M20J glide ratio

[carusoam]

Definitely a feature…

For most Mooneys…

There will be an rpm that there isn’t enough oil pressure to pressurize the prop…

Often, the run-up will give a hint where that will happen…

Some people use a higher rpm for prop testing…..

 

I have never noticed any prop control issues, prior to pushing the prop in for landing….

Where the knob all the way in, puts the prop near or on the stops….

 

Oddity: Missiles and Rockets fail to Low RPM with their original props from the Twin C….

Experience: I lost the shaft seal behind the prop of the M20C… no pressure to the prop, blades on their stops… RPM can easily go past redline if the stops aren’t adjusted perfectly….

Best regards,

-a-

[Pinecone]

15 hours ago, carusoam said:

 

There will be an rpm that there isn’t enough oil pressure to pressurize the prop…

Often, the run-up will give a hint where that will happen…

On run up, the there more than enough oil pressure, but there is not enough power from the engine to hit the max RPM, so the prop is at the fine pitch stop.

During the run up at 1700 RPM, you are still  at the fine pitch stop, but pulling the prop control back requests a lower RPM than 1700, so the prop responds and the RPM falls.

 

[A64Pilot]

We don’t have variable pitch props, we have constant speed props.

[Pinecone]

A constant speed prop IS a variable pitch prop.

The difference is how the pitch is controlled.

 

[A64Pilot]

3 hours ago, Pinecone said:

A constant speed prop IS a variable pitch prop.

The difference is how the pitch is controlled.

 

Actually not, a variable pitch prop is adjustable but the pitch does not change unless the pilot adjusts it. Back in the day the variable pitch and two speed props were mainstream

Later constant speed props came out and as the name suggests they will automatically change pitch to maintain a set RPM, within limits of course.

Really very different things, you would be working hard trying to maintain max RPM on takeoff with a variable pitch prop, not that we dogfight, but that’s where the constant speed really made the difference, everything on our aircraft came from Military technology, even our common hardware.

I believe just two months prior to the Battle of Britain the Spitfires were modified with license built Hamilton Standard constant speed props, this allowed the pilots to not worry about engine RPM in either a steep climb or dive, the governor made sure the engine would stay at its HP peak always, that and the US made 100 Octane fuel almost certainly allowed the Brits to win. Between the two the Spit would climb hard and gained I think something like 15 or 20 kts speed, it was a huge difference, just looked it up, 25 mph at sea level and 34 at 10,000 ft, allowed higher boost of course

The German BF-109 at the time had variable pitch props which was a significant disadvantage, they were electric props and had a pitch indicator sort of like a clock face, but the German pilot had to essentially run a lower than max RPM to keep from inadvertently  over speeding the engine and of course had to constantly watch the tach.

 

[A64Pilot]

The 100 Octane fuel story for those that haven’t read it.

https://sofrep.com/news/filler-up-how-high-octane-gasoline-saved-untold-allied-pilots-during-wwii/

The Germans of course captured some but their engines couldn’t make enough boost to take advantage of it at altitude, so they used alcohol and water injection down low where they could run high boost and Nitrous oxide injection up high.

Germans mostly burned 89 Octane fuel in the war, they had some high octane, but not much, while Japan fought with 87 Octane, only the Allies with US fuel had 100 Octane.

Russians had everything from 70 to 100, as they got the majority of their Avgas from us, 60% I bet we supplied the 100.