Cherokee STC RPM question

ircphoenix

ircphoenix

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ircphoenix
For the Cherokee 140/160 engine STC, the book says that you can run at 2500 RPM all day long... but not in excess of 2500 RPM for longer than 5 minutes due to the FAA Part 36 noise rules.

So... my question is... what the hell? The RPM limitation is noise abatement thing? At 10,500 feet what difference is an additional 1,000-1,500 RPM going to make at the ground for noise? The restriction isn't in place to protect the engine?

The power charts show up to 2600 RPM... but limited to 2500 RPM? I'm so confused.
 
I thought the recommended rpm for cruise ,on the Cherokees was 2450 rpm
 
ircphoenix said:
For the Cherokee 140/160 engine STC, the book says that you can run at 2500 RPM all day long... but not in excess of 2500 RPM for longer than 5 minutes due to the FAA Part 36 noise rules.
Click to expand...

That's a new one to me. Can you post a copy of the STC or other documentation that mentions the 2500 RPM max??

ircphoenix said:
I'm so confused.
Click to expand...

Yes - so am I.
 
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It looks like somewhere between 2500 and 2700 is an RPM that is ok for continuous operation without stressing the engine. Whether Lycoming will give it up, I doubt it.
 
ircphoenix said:
Yeah... I'm just confused about the restriction due to part 36. Like... Really?
Click to expand...

Did you look up 14 CFR part 36? It appears this was a requirement imposed on the STC holder at the time of its issuance so it looks like there is a 2500 rpm max continuous limitation other than for takeoff.

Now, would it fly ok at 2600 rpm in cruise? Probably, but you would not be operating within the limitations set forth by the STC.
 
I'm just confused about the noise limitation itself. So it isn't a limitation on the performance of the engine. It's a noise limitation. But ... for the people on the ground or in the air? And why is 5 minutes okay but 10 isn't as far as noise is concerned. I would think the limitations would be in relation to the ground, not the people in the plane... but who knows.

I like to know why. I'm finding that's a pretty futile effort when it comes to many FAA regs.
 
It's an environmental rule (noise limiting).....and has no bearing on the performance of the engine. Part 36 was added to the FAA rule set at the request of the EPA.....:mad2:

Ain't the EPA wonderful?:popcorn::sigh:
 
Last edited:
ircphoenix said:
For the Cherokee 140/160 engine STC, the book says that you can run at 2500 RPM all day long... but not in excess of 2500 RPM for longer than 5 minutes due to the FAA Part 36 noise rules.

So... my question is... what the hell? The RPM limitation is noise abatement thing? At 10,500 feet what difference is an additional 1,000-1,500 RPM going to make at the ground for noise? The restriction isn't in place to protect the engine?

The power charts show up to 2600 RPM... but limited to 2500 RPM? I'm so confused.
Click to expand...

Can it make 2,600 RPM at 10,5?
 
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