Sikorsky S-76: Ask Nick Lappos
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Low Time,
I think Brian and bb in ca and the others have it right. A slight loss of prime will make the engine delay a bit on start. I would think you can hold the starter a bit longer than 6 seconds, and you should see it light off. There is no harm in waiting 10 or even 20 seconds, although the fact that it lights immediately after an aborted 6 second crank tells me that it will probably light before 10 sec. If you have fuel flow gauges, note the kick as the gas finally arrives in the engine as the sign to expect lightoff. If not, note the fuel pressure light blinks as the venturi pump wets itself.
If the lightoff delay is an ignition failure while fuel is flowing, the fuel flow gauge and a white fog exhaust are the signs (and of course the quiet in the head set instead of the slight tick-tick of the igniters).
I think Brian and bb in ca and the others have it right. A slight loss of prime will make the engine delay a bit on start. I would think you can hold the starter a bit longer than 6 seconds, and you should see it light off. There is no harm in waiting 10 or even 20 seconds, although the fact that it lights immediately after an aborted 6 second crank tells me that it will probably light before 10 sec. If you have fuel flow gauges, note the kick as the gas finally arrives in the engine as the sign to expect lightoff. If not, note the fuel pressure light blinks as the venturi pump wets itself.
If the lightoff delay is an ignition failure while fuel is flowing, the fuel flow gauge and a white fog exhaust are the signs (and of course the quiet in the head set instead of the slight tick-tick of the igniters).
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Nick, a question. We had the Kratos glass C model - why on the start page were the T5 limits depicted not the "start" limits? Having gone to the trouble of providing a start page I would have thought it axiomatic to provide the relevant/applicable T5 information. Always had me wondering, and FS instructors were not aware until I pointed it out.
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Brian,
Good question. The engine limits are specified in the flight manual and are required markings, so the typical red lines must appear, in any piloting situation, per FAR. There is no approved way to show other limits, and the FAA guards against non-conformities (rightfully) so additional red lines are not allowed.
In the A model, it took a lot of negotiating to come up with the white region below 694 degrees, and I would wage that marking would not be allowed today.
Good question. The engine limits are specified in the flight manual and are required markings, so the typical red lines must appear, in any piloting situation, per FAR. There is no approved way to show other limits, and the FAA guards against non-conformities (rightfully) so additional red lines are not allowed.
In the A model, it took a lot of negotiating to come up with the white region below 694 degrees, and I would wage that marking would not be allowed today.
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Many thanks Nick. If I recall correctly (been some 5 years now) the start page did show an almost invisible (so small) red diamond that depicted a particular T5 start limit.
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Nick et al:
I am trying to find a good drawing of the S-76 gearbox (the inside of course
).
Is it proprietary or why is there nothing really useful out there?
Even the FlightSafety training manual only shows a very rudimentary schematic of the free-wheeling unit.
I asked our DOM and he says he's gonna look in the attic, but is not sure if he finds the info I'm looking for.
Its just for my personal education, I am no engineer, just a pilot interested to learn as much as I can about the aircraft I fly.
Thank you very much in advance!
I am trying to find a good drawing of the S-76 gearbox (the inside of course
).Is it proprietary or why is there nothing really useful out there?
Even the FlightSafety training manual only shows a very rudimentary schematic of the free-wheeling unit.
I asked our DOM and he says he's gonna look in the attic, but is not sure if he finds the info I'm looking for.
Its just for my personal education, I am no engineer, just a pilot interested to learn as much as I can about the aircraft I fly.
Thank you very much in advance!
Hello gents,
Further to a discussion on another forum I am wondering if any of you in the offshore part of the industry have ever heard of a Sikorsky procedure for offshore operators involving the use of the rotor brake (engines at idle) .
Obviously the option exists but I have never seen or heard of such procedure (at least during my 5 years in the offshore industry).
I have hardly ever used it (once in 5 years)on a deck and so have most fellow pilots I have been working with in South Est Asia ( a brake slippage/release comes to my mind as the main reason for not using it).Is it a common practice in other parts of the world?
Thank you in advance for any comments.
Cheers
Bell4can
Further to a discussion on another forum I am wondering if any of you in the offshore part of the industry have ever heard of a Sikorsky procedure for offshore operators involving the use of the rotor brake (engines at idle) .
Obviously the option exists but I have never seen or heard of such procedure (at least during my 5 years in the offshore industry).
I have hardly ever used it (once in 5 years)on a deck and so have most fellow pilots I have been working with in South Est Asia ( a brake slippage/release comes to my mind as the main reason for not using it).Is it a common practice in other parts of the world?
Thank you in advance for any comments.
Cheers
Bell4can
Use of the brake on start is common practice. What do you want to know specifically?
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Regarding the rotor brake, it is both common and allowed to have the brake on efore starting one or both engines, then release the brake after the engines stabilize at idle. In high winds, it is preferred to start against the brake, to minimize dwell time at low Nr and low acceleration.
It is also allowable to shut down while one engine is at idle and the other shut down, thus keeping one DC gen on line and assuring a fast start. This procedure does wear the brake a bit faster than a shutdown with no engines on line, but I don't think it is a major difference,
The flight manual normal procedures describe these runups and shutdowns in detail (bell4can, I wonder how you got to sit in front and don't know this!)
