Bell 206: JetRanger and LongRanger
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Sounds like your swashplate friction is high. Have a mechanic ensure the breakaway friction settings are below the max limit.
Have the friction set to the lower end of the friction limit as the uniball can heat up and tighten when being used in flight.
Has the swashplate had new slider bearings put in recently?
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Have the friction set to the lower end of the friction limit as the uniball can heat up and tighten when being used in flight.
Has the swashplate had new slider bearings put in recently?
.
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Technically the swashplate outer ring will not tilt on the uniball during collective application, the whole assembly just slides up and down on the support (assuming fixed cyclic position).
You mention checking of the cyclic on the ground, what does the collective feel like on the ground?
You mention checking of the cyclic on the ground, what does the collective feel like on the ground?
Years ago in Iran...had a similar problem...was the slider ....but then it could be something else as well.
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Yes, if the slider bearings are old, corrosion can build up behind them and tighten up on to the support.
tcf: I dont have a 206 outside to look at, but there is some sort of coupling (either by friction or mechanical linkage) between the collective and cyclic. Lift up the collective lever (blades not turning) and the cyclic will move fwd or aft.
tcf: I dont have a 206 outside to look at, but there is some sort of coupling (either by friction or mechanical linkage) between the collective and cyclic. Lift up the collective lever (blades not turning) and the cyclic will move fwd or aft.
Last edited by sprocket; 26th Jun 2004 at 05:41.
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Sprocket,
You are correct, their is a mixing bellcrank at the base of the vertical tunnel (broom closet). I should have been more specific and said if you hold the cyclic still and raise the collective then does it only move up and down without tilting the uniball.
20kg of force seems like a tremendous amount of friction to build up. The suggestion of the slider bearings is a valid one, ceratinly worth checking but it does involve removing the swashplate.
Good luck
TCF
You are correct, their is a mixing bellcrank at the base of the vertical tunnel (broom closet). I should have been more specific and said if you hold the cyclic still and raise the collective then does it only move up and down without tilting the uniball.
20kg of force seems like a tremendous amount of friction to build up. The suggestion of the slider bearings is a valid one, ceratinly worth checking but it does involve removing the swashplate.
Good luck
TCF
As mere pilots, there's not a lot we can do to troubleshoot a problem with our aircraft. The best we can do is thoroughly explore what's happening and then describe that to the engineers who will then take the appropriate measures to correct it.
I'd start with a check of all controls with the frictions completely off and the aircraft shut down. First thing I'd wonder about: Is the collective friction really completely off? I've seen pilots twist the knob in the "off" direction so hard that the friction started to come back on. The first thing I would check is that the collective friction was not causing *any* binding.
Do the cyclic and collective move through their entire respective ranges with the same amont of force? I might even have an engineer remove the seats and seatpans to ensure that the collective linkage is not binding on anything (wire bundles, errant spanner, etc) between the stick and where the linkage goes into the broomcloset.
Once the aircraft is started and at *idle* (you know, around 62% N1), it won't hurt anything to momentarily lift the collective up a ways (you don't have to pull it *all* the way up but you could) as long as the cyclic is centered. You'll find out how the linkage feels with the hydraulics on. Are the forces constant? Now do your hydraulic checks by the book.
Take off and fly. When you start to feel the binding (I'm assuming from your original post that it is not constant), then fly at 60 kts. You can make fairly large control movements here without too much fear. So feel the cyclic servos. Remember the "X" pattern (left/front to right/rear and right/front to left/rear). Don't be jerky or abrupt, be smooth! But do move the cyclic enough to know that the servo is actually moving. Are either of them binding? (You probably don't want to do that with paying passengers onboard.)
If you're satisfied that the cyclic is okay and not part of the problem, then focus on the collective. You can make some big movements from whatever power is necessary to hold 60 kts to 100%Q (or limiting TOT, whichever) and down to flat pitch, then back up to max power. Is the force needed to move the collective different from when you were on the ground? Is the force needed constant? Does it change as you move it through certain areas?
Once these questions are answered, you can go to your engineers with an informed, informative discrepancy write-up.
I'd start with a check of all controls with the frictions completely off and the aircraft shut down. First thing I'd wonder about: Is the collective friction really completely off? I've seen pilots twist the knob in the "off" direction so hard that the friction started to come back on. The first thing I would check is that the collective friction was not causing *any* binding.
Do the cyclic and collective move through their entire respective ranges with the same amont of force? I might even have an engineer remove the seats and seatpans to ensure that the collective linkage is not binding on anything (wire bundles, errant spanner, etc) between the stick and where the linkage goes into the broomcloset.
