Since when the Feds require a balanced field?:suspect:
I think the gentleman is confused...
Do you mean balanced v1(since you dont use assume temp)?

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

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. :rolleyes:

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...:eek:

I guess at that point, this whole derated/reduced thrust topic goes out the window

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.

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.

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? :eek:

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.

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.

I think you've just made my case - see post #44.

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

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.

Using max take off power costs your company money. If you don't need it why waste your companies resources?

kt:

Bought a new CFM hot section lately?

(PS - Where would I go to buy "20 new A300s"? Do they still make them?)

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.

This is cognitive dissonance to many pilots, but from an engine standpoint, it's perfectly fine, even desirable; the takeoff segment serves as a "warmup" for the more demanding climb. :)

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? ;)

In ships I'm familiar with, you won't reach Max Cruise until well above optimum altitude / normal Mo.

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.

TTHR

You do relealize that at Max Cruise Thrust, the engine is at considerably lower thrust levels than at Take-off Thrust?

GF

Galaxy -

I've done my share of engine overhauls and hot sections...I'll bet you $100 you can't find one guy on Earth who's going to prove that reduced thrust departures (for two minutes) is gong to save more in engine overhaul costs then say 5000 hours of running at max cruise thrust at altitude.

I might also add that more time on the runway, gives the plane more of a chance to pick up FOD...food for thought considering the Concord was over gross...she might have missed that chunk of metal if she had been lighter...

So SSG reincarnation number 10 has finally admitted.....

But his problem is with management?

Time for his future rants to be in the Airlines, Airports and Routes forum :):)

Mutt

Mutt...there is no question that the sum total of your aviation repertoire would fall flat in a person to person debate with me. It would be a slaughter.

Do I argue that pulling back the power to 50% all day long would extend engine life...no...nor would sweeping the runway prior to all departures, or flying only in land, never near the ocean, staying away from the desert, or ice, that could crack off the inlets and dent a blade...or also keeping the 200 hour pilots you hire off the throttles so as not to overspeed inadvertently...we could also start doing oil changes after every flight...

And in the end, it's some mechanic, probably the same guy that missed the jack screw at Alaska Airlines that is checking the blades...

All right Mutt...do you get it? Do you actually fly planes to understand what I am talking about?

So there you are lined up on the runway, pulling it off as far down the runway as possible on some misguided mission to save the company money, when in fact there are a hundred other ways to do so that won't compromise safety one iota.

Seriously Mutt, just shut up..your just too stupid to talk.

@kanetoads
You may wish to lay off the skydrol cocktails mate!

So says a person who's only association with aviation is as a pax in 46C. :ugh: Worked out that rotor rotation thingy yet? :cool:

You can find me at the Dubai Airshow next week, either at the Boeing or Gulfstream chalets, come over and chat, we will have immediate access to representatives who can validate your "concepts" of large aircraft operations.......:ok::ok:

Mutt

@ TakeTheHighRoad.

If you looked at any metallurgical paper such as DoITPoMS - TLP Library Creep Deformation of Metals - Effects of stress and temperature, you'd see that the creep rate of a turbine blade will have an exponential dependence on temperature.

It pays to run the engines as cool as possible with any power setting greater than MCT.

So true to form, once you are exposed as having no technical knowledge of large aircraft performance or operations, you immediately turn to insults.... usually resulting in a forum ban........

I wonder who you will come back as next time :{:{:{

Mutt

TakeTheHighRoad aka SSG, take a hike tosser, mutt is a highly accomplished aviator, along with many others you take exception to - galaxy flyer, con-pilot etc. You have proven time and time again under your many guises that you know absolutely zip when it comes to aviation, and have absolutely nothing substantive to contribute to discussions.

Figured out that rotor direction thingy yet?

moving swiftly on
 

Brian

Well said. By the way you don't still have a copy of my RR Merlin spreadsheet do you? Mislaid mine.

Well at the end of the day the real justification is that you guys do what your told...it just makes you guys feel better when pulling the gear up over the fence that you have 'just cause'.

It's the same mentality of a guy that sits down and eats three cheesecakes, obviously overweight...tells everyone he's got a thyroid problem.

Problem? Who has a problem?

