Sikorsky S-76: Ask Nick Lappos
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Yet another question for Nick - S76C+
In the non IIDS C+, when you touch the 'Test' sensor on the N1 indicator, without the engines running, it displays;
rANO
Looked in all the manuals I can get my hands on, but cannot find what the code is meant to indicate. Obviously the DECU engine gen is not turning so no corrected N1 is available, but what do the letters stand for? Got our engineering staff perplexed as well.
Ta
Geoff
rANO
Looked in all the manuals I can get my hands on, but cannot find what the code is meant to indicate. Obviously the DECU engine gen is not turning so no corrected N1 is available, but what do the letters stand for? Got our engineering staff perplexed as well.
Ta
Geoff
Last edited by Geoff Williams; 10th Jun 2005 at 09:40.
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Yes, Nigel, I have forgotten everything. Sitting in a G-V, with a glass of wine, reading The Wall Street Journal, I seem to see some poor sod in a rotory winged craft flogging slowly out to sea, several miles below. I lean forward, turn down the volume on the DVD movie set, and think, "There, but for the grace of God, go I!"
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check them wires!
Wow, round gage 76C+. That's a rare bird! You're part of a small group that knows what a DDR is...
Like most things on helicopters, the issue of displaying N1 in the 76C+ isn't a simple as it appears. In fact, the N1 you are looking at is a "corrected" N1, and not necessarily the exact N1 speed the engine is turning. It's due to the fact that Turbomeca rates their engines primarily on N1 speed and the precise rated (takeoff, 2min, 30sec) n1 speed is different for different ambient conditions (alt, temp).
So the kind Sikorsky engineeers, realizing you really didn't want to pull out a chart each time you set takeoff power, came up with a scheme for a "biased" or indicated N1. This allows you to memorize only one number for each rating. The mathematical correction is made in the DECU and sent (via ARINC) to the indicator. As a backup, the N1 indicator itself is also capable of calculating "Biased N1". It receives a raw N1 signal from the alternator, and oat from the ship's OAT. So what you're actually doing when conducting this test is confirming the gage calculated N1 is within tolerance to the DECU calculated value.
So with all that I STILL haven't answered your question! I don't have an exact answer for you right now, but will find the indicator spec and let you know. In the meantime, check all the inputs to the indicator for proper connections. Seems to me it's missing a necessary input to do its own calculation.
R. Cal
Like most things on helicopters, the issue of displaying N1 in the 76C+ isn't a simple as it appears. In fact, the N1 you are looking at is a "corrected" N1, and not necessarily the exact N1 speed the engine is turning. It's due to the fact that Turbomeca rates their engines primarily on N1 speed and the precise rated (takeoff, 2min, 30sec) n1 speed is different for different ambient conditions (alt, temp).
So the kind Sikorsky engineeers, realizing you really didn't want to pull out a chart each time you set takeoff power, came up with a scheme for a "biased" or indicated N1. This allows you to memorize only one number for each rating. The mathematical correction is made in the DECU and sent (via ARINC) to the indicator. As a backup, the N1 indicator itself is also capable of calculating "Biased N1". It receives a raw N1 signal from the alternator, and oat from the ship's OAT. So what you're actually doing when conducting this test is confirming the gage calculated N1 is within tolerance to the DECU calculated value.
So with all that I STILL haven't answered your question! I don't have an exact answer for you right now, but will find the indicator spec and let you know. In the meantime, check all the inputs to the indicator for proper connections. Seems to me it's missing a necessary input to do its own calculation.
R. Cal
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R. Cal
Thanks for your reply, but you might have missed in my description that the engines are off....so no N1 anyway. I am aware of the dual sensors on the phonic wheel and the frequency proportional signal from the DECU engine alternator all provide N1 signals. And when we are running, no problems, all indications are fine and the test shows the backup N1 signal is within 0.2. But curiosity was aroused when pressing the test with the engines off I got a code I can't find any info on.
rANO doesn't seem to fit any scenario I dream up??
Nothing in the 2S1 training manual either that I can find.
Geoff
Thanks for your reply, but you might have missed in my description that the engines are off....so no N1 anyway. I am aware of the dual sensors on the phonic wheel and the frequency proportional signal from the DECU engine alternator all provide N1 signals. And when we are running, no problems, all indications are fine and the test shows the backup N1 signal is within 0.2. But curiosity was aroused when pressing the test with the engines off I got a code I can't find any info on.
rANO doesn't seem to fit any scenario I dream up??
Nothing in the 2S1 training manual either that I can find.
