Constant Speed Props

[rookiepilot]

16 inches and 2700 RPM…weird.

The 16 inches was at full throttle because of the altitude. That combination will give you more power then selecting a lower RPM but is very hard on the engine.

How high was he? 16 inches….

[digits_]

As a general comment high RPM with very low MP should be avoided where possible. The problem is that the cylinder pressure is low and there is danger of the piston rings not being held firmly against the cylinder walls and scuffing the cylinder liners. A fellow I knew badly damaged his cylinders flying at cruise at high altitudes in a normally aspirated engine. He was running 16 inches and 2700 Rpm.

Was he still within POH limits during that flight?

[NotDirty!]

16 inches and 2700 RPM…weird.

The 16 inches was at full throttle because of the altitude. That combination will give you more power then selecting a lower RPM but is very hard on the engine.

How high was he? 16 inches….

I would guess significantly higher than that! Tens of thousands of inches, likely!

[rookiepilot]

The 16 inches was at full throttle because of the altitude. That combination will give you more power then selecting a lower RPM but is very hard on the engine.

How high was he? 16 inches….

I would guess significantly higher than that! Tens of thousands of inches, likely!

[Big Pistons Forever]

As a general comment high RPM with very low MP should be avoided where possible. The problem is that the cylinder pressure is low and there is danger of the piston rings not being held firmly against the cylinder walls and scuffing the cylinder liners. A fellow I knew badly damaged his cylinders flying at cruise at high altitudes in a normally aspirated engine. He was running 16 inches and 2700 Rpm.

Was he still within POH limits during that flight?

Good question. He was regularly flying a V35 Bonanza at 15000 or 16000ft and the POH that I looked at doesn't expressly prohibit that MP and RPM combination but the cruise power charts only give cruise power settings for 2100, 2300, and 2500 RPM.

[rookiepilot]

As a general comment high RPM with very low MP should be avoided where possible. The problem is that the cylinder pressure is low and there is danger of the piston rings not being held firmly against the cylinder walls and scuffing the cylinder liners. A fellow I knew badly damaged his cylinders flying at cruise at high altitudes in a normally aspirated engine. He was running 16 inches and 2700 Rpm.

Was he still within POH limits during that flight?

Good question. He was regularly flying a V35 Bonanza at 15000 or 16000ft and the POH that I looked at doesn't expressly prohibit that MP and RPM combination but the cruise power charts only give cruise power settings for 2100, 2300, and 2500 RPM.

Mmmmm.

https://www.aopa.org/go-fly/aircraft-an ... ft-bonanza

[PilotDAR]

Thread drift, but it's probably time anyway....

While doing mogas testing in a normally aspirated, carburetted O-520, in a 185, the objective was to find the absolute ceiling. I got it to 21,050 feet, but could not hold it there. I held it at 20,800 feet, stall horn tweeting, 75 MIAS, 12 in MP (full power) and 2500 RPM (full fine). Interesting, but I did not stay long.

Yes, when I had dumped the jumpers from the 185, I pulled some G most of the way the way down (no G meter though, so I was careful), but still not 3000 FPM descent. Another pilot eventually wrinkled the wings doing something dumb trying to get down quick, and they wrote the plane off (It was not a cream puff). Cessnas are tough though....

[pelmet]

Thread drift, but it's probably time anyway....

Yes, when I had dumped the jumpers from the 185, I pulled some G most of the way the way down (no G meter though, so I was careful), but still not 3000 FPM descent. Another pilot eventually wrinkled the wings doing something dumb trying to get down quick, and they wrote the plane off (It was not a cream puff). Cessnas are tough though....

Interesting. Reminds me of when I was skydiving. One of the weaker pilots went into a cloud and lost control but recovered. I showed up later to jump and did so....out of that aircraft. Plane had looked OK. Turned out that there was major damage at the struts. Perhaps exaggerated but I was told the bolts were nearly pulled out.

[PilotDAR]

The wing damaged jump 185 to which I refer was in the Ottawa area, probably close to thirty years ago. I heard of the event through the jump organization I knew, and it was verified later, as a friend of mine bought the damaged wings and had them completely rebuilt for his amateur built 185 project.