Bell 206: JetRanger and LongRanger
Join Date: Jun 2005
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Its been a few years since I flew the 206 in flight in autorotation we always had a big needle split.
On one 206 I flew there was no needle split in autorotation when the throttle was closed so the aircraft was grounded and repaired, Sorry but I don't know what the problem was it was some time back.
On one 206 I flew there was no needle split in autorotation when the throttle was closed so the aircraft was grounded and repaired, Sorry but I don't know what the problem was it was some time back.
Join Date: Jul 2004
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I would have to agree with Nick's camp on this one as well. You should get a needle split. However before I started looking at the big spendy parts like the sprag clutch I would check to see if the aircraft is lying to us. If memory serves me correctly the NR/N2 gauge has two cannon plugs on the backside one for each indication and it is very easy to reverse them. I have seen this before and it isn't always caught early on. I would expect if this was the case that you would still get a needle split but it would be reversed (NR would drop off and N2 would remain) but stranger things have happened. Just a thought worth considering but above and beyond that the freewheel clutch it is.
Max
Max
Join Date: Apr 2003
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good idea, Max, and less expensive! Not likely, if the gauge has behaved right otherwise, but still a good idea to check.
Bad clutch rollers can sometimes be flet and heard when the shaft is rotated by hand in the hangar. Sort of ratchety feeling and a snickity sound.
Bad clutch rollers can sometimes be flet and heard when the shaft is rotated by hand in the hangar. Sort of ratchety feeling and a snickity sound.
Join Date: Dec 2004
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Years ago I had a 206B have a clutch failure. Pilot reported a noise when the main rotor blade was rotated forward by hand. We rotated the main rotor forward and the power turbine turned with the blades. I removed the sprag clutch and found the cage of the clutch broken with a piece of the cage jammed in between the sprags.
Fly at your own risk.
Fly at your own risk.
Join Date: Feb 2002
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My old job at a Bell CSF involved doing a Maintenance Flight before and after a helicopter was recieved for maintenance, we would take all paramenters, idle, hover, flight, power check, control rigging, and Autorotation RPM, etc. etc. I have probably flown 40 different JetRangers and some get a needle split in Auto but some don't, at first I thought that wasn't right, but the mechanics said that it was ok as long as when you where on the ground, when you shut the engine down the needles would split, if they didn't then there were problems, but this was on engine shutdown.
In flight we have never made a discrepancy of the needles not splitting.
In flight we have never made a discrepancy of the needles not splitting.
Join Date: Oct 2003
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Gentlemen, I have to agree with Blenderpilot on this one, at mother rucker ,we do autos everyday and while the N1 goes to idle, we do not get a needle split between the N2 and nr , only on the shut down there is a positive split......
Wow. Darn. Now I'm really confused. And I mean scratching-my-head-confused. I've flown a 206 or two in my day. And I say: No definite N2/NR needle-split in a practice auto in a 206. Then people, including the "esteemed" N. Lappos jump down my throat and call me incorrect. Maybe I've only dreamt my career, that it didn't really happen? Perhaps.
N.L. sez:
Hmm, the N2needle goes to 65%? I've never flown an S-76, but this statement does surprise me. So what you're saying is that once the FCL is brought back to "idle," the governor is completely out of the picture, hmm?
Well I have to admit that I do not understand this statement. If we retard an FCL on an engine to "idle," then as you say that engine's N2 will go to 65%. Okay...but...how will lowering the collective cause that engine's N2 to go to 103%? Furthermore, why will that engine's N2 be "governed " to 103% if the governor is completely off-line? Maybe I better have a look at that schematic, Nick.
I think two things are happening here. Either Nicky is confusing N1 and N2 or he has forgotten how an S-76 flies. Hey, let's not be too hard on him- that's what happens when we get old.
I will admit that since I've never flown an S-76A, it is entirely possible that if you pull an FCL lever back, that engine's N2 might go to 65%. I doubt it, but it's possible. But I can say with confidence that the N2 needle of a 206 will definitely *not* go to 65 or 70% in flight with the throttle at "idle." Anyone who says otherwise is either fantasizing, doesn't understand how free turbine engines work, or has never flown a 206.
