Now i have a question, if engine is weak/ under power, what we expect to see on Torque Indicator inside cabin, a higher or lower then normal Torque?
Another indication for a weak engine is a higher indicated EGT/ MGT. But what about Indicated Torque. Does it have any significance to ascertain condition (and health) of engine?
But i have a confusion in mind, that, before flight, we check Performance Planning Charts from Dash Ten, and find, max allowable Torque.
This Torque is not allowed to be exceeded. Is it a Engine limitation.
If your engine is weak or under powered, it’s working inefficiently. Therefore, the engine must work harder to support its normal workload. Looking at the relationships, you’ll see higher than normal Ng, N1, TOT, TIT, EGT, and Fuel flow readings etc. for the same torque value. Example, you’re normally hovering OGE at your home base @ 75ºF, full fuel @ 39 PSI torque and 608ºC EGT. Over time you’re at the same 39 PSI torque; however, your EGT is how 620ºC, along with a near max Ng.
It’s a common problem, low power with high EGT. It is most commonly related to compressor damage, dirty compressor, bleed valve failing to close fully, In the case of the T53, a Bleed band, which is controlled by a slide valve on the fuel control with reference to compressor discharge (P3), and ambient pressure (PA). Additional problems include, excessive air leaks, anti-icing or heat control valve leaks. Normally higher engine inlet temperatures during the summer also amplify the situation.
As stated in Gomer Pilot’s post above, the best way to troubleshoot power issues is to start with an evaluation of the engine by accomplishing a power check.
Torque available values determined are not limits. Any torque which can be achieved, without exceeding engine, transmission, or other limits, may be used. As shown in the chart below torque is limited by the transmission/drivetrain, which is most often the case.
A few words on torque and engine power to ease the confusion. If a force is being applied to cause rotational movement, Work is being accomplished to cause that motion and a torque is being applied. Therefore, in accordance to the physics, there’s a relationship between Work, Power, and Torque.
Power is the rate of doing Work. Work = D (distance moved) x F (force applied). By definition, Work is calculated as a vector force, exerted in a straight line. But engines (as well as nuts and bolts when they are tightened or loosened) rotate around an axis.
The expression of this rotational or twisting force around an axis is called torque, which is measured in units of force times distance from the axis of rotation. If you have a 1-foot-long wrench and you exert a force of 10 pounds on the end of it then you apply a torque of 10 Foot-pounds (10 ft.-lbs.). If the wrench were 2 feet long, the same force would apply a torque of 20 ft.-lbs. When an engine is said to make 200 ft.-lbs. of torque, it means that 200 pounds of force on a 1-foot lever is needed to stop its motion. This is the relationship between torque and engine power, even though torque is most often referred to only as a transmission or drivetrain limit.
Edited by iChris, 17 July 2016 - 01:47.