Rupurt

"So start it already. Torque is generally measured in mass over distance, correct? I'm less than sure about horsepower- is there a time factor involved? "
Yeah power is work over time (I think). Torque is rotational force.

William Robison

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[b]Jett:

You are still missing one important point. All the examples I and many others have given are from a steady state; trimmed level cruise, at less than Vne and below the airplanes service ceiling.

Now, not using autothrust or the autopilot. In this level stable cruise, let's say you're in a PA-18 at 85 knots, 4000 AGL, 65% power. Crank in a little up trim. Yes, you will pitch up and the plane will start a climb. BUT, it will come back to level flight at a lower airspeed. Still 65% power. Or crank in a little down. The reverse will happen - level flight at a higher airspeed.

Back in a stable cruise, we'll play with the power. Go from 65% to 75%. Again, the airspeed will increase, and all by itself the plane will start climbing, again reach a stable cruise at a higher altitude. The reverse is also true. Cut power to 50%, the airspeed will drop, the plane will nose down, and at a lower altitude the plane will reach a stable state of flight.

Or as was posted earlier - the instructor chopped the power and told the student to climb to 6000 feet.

If you lose power in any airplane sir, not only can you not climb, you are going down. Care to make a guess about what controls your airspeed in the descent? Pitch, sir. In other words the elevator is controlling the airspeed.

THe heavies, autopilot and autothrust notwithstanding, work exactly the same way. It is just more obvious when you're driving a light plane.

This relationship can be hard to understand, it took me a while to get it too. But I got it more than 40 years ago. As you get more time I hope you come to understand this, Without this understanding of a basic characteristic you'll find it's a lot easier for a simple mistake to escalate into a major error which can kill you, and anyone riding along.

In the meantime sir, I suggest you stop posting in this thread. Perhaps, if you go back and reread the postings you will understand though.

Flycfii:

Go back to the thread I linked earlier. I have a note there about p-factor too.

Bill.

MJD

My Feedback: (1)

Really? Start it? Start what?...

Torque is a force. One foot pound is the torque that will exert one pound force with a moment arm of one foot. There is no rate involved, only force. Horsepower is torque times rpm. Turning a certain propeller at a certain rpm requires a specific amount of torque but [and IMHO here's where the confusion, debates and myths originate] to generate that amount of torque at that rpm requires a certain amount of horsepower. Horsepower comes from a rate of fuel flow, plus efficiency and other factors, but ultimately from a rate of fuel flow.

You can cause a 40% scale whatever to rise 100 feet with a Cox .020, if you gear it down to the point where it can drive a pulley and cord to lift the aircraft at a speed that equals the horsepower input. You can do it faster with a 100cc engine, because the rate at which it does work is higher. And for the same reason no matter how much you gear down to .020, it will never fly the aircraft because it does not have enough horsepower to move the aircraft fast enough. The rate it does work is not sufficient, it cannot flow fuel fast enough.

The debates, myths and cute axioms regrading torque I think all originate in the art, science and voodoo of propeller selection and of running engines in certain areas of their horsepower curves. [No, their torque curves!! Oh wait, horsepower divided by rpm IS torque..].

That's it, done, finito, back to work, time for a sandwich anyway. Mmmm peppercorn salami and cheddar on rye.

Rv7garage

My Feedback: (10)

MJD-

Actually, fuel is not a factor in HP ratings. Here's the equation:

Horsepower is defined as work done over time. The exact definition of one horsepower is 33,000 lb.ft./minute. Put another way, if you were to lift 33,000 pounds one foot over a period of one minute, you would have been working at the rate of one horsepower. In this case, you'd have expended one horsepower-minute of energy.

So it is torque over time, not dependant upon fuel or where the energy comes from.

Roast beef 'n' swiss hoagie for me... love that Horse Radish...

Rupurt

Fuel comes in where the energy is required the more fuel you can burn in a given time the more energy will be availble. energy is required to do the work which is needed for the power. So yes fuel type and flow is a factor

William Robison

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[b]Here we go again.

Bill.

JettPilot

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I have never gotten involved in the torque versus horsepower debate in this forum, but I am willing to jump in

Rv7garage

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Rupert- I understand what you are saying, but at the very basic level there is no need to put fuel into the equation. I think we are starting to beat a dead....horse...

Flyboy Dave

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Here's the equasion I go by....if a 1,000 pound horse walks up a 33 foot high
ramp in one minute, then lifts his tail and deposits 5 pounds of used hay on
ground behind him....

....what do you end up with ????

FBD.

Rupurt

"I have never gotten involved in the torque versus horsepower debate in this forum, but I am willing to jump in "

I don't see where the versus part comes in

Power = Torque X angular speed , where torque is in newton meters, power is watts and Angular speed is radians/s

Rv7garage

My Feedback: (10)

HAW.

