30 min Dry Run Capabilities
Shawn
Sounds good in theory but maybe you haven't seen a decent N Sea sea state close up and personal! There are various reasons not to:
1) The rotor blades are likely to chop the liferaft and its occupants up (and if you keep collective pitch on to reduce the liklihood of that, the downwash will have the liferafts everywhere except where the pax can board them dry)
2) After you happily taxy off into the sunset, what are you going to do when you find that all the pax are in the liferafts without crew members to lead them, and you are left with no rafts!
If its OK to shut down and then get into the crew liferaft (if there was one), surely its better to all do it at the same time. Or do you think that the captain should go down with his ship to save the women and children who might be on board? The difficulty with that is the cockpit of an S Puma or 92 is not tall enough to stand up and salute whilst the water comes over one's head, therefore rather spoiling the effect.
In reality, most of the time a big heli will float right ways up after shutdown, even though the motion will feel dreadful to the crew. If its that wild, chances are the liferaft will go upside down from time to time too. As we have said before, surely its better not to end up in the water in the first place, and for that we need good design, not paper safety.
HC
Sounds good in theory but maybe you haven't seen a decent N Sea sea state close up and personal! There are various reasons not to:
1) The rotor blades are likely to chop the liferaft and its occupants up (and if you keep collective pitch on to reduce the liklihood of that, the downwash will have the liferafts everywhere except where the pax can board them dry)
2) After you happily taxy off into the sunset, what are you going to do when you find that all the pax are in the liferafts without crew members to lead them, and you are left with no rafts!
If its OK to shut down and then get into the crew liferaft (if there was one), surely its better to all do it at the same time. Or do you think that the captain should go down with his ship to save the women and children who might be on board? The difficulty with that is the cockpit of an S Puma or 92 is not tall enough to stand up and salute whilst the water comes over one's head, therefore rather spoiling the effect.
In reality, most of the time a big heli will float right ways up after shutdown, even though the motion will feel dreadful to the crew. If its that wild, chances are the liferaft will go upside down from time to time too. As we have said before, surely its better not to end up in the water in the first place, and for that we need good design, not paper safety.
HC
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Why don't helicopter manufacturers build in a one way sprag clutch into the main rotor shaft, so that in the event of a gearbox seizure, the output shaft keeps turning in autorotation? This would help in the loss of tail rotor too! This is how we design our un-manned helicopters, we can auto rotate to the ground in the event of engine failure, main gearbox seizure or tail rotor drive shaft failure.
Hi Shawn
Well you are right of course - and what is better than falling from a great height with no rotor is to follow the flight manual when it says Land Immediately, even if you don't like the look of the sea. Ditching under control in a wild sea is moderately survivable, falling with no rotor is not! But then again if the pilots thought that in reality they had 30 mins and the Land Immediately was just some certification arse covering...
chopjock - I think it might be a problem of scalability. On the Super Puma family the freewheels (sprag clutch) are after the first stage of reduction and run aroung 8000 rpm (from memory!) and still give the occasional problem, but by the time the rpm is reduced to 265 for the rotor drive, the torque is massive. I am not sure that its feasible to design a sprag clutch that would take the torque, and of course it would have to be more reliable than current transmissions (say <1 failure every 3 million flight hours) - it would be rather embarrasing to lose drive to the main rotor whilst the tail rotor was still working, and with you over that raging sea...
HC
Well you are right of course - and what is better than falling from a great height with no rotor is to follow the flight manual when it says Land Immediately, even if you don't like the look of the sea. Ditching under control in a wild sea is moderately survivable, falling with no rotor is not! But then again if the pilots thought that in reality they had 30 mins and the Land Immediately was just some certification arse covering...
chopjock - I think it might be a problem of scalability. On the Super Puma family the freewheels (sprag clutch) are after the first stage of reduction and run aroung 8000 rpm (from memory!) and still give the occasional problem, but by the time the rpm is reduced to 265 for the rotor drive, the torque is massive. I am not sure that its feasible to design a sprag clutch that would take the torque, and of course it would have to be more reliable than current transmissions (say <1 failure every 3 million flight hours) - it would be rather embarrasing to lose drive to the main rotor whilst the tail rotor was still working, and with you over that raging sea...
HC
So for really big sea states in extreme situations where a ditching will cause a rollover it would be better to evacuate the pax from a low hover/hovertaxi - at least you give the pax a fighting chance whether or not there are any crew members there to guide them.
I know I would rather drop into the sea and fend for myself instead of having to escape from an inverted helicopter with 15 or so others and then have to fend for myself.
If you as the captain then find yourself in the water without a raft a. your safety equipment provision isn't very well thought out and b. you are at least in an immersion suit with a lifejacket and an ELT/EPIRB/PLB.