Once the aircraft is started and at *idle* (you know, around 62% N1), it won't hurt anything to momentarily lift the collective up a ways (you don't have to pull it *all* the way up but you could) as long as the cyclic is centered. You'll find out how the linkage feels with the hydraulics on. Are the forces constant? Now do your hydraulic checks by the book.
Take off and fly. When you start to feel the binding (I'm assuming from your original post that it is not constant), then fly at 60 kts. You can make fairly large control movements here without too much fear. So feel the cyclic servos. Remember the "X" pattern (left/front to right/rear and right/front to left/rear). Don't be jerky or abrupt, be smooth! But do move the cyclic enough to know that the servo is actually moving. Are either of them binding? (You probably don't want to do that with paying passengers onboard.)
If you're satisfied that the cyclic is okay and not part of the problem, then focus on the collective. You can make some big movements from whatever power is necessary to hold 60 kts to 100%Q (or limiting TOT, whichever) and down to flat pitch, then back up to max power. Is the force needed to move the collective different from when you were on the ground? Is the force needed constant? Does it change as you move it through certain areas?
Once these questions are answered, you can go to your engineers with an informed, informative discrepancy write-up.
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Q for 206 guru's
Hey guys, situation, first flight of the day, reach 50% N1, does not accelerate, hung start, observe start times, close throttle, try again, 2nd start, lay a months money that this time it will work, always does on any of the 206's in the fleet.....I know that the hung start is usually lack of fuel in the combustion chamber, but can anyone shed some light on why that 2nd start, in my experience(hundreds of starts on the 206) always works the second time around?
Appreciate any information...
Regards,
Fatigue.
Appreciate any information...
Regards,
Fatigue.
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Fatigue,
How's the battery in the ship?...it may be like your namesake!! it may be a bit lazy?..make sure you have a good battery or ground power for the first start of the day if you can get it.
How's the battery in the ship?...it may be like your namesake!! it may be a bit lazy?..make sure you have a good battery or ground power for the first start of the day if you can get it.
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Fatigue,
Need more info.
Internal or external power?
Type of battery/s?
Bendix or CECO?
OAT?
N1 when throttle opened?
Any delay between throttle open and lightoff?
1st TOT peak and at what N1?
2nd TOT peak (if any) and and what N1?
Time to idle or hung point?
Fuel Nozzle maintenance practices?
All info helps.
Cheers
TCF
Need more info.
Internal or external power?
Type of battery/s?
Bendix or CECO?
OAT?
N1 when throttle opened?
Any delay between throttle open and lightoff?
1st TOT peak and at what N1?
2nd TOT peak (if any) and and what N1?
Time to idle or hung point?
Fuel Nozzle maintenance practices?
All info helps.
Cheers
TCF
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Internal or external power? We always use 28 V GPU for start
Type of battery/s? 24 V Sealed Lead Acid
Bendix or CECO? Bendix
OAT? Average 15-20 degrees C
N1 when throttle opened? 15%
Any delay between throttle open and lightoff? No!
1st TOT peak and at what N1? TOT Can't remember, N1 stopped at 50%
2nd TOT peak (if any) and and what N1? TOT can't remember, second start successful (as always)
Time to idle or hung point? Approx. 30 seconds
Fuel Nozzle maintenance practices? Will have to ask maintenance!
We have several 206's, and on the odd occasion, we have a hung start, the second start is always successful, and I am just intrigued as to the reason why. Many thanks, Fatigue
Type of battery/s? 24 V Sealed Lead Acid
Bendix or CECO? Bendix
OAT? Average 15-20 degrees C
N1 when throttle opened? 15%
Any delay between throttle open and lightoff? No!
1st TOT peak and at what N1? TOT Can't remember, N1 stopped at 50%
2nd TOT peak (if any) and and what N1? TOT can't remember, second start successful (as always)
Time to idle or hung point? Approx. 30 seconds
Fuel Nozzle maintenance practices? Will have to ask maintenance!
We have several 206's, and on the odd occasion, we have a hung start, the second start is always successful, and I am just intrigued as to the reason why. Many thanks, Fatigue
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I take it that this happens on a few of your 206 fleet, not just one troublesome machine (judging from your 1st post)? If so, that is intriguing.
When you say a 28V GPU do you mean a proper GPU or just some batteries hooked up together in a wheeled box?
Do you have the same problems if you start on internal batteries?
Can you note the 1st and 2nd peak N1/TOT figures next time you start one and let us know? In the Bendix FCU there are 2 adjustments that can alter these parameters so which ones to make, if required, rely on accurate reporting to the gingerbeers.
TCF
When you say a 28V GPU do you mean a proper GPU or just some batteries hooked up together in a wheeled box?
Do you have the same problems if you start on internal batteries?
Can you note the 1st and 2nd peak N1/TOT figures next time you start one and let us know? In the Bendix FCU there are 2 adjustments that can alter these parameters so which ones to make, if required, rely on accurate reporting to the gingerbeers.
