Less Rpm=more Lift

[Outwest]

Oil pressure inside the engine is how every turbine helicopter measures torque.

 

It never ceases to amaze me how people make these sort of statements. AGAIN. absolutely false!!!

 

I will tell you, for a fact, the S61 torque system (and probably the S64) has absloutely no connection to the engine oil system what so ever!!!

 

The torque indication is derieved by the action of the input gear inside the front section of the main gear box having bevel cut gear teeth acting on the next gear in the chain. The more torque required to turn this gear the more this gear moves away from its mate, this moves a corresponding piston which is supplied oil from a torque meter pump on the transmission.

 

This is then converted to electrical value (AC) and is read by the torque gages.

 

 

[arctic_front]

Artic front you are wrong on the tq oil thing. In the 412 the tq reading come from sensor located at the bottom of the transmission extending up into the bottom of the mast which measures tq or the mechanical twisting force applied to the main rotor. With the 412, tq measuring has nothing to do with oil which is significantly different from 212 and early 412 models,it stictly mechanical and electrical.

 

 

I'll take that as being correct, as I have no experience with a 412. I'm guess that is a feature fairly unique however, as I think the 'typical' method is still engine oil pressure. Maybe the newer machines, akam AB139, 119 B4, EC145 ect have moved away from the old methods. I'm not at liberty to say. Until recently things have been pretty similar.

[arctic_front]

I stand corrected

 

[sirlandsalot]

well.......oooooooookay then, thanks y'all!

 

 

 

 

 

 

 

 

 

[splitpin]

It always amazes me how little people know about the most basic things in our industry. You guys don't even know what torque is!! Jeez!!

Best definition--

You are standing at the toilet with a monster woody---

Press down hard on said woody in order to hit bowl with resultant stream---

You will notice that your heels are lifted from the floor---

THAT'S TORQUE!!

[skullcap]

It always amazes me how little people know about the most basic things in our industry. You guys don't even know what torque is!! Jeez!!

Best definition--

You are standing at the toilet with a monster woody---

Press down hard on said woody in order to hit bowl with resultant stream---

You will notice that your heels are lifted from the floor---

THAT'S TORQUE!!

 

 

And you call yourself an engineer, that is an obvious transient overtorque, max continuous torque is when it takes one hand to push it down, max takeoff torque is when it two hands, max transient torque is two hands with the feet coming off the ground,,,,maybe you are old and are taking too much viagra and are forgetting the limits.

[splitpin]

And you call yourself an engineer, that is an obvious transient overtorque, max continuous torque is when it takes one hand to push it down, max takeoff torque is when it two hands, max transient torque is two hands with the feet coming off the ground,,,,maybe you are old and are taking too much viagra and are forgetting the limits.

 

You just made my day Skully!! Thanks!!

 

[Freefall]

Here's the answer to your question.

 

When you beep down the rotor, you are also slowing the engine. The torque pressure is a derivative of engine oil pressure so less oil pressure into the torquemeter piston, the less oil pressure coming out and to the gauge=more room on the gauge. Most engines will maintain a set oil pressure with minor fluctuations of engine speed, but the older ships probably didn't maintain as well. Therefore, as long as your oil pressure stays the same, you're not going to get any more "torque" by beeping it down, all you are doing is slowing the rotor and putting more stresses on the aircraft. the "beep" switch is there to provide you with an adjustment to compensate for temperature and pressure changes(ambiant) so that you can keep it at 100%. Read the Flight Manual and know your droop limits instead of chasing it around all the time.

 

Leave it at 100% and if you can't get off the ground you are doing something wrong. Get a more powerful machine or do 2 trips. You look like an *** when you wreck an overloaded aircraft, not to mention the resultant serious injury or death.

 

Hope this explains it well enough

 

I

 

 

The torque is measured off the compressor not the N2, which stays constant. Beeping it down will not decrease the torque. The N2 becomes harder to turn because of the increased drag in the blades with a higher AOA because you have to add collective to compensate for the drop in RPM. The fuel control has to add more fuel to compensate for the added drag and that causes the compressor to speed up which INCREASES the torque reading on the guage.

 

If your torque guage fails, how do you know how much torque you are pulling? N1

 

Why is the 204/205 with symetrical blades beep down theory so widely preached? I don't know there has to be something behind it I would think for so many people to believe it.

 

Maybe the old blades were so inneficient, that when you were light, and there is a low angle of attack on the blades, the blades actually needed a bit more angle of attack before they worked efficiently.

[Torque Split]

The torque is measured off the compressor not the N2, which stays constant. Beeping it down will not decrease the torque. The N2 becomes harder to turn because of the increased drag in the blades with a higher AOA because you have to add collective to compensate for the drop in RPM. The fuel control has to add more fuel to compensate for the added drag and that causes the compressor to speed up which INCREASES the torque reading on the guage.

 

If your torque guage fails, how do you know how much torque you are pulling? N1

 

Why is the 204/205 with symetrical blades beep down theory so widely preached? I don't know there has to be something behind it I would think for so many people to believe it.

 

Maybe the old blades were so inneficient, that when you were light, and there is a low angle of attack on the blades, the blades actually needed a bit more angle of attack before they worked efficiently.

 

Outwest is somewhat correct in his response to how torque is measured.

 

The torque on a 250 is measured off the helical torquemeter gearshaft which supplys power to the power output gear and is driven by the power turbine shaft. It basically is measuring the difference in the power supplied to what is being used.

It is definitely not measured off the Compressor and the N1 is the least constant rpm in the whole turbine.

 

The following pertains to the Allison 250 Series

The torque is measured when two helical gears in the accesory gearbox produce an axial thrust directly proportional to the torque transmitted through the helical gears. The gears kinda walk over each other as more torque is produced. This compresses an amount of engine oil in a chamber and it is from this pressure that the torque pressure is read. Engine oil does supply the oil for this system to work. Remember with the Astar that when the oil pressure is low you also refer to the torque gauge. If this reads zero its actually giving you an indication that there is no engine oil pressure or oil left to use for the torque system. Definitely a serious problem.

So engine oil pressure does not control the torque but only supplys the source of oil that the torquemeter system uses. The old 206's had a wetline direct to the cockit torque guage and the later ones convert the torque pressure to an electrical signal that is sent forward to the guage.

 

There are different systems to measure torque. The gazelle actually measured the twist in the output shaft and the lama the blade pitch angle which in turn new how much power was required to maintain this angle through temp and altitude.

So it would help if you included the type that you are talking about

 

The following is not directed at anyone in particular.

 

With all the lowtimers, inexperienced people and those with a thirst for real knowledge that read these posts, it is imperative that you do some reasearch and know what you are talking about before posting.

[Freefall]

Hmm interesting.

 

I just assumed since the torque so closely related the N1 they had to come from the same part of the engine.