Geoff
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Goeff, I will bug the Chief Pilot again. I suspect it is French for something the Taunting Knight said to Arthur, "You are brave little people who wipe other people's asses..." (Python fans out there, anyone?)
R. Cal, you are right, when we adapted the original Turbomeca to the A+, we test pilots were aghast that someone would actually allow the OEI limit to vary by each degree of OAT and foot of altitude, and expect that the pilot would use a look-up table while wrestling with a failed engine! The folks who make the gages were able to work with us to produce a small computation that always showed "corrected" N1 so that the limit number shown was always a constant, thus you had to memorize one number and it was valid for any ambient.
I am always struck that those who like the single limit calculator for the latest Super Puma don't mention this vast shortfall on another EC product!
R. Cal, you are right, when we adapted the original Turbomeca to the A+, we test pilots were aghast that someone would actually allow the OEI limit to vary by each degree of OAT and foot of altitude, and expect that the pilot would use a look-up table while wrestling with a failed engine! The folks who make the gages were able to work with us to produce a small computation that always showed "corrected" N1 so that the limit number shown was always a constant, thus you had to memorize one number and it was valid for any ambient.
I am always struck that those who like the single limit calculator for the latest Super Puma don't mention this vast shortfall on another EC product!
Avoid imitations
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I think it means "read Air Navigation Order".
You might as well, 'cos you are obviously bored silly being a hangar pilot with the engines switched off so you aren't going flying today.
You might as well, 'cos you are obviously bored silly being a hangar pilot with the engines switched off so you aren't going flying today.
"I am always struck that those who like the single limit calculator for the latest Super Puma don't mention this vast shortfall on another EC product!"
Nothing as crude as having to look at an N1 gauge in the latest ECF products. In the 155, with the arrial 2 series, you just pull to the stop for the power rating selected. May not even be N1 limited, but who cares? The computation is done for you!
On the 225 it's even better; YOU don't pull at all, it does it for you. The AP will pull to 96% Nr with the 2 minute rating selected, then fly you at the automatically calculated Vtoss (it knows the weight and ambient conditions). Very civilised!
Say what you like about the French, but don't knock their innovative and clever MMI (Man Machine Interface) concepts. For us in the pointy end, they have got it right
Nothing as crude as having to look at an N1 gauge in the latest ECF products. In the 155, with the arrial 2 series, you just pull to the stop for the power rating selected. May not even be N1 limited, but who cares? The computation is done for you!
On the 225 it's even better; YOU don't pull at all, it does it for you. The AP will pull to 96% Nr with the 2 minute rating selected, then fly you at the automatically calculated Vtoss (it knows the weight and ambient conditions). Very civilised!
Say what you like about the French, but don't knock their innovative and clever MMI (Man Machine Interface) concepts. For us in the pointy end, they have got it right
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Nick -
I reckon it aint French fo anytin. Them N1 gages are from the Lone Star State. Prolly some intelligent cryptic Texan message.
Nah, strike that. Texan and Intelligent don't belong in the same sentence...
R. Cal
(Z. Cal's tightwad brother)
I reckon it aint French fo anytin. Them N1 gages are from the Lone Star State. Prolly some intelligent cryptic Texan message.
Nah, strike that. Texan and Intelligent don't belong in the same sentence...
R. Cal
(Z. Cal's tightwad brother)
212man....These the same French that build the Airbus things that fly themselves despite what the pilot wants to do? Something about an airshow crash with passengers aboard as I recall.
Also...on the 155 one has to remember to put the lever down or hit a button at some point do you not....or burn up an engine?
Thinking of a situation where you are zinging along at warp speed at 7500 feet and one engine flames out......the aircraft senses the power demand for your flight condition...pours the dead dinosaurs into the combustion chamber.....and throws out all sorts of display pages at you. Then at some point the pilot is supposed to put down the cross word puzzle...and do something...since the one engine is pretty well humping to meet the demand?
Also...on the 155 one has to remember to put the lever down or hit a button at some point do you not....or burn up an engine?
Thinking of a situation where you are zinging along at warp speed at 7500 feet and one engine flames out......the aircraft senses the power demand for your flight condition...pours the dead dinosaurs into the combustion chamber.....and throws out all sorts of display pages at you. Then at some point the pilot is supposed to put down the cross word puzzle...and do something...since the one engine is pretty well humping to meet the demand?
SASless,
as for the Airbus it's the same as with any computer; garbage in, garbarge out!
Regarding the 155 and burning engines out, that's not a fair understanding of the situation. ANY aircraft having an engine failure will use the remaining engine to try and meet the power demand at the time of failure. If the demand is too great then, for engines with a 30 second rating, the 30 second rating will be required. This will still result in Nr decay unless either the pilot intervenes (if no outer loop modes coupled) or the AP lowers the lever (if outer loop modes coupled).