TCF
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The Bendix system was never my favorite, I liked the Ceco system better, even if the Nr wandered around a bit more.
TCF has the correct thought process, check the temps and N1's on the 2 surges, it will tell you where the start "notch" is, and can be adjusted to provide more of an acceleration boost in the latter stages of the start.
A good 206 start is probably hotter and quicker than you'd imagine....I forget the Alison figures, but 825 C comes to mind. I may have that old memo at the office, I'll check tomorrow.
TCF has the correct thought process, check the temps and N1's on the 2 surges, it will tell you where the start "notch" is, and can be adjusted to provide more of an acceleration boost in the latter stages of the start.
A good 206 start is probably hotter and quicker than you'd imagine....I forget the Alison figures, but 825 C comes to mind. I may have that old memo at the office, I'll check tomorrow.
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PC Filter
Do you regularly comp wash the heli without either removing the PC line to the filter or shutting the line off with an AA comp wash kit??
If the PC filter is a bit grubby it can become restricted with a bit of moisture and the start will hang at 40-50%, but on the second try will start without a problem.
Get your engineer to clean the filter ultrasonicly and see if that fixes the problem.
TRACKDIRECT
If the PC filter is a bit grubby it can become restricted with a bit of moisture and the start will hang at 40-50%, but on the second try will start without a problem.
Get your engineer to clean the filter ultrasonicly and see if that fixes the problem.
TRACKDIRECT
It is an interesting peculiarity that some 206's will hang on the first attempt yet start fine on the second. I've got to go with "trackdirect"- it's most likely moisture in the PC filter or other air lines that gets dried out by the heat of the compressed air during the first start. In my experience, whenever the engine would hang on the first, I'd let it sit there for a few seconds (nothing protracted) just to make sure to get some heat into the components before making the second try.
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TCF
We use proper GPU,s and have around 28v indicated on the cockpit voltmeter,and yes it is no particular aircraft, never had a hung start using the battery yet but we rarely do them...will try to remember the figures next time....
407D.
Our aircraft start well below 825, 650-750 is the norm,800+ sometimes,....although I watch one peak at 920 the other day during some sort of maintenance...
Moisture sounds quite feesable as we start very early in the morning..
Thanks Gents for all your information..
Regards
Fatigue.
We use proper GPU,s and have around 28v indicated on the cockpit voltmeter,and yes it is no particular aircraft, never had a hung start using the battery yet but we rarely do them...will try to remember the figures next time....
407D.
Our aircraft start well below 825, 650-750 is the norm,800+ sometimes,....although I watch one peak at 920 the other day during some sort of maintenance...
Moisture sounds quite feesable as we start very early in the morning..
Thanks Gents for all your information..
Regards
Fatigue.
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Keep in mind that the Pc filter should be inspected and cleaned every 300 hours according to RR.
Filling it up with Compressor wash detergent if you dont disconnect the line or close it off with an AA kit will certainly prevent the engine accelerating but usually will continue with same fault until the detergent is cleaned out. I would be suprised if many engineers made that mistake too often.
All of these hung start problems are not normal and a systematic fault finding approach, starting with accurate ntoing/recording of start parameters, is the first step.
TCF
Filling it up with Compressor wash detergent if you dont disconnect the line or close it off with an AA kit will certainly prevent the engine accelerating but usually will continue with same fault until the detergent is cleaned out. I would be suprised if many engineers made that mistake too often.
All of these hung start problems are not normal and a systematic fault finding approach, starting with accurate ntoing/recording of start parameters, is the first step.
TCF
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Fatigue, those starts sound a bit cool for a 206. I was busy today, so never got to finding that old Alison article, may not have time tomorrow either, but I'd suggest a boost of start temp may be in order...perhaps not to solve the problem now, but to cause less stress on the engine. Slow cool starts are not good for a turbine.
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The documents that 407 is referring to are Allison (now Rolls) Commercial Service Letter's (CSL) # 1176 and # 1192 (for the C20 series).
The first one is titled Optimised Start technique for the C20. Without reciting the whole thing, of note is their definition of a good first start - "one taking less than 25 seconds form the introduction of fuel until the engine reaches ground idle". Overall a very interesting read.
#1192 is a 20 page effort about troubleshooting, with some excellent info.
Your maintenance people should have these in their tech library or contact Rolls themselves for copies.
The first one is titled Optimised Start technique for the C20. Without reciting the whole thing, of note is their definition of a good first start - "one taking less than 25 seconds form the introduction of fuel until the engine reaches ground idle". Overall a very interesting read.
#1192 is a 20 page effort about troubleshooting, with some excellent info.
Your maintenance people should have these in their tech library or contact Rolls themselves for copies.