Farsight
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GE9X Record Breaker

Wed Feb 27, 2019 8:32 pm

Hi All

Feels good to finally join after a decade+ of observation!

My question is...how likely is it that GE will attempt to beat the GE90 thrust record any time soon? Could a test GE9X be 'turned up to 11' and put out a few 1000lbs extra...just for bragging rights of course!

Many thanks.
 
PerVG
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Re: GE9X Record Breaker

Wed Feb 27, 2019 9:05 pm

Not very likely, IMHO.
What would be the point of it, anyway? They already have the record, with the "bragging rights" that come with it. And that record came from normal testing, not from any intentional "record run".
As for the GE9X, it targets a lower thrust point than the GE90, at least for now. I don't see it breaking any thrust records in testing.
It should break efficiency records, tho, which are far more important. ;)
 
strfyr51
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Re: GE9X Record Breaker

Wed Feb 27, 2019 10:50 pm

PerVG wrote:
Not very likely, IMHO.
What would be the point of it, anyway? They already have the record, with the "bragging rights" that come with it. And that record came from normal testing, not from any intentional "record run".
As for the GE9X, it targets a lo"wer thrust point than the GE90, at least for now. I don't see it breaking any thrust records in testing.
It should break efficiency records, tho, which are far more important. ;)

The question is NOT how much thrust it CAN Generate? But for how many Takeoffs and for how many Hours it can generate it in Cruise before it deteriorates.
With Engines flying in ."On Condition" limits? you'd want the engine to generate power for Years with no problems.
There's no point in Over Boosting an engine for a thrust record. Especially since Takeoff Power is only for 5 Minutes. And? An Overhaul could cost $1M to repair the damage. IF it can be repaired! Unless however? It's your Money??
 
stratclub
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Re: GE9X Record Breaker

Wed Feb 27, 2019 11:22 pm

The 747-8 could easily take off at over a million pounds but to the best of my knowledge Boeing never has because MTOW is certified at 875,000 pounds. They certainly could easily do it except bragging rights have no place in something as conservative as aviation.

Once the flight envelope etc is defined you just plain old do not intentionally exceed it. Like I said, aviation in reality is a very conservative endeavor. In the jet age, Boeing and if my info is correct Airbus have never lost an aircraft during validation testing. When you consider the extent of testing and the performance modern airliners are capable of, that stat is pretty amazing.
 
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Stitch
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Re: GE9X Record Breaker

Wed Feb 27, 2019 11:30 pm

stratclub wrote:
The 747-8 could easily take off at over a million pounds but to the best of my knowledge Boeing never has because MTOW is certified at 875,000 pounds.


Current MTOW for the 747-8 Intercontinental is 975,000 pounds (442,000kg) and for the 747-8 freighter it is 987,000 pounds (448,000kg).
 
Farsight
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Re: GE9X Record Breaker

Wed Feb 27, 2019 11:30 pm

Thanks for the replies..

Then how was the 127,000lbs figure achieved during GE90 testing?

The design brief was fixed at 115,000...so why did they exceed it so dramatically? What was the purpose?
 
stratclub
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Re: GE9X Record Breaker

Thu Feb 28, 2019 3:39 am

Stitch wrote:
stratclub wrote:
The 747-8 could easily take off at over a million pounds but to the best of my knowledge Boeing never has because MTOW is certified at 875,000 pounds.


Current MTOW for the 747-8 Intercontinental is 975,000 pounds (442,000kg) and for the 747-8 freighter it is 987,000 pounds (448,000kg).

Well, I am retired so all I have to go by is crappy old Wikipedia. Do you agree with the intent of my post?
 
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TheFlyingDisk
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Re: GE9X Record Breaker

Thu Feb 28, 2019 5:29 am

stratclub wrote:
The 747-8 could easily take off at over a million pounds but to the best of my knowledge Boeing never has because MTOW is certified at 875,000 pounds. They certainly could easily do it except bragging rights have no place in something as conservative as aviation.


They actually did do this during testing

https://www.youtube.com/watch?v=IzAwWdIivVg

https://www.airspacemag.com/flight-toda ... -68322626/
I FLY KLM+ALASKA+QATAR+MALAYSIA+AIRASIA+MALINDO
 
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AirKevin
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Re: GE9X Record Breaker

Thu Feb 28, 2019 6:54 am

stratclub wrote:
Stitch wrote:
stratclub wrote:
The 747-8 could easily take off at over a million pounds but to the best of my knowledge Boeing never has because MTOW is certified at 875,000 pounds.


