Hard Core Category A?
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Nick says
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The US Army's experience with the GE T700/CT7 engine family is very impressive: the failure rate is 1 engine failure per 500,000 hours of engine operation for engine cause, and 1:200000 for all causes (mostly pilot/fuel issues.) At 1:200,000 hours, that means a 500 aircraft civil fleet flying 1,000 hours per year per aircraft would experience 5 engine failures per year total, and 2 that were the engine's fault. If the average mission is 1 hour long, and there was an 8 second exposure time on takeoff, and a 5 second one on landing (13 seconds out of 3600) then the fleet spends 0.36% of its life in the exposure zone. This infers an engine failure every 55 years inside the exposure time!
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Am I correct to assume that an engine is more prone to failure when operating at very high power demands? Like during T/O, Ldg and hovering? On some twins the T/O Cat A profile requires 100% torque. What are the statistics for engine failure at max power? The thread was, after all, about take off and landing performance.
The Cat A profiles also require an engine to be able to produce it’s published power. How many engine changes has the Sikorsky 76C+ fleet had because of failure to meet the PPI?
My point is the engines on a lot of twins are operating very close to their design limits. Would it not make sense to have some margin in these engines in order that they are not at max chat at every take off? That margin could then be used to reduce the exposure time and reject distance in the event of OEI. I know we have OEI 30 sec and 2.5 min limits but utilizing these margins, on some twins, still requires 100’s of meters of flat unobstructed reject area and a replacement of the good engine if it all works out.
Helmut fire says
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It is simple: operate to the appropriate risk exposure you are willing to accept AND pay for. If that means you have 5 people to transport with PC1 risk, then you will have to get out of your AS355 and pay for a 412. If you have 13 people for a PC1 op, then get out of your 412 and into the 332
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Most light twin helicopters were designed to carry 12 pax. In the Corporate role most of these helicopters are fitted for just 6 pax. And still we struggle to get airborne and fly 250 miles. We don’t struggle from airfields but from the operating sites. Yes, I know, we can get rid of the leather, the bar, the A/C and all the other luxuries but the boss likes them!
And the Helicopter Manufacturers like selling them!
Mars says:
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How can the manufacturers be accused of hiding performance, don’t they publish the Category A procedure; isn’t it more that the operators, pilots and regulators are not capable of asking the correct questions and appear to be satisfied by a statement that the aircraft is Certificated to Category A.
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I did not say that they hide their performance figures. The words "Category A" sell helicopters that have insufficient performance for a lot of corporate and charter operations.
Can hardly wait for the AB139 and the Grand!
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The US Army's experience with the GE T700/CT7 engine family is very impressive: the failure rate is 1 engine failure per 500,000 hours of engine operation for engine cause, and 1:200000 for all causes (mostly pilot/fuel issues.) At 1:200,000 hours, that means a 500 aircraft civil fleet flying 1,000 hours per year per aircraft would experience 5 engine failures per year total, and 2 that were the engine's fault. If the average mission is 1 hour long, and there was an 8 second exposure time on takeoff, and a 5 second one on landing (13 seconds out of 3600) then the fleet spends 0.36% of its life in the exposure zone. This infers an engine failure every 55 years inside the exposure time!
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Am I correct to assume that an engine is more prone to failure when operating at very high power demands? Like during T/O, Ldg and hovering? On some twins the T/O Cat A profile requires 100% torque. What are the statistics for engine failure at max power? The thread was, after all, about take off and landing performance.
The Cat A profiles also require an engine to be able to produce it’s published power. How many engine changes has the Sikorsky 76C+ fleet had because of failure to meet the PPI?
My point is the engines on a lot of twins are operating very close to their design limits. Would it not make sense to have some margin in these engines in order that they are not at max chat at every take off? That margin could then be used to reduce the exposure time and reject distance in the event of OEI. I know we have OEI 30 sec and 2.5 min limits but utilizing these margins, on some twins, still requires 100’s of meters of flat unobstructed reject area and a replacement of the good engine if it all works out.
Helmut fire says
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It is simple: operate to the appropriate risk exposure you are willing to accept AND pay for. If that means you have 5 people to transport with PC1 risk, then you will have to get out of your AS355 and pay for a 412. If you have 13 people for a PC1 op, then get out of your 412 and into the 332
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Most light twin helicopters were designed to carry 12 pax. In the Corporate role most of these helicopters are fitted for just 6 pax. And still we struggle to get airborne and fly 250 miles. We don’t struggle from airfields but from the operating sites. Yes, I know, we can get rid of the leather, the bar, the A/C and all the other luxuries but the boss likes them!
And the Helicopter Manufacturers like selling them!
Mars says:
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How can the manufacturers be accused of hiding performance, don’t they publish the Category A procedure; isn’t it more that the operators, pilots and regulators are not capable of asking the correct questions and appear to be satisfied by a statement that the aircraft is Certificated to Category A.
