Question for turbo prop pilots

[no1pilot2000]

What is torque as it relates to a turbo prop?

Thanks.

 

[Kaman]

Torque is a measurement of twist measured in foot pounds typically or a percentage...It is also from a physics point of view a measurement of "work". Chemical energy converted into heat and kinetic energy.

 

[kf4amu]

I don't think torque is work. You need motion for work.

 

[Flyin2low]

Torque is the amount of power usually expressed in %. Pratt / Whitney likes to use it.

 

[SpauldingSmails]

What is torque as it relates to a turbo prop?

Thanks.

Torque is a measure of force. In the case of a turboprop we are measuring the force which the engine exerts upon the shaft that drives the propeller, or prop gearbox.

Power is computed by multiplying the torque that an engine produces by its rotational speed at it's drive shaft.

In simple terms of operation, in most turboprops, torque is the primary indication that the pilot will use for setting power for take-off, climb, cruise, descent, approach and landing.

If you're familiar with a piston engine aircraft equipped with a constant speed prop - you set the manifold pressure with the throttle and then set the propeller speed to maintain a desired power setting.

Torque, although a completely different type of measurement, would be the analog of setting manifold pressure in a piston engine airplane with a constant speed propeller.

There are many variations of engine control schemes for turboprops with regard to what levers control what, many aircraft combine functions power and propeller control.

Most basic turboprop engines use three levers to control their function: power lever - used to set torque, prop lever - used to propeller speed, and a condition lever - used to set the idle speed of the engine and function as a fuel cut-off lever. The power levers also usually provide for a propeller reversal setting (beta) to help slow the aircraft on the ground, and the prop lever will allow for feathering of the propeller.

 

[pilotyip]

Torque ='s Shaft Horse Power. We had a gauge on the L-188, CV-580 and P-3 that measured the Horsepower out put of each engine, same engine a C-130 measured it in foot pounds. P-3's L-188's and CV-580 had one lever for each engine like a jet.

 

[SpauldingSmails]

Double posted - disregard.

 

[Golden Falcon]

torque is a force extracted from a rotating power source...a car engine in neutral has no load on it, so the engine is not supplying any torque...a propellor spinning in a Piper Cherokee in idle is demanding no, or very little torque from the engine...as the throttle is opened and the rpm increases, the propellor creates thrust, which in turn causes drag, and the engine has to work to turn the propellor...this "work" is torque...turboprobs tend to have two engine operating limitations...temperature...due to internal metallurgy/construction of the engine, and a torque limit due to strength of the reduction gearbox on a cold day most turboprops will reach the torque limit before the temp limit..higher density altitudes/ambient temperatures the temp limit may be reached first...

 

[livin'thesim]

Real pilots fly props - down in the weather, in non-radar areas, etc.

Jet pilots are just a bunch of coffee-sipping dandies. And yes, I fly a jet.

 

[wms]

Force- amount of energy needed to change the state of motion of an object.
Work=force x distance
Power= f • d divided by time
HP = force x speed divided by 550
Comparison of thrust is HP= thrust • velocity in kts divided by 325.
Torque is a value some manufacturers use to determine percentage of power produced.

 

[Pattern-Master]

Real pilots fly props - down in the weather, in non-radar areas, etc.

Jet pilots are just a bunch of coffee-sipping dandies. And yes, I fly a jet.

I'll be a dandy sipping my coffee at FL 450 in the smoth air above the weather. And yes, i have many hours in a king air 90 flying in all that dogs!t wx.

 

[RJLoser]

Don't NTS.

 

[zasca]

Miss my Dash.... Jets are boring and there are still bumps at 410. Check is nice tho

 

[CX880]

Real pilots fly props - down in the weather, in non-radar areas, etc.

Jet pilots are just a bunch of coffee-sipping dandies. And yes, I fly a jet.

That's the point, get to the top where the air is crisp. And you get more women if you fly a jet, it's a scientific fact.

 

[pilotyip]

That's the point, get to the top where the air is crisp. And you get more women if you fly a jet, it's a scientific fact.

jets are for kids, real men are T-Prop drivers, I bet my T-Prop P-3 will run away from any of your jets at S.L. , anyone got a jet with a Vne of 407 IAS?

 

[OPECJet]

jets are for kids, real men are T-Prop drivers, I bet my T-Prop P-3 will run away from any of your jets at S.L. , anyone got a jet with a Vne of 407 IAS?

Doesn't count if the wings twist off at 340.

 

[pilotyip]

Doesn't count if the wings twist off at 340.

Not in the ole days when the airframes only had a couple thousand hours on them. I saw 400 and it wasn't even max continuous power. I have only had a wing come off on takeoff. Never in flight

 

[Flyin2low]

I have only had a wing come off on takeoff. Never in flight

Now that is real torque.

 

[sstearns2]

Torque is not Power!

Torque (in ft*lbs) X RPM / 5252 = Horsepower. If you are running a constant power (fuel flow) and you pull the propeller rpm down the torque will go up, but the airplane performance will not change since you have not changed the horsepower.

Structural engineers care mainly about torque because that is what creates the forces on the gearboxes, shafts, etc. Performance engineers and Pilots care mainly about horsepower because that is what makes the airplane perform, but torque is important since that sets the structural limitations.

When someone states that their big V-8 powered car is fast because it has a lot of torque they are wrong. The car feels fast because the engine can make a lot of horsepower at low rpm. Torque is meaningless for performance. It is horsepower that moves the car, airplane, boat, etc.

Scott

 

[SpauldingSmails]

jets are for kids, real men are T-Prop drivers, I bet my T-Prop P-3 will run away from any of your jets at S.L. , anyone got a jet with a Vne of 407 IAS?

You own a P-3!? You fly around at sea level!?

I doubt anyone on this board owns a jet, and I've never seen a published Vne for a turbojet aircraft - merely Vmo/Mmo in accordance with FAR Part 25 which has significant structural load margins. I'd also venture to guess that if manufacturers did calculate and publish a Vne speed, many jet aircraft would have Vne speeds in excess of 400 knots.