Texas Skyways 240hp O-520-F-T/S STC SE09017SC

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Jon Wilder

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Jwylde
Hi all. Is anyone familiar with a Texas Skyways O-520-F-T/S 240hp engine built IAW STC SE09017SC? It's the engine on a 182Q that I rent from time to time. It seems odd to me that they'd build a bit larger engine for only a 10hp gain.

Also, the STC calls out a Horizon Instruments P1000 electronic tachometer to be installed with the engine "when installed in a Cessna 182 aircraft" (exact language under the "GENERAL" section of the STC Flight Manual Supplement). However, this aircraft has since had a Garmin G3X Touch with Garmin GEA 24 engine analyzer installed. Is this a legal substitute for the electronic tachometer called out in the STC? Or would the electronic tachometer called out in the STC have to be retained in order to maintain continued airworthiness under that STC?

Thanks in advance.
 
Last edited:
Jon Wilder said:
Hi all. Is anyone familiar with a Texas Skyways O-520-F-T/S 240hp engine built IAW STC SE09017SC? It's the engine on a 182Q that I rent from time to time. It seems odd to me that they'd build a bit larger engine for only a 10hp gain.

Also, the STC calls out a Horizon Instruments P1000 electronic tachometer to be installed with the engine "when installed in a Cessna 182 aircraft" (exact language under the "GENERAL" section of the STC Flight Manual Supplement). However, this aircraft has since had a Garmin G3X Touch with Garmin GEA 24 engine analyzer installed. Is this a legal substitute for the electronic tachometer called out in the STC? Or would the electronic tachometer called out in the STC have to be retained in order to maintain continued airworthiness under that STC?

Thanks in advance.
Click to expand...
Why not call Texas Skyways since they own the STC.
 
Jon Wilder said:
Is this a legal substitute for the electronic tachometer called out in the STC?
Click to expand...
In general terms, once an aircraft is altered per an STC it conforms to a "new" type design. After that design change, it is possible to alter the aircraft type design again, using the proper process, even if that alteration is with the items installed under an STC. So the "clock" resets after each aircraft alteration and the same rules apply. My bet is that if the Garmin 3X is installed correctly it meets the requirements for the engine STC. Usually listed on the STC document under the Limitations and Conditions section is the following statement: "Compatibility of this design change with previously approved modifications must be determined by the installer." Or something similar. If that makes sense.
 
So I did email Texas Skyways. They informed me that the "naked" powerplant is rated 280hp, and is stamped as such on the engine's data plate. The AFMS lists the bhp, or Braking Horsepower, which is what you get once you hang a prop on it, install the alternator, vacuum pump, etc. All of that stuff consumes some of that 280hp, leaving 240 bhp to play with.

They also informed me that the engine begins life as a Continental IO-520 300hp. They derate it by ditching the injection system for a carburetor. All of the mods are external. Nothing is done to the internals of the engine.

Which leads me to the next question.

The original engine was a O-470-U rated for 230bhp @ 2400 RPM. Going to the big bore engine gives 240bhp @ 2700 RPM. We have 10 more horsepower but at a higher RPM. So what did we really do here?
 
Jon Wilder said:
….The original engine was a O-470-U rated for 230bhp @ 2400 RPM. Going to the big bore engine gives 240bhp @ 2700 RPM. We have 10 more horsepower but at a higher RPM. So what did we really do here?
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You’re spinning the prop faster which means you’re moving more air so you’re doing something faster or heavier.

You may also be making more power at any given altitude relative to the stock engine.
 
The data tag is for the FAA. That’s what they did to get the STC approved. A carbureted 520 will make the same power as the injected version at the same RPM assuming same pistons. Pponks version makes a little less HP because the standard STC uses TSIO pistons with lower compression.
 
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