Why do some turboprops have throttle, prop, and condition levers while some have only throttle and condition levers? Also, does anybody have a dumbed down explanation of what exactly the condition levers do and how the prop levers control RPM? I imagine they control them differently than in a piston engine with a controllable pitch prop.
Turboprop engine controls
- Thread starter JordanD
- Start date
Here's a great online explanation.
Question #1 http://www.pilotoutlook.com/airplane_flying/turboprop_engines_types
Question #2 http://www.pilotoutlook.com/airplane_flying/reverse_thrust_and_beta_range_operations
Question #1 http://www.pilotoutlook.com/airplane_flying/turboprop_engines_types
Question #2 http://www.pilotoutlook.com/airplane_flying/reverse_thrust_and_beta_range_operations
SpiraMirabilis
Possible Subversive
Some turboprop engines, namely the PT6 and a few other types, have a setting for "high idle" and "low idle" that necessitate a seperate fuel condition lever where as other turboprops, like the Dash-8 have the "Fuel Cut-off" and "Idle" portions of the fuel condition lever combined into the lower end of the prop lever. That's to say at the very bottom detent of the prop is fuel cutoff, then one detent up feather, then the next detent is introduce fuel and minimum prop RPM and now you're at the stage where you can move the prop all the way forward without encountering another detent until you get to max prop RPM.
I suppose this functionality could be replaced with a "Low / High Idle" switch rather than having a whole seperate lever for it so it may not be the only reason involved... there might be some kind of cockpit design or trainability reason too.
Hacker15e
Who am I? Where are my pants?
In the King Air, at least, it has to do with the low/high idle concept, and the fact that the bottom end of the power lever has ground fine and reverse (leaving no room for the two idles and the fuel cutoff positions).
If they were all on the same lever, you'd have to go through reverse in order to shut the engine down...not exactly a great idea when shutting a motor down in flight.
The natural follow-on to the question for me is, "why are there prop controls (ground fine, reverse) at the bottom end of the power levers (instead of where logic would say they should be, on the prop levers)??"
Probably has to do with being able to select the Beta functions without moving your hands to a different set of levers during the landing....
If they were all on the same lever, you'd have to go through reverse in order to shut the engine down...not exactly a great idea when shutting a motor down in flight.
The natural follow-on to the question for me is, "why are there prop controls (ground fine, reverse) at the bottom end of the power levers (instead of where logic would say they should be, on the prop levers)??"
Probably has to do with being able to select the Beta functions without moving your hands to a different set of levers during the landing....
SpiraMirabilis
Possible Subversive
Well they usually put the reverse/beta on the power lever past a detent/trigger so you would just pull power back to the detent to go to idle power, then move to the next lever for fuel cut-off for engine shutdowns.
Hacker15e
Who am I? Where are my pants?
My point was just that it's funny to have prop functions at one end of the power lever (controlling fuel) instead of on the prop lever....and necessitating a third set of levers for additional fuel control functions. Just on prima facie value, it would seem more simple if the fuel/power controls were all on a single set of levers and the prop controls were all together on another set.
Ergonomically, of course, it makes more sense the way it is.
SpiraMirabilis
Possible Subversive
Well even with three power levers the power lever in the lower range still controls prop pitch and compressor % in order to accomplish beta and reverse.
PFGiardino
Well-Known Member
The RPM isn't in the prop lever governing range while on ground, so power lever has beta and reverse ranges that operate on a separate, lower RPM governor system. Remember that idle RPM is very high compared to a piston; without this separate ground governing function, torque would be too high even at idle RPM for a normal taxi speed. Makes sense to associate that ground governor with the power lever so that only one needs manipulation on the ground. I'm fairly sure the "Emergency Power Lever" in the Caravan bypasses the ground governor in case its failure hinders normal flight operation.
The prop lever is the flight range RPM governor, a lot like a piston; more expensive.
The condition lever limits power by limiting fuel flow-- just a high/low switch, gets left alone in flight.
