AS350 cycles
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AS350 cycles
Someone has told me today that the cycle measurement of the AS350b2 is not only measure only by start-ups. So if you land the aircraft and takeoff without shutting it down, it still may count another cycle. The VEMD uses the variations of n1 or ng to measure it.
Is this correct?
Is this correct?
Older B2´s do not have VEMD but yes VEMD B2 & B3 calculates cycles.
You have Np & Ng cycles to log.
One Np = one flight
Ng is calculation depends on variations of combinations og max Ng & min Ng during one flight. Quite complicated to keep up with actually.
You have Np & Ng cycles to log.
One Np = one flight
Ng is calculation depends on variations of combinations og max Ng & min Ng during one flight. Quite complicated to keep up with actually.
Turbomeca makes it much more difficult than other engine manufacturers
All modern engines have complicated LCF counting and the "partial cycle" count has been with the Arriel Series since day one.
PW200 Series is similar.
Its up to you how you do it. If you can't work it out you have to take the most depleting and more basic method.
In earlier times this was an issue as most found when migrating from analog 350B2 to VEMD B2/B3 and found that there previous counting method may have been a little conservative.
Thankfully FADEC or electronically monitored engines are better at it than manual methods. In most cases you need to keep a manual paper log of the cycles in case the electronic memory is corrupted.
Discussed previously here.
"Just a pilot"
350 B2 VEMD cycles
There are 2 separate cycles to track (Nf and NG) and the VEMD has limitations.
Know that the end of flight cycle count display is cumulative. If the page is not displayed at shutdown, the VEMD continues to accumulate a grand total since the last display, ie if a flight total 1.05 cycles NG but the page is not displayed, those NG cycles will be added at the next display increasing it by that amount.
The VEMD activates the page when the NR drops below "X" RPM after whatever engine parameters activate it. If you turn the battery off before the page is displayed, see previous.
The B2 VEMD doesn't count NF cycles well at all. It also doesn't seem to count no-flights, the NG and NF don't change if you don't pull power.
"So if you land the aircraft and takeoff without shutting it down"...
Yes. No. Maybe. Sometimes. Never. My experience is that it will continue to more or less accurately count NG. If you keep the NF cycles above the cycle adjustment point (full throttle/NR) no adjustment to VEMD cycles required. Allow the NR to drop the first point, you have to adjust NF by adding .3 cycles and if it drops below the lower point, it's a whole cycle. I don't recall the VEMD adjusting this.
Know that the end of flight cycle count display is cumulative. If the page is not displayed at shutdown, the VEMD continues to accumulate a grand total since the last display, ie if a flight total 1.05 cycles NG but the page is not displayed, those NG cycles will be added at the next display increasing it by that amount.
The VEMD activates the page when the NR drops below "X" RPM after whatever engine parameters activate it. If you turn the battery off before the page is displayed, see previous.
The B2 VEMD doesn't count NF cycles well at all. It also doesn't seem to count no-flights, the NG and NF don't change if you don't pull power.
"So if you land the aircraft and takeoff without shutting it down"...
Yes. No. Maybe. Sometimes. Never. My experience is that it will continue to more or less accurately count NG. If you keep the NF cycles above the cycle adjustment point (full throttle/NR) no adjustment to VEMD cycles required. Allow the NR to drop the first point, you have to adjust NF by adding .3 cycles and if it drops below the lower point, it's a whole cycle. I don't recall the VEMD adjusting this.
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Yes. No. Maybe. Sometimes. Never. My experience is that it will continue to more or less accurately count NG. If you keep the NF cycles above the cycle adjustment point (full throttle/NR) no adjustment to VEMD cycles required. Allow the NR to drop the first point, you have to adjust NF by adding .3 cycles and if it drops below the lower point, it's a whole cycle. I don't recall the VEMD adjusting this.
This old chestnut yet again.
Here's the deal and why. Arriel 1B data used and models can differ.
Nf Cycle is 1 per Start, Takeoff, Shutdown. No flight No Cycle. No partial cycle count.
Example 1 - Start, Takeoff, Land, Shutdown.
Ng Cycle is the following -
Max Ng used for that particular flight taken from data. i.e Max Ng 97% = 0.7
Number of times Ng on that particular flight goes below 85% and back above = 0.05.
So for this flight Ng cycle is 0.7 plus 0 x 0.05 = 0.7
Nf cycle = 1.
Example 2 Start, Takeoff, Land 12 times (or whatever takes Ng below 85%), Shutdown.
Max Ng used for this particular flight taken from data. i.e Max Ng 97% = 0.7
Number of times Ng on that particular flight goes below 85% and back above - say 12 = 0.05 x 12 =0.6
So for this flight 0.7 plus 0.6 = 1.3
Now tell me if you can approach and get it on the ground to flat pitch without going below 85% Ng?
If you do not record the data you must use a more restrictive formula i.e. 1 for 1 which may not be applicable if you read the accident report.
If you do not have a recorder and don't record correctly you may get burned on cycles. You have the option to record partial cycles and who would't.
Option - fit a recorder. It was an option in some Tacho Boxes but rare unfortunately. VEMD users are OK. AKV is one aftermarket unit.
Why it is so -
For example and not limited to - the injection wheel makes up the gas generator rotating assembly and is a) subject to extreme heat, b) cooled by fuel passing through it.
It is the range of temperature which corresponds to Ng speed so they need to know a) how hot did it get? and b) how cool did it get?