I guess I'll just wait and see if anyone else weighs-in on this topic. Maybe a former Bell Helicopter CSF pilot or a guy who flies at Rucker will shed some light on this and prove me wrong once and for all.
N.L. sez:
1) When the throttle on an Allison/RR is rolled to idle, the governor is put to bed, out of the picture. I could draw the schematic for ppf if he'd bother to read it. At idle, the CECO fuel control metering valve is pulled back to an essentially fixed position, which allows the engine to barely run. On an S-76A the idle will be about 65 to 70% if the throttle is pulled back, with the rotor at 100%.
2) The needles will split, virtually all the time, when you command the engine to idle with the throttle while the rotor is at 100%. If you just let the collective down and the rotor builds upward, the engine will still be governed, and will creep up to about 103%. This is called updroop, and is built into the governor for stability purposes.
I think two things are happening here. Either Nicky is confusing N1 and N2 or he has forgotten how an S-76 flies. Hey, let's not be too hard on him- that's what happens when we get old.
I will admit that since I've never flown an S-76A, it is entirely possible that if you pull an FCL lever back, that engine's N2 might go to 65%. I doubt it, but it's possible. But I can say with confidence that the N2 needle of a 206 will definitely *not* go to 65 or 70% in flight with the throttle at "idle." Anyone who says otherwise is either fantasizing, doesn't understand how free turbine engines work, or has never flown a 206.
I guess I'll just wait and see if anyone else weighs-in on this topic. Maybe a former Bell Helicopter CSF pilot or a guy who flies at Rucker will shed some light on this and prove me wrong once and for all.
Join Date: Feb 2005
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In PPfan1 defence.
I dont know what im talking about but i have a couple of thousand hrs in 206 and do autos at least 2/3 times week and never seen a needle split more than 8% or so, i just put it down to the lack of load on the N2 during auto, even the N1 idle sits a bit higher at times in auto than at ground idle, either the same or 1% more.
I also presume the free wheel unit aint so slopy so im guessing may be it will drag the N2 up a little, its bound to. Cant see this as a malfunction,
These are only my observations and are also recorded during test flights by maint: we run quite a few B206 and are all exactly the same give or take 1% or so.
Like i say, just what i see, never seen it any other way, maybe all our 206 should be grounded, ( i need a vacation )
hope this helps.
Will certainly dig a little deeper now. cheers. ( edit for my bad spelling)
I dont know what im talking about but i have a couple of thousand hrs in 206 and do autos at least 2/3 times week and never seen a needle split more than 8% or so, i just put it down to the lack of load on the N2 during auto, even the N1 idle sits a bit higher at times in auto than at ground idle, either the same or 1% more.
I also presume the free wheel unit aint so slopy so im guessing may be it will drag the N2 up a little, its bound to. Cant see this as a malfunction,
These are only my observations and are also recorded during test flights by maint: we run quite a few B206 and are all exactly the same give or take 1% or so.
Like i say, just what i see, never seen it any other way, maybe all our 206 should be grounded, ( i need a vacation )
hope this helps. Will certainly dig a little deeper now. cheers. ( edit for my bad spelling)
Last edited by skitzs; 10th Jul 2005 at 17:44.
To maybe cloud the issue a bit, in the 205 when we did maintenance test flights that required autorotation, we would for the first one lower the collective fully and look for a needle split (N2 vs Nr); then, having proven that it would autorotate, wind the throttle to idle from the cruise for subsequent entries, giving a marked needle split when the collective was then lowered, Nr recovered and N2 stayed down (can't remember the value it went to, but definitely below the governed range of 6000 to about 6700 from memory).
Going out in the 206 tomorrow so may get a chance to check the occurrence or otherwise of needle splits when the collective is lowered fully to enter the auto profile (won't be rolling the throttle off though).
Can I also put in a request for the maintenance (pardon the pun) of a non-bitchy forum, as we usually enjoy.
Going out in the 206 tomorrow so may get a chance to check the occurrence or otherwise of needle splits when the collective is lowered fully to enter the auto profile (won't be rolling the throttle off though).
