Porp RPM

[rayrey10]

Question: when flying an aircraft with propellers and you reduce the RPM to say, 2200 to 2500, do you leave it at that RPM setting all the through to landing? Or do you go back to full prop speed when making your descent?

 

[Volker Böhme]

Question: when flying an aircraft with propellers and you reduce the RPM to say, 2200 to 2500, do you leave it at that RPM setting all the through to landing? Or do you go back to full prop speed when making your descent?

Hi,

depends on the aircraft, but for landing, you'd want RPM to be higher than cruise/descent RPM to allow for higher drag of gear and flaps and to allow quicker acceleration on go-around. Some pilots/airlines/manufacturers advocate full high RPM on short final, but it might vary, depending on the type and possibly on the user as well.
The last cruise RPM setting usually works well for descent. Going to full high RPM at top of descent will probably be very hard on the engine - after all, you shift back to first gear the second you reach the freeway off ramp.

Best regards,
Volker

 

[Dynasaur]

When I used to fly single engine aircraft with constant speed props, the procedure I was taught was to reduce the throttle on downwind until the prop rpm dropped (it stopped constant speeding) then go to full fine prop pitch and just use the throttle after that. If you had to go-around on final you would need max. rpm to climb out again.
This was just for Cessnas, Piper Arrows etc.

 

[Sunny9850]

I leave the last cruise rpm as well until on downwind. Then as described by Dynasaur....unless I am forced to a Slam-Dunk approach by ATC.... in that case I might go full fine earlier in the descent.
This of course depends on the aircraft in question as well. My lovely Saratoga is of the gear-down-and welded variety...so not exactly a queen of aerodynamic sleekness so usually doesn't have too much trouble slowing down. When flying a retractable such as a Mooney or one of the plastic bodied fixed gear slicks (Cirrus, Corvalis) a bit more finesse might be needed to keep speed in check.

Since I have to pay for my IO-540 out of my own pocket I do make sure that all rpm changes are done smoothly and below redline. But I know a few hamfisted jockeys that seem to simply go by their checklist and when they get to the line that reads " prop full forward " that is what they do....no matter what and then you hear this screaming banshee on short final.

Stefan

 

[rayrey10]

Thanks for the info fellas! It knew that it made sense to increase prop RPM at least on final in case of a go-around but I wasn't sure for descent.

 

[Aztec]

rayrey, if you havn't already seen it, have a look here -

http://www.avweb.com/news/pelican/182146-1.html

There's not much this bloke doesn't know about operating piston engines. #'s 15, 16, 18 & 19 are of particular interest.

Az

 

[tgibson]

In the propliner era it appears it varied airline by airline. Some chief pilots thought one way, and some thought the other way...

 

[rayrey10]

Az - thanks for the link. Lots of info. A bit over my head since I am not a pilot but very interesting.


tgibson - thanks! I read that somewhere when I first "researched" the subject.