B206 Torque
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B206 Torque
Any ideas why the torque on a 206 would be sitting at around 40% at flat pitch and at flight idle on the ground? I would expect it to at least 10% lower at this setting.
Once flying torque figures seem pretty standard with other 206's ive flown.
Cheers
Once flying torque figures seem pretty standard with other 206's ive flown.
Cheers
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I had suspected it could be to do with the auto RPM setting. I have only flown this particular machine a couple of times and am unware as to how long it has been doing it.
I do no that nothing has been changed recently in regards to rotor heads so hopefully no dramas with installation.
I do no that nothing has been changed recently in regards to rotor heads so hopefully no dramas with installation.
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Thanks for the replys so far.
Flight Idle being collective at flat pitch and throttle fully open.
The airspeed at 80% torque seems about right for a jetranger. Cant remember of the top of my head n1 at flight idle, but n2 was at 100%. Havent done an auto in it yet but will try soon.
Flight Idle being collective at flat pitch and throttle fully open.
The airspeed at 80% torque seems about right for a jetranger. Cant remember of the top of my head n1 at flight idle, but n2 was at 100%. Havent done an auto in it yet but will try soon.
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Erm. You might want to check with an engineer before doing an auto. I'm absolutely not an expert, but if it takes a lot of power from the engine to turn the blades with the collective all the way down, then it seems to me that the autorotative airflow will also struggle with the same task, and you may well have rpm problems.
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The engineer will just have you do an autorotation RPM check anyway. The 206 is about as benign a helicopter as you can find in autorotation, and a prudent pilot would get plenty of altitude before entering anyway, and pay attention to the RPM and start a power recovery before the RPM gets out of the green. I've never seen the Nr in a 206 dangerously low with the collective full down, and they have lots of blade inertia.
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I will speak with the engineer tomorrow and as everyone has said I suspect the auto RPM will be a bit low.
Hopefully it will be a quick fix by adjusting the lower pitch setting with collective all the way down.
Hopefully it will be a quick fix by adjusting the lower pitch setting with collective all the way down.
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Umm are you sure you don't mean 'flight rpm'? with club down & presumably flat pitch with the throttle wide open? to me that would be flight rpm as opposed to 'ground idle' club down throttle back to detent possie.
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Semi Rigid:
On the 206,
Nr/N2 at 100%, collective at min pitch = Flight Idle
N1 at 58% to 62%, collective at min pitch = Ground Idle
A couple of things could be the culprit, either Tq. gage is incorrect or Autorotoation RPM is too low or a combination of both. Since he said his cruise speed at 80% Tq looked about right, my hunch is low auto rev's. An easy flight check for auto rev's would be the first place to look followed by testing the tq gage with a dead wt. tester.
I would also suspect the aircraft felt light on the ground and took a lot less of collective travel to get it light on the skids.
Chuck
On the 206,
Nr/N2 at 100%, collective at min pitch = Flight Idle
N1 at 58% to 62%, collective at min pitch = Ground Idle
A couple of things could be the culprit, either Tq. gage is incorrect or Autorotoation RPM is too low or a combination of both. Since he said his cruise speed at 80% Tq looked about right, my hunch is low auto rev's. An easy flight check for auto rev's would be the first place to look followed by testing the tq gage with a dead wt. tester.
I would also suspect the aircraft felt light on the ground and took a lot less of collective travel to get it light on the skids.
Chuck
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Semi Rigid.
I agree with chuckolamofola. And if you like at my previous post I defined flight idle as "Flight Idle being collective at flat pitch and throttle fully open"
I didnt notice needing less collective to get machine light on skids than normal but it could well have been.
Cheers
I agree with chuckolamofola. And if you like at my previous post I defined flight idle as "Flight Idle being collective at flat pitch and throttle fully open"
I didnt notice needing less collective to get machine light on skids than normal but it could well have been.
Cheers
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This is my first post, so be gentle. As your question was about torque on the 206 I suggest you do this. Do not fly it. On a ground run do your normal start and when you increase the rotor speed over the N2 yellow caution band bring the twist grip back to the Idle Detent. Your N2 NR needles should be above the N2 yellow caution band. If it is not then you probably will not be able to autorotate, well not for long. An engineer should be able to sort this out, ie if you are below the yellow band the pitch links should be shortened. The other check would be to check your engine oil pressure is in tolerance. Torque is measured by a modulated engine oil pressure, so if the engine oil pressure is high so the torque reading will be high, and vice versa. Hope this helps
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The torque reading is directly proportional to the engine oil pressure being produced at the N1 rpm.
Look at your oil pressure and torque readings and run up slowly while watching engine oil pressure.
Torque readings are only accurate while engine oil pressure is in the double green band of the gauge.
Look at your oil pressure and torque readings and run up slowly while watching engine oil pressure.
Torque readings are only accurate while engine oil pressure is in the double green band of the gauge.
jeffrey1 - really? Where did you get that information?
The only reason an A250 has such high oil pressure is to make the Q meter work. The lube side does not need high pressure but is subsequently designed to operate with it. In other words low oil pressure is a problem for the lube system as it is designed. I am not saying that low oil pressure is not an issue. The oil pressure is regulated in the engine and only needs to be adjusted to higher than the demands of the Q meter system.
The following probably sums it up quite neatly.