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I did not say that they hide their performance figures. The words "Category A" sell helicopters that have insufficient performance for a lot of corporate and charter operations.
Can hardly wait for the AB139 and the Grand!
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FLI:
It was meant to be irony and make exactly the point that you were making. Why would anyone buy a helicopter without establishing exactly what it can and cannot do - performance wise? Is it that we helicopter pilots do not understand the issues?
It was meant to be irony and make exactly the point that you were making. Why would anyone buy a helicopter without establishing exactly what it can and cannot do - performance wise? Is it that we helicopter pilots do not understand the issues?
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FLI,
No, I think it is generally incorrect to assume that power margin is the way to assure engine failure reliability. Those military engines I note are used in awful environments by Army pilots and mechanics, and the stats are what they are, anyway. The way to assure flight safety is to fix the cause of accidents, FLI, not to add more engine power, but you miss all that, and fail to even consider it.
I note that the numbers don't move you at all, you gloss over the proven experience that there are about 9999 more ways to have an accident than an engine failure in a critical exposure window, ways that get us every day, in spite of the exposure windows we have.
You seem upset about all this, and blame lots of people for your plight. You have choices. Carefully note the cost to operate, the payload, range and OEI peformance, and buy what you want, of course. When you do find the perfect ground level, zero exposure helicopter, do not be disappointed to find the IFR range is a bit shy, and the costs are equivilent to those of an aircraft that carries a bunch more payload, since you are really buying a given helo, and operating it at 75% of its potential.
And for accident prevention, please buy an EGPWS with that new machine!
No, I think it is generally incorrect to assume that power margin is the way to assure engine failure reliability. Those military engines I note are used in awful environments by Army pilots and mechanics, and the stats are what they are, anyway. The way to assure flight safety is to fix the cause of accidents, FLI, not to add more engine power, but you miss all that, and fail to even consider it.
I note that the numbers don't move you at all, you gloss over the proven experience that there are about 9999 more ways to have an accident than an engine failure in a critical exposure window, ways that get us every day, in spite of the exposure windows we have.
You seem upset about all this, and blame lots of people for your plight. You have choices. Carefully note the cost to operate, the payload, range and OEI peformance, and buy what you want, of course. When you do find the perfect ground level, zero exposure helicopter, do not be disappointed to find the IFR range is a bit shy, and the costs are equivilent to those of an aircraft that carries a bunch more payload, since you are really buying a given helo, and operating it at 75% of its potential.
And for accident prevention, please buy an EGPWS with that new machine!
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Nick,
I think you already know that most corporate machines bought from Sikorsky are very well equiped with the aids to flight safety that you list. I am very grateful to Sikorsky for developing and providing them.
But, the issue here is power. Not just OEI but twin engine power.
Apart from the 'B model' the 76 just doesn't have enough power.
Eurocopter's 155 has similar limitations.
The topic of this thread was "full Cat A?" Yes, there is a market for it.
I'm just glad that another manufacturer is addressing that!
I think you already know that most corporate machines bought from Sikorsky are very well equiped with the aids to flight safety that you list. I am very grateful to Sikorsky for developing and providing them.
But, the issue here is power. Not just OEI but twin engine power.
Apart from the 'B model' the 76 just doesn't have enough power.
Eurocopter's 155 has similar limitations.
The topic of this thread was "full Cat A?" Yes, there is a market for it.
I'm just glad that another manufacturer is addressing that!
FLI touches on the points I raise quite nicely, but so far no one seems to really appreciates the full significance of onshore PC2 exposure time as a concept. We are not talking about using 332s to lift 412 cabin loads etc, we are talking about using using class 2 performance criteria to take off from a site where in fact there is no suitable reject area for a significant portion of the take off profile.
Nick, I appreciate what you are saying but please also remember that what we have to operate to, regardless of the client or operator, is some logical and justifiable arena of operation that we can justify to the proverbial "subsequent board of enquiry." Generic discussion of engine reliability does not hold sway in court; regulatory documents will.
Nick, I appreciate what you are saying but please also remember that what we have to operate to, regardless of the client or operator, is some logical and justifiable arena of operation that we can justify to the proverbial "subsequent board of enquiry." Generic discussion of engine reliability does not hold sway in court; regulatory documents will.
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FLI,
In supporting your point about Cat A, you say, "I'm just glad that another manufacturer is addressing that!" as if one or the other manufacturer is represented here, or as if one or the other does not provide what you are looking for.
Let me state again, the opinions I state here are mine, and not a line from any company. To infer otherwise is not correct, and frankly unfair.
I believe that all manufacturers provide helos that meet full Cat A from rigs, ground level heliports and anywhere else. The charts that tell you how to perform to those standards are in the flight manuals.
