Sikorsky S-76 [Archive Copy]
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How about just answering the poor lad's question
Here's the answer. (We had a similar situation in the test 76C++ last year, so I had looked it up)
When Test switch (Initiated Test) is touched, if the DECU ARINC is not being received the digital display will read "ArNO", if the DDR data is not being received the digital display will read "drNO", and if the Raw N1 signal is not being received the display will read "rANO".
As you observed, it takes a bit for the DDR & DECU to start sending their outputs. Until then, you'll get the appropriate error message.
Good Luck.
Hoss
When Test switch (Initiated Test) is touched, if the DECU ARINC is not being received the digital display will read "ArNO", if the DDR data is not being received the digital display will read "drNO", and if the Raw N1 signal is not being received the display will read "rANO".
As you observed, it takes a bit for the DDR & DECU to start sending their outputs. Until then, you'll get the appropriate error message.
Good Luck.
Hoss
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It helps when you have an "inside connection" !
I got it from the N1 indicator specification document. You'd be hard pressed to find it anywhere other than the Sikorsky factory.
See ya,
HO5S
I got it from the N1 indicator specification document. You'd be hard pressed to find it anywhere other than the Sikorsky factory.
See ya,
HO5S
Just an update:
We fitted the Ryan 9900 BX TCAS, with its stand-alone indicator and voice alert system with mute and refresh button on the collective. Provisions for future expansion for lightning alert and EGPWS.
Absolutely marvellous, and the altitude alert functions and approach modes work like a charm. They would want to, coming with a price tag over $55,000. But a lot cheaper than bumping into somebody.
Heck of a time finding somewhere to put it on the dash. Eventually had to toss the ancient Garmin 165 and shuffle a few dials around. Still got two other GPS to help me not get lost, so the 165 can be a spare for the Huey.
We fitted the Ryan 9900 BX TCAS, with its stand-alone indicator and voice alert system with mute and refresh button on the collective. Provisions for future expansion for lightning alert and EGPWS.
Absolutely marvellous, and the altitude alert functions and approach modes work like a charm. They would want to, coming with a price tag over $55,000. But a lot cheaper than bumping into somebody.
Heck of a time finding somewhere to put it on the dash. Eventually had to toss the ancient Garmin 165 and shuffle a few dials around. Still got two other GPS to help me not get lost, so the 165 can be a spare for the Huey.
Ascend, for information, TCAS 2 is not compatible with helicopters as they do not have the performance to follow its instructions.
Skywatch seems to be a popular choice.
Skywatch seems to be a popular choice.
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Jez,
Yes TCAS depends on both aircraft squaking on transponders, it uses the answerback for range, and uses an antenna array to get bearing.
IMHO, it works fantastically, and is very valuable.
Yes TCAS depends on both aircraft squaking on transponders, it uses the answerback for range, and uses an antenna array to get bearing.
IMHO, it works fantastically, and is very valuable.
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S-76 Fleet Exceeds Four Million Flight Hours
S-76 Fleet Exceeds Four Million Flight Hours
Wednesday July 27, 9:12 am ET
STRATFORD, Conn., July 27 /PRNewswire-FirstCall/ -- Sikorsky Aircraft is pleased to announce that its S-76 fleet has accumulated more than four million total flight hours.
This achievement was made possible by the over 220 operators currently flying close to 600 aircraft in 59 countries around the world.
"The S-76 is a versatile product capable of flying anywhere, under difficult conditions, with unmatched range and speed. Its success has been built by meeting the needs of our customers throughout the S-76's long and distinguished tenure," said Jeff Pino, Sikorsky's Senior Vice President of Marketing and Commercial programs.
Pino said further that, "Hitting four million flight hours attests to the S-76's status as the preferred choice for hundreds of commercial operators around the world. It combines total reliability, comfort and safety."
Even legacies leave room for improvement however, which prompted Sikorsky to announce in February 2005 a series of engine, air vehicle, interior and avionics upgrades available for order immediately on the new S-76C++(TM) helicopter and a set of additional product improvements that will lead to the launch of the new S-76D(TM) model in 2008.
The extensive product upgrades ensure that the S-76C++ and the future S- 76D will remain best-in-class in the corporate VIP, offshore oil, airline, EMS/ search-and-rescue and law enforcement segments.
Product improvements available immediately on the S-76C++ include: a Turbomeca Arriel 2S2 engine upgrade, a new VIP interior, a new health and usage monitoring system (HUMS), and the implementation of new quiet zone technology(TM) which will enable significant interior noise level reductions without weight penalty.
