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Originally Posted by FGD135
(Post 9730832)
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. Why is it self evident that left engine at low torque? |
Why is it self evident that left engine at low torque? |
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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Originally Posted by FGD135
(Post 9731249)
The flight path and performance give it away.
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Originally Posted by FGD135
(Post 9730832)
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. |
Therefore the slash marks on the roof arnt slash marks which now marks what of the 2000 to 1586 rpm that has been quoted. 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). |
As a layman, how can you have negative torque? Zero or above I understand but negative?
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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. |
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. |
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. |
Originally Posted by FGD135
(Post 9731903)
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). |
And even at a Np of 1586 the engine would be driving the prop |
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. |
Originally Posted by megan
(Post 9732363)
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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Originally Posted by Eddie Dean
(Post 9732712)
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. |
Originally Posted by megan
(Post 9732363)
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. |
However to have the Tq at ZERO Tq and a prop speed of 1600 rpm is impossible. 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. |
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. 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. 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. |
Good point.
How many hours in command of the B200 - or any aircraft for that matter - do you have Connedrod? |
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. |
Gotta love the old LAME vs Pilot arguments on engine operation...
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Originally Posted by Squawk7700
(Post 9733555)
Gotta love the old LAME vs Pilot arguments on engine operation...
Squawk it appears to me that it is more a case of ex military officers having problems with the ORs disagreeing with them. I was once at a debrief after a Caravan had an engine roll back to 56% Ng in flight and the pilots dead sticked about 15 mile to a beach. Memory is a bit iffy, Taily and can correct me, but during restart attempts the engine was shut off and the Ng dropped to zero, subsequent restarts didn't achieve self sustain RPM. Propellor rotation will only rotate the power section, it will not turn the gas generator. As Ramrod has previously explained, to achieve the 18% or more gas generator speed to effect successful lightoff, one needs a high airspeed for ram air to spin the compressor section to this RPM. As Connedrod has explained, without sufficient Ng the oil pump pressure will not be high enough to deliver sufficient pressure to the CSU to pump oil to maintain propellor blade angle and may in fact come back to feather. |
Eddie
We know the engine was operational at the time of impact. This is because the prop was not in a freathered position. At least postion of the condition levers may have been in two possibly positions of grd idle of 52% or flight idle of 72% ng. It should be at the later. At in 72% it would not have zero tq. This is the min speed of the N1 if the power lever is brought back to the idle position. With out oil px the prop will not and cannot stay in fine pitch. In this case the posibity of auto freather may or may not have worked. Auto freather only purpose is to help the pilot from removing power from the wrong engine if there is a problem. If the engine has a completely lost power from the cold section it will freater its self. It can be seen from the pics that one of the engines was not in the freathered position. We at this stage ate only think it was the left engine which has had the problem. Astb reports say that both engines internal assy where operational. |
What's freather?
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We know the engine was operational at the time of impact. This is because the prop was not in a freathered position. ... two possibly positions of grd idle of 52% or flight idle of 72% ng. With out oil px the prop will not and cannot stay in fine pitch. In this case the posibity of auto freather may or may not have worked. There is plenty of oil pressure at all normal engine speeds. I believe there is plenty even at speeds as low as 20% Ng. During start, the prop begins to unfeather well before the Ng is fully up to speed. Auto freather only purpose is to help the pilot from removing power from the wrong engine if there is a problem. |
The lever can be set at intermediate positions |
We talking the fuel/condition lever?
Yes it can be set at intermediate positions between low and high idle. |
Originally Posted by Car RAMROD
(Post 9733739)
We talking the fuel/condition lever?
Yes it can be set at intermediate positions between low and high idle. |
Just now read the PT6 manual. Idle reset has only two positions. There appears to be no intermediate position. If you have it in low idle you can increase RPM with the throttle.
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Originally Posted by FGD135
(Post 9733708)
You cannot draw that conclusion from that evidence.
King Air operators have a variety of policies in regard of where the condition levers are set. For the 4 bladers, I believe the low idle setting is 60%, not 52%. The lever can be set at intermediate positions (e.g. 62%). If they needed airconditioning that morning, it is possible the R engine was at 62%, with the left at 60%. It is possible both were at 60% - or 62%. It is unlikely that both were at 70%. More lilely they should be at 70% high idle. This should be used for take off and landing. The A/C should be in in the OFF position for take off and landing. Contradicting yourself. You seem to be saying that with the loss of oil pressure, the prop will feather. Then you say that, without oil pressure, the autofeather may not work. (!) No saying that with out oil px the prop will freather. But as the engines are working it may not work as the Tq is above the low setting to activate. There is plenty of oil pressure at all normal engine speeds. I believe there is plenty even at speeds as low as 20% Ng. During start, the prop begins to unfeather well before the Ng is fully up to speed. Are you joking 20% is around light off Ng. The engine is not even close to self substanting its self. 50%Ng is when the engine will hold its own. Wrong. The pilot can still inadvertently feather the good engine. If the bad engine has autofeathered, the good can still be manually feathered. |
[QUOTE=FGD135;9733708]You cannot draw that conclusion from that evidence.