212man,
I guess you are bound to hard Cat A, am I right? If so, there are good procedures for this for virtually all aircraft.
In supporting your point about Cat A, you say, "I'm just glad that another manufacturer is addressing that!" as if one or the other manufacturer is represented here, or as if one or the other does not provide what you are looking for.
Let me state again, the opinions I state here are mine, and not a line from any company. To infer otherwise is not correct, and frankly unfair.
I believe that all manufacturers provide helos that meet full Cat A from rigs, ground level heliports and anywhere else. The charts that tell you how to perform to those standards are in the flight manuals.
212man,
I guess you are bound to hard Cat A, am I right? If so, there are good procedures for this for virtually all aircraft.
FLI and 212man,
My point was that performance IS linked to dollars. If you want more margin then the upgrade will cost more $$. What about all those other operators who are comfotable with the current margins due to their risk profiles? Do we make them pay for the extra margin and affect their economic viability? Surely it's better the way it is now - that those who want the extra margin due to their risk profiles CAN access it by either operating with reduced payload or buying a bigger machine. If the bosses like their leather - then that comes at a cost of exposure. They can forgo the nice bits OR buy a bigger machine: at least they have an option.
Nick, on the fuel dump I agree that the critical issue part is the dip down, and as I said, it will not solve your deck edge clearance issues, but that is, as you point out, such an insignificant period of exposure. The dump pipe WILL benefit you over the entire rest of the exposure envelope with the exception of final landing stages. So taking Nick's 0.36%, that is during 99.64% of the flight time, a fuel dump pump will be of benefit to OEI situations.
A slightly unfair use of stats, but you get the point. Maybe thats your answer FLI: stay with the leather, add a fuel dump.
My point was that performance IS linked to dollars. If you want more margin then the upgrade will cost more $$. What about all those other operators who are comfotable with the current margins due to their risk profiles? Do we make them pay for the extra margin and affect their economic viability? Surely it's better the way it is now - that those who want the extra margin due to their risk profiles CAN access it by either operating with reduced payload or buying a bigger machine. If the bosses like their leather - then that comes at a cost of exposure. They can forgo the nice bits OR buy a bigger machine: at least they have an option.
Nick, on the fuel dump I agree that the critical issue part is the dip down, and as I said, it will not solve your deck edge clearance issues, but that is, as you point out, such an insignificant period of exposure. The dump pipe WILL benefit you over the entire rest of the exposure envelope with the exception of final landing stages. So taking Nick's 0.36%, that is during 99.64% of the flight time, a fuel dump pump will be of benefit to OEI situations.
A slightly unfair use of stats, but you get the point. Maybe thats your answer FLI: stay with the leather, add a fuel dump.
Nick...we have been this way before....ok I have the OGP pie charts now and I am convinced about CFIT. Elimate that section of the chart and you take a great chunk out of your risk exposure.
Cant afford the EGPWS and dont think it is value for money in my environment where I operate literally from the beach ie 99% of my flight is over water (typical offshore oil support) where Radalt/Radar/GPS AND sound procedure should ( I say should)keep me outa the water or from hitting the rig. (is not striking the deck edge post OEI take off , sort of CFIT ?? sorry , a touch of Aussie "stirring" creeping in there.)
anyhow....
CFIT training is not readily available unless one makes up their own course and then , as far as I can see , it is still a classroom exercise. I sure would like to see what other people have done in the way of CFIT training..in the classroom/aircraft/WPB Simulator
Peter
Cant afford the EGPWS and dont think it is value for money in my environment where I operate literally from the beach ie 99% of my flight is over water (typical offshore oil support) where Radalt/Radar/GPS AND sound procedure should ( I say should)keep me outa the water or from hitting the rig. (is not striking the deck edge post OEI take off , sort of CFIT ?? sorry , a touch of Aussie "stirring" creeping in there.)
anyhow....
CFIT training is not readily available unless one makes up their own course and then , as far as I can see , it is still a classroom exercise. I sure would like to see what other people have done in the way of CFIT training..in the classroom/aircraft/WPB Simulator
Peter
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peter, peace! The right procedures and awareness should serve, but at the next equipment upgrade.....
Here is some stuff to whet the argument. I did a small design exercise, crude but to the point:
Here are three similar helos, all the same gross weight, same rotor and such, but they differ in engine power. the single has one 1300 HP engine, the middle twin has two 700HP engines and can do airport OEI procedures, and the third has two 1000HP engines, and can Hover OEI.
Note that the payload and range are vastly different, mostlt because of the extra gross weight and the extra fuel flow.
Note that the sacrifice for OEI hover is pretty big.