The S-76D will build upon the upgrades slated immediately for the C++ by offering additional product improvements to include: a new composite main rotor blade, a new quiet tail rotor, a rotorcraft icing protection system (RIPS) that will provide the ability to launch into known icing conditions, a new cockpit with an integrated avionics system designed to the latest FAA/JAA requirements, and a new Pratt & Whitney Canada PW210 engine.
These product improvements will ensure a bright future for the S-76, one that builds on its strong legacy and holds true to its mission to fly anywhere and perform any mission at anytime.
Sikorsky Aircraft Corporation, based in Stratford, Conn., is a world leader in helicopter design, manufacturing and service. Sikorsky is a subsidiary of United Technologies Corporation (NYSE: UTX - News), of Hartford, Conn., which provides a broad range of high-technology products and support services to the aerospace and building systems industries.
Wednesday July 27, 9:12 am ET
STRATFORD, Conn., July 27 /PRNewswire-FirstCall/ -- Sikorsky Aircraft is pleased to announce that its S-76 fleet has accumulated more than four million total flight hours.
This achievement was made possible by the over 220 operators currently flying close to 600 aircraft in 59 countries around the world.
"The S-76 is a versatile product capable of flying anywhere, under difficult conditions, with unmatched range and speed. Its success has been built by meeting the needs of our customers throughout the S-76's long and distinguished tenure," said Jeff Pino, Sikorsky's Senior Vice President of Marketing and Commercial programs.
Pino said further that, "Hitting four million flight hours attests to the S-76's status as the preferred choice for hundreds of commercial operators around the world. It combines total reliability, comfort and safety."
Even legacies leave room for improvement however, which prompted Sikorsky to announce in February 2005 a series of engine, air vehicle, interior and avionics upgrades available for order immediately on the new S-76C++(TM) helicopter and a set of additional product improvements that will lead to the launch of the new S-76D(TM) model in 2008.
The extensive product upgrades ensure that the S-76C++ and the future S- 76D will remain best-in-class in the corporate VIP, offshore oil, airline, EMS/ search-and-rescue and law enforcement segments.
Product improvements available immediately on the S-76C++ include: a Turbomeca Arriel 2S2 engine upgrade, a new VIP interior, a new health and usage monitoring system (HUMS), and the implementation of new quiet zone technology(TM) which will enable significant interior noise level reductions without weight penalty.
The S-76D will build upon the upgrades slated immediately for the C++ by offering additional product improvements to include: a new composite main rotor blade, a new quiet tail rotor, a rotorcraft icing protection system (RIPS) that will provide the ability to launch into known icing conditions, a new cockpit with an integrated avionics system designed to the latest FAA/JAA requirements, and a new Pratt & Whitney Canada PW210 engine.
These product improvements will ensure a bright future for the S-76, one that builds on its strong legacy and holds true to its mission to fly anywhere and perform any mission at anytime.
Sikorsky Aircraft Corporation, based in Stratford, Conn., is a world leader in helicopter design, manufacturing and service. Sikorsky is a subsidiary of United Technologies Corporation (NYSE: UTX - News), of Hartford, Conn., which provides a broad range of high-technology products and support services to the aerospace and building systems industries.
S76 OEI N2/Nr Droop
Hi all,
With reference to the S76, fitted with Arriel engines, no DECU/FADEC etc:
Two engine N2/Nr is set at 107%. If one engine's power is removed, and with the remaining engine within limits, it seems to droop and stabilise at around 104-105%.
Each engine doesn't know whether the other one is functioning or not, so I view the loss of one engines power simply as an increased demand of the other one providing power, similar to raising the collective in a single.
My understanding is that if you ask an engine to deliver 107% N2/Nr, the engine will do everything it can to give you that, including maximum fuel flow (N1 topping) if need be.
I can't quite seem to get my head around why this droop happens.
With reference to the S76, fitted with Arriel engines, no DECU/FADEC etc:
Two engine N2/Nr is set at 107%. If one engine's power is removed, and with the remaining engine within limits, it seems to droop and stabilise at around 104-105%.
Each engine doesn't know whether the other one is functioning or not, so I view the loss of one engines power simply as an increased demand of the other one providing power, similar to raising the collective in a single.
My understanding is that if you ask an engine to deliver 107% N2/Nr, the engine will do everything it can to give you that, including maximum fuel flow (N1 topping) if need be.
I can't quite seem to get my head around why this droop happens.
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I'm not sure if I can explain this for you and make things better or just muddy the water more but I"ll give it a shot.