With the arrial 2 series, when it was in its relative infancy, there was no cumulative time available for the 30 second rating (same on the 76 C+; same engine) and it required a module 3/4 change (equals engine change for practical purposes). It was not BURNED OUT! the engine is now in a more mature state and TM have allowed cumulative consumption of the 30 second rating.
Having seen various FDR traces, I can tell you that the AP does a much better job of handling an engine failure, than the pilots, in these sorts of incidents. But then it's easy to be an armchair critic and no criticism is intended.
Don't knock it till you've tried it!!
as for the Airbus it's the same as with any computer; garbage in, garbarge out!
Regarding the 155 and burning engines out, that's not a fair understanding of the situation. ANY aircraft having an engine failure will use the remaining engine to try and meet the power demand at the time of failure. If the demand is too great then, for engines with a 30 second rating, the 30 second rating will be required. This will still result in Nr decay unless either the pilot intervenes (if no outer loop modes coupled) or the AP lowers the lever (if outer loop modes coupled).
With the arrial 2 series, when it was in its relative infancy, there was no cumulative time available for the 30 second rating (same on the 76 C+; same engine) and it required a module 3/4 change (equals engine change for practical purposes). It was not BURNED OUT! the engine is now in a more mature state and TM have allowed cumulative consumption of the 30 second rating.
Having seen various FDR traces, I can tell you that the AP does a much better job of handling an engine failure, than the pilots, in these sorts of incidents. But then it's easy to be an armchair critic and no criticism is intended.
Don't knock it till you've tried it!!
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212man and SASless,
The response to engine failure is often governed by the engine fuel control, which limits all paramenters to assure that the rotor droop occurrs, but that the engine is not harmed during that event. Thus the pilot has to use the lever to hold Nr properly, and all is right with the aircraft. With this engine limit protection scheme, no autopilot or pilot intervention is needed to assure protecting the engine, and the pilot does not have to fly using a combination of two gages, (the first limit gage and the Nr gage.) The fly away task is simply "make sure the rotor droops, and hold it to about a 2% droop." In other words, the engine limiter makes less workload than the first limit gage.
To rely on an autopilot to protect the engine is to have said "the job is too colplex for the pilot, so he must keep his hands off". This might be necessary at some time in the future, but is not needed now.
The response to engine failure is often governed by the engine fuel control, which limits all paramenters to assure that the rotor droop occurrs, but that the engine is not harmed during that event. Thus the pilot has to use the lever to hold Nr properly, and all is right with the aircraft. With this engine limit protection scheme, no autopilot or pilot intervention is needed to assure protecting the engine, and the pilot does not have to fly using a combination of two gages, (the first limit gage and the Nr gage.) The fly away task is simply "make sure the rotor droops, and hold it to about a 2% droop." In other words, the engine limiter makes less workload than the first limit gage.
To rely on an autopilot to protect the engine is to have said "the job is too colplex for the pilot, so he must keep his hands off". This might be necessary at some time in the future, but is not needed now.
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Ok, Shy Torque might be right. I am bored, been here since 1100 on a Sunday for a 1200 departure, its now gone 1500 and some of the pax still stuck in LOS I've been told. Going to be 1700 I bet before the job is on.
So went down and turned on the BAT. After the initial start sequence on the N1's with both usage lights and all digits showing '8' s, I covered the test cell to see
drNO for about 2 seconds then rANO.
Subsequent tests with the power still on gave the previous rANO.
Now here's a guess.
drNO might mean dDrNotOperating. Yes? The DECU was still going through its 10 second 'wake up' and it was during that time that this code was displayed.
Using some of the same lose logic, might rANO mean referenceAlternatorNotOperating.
Checked the 2S1 Maintenance Manual, zip.
Sprocket......nope, the ginger beers say there is no battery.
And yes, I agree with all you that are shouting.....get a life!
So went down and turned on the BAT. After the initial start sequence on the N1's with both usage lights and all digits showing '8' s, I covered the test cell to see
drNO for about 2 seconds then rANO.
Subsequent tests with the power still on gave the previous rANO.
Now here's a guess.
drNO might mean dDrNotOperating. Yes? The DECU was still going through its 10 second 'wake up' and it was during that time that this code was displayed.
Using some of the same lose logic, might rANO mean referenceAlternatorNotOperating.
Checked the 2S1 Maintenance Manual, zip.
Sprocket......nope, the ginger beers say there is no battery.
And yes, I agree with all you that are shouting.....get a life!
