Sikorsky S-76: Ask Nick Lappos
Rear CG
AC,
XUX had (has?) the same problem when it arrived as the first A+. Heavy engine cover, all the extra avionics in the tail, Urst didn't like the club seats, either. Both forward float bays were eventually filled with as much lead ballast as we could fit, to get the CoG within limits. About 140kg, IIRC, but I don't know if it's still there
XUX had (has?) the same problem when it arrived as the first A+. Heavy engine cover, all the extra avionics in the tail, Urst didn't like the club seats, either. Both forward float bays were eventually filled with as much lead ballast as we could fit, to get the CoG within limits. About 140kg, IIRC, but I don't know if it's still there
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Ascend, that's a huge fuel burn. I guess there's a reason B models are relatively rare. In the A++, we burn well under 600 lb/hr, if we can get above 3000 ft, flying at Vne. We rarely see more than 600, and that's at sea level pulling max continuous power. We plan for 3 hours fuel, and usually have more. That extra fuel makes a big difference.
The fuel burn is the price we pay for having 1033 horses lined up on each side.
The boss wants the grunt, we can take a full load of 9 pax with baggage, polo sticks etc and a reduced fuel load and still launch with the greatest of ease. The cost of the fuel is the least part of the equation, and range rarely matters if the normal run is only 130-150 nm.
The boss wants the grunt, we can take a full load of 9 pax with baggage, polo sticks etc and a reduced fuel load and still launch with the greatest of ease. The cost of the fuel is the least part of the equation, and range rarely matters if the normal run is only 130-150 nm.
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Well, horses for courses. Over here, range always matters. Going 200NM offshore, the customer always wants to carry the max load, and 800 lb/hr with about 2.5 hrs fuel max is why the 412 won't cut the mustard (the slow speed is another, which contributes to lack of range). The S76C+ looks like the coming thing, with good range and payload. There are no B models in the GOM that I know of, but for VIP work they may be very good. I've never even seen one other than in pictures.
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S76'B'
Ascend Charlie's spot on. Buy the 'B' model for the Grunt or for Hot 'n High. Strictly from a pilot's point of view, the best model S76. Loads of power and an excellent fuel control system with a simple manual override if the duplex computers fail. FADECs on the 'C' have maybe gone too far.
We operate a corporate 'B' that weighs in at 8546 lbs on the ramp with aft-facing club seats and credenza. That's without the noise cocoon. As with everything in life, there's always a price to pay. In this case, always PLAN to use 800 lbs/hour.
C of G has been a problem in all 76's but the 'B' was helped by placing the battery(s) in the nose. The range can be improved by fitting the extra tank in the boot, but just try positioning single pilot with all tanks full !!
Hi to John Eacott (It's Urs without the T). XUX is still spending 11 months / year in the hangar. An excellent ship. Used to get fuel flows down to 520 lbs/hour at 8,000 ft.
I thought about asking to take it to Sumatra where it could be put to much better use. However, COALIN says the boys with the Stars and Stripes can hack it (see the Tsunami thread) so best leave it at Bankstown.
By the way, I used to be an S76 devotee until I flew the Agusta 139 last year.
We operate a corporate 'B' that weighs in at 8546 lbs on the ramp with aft-facing club seats and credenza. That's without the noise cocoon. As with everything in life, there's always a price to pay. In this case, always PLAN to use 800 lbs/hour.
C of G has been a problem in all 76's but the 'B' was helped by placing the battery(s) in the nose. The range can be improved by fitting the extra tank in the boot, but just try positioning single pilot with all tanks full !!
Hi to John Eacott (It's Urs without the T). XUX is still spending 11 months / year in the hangar. An excellent ship. Used to get fuel flows down to 520 lbs/hour at 8,000 ft.
I thought about asking to take it to Sumatra where it could be put to much better use. However, COALIN says the boys with the Stars and Stripes can hack it (see the Tsunami thread) so best leave it at Bankstown.
By the way, I used to be an S76 devotee until I flew the Agusta 139 last year.
Two S76 mishaps
According to Sikorsky info there has been two S76 mishaps this week. On C+ in the Pacific Rim and one A in South america.
Anybody knows more details - crew, WX, mechanical, unknown???
CB
Anybody knows more details - crew, WX, mechanical, unknown???
CB
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S76A Mishap
Nothing official yet but a Brazilian S76A suffered loss of control at the commencement of a maintenance flight. It ended up on its side. Two pilots and three engineers on board. No serious injuries but one engineer apparently had his seat belt undone and sustained minor injuries.
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S76 Mishap
S76C+ in Japan. Carrying out Rescue training........one engine ran down and aircraft landed in the water. No floats deployed so the aircraft sank in 500+ meters of water. Attempts are being made to recover the FDR. No fatalities so far as I am aware.
S76 Swashplate
I have tried to find an answer on this but nobody seems to know, so I am trying PPRuNe for help.
