Sikorsky S-76: Ask Nick Lappos
A query of the database http://www.griffin-helicopters.co.uk...&submit=Search
reveals these two, in addition to the lightning strike, and a passenger walking into a blade.
Blade Seperated, but due to spindle bearing failure.
http://www.griffin-helicopters.co.uk...identkey=14398
Blade Seperated after contacting fuselage, during Inadvertant IMC
http://www.griffin-helicopters.co.uk...identkey=19131
Never even sat in one, so know nothing about them.
V.
reveals these two, in addition to the lightning strike, and a passenger walking into a blade.
Blade Seperated, but due to spindle bearing failure.
http://www.griffin-helicopters.co.uk...identkey=14398
Blade Seperated after contacting fuselage, during Inadvertant IMC
http://www.griffin-helicopters.co.uk...identkey=19131
Never even sat in one, so know nothing about them.
V.
Last edited by VeeAny; 25th Aug 2007 at 20:20. Reason: Clarify the lightning strike etc.
After the spindle failure, Sikorsky modified the head with the addition of a collar on the spindle, to stop it moving all the way out, and a tell-tale yellow strip which you check on the pre-flight.
No strip, run away.
No strip, run away.
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Schreiner Airways (operating in Nigeria as Aero Contractors Nigeria) around 2000/2001 had about a 1 metre inboard section of a blade break off in flight from an S76B (either 5N-BBK or 5N-SDW). The rear edge of the main spar was visible for nearly 1 metre and some outer skin had been torn off, exposing the filler foam for around another half metre. It landed safely on a drill ship and was flown back to Port Harcourt after a spare (A+) blade had been borrowed from Bristow and shipped out that night. It was due to a manufacturing defect on a particular batch of blades all of which were grounded until the manufacturer sent out specialist repair teams to fit strengthening patches on the inboard sections of the bad batch.
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The first spindle failure occured in South America within months of the 76 going into operation. The blade flew off on approach to & within sight of the rig & all 14 were killed. The next one was a Bristow 76 out of Aberdeen doing some IF training & all 4 on board were killed.
After these 2 accidents, Sikorsky did some spindle mods & I believe no more blades flew off for that reason. Lightning strikes, etc are not the fault of the blade.
Incidently Air Logistics & Okanagan Helicopters were the first 2 operators of the 76.
After these 2 accidents, Sikorsky did some spindle mods & I believe no more blades flew off for that reason. Lightning strikes, etc are not the fault of the blade.
Incidently Air Logistics & Okanagan Helicopters were the first 2 operators of the 76.
Nigel said
Which is true - a blade is not a sentient being so couldn't really ever be considered to be at fault
However, the manufacturer / overhauler ... now that is a different matter. If a blade has a lightning strike, is sent back for overhaul, then subsequently fails killing lots of people, and it transpires that a manufacturing defect resulted in the lightning strike seriously weakening the spar, and that defect was not noticed at manufacture nor during overhaul, nor was the damaged spar, then someone is at fault.
HC
Lightning strikes, etc are not the fault of the blade
However, the manufacturer / overhauler ... now that is a different matter. If a blade has a lightning strike, is sent back for overhaul, then subsequently fails killing lots of people, and it transpires that a manufacturing defect resulted in the lightning strike seriously weakening the spar, and that defect was not noticed at manufacture nor during overhaul, nor was the damaged spar, then someone is at fault.
HC
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Nigel has the straight story. There was an accident (Brazil) where the spindle let go, after the steel spindle liner had let go. Without the liner, the spindle had extra motion in lead-lag and flapping that overstressed the nut area. Retaining the liner stopped that mode, but it turned out that the normal motions produced enough fatigue damage that a second similar accident occurred (Bristow, Aberdeen). At that point, we installed a redundant steel rod that compressed the entire spindle, and also served as a second load path. Crews were sent world-wide to install the kits at no cost. I lived through these events as S76 project pilot, and it was so very traumatic. Gerry Hardy was a friend, and quite a pilot. I still can feel the pain of that moment.
I cannot describe the way those of us who build these machines put all our best into the work, and how much of us is in the aircraft. Through success and failure, you can be sure there is not a drop of cynical attitude, no attempt to be "good enough" when safety is concerned. I met the engineer who signed off those lightning strike blades, he was devastated when that accident occurred, absolutely devastated.