First your assesment of the control system is correct in a perfect world however we haven't taken into consideration "static droop". The basic principal says that the engine will do what ever it can to acheive an N2 datum vs actual N2 match. The datum is whatever value we decide N2 should be, in this case 107%. In real life however what the FCU is going to try to do is match centrifugal force against a spring pressure. The centrifugal force is coming from a flyweight that is driven by N2 and the spring pressure is set by the anticipator cable (connected to your collective lever). As you raise the collective you increase the spring tension and upset the balance which causes the FCU to increase fuel flow instead of waiting for the N2 to droop. If we didn't have this system in place you would have a "static droop" where the N2 rpm could be 107% on the ground but as you add load you would see a droop in N2. You would basically be behind the power curve all the time. The governor will increase fuel flow but not enough to maintain the RPM.
So in twin engine operation the system is setup to maintain a nominal N2 rpm (107%) by increasing fuel flow by a given amount to each engine as you raise the collective. Now when you stow one stove your only adding half of that additional fuel flow for the same collective position and hence you see a bit of a static droop effect.
If the system worked like the FADEC controlled aircraft you should not see this effect as the governor system simply adjusts fuel flow to maintain the N2 RPM datum. We still have the anticipator system in FADEC engines to reduce the transient droop. In the mechanical system the FCU doesn't care what speed the rotor or the N2 are at...only the centrifugal force that those speeds create and how it balances the anticipator spring tension. So at an OEI hover we have the same collective pitch postion adding an additional fuel flow to only one engine which will help carry the load but not quite enough to keep the same RPM as if it was operating along side it's partner engine.
This is much easier to explain if you have a diagram in front of you to see how the whole mess works. At any rate, if this explaination helped then good "I"ll be here till Tuesday!" and if it didn't then disregard all the above and listen to someone who can explain it better!!
Max
First your assesment of the control system is correct in a perfect world however we haven't taken into consideration "static droop". The basic principal says that the engine will do what ever it can to acheive an N2 datum vs actual N2 match. The datum is whatever value we decide N2 should be, in this case 107%. In real life however what the FCU is going to try to do is match centrifugal force against a spring pressure. The centrifugal force is coming from a flyweight that is driven by N2 and the spring pressure is set by the anticipator cable (connected to your collective lever). As you raise the collective you increase the spring tension and upset the balance which causes the FCU to increase fuel flow instead of waiting for the N2 to droop. If we didn't have this system in place you would have a "static droop" where the N2 rpm could be 107% on the ground but as you add load you would see a droop in N2. You would basically be behind the power curve all the time. The governor will increase fuel flow but not enough to maintain the RPM.
So in twin engine operation the system is setup to maintain a nominal N2 rpm (107%) by increasing fuel flow by a given amount to each engine as you raise the collective. Now when you stow one stove your only adding half of that additional fuel flow for the same collective position and hence you see a bit of a static droop effect.
If the system worked like the FADEC controlled aircraft you should not see this effect as the governor system simply adjusts fuel flow to maintain the N2 RPM datum. We still have the anticipator system in FADEC engines to reduce the transient droop. In the mechanical system the FCU doesn't care what speed the rotor or the N2 are at...only the centrifugal force that those speeds create and how it balances the anticipator spring tension. So at an OEI hover we have the same collective pitch postion adding an additional fuel flow to only one engine which will help carry the load but not quite enough to keep the same RPM as if it was operating along side it's partner engine.
This is much easier to explain if you have a diagram in front of you to see how the whole mess works. At any rate, if this explaination helped then good "I"ll be here till Tuesday!" and if it didn't then disregard all the above and listen to someone who can explain it better!!
Max
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N2/Nr drop
Hi,
Here is a control systems answer, not a S76 experienced technicians answer.
Control systems can be made as complex as imaginable, but in practise they tend to be based on simplified rules.
The static droop referred to is associated with a static feedback system (proportional control). If the control is calibrated for two engine operation, then the loss of an engine will create an N2/NR offset that makes the proportional control react (proportional increase in fuel flow). There is however always a 'remaining offset' necessary to drive the control system when operating out of its design point. So a disturbed proportional control system will always display a static offset.
Now most systems are not just 'proportional systems', and classical control theory would among others include 'integral control'. The latter 'integrates' or 'sums over time' the control error to drive the correction, so over time it will reduce the control error to zero, since as long as it sees an error this error will drive corrective actions. This is equivalent to thinking that this system is capable of compensating the permanent offset. The problem here of course is that some care with this permanent driving should be exercised not to create dynamically unstable or out off limit situations.
