American twins,Brit triple spool engines?

[unmanned transport]

Thanks for the tutorial re copying, Turbine D but all I have at the top RH corner on my dark blue toolbar is #78(Permalink) underlined.

Not:

"Wrap(quote)tags" icon
which is the third icon tab from the right (toolbar above).

[Turbine D]

unmanned transport

all I have at the top RH corner on my dark blue toolbar is #78(Permalink) underlined.

Sorry, you might try the Forum on "Computer/Internet Issues & Troubleshooting" and go to frequently asked questions. This subject is one of them.

Turbine D

[Rj111]

Sorry Rj111, I should have noted the link for the fuel burn data as it's always good to provide a link to back up ones notation(s).

Document Categories | Human and Environmental Issues | Safety Regulation

I hope the previously noted data clears up and misunderstanding with regards to fuel burn in the climb stage.

Yeah i saw these earlier and was surprised as it's inconsistent with what i've heard.

Though to counter some of the discrepancies it's worth noting that the GE90-94 is much heavier and larger than the T895. This should matter more on the light A-model 777s though.

In addition the figures for the A330 are for a more powerful version of the Trent vs the GE (I CBA to check the Pratts). If you match the rated outputs, the GE and RR at least, are comparable...

http://www.caa.co.uk/docs/702/2RR022_01102004.pdf
http://www.caa.co.uk/docs/702/4GE081_01102004.pdf

RR must be doing something right though as they're the dominant provider on the A330 (by far). And i believe they just snuck the biggest share on the 772ER/772A/773A.

RJ

[Turbine D]

gas path

One thing the RR motor has always been good at performance retention over its lifetime. The hightime engine achieved over 40k hours on wing. The mount bolts still had the boeing seal on them when it was eventually pulled for overhaul.

Occasionally, some engines and operators achieve high time on-wing, it depends on lots of factors.

GE Aviation has recognized Kenya Airways for achieving the highest time on wing for a CF6-80C2 engine in Africa. The Kenya Airways' CF6-80C2 engine was installed on a Boeing 767-300ER aircraft in 2001 and has accumulated more than 35,000 flight hours and more than 6,400 cycles without a removal.

American Airlines has set a time on wing record for a GE CF6-80C2 engine - logging more than 40,000 flight hours and nearly 10 years of continuous on-wing operation on a Boeing 767 aircraft.

[unmanned transport]

RJ111, the B744 and B767s GE/Pratt powered craft outsold RR powered ones by a huge margin. In fact BA now have more GE powered 777s than RR powered ones and that is likely to increase with more 773ERs coming into their fleet.

Cathay and Qantas fleet numbers are moving more towards GE power as well.

I bet Qantas and SIA and LH rue the day they ordered Trent engines on their A380s from the huge grounding costs that hit them. I bet Emirates and Air France were smiling every day since they could launch their A380s with EA engines.- no groundings

[Jane-DoH]

Turbine D

The question is, how do you know (100% positively sure) the bond has been made? Perhaps today there is adequate inspection technology to survey the bonds and detect abnormalities now, but then inspection technology wasn't as advanced as today. The plane never got a chance to work, the contract (funding) by the US government was cancelled before any planes were built.

They did test the engine though


unmanned transport

Because to my knowledge, the USA holds the patent on diffusion bonded titanium fan blades. I may be wrong and someone please correct me if so.

I didn't know we did

[K_9]

Bearfoil and Turbine D
Thanks for your explanations. Those both make sense, though now I have another novice question.

When a turbine is windmilling on the ground, you hear a clicking noise. I am given to understand that this is from fan blades having some play (wide tolerances) built into their installation. I thought that design feature was to allow the blades to be flush against the outside circumference of the fan shroud or duct (for want of a better term). What's to keep the fan blade tips from overheating or wearing down at a rapid rate?

[unmanned transport]

K 9, I don't mean to steal Bearfoil or Turbine Ds 'thunder' but here is my take on all that clattering going on from that big 'wheel' in the wind.

During the fan's rotation in the wind, the top blade at the 12 o'clock position
going downhill, falls over towards it's neighboring blade due to the increasing angular separation 'veeing' towards the blade tip. Each blade has what's called a mid-span snubber which is a proturberance (sp?) chordwise across the blade about an inch deep on some engines. This is the first contact point on each blade against which each snubber which makes the clattering noise. When the engine is running the centrifugal force separates each blade equidistant from it's neighbor with a clearance.

[K_9]

Interesting--I always thought it was a radial movement that was happening.

[lomapaseo]

Add in that even the rocking of the blade root in its slot may cause some noise. Curved slots solve that problem. Used to be a problem years ago so I doubt that you hear anything on the newer engines today.

[Rj111]

I was mainly speaking of the Trents. The RB211 was never intended for the 767, it was requested by BA, but its true, it was not great for the 747 and was mainly ordered by the commonwealth.

Of course airlines are now going away from the Trent for the 777, GE bought their way into the LR program. Look at the stink AA, for example, kicked up when that occured. Incidently BA have always had more GE powered 777s than RR.

QF were in part screwed by the amount of sensationalist media coverage they received. How much of world heard about N330AA? Sure they will be angered by the incident and grounding, on the other hand, you shouldn't base a decision on 1 event - the aircraft will be in service for up to 20 years.

I not interested in a pissing contest though, plenty of prestigious airlines have endorsed the Trent, and in numbers. So back to my original point, the design must be doing something right, if that thing isn't fuel consumption.

