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King Air down at Essendon?

Old 6th Apr 2017, 09:22
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Originally Posted by FGD135
You cannot tell from RPM alone whether the engine is "making power". Positive torque would be a more correct term for this, by the way.

To determine whether positive torque existed or not requires knowledge of the RPM and the propeller blade angle.

It is self evident that the torque produced by the L engine was a very low value. Possibly positive, possibly negative.
Splitting hairs over torque and power there old mate.
Why is it self evident that left engine at low torque?
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Old 6th Apr 2017, 13:15
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Why is it self evident that left engine at low torque?
The flight path and performance give it away.
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Old 6th Apr 2017, 14:08
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One thing I've never heard talked about anywhere is reducing power on the live engine, if the other has failed, and you find yourself playing with Vmca. Much is written about handling engine failures in the take off scenario, but not this particular aspect. It was SOP on some WWII types, P-38 for example. It is addressed in the King Air emergency procedures section, reduce power on the live, but I wonder how many King Air drivers get to practice in a sim? Melbourne does have one.
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Old 6th Apr 2017, 15:26
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Originally Posted by FGD135
The flight path and performance give it away.
Thanks for that.
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Old 6th Apr 2017, 21:48
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Originally Posted by FGD135
You cannot tell from RPM alone whether the engine is "making power". Positive torque would be a more correct term for this, by the way.

I have said that Tq is what makes power from the start. What im saying here is at 2000 rpm it is making power ie what is the min Tq at 2000rpm ? . Max Tq at full fine at take off power is controlled by the power lever not via the prop lever.
Therefore the Tq at this speed is better min and max.

At 1586 rpm the engine is not considered in the power range as it is not in prop gov min speed range.
Therefore it has not even meet min Tq.

To determine whether positive torque existed or not requires knowledge of the RPM and the propeller blade angle.

It is self evident that the torque produced by the L engine was a very low value. Possibly positive, possibly negative.
Negative Tq. Are you really sure. Are you saying the prop is in beta range or feather. Therefore the slash marks on the roof arnt slash marks which now marks what of the 2000 to 1586 rpm that has been quoted.
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Old 7th Apr 2017, 03:35
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Therefore the slash marks on the roof arnt slash marks which now marks what of the 2000 to 1586 rpm that has been quoted.
It is impossible to understand what you are stating or asking here, Connedrod. In your days as yr_right you were similarly impossible to understand at times.

In the beta range or feathered? Nah.

Positive or negative torque? Impossible to tell with the facts we have at the moment, but if I was a betting man, I would go for negative as this is the more likely, given the appearances (one of which is the significant sideslip, revealed by the tyre marks, that was evident when the aircraft made first contact with the roof).
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Old 7th Apr 2017, 04:18
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As a layman, how can you have negative torque? Zero or above I understand but negative?
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Old 7th Apr 2017, 05:17
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Octane,

Negative torque is when the prop is driving the engine. Normally, the torque is positive and the engine drives the prop. When an aircraft engine is being driven by the prop, it means that the powerplant is extracting considerable energy from the air stream - which in other words means "creating considerable drag".

There are lots of different terms that all mean the same thing:

- "Windmilling"
- "Backdriving"
- "Discing"
- "Negative torque"

You would be familiar with negative torque in your car. Take your foot off the accelerator and allow the car to coast. The revs will stay high, but this is because the wheels are now driving the engine's rotation. You have switched from positive torque to negative.
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Old 7th Apr 2017, 05:32
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Octane,

I should have added that to achieve negative torque, the engine must have failed or had its torque production reduced down and past zero.

There is speculation that the L engine of this King Air had its torque production reduced by the action of the power lever sliding back from the takeoff position.

Note that the prop RPM is varied by varying the blade angle. These blade angle changes directly increase or decrease the torque and can cause the torque to go negative, if it was originally a small, positive value.

In the crash of the Colgan Airlines Dash 8 Q400 in 2009, I believe that a causal factor was the sudden transition to negative torque that occurred when the pilots increased the prop RPM as part of their pre-landing procedure. I believe the torque was a small positive before this, but the torque decrease from changing the blade angles made it negative - thus precipitating a dramatic reduction in airspeed.
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Old 7th Apr 2017, 05:38
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To set zero thrust the manual has this to say,
SIMULATING ONE-ENGINE-INOPERATIVE (ZERO THRUST)
When establishing zero thrust operation, use the power setting listed below. By using this power setting to establish thrust, inherent delays of restarting a shut-down engine are avoided and almost instant power is available to counter any attendant hazard.
1. Propeller 1600 RPM
2. Power Lever Set 100 ft-lb torque
NOTE:
This setting will approximate Zero Thrust at low altitudes using recommended One-Engine-Inoperative Climb speeds. Because the differential rudder boost system may not activate, rudder forces may be higher than those with an actual engine failure.
If that is zero thrust Connedrod, what do you reckon a TQ setting <100 ft-lb would give you?
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Old 7th Apr 2017, 08:49
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Originally Posted by FGD135
It is impossible to understand what you are stating or asking here, Connedrod. In your days as yr_right you were similarly impossible to understand at times.

In the beta range or feathered? Nah.