Here are two OGP pdf files for us to chew on, great stuff, thanks to some great helo pilots who work for the Oil Companies, and who really try to do the right thing. Each file is not quite 1 meg:
http://www.s-92heliport.com/OGP1998.pdf
http://www.s-92heliport.com/OGP2002.pdf
Here is some stuff to whet the argument. I did a small design exercise, crude but to the point:
Here are three similar helos, all the same gross weight, same rotor and such, but they differ in engine power. the single has one 1300 HP engine, the middle twin has two 700HP engines and can do airport OEI procedures, and the third has two 1000HP engines, and can Hover OEI.
Note that the payload and range are vastly different, mostlt because of the extra gross weight and the extra fuel flow.
Note that the sacrifice for OEI hover is pretty big.
Here are two OGP pdf files for us to chew on, great stuff, thanks to some great helo pilots who work for the Oil Companies, and who really try to do the right thing. Each file is not quite 1 meg:
http://www.s-92heliport.com/OGP1998.pdf
http://www.s-92heliport.com/OGP2002.pdf
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Nick, Eurocopter & Airfix
With lives at stake daily and the need to hover in all sorts of wonderful places, weather and altitudes. The big twin is going to be the choice of the SAR pilots. We would gladly sacrifice a little max range and payload (no commercial penalty for us). We are frequently exploring the boundaries of possible OEI territory for protracted periods. The great threat of CFIT for us is a very real. Escaping it on one engine that insists on taking you to the scene of the accident isn’t acceptable when an EGPWS is ‘whooping away’. Granted engine failures are rare and with the increased protection afforded by modern design, we will be better placed with the newer EC & Sikorsky products. Albeit limited for now, the SAR world is a growing market. ‘Loads of power’ please.
With lives at stake daily and the need to hover in all sorts of wonderful places, weather and altitudes. The big twin is going to be the choice of the SAR pilots. We would gladly sacrifice a little max range and payload (no commercial penalty for us). We are frequently exploring the boundaries of possible OEI territory for protracted periods. The great threat of CFIT for us is a very real. Escaping it on one engine that insists on taking you to the scene of the accident isn’t acceptable when an EGPWS is ‘whooping away’. Granted engine failures are rare and with the increased protection afforded by modern design, we will be better placed with the newer EC & Sikorsky products. Albeit limited for now, the SAR world is a growing market. ‘Loads of power’ please.
Helmet,
Fuel dump is an excellent device when a helicopter cannot meet its en-route performance - for example where it has to clear a defined obstacle (a mountain peak). Guidance on this is contained in JAR-OPS 3, IEM OPS 3.500(a)(5) - suffice to say that the fuel remaining after the dump must meet the requirement for continuation to a destination or alternate (i.e. the use of dump must be planned before take-off - as it always was when being used in the S61).
The maximum take-off mass for operations in PC2 is defined by the second segment climb (150ft/min OEI at Vy - 1000ft above the take-off point); this second segment climb is identical to the requirement for PC1. This leads to a number of observations:
Nick can provide the time/distance for most of the above but from experience, it is not likely to be more than 10 seconds from the time that all-engines-operating acceleration is commenced (be it from the hover or from the rotation point at the top of the vertical section of the take-off profile).
None of this can possibly be influenced by a fuel dump - which under civilian operating rules, cannot be commenced below 1000 ft.
Fuel dump is an excellent device when a helicopter cannot meet its en-route performance - for example where it has to clear a defined obstacle (a mountain peak). Guidance on this is contained in JAR-OPS 3, IEM OPS 3.500(a)(5) - suffice to say that the fuel remaining after the dump must meet the requirement for continuation to a destination or alternate (i.e. the use of dump must be planned before take-off - as it always was when being used in the S61).
The maximum take-off mass for operations in PC2 is defined by the second segment climb (150ft/min OEI at Vy - 1000ft above the take-off point); this second segment climb is identical to the requirement for PC1. This leads to a number of observations:
Nick can provide the time/distance for most of the above but from experience, it is not likely to be more than 10 seconds from the time that all-engines-operating acceleration is commenced (be it from the hover or from the rotation point at the top of the vertical section of the take-off profile).
None of this can possibly be influenced by a fuel dump - which under civilian operating rules, cannot be commenced below 1000 ft.
Last edited by JimL; 16th Aug 2004 at 10:12.
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Nick, you say “I believe that all manufacturers provide helos that meet full Cat A from rigs, ground level heliports and anywhere else. The charts that tell you how to perform to those standards are in the flight manuals”.
When you started this thread, you were discussing “hard core Cat A”. We now appear to be discussing the Cat A profiles that have been in helicopter manuals for many years. Most of these profiles require unrealistic onshore, off airfield, rejected T/O areas or substantial reductions in payload. Yes, as pilots, we have choices but sometimes the field conditions just do not allow us to be so flexible.
Regulations often provide no flexibility.