In my mind a much better option than ditching and then having everyone use their dunker training. I am talking about 'in extremis' situations where you know the MRGB will seize and you only have limited time to deal with the situation and nowhere to land except the very large seas.
I know I would rather drop into the sea and fend for myself instead of having to escape from an inverted helicopter with 15 or so others and then have to fend for myself.
If you as the captain then find yourself in the water without a raft a. your safety equipment provision isn't very well thought out and b. you are at least in an immersion suit with a lifejacket and an ELT/EPIRB/PLB.
In my mind a much better option than ditching and then having everyone use their dunker training. I am talking about 'in extremis' situations where you know the MRGB will seize and you only have limited time to deal with the situation and nowhere to land except the very large seas.
in extremis
How do suggest we co-ordinate the evacuation of 19 guys, with no crewmen in the back on intercom? Shouting "brace, brace, brace" over the PA is one thing, attempting a lengthy discourse on how we'd like "you all to jump out, in an orderly manner" is another thing entirely!
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All this talk of ditching should be irrelevant. The industry has invested a huge amount of time and money on twin engine operations so that we should never have to ditch following an engine malfunction (OK PC2e is worthy of another thread). We now are in the situation where the next focus of attention should be never having to ditch following a transmission failure.
Of course the mechanical bits of the MRGB are designed such that the chances of failure are so small, they should never fail in the life of the gearbox. Great - the way it should be. Sikorsky tried this approach for the lube system on the S92. Maybe on the basis of the Blackhawk family, Sikorsky had a rightful claim to the "extremely remote chance of failure". Clearly this wasn't the case with the titanium bolts on the oil filter. But perhaps it is true now they have changed the bolts?
It strikes me that the inclusion of the 30 mins dry run capability is a cop out clause because manufacturers couldn't meet/proove the extremely remote chance of failure requirement. If the lube system was as reliable as the rest of the gearbox, we wouldn't need any dry run ability.
I have no idea if viable technology is available to make MGB lube systems as reliable as the rest of the gearbox. If it is, then FAR 29 should be ammended to remove the 30 mins clause, forcing manufacturers to make their lube systems reliable enough. If not, then instead of 30 mins, the regulations should simply require that following a failure (partial or total) of the MGB lube system, the aircraft should be able to return to a safe place to land. In other words, the dry run capability should be related to the range of the aircraft.
Of course this will probably mean some form of emergency lube system, like that on the S61 (by the way 2 hours at Vy!!!) or a glycol cooling system a la 225. Of course the reliability of the emergency system must also be regulated and we as pilots must be able to test the system is working prior to taking it flying. After all we need to know we really do have the ability the book claims.
Of course the mechanical bits of the MRGB are designed such that the chances of failure are so small, they should never fail in the life of the gearbox. Great - the way it should be. Sikorsky tried this approach for the lube system on the S92. Maybe on the basis of the Blackhawk family, Sikorsky had a rightful claim to the "extremely remote chance of failure". Clearly this wasn't the case with the titanium bolts on the oil filter. But perhaps it is true now they have changed the bolts?
It strikes me that the inclusion of the 30 mins dry run capability is a cop out clause because manufacturers couldn't meet/proove the extremely remote chance of failure requirement. If the lube system was as reliable as the rest of the gearbox, we wouldn't need any dry run ability.
I have no idea if viable technology is available to make MGB lube systems as reliable as the rest of the gearbox. If it is, then FAR 29 should be ammended to remove the 30 mins clause, forcing manufacturers to make their lube systems reliable enough. If not, then instead of 30 mins, the regulations should simply require that following a failure (partial or total) of the MGB lube system, the aircraft should be able to return to a safe place to land. In other words, the dry run capability should be related to the range of the aircraft.
Of course this will probably mean some form of emergency lube system, like that on the S61 (by the way 2 hours at Vy!!!) or a glycol cooling system a la 225. Of course the reliability of the emergency system must also be regulated and we as pilots must be able to test the system is working prior to taking it flying. After all we need to know we really do have the ability the book claims.
attempting a lengthy discourse on how we'd like "you all to jump out, in an orderly manner" is another thing entirely!
Makes you wonder how the regulators allow so many pax in the back as SLF without a cabin crew member to take care of them.
In my scenario I thought it was fairly clear that the co-pilot would escort the pax off the aircraft and into the dinghies - it might not be very palatable but a lot better than putting everyone at risk by ditching in a big sea where they all have to escape from underwater.
In my scenario I thought it was fairly clear that the co-pilot would escort the pax off the aircraft and into the dinghies - it might not be very palatable but a lot better than putting everyone at risk by ditching in a big sea where they all have to escape from underwater.