Current MTOW for the 747-8 Intercontinental is 975,000 pounds (442,000kg) and for the 747-8 freighter it is 987,000 pounds (448,000kg).

Well, I am retired so all I have to go by is crappy old Wikipedia. Do you agree with the intent of my post?

To be fair, 875,000 would be for the 747-400, so that number didn't completely come out of nowhere, either.
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zeke
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Re: GE9X Record Breaker

Thu Feb 28, 2019 7:06 am

Farsight wrote:
Thanks for the replies..

Then how was the 127,000lbs figure achieved during GE90 testing?

The design brief was fixed at 115,000...so why did they exceed it so dramatically? What was the purpose?


I do not know specifics, my guess is the engine has additional built in margins so when thrust bumps or hot and high conditions are there they can maintain full thrust up to a higher density altitude.
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WIederling
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Re: GE9X Record Breaker

Thu Feb 28, 2019 9:01 am

Farsight wrote:
Thanks for the replies..

Then how was the 127,000lbs figure achieved during GE90 testing?

The design brief was fixed at 115,000...so why did they exceed it so dramatically? What was the purpose?


Testing ;-?
For a range of performance aspects you can swap out time limits for other params expanding limits.
something like $runtime_life * $%overthrust ~= constant
Murphy is an optimist
 
gloom
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Re: GE9X Record Breaker

Thu Feb 28, 2019 10:29 am

[quote="zeke"
I do not know specifics, my guess is the engine has additional built in margins so when thrust bumps or hot and high conditions are there they can maintain full thrust up to a higher density altitude.[/quote]

100% true.

Max thrust is something sustainable for a number of minutes/hours (would need to look for exact numbers on certification requirements).

Max N1/N2 is higher than that, it indicates "never exceed" conditions. If (and when) they tested max N1/N2, they go above max thrust conditions. Since thrust is generally higher with higher rpm, they achieved more than nominal thrust.

Cheers,
Adam
 
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Pudelhund
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Re: GE9X Record Breaker

Thu Feb 28, 2019 10:35 am

I am not very familiar with engines, so why would you need a GE9X if it carries the 777-9 with less thrust than the GE90 for the 77W? Is it just efficiency and longevity? TOGA power requirements?
 
RJMAZ
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Re: GE9X Record Breaker

Thu Feb 28, 2019 11:09 am

All engines and structures in testing would exceed their normal design limit. This is done to help certify the actual limit in service.

Overloading something is also a great way at finding the weakest point of a design.
 
Farsight
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Re: GE9X Record Breaker

Thu Feb 28, 2019 1:59 pm

Thanks for the replies...

I think we can safely assume then that the GE9X has been heavily overloaded during testing, way past the 105,000lb rating. Anyone care to speculate on any maximum thrust figures?
 
PerVG
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Re: GE9X Record Breaker

Thu Feb 28, 2019 2:35 pm

The GE90's 127k lb figure was obtained during mandatory triple red line (maximum N1, N2 and EGT values) testing for certification.
Source: https://www.geaviation.com/press-releas ... tes-far-33

As for what the GE9X might do under the same conditions, if it gets the same 110% of rated thrust it will reach about 116k lb...
 
stratclub
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Re: GE9X Record Breaker

Thu Feb 28, 2019 7:09 pm

So much for my perception. A million plus is not that much over the Certified MTOW of the 747-8. You might say that in normal service, the aircraft will never exceed MTOW. When the -8 was doing validation testing, I was on the 787 so my observation for the -8 are second hand at best.
 
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AirKevin
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Re: GE9X Record Breaker

Fri Mar 01, 2019 12:37 am

Pudelhund wrote:
I am not very familiar with engines, so why would you need a GE9X if it carries the 777-9 with less thrust than the GE90 for the 77W? Is it just efficiency and longevity? TOGA power requirements?

I'm guessing fuel efficiency of the newer engine.
Captain Kevin
 
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Stitch
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Re: GE9X Record Breaker

Fri Mar 01, 2019 1:06 am

Pudelhund wrote:
I am not very familiar with engines, so why would you need a GE9X if it carries the 777-9 with less thrust than the GE90 for the 77W?


