AS350 Astar/Squirrel
A question for all 350 (B2) gurus:
NR adjustment is performed via WC 76-11-01, 5-1 (not 5-2 as EC discovered they made a typo... soon to be revised).
So, the document (NOTE) states:
WTF mate... what about autorotation adjustments?
So, the question being; is it really necessary to use another pickup sensor to adjust the anticipator for NR (being slightly high). What is the practice?
NR adjustment is performed via WC 76-11-01, 5-1 (not 5-2 as EC discovered they made a typo... soon to be revised).
So, the document (NOTE) states:
The display accuracy of the N.R. indicator on the
instrument panel is not enough to control and adjust
N.R. use the recommended equipment. If another
equipment item is used, check its measurement
accuracy at ± 1 rpm.
instrument panel is not enough to control and adjust
N.R. use the recommended equipment. If another
equipment item is used, check its measurement
accuracy at ± 1 rpm.
So, the question being; is it really necessary to use another pickup sensor to adjust the anticipator for NR (being slightly high). What is the practice?
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NR should be pretty straight forward as per the MM by adjusting the anticipator cable and autos using the collective rigging stop bolt. If you need to double check that the NR gauge is reading correctly you can try this first.
A- PURPOSE: TO PROVIDE TWO METHODS OF CHECKING THE
ACCURACY OF THE NR-NG-NP INDICATION USING A 80 SERIES
FLUKE METER.
METHOD 1
1- PERMENANTLY SPLICE INTO THE INDICATOR WIRES BEHIND THE
DASH AS SHOWN ON THE ATTACHED DRAWING.
2- MOUNT TEST LEAD BRACKETS USING AMP TEST JACKS
AMP P/N 164-401R & 164-401B (red and black test jacks )
OR METHOD 2
3- DISCONNECT THE INDICATOR PLUG AND CONNECT THE FLUKE
METER INTO THE APPROPRIATE PINS.
4- RUN FLAT PITCH ON THE GROUND, PLUG IN THE FLUKE METER AND
READ THE FREQUENCY OF THE NR AND NG
5-USING THE ATTACHED FORMULA, DETERMINE THE NR AND NG SPEEDS
SEE ARRIEL 1D1 SERVICE LETTER (1840 / 98 / ARID / 43 )
6- TO CHECK THE FUEL CONTROL STATIC DROOP ON THE GROUND
PLOT THE NR-NG SPEEDS ON THE STATIC DROOP CHART PER THE
ENGINE MM CHAPT.73
7- TO CHECK THE NR AND NG SPEED ACCURACY IN FLIGHT,CRUISE
AT APPROX. 97% NG (B.V.CLOSED) AND TAKE THE HERTZ READINGS
AND USE THE ATTACHED FORMMULA
NR=FREQ.IN HERTZ X 2.5 = NR SPEED
NG= FREQ. IN HERTZ DIVIDED BY 140.017 X 100 = % NG
NP = FREQ. IN HERTZ DIVIDED BY 70.267 X 100 = % NP
A- PURPOSE: TO PROVIDE TWO METHODS OF CHECKING THE
ACCURACY OF THE NR-NG-NP INDICATION USING A 80 SERIES
FLUKE METER.
METHOD 1
1- PERMENANTLY SPLICE INTO THE INDICATOR WIRES BEHIND THE
DASH AS SHOWN ON THE ATTACHED DRAWING.
2- MOUNT TEST LEAD BRACKETS USING AMP TEST JACKS
AMP P/N 164-401R & 164-401B (red and black test jacks )
OR METHOD 2
3- DISCONNECT THE INDICATOR PLUG AND CONNECT THE FLUKE
METER INTO THE APPROPRIATE PINS.
4- RUN FLAT PITCH ON THE GROUND, PLUG IN THE FLUKE METER AND
READ THE FREQUENCY OF THE NR AND NG
5-USING THE ATTACHED FORMULA, DETERMINE THE NR AND NG SPEEDS
SEE ARRIEL 1D1 SERVICE LETTER (1840 / 98 / ARID / 43 )
6- TO CHECK THE FUEL CONTROL STATIC DROOP ON THE GROUND
PLOT THE NR-NG SPEEDS ON THE STATIC DROOP CHART PER THE
ENGINE MM CHAPT.73
7- TO CHECK THE NR AND NG SPEED ACCURACY IN FLIGHT,CRUISE
AT APPROX. 97% NG (B.V.CLOSED) AND TAKE THE HERTZ READINGS
AND USE THE ATTACHED FORMMULA
NR=FREQ.IN HERTZ X 2.5 = NR SPEED
NG= FREQ. IN HERTZ DIVIDED BY 140.017 X 100 = % NG
NP = FREQ. IN HERTZ DIVIDED BY 70.267 X 100 = % NP
NR Adjustment
The Arriel 1 has a "design feature" that causes the RPM to vary with fuel temperature.