Even after a full site recce in preparation for a flight, conditions can change. In the UK this summer, we have had +17 one day and two days later it is +30! Welcome to England! We have to reduce payload (leave the boss’s wife behind?) or stop enroute to fuel or even cancel the flight. Hardly “all weather Cat A” that the manufactures put in their glossy publications. We can’t even fly on sunny days! Reliable door to door time is why the clients bought the machine.
With regards to limited range, most corporate clients have access to jets. They generally do not fly 400 miles by helicopter. They go by jet. Give us 2.5 hours fuel with an aux tank option to extend to 3 hours.
When Sikorsky produced the B model, they answered a lot of the performance failings of the A. Yes, the fuel consumption was a lot more and the range reduced, but Sikorsky offered an aux tank option to redress these issues and increase the flexibility of the machine. For many years the B cornered the corporate market, with clients switching from A’s and AS365’s. What a sad day it was, when Sikorsky closed the B production line and introduced the C. Some very wealthy clients are now flying in 15 year old B’s because there has been no comparable alternative, performance wise. The large twins are just too large for many public-use sites.
When Eurocopter announced the 365N4 (to become EC155B) many clients were excited. In reality, the marginal performance of the 155B was quickly addressed with the introduction of the B1. (It went from marginal to weak). Lovely aircraft to fly, just poor performance. It has Cat A certification.
Early versions of the Explorer did not have enroute Cat A performance (level sustained flight OEI) at realistic range/payload. Addressed for later versions.
We all remember early versions of the 109… full fuel no pax or full pax no fuel! Again, addressed for later versions.
It is ironic that, most ‘full pax and full fuel’ helicopters are single engine and that they require less distance for a RTO than many so called Cat A twins!
212man has highlighted the regulatory issues very well.
Helmut fire says “Maybe that’s your answer FLI: stay with the leather, add a fuel dump”. I have flown aircraft with fuel dump. How will it help during the critical T/O phase? I hardly think you would have time, or the inclination, to spray fuel during an OEI reject! If one is able to take off Cat A then, generally, one has Cat A enroute performance in most helicopter operations. It is would be useful to reduce weight for the OEI landing but the critical power phase is during T/O.
What I find most ironic from some of the postings is, now that we are close to getting “Hard Core Cat A”, people are questioning the requirement. Ask any onshore twin engine helicopter pilot operating commercially if he needs/wants more power to satisfy safety and regulations.
When you started this thread, you were discussing “hard core Cat A”. We now appear to be discussing the Cat A profiles that have been in helicopter manuals for many years. Most of these profiles require unrealistic onshore, off airfield, rejected T/O areas or substantial reductions in payload. Yes, as pilots, we have choices but sometimes the field conditions just do not allow us to be so flexible.
Regulations often provide no flexibility.
Even after a full site recce in preparation for a flight, conditions can change. In the UK this summer, we have had +17 one day and two days later it is +30! Welcome to England! We have to reduce payload (leave the boss’s wife behind?) or stop enroute to fuel or even cancel the flight. Hardly “all weather Cat A” that the manufactures put in their glossy publications. We can’t even fly on sunny days! Reliable door to door time is why the clients bought the machine.
With regards to limited range, most corporate clients have access to jets. They generally do not fly 400 miles by helicopter. They go by jet. Give us 2.5 hours fuel with an aux tank option to extend to 3 hours.
When Sikorsky produced the B model, they answered a lot of the performance failings of the A. Yes, the fuel consumption was a lot more and the range reduced, but Sikorsky offered an aux tank option to redress these issues and increase the flexibility of the machine. For many years the B cornered the corporate market, with clients switching from A’s and AS365’s. What a sad day it was, when Sikorsky closed the B production line and introduced the C. Some very wealthy clients are now flying in 15 year old B’s because there has been no comparable alternative, performance wise. The large twins are just too large for many public-use sites.
When Eurocopter announced the 365N4 (to become EC155B) many clients were excited. In reality, the marginal performance of the 155B was quickly addressed with the introduction of the B1. (It went from marginal to weak). Lovely aircraft to fly, just poor performance. It has Cat A certification.
Early versions of the Explorer did not have enroute Cat A performance (level sustained flight OEI) at realistic range/payload. Addressed for later versions.
We all remember early versions of the 109… full fuel no pax or full pax no fuel! Again, addressed for later versions.
It is ironic that, most ‘full pax and full fuel’ helicopters are single engine and that they require less distance for a RTO than many so called Cat A twins!
212man has highlighted the regulatory issues very well.
Helmut fire says “Maybe that’s your answer FLI: stay with the leather, add a fuel dump”. I have flown aircraft with fuel dump. How will it help during the critical T/O phase? I hardly think you would have time, or the inclination, to spray fuel during an OEI reject! If one is able to take off Cat A then, generally, one has Cat A enroute performance in most helicopter operations. It is would be useful to reduce weight for the OEI landing but the critical power phase is during T/O.