Rupurt

"Rupert- I understand what you are saying, but at the very basic level there is no need to put fuel into the equation. I think we are starting to beat a dead....horse... " well in the "real world" it is important not many of us ever seem to visit there. I think the term is "Flossing a dead horse"

Rv7garage

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There really is no debate. Horsepower is torque with a time factor added in: it gives us a measure of work done over time. Lets do one better- lets measure it in calories!

Rv7garage

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If what you are saying is: "I think it's important to know what the fuel consumption will be for a specific horsepower output", then I agree- but now you are talking about efficiency- which can be a real flossing nightmare (cripes, the puns are a'flowing!). There is nothing wrong with starting with the basics, though.

Rupurt

What I am saying is the rate at which an engine can convert chemical energy into kinetic energy directly related to it's power output. In otherwords the more fuel an engine can process in a given time the more power it can deliver. The easiest way to make an engine process more fuel is increase it's displacement duh[X(].

just thought I had better add

In fact think of it like this. As you increase your altitude the pressure drops and less air enters the cylinders this effects the engines ability to process the fuel, decreasing horsepower AS you may or may not know you will need to decrease fuel flow (lean) as you ass-end. this demonstrates clearly the relationship of fuel flow and power.

MJD

My Feedback: (1)

Of course it doesn't matter where the energy comes from. The only reason I threw fuel in my comment is that in the end (other factors being equal) in the world of comparing internal-combustion engines burning the same fuel, the amount of horsepower generated is PRIMARILY dependent on how much fuel burned per second. I also noted that efficiency of the engine comes into play. The reason I stated it that way, is that some people argue that two otherwise identical motors, set up optimally for two different rpms (let's say for fun two .50's, one set up to produce its maximum horsepower at 10,000 rpm, and another at 18,000 rpm) can produce the same horsepower. They can't. The motor running at 18,000 rpm has 1.8 times as many combustion cycles per second, a correspondingly higher fuel consumption rate, and correspondingly more horsepower potential. In other words, there's a real good reason F1 cars and Pro Stock dragsters are running their engines at insane rpms - more horsepower per unit of displacement. But in the world of aircraft, we run into tradeoffs where the aircraft performs better on props that are not necessarily the ones that take the motor to its peak HP output. Lots of other factors in that equation.

I remember at the flying field one day watching someone fly some sport airplane, and climbing vertically for a while. The engine wasn't running very high rpm, IIRc it ws a .60 on a 12 or 13 inch prop. One of the wags at the field commented [verbatim] "look, she's torquin' 'er up!". Okay then..

Rupurt

Turbines generate insane power, they're on a permenant powerstroke and can process fuel much faster than similar sized piston engines. An example, the wren turboprop weighs under 2kg it can burn 190ml of kero in a minute and produce 7hp.

JettPilot

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Bill,

You have gone off on a tangent. The origional issue is PITCH contorls ALTITUDE, not power.

Its possible to be in a full power screaming dive all the way into the ground, by applying ELEVATOR to do it. If you pitch down with the elevator, all the power in the world is not going to change that. So ELEVATOR is the primary means of control to change pitch and altitude, NOT POWER.

Elevator is contolling PITCH. The pitching down the elevator creates makes the plane go "downhill" which has a huge influence on airspeed. But elevator controls Pitch directly, not airspeed (even though it has a big effect on airspeed). You statement is simply wrong.

JettPilot

My Feedback: (6)

I suggest you study your aerdynamicas Bill. Because you are proven wrong 10,000 times a day, every time an autoflight system on an airliner flys an ILS approach, using the THRUST to change airpseed, and the ELEVATOR to correct to glidepath deviations.

ITS THAT SIMPLE...

William Robison

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[b]JP:

You still don't get it, and I'm tired of explaining it.

Bill.

bob27s

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if i recall last time i was in a simulator, the instructor had me control rate of decent and slope using the throttle, and forward velocity was controlled with subtle movements using the elevator . Nose down, plane goes faster, nose up, plane slowed down. All this while trying to maintain a decent AOA , deal with the 20 deg cross wind, keep the numbers over the nose, and keep on the center line. Fun Gravity is an amazing thing.

Im out.

Bob

Flyboy Dave

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I'm outta here too (unsubscribed)....he ain't gonna get it. []

FBD.

Hobbsy

My Feedback: (102)

Per RCadmin this has been cleaned up some and moved to the new Off Topic Forum, have your way with it gentlemen.

RCKen

My Feedback: (9)

Ok, as Hobbsy said, this thread has been moved to the "Off Topic - Planes/heli's" forum. I've unlocked this thread if anybody wants to continue this discussion. I've read this thread and it has become heated at times, so I do ask that the discussion abide by the RCU rules of posting

Thank you all for following the rules

Ken

jon_focal_plane

Bob,

I'm on short final just above stall speed. I'm gonna come up a bit short of the runway so, what do I do? If I pull up with elevator, I stall the plane. I need to reduce my rate of decent a bit so I add some power. It's worked for me (full scale and rc). There could be some elevator/pitch action in there as well, but I'm mostly using pitch to keep above the stall speed in this flight regime.

jde