Cessna might have made specific changes to the structure or fuel delivery system to accommodate the extra fuel capacity. An STC would need to consider all aspects of the modification without the benefit of Cessna's engineering.
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System Message
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Re: STC required?

Post by System Message »

You do not STC something that is on the type certificate.
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iflyforpie
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Re: STC required?

Post by iflyforpie »

You don't need an STC to have something that is already incorporated in the type design, but you need to incorporate everything that is in the type design when installing it, and it might not be very easy to find that data. The first person who says 'just use the IPC' gets 50 lashes with a wet noodle! :D

Due to the huge amount of modification required, probably the only practical way to do it would be to find a set of wings with LR tanks installed and perform the necessary maintenance required to install them (installing control cables, controls, flap motor, testing fuel tanks, vents, and sending units, wiring if it has been damaged or removed, probably a zillion other small details). Still not an easy undertaking.

I would imagine a ship set of good wings with LR tanks commands a premium over standard tanks.

This is probably why there are lots of STCs for LR tanks out there, like Flint Tips for the 172.

http://www.flintaero.com/Cessna_150-205.htm
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Big Pistons Forever
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Re: STC required?

Post by Big Pistons Forever »

I believe there is an STC that adds the L shaped extensions to the standard 38 gal system tanks to make them the same as the 49 gal factory long range tank. As I understand it you get a appropriately approved shop to weld on the extension and then do the necessary wing sheet metal work to fit it. I have no idea who has the STC but you could try talking to the cessna type club.
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zed
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Re: STC required?

Post by zed »

Thanks. My take away: possible, but not straight forward or necessarily easy/cheap.
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CID
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Re: STC required?

Post by CID »

A couple of people stated that you don't STC something on the type certificate. That is true. If you can get a copy of the installation data and it's eligible for installation on your specific serial number.

But (as I stated) if your serial number isn't covered, you can STC it using the installation data but you'll have to come up with engineering data.

It's a fairly common myth that if you can make it look like the IPC you can install it. Not true. Systems that are approved under the type certificate may have specific additional requirements to accommodate the modification. That's why the first place to go is the manufacturer and see if a service bulletin is available for post production installation. If not.....STC like I said.
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