Just as pilots know that each decision can reach life or death importance, the designers, builders and technicians who develop and test the aircraft feel the same sense of responsibility in their hearts.
I cannot describe the way those of us who build these machines put all our best into the work, and how much of us is in the aircraft. Through success and failure, you can be sure there is not a drop of cynical attitude, no attempt to be "good enough" when safety is concerned. I met the engineer who signed off those lightning strike blades, he was devastated when that accident occurred, absolutely devastated.
Just as pilots know that each decision can reach life or death importance, the designers, builders and technicians who develop and test the aircraft feel the same sense of responsibility in their hearts.
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A not very good photo of one of natures gentlemen (at my wedding - only phot I have). Shared a flat with him in Kings Cross for weekend forays from Nowra when single, and on the same squadron for the duration of his exchange, he instructor, I humble boggy/student. See you upstairs Gerry.
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76A++ information needed
Excellent thread guys, I just spent the past two days reading through the whole thing and learned a lot.
I am finally getting out of 212/412's and am starting a new job in the GOM flying a 76 A++. I have a FSI manual but am looking for any other documentation I can download so I can read up for the next few months and make the transition that much easier.
Do any of you know where I can download a flight manual or anything else that will help me out? I am willing to pay for it if necessary. Just don't know where to find it.
Thanks
I am finally getting out of 212/412's and am starting a new job in the GOM flying a 76 A++. I have a FSI manual but am looking for any other documentation I can download so I can read up for the next few months and make the transition that much easier.
Do any of you know where I can download a flight manual or anything else that will help me out? I am willing to pay for it if necessary. Just don't know where to find it.
Thanks
The manual for the A++ is a mess.
First you need an A manual.
Then you insert supplement 29 (makes it A+)
Then you insert supplement 29A (installs 1S1 engines in an A+ w/o using the pwr)
Then you insert supplement 29B (makes it A++)
By now you have a manual 3-4 inches thick with multiple pages with same number and nearly same information
Do not know where you can find one though.
First you need an A manual.
Then you insert supplement 29 (makes it A+)
Then you insert supplement 29A (installs 1S1 engines in an A+ w/o using the pwr)
Then you insert supplement 29B (makes it A++)
By now you have a manual 3-4 inches thick with multiple pages with same number and nearly same information
Do not know where you can find one though.
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Thanks Collective Bias,
It's good to know what makes up the A++, now I just need to figure out if a digital version of all that stuff exists.
If I was really desperate, I could get the hard copy and scan all 4 inches one page at a time.... but I'm not that desperate!
It's good to know what makes up the A++, now I just need to figure out if a digital version of all that stuff exists.
If I was really desperate, I could get the hard copy and scan all 4 inches one page at a time.... but I'm not that desperate!
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DC Gen = Mo Powa
Regarding the increase in Arriel Power with a fully loaded DC Generator.
The Arriels limit power based either on N1 (compressor) speed or output torque. If you are not limited by torque, the engine will achieve a certain N1 speed and hold it there.
The catch is, the DC generator is driven by the N1 spool of the engine. So, here's how it goes: you are at 104.3%N1 power then increase the power requirement of the DC generator. The N1 spool slightly decreases speed due to the increased load. The DECU senses this speed decrease and increases fuel flow to bring N1 back up to 104.3% (or whatever the active limit is). BUT, due to the (in)efficiency of the N1 turbine, there is also more energy delievered to the power turbine as well.
Admittedly, it's not much more power, but it IS measurable, as proven by the Sikorsky powerplant flight test guru.
Now, to shift gears, I'd like to hear from anyone that has experience with "OEI training mode" on the 2S2. Is it an improvement over the 2S1?
Hoss
The Arriels limit power based either on N1 (compressor) speed or output torque. If you are not limited by torque, the engine will achieve a certain N1 speed and hold it there.
The catch is, the DC generator is driven by the N1 spool of the engine. So, here's how it goes: you are at 104.3%N1 power then increase the power requirement of the DC generator. The N1 spool slightly decreases speed due to the increased load. The DECU senses this speed decrease and increases fuel flow to bring N1 back up to 104.3% (or whatever the active limit is). BUT, due to the (in)efficiency of the N1 turbine, there is also more energy delievered to the power turbine as well.