United States Patent 4690614
A torque meter is provided for use in conjunction with a layshaft having a forward and rear end and which is rotatably mounted in a housing. The layshaft is axially movable with respect to the housing between a forward and a retracted position while a gearing arrangement in mesh with the layshaft urges the layshaft towards its forward position with a force proportional to the shaft torque due to the helical cut of the gears. The torque meter comprises a body secured to the housing adjacent the front end of the layshaft which forms a chamber open to the front end of the layshaft while a piston is axially slidably mounted within the chamber. The chamber is pressurized with a fluid, such as oil, which urges the piston against the front end of the layshaft with a force proportional to the pressure so that the piston balances the layshaft against the axial force imposed by the engine. A fluid pressure gauge determines the pressure within the chamber which varies proportionately with the layshaft torque. In addition, a piston ring on the piston opens the fluid chamber to an opening in the body and a passageway in the housing when the layshaft moves to its rearward position, indicative of a negative shaft torque condition, whereupon fluid discharges from the chamber, through the passageway.
From memory on a 20 series the pressure equates to 1 PSI = 4HP at 100% N2. Any difference in N2 and these numbers will change.
As to the Jetbox high Q at flat pitch - most obvious is too much pitch.
If the passageway (bleed) is blocked or restricted your Q meter will read engine oil pressure or be slow to indicate less Q as appropriate.
The only reason an A250 has such high oil pressure is to make the Q meter work. The lube side does not need high pressure but is subsequently designed to operate with it. In other words low oil pressure is a problem for the lube system as it is designed. I am not saying that low oil pressure is not an issue. The oil pressure is regulated in the engine and only needs to be adjusted to higher than the demands of the Q meter system.
The following probably sums it up quite neatly.
United States Patent 4690614
A torque meter is provided for use in conjunction with a layshaft having a forward and rear end and which is rotatably mounted in a housing. The layshaft is axially movable with respect to the housing between a forward and a retracted position while a gearing arrangement in mesh with the layshaft urges the layshaft towards its forward position with a force proportional to the shaft torque due to the helical cut of the gears. The torque meter comprises a body secured to the housing adjacent the front end of the layshaft which forms a chamber open to the front end of the layshaft while a piston is axially slidably mounted within the chamber. The chamber is pressurized with a fluid, such as oil, which urges the piston against the front end of the layshaft with a force proportional to the pressure so that the piston balances the layshaft against the axial force imposed by the engine. A fluid pressure gauge determines the pressure within the chamber which varies proportionately with the layshaft torque. In addition, a piston ring on the piston opens the fluid chamber to an opening in the body and a passageway in the housing when the layshaft moves to its rearward position, indicative of a negative shaft torque condition, whereupon fluid discharges from the chamber, through the passageway.
From memory on a 20 series the pressure equates to 1 PSI = 4HP at 100% N2. Any difference in N2 and these numbers will change.
As to the Jetbox high Q at flat pitch - most obvious is too much pitch.
If the passageway (bleed) is blocked or restricted your Q meter will read engine oil pressure or be slow to indicate less Q as appropriate.
Avoid imitations
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Has the aircraft rigging actually been disturbed? When was this problem first noticed?
Something worries me about this - this might be so obvious that it has (hopefully) already been taken into consideration. A failing gearbox bearing would require more torque to turn it.
Has someone checked that the main rotor gearbox turns without undue resistance or noise? Does it slow down to "stop" after engine shutdown in a normal manner and period of time?
I was once flying an aircraft with a failing main gearbox. We had no real symtoms or indications in the cockpit except for a tiny bit of extra vibration (we had no torque gauge on that type, we only had a collective pitch gauge). On our return, we spoke to the engineers, who pulled an oil sample. The mag plug had a piece of ferrous metal stuck on it that was so big it wouldn't come out of the plug hole.
So take care!
Something worries me about this - this might be so obvious that it has (hopefully) already been taken into consideration. A failing gearbox bearing would require more torque to turn it.
Has someone checked that the main rotor gearbox turns without undue resistance or noise? Does it slow down to "stop" after engine shutdown in a normal manner and period of time?
I was once flying an aircraft with a failing main gearbox. We had no real symtoms or indications in the cockpit except for a tiny bit of extra vibration (we had no torque gauge on that type, we only had a collective pitch gauge). On our return, we spoke to the engineers, who pulled an oil sample. The mag plug had a piece of ferrous metal stuck on it that was so big it wouldn't come out of the plug hole.
So take care!
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I received that information from the Bell factory school in which I just returned from last week.
They explained in detail about the torque system and the double green lines on the engine oil pressure gauge.
They explained in detail about the torque system and the double green lines on the engine oil pressure gauge.
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Thanks for all the replys so far.
ShyTorque. The blades slow down and start up at the same speed as on any jetranger I have seen.
jeffrey1. Very usual information.
I did some autos in the machine yesterday to check auto RPM and it was fine. 100% with collective down so no dramas there.
I have been told that the problem could be something as simple as a small object lodged somewere in the actual line running to the torque gauge. And apparently to retreive the "object" you have to pull the whole accessory gearbox apart. Any views on this?
ShyTorque. The blades slow down and start up at the same speed as on any jetranger I have seen.
jeffrey1. Very usual information.
I did some autos in the machine yesterday to check auto RPM and it was fine. 100% with collective down so no dramas there.
I have been told that the problem could be something as simple as a small object lodged somewere in the actual line running to the torque gauge. And apparently to retreive the "object" you have to pull the whole accessory gearbox apart. Any views on this?