Positive or negative torque? Impossible to tell with the facts we have at the moment, but if I was a betting man, I would go for negative as this is the more likely, given the appearances (one of which is the significant sideslip, revealed by the tyre marks, that was evident when the aircraft made first contact with the roof).
Really so the figures given between 2000 down to 1586 Np. Pt6-42 is a free turbine engine. And even at a Np of 1586 the engine would be driving the prop. If you understand the engine and how it works and given the facts that are already proven and documented you can say that the prop was not free spining. Slide sliping across the roof of tne main wheel can caused by multiple reasons.
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Old 7th Apr 2017, 13:56
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And even at a Np of 1586 the engine would be driving the prop
Maybe, maybe not. All you can tell was the prop was rotating. For the zero thrust setting of 100/1,600 and using recommended One Engine Inoperative Climb speeds the engine is producing no prop thrust, but consuming 30.46 shaft horse power just to rotate the prop. If you were to reduce TQ to 10 ft-lb and the prop maintained 1,600 RPM, that means the slipstream is contributing 27.4 SHP. What the prop RPM at zero TQ and recommended One-Engine-Inoperative Climb speeds I have no idea.
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Old 7th Apr 2017, 20:43
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How confusing you all are.
The prop is now at discing or less.
The prop is also driving the "engine".

I'll have to find my Pratt course notes and rewrite some of them.

Connedrod, maybe this engine has a clutchpack in the PRG.

Last edited by Eddie Dean; 7th Apr 2017 at 21:44.
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Old 8th Apr 2017, 02:14
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Originally Posted by megan
Maybe, maybe not. All you can tell was the prop was rotating. For the zero thrust setting of 100/1,600 and using recommended One Engine Inoperative Climb speeds the engine is producing no prop thrust, but consuming 30.46 shaft horse power just to rotate the prop. If you were to reduce TQ to 10 ft-lb and the prop maintained 1,600 RPM, that means the slipstream is contributing 27.4 SHP. What the prop RPM at zero TQ and recommended One-Engine-Inoperative Climb speeds I have no idea.
Finally you are correct. You have no idea at all do you. Zero thrust is only in the Beta condition. All other positions are ever forward or reverse thurst. And what is the primary perpose of the auto freather in the B200.
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Old 8th Apr 2017, 02:32
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Originally Posted by Eddie Dean
How confusing you all are.
The prop is now at discing or less.
The prop is also driving the "engine".

I'll have to find my Pratt course notes and rewrite some of them.

Connedrod, maybe this engine has a clutchpack in the PRG.

Yes its called an air drive between the cold and the hot section lol.
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Old 8th Apr 2017, 10:22
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Originally Posted by megan
Maybe, maybe not. All you can tell was the prop was rotating. For the zero thrust setting of 100/1,600 and using recommended One Engine Inoperative Climb speeds the engine is producing no prop thrust, but consuming 30.46 shaft horse power just to rotate the prop. If you were to reduce TQ to 10 ft-lb and the prop maintained 1,600 RPM, that means the slipstream is contributing 27.4 SHP. What the prop RPM at zero TQ and recommended One-Engine-Inoperative Climb speeds I have no idea.

Do you understand how the Tq is calculated. Do you understand that the oil suply to the prop at 1600 RPM IS AT VERY BEST ONLY JUST in gov range. This means to gov the prop is unlikely to occur. However to have the Tq at ZERO Tq and a prop speed of 1600 rpm is impossible. For Zero tq means the gas generator must be stopped. This means no oil px to the power section. This means no oil to the gov. This means Zero oil to the prop. This means the counter weights and spring will place the prop into feather by its self with Zero input via any pilot input. This means rotational speed of the prop is amlost zero. This means your statement of i have no idea is true and correct. Therefore any speed of the prop is producing forward thrust. The only thing now is how much it was producing.
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Old 8th Apr 2017, 11:54
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However to have the Tq at ZERO Tq and a prop speed of 1600 rpm is impossible.
How so? The airflow can drive the prop.

A prop on an aircraft in flight does not stop spinning when the engine fails. The engine is producing no TQ yet the prop continues to turn.
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Old 8th Apr 2017, 12:21
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Connedrod,

Don't drink and post.

Do you understand that the oil suply to the prop at 1600 RPM IS AT VERY BEST ONLY JUST in gov range.
Complete rubbish.

However to have the Tq at ZERO Tq and a prop speed of 1600 rpm is impossible. For Zero tq means the gas generator must be stopped. This means no oil px to the power section. This means no oil to the gov. This means Zero oil to the prop.
Complete rubbish also.

You obviously cannot understand what is happening with the power plant IN FLIGHT. All of your experience and knowledge of this power plant is when you are doing static run ups, stationary ON THE GROUND.

What you have claimed may well be true - FOR A STATIC RUN UP, ON THE GROUND.

Zero thrust is only in the Beta condition.
On the ground, during a static run up, yes. But in flight, things are different.
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Old 8th Apr 2017, 13:00
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Good point.

How many hours in command of the B200 - or any aircraft for that matter - do you have Connedrod?
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Old 8th Apr 2017, 20:21
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You obviously cannot understand what is happening with the power plant IN FLIGHT. All of your experience and knowledge of this power plant is when you are doing static run ups, stationary ON THE GROUND.

What you have claimed may well be true - FOR A STATIC RUN UP, ON THE GROUND.

On the ground, during a static run up, yes. But in flight, things are different.[/QUOTE]

Really.

So how dose the feather system work ?
Any power via the gas producer will transmit power to the propeller. There will always be Tq indicated. Especially when the quoted airspeed of 108 knots.
What is the min gov speed on a B200 and at what Ng is. Approx will do.
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