This range of temperature and/or possibly speed relates to low cycle fatigue on the components.
Hope you can make sense of it.
Here's the deal and why. Arriel 1B data used and models can differ.
Nf Cycle is 1 per Start, Takeoff, Shutdown. No flight No Cycle. No partial cycle count.
Example 1 - Start, Takeoff, Land, Shutdown.
Ng Cycle is the following -
Max Ng used for that particular flight taken from data. i.e Max Ng 97% = 0.7
Number of times Ng on that particular flight goes below 85% and back above = 0.05.
So for this flight Ng cycle is 0.7 plus 0 x 0.05 = 0.7
Nf cycle = 1.
Example 2 Start, Takeoff, Land 12 times (or whatever takes Ng below 85%), Shutdown.
Max Ng used for this particular flight taken from data. i.e Max Ng 97% = 0.7
Number of times Ng on that particular flight goes below 85% and back above - say 12 = 0.05 x 12 =0.6
So for this flight 0.7 plus 0.6 = 1.3
Now tell me if you can approach and get it on the ground to flat pitch without going below 85% Ng?
If you do not record the data you must use a more restrictive formula i.e. 1 for 1 which may not be applicable if you read the accident report.
If you do not have a recorder and don't record correctly you may get burned on cycles. You have the option to record partial cycles and who would't.
Option - fit a recorder. It was an option in some Tacho Boxes but rare unfortunately. VEMD users are OK. AKV is one aftermarket unit.
Why it is so -
For example and not limited to - the injection wheel makes up the gas generator rotating assembly and is a) subject to extreme heat, b) cooled by fuel passing through it.
It is the range of temperature which corresponds to Ng speed so they need to know a) how hot did it get? and b) how cool did it get?
This range of temperature and/or possibly speed relates to low cycle fatigue on the components.
Hope you can make sense of it.
Yes. No. Maybe. Sometimes. Never. My experience is that it will continue to more or less accurately count NG
Be careful not to read to much into things. The VEMD I have only shows full cycles. So you may do 3 flights and see nothing changes until you accumulate 1 full cycle or more.
"Just a pilot"
RVDT posted:
"Can the VEMD display 100th of a cycle ie. 0.01? a 10th of a cycle i.e. 0.1? or only full cycles i.e. 1.0"
Depends on what specific cycles you're discussing. My experience is that the VEMD NG will display in 0.01 increments, for instance 0.93, 0.76, .88 NG cycles. I can't calculate to that fine interval, I use 0.05, 0.10, 0.15 K2 adjustments as trained, and if the VEMD approximates my mental calculation, I consider my account accurate and log initial calculation. The B2 VEMD is not considered authoritative according to my training, as it's derived from non-fadec data.
The B2 VEMD will only display NF cycles whole cycles, and doesn't accurately adjust for different RPM cycle K2.
On the subject of NG cycles, I believe the RFM allows 1.15 cycle entry for each start and flight event if used uniformly for all NG cycle entry. I don't use that method, so check your RFM...
"Can the VEMD display 100th of a cycle ie. 0.01? a 10th of a cycle i.e. 0.1? or only full cycles i.e. 1.0"
Depends on what specific cycles you're discussing. My experience is that the VEMD NG will display in 0.01 increments, for instance 0.93, 0.76, .88 NG cycles. I can't calculate to that fine interval, I use 0.05, 0.10, 0.15 K2 adjustments as trained, and if the VEMD approximates my mental calculation, I consider my account accurate and log initial calculation. The B2 VEMD is not considered authoritative according to my training, as it's derived from non-fadec data.
The B2 VEMD will only display NF cycles whole cycles, and doesn't accurately adjust for different RPM cycle K2.
On the subject of NG cycles, I believe the RFM allows 1.15 cycle entry for each start and flight event if used uniformly for all NG cycle entry. I don't use that method, so check your RFM...
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So is it the automatic cycle counting that makes people land their helicopter, leave it running at full revs, hop out, walk away and then wonder why it flys away by itself? 
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I found a document that explained it. I think I understand it now... It says that the maximum Ng value during the flight converts to a certain cycle value, so in your case 97% converts to 0.7 cycles. With 80% maximum Ng for example this would be 0.58 cycles. In the EC120 flight report below you see 0.87 cycles for the Ng. My guess is that 87% Ng translates to 0.87 cycles, but that is just a guess.
It seems that Nf goes in multitudes of 0.05 and not 1 as RVDT stated. But the question is what is done with that 0.05.
It seems that Nf goes in multitudes of 0.05 and not 1 as RVDT stated. But the question is what is done with that 0.05.
Last edited by LNRalph; 28th Aug 2018 at 19:58.
LNRalph,
My figures quoted were for AS350B which last time I looked has an Arriel engine fitted.
You are quoting info from an EC120 which has an Arrrius 1 fitted - chalk and cheese - different engine.
My figures quoted were for AS350B which last time I looked has an Arriel engine fitted.
You are quoting info from an EC120 which has an Arrrius 1 fitted - chalk and cheese - different engine.
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I was aware of that. I've seen a flight report from an AS350, which had decimals for the Nf as well. Maybe a different engine than the one you were referring to.
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Don't forget that there are also dynamic parts that are cycle limited in the AS350 (eg: mast, epicyclic carrier). These are limited by torque cycle, so one take off equals one TC, but also lifting of an external load is classed as a TC, so, during one "flight" the dynamics may log multiple cycles.
