Trying to understand Prop Feathering, Constant speed props etc

[N1G 88]

Hi,This is my first attempt to understand feathering and constant speed props. I just bought the jetprop and really am trying to understand it's operation and theory behind this type of technology. How to fly it, what to do and what not to do. It really has me scratching my head. It really bothers me to try and fly something and pretend I understand it's operation. Can anyone point me to an article or series of articles that will help me understand how it works and how to use it.RegardsBob

[ryanbatc 12,770]

I hear ya... ever since the turbine Duke I've been trying to learn more about the engine itself.What I've gathered so far is most are fairly laggy in terms up power increase and decrease. Generally put the engine stuff in the green and you're ok. When climbing, reduce throttle, then reduce rpm to set cruise power.Here's a link that might help clarify:http://www.pilotoutlook.com/airplane_flying/turboprop_engines_types

[N1G 88]

I hear ya... ever since the turbine Duke I've been trying to learn more about the engine itself.What I've gathered so far is most are fairly laggy in terms up power increase and decrease. Generally put the engine stuff in the green and you're ok. When climbing, reduce throttle, then reduce rpm to set cruise power.Here's a link that might help clarify:http://www.pilotoutl...p_engines_types

thanks Ryan, I will take a look. I have a basic understanding but having a solid understanding will allow you to make the right decision in case of trouble. I remember reading about a guy who crashed because of not completely understanding of the physics and operational configurations and why. Apparently he was on approach with a mild descent. Blade pitch angle was reduced along with power. What happened was a plane pulled out onto the runway and he needed to pull up and out but the RPM's were way to low and he did not have enough time to correct. He ended up leveling a couple of small hangers, himself and all 4 passengers were killed. So what the experts were saying was that he should have kept the RPM's high on approach just in case. So with this in mind, it is more than just knowing what each lever does, it is this understanding what not to do aside from keeping things in the green I guess. So I really need to do some reading.Bob Edited January 12, 2012 by N1G

[ryanbatc 12,770]

Understood. From what I've read, when on final you treat every approach like you're going to go around. Sooo... props high rpm, oil cooler doors open (they are closed during descent to contain the warm air), fuel pumps on, fuel fullest tank, flaps lnd and gear down of course. The condition lever is apparently used more on the ground for taxiing but I'm not 100% sure one when to use the different settings in flight.

[Tom Wright 438]

It's actually pretty simple. In addition to the throttles (which control the power, or torque delivered by the engine) you also have the Prop levers, which control the speed (RPM) of the propeller by altering the pitch of the blades. In most aircraft, you take off and land with the propellers fully fine (full RPM, or levers fully forward). This gives the props the biggest 'bite' and thus more power, but also makes them noisier. During climbout, its standard procedure at thrust reduction altitude to reduce power, and reduce prop RPM. Note it must be in that order - you always reduce the throttles first before reducing prop RPM, otherwise you can overboost and cause damage to the engine. When you reach cruise, you set cruise power on the throttles and bring the props back a little further. In the manual for the aircraft there is usually a table which contains the cruise power settings and prop settings for particular altitudes. The props usually then stay in that cruise position until somewhere on the approach when they are moved back to fully fine for landing.Feathering a propeller is usually done after an engine failure to stop the propeller spinning (windmilling) in the wind (causing drag). The blades of a feathered prop are angled flat so they present the least obstruction to passing air.

Edited January 12, 2012 by twright

[N1G 88]

Hi Guys, thanks for the answers. So what exactly then is a constant speed prop? If one can control the RPM by changing pitch manually, then are there systems which control the rpm automatically?The learning process sometimes requires stupid questions I guess.Bob

[Tom Wright 438]

So what exactly then is a constant speed prop? If one can control the RPM by changing pitch manually, then are there systems which control the rpm automatically?

Constant speed prop means just that - it turns at a constant speed, independent of the engine speed.Compared with a fixed pitch prop like in the simple Cessna 172, where increasing the throttle also increases the RPM of the prop. With a constant speed prop, you set the desired prop RPM using the prop lever, and this will remain constant regardless of throttle position / engine speed. There is an automatic process which adjusts the pitch of the blades to maintain the prop rpm as a response to change in engine speed. Edited January 12, 2012 by twright

[N1G 88]

Constant speed prop means just that - it turns at a constant speed, independent of the engine speed.Compared with a fixed pitch prop like in the simple Cessna 172, where increasing the throttle also increases the RPM of the prop. With a constant speed prop, you set the desired prop RPM using the prop lever, and this will remain constant regardless of throttle position / engine speed. There is an automatic process which adjusts the pitch of the blades to maintain the prop rpm as a response to change in engine speed.

So when using the prop lever, you are actually changing the pitch of the blades which directly affects rpm's, is this correct? By increasing or decreasing throttle, blade pitch angle is increased and decreased proportionally to maintain prop rpm. I don't think I have this correct because if you manually can change the pitch with the prop lever then the throttle is also changing the pitch does not seem logical. sorry for being so dense here, but I am really stuck.Bob

[ryanbatc 12,770]

With the prop lever you are correct, the pitch (angle) of the blades change. With throttle lever, you're adding combustion (I guess in a simple term), and it's spinning the shaft, where the prop is connected. IE with the power lever (throttle) you are providing an increase or decrease of thrust. However the power lever setting DOES NOT change the pitch of the props... the prop lever does that.

Edited January 12, 2012 by ryanbatcund

[RudiJG1 172]

Watch this video, which is a great explanation of prop types:

And read the accumsim handbook for the Spitfire or the P-40; they include good info on props as well: http://www.a2asimulations.com/store/index.php?main_page=product_info&cPath=9&products_id=47Scroll to bottom of page and click on the accumsim manual to download.

[N1G 88]

Watch this video, which is a great explanation of prop types:

And read the accumsim handbook for the Spitfire or the P-40; they include good info on props as well: http://www.a2asimula...&products_id=47Scroll to bottom of page and click on the accumsim manual to download.

Hey thanks a bunch. I will do that.RegardsBob

With the prop lever you are correct, the pitch (angle) of the blades change. With throttle lever, you're adding combustion (I guess in a simple term), and it's spinning the shaft, where the prop is connected. IE with the power lever (throttle) you are providing an increase or decrease of thrust. However the power lever setting DOES NOT change the pitch of the props... the prop lever does that.

Well I thought I had it until now.Twright made this comment above "There is an automatic process which adjusts the pitch of the blades to maintain the prop rpm as a response to change in engine speed."Anyway, I am not sure now which is correct. I will keep reading.Bob

[ryanbatc 12,770]

You're right. Now I'm confused lol!

[Kimo 14]

Well I thought I had it until now.Twright made this comment above "There is an automatic process which adjusts the pitch of the blades to maintain the prop rpm as a response to change in engine speed."

Correct you select prop rpm with the prop lever. If you add power by increasing throttle the blade angle will increase too hold the rpm. Edited January 12, 2012 by Kimo

[ryanbatc 12,770]

I was wrong thanks for clarifying!

[NoahBryant 26]

Part of the reason I had trouble learning this was that in most FS planes, there's no penalty for just pushing everything to the max, but after the J41 and Turbine Duke I have a much better grasp of it.