So to me it seems that the system is close to a (basic) proportional control system.
d3
Here is a control systems answer, not a S76 experienced technicians answer.
Control systems can be made as complex as imaginable, but in practise they tend to be based on simplified rules.
The static droop referred to is associated with a static feedback system (proportional control). If the control is calibrated for two engine operation, then the loss of an engine will create an N2/NR offset that makes the proportional control react (proportional increase in fuel flow). There is however always a 'remaining offset' necessary to drive the control system when operating out of its design point. So a disturbed proportional control system will always display a static offset.
Now most systems are not just 'proportional systems', and classical control theory would among others include 'integral control'. The latter 'integrates' or 'sums over time' the control error to drive the correction, so over time it will reduce the control error to zero, since as long as it sees an error this error will drive corrective actions. This is equivalent to thinking that this system is capable of compensating the permanent offset. The problem here of course is that some care with this permanent driving should be exercised not to create dynamically unstable or out off limit situations.
So to me it seems that the system is close to a (basic) proportional control system.
d3
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delta3 has it pretty close. The "permanent droop" is built into the governor to make it stable and thus prevent the rpm from hunting up and down around the set rpm. If there was no permanant droop, the governor would behave like a dropping a steel ball on a steel plate, it would bounce forever. The premanent droop is like a pillow on the plate, it allows the ball to sink slightly.
A FADEC digital control has the mathmetical sophistication to use integrators as delta3 describes, so it can be truly "isochronus" - constant rpm - and still be very stable.
A FADEC digital control has the mathmetical sophistication to use integrators as delta3 describes, so it can be truly "isochronus" - constant rpm - and still be very stable.
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A FADEC digital control has the mathmetical sophistication to use integrators as delta3 describes, so it can be truly "isochronus" - constant rpm - and still be very stable.
Hoss
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Exploding C30S engines in 76A models
Rumor has it there have been several #3 Power Turbine Wheels failing catastrophically on S76As (and possibly other A/C types?). A new idling restriction has been placed on the engines (no steady state 72%-90.5%N2)
What is going on? What has changed with these engines?
What is going on? What has changed with these engines?
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I am suprised that nobody knows any 'stories' about these engines. Something seems to be going on, considering the new restictions to N2 after all these years, and the failures.
Anybody?
Anybody?
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I don't know about the S76, but some time ago Rolls Royce came out with a requirement to have a sticker on the instrument panel in Bell 407s stating the need to avoid steady state operations between 68% and 86% NG. They have recently amended this to a more accurate set of numbers, something like 68.6% to 87.4%, like I'm going to pay that much attention.
I have asked people in the know and can't get much of an explaination as to why things have changed.
I have asked people in the know and can't get much of an explaination as to why things have changed.
Hey hovering,
I work with CHL in the EMS division and we operate a dozen A model 76's.
We had at least one recent engine failure that may have been related to fatigue caused by idling in the 72%-90.5%N2 range.
We are now abiding by the N2 area of avoidance and also recording N2 overspeeds of 112% and greater (not sure if they ever happen though as I've never been remotely close).
Interesting topic and will be interesting to see what RR does in the future with operations and maintenance.
bb in ca
I work with CHL in the EMS division and we operate a dozen A model 76's.
We had at least one recent engine failure that may have been related to fatigue caused by idling in the 72%-90.5%N2 range.
We are now abiding by the N2 area of avoidance and also recording N2 overspeeds of 112% and greater (not sure if they ever happen though as I've never been remotely close).
Interesting topic and will be interesting to see what RR does in the future with operations and maintenance.
bb in ca
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Rolls Royce CEB A-72-3272 refers:
The max. cont. Nr/N2 RPM is 107.2% with trainsients allowed up to 112.7 for a max. of 15 seconds. Maintenance action is required for transients of 112.7% and above for more than 15 seconds.
This is a high end restriction, added to the already steady state restriction, and is more likely to occur when in a low pitch descent manoeuvre such as an auto. Easy to do if you are doing an auto RPM check.....beware!!
The CEB is interesting reading if you can get a copy from your engineering folk
The max. cont. Nr/N2 RPM is 107.2% with trainsients allowed up to 112.7 for a max. of 15 seconds. Maintenance action is required for transients of 112.7% and above for more than 15 seconds.
This is a high end restriction, added to the already steady state restriction, and is more likely to occur when in a low pitch descent manoeuvre such as an auto. Easy to do if you are doing an auto RPM check.....beware!!
The CEB is interesting reading if you can get a copy from your engineering folk