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In normal missions, all people on board are well trained-because they have to go through lots of training....
As far as i know, everybody who is going to work on a rig in the sea has to pass underwater egress training-or is this not an international standard?
Before each flight, we have briefed all passengers telling them exactly what to do in an emergency situation....
Luckily, i never had to try if all emergency maneuvers would have worked as we briefed them....
As far as i know, everybody who is going to work on a rig in the sea has to pass underwater egress training-or is this not an international standard?
Before each flight, we have briefed all passengers telling them exactly what to do in an emergency situation....
Luckily, i never had to try if all emergency maneuvers would have worked as we briefed them....
In civil offshore flying I have never heard of any pax being trained in hover exit or even heard of it being mentioned.
Doing it with 19 untrained pax and expecting anyone to survive with no rafts in a sea state that wouldn't "allow" ditching is wishfull thinking IMHO.
Power on "controled" ditching is the best of a nasty list of options in the event of a "Land or ditch immediately event" -again IMHO
Doing it with 19 untrained pax and expecting anyone to survive with no rafts in a sea state that wouldn't "allow" ditching is wishfull thinking IMHO.
Power on "controled" ditching is the best of a nasty list of options in the event of a "Land or ditch immediately event" -again IMHO
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Makes you wonder how the regulators allow so many pax in the back as SLF without a cabin crew member to take care of them.
In my scenario I thought it was fairly clear that the co-pilot would escort the pax off the aircraft and into the dinghies - it might not be very palatable but a lot better than putting everyone at risk by ditching in a big sea where they all have to escape from underwater.
In my scenario I thought it was fairly clear that the co-pilot would escort the pax off the aircraft and into the dinghies - it might not be very palatable but a lot better than putting everyone at risk by ditching in a big sea where they all have to escape from underwater.
I don't see how providing training normally reserved for Navy seals (or Kevin Costner hoo haa) has a place in commercial aviation, where the rules and regulations are meant to prevent critical component failures with the A/C used.
Hueyracer, unfortunately not all offshore operators include the HUET in their offshore survival training. I know that Norway, UKCS, and Atlantic Canada do, and rightly so as a last case resort.
Droopystop has the right attitude IMHO, let's see more of this proactive discussion and less nonsense.
Safe Flying
Max
Last edited by maxwelg2; 28th Nov 2009 at 19:31.
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Does anybody have any hard information regarding what the limiting design factors are with regard to expected (and demonstrated) extended MGB running time on the S61, 225, or any other type/s (and the Lear Fan F/W mentioned earlier for that matter) after the ELS kicks in ?
Interested in any/all combinations (such as, but not limited to ) :
"spare resevoir capacity" ?
number of application points ?
pressure at which coolant is applied ?
type of coolant ?
liquid ? solid ? mix ? gaseos ?
aircooled ?
additives ?
internal (hard surface) cooling ?
Want to move away from generalities such as "difficult", "technically demanding", "current regulations don't require..." etc...etc...and move on - there must be tons of really good technical information out there available from sources who have no interest other than to make the thing work ?
Any real life ELS activation examples that can be shared by anyone ?
Interested in any/all combinations (such as, but not limited to ) :
"spare resevoir capacity" ?
number of application points ?
pressure at which coolant is applied ?
type of coolant ?
liquid ? solid ? mix ? gaseos ?
aircooled ?
additives ?
internal (hard surface) cooling ?
Want to move away from generalities such as "difficult", "technically demanding", "current regulations don't require..." etc...etc...and move on - there must be tons of really good technical information out there available from sources who have no interest other than to make the thing work ?
Any real life ELS activation examples that can be shared by anyone ?
maxwel - some posters on here refer to themselves as SLF so it is hardly derogatory.
I am not advocating the hover jump as standard procedure - just a consideration when the gearbox is going to seize and the sea state is too big to guarantee a safe power on ditching - will your pax survive the aircraft disintegrating and rolling over as you hit the water with your main and TR blades, possibly damaging the flotation gear as you do so? With difficulty I would suggest and then they still have to find the liferafts and get into them. On the other hand, being given a fighting chance of dropping 20 feet into the water from a hover taxi along with the rafts might improve their chances of survival. I know what I would prefer if I were the pax.
Or should you comply 100% with your rules and regs and involve them in the crash?
On the Sea King, once the ELS has operated, you must monitor the MRGB oil temp - if it gets to 150 deg C you have 5 mins to land. The same 5 mins is the estimated run-dry time at 75% Tq before seizure.