As the RPM drifts off all the vibration absorbers fitted to the head and under the floor then go out of tune.
As stated the NR Tachometer cannot be interpreted accurately enough and can be adjusted to suit.
Various methods can be used to use to measure the RPM via a simple break out harness. For example the MicroVib balancer has a page where you can input the frequency value that equates to 100% and/or an RPM value.
It is important that it is checked in flight at or about MCP in the cruise. The RPM is different between models.
Keeping the RPM in the correct range is probably the most important thing you can do to keep your aircraft smooth and should be checked regularly and before any other adjustments are made.
355 F's with pneumatic governor controls can be anyones guess as the RPM drifts with barometric conditions although there are aftermarket kits to improve this.
As the RPM drifts off all the vibration absorbers fitted to the head and under the floor then go out of tune.
As stated the NR Tachometer cannot be interpreted accurately enough and can be adjusted to suit.
Various methods can be used to use to measure the RPM via a simple break out harness. For example the MicroVib balancer has a page where you can input the frequency value that equates to 100% and/or an RPM value.
It is important that it is checked in flight at or about MCP in the cruise. The RPM is different between models.
Keeping the RPM in the correct range is probably the most important thing you can do to keep your aircraft smooth and should be checked regularly and before any other adjustments are made.
355 F's with pneumatic governor controls can be anyones guess as the RPM drifts with barometric conditions although there are aftermarket kits to improve this.
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Engineer's perspective
I am not a pilot, but I can give you an engineer's perspective of the FX2 conversion.
The Turbomeca Arriel 1D1 in the AS350B2 has a MCP rating of 625 SHP. The LTS101-700D-2 has a MCP rating of 650 SHP.
In the SD2 conversion, the FAA required Soloy to only allow the LTS101 to produce as much MCP power as the AS350B2 was originally certified with, so 625 SHP.
However, the FX2 conversion was allowed to take advantage of the full LTS101 MCP rating of 650 SHP, 4% more power. If you look at the Helilynx 350 FX2 website, on the right are links to their FX2 HOGE and HIGE charts. You will be able to see the benefit in gross weight the FX2 conversion has over the AS350B2.
Hope this helps.
The Turbomeca Arriel 1D1 in the AS350B2 has a MCP rating of 625 SHP. The LTS101-700D-2 has a MCP rating of 650 SHP.
In the SD2 conversion, the FAA required Soloy to only allow the LTS101 to produce as much MCP power as the AS350B2 was originally certified with, so 625 SHP.
However, the FX2 conversion was allowed to take advantage of the full LTS101 MCP rating of 650 SHP, 4% more power. If you look at the Helilynx 350 FX2 website, on the right are links to their FX2 HOGE and HIGE charts. You will be able to see the benefit in gross weight the FX2 conversion has over the AS350B2.
Hope this helps.
Having time to spare the other day, I was reading through 350's FLM. Being used to Bells and german side of EC's I was amazed at 350's rate of climb performance charts. Two charts, one for corrected weight and the other for rate of climb.
Why the corrected weight chart and what is the catch behind it?
Why the corrected weight chart and what is the catch behind it?
corrected weight
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AS350 BA
(b) Free turbine
The number C2 of reference cycles consumed between one start and the consecutive shutdown is calculated as follows:
C2 = F1 + ∑F2
F1: Complete cycle to the value of 1
F2: Partial cycle (power decrease followed up by a return to nominal rating), related to all the values reached less than or equal to 85%
The value of F2 is counted as follows: after exceeding a minimum value of 98%
When N2 decreases and reaches a value between 85% and 70% then rises above 98%
F2 = 0.1 (engine PRE-MOD TU77)
F2 = 0.3 (engine POST_MOD TU77)
When N2 decreases and reaches a value less than 70%, then rises above 98%: F2=1
NOTE this notably concerns the procedure that exists on some aircraft to lock the rotor while keeping the engine in operation (at ground idle), in order to get on board and get off passengers.
