Engine Modification

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Jon Wilder

Pre-takeoff checklist
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Jwylde
Hi all.

Let's say you're researching an aircraft's engine logbook (engine is a Lycoming O-320-E2D) and you see the following language in the most recent overhaul entry -

"Installed overhauled Nickel Carbide cylinders with new high compression pistons..."

No mention of any STC that approves the installation of said high compression pistons.

Would this be legal? AFAIK, using the RAM 160 STC as an example, an approval letter is needed from the STC holder authorizing the modification of a specific engine IAW the STC, and an approval letter from the STC holder authorizing the installation of that engine on a specific aircraft. Yet nothing of the sort is mentioned in the overhaul entry, nor is any langauge alluding to "IAW STC blah blah blah".

Thanks in advance.
 
What type pf airworthiness certificate does the plane have?
 
Assuming this is a TCd engine, more context may be needed. There are methods some use to do things like this via converting the engine to a different model. But converting the engine to a different model may make it ineligible to be on the airframe without further approval.

Here’s an example of Continental’s guidance on the subject. Lycoming had a similar bulletin.

 
Jon Wilder said:
"Installed overhauled Nickel Carbide cylinders with new high compression pistons..."

No mention of any STC that approves the installation of said high compression pistons.
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This could merely be a repair and the piston upgrade was done previously under a different entry. Technically, there is no requirement to reference the STC again once the aircraft has been altered. However, without more info hard to make any other determination.

As to the piston upgrade, that would also depend on when it was performed as back before the early 2000s 337/STC fiasco some forward thinking shops actually upgraded O-320s from 150 to 160hp as a minor alteration. As I vaguely recall the FAA bought off on it. No STC used or 337 filled out. So there was no issue with the airframe side as indicated above. However, today, if someone were to check the conformity of your engine like you're doing now, it would get flagged and require additional documentation even if done as a minor pre-2000s fiasco times.
 
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O320 150 to 160 horse conversion runs afoul with crankshaft corrosion AD in most cases.
 
mondtster said:
Assuming this is a TCd engine, more context may be needed. There are methods some use to do things like this via converting the engine to a different model. But converting the engine to a different model may make it ineligible to be on the airframe without further approval.

Here’s an example of Continental’s guidance on the subject. Lycoming had a similar bulletin.

Click to expand...
Yes it is a TC'd engine.

Lycoming Service Instruction 1304J states that the serial number must be suffixed by the letter "C" when the basic model has been altered or converted to another model designation. This indicates a change from its original manufacture. AFAIK, this, too, requires a logbook entry.
 
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Jon Wilder said:
Yes it is a TC'd engine.

Lycoming Service Instruction 1304J states that the serial number must be suffixed by the letter "C" when the basic model has been altered or converted to another model designation. This indicates a change from its original manufacture. AFAIK, this, too, requires a logbook entry.
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Correct. So you need to look at the data plate and see if it has the C suffix and if the logbook has any documentation concerning a conversion, and what it was converted to.

If it is a conversion, then you need to figure out if it is an approved engine on the airframe, either via TC, STC, or field approval.

At a minimum, I personally know of several Super Cubs that had an engine conversion this way and an STC to fit it to the airframe.
 
bnt83 said:
O320 150 to 160 horse conversion runs afoul with crankshaft corrosion AD in most cases.
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i wouldn't say it runs afoul, it just means that when the upgrade is done legally, then the AD applies and it must then be complied with at that time.
 
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