Most of the parts in the rotorhead is similar in apperance on the A and B (C) models except the rotating scissor link. On the B (C) model this link is offset and the end result is angled pitchlinks.
Anybody know what the reason for this is???
I do not want to start anything with phase angles
but I am guessing this could be the case.
CB
Most of the parts in the rotorhead is similar in apperance on the A and B (C) models except the rotating scissor link. On the B (C) model this link is offset and the end result is angled pitchlinks.
Anybody know what the reason for this is???
I do not want to start anything with phase angles
but I am guessing this could be the case.CB
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The offset swashplate is rotated so that the blade's pitch angle increases with aft laging motion. This is called "alpha 1 coupling", and it makes the blade a bit more stable, and it also makes a bit more collective pitch available. The way it works is that the swashplate horn is behind the blade pitch horn, so the pitch link must lean forward to meet the blade. If the blade lags aft, the pitch link stands more vertically, and is therefore a bit longer, and makes more angle on the blade. This helps damp any lag motions.
The change was made as the gross weight was increased from the A to the B.
The change was made as the gross weight was increased from the A to the B.
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The stability works both ways, as the blade leads, the angle is reduced; as it lags, the angle is increased. This makes the blade more stable in-plane. The idea of using alpha 1 is not new, it is part of the designer's bag of tricks. Look at the push rods of many helicopters to see how this angle is used. I recall seeing it on EH-101 as well.
Iconoclast
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Aw crap, I wanted to ask that question.
I figured that if I did Nick would think I was giving him a dig. However, it is a valid question. If there is a positive effect when the blades lag is there a negative effect when the blades lead?
I may continue this when I get a bit more information.
Overtaken by events. See above.
I may continue this when I get a bit more information.
Overtaken by events. See above.
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S-76d
Avoid imitations
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Sounds great, the type could now use more performance to compete with the AB139.
However, one question comes immediately to mind.
Bearing in mind the weight of the new equipment, such as enhanced anti-icing, new soundproofing, HUMS etc, will there be any REAL increase in usable performance / payload / endurance?
What appears at first glance to be an increase in performance sometimes gets "swallowed up" when the whole package is considered. I hope not - perhaps that quirky "short field" takeoff profile will be no longer required.
However, one question comes immediately to mind.
Bearing in mind the weight of the new equipment, such as enhanced anti-icing, new soundproofing, HUMS etc, will there be any REAL increase in usable performance / payload / endurance?
What appears at first glance to be an increase in performance sometimes gets "swallowed up" when the whole package is considered. I hope not - perhaps that quirky "short field" takeoff profile will be no longer required.
Getting the latest engine technology into the S76 is great, but, why not have the choice between Turbomeca and P&W. The S76 with Turbomeca is a mature and proven aircraft, and think of fleet operators, I think they will be pissed by getting a new type of engines. Have a choice I say, othervise the idea seems good.
Must say though, have a hard time se that little tiny PW210S with single compressor, single gasturbine and single freeturbine produce more power than the PT6. At what, 60 000 rpm and 1000 deg C?
MTBF?
CB
Must say though, have a hard time se that little tiny PW210S with single compressor, single gasturbine and single freeturbine produce more power than the PT6. At what, 60 000 rpm and 1000 deg C?
MTBF?
CB
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S76A Transient Limits
Simply---Does pulling up to 115% (230% total) torque for under 5 seconds exceed RFM limits?
Long version---In the limitations section of the RFM, reference is given to figure 1-5 which states “Transient – Time: 5 Second – Transmission Torque Limit: 115%”. This is not an OEI limit. One could interpret this as a 230% total torque limit. FlightSafety seems to agree with this interpretation.
Right after the RFM reference to figure 1-5 is “NOTE: …the sum of the individual torque values does not exceed 200%” there is no other reference to the 5 second limit.
Which is it?
Also, there is not an "Intentional use of transients prohibited" clause. What is Sikorskys position on this?
Bruised Armpit
Long version---In the limitations section of the RFM, reference is given to figure 1-5 which states “Transient – Time: 5 Second – Transmission Torque Limit: 115%”. This is not an OEI limit. One could interpret this as a 230% total torque limit. FlightSafety seems to agree with this interpretation.
Right after the RFM reference to figure 1-5 is “NOTE: …the sum of the individual torque values does not exceed 200%” there is no other reference to the 5 second limit.
Which is it?
Also, there is not an "Intentional use of transients prohibited" clause. What is Sikorskys position on this?
Bruised Armpit
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“NOTE: …the sum of the individual torque values does not exceed 200%”
I think that 200% limit is for normal operations i.e. take-off
so you could have 1 engine at 104% and the other at 96% and that would be OK for take-off. Transient limits are notnormal ops they are transient.
I think that 200% limit is for normal operations i.e. take-off
so you could have 1 engine at 104% and the other at 96% and that would be OK for take-off. Transient limits are notnormal ops they are transient.