The number C2 of reference cycles consumed between one start and the consecutive shutdown is calculated as follows:
C2 = F1 + ∑F2
F1: Complete cycle to the value of 1
F2: Partial cycle (power decrease followed up by a return to nominal rating), related to all the values reached less than or equal to 85%
The value of F2 is counted as follows: after exceeding a minimum value of 98%
When N2 decreases and reaches a value between 85% and 70% then rises above 98%
F2 = 0.1 (engine PRE-MOD TU77)
F2 = 0.3 (engine POST_MOD TU77)
When N2 decreases and reaches a value less than 70%, then rises above 98%: F2=1
NOTE this notably concerns the procedure that exists on some aircraft to lock the rotor while keeping the engine in operation (at ground idle), in order to get on board and get off passengers.
Can anyone please tell me what they are referring to with N2?
or does N2=Ng gauge
as they don't refer to an N2 anywhere except in the above!
I thought it might be (Rotor tacho = Nr) but then the figures don't line up?:
Thanks in advance.
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N2=Nf=free turbine
N1=Ng=gas generator turbine
NR is rotor rpm measured on the MRH mast and no concern of turbomecas other than under normal circumstances NR is a function of N2/Nf.
N1=Ng=gas generator turbine
NR is rotor rpm measured on the MRH mast and no concern of turbomecas other than under normal circumstances NR is a function of N2/Nf.
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AS350BA
Thanks for the info, and that is what i though.
Now how do I measure the N2 free turbine speed? I thought that was directly related to rotor rpm, so read from the rotor tacho, and once you go to full throttle the free turbine or (power turbine is it?)and rotor speed matched/stayed constant together around 395 Rrpm, and only the NG changed its rpm due to power requirements’
ie: less power (collective setting, low torque) less NG rpm and
more power (raising the collective, more torque) more NG rpm, but the free turbine basically stayed the same I know it can move a little.
Please remember I’m trying to understand how to calculate the NF or NP or C2 cycles I think?
I understand the NG or C1 cycles I hope! as they are all measured from the NG gauge and have been explained earler in this thread (around pg6) but understanding the F2 Partial cycle has me beat at the moment.
Cheers.
Now how do I measure the N2 free turbine speed? I thought that was directly related to rotor rpm, so read from the rotor tacho, and once you go to full throttle the free turbine or (power turbine is it?)and rotor speed matched/stayed constant together around 395 Rrpm, and only the NG changed its rpm due to power requirements’
ie: less power (collective setting, low torque) less NG rpm and
more power (raising the collective, more torque) more NG rpm, but the free turbine basically stayed the same I know it can move a little.
Please remember I’m trying to understand how to calculate the NF or NP or C2 cycles I think?
I understand the NG or C1 cycles I hope! as they are all measured from the NG gauge and have been explained earler in this thread (around pg6) but understanding the F2 Partial cycle has me beat at the moment.
Cheers.
Last edited by EZY AIR; 19th Feb 2012 at 00:13. Reason: adding info
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On your NR gauge you have the needle for NR and the triangle(if I remember correctly for the B2) for Nf/N2. So yes they normally run together except during auto's, certain failures etc but you can look at the triangle to see where your Nf/N2 is. If you have a BA or a B you might not have the triangle then you will have to use NR as your guide.
AS350/5 Cabin Structure
Given the apparent susceptibility of the AS350/5's cabin to 'falling off' at the slightest provocation (okay, well some provocation) and given that they are still being produced .. wouldn't it be possible for our friends in Marignane to install a couple of roof spars extending say from the engine deck (where perhaps the spar could be mounted) forward into the fabric (or underside) of the cabin roof and in the general vicinity depicted by the yellow stripe in the image below?
Proposed cabin strengthening (both sides) within the vicinity depicted by the yellow stripe
Proposed cabin strengthening (both sides) within the vicinity depicted by the yellow stripe
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AS350BA cycles
Thanks VP, but I’m still looking for the answer for the free turbine cycles?
They state
(b) Free turbine
C2 = F1 + ∑F2
F1: Complete cycle to the value of 1
F2: Partial cycle (power decrease followed up by a return to nominal rating), related to all the values reached less than or equal to 85%
When N2 decreases and reaches a value between 85% and 70% then rises above 98%
They use the name N2 but the values they state sound like N1 values not Rotor gauge!