The prop lever is the flight range RPM governor, a lot like a piston; more expensive.
The condition lever limits power by limiting fuel flow-- just a high/low switch, gets left alone in flight.
SteamyNicks
Well-Known Member
On zee dash, we have a Power lever, and a Condition Lever. The power levers have 2 areas where they control 2 different things. Above flight idle, the power lever works like ... a power lever! It controls a Manual Fuel Control (which really just increases or decreases fuel flow) and inputs to an Engine Control Unit (which meters fuel flow and controls automatic uptrim). Below flight idle you're in the Beta/Reverse range. Theres 2 things you can do below flight idle. the first detent is disc, where the props essentially go flatpitch, causing lots of drag. Below disc is reverse (self explanatory). You have to pull on a trigger to go below flight idle and into disc. If you pull this trigger in flight, it sounds a horribly un-ignorable horn, and if you were to pull the power lever below flight idle, the beta lockout system comes into play and prevents the prop from going to disc (and according to our ground school teachers, the wings from falling off).
Our condition levers have 3 actions. The normal range (which is above the start&feather detent) the props act like your standard props on a twin. towards the nose is higher rpm. In the start and feather range, the props go into feather, and this also allows fuel into the engines (which for a now t-prop guy, is weird to see an engine that is running... in feather) . I think of this like a prop rpm combo meal with a fuel on/off switch dessert. Below start and feather is fuel off, which turns the fuel off and allows for shutdown of the engines.
I hope that kinda makes sense!
Our condition levers have 3 actions. The normal range (which is above the start&feather detent) the props act like your standard props on a twin. towards the nose is higher rpm. In the start and feather range, the props go into feather, and this also allows fuel into the engines (which for a now t-prop guy, is weird to see an engine that is running... in feather) . I think of this like a prop rpm combo meal with a fuel on/off switch dessert. Below start and feather is fuel off, which turns the fuel off and allows for shutdown of the engines.
I hope that kinda makes sense!
Autothrust Blue
”…trusting ze process…”
And because the ground-fine and reverse portions would be logically (in terms of blade angle - low pitch, high RPM) placed at the top end of the prop levers, and you'd have to push forward to get reverse. An unsatisfactory situation.
On the TBM, we have the conventional condition lever (high idle for almost all phases of operation if memory serves), prop lever (with full low pitch-high RPM and full feather as limits), and power lever setup. The power lever has the normal flight range, the "taxi" range (which is roughly equivalent to ground fine for beta) and the reverse range. Chicks dig the beta and reverse ranges.
Boris Badenov
Fortis Leader
PT6s have three because they're like tricycles...for babies who can't use two. Or maybe one of the levers is to pivot the engine till it's facing forward.
Autothrust Blue
”…trusting ze process…”
Nah, it's the "sneak up on someone on the ramp (relative to a Garrett)" lever...the real reason they have three.
Hacker15e
Who am I? Where are my pants?
The T-6 has only one lever for it's PT-6.
Hacker15e
Who am I? Where are my pants?
Only prop RPM, since the prop shaft is not connected to the same shaft on which the N1 is spinning.
Gotcha, that's what I figured for the free turbines. I guess the Garretts are a little different?
Boris Badenov
Fortis Leader
That's because it's operated by guys who don't know that "it's" is a contraction of "it is", rather than an indication of possession.
The PC-12 and Meridian only had two levers and they both have a PT6. The PC12 had a power lever and a condition lever. The condition lever had Flight Idle, Ground Idle, and Cutoff/Feather. The Meridian's condition lever had "Run and Cutoff". Prop RPM on both was set to a fixed value (1700 on the PC12, 2000 on the Meridian).
Hacker15e
Who am I? Where are my pants?
That's because it's operated by guys who don't know that "it's" is a contraction of "it is", rather than an indication of possession.
Not a T-6 guy, so I wouldn't know.
Autothrust Blue
”…trusting ze process…”
The real T-6 has a mixture, prop lever, and throttle. And a carb heat control.