Admittedly, it's not much more power, but it IS measurable, as proven by the Sikorsky powerplant flight test guru.
Now, to shift gears, I'd like to hear from anyone that has experience with "OEI training mode" on the 2S2. Is it an improvement over the 2S1?
Hoss
Very interesting HOSS, I guess it is why we have to switch the GEN off to perform ground power checks.
Do you know at what stage we are supposed to meet the maximum fuel flow ?
Do you know at what stage we are supposed to meet the maximum fuel flow ?
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Yes, EXACTLY why the gen is turned off. And, speaking of power checks, that PITA three minute wait during a Arriel ground power check is also a function of the engine being N1 rated.
The same guru engineer discovered that the predicted performance would be too optimistic if you didn't let the engine "cook up" during the gnd pwr check. The N1 & T5 numbers after three minutes are representative of the engine's condition in flight. But, I don't understand the dynamics of the cause. Something to do with the turbine blades growing and closing (or opening?) gaps... ???
Sorry, don't know about the max fuel flow question.
HO5S
The same guru engineer discovered that the predicted performance would be too optimistic if you didn't let the engine "cook up" during the gnd pwr check. The N1 & T5 numbers after three minutes are representative of the engine's condition in flight. But, I don't understand the dynamics of the cause. Something to do with the turbine blades growing and closing (or opening?) gaps... ???
Sorry, don't know about the max fuel flow question.
HO5S
We can imagine that, at a certain regime we can eventually meet a condition where the stepper motor is at its maximum opening and cannot provide more fuel...
I think the remark we can find in S76C+ RFM (page 1-5 part 1 operating limitations - "Gross weight reduction due to maximum fuel flow rate restriction" ) is reflecting this condition.
But it seems that, given the rather low temperatures and pres. altitudes where this limitation is in force the limiting factor, here, will be the torque ( 135%) before the N1.
I usually fly the "C+" between a ISO +10 and ISO +20 temperature conditions and never had to deal with this limitation untill now.
I think the remark we can find in S76C+ RFM (page 1-5 part 1 operating limitations - "Gross weight reduction due to maximum fuel flow rate restriction" ) is reflecting this condition.
But it seems that, given the rather low temperatures and pres. altitudes where this limitation is in force the limiting factor, here, will be the torque ( 135%) before the N1.
I usually fly the "C+" between a ISO +10 and ISO +20 temperature conditions and never had to deal with this limitation untill now.
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S76 limitation
Was there ever a S76 RFM limitation, caution or warning limiting the maximum nose up attitude to 10 degrees within 30' AGL?
Or is this just something I faintly remember for some company SOP's?
Or is this just something I faintly remember for some company SOP's?
The 10 degrees nose up is to avoid bumping the tail on the ground. There is always a lot of nose-up attitude trying to slow a 76 down a bit, and for running landings, specially OEI, you have to pay attention before touchdown.
Remember you ain't got no stinger like in a 109, and the first thing to get wiped off is the hydraulic lines to the tail rotor.
Remember you ain't got no stinger like in a 109, and the first thing to get wiped off is the hydraulic lines to the tail rotor.
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It is just a caution, but wise folks watch. I wrote it. The penalty for exceeding 14.7 degrees is that you touch the tail fairing, scrape the paint and buy your crew chief a case of beer. At nose into 15 knots of wind at light weight, full aft CG you hover at 10 degrees nose up, or so.
The fairing is good for a 3000 lb whack, so you would have to work to make it do more than just crush a bit. If you really bashed to fairing, there is slight possibility you can disrupt the TR cables, but that would have to be one awful strike.
The fairing is good for a 3000 lb whack, so you would have to work to make it do more than just crush a bit. If you really bashed to fairing, there is slight possibility you can disrupt the TR cables, but that would have to be one awful strike.
Was just watching a S-76 video earlier on youtube.. when hes flaring on approach to the runway the warning light comes on, i take it thats the warning light for 10 Degrees nose up??
Heres the video http://youtube.com/watch?v=3tfECaTMkAk&feature=related
Heres the video http://youtube.com/watch?v=3tfECaTMkAk&feature=related