Regarding MGB design, I believe the Flight Safety package shows a sketch of the transmission gear train (with their rpm's) I will hunt down my copy (my garage has a dozen boxes of prime stuff waiting archeologists to explore it!
It is also allowable to shut down while one engine is at idle and the other shut down, thus keeping one DC gen on line and assuring a fast start. This procedure does wear the brake a bit faster than a shutdown with no engines on line, but I don't think it is a major difference,
The flight manual normal procedures describe these runups and shutdowns in detail (bell4can, I wonder how you got to sit in front and don't know this!)
Regarding MGB design, I believe the Flight Safety package shows a sketch of the transmission gear train (with their rpm's) I will hunt down my copy (my garage has a dozen boxes of prime stuff waiting archeologists to explore it!
I'm not positive but I get the feeling he's implying an offshore hot turn.
During offshore landings without shutdowns I don't stop the blades and have never been with anyone who suggested it.
I have stopped blades with a single engine shutdown on scene calls in an air ambulance roll where it's not going to be long on the ground. I still ensure all crew movement is as if the blades were still turning in case of rotor brake failure.
Nick on the C+ and C++ with manual rotor brakes I believe you'll find you can do a rotor stop with both engines at idle; can't say as I ever have though.
Regards,
bb
During offshore landings without shutdowns I don't stop the blades and have never been with anyone who suggested it.
I have stopped blades with a single engine shutdown on scene calls in an air ambulance roll where it's not going to be long on the ground. I still ensure all crew movement is as if the blades were still turning in case of rotor brake failure.
Nick on the C+ and C++ with manual rotor brakes I believe you'll find you can do a rotor stop with both engines at idle; can't say as I ever have though.
Regards,
bb
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Could someone please explain how that works (rotors stopped with engines at idle)?
Is there something in the rotorbrake assembly that disengages the engines from the MRGB?
Is there something in the rotorbrake assembly that disengages the engines from the MRGB?
bb in ca:
You are right in your asumption. I meant to ask for the use of the rotor brake (engines at idle) in offshore hot turns.
My apologies to 212man and Mr Lappos (yes I do know of section 2 as I happen to sleep with the flight manual 6 months a year..well, almost.. ) as this was not clear in my previous posting.
Bell4can
You are right in your asumption. I meant to ask for the use of the rotor brake (engines at idle) in offshore hot turns.
My apologies to 212man and Mr Lappos (yes I do know of section 2 as I happen to sleep with the flight manual 6 months a year..well, almost..
) as this was not clear in my previous posting.Bell4can
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Nick Lappos! Soft limiting 76 C+/C++
Can soft limiting be used on a day to day normal operation or is it designed as a "safety net" in an unplanned situation.
In my company, it is split 50/50 as to which way it is to be used but as excursions in soft limit does not trigger any events whatsoever and it is not prohibited in the RFM...... you would think it is O.K.?
Any comments beside Nick's are also welcomed.
In my company, it is split 50/50 as to which way it is to be used but as excursions in soft limit does not trigger any events whatsoever and it is not prohibited in the RFM...... you would think it is O.K.?
Any comments beside Nick's are also welcomed.
In my opinion you are limited by the stated Limitations in the RFM. Transient limits are not to be planned for. Soft limiting is beyond the limitations and are transients.
I do use soft limiting and I don't think it's a bad thing BUT it's not planned for or routinely used. The 76 C+ and C++ are not easy to finesse to take-off power limits and occasionally soft limiting is used.
Limitations Section - C++
OPERATING CONDITION Take Off
TRANSMISSION TORQUE LIMIT (%) 100
%N1 100.0
POWER ON
Maximum: 108% Nr; except 109% transient operation for 20 seconds
Minimum: 106% Nr (dual-engine operation)
NOTE
Operation above 104% torque, 100.5% N1, or 912°C T5 is reserved for actual emergencies, inadvertent transient excursions, or, as artificially biased indications, with the OEI training provision.
I think the note is there to allow for use of the soft-limiting without penalty. Notes are not limitations but notes.
A whole other subject would be why are pilots taking-off with weights that aren't right for the a/c with the present conditions.
Just my opinion
Fly safe,
bb
I do use soft limiting and I don't think it's a bad thing BUT it's not planned for or routinely used. The 76 C+ and C++ are not easy to finesse to take-off power limits and occasionally soft limiting is used.
Limitations Section - C++
OPERATING CONDITION Take Off
TRANSMISSION TORQUE LIMIT (%) 100
%N1 100.0
POWER ON
Maximum: 108% Nr; except 109% transient operation for 20 seconds
Minimum: 106% Nr (dual-engine operation)
NOTE
Operation above 104% torque, 100.5% N1, or 912°C T5 is reserved for actual emergencies, inadvertent transient excursions, or, as artificially biased indications, with the OEI training provision.
I think the note is there to allow for use of the soft-limiting without penalty. Notes are not limitations but notes.
A whole other subject would be why are pilots taking-off with weights that aren't right for the a/c with the present conditions.
Just my opinion
Fly safe,
bb
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The soft limiter allows minor transient excursions up to 100.5% N1 to maintain 107% NR. Just after this excursion, the limiter will immediately begin reducing the N1 at a rate of 0.1% per second to 100%. This soft limiter logic is then reset and again becomes available once N1 goes to 99.9%.
Like you say, don't plan to use it, but it is a handy tool for unexpected events.
Pedro
Like you say, don't plan to use it, but it is a handy tool for unexpected events.
Pedro