What I find most ironic from some of the postings is, now that we are close to getting “Hard Core Cat A”, people are questioning the requirement. Ask any onshore twin engine helicopter pilot operating commercially if he needs/wants more power to satisfy safety and regulations.
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FLI,
You have not moved from your starting point. You have not recognized the accident probabilities. or the cost in reduced range and payload of providing the amount of excess power. You have basically blamed those "misleading" manufacturers with the "glossy brochures", who seem to be unable to break the laws of aerodynamics enough to suit your needs.
But you are stating that you want, need, and insist on - full Cat A, and that is fine. You havn't accepted the fact that this will reduce other aspects of the design. You do know there is a design trade off at work, when you state, "It is ironic that, most ‘full pax and full fuel’ helicopters are single engine....."
See the above charts that explain how big-engined twins have LESS payload and range than equivilent singles.
The question on the table is not "How much OEI power do you want?" The question is, "What range, payload and safety benifits are you willing to give up to gain that OEI power margin?"
You have not moved from your starting point. You have not recognized the accident probabilities. or the cost in reduced range and payload of providing the amount of excess power. You have basically blamed those "misleading" manufacturers with the "glossy brochures", who seem to be unable to break the laws of aerodynamics enough to suit your needs.
But you are stating that you want, need, and insist on - full Cat A, and that is fine. You havn't accepted the fact that this will reduce other aspects of the design. You do know there is a design trade off at work, when you state, "It is ironic that, most ‘full pax and full fuel’ helicopters are single engine....."
See the above charts that explain how big-engined twins have LESS payload and range than equivilent singles.
The question on the table is not "How much OEI power do you want?" The question is, "What range, payload and safety benifits are you willing to give up to gain that OEI power margin?"
Last edited by NickLappos; 16th Aug 2004 at 13:15.
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Nick:
Whilst most of us can contemplate a rational discussion of PC2 v PC1 in areas where there are no third party risks; and, under some circumstances, measure the arguments for and against PC2 ‘with exposure’ - the fact that a single can lift more than a twin is a non sequitur.
We are straying from a discussion of whether it is technically feasible and economically justifiable to eliminate/limit exposure to engine failure in the take-off and landing phases to one where the flight is always exposed to an engine failure. I’m not sure FLI’s customer base will welcome the improvement in range that is based on swapping two engines for one.
As has been pointed out in recent posts, PC2 with exposure is limited in time and space and could be part of a Risk Assessed departure/arrival regime - we (with some certainty) know: the maximum extent of the exposure; the probability of engine failure; and can assess the consequences of that failure; both in immediate terms for this phase, and in the medium and long term on our business (be it a one-man-band or a multi-national oil company).
What comes as a surprise to all of us is not ‘driving looking in the rear view mirror’ but the attempt to ‘put the car into reverse’. We already know that the EC225, AS332L2, S92 and S76 can operate in PC1 and to their credit the latest marks of the EC135, A109, MD902 and AB139 can do it in spades.
FLI may have not moved from his starting point - he knows what his customer wants; what is puzzling us is the direction of your movement.
Whilst most of us can contemplate a rational discussion of PC2 v PC1 in areas where there are no third party risks; and, under some circumstances, measure the arguments for and against PC2 ‘with exposure’ - the fact that a single can lift more than a twin is a non sequitur.
We are straying from a discussion of whether it is technically feasible and economically justifiable to eliminate/limit exposure to engine failure in the take-off and landing phases to one where the flight is always exposed to an engine failure. I’m not sure FLI’s customer base will welcome the improvement in range that is based on swapping two engines for one.
As has been pointed out in recent posts, PC2 with exposure is limited in time and space and could be part of a Risk Assessed departure/arrival regime - we (with some certainty) know: the maximum extent of the exposure; the probability of engine failure; and can assess the consequences of that failure; both in immediate terms for this phase, and in the medium and long term on our business (be it a one-man-band or a multi-national oil company).
What comes as a surprise to all of us is not ‘driving looking in the rear view mirror’ but the attempt to ‘put the car into reverse’. We already know that the EC225, AS332L2, S92 and S76 can operate in PC1 and to their credit the latest marks of the EC135, A109, MD902 and AB139 can do it in spades.
FLI may have not moved from his starting point - he knows what his customer wants; what is puzzling us is the direction of your movement.
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Nick,
I think you will find that I have acknowledged the other aids to flight safety. I have acknowledged the reliability figures. I did, however, question the validity of the figures when discussing very high power demands. I have accepted that there will be a trade off in range and payload.
What I fail to understand is why we, the operators, must accept unrealistic onshore RTOD.