Can I also put in a request for the maintenance (pardon the pun) of a non-bitchy forum, as we usually enjoy.
Join Date: Apr 2004
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Wasn't going to get into this but I will. As an ex-mil instructor with not an inconsiderable number of hours (and subsequent EOL's) on many Brit and US machines it is my experience that, almost always, the split between N2 and NR in stable autorotative flight is minimal,not so N1.
In the machine I currently fly and do autos in for Base Check/ conversion purposes, powered by a single PT6, the manufacturer saw fit to overlay the Mechanical Engine Control with an Electronic Engine Control to ensure an N2/NR split in auto. Not so the N1 which can hit a Flight Idle RPM in auto 6 or so % below the on ground, flat pitch Flight Idle - low enough to bring the ENG OUT warning on!
In a hard flaring manouvre the N2 will follow the NR up.
GAGS E86
In the machine I currently fly and do autos in for Base Check/ conversion purposes, powered by a single PT6, the manufacturer saw fit to overlay the Mechanical Engine Control with an Electronic Engine Control to ensure an N2/NR split in auto. Not so the N1 which can hit a Flight Idle RPM in auto 6 or so % below the on ground, flat pitch Flight Idle - low enough to bring the ENG OUT warning on!
In a hard flaring manouvre the N2 will follow the NR up.
GAGS E86
Join Date: Mar 2005
Location: chester uk
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jetranger type rating UK
I would be grateful for some recommendations for Jetranger type conversion training in the UK.
Preferably the cheapest one
Also preferably in the North or Midlands, however if the price was right i would travel. (its only a 5 hour course isn't it?)
Is 5 hours realistic for conversion from R22 and R44? or should i budget for more?
I will be flying one in the USA later in the year so to be able to log the hours (JAR logbook) i need to be type rated on my JAA licence.
If someone knows a way around this please let me know. I believe that the UK CAA can be really picky about people hour building in USA in helis that they are not rated for but still trying to log P1 hours .
Thanks in advance
Chester
Preferably the cheapest one
Also preferably in the North or Midlands, however if the price was right i would travel. (its only a 5 hour course isn't it?)
Is 5 hours realistic for conversion from R22 and R44? or should i budget for more?
I will be flying one in the USA later in the year so to be able to log the hours (JAR logbook) i need to be type rated on my JAA licence.
If someone knows a way around this please let me know. I believe that the UK CAA can be really picky about people hour building in USA in helis that they are not rated for but still trying to log P1 hours .
Thanks in advance
Chester
Join Date: Jan 2000
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mmmmm.....methinks most of you have little idea about how a free turbine engine works, including the governor, except for Nick Lappos and a couple of others above!!
PPN#1F..where did you get the impression that Nick said any thing about the N2 being at 70% at idle? Come on now, you must be aware he was referring to the N1.
And by the way, if you are in any doubt as to whether the governor on an Allison or RR 250 is working when the throttle or power lever/s is or are back at idle (in autorotation of course), try pulling the bloody lever up climbing away and see how quick your "governed" N2 gives up. Haven't ya noticed what happens to the N2 during the terminationof a practice EOL, even at the hover?
Defence rests, yer honour.
PPN#1F..where did you get the impression that Nick said any thing about the N2 being at 70% at idle? Come on now, you must be aware he was referring to the N1.
And by the way, if you are in any doubt as to whether the governor on an Allison or RR 250 is working when the throttle or power lever/s is or are back at idle (in autorotation of course), try pulling the bloody lever up climbing away and see how quick your "governed" N2 gives up. Haven't ya noticed what happens to the N2 during the terminationof a practice EOL, even at the hover?
Defence rests, yer honour.
I did mine at Alan Mann - expensive, but there was a reason for it. I can't recommend any schools up north, but I'd ensure you ask to be shown:
[list=1][*]Flight with limiting conditions (TOT, torque, and N1 if possible) - preferably also at MAUM or close to it.[*]Flight in an A model (severely TOT limited).[*]Crosswind / downwind operations when OGE and heavy. Beware gusts !![/list=1]
If you're switched on, converting across in 5 hours is not an issue.