Nick,
I'm not sure what you are trying to say!
Firstly, when flying an a/c with an FLI, and an engine failure, the only thing you have to check is that you have the corect power rating selected (it defaults to 30 sec on failure of other engine, but you may need to select lower ratings), thereafter you just fly Nr. You do not refer to the FLI to check the power; it is simply telling you what the FADEC is doing. It is mischievous to imply you have to monitor two gauges!
Secondly, using the 30 second rating (on the 155 B) does not 'harm' the engine. It just requires a maintenance inspection, which in turn requires module 3/4 removal.
Thirdly, I fail to see how the 76 C+ can be any different in this regard; same engine! if the power demand at the point of failure is such that it is equal or greater than the 30 second power, the 30 second power will be used and this will result in the same inspection (unless the 2S1 now has cumulative usage, which the 2C1 does not). Obviously this will not apply to the 76 C++ and D, or the current 155 B1 (2S2, 2C2.)
I think the point about APs and engine failures is that in all probability they will do a more accurate job than the pilot, in the real world. Remember, that in most cases, a failure is a surprise to the crew and the subsequent handling will not be the same as a pre-briefed OPC/PPC or test flight, where the pilot will be poised with a hair trigger reaction, and a set of carefully recalled numbers in is head waiting to be applied.
It's a question of phillosophy; do we use automatics as some form of add on nicety, to be used from time to time, but fundamentally fly the a/c as we always have, or do we use them as the core operating function, with manual skills kept in practice to serve as the back up mode?
Sorry to divert the thread but I hate to see innacurate comment about some b***dy clever products!
PS. Geoff; get a life
I'm not sure what you are trying to say!
Firstly, when flying an a/c with an FLI, and an engine failure, the only thing you have to check is that you have the corect power rating selected (it defaults to 30 sec on failure of other engine, but you may need to select lower ratings), thereafter you just fly Nr. You do not refer to the FLI to check the power; it is simply telling you what the FADEC is doing. It is mischievous to imply you have to monitor two gauges!
Secondly, using the 30 second rating (on the 155 B) does not 'harm' the engine. It just requires a maintenance inspection, which in turn requires module 3/4 removal.
Thirdly, I fail to see how the 76 C+ can be any different in this regard; same engine! if the power demand at the point of failure is such that it is equal or greater than the 30 second power, the 30 second power will be used and this will result in the same inspection (unless the 2S1 now has cumulative usage, which the 2C1 does not). Obviously this will not apply to the 76 C++ and D, or the current 155 B1 (2S2, 2C2.)
I think the point about APs and engine failures is that in all probability they will do a more accurate job than the pilot, in the real world. Remember, that in most cases, a failure is a surprise to the crew and the subsequent handling will not be the same as a pre-briefed OPC/PPC or test flight, where the pilot will be poised with a hair trigger reaction, and a set of carefully recalled numbers in is head waiting to be applied.
It's a question of phillosophy; do we use automatics as some form of add on nicety, to be used from time to time, but fundamentally fly the a/c as we always have, or do we use them as the core operating function, with manual skills kept in practice to serve as the back up mode?
Sorry to divert the thread but I hate to see innacurate comment about some b***dy clever products!
PS. Geoff; get a life
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212Man,
Sounds like the two are flown the same way, using the engine limiter to control engine limits, and flying the Nr to keep workload down. That was not stated previously, you hung your hat on the first limit indicator and the autopilot! Sounds like they are all flown the same way, except the 350, which requires the pilot to look up a bunch of data on his kneeboard!
Yes you did steal the thread, when you defended the French by bringing up two other, irrelevant pieces of kit when we were talking about the 350. The 350 is still a bear to fly OEI, but I do concede, the other EC models are well governed!
Sounds like the two are flown the same way, using the engine limiter to control engine limits, and flying the Nr to keep workload down. That was not stated previously, you hung your hat on the first limit indicator and the autopilot! Sounds like they are all flown the same way, except the 350, which requires the pilot to look up a bunch of data on his kneeboard!
Yes you did steal the thread, when you defended the French by bringing up two other, irrelevant pieces of kit when we were talking about the 350. The 350 is still a bear to fly OEI, but I do concede, the other EC models are well governed!
Nick,
Re-reading your post I see you don't mention the 350 directly and I therefore thought you were bashing the 225 (latest Super Puma.)
'Steal' is a bit harsh, I thought 'divert' was about right!
Re-reading your post I see you don't mention the 350 directly and I therefore thought you were bashing the 225 (latest Super Puma.)
'Steal' is a bit harsh, I thought 'divert' was about right!