This is surely not the Rotor gauge they are referring to?? Or is it!!
Also F1: Complete cycle to the value of 1 Does that mean that F1 can be less than 1 for a start??
Thanks again.
They state
(b) Free turbine
C2 = F1 + ∑F2
F1: Complete cycle to the value of 1
F2: Partial cycle (power decrease followed up by a return to nominal rating), related to all the values reached less than or equal to 85%
When N2 decreases and reaches a value between 85% and 70% then rises above 98%
They use the name N2 but the values they state sound like N1 values not Rotor gauge!
This is surely not the Rotor gauge they are referring to?? Or is it!!
Also F1: Complete cycle to the value of 1 Does that mean that F1 can be less than 1 for a start??
Thanks again.
Ezy Air,
All this was discussed on Page 6 of this thread, from post 111: way back in 2003!
To answer your main question, yes the N2 referenced is your Ng. PITA to come back from a sling load or similar sortie and try to guess how many times you've decreased power to <85%Ng, or above 98%Ng and then factor the 0.1 or 0.3 cycle count! Really, who is watching the Ng that closely when your head is outside flying? Then there is <70%Ng and back above 98%Ng for a complete cycle instead of the .1 or .3. Again, if you are bottoming the lever to attain those figures then you've more on your mind than watching the Ng gauge
Re your second question, the start cycles will be factors of 1. What else could they be?
Forget the Nr, it is irrelevant to the Arriel cycle count.
All this was discussed on Page 6 of this thread, from post 111: way back in 2003!
To answer your main question, yes the N2 referenced is your Ng. PITA to come back from a sling load or similar sortie and try to guess how many times you've decreased power to <85%Ng, or above 98%Ng and then factor the 0.1 or 0.3 cycle count! Really, who is watching the Ng that closely when your head is outside flying? Then there is <70%Ng and back above 98%Ng for a complete cycle instead of the .1 or .3. Again, if you are bottoming the lever to attain those figures then you've more on your mind than watching the Ng gauge
Re your second question, the start cycles will be factors of 1. What else could they be?
Forget the Nr, it is irrelevant to the Arriel cycle count.
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Ezy Air,
All this was discussed on Page 6 of this thread, from post 111: way back in 2003!
No it was not, the information there is all about the NG cycles or C1 or N1 whatever you call them. I’m after the Np or Nf or C2 cycles I never once asked for the NG cycles as I can understand how to work them out.
To answer your main question, yes the N2 referenced is your Ng. PITA to come back from a sling load or similar sortie and try to guess how many times you've decreased power to <85%Ng, or above 98%Ng and then factor the 0.1 or 0.3 cycle count! Really, who is watching the Ng that closely when your head is outside flying?
Well with an AS350 BA you would know that to get an NG under 85% you have to have the collective on the bottom stop and some will not go below 85%NG even then, so almost no need to look at the gauge then! But I bet if that’s where the collective was then you might just have your head up! and well Max power pulled each time you pull lots I said Lots of power you’re kidding me, you don’t look at that, you only need the max power pulled for the total flight, twenty take-offs what was the max power pulled? That is not too hard to remember for me anyway.
Then there is <70%Ng and back above 98%Ng for a complete cycle instead of the .1 or .3. Again, if you are bottoming the lever to attain those figures then you've more on your mind than watching the Ng gauge yep have to land and pull the throttle back for that one so it’s easy don’t retard the NG below 71% piece of piss.
Re your second question, the start cycles will be factors of 1. What else could they be? 0.6, 0.7 0.8 but not 0.85 maybe?? That’s why I’m asking!! With words like to the value of 1 from the French translated to English something could be lost!
So am I using the Ng gauge for the F2 partial cycle for the Np logging formula?
All this was discussed on Page 6 of this thread, from post 111: way back in 2003!
No it was not, the information there is all about the NG cycles or C1 or N1 whatever you call them. I’m after the Np or Nf or C2 cycles I never once asked for the NG cycles as I can understand how to work them out.
To answer your main question, yes the N2 referenced is your Ng. PITA to come back from a sling load or similar sortie and try to guess how many times you've decreased power to <85%Ng, or above 98%Ng and then factor the 0.1 or 0.3 cycle count! Really, who is watching the Ng that closely when your head is outside flying?