As AirKevin notes, the GE9X will be significantly more fuel efficient (especially at cruise) than the GE90 so it will contribute greatly to the 777-9's overall fuel efficiency improvements over the 777-300ER.
 
LH707330
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Re: GE9X Record Breaker

Fri Mar 01, 2019 5:04 am

stratclub wrote:
Stitch wrote:
stratclub wrote:
The 747-8 could easily take off at over a million pounds but to the best of my knowledge Boeing never has because MTOW is certified at 875,000 pounds.


Current MTOW for the 747-8 Intercontinental is 975,000 pounds (442,000kg) and for the 747-8 freighter it is 987,000 pounds (448,000kg).

Well, I am retired so all I have to go by is crappy old Wikipedia. Do you agree with the intent of my post?

I'm pretty sure that both are 987k, whether the operators bought those weights is another question: https://www.flightglobal.com/news/artic ... ts-367030/
 
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Stitch
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Re: GE9X Record Breaker

Fri Mar 01, 2019 6:11 am

LH707330 wrote:
I'm pretty sure that both are 987k, whether the operators bought those weights is another question: https://www.flightglobal.com/news/artic ... ts-367030/


You are correct. Was looking at the 747-8F ACAP and they had those two values listed for the freighter and I thought the left was the -8I and the right the -8F. The -8I is on a separate page and it is also 987klbs / 448t.
 
mickrussom
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Re: GE9X Record Breaker

Sun Jun 23, 2019 12:53 am

Farsight wrote:
My question is...how likely is it that GE will attempt to beat the GE90 thrust record any time soon? Could a test GE9X be 'turned up to 11' and put out a few 1000lbs extra...just for bragging rights of course!


The GE9X has exceeded the GE90-115B records but GE has kept them private thus far according to Ted Ingling GE Aviation’s GE9X program manager. The previous GE90-115B record is 127,900 lbf (569 kN).


www ainonline com / aviation-news / air-transport / 2019-06-11 / ge9x-flight-testing-evaluates-possible-future

Ted Ingling, GE Aviation’s GE9X program manager:

One GE9X performance measure of which GE is fully confident is the engine’s ability to provide its maximum rated thrust. Ingling revealed that, during ground runs on very cold days in which the fan was run up to rotation speeds well within its design envelope and with all temperatures and pressures “margined” within production-engine performance parameters, the high air density led to the development engine producing thrust levels far beyond the GE9X’s 105,000-pound design rated maximum thrust level. Those tests showed that the GE9X “is not airflow-limited,” he said. “The flow at the inlet and through the nacelle is sufficient and the fan can pump it” through the engine at the rate required to achieve rated maximum takeoff thrust.

The GE9X cold-day tests even produced thrust levels well beyond the 115,000-pound maximum thrust rating of the GE90-115B, today the most powerful jet engine in the world, Ingling revealed. While he won’t confirm the actual thrust levels the engine achieved until GE validates the results, it appears possible that on some of those cold-day runs the GE9X achieved a thrust level beyond even the 127,900-pound maximum the GE90-115B achieved during cold-day testing. Today that level remains the highest thrust level ever officially produced by a jet engine, but “for sure there will be a new record in the books soon,” Ingling told AIN.
 
mickrussom
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Re: GE9X Record Breaker

Sun Jun 23, 2019 12:55 am

PerVG wrote:
Not very likely, IMHO.

Its very likely. Ted Ingling (GE Aviation’s GE9X program manager ) said the GE9x has unofficially beaten the GE-115B record thrust in cold weather triple red line conditions and stated a new record for the books will be forthcoming. He stated the numbers will remain unpublished until fully evaluated.
 
mickrussom
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Re: GE9X Record Breaker

Sun Jun 23, 2019 1:08 am

Farsight wrote:
Then how was the 127,000lbs figure achieved during GE90 testing?

Triple red line testing of the engine in a test bed with a potentially sacrificial SETT (second engine to test - after certification this will be the reference design).

GE Aviation ran the GE90-115B ran for approximately 60 hours at triple-red-line conditions (maximum fan speed, core speed and exhaust gas temperature) to evaