Reduced Versus Full Takeoff Thrust
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Since when the Feds require a balanced field?
I think the gentleman is confused...
Do you mean balanced v1(since you dont use assume temp)?
I think the gentleman is confused...
Do you mean balanced v1(since you dont use assume temp)?
Last edited by de facto; 31st Oct 2011 at 09:42.
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Thread ender - So does anyone use reduced thrust without the financial incentive of extending engine overhaul times, ergo for the express and sole purpose of 'enhancing safety by putting less stress on the engines'? Aside from a few pilots I have known that don't push the engines up at alt during cruise, I haven't seen nor hear of it.
Having read SSG V1 thru V9 before, I'm a consciousness objector for this thread. As is, I think, another well-known denizen of this forum.
GF
GF
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There is a simple economic reason for kt's point of view.
In an airline operation, engine maintenance cost is a very significant part of the corporation's total cost structure, and so flex thrust makes much sense. Costs make the difference between profitability and bankruptcy.
In kt's world, the engine maintenance cost (in fact the whole bizjet operation) is a very small part of the corporation's total cost. If engine maintenance cost were zero, or if it were tripled, wouldn't make a pfennig difference in the corporation's EPS.
In an airline operation, engine maintenance cost is a very significant part of the corporation's total cost structure, and so flex thrust makes much sense. Costs make the difference between profitability and bankruptcy.
In kt's world, the engine maintenance cost (in fact the whole bizjet operation) is a very small part of the corporation's total cost. If engine maintenance cost were zero, or if it were tripled, wouldn't make a pfennig difference in the corporation's EPS.
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Mutt: Not at all...though some of the things we do I question. Although the thought always does cross my mind when I don't have a parachute strapped to me & I'm not sitting in the cockpit - I hope these guys are on top of their game. I have seen it once (only once) where they weren't. I was sitting by the wing and the flaps started to extend after the power was pushed up for takeoff. Scary...
I guess at that point, this whole derated/reduced thrust topic goes out the window
I guess at that point, this whole derated/reduced thrust topic goes out the window
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TakeTheHighRoad:
I know of one engine OEM that very pointedly says that derate/flex has no effect on safety, but is strictly an economic issue. I think this is the general industry attitude, although some crews believe safety (failure rate) is enhanced with reduced thrust.
There is another point to be made: Flex thrust results in operating at a more constant thrust/weight ratio. This may be trivial or not. It means that the TO roll time to V1 & Vr is more constant, and the pace of cockpit activity isn't hurried one day and leisurely the next. Maybe the human factors crew can comment.
I know of one engine OEM that very pointedly says that derate/flex has no effect on safety, but is strictly an economic issue. I think this is the general industry attitude, although some crews believe safety (failure rate) is enhanced with reduced thrust.
There is another point to be made: Flex thrust results in operating at a more constant thrust/weight ratio. This may be trivial or not. It means that the TO roll time to V1 & Vr is more constant, and the pace of cockpit activity isn't hurried one day and leisurely the next. Maybe the human factors crew can comment.
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Barit - If I was allowed to overhaul on condition, you could bet i would do everything to not only get the overhaul cost down, but not have to go through it all all. Having done my share of overhauls, hot sections, and a back and forth with the factory over a bearing failure...it's a pain...really is. But I am just not sure how much grass at the end of the runway I would want to just fly over to put another dollar in the boss's pocket.
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Are you saying your airplane won't perform OEI like the AFM says it should? Are you saying bearing failures are a big issue on your engine?
I note that loss of thrust on one is not an emergency in an airliner AFM. And further, engine reliability is such that the typical airline pilot would statistically fly two or three careers before encountering an engine failure during takeoff segment.
I note that loss of thrust on one is not an emergency in an airliner AFM. And further, engine reliability is such that the typical airline pilot would statistically fly two or three careers before encountering an engine failure during takeoff segment.
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Barit - I'm just joking. If corporate made us use reduced thrust to save a buck, it would be pretty funny..guys would probably just be pulling it off at the end.... As far as engine failures go, I've had 4 so far...personally I think it's inevitable that a pilot that flies enough is going to see some malfunctions, all over the plane. Maybe it's because I deal directly with the owners...it just seems comical to consider departing farther down the runway, so that we can make the guy a little richer.
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By personal experience, Your CO. is ACMI, your Aircrft and Engines are leased. As a result, your customer rarely fills your aircraft to less than MGW and by personal experience rounds down the numbers. That was a different life that resulted in many full thrust T/O's
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Well at issue really...is to separate those that have actually gone through the overhaul process vs those who believe what they are told, then run around and regurgitate as gospel.
But I suspect the same people who will argue for reduced power departures are the sames ones who bought it hook line and sinker that taking pillows and peanuts off of Delta flights was what was REALLY needed to save the airline.
If you haven't seen the numbers first hand, spent the money, actually been in charge of this stuff, then your simply going by what your chief pilot/department manager is telling you...
Anyone know what the actual fuel cost is, how about insurance, what about the gate fees, how about the real cost of the aircraft...
It's a tough sell to convince me that your company is going under with out the use of Flex when you just bought 20 new A300s. Just sayin.
But I suspect the same people who will argue for reduced power departures are the sames ones who bought it hook line and sinker that taking pillows and peanuts off of Delta flights was what was REALLY needed to save the airline.
If you haven't seen the numbers first hand, spent the money, actually been in charge of this stuff, then your simply going by what your chief pilot/department manager is telling you...
Anyone know what the actual fuel cost is, how about insurance, what about the gate fees, how about the real cost of the aircraft...
It's a tough sell to convince me that your company is going under with out the use of Flex when you just bought 20 new A300s. Just sayin.
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kt:
Bought a new CFM hot section lately?
(PS - Where would I go to buy "20 new A300s"? Do they still make them?)
It's a tough sell to convince me that your company is going under with out the use of Flex when you just bought 20 new A300s. Just sayin.
(PS - Where would I go to buy "20 new A300s"? Do they still make them?)
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No, they dont, but you can buy refurbished A300-freighters from EADS.
There are big differences between airline and GA business models. A shorthaul aircraft in the airline business needs to fly around 3500 hours a year to earn its keep, a longhaul aircraft around 6000 hours a year. Most GA aircraft do not more than 500 hours a year and many do less. Reliability is a key factor for airlines as they cannot spare extra ground time without schedule problems, therefore high reliability is one of the main selling points of airline aircraft. GA aircraft have a lot more ground time which can be used for maintenance and usually do not reach the same reliability numbers as airline aircraft which isn't really a problem after all with all that much spare ground time.
That said most airlines pamper their engines. For example we wash engines around every other week during scheduled maintenance, of course continous monitoring is absolutely standard with downlinking engine parameters from every few minutes to several times an hour via ACARS/datalink and rigorous maintenance action. As changing an engine is often times faster (around 6 hours for a PW4000) than doing extensive maintenance on the wing we are not against taking them off, however a complete overhaul is a rare thing, it is usually just a parts change. That requires several spare engines of course, but again, that is standard airline operation anyway.
And of course reduced thrust when you do not need full thrust is another measure to increase engine life and at the same time reduce maintenance cost. If full thrust is needed we use it of course, that is why we bought it in the first place. We do use full climb thrust now wherever usefull (doesn't really help with a low level off altitude like london area departures) to save on fuel, so reduced thrust is only used for take offs up to 1000ft AGL. Of course that means nearly every time that climb thrust "reduction" is actually an increase in thrust.
There are big differences between airline and GA business models. A shorthaul aircraft in the airline business needs to fly around 3500 hours a year to earn its keep, a longhaul aircraft around 6000 hours a year. Most GA aircraft do not more than 500 hours a year and many do less. Reliability is a key factor for airlines as they cannot spare extra ground time without schedule problems, therefore high reliability is one of the main selling points of airline aircraft. GA aircraft have a lot more ground time which can be used for maintenance and usually do not reach the same reliability numbers as airline aircraft which isn't really a problem after all with all that much spare ground time.
That said most airlines pamper their engines. For example we wash engines around every other week during scheduled maintenance, of course continous monitoring is absolutely standard with downlinking engine parameters from every few minutes to several times an hour via ACARS/datalink and rigorous maintenance action. As changing an engine is often times faster (around 6 hours for a PW4000) than doing extensive maintenance on the wing we are not against taking them off, however a complete overhaul is a rare thing, it is usually just a parts change. That requires several spare engines of course, but again, that is standard airline operation anyway.
And of course reduced thrust when you do not need full thrust is another measure to increase engine life and at the same time reduce maintenance cost. If full thrust is needed we use it of course, that is why we bought it in the first place. We do use full climb thrust now wherever usefull (doesn't really help with a low level off altitude like london area departures) to save on fuel, so reduced thrust is only used for take offs up to 1000ft AGL. Of course that means nearly every time that climb thrust "reduction" is actually an increase in thrust.
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Of course that means nearly every time that climb thrust "reduction" is actually an increase in thrust.
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Ok, then it follows that iif you guys pull it back for the two minutes that you could go max thrust...then I will assume that for the other 20000 hours at altitude, your pulling back the power from max cruise as well... Right? 
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Well, see Barit, that's where your argument comes undone.
Keeping costs down in a flight operation is a matter of containing costs in a number of areas...
So pulling back on the power for departure might extend engine overhaul times, but flying around at altitudes not optimal for the trip burns more fuel right now...we could go into insurance, training costs...and for me...pointless..
Reminds of when the ex CEO of United blew 100 million on non refundable aircraft orders and almost bankrupted the company...
I won't argue that power reduction can save overhaul costs, but chances are, that procedure in an organization that is probably bleeding money in other areas is like the kid who put his finger in the dam.
Feel free to fly it to fence if you want, but unless I was convinced that the rest of the organization was as motivated in their efforts to save money, I wouldn't put any more runway behind me then necessary.
Keeping costs down in a flight operation is a matter of containing costs in a number of areas...
So pulling back on the power for departure might extend engine overhaul times, but flying around at altitudes not optimal for the trip burns more fuel right now...we could go into insurance, training costs...and for me...pointless..
Reminds of when the ex CEO of United blew 100 million on non refundable aircraft orders and almost bankrupted the company...
I won't argue that power reduction can save overhaul costs, but chances are, that procedure in an organization that is probably bleeding money in other areas is like the kid who put his finger in the dam.
Feel free to fly it to fence if you want, but unless I was convinced that the rest of the organization was as motivated in their efforts to save money, I wouldn't put any more runway behind me then necessary.