And BTW, learn about the torque / TOT limits - not just temporary exceedances, but what exceeding the limits means for maintenance action.
[list=1][*]Flight with limiting conditions (TOT, torque, and N1 if possible) - preferably also at MAUM or close to it.[*]Flight in an A model (severely TOT limited).[*]Crosswind / downwind operations when OGE and heavy. Beware gusts !![/list=1]
If you're switched on, converting across in 5 hours is not an issue.
And BTW, learn about the torque / TOT limits - not just temporary exceedances, but what exceeding the limits means for maintenance action.
Jetranger crash Angola
Join Date: Aug 2003
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MGT
This one took some finding out but details are as follows:
Owner is a company called Inter Transit. They are in the construction and transportation business apparently.
The company has had the 206B for about 10 years.
My informants tell me it was an engine flame out but the landing caused damage and injuries.
Passengers included the Vice Minister for Public Works, his ex deputy and the ex minister for social integration.
Some have had to be flown to South Africa for treatment.
HH
This one took some finding out but details are as follows:
Owner is a company called Inter Transit. They are in the construction and transportation business apparently.
The company has had the 206B for about 10 years.
My informants tell me it was an engine flame out but the landing caused damage and injuries.
Passengers included the Vice Minister for Public Works, his ex deputy and the ex minister for social integration.
Some have had to be flown to South Africa for treatment.
HH
Join Date: Feb 2005
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As many have indicated, there is a possibility that there's a clutch related problem. The results of that can be quite nasty, so it's a good idea to confirm whether that is the case.
If it's not the case, it could be that the idle setting of the throttle is providing enough non-governed fuel to allow an unloaded freewheel to spin at N2=100%. If N2=NR then the clutch should engage so you wouldn't expect to see N2>NR (that's bad). If the rotor increases slightly, then N2 may be able to increase as well, but just to the N2 that is possible with an unloaded freewheel.
Because you said that the N2 will drop below 100% once it splits from the NR, then it seems that the rotor is driving the freewheel to an extent.
In any case, ensure the clutch is working properly.
As far as the 103% NR after a collective drop that Nick mentioned, I don't know the S76 system, but other governing systems that are not isochronous (maintain exactly 100%) will exhibit similiar behaviour. Rather than reacting immediately to small changes in NR or collective position by providing less fuel, a reduced power demand will cause the rotor to increase. Once the increase is large enough, then the fuel flow is altered.
Maintaining the NR slightly high following a reduced power demand has the benefit that if the power demand is soon increased, then the rotor only has to slow without changing the fuel flow again. This means that the engine runs at a constant power when there are quickly changing loads in the rotor. Or as Nick said, it improves the stability.
Of course, engine and rotor governing is much bigger than what I've mentioned, this is a simple explanation of why higher rotor speeds can result from collective lowerings in some systems. Experts, feel free to tear this apart.
Matthew.
If it's not the case, it could be that the idle setting of the throttle is providing enough non-governed fuel to allow an unloaded freewheel to spin at N2=100%. If N2=NR then the clutch should engage so you wouldn't expect to see N2>NR (that's bad). If the rotor increases slightly, then N2 may be able to increase as well, but just to the N2 that is possible with an unloaded freewheel.
Because you said that the N2 will drop below 100% once it splits from the NR, then it seems that the rotor is driving the freewheel to an extent.
In any case, ensure the clutch is working properly.
As far as the 103% NR after a collective drop that Nick mentioned, I don't know the S76 system, but other governing systems that are not isochronous (maintain exactly 100%) will exhibit similiar behaviour. Rather than reacting immediately to small changes in NR or collective position by providing less fuel, a reduced power demand will cause the rotor to increase. Once the increase is large enough, then the fuel flow is altered.
Maintaining the NR slightly high following a reduced power demand has the benefit that if the power demand is soon increased, then the rotor only has to slow without changing the fuel flow again. This means that the engine runs at a constant power when there are quickly changing loads in the rotor. Or as Nick said, it improves the stability.
Of course, engine and rotor governing is much bigger than what I've mentioned, this is a simple explanation of why higher rotor speeds can result from collective lowerings in some systems. Experts, feel free to tear this apart.
Matthew.