I think it's just fine that you run rated thrust on every takeoff, because that's more spare parts revenue for my employer (from whom I've retired, but I still collect dividends from). That's easy money for us. :)

Just don't think that attitude will find traction in an industry that survives or perishes on its avoidable costs.

barit1,

You had me worried for a moment, until I did a re-read of your tounge in cheek remark, which, to me, ends this whole discussion. If an engine manufacturer just loves full thrust takeoffs in the name of increased revenue for them from spare parts sales, that says it all:ok:

Doubters should take a good look at an Engine stress Vs Engine life graph which pretty much says it all, reduce the thrust (if possible), and increase the engine life and likelyhood of Engine failure DRAMATICALLY. I don't have the facility to post diagrams, but will have it done by a fellow prooner (my son). That one diagram is worth a thousand words.

TakeTheHighRoad, SSG, and all of your other mutant offspring, It seems that you have taken issue with one of the regular contributors here, who is part of the back-bone of PPRune. May I refer you to a contributor who:-

(1) Has an incredibly long career as a Professional Pilot and Performance Engineer for a MAJOR airline,

(2) Has vast experience on small to VERY large aircraft in that, and other airlines,

(3) Receives Boeing and engine manufacturer data directly from them, and returns it if faulty, which these major manufacturers accept,

(4) Very gracefully accepts correction if he makes an extremely rare mistake,

(5) Is an absolute gentleman of unparalleled restraint when insulted by FOOLS. He obviously belongs to the school of thought that if an insult is given, but not accepted, the insult remains with the person initiating it.

I have learned a lot from his sharing his considerable experience.

He goes by the name of Mutt on these forums:ok:

On a personal take, most discussion regarding use of Flex/Reduced thrust centres on cost saving. It's a very valid and truthful point, but, even if it were not, I would (and do) use Flex/Reduced thrust for every Takeoff possible in the interests of safety, such safety enhancement emanating from very significantly reduced engine stress, thus leading to a very significantly reduced probability of engine failure:ok:

This was an otherwise good thread for all pilots. Unfortunately it has been soiled by you, TakeTheHighRoad, SSG, and all of your other mutant offspring. Do us all a favour and ... or, as my good colleague Jack Macdonald once observed to me many decades ago .. in respect of a court martial in which he was a material witness .. "He said 'Go away, or words to that effect, Sir". (I have to play with extreme even-handedness) - JT

Now, let the sane debate continue.........

Best Regards,

Old Smokey (who does not share Mutt's degree of restraint.:)

Old Smokey:

Well, I didn't intend my post tongue-in-cheek - I was perfectly serious. It's only a few pfennigs in my pocket, but it somehow feels better when it's coming from hot jock like kt. :E

What I would like to know is how the airlines can run their cycle limited components to 4 and 5 times the component cycles of GA Jet Engines.

Here it is....SSG V10. :=


For one thing, GA engines are not designed for the use airline engines are, think of it, how mang GA engines will see 16,000 hours?

GF

Galaxy, I am all ears to how you and experts are going to demonstrate that an inner turbine wheel on a JT15D is some how manufactured to a lower standard then say your typical airline engine.

That's good to know though...the next time I do an engine overhaul I can now can call up Garret, Pratt, or Rolls and say...

'You know I heard on the internet that I can get a turbine wheel that will go 20000 cycles instead of the 5000 cycle one your trying to sell me'. and the response will be..

'Oh, yeah, that's the extra super duper turbine wheel that we only sell to the airlines, would you like one?

Could it be that the designers fashion an engine to meet the expected usage pattern - metallurgy (single crystal blades), plasma coating blades with exotic materials, cooling (plasma drilling passages, casting blades with passages), active blade clearance. Technology costs money, and the usage pattern of JT15 powered aircraft was probably designed with 500 hours per annum in mind. Calendar time likely to come up before hours or cycles. Could it be? Nah, not a chance.

Formula One guys should buy their tyres at Harrys Cheap Tyres, they do the same job, both just bits of rubber on a wheel.

Brian, we could speculate all day long that airline engines have more unobtanium in them then GA jet engines.

But I think those in the know here, are very well aware that the answer to this question lies in two turbine wheels made to spec...and one operator gets to do 'this' and another operator gets to do 'that'.