Most of your arguments are counter to Sikorsky ever producing the B model to provide an alternative to the ‘A’. The number of onshore operators using the ‘B’ is testament to accepting the trade-offs for more performance. (Less range, less payload, higher costs, etc.) The same argument applies to the AS365N, N1, N2 and N3. The answer, I suspect, is in response to customer requirements for more power.
Yes, I understand the penalties of a reduced RTOD. Anyone who has flown twin anything will recognise the trade-offs. It is there in the charts.
My issue is that all twin engine helicopter manufactures provide ‘Cat A’ but in a lot of circumstances the penalties are too great to operate full Cat A. We need more power to reduce/eliminate the RTOD.
Legislation, particularly operations within congested areas, requires full Cat A. On many of the helicopters today that is nigh on impossible without a very substantial reduction in payload. Perhaps, instead, we should be lobbying for a relaxation of the rules based on the industry statistics? Maybe, even, fly medium singles as they appear to answer a lot of the problems that the manufactures have in providing what we want?
Those cost conscious operators can continue to fly today’s machines. Let the corporate/onshore charter customers have an alternative to the ageing 76B!
As an aside, I have suffered 4 engine shutdowns on twins: Two in the cruise to secure an engine due to low oil pressure, one in the hover due to no oil pressure (burst pipe) and one engine explosion during take off. I have also had governor problems, which, not technically an engine failure, have resulted in limited power landings. So much for statistics! Touch wood, none on singles though!
I think you will find that I have acknowledged the other aids to flight safety. I have acknowledged the reliability figures. I did, however, question the validity of the figures when discussing very high power demands. I have accepted that there will be a trade off in range and payload.
What I fail to understand is why we, the operators, must accept unrealistic onshore RTOD.
Most of your arguments are counter to Sikorsky ever producing the B model to provide an alternative to the ‘A’. The number of onshore operators using the ‘B’ is testament to accepting the trade-offs for more performance. (Less range, less payload, higher costs, etc.) The same argument applies to the AS365N, N1, N2 and N3. The answer, I suspect, is in response to customer requirements for more power.
Yes, I understand the penalties of a reduced RTOD. Anyone who has flown twin anything will recognise the trade-offs. It is there in the charts.
My issue is that all twin engine helicopter manufactures provide ‘Cat A’ but in a lot of circumstances the penalties are too great to operate full Cat A. We need more power to reduce/eliminate the RTOD.
Legislation, particularly operations within congested areas, requires full Cat A. On many of the helicopters today that is nigh on impossible without a very substantial reduction in payload. Perhaps, instead, we should be lobbying for a relaxation of the rules based on the industry statistics? Maybe, even, fly medium singles as they appear to answer a lot of the problems that the manufactures have in providing what we want?
Those cost conscious operators can continue to fly today’s machines. Let the corporate/onshore charter customers have an alternative to the ageing 76B!
As an aside, I have suffered 4 engine shutdowns on twins: Two in the cruise to secure an engine due to low oil pressure, one in the hover due to no oil pressure (burst pipe) and one engine explosion during take off. I have also had governor problems, which, not technically an engine failure, have resulted in limited power landings. So much for statistics! Touch wood, none on singles though!
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Mars and FLI,
Sorry that my post was so misunderstood, as I have tried to show the natural progression in cost to the design from 1 to 2 smaller to 2 big engines. This is a free ranging discussion, and I am just painting the picture of how the cost builds. Note the reasonably symmetrical damage to range and payload as the single morphs to a twin with Cat A enroute to the very capable twin.
I note with both you and FLI take it as a given that more engine OEI power is better, safer and more modern, so you have made your minds up. Fair enough, but I am not sure why you believe it is safer, you never told us. That was the reason for the thread!
Sorry that my post was so misunderstood, as I have tried to show the natural progression in cost to the design from 1 to 2 smaller to 2 big engines. This is a free ranging discussion, and I am just painting the picture of how the cost builds. Note the reasonably symmetrical damage to range and payload as the single morphs to a twin with Cat A enroute to the very capable twin.
I note with both you and FLI take it as a given that more engine OEI power is better, safer and more modern, so you have made your minds up. Fair enough, but I am not sure why you believe it is safer, you never told us. That was the reason for the thread!
Nick, if you think "I'm hardcore Cat A" you want to come and look at my operating environment! Especially in an a/c that drops Cat A weight from 19.5 C at sea level, and operating in the tropics.
It's too late at night to come up with long answers to discuss the points that you and JimL et al raise, so I won't try.
Please don't raise the issue of what the military do and do not accept as a risk for AEO/OEI ops: clearly they have a different agenda and evaluate risk from a different perspective. They also have a different legal liability exposure too.
I fully accept the basic premise of PC2 ops as a concept (or I wouldn't be operating onshore with water rejects!) As I have tried to say, though, the idea of adding the exposure time concept to onshore ops is (IMHO) a backwards step that is not well understood by many pilots or, especially, the passengers.
