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Power setting for approach

Posted: Mon Sep 14, 2020 1:52 am
by JW Scud
Found it on another forum and sounds like it makes sense. Mind you, a lot of times I just do it by feel.

I fly dozens of aircraft makes and models with one set of numbers 25, 20, 15, 12. These are used for either manifold pressure on constant speed propeller craft or RPM on fixed pitch propeller aircraft. 25" or top of the green for cruise, 20" for entry into the airport traffic area (descent from cruising altitude or level at vectoring altitude, or 45 degree entry into downwind), 15" for approach descent (with initial flaps and gear extended), and 12" for short final with full flaps. If flying an aircraft with fixed pitch prop, ad two zeroes to each number for the appropriate RPM setting.

The resultant airspeeds will match up with the white arc (unless your aircraft has only one flap extension speed), with a suitable speed for stabilized approach, the 3 degree glide path/slope, and not excessive over-the-threshold speed with proper energy remaining for the flare to touch down just above stall speed.

This comes from 9000+ hours in all sorts of GA aircraft. It even works in twins. Give it a try before you comment. In most cases, the numbers work as is. The 15 may need adjusted one number or two up or down, but it is a good starting point.

Re: Power setting for approach

Posted: Mon Sep 14, 2020 3:45 am
by John Swallow
I'll file that away with all my other ROTs.* For my fixed pitch aircraft, they just might work...
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* Rules of Thumb

Re: Power setting for approach

Posted: Mon Sep 14, 2020 10:00 am
by Nark
That’s about what I do as it is. I’d have to agree.

Re: Power setting for approach

Posted: Mon Sep 14, 2020 2:52 pm
by Liquid_Charlie
Well this post got me thinking and I being a "looks about right" kind of guy my brain wanders back over what I did and I must say power settings were more a place on the dial than a number for me. I hated rules of thumb and preferred feedback my ass was feeling. I know flying approached on a jet power settings will give you the profile you are looking for but again rough set the thrust and tweak was more me. I guess it's all how you learn to fly. I have trained many pilots who are so anal about power settings it affects their flight duties and ability to keep the dirty side down. I see the source, flight schools and the one mould fits all thing.

I see the logic it what you do and yes power settings are important, I even marked the thrust lever position on the quadrant in case we lost all the gauges. A jet is so much easier to fly. Pitch first followed by thrust give an airspeed, rate of altitude change. Prop aircraft not so stable. The herc drove me crazy sometimes after coming off a jet. :o