Well with an AS350 BA you would know that to get an NG under 85% you have to have the collective on the bottom stop and some will not go below 85%NG even then, so almost no need to look at the gauge then! But I bet if that’s where the collective was then you might just have your head up! and well Max power pulled each time you pull lots I said Lots of power you’re kidding me, you don’t look at that, you only need the max power pulled for the total flight, twenty take-offs what was the max power pulled? That is not too hard to remember for me anyway.
Then there is <70%Ng and back above 98%Ng for a complete cycle instead of the .1 or .3. Again, if you are bottoming the lever to attain those figures then you've more on your mind than watching the Ng gauge yep have to land and pull the throttle back for that one so it’s easy don’t retard the NG below 71% piece of piss.
Re your second question, the start cycles will be factors of 1. What else could they be? 0.6, 0.7 0.8 but not 0.85 maybe?? That’s why I’m asking!! With words like to the value of 1 from the French translated to English something could be lost!
So am I using the Ng gauge for the F2 partial cycle for the Np logging formula?
To quote page 6
Those of us that can read will have noticed
Which obviously means as well - NO Flight = NO Cycle.
Ezy Air,
You may understand "how" to work out the Ng cycles but here is the "why".
The design of the Arriel and some other TM engines involves a unique feature called the "injection wheel". This wheel is an integral part of the rotating assembly of the Gas Generator. It is subject to some fairly severe low cycle fatigue as it has the added issue of relatively cold fuel flowing through it and combustion occurring very close by and it links the gas generator turbine to the compressor so probably has about ~ 4-5 thousand horsepower going through it. The fuel and Ng speed are linked so the range of Ng is directly related to the temperature cycle and speed cycle that the injection wheel and other LCF affected components are subjected to.
The injection wheel probably has the lowest "cycle life" of all the rotating components.
Low Cycle Fatigue is real as some have found to their detriment. The partial cycle count was never an issue with this engine until someone found out the hard way.
(I) REFERENCE CYCLE (Ng): Theoretical cycle used a reference for setting service life limits. Includes one start, one power acceleration corresponding to the "takeoff power" and one shutdown.
(ii) OPERATING CYCLES: A flight may consist of two types of cycles:
- Complete Cycle: An engine operating sequence including one start, one power acceleration and one shutdown.
- Partial Cycle: An engine operating sequence corresponding to a power decrease followed by a significant increase without engine shutdown. It may be defined as the number of hover events and landings.
(iii) Free Turbine: All components. One flight = One cycle
Gas Generator Equation: N = K1 + (n x K2)
K1 = Coefficient corresponding to maximum Ng (see table over page)
K2 = Coefficient corresponding to minimum Ng (see table over page)
n = Number of partial cycles carried out between start and shutdown
(ii) OPERATING CYCLES: A flight may consist of two types of cycles:
- Complete Cycle: An engine operating sequence including one start, one power acceleration and one shutdown.
- Partial Cycle: An engine operating sequence corresponding to a power decrease followed by a significant increase without engine shutdown. It may be defined as the number of hover events and landings.
(iii) Free Turbine: All components. One flight = One cycle
Gas Generator Equation: N = K1 + (n x K2)
K1 = Coefficient corresponding to maximum Ng (see table over page)
K2 = Coefficient corresponding to minimum Ng (see table over page)
n = Number of partial cycles carried out between start and shutdown
(iii) Free Turbine: All components. One flight = One cycle
Ezy Air,
You may understand "how" to work out the Ng cycles but here is the "why".
The design of the Arriel and some other TM engines involves a unique feature called the "injection wheel". This wheel is an integral part of the rotating assembly of the Gas Generator. It is subject to some fairly severe low cycle fatigue as it has the added issue of relatively cold fuel flowing through it and combustion occurring very close by and it links the gas generator turbine to the compressor so probably has about ~ 4-5 thousand horsepower going through it. The fuel and Ng speed are linked so the range of Ng is directly related to the temperature cycle and speed cycle that the injection wheel and other LCF affected components are subjected to.
The injection wheel probably has the lowest "cycle life" of all the rotating components.
Low Cycle Fatigue is real as some have found to their detriment. The partial cycle count was never an issue with this engine until someone found out the hard way.