[Turbine D]

K_9

unmanned transport gave a good explanation of the fan blade clanking heard on a windmilling fan. I think, but not positively sure, this was confined to the early CF6-6 engines on DC-10 aircraft. The fan blades are intentionally not held tightly in the fan disk slots when the fan is at rest (not rotating). Upon spool-up, the centrifugal force moves the blades outward, firmly and evenly seating the fan blade upper dovetail surface to the corresponding disk lobe surface.

Now a little history: When the DC-10 was introduced to revenue service, some airports didn't have either enough jetways or ones they had couldn't be used to board passengers on DC-10s. Also, many terminals were undergoing changes/upgrades. So airlines used mobile stairs for boarding. The stairs were just in front of the engine and if it was windmilling, the clanking noise unnerved boarding passengers. So the airlines asked GE if they could stop the clanking. GE redesigned the fan blade retainer component to stop the clanking but still permit proper seating of the blade upon spool-up. This modification was introduced throughout the DC-10 fleet. This anti-clank modification feature became standard in the CF6-50 & CF6-80A/C engines.

[lomapaseo]

GE redesigned the fan blade retainer component to stop the clanking but still permit proper seating of the blade upon spool-up. This modification was introduced throughout the DC-10 fleet

Redesigned under an AD to prevent another fatal acident like National Airlines N60NA

[Turbine D]

Rj111

There are many reasons why airlines select particular engines, why air-framers offer three, two, or one brand of engines for a given aircraft, or why engine producers choose to participate in a particular aircraft program or not.

Of course airlines are now going away from the Trent for the 777, GE bought their way into the LR program.

GE had an engine (GE90-115) that was already developed and certified by EASA & FAA. Rolls Royce did not. That meant GE could and did offer a better deal to Boeing looking at both timing and total aircraft certification cost which permitted Boeing to get this plane into revenue service sooner at lower cost than other alternatives.

I was mainly speaking of the Trents.

There are various reasons an airline selects a particular engine verses another besides SPF. These reasons include but are not limited to logistics, parts commonality, historical airline/engine manufacturer relationships over time, training costs for both crews and maintenance and so forth. Trent engines will continue to be sold to those operators where it makes total economic sense, relationships continue to be good and service is good.

Engine manufacturers carefully choose which programs to offer engines to or not. For example, GE chose not to participate in the Boeing 757 program because, at the time, they did not see a payback with three engine manufacturers participating, leaving only PW & RR to compete against one another. PW & GE decided not to compete on the A-350 program, leaving RR as the sole supplier. When the final A-350 design was released, the proposed GEnx engine for an earlier A-350 design concept was withdrawn as the final A-350 aircraft competes against the Boeing 777 ER/LR (GE90-115). It is business strategy at play, sometimes you win, sometimes you lose.

How much of world heard about N330AA?

Probably not much of the world knew. It was a ground failure. In fact, it probably shouldn't have happened. On the previous flight, the pilot reported unusual in-flight engine vibration, but to the degree not requiring the engine to be shut down. So instead of removing the engine from service and investigating what the cause might be, the decision was made to take the plane to a more remote area and run the engine up to full TO thrust. The problem was the HPT disk had developed a crack at one of the disk blade posts and the rest is history. The press wasn't there as it wasn't an in-flight uncontained failure during climb-out from the airport as was the Qantas incident. By the way, N330 was written off by the insurers and was dismantled on site at LAX.

[barit1]

By the way, N330 was written off by the insurers and was dismantled on site at LAX.

I was wondering about its final disposition; I had heard at one point that AA was planning to ferry it to the Mojave boneyard. Apparently that was not feasible.

[Turbine D]

barit1

Here is a site that shows the dismantling:

http://www.aircraftrecycling.com/pp%...%20Airways.pdf

[411A]

Hmmm, much is made (it seems) that Rollers consume more fuel than their GE counterparts.

Nope, not the case, when you compare the L1011 with the DC10, at equal in-flight weights (mass, for our European friends)...

IE: the mad dog consumed 9% more, at the same enroute weight.
Confirmed by IATA data, at the time.
'Tis a fact.
Also, the three-spool Roller design was quieter, by a large measure.
Of the three American original widebody designs, only the L1011's (exclusively Rollers) were stage three compliant...at ALL weights.
(Again, 'mass', for our Euroland friends.)

I repeat....RollsRoyce manufactures mighty fine turbine engines.
So says me...with well over twenty thousand hours in RR powered airplanes.
And, at least another year to go....

NB.
Admitted however...the Rollers are significantly heavier than others, due to the three shaft design.
How much heavier?
Twenty six hundred pounds, in the case of the RR 211 series used on the B747.
But...is saved far more fuel in its years of service.

Another fact.

[Rj111]

GE had an engine (GE90-115) that was already developed and certified by EASA & FAA. Rolls Royce did not. That meant GE could and did offer a better deal to Boeing looking at both timing and total aircraft certification cost which permitted Boeing to get this plane into revenue service sooner at lower cost than other alternatives.

This is true, but RR were willing to go into the 777X program without exclusivity, unlike the other two. GE offered financial incentives to be a risk-sharing partner and that is what went ahead, in hindsight, an extremely good result for GE.

When the final A-350 design was released, the proposed GEnx engine for an earlier A-350 design concept was withdrawn as the final A-350 aircraft competes against the Boeing 777 ER/LR (GE90-115). It is business strategy at play, sometimes you win, sometimes you lose.

Just to add to that, GE were willing to power the smaller 2 A350s in its current incarnation, but Airbus wanted all 3, or nothing.

[bearfoil]

411A

You've lost me. How does comparing disparate airframes with different engines confirm fuel specifics v/v engine mfg.??

Enlighten us??

[411A]

Enlighten us??

Similar airframe configurations (trijets) at the same weight.
Quite reasonable actually, especially for the bean-counter types.