I am not advocating the hover jump as standard procedure - just a consideration when the gearbox is going to seize and the sea state is too big to guarantee a safe power on ditching - will your pax survive the aircraft disintegrating and rolling over as you hit the water with your main and TR blades, possibly damaging the flotation gear as you do so? With difficulty I would suggest and then they still have to find the liferafts and get into them. On the other hand, being given a fighting chance of dropping 20 feet into the water from a hover taxi along with the rafts might improve their chances of survival. I know what I would prefer if I were the pax.
Or should you comply 100% with your rules and regs and involve them in the crash?
On the Sea King, once the ELS has operated, you must monitor the MRGB oil temp - if it gets to 150 deg C you have 5 mins to land. The same 5 mins is the estimated run-dry time at 75% Tq before seizure.
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Crab,
On the Sea King, what's the indicator/s of uncontained oil loss - temp, quantity, both ? If 150 degrees C is the maximum allowed after ELS activation, what flight constraints (Tq/V/Alt etc....also taking into account min. requirements for Autorotation) would there be to keep it under the 150 ? if possible ?
If it is possible, what prevents continued ELS protection - lack of spare resevoir or does the heat generation just overtake the ELS cooling capability after a certain period ?
On the Sea King, what's the indicator/s of uncontained oil loss - temp, quantity, both ? If 150 degrees C is the maximum allowed after ELS activation, what flight constraints (Tq/V/Alt etc....also taking into account min. requirements for Autorotation) would there be to keep it under the 150 ? if possible ?
If it is possible, what prevents continued ELS protection - lack of spare resevoir or does the heat generation just overtake the ELS cooling capability after a certain period ?
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Why don't helicopter manufacturers build in a one way sprag clutch into the main rotor shaft, so that in the event of a gearbox seizure, the output shaft keeps turning in autorotation?
Seizure of gears is one thing, but it's the seizure of the main transmission bearings which is also a very big factor, and the use of a sprag clutch won't help that situation at all. Were sprag clutch to be contemplated, it would have to be immense to transmit all of that torque at the relatively low main rotor RPM, and thus be very heavy, and probably more failure prone than the weaknesses it was there to overcome!
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Lubricant in a gearbox is primarily for the gears, You can have sealed bearings for example. I have actually designed and built (on a smaller scale) a second stage transmission which derives it's lubrication (and cooling) from the fuel. The fuel is sprayed directly onto the gears and then presurises the caseing. I don't see why this can not be modified as an emergency solution to loss of oil. All you would need to do is fit a fuel nozzel to the gearbox casing and attach a solonoid and fuel line to a boost pump. When the pressure drops and the temp starts to rise, you activate the solenoid and spray fuel straight on to the gears untill you find somewhere safe to land.
I'll get my coat...
I'll get my coat...
Madrock, the torquemeters on the Sea King use oil pressure fed from a pump piggybacked onto the No1 MRGB oil pump and supplied from an addition to the MRGB sump at a lower level than the MRGB pumps. The tqmeter oil runs through a union which allows it to flow to the torquemeters only if there is more than 30-35psi in the MRGB system. If the MRGB loses its oil and the pressure drops, a valve in the union shuts and the Tqmeter oil is redirected to the MRGB. The indications that the ELS is operating are a caption on the CWP and the Tqmeter indications dropping to zero. There is another warning if the ELS pressure falls - the most likely reasons being that there is either a hole in the bottom of the sump or that the No1 MRGB pump has failed.
Once in ELS mode you have limited manouverability in order to keep the oil in the lower sump but at 70 kts should have a couple of hours of flying depending on the oil temp. I don't know how long the MRGB will run on ELS without failing but its a whole lot more than 10 mins 47 seconds!
Once in ELS mode you have limited manouverability in order to keep the oil in the lower sump but at 70 kts should have a couple of hours of flying depending on the oil temp. I don't know how long the MRGB will run on ELS without failing but its a whole lot more than 10 mins 47 seconds!
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Or should you comply 100% with your rules and regs and involve them in the crash?
Perhaps we need to look at a more fundamental issue, and that is should the A/C be flying is such sea states? My opinion is no.
To my knowledge we currently have only SS5 on the S-92 as that's what they show in the helo brefing video. SS6 would give us potentially a better chance of not capsizing, but in reality we would most likely still turn over.
IMO If the A/C can't land with a relatively high personnel survivability ratio either under power and/or in auto-rotation then the certification should be such that the design must have an ELS like the EC225 or the S61 to allow sufficient flight time to reach a dry landing site.
Oh, and it's not my rules and regs, it's the FAAs, perhaps they should fly in the S-92 as their regular (or very irregular as it is these days) mode of commercial transport to work.
Safe Flying
Max
I don't know how long the MRGB will run on ELS without failing