We sure can. Atsb have stated it. Indication marks on the roof are port to starboard in a forward diection. Not fwd to rear in a fwd diection meaning the prop was not in feather position. Meaning the prop had oil px. Meaning the only way tne prop can have oil px is if the engine was running. This means the egine was above 50% N1 at inpact. And when the correct prop speed is determined if its below min gov speed a Tq value will be able to be determined. Above min gov it may not be able to be known. |
Does the report stating that the engines were operative relate to the state of the fuel system?
Mickjoebill |
Originally Posted by Eddie Dean
(Post 9733820)
Just now read the PT6 manual. Idle reset has only two positions. There appears to be no intermediate position. If you have it in low idle you can increase RPM with the throttle.
Are you talking about up at the fcu? Of course you can increase rpm with the power lever (throttle). You can also increase it with the condition lever- anywhere between the low and high idle positions. Push the lever forward a bit, stop, it stays there with a corresponding increase in idle speed. Mick, the report doesn't say the engines were "operative". It just says that the cores were rotating at impact but they don't indicate at what possible speeds. Ram airflow will spin the core of a PT6. All that highlights is for example it hadn't seized up/disintegrated etc. State of the fuel system cannot really be figured out directly from the information at hand. I'm sure they'll investigate what components they can, and if it was refuelled locally I'd imagine they'd already have copies of the delivery docket and samples from the truck. |
In keeping with The Australian's propensity for dishing up largely confected pap on its Aviation pages, today we're treated to Ean Higgins' ATSB report ‘may have prevented Essendon plane tragedy’. Higgins reports that Dick Smith contends that;
THEN everyone would have lived happily ever after. |
I'm hoping that's not an even ball-park close report of Dick's views. If they are, it is sad to see the onset of dementia in a once-great Australian. :{
The safety regulator investigated and took regulatory action against Mr Q in relation the Hotham incident. |
Ah Dick. Do you really think that IF he was found at fault for Hotham, and grounded for a time period (unlikely, let alone long enough to cover the time period of the accident flight) that this accident wouldn't have occurred?
That's a very, very long bow to draw. Mick, that's indeed a lot of IF's! |
Originally Posted by Lead Balloon
(Post 9734459)
I'm hoping that's not an even ball-park close report of Dick's views. If they are, it is sad to see the onset of dementia in a once-great Australian. :{
Dick Smith, a former chairman of the Civil Aviation Safety Authority, said it was “completely inexcusable” that the ATSB had still not completed the report of its investigation of the September 2015 incident at Mount Hotham. He told The Australian that had the ATSB completed its investigation and report within a reasonable timeframe, and concluded that pilot Quartermain had engaged in poor airmanship endangering lives, he might have been grounded. In that case, Mr Smith said, Quartermain would not have piloted February’s flight in which he and four American passengers died when the Beechcraft King Air crashed into a shopping centre nine seconds after it took off from Essendon airport. |
Mick, the report doesn't say the engines were "operative". It just says that the cores were rotating at impact but they don't indicate at what possible speeds. Ram airflow will spin the core of a PT6. All that highlights is for example it hadn't seized up/disintegrated etc.
State of the fuel system cannot really be figured out directly from the information at hand. I'm sure they'll investigate what components they can, and if it was refuelled locally I'd imagine they'd already have copies of the delivery docket and samples from the truck.[/QUOTE] Two men say they Jesus one of them must be wrong. Ppruners say prop speed between 1586 and 2000 rpm. For this the engine must be running. Slash marks indication show prop not in feathered position. Prop will feather with no oil Px from the cold section. Ram air will not supply enough oil to hold the prop in fine without oil the cold section working. So is the fuel system working or not. |
Probably shouldn't try getting into the argument but here goes anyway.
Relative wind, no seizure, ram airflow. Windmilling. Hence the term. There is enough airflow through the compressor section driving the oil pump, to the prop governor, to keep the blades towards fine. If not, please explain the windmill start procedure! I'd say go and try it- but not in a 4 blader because the drag sucks! Conned, please leave the discussion to those who know what they are talking about. |
Car RAMROD,
I think it best not to engage with Connedrod. It is quite apparent that he has poor written english, but having debated him over the last few days, can report that he his comprehension of written english is similarly abysmal. It is impossible to have a rational debate with this kind of person. You are wasting your time. To everybody else, I urge no engagement with this individual, and strongly back this statement from Car RAMROD: Conned, please leave the discussion to those who know what they are talking about. |
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