As I understood it, the frangible parts were supposed to be on the aircraft or the landing surface; not pink, soft and within the cabin!
Anyone got any figures for a 214B with a 412 head? That must be the way forward, surely?
It's too late at night to come up with long answers to discuss the points that you and JimL et al raise, so I won't try.
Please don't raise the issue of what the military do and do not accept as a risk for AEO/OEI ops: clearly they have a different agenda and evaluate risk from a different perspective. They also have a different legal liability exposure too.
I fully accept the basic premise of PC2 ops as a concept (or I wouldn't be operating onshore with water rejects!) As I have tried to say, though, the idea of adding the exposure time concept to onshore ops is (IMHO) a backwards step that is not well understood by many pilots or, especially, the passengers.
As I understood it, the frangible parts were supposed to be on the aircraft or the landing surface; not pink, soft and within the cabin!
Anyone got any figures for a 214B with a 412 head? That must be the way forward, surely?
Last edited by 212man; 16th Aug 2004 at 21:35.
FLI: do you read the responses? Look for your point about the fuel dump on the take off part in both my posts. Is there an echo here somewhere? Whilst you highlight the lack of brainspace available to the pilot during an OEI on take off, I note that floats and contingency power limiter switches have previously been incorporated and successfully used in the past despite such brainspace issues.
The point was that the fuel dump is not effective on the rejected take off, nor after the TDP, but it is usefull for the other 99.64% by giving you a much improved power margin for your subsequent actions. You want the power margin - and a fuel dump will give that to you. Not only does it provide you better enroute planning ability due to the ability to significantly increase drift down altitudes, it provides you a significantly better margin when you try to land OEI, but it also gives you an improving margin in your OEI flyaway attempt after TDP. And if you correctly pick your flight path (avoiding disabled kindergardens and day care centres), a fuel dump below 1000ft AGL is justified in an emergency.
So, to incorporate a fuel dump into your risk management process, you will take off 60lbs heavier, thus you should climb a bit extra for the TDP, and increase LDP. For that 0.36% of the sortie you will land 60lbs heavier in your OEI situation, but between TDP and LDP you will have a power margin increase and thus a reduced risk exposure over the remaining 99.64% of the sortie, and it may even allow you to accept higher enroute LSALTs and a more direct route due to the higher drift down capability.
Or, FLI, maybe an accurate analysis of your operating environment, payload requirements, and acceptable risk exposure levels could be matched to a machine that IS capable of achieving your aims, rather than purchasing one that just doesnt do the job and trying to blame the manufacturers for insufficient power. They make machines with sufficient power for your mission profile, you just have to pay for it.
The point was that the fuel dump is not effective on the rejected take off, nor after the TDP, but it is usefull for the other 99.64% by giving you a much improved power margin for your subsequent actions. You want the power margin - and a fuel dump will give that to you. Not only does it provide you better enroute planning ability due to the ability to significantly increase drift down altitudes, it provides you a significantly better margin when you try to land OEI, but it also gives you an improving margin in your OEI flyaway attempt after TDP. And if you correctly pick your flight path (avoiding disabled kindergardens and day care centres), a fuel dump below 1000ft AGL is justified in an emergency.
So, to incorporate a fuel dump into your risk management process, you will take off 60lbs heavier, thus you should climb a bit extra for the TDP, and increase LDP. For that 0.36% of the sortie you will land 60lbs heavier in your OEI situation, but between TDP and LDP you will have a power margin increase and thus a reduced risk exposure over the remaining 99.64% of the sortie, and it may even allow you to accept higher enroute LSALTs and a more direct route due to the higher drift down capability.
Or, FLI, maybe an accurate analysis of your operating environment, payload requirements, and acceptable risk exposure levels could be matched to a machine that IS capable of achieving your aims, rather than purchasing one that just doesnt do the job and trying to blame the manufacturers for insufficient power. They make machines with sufficient power for your mission profile, you just have to pay for it.
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FLI, the A++ is, IMO, far superior to the B model. The Arriel engines give lots of power, but are very efficient. We typically burn less than 600 lb/hr, unless someone gets in a big hurry. PT6s are reliable, but they are so fuel-hungry that they don't give you much range. With only a 10,800lb MGW, we can carry almost as much as a C+, and go a long way. We can't often carry a full 12 offshore hands, but 10 is common, going well over 100NM offshore. We couldn't fit the baggage for the other two, anyway. We often have to carry baggage in the cabin, strapped into the empty seats. I wouldn't want a B model, but the A++ is so much better than the straight A that it's like a different aircraft.
Engine manufacturers have come a long way, and are producing engines with more power and lower fuel consumption than were available a few decades ago, and airframe manufacturers are using them.
Engine manufacturers have come a long way, and are producing engines with more power and lower fuel consumption than were available a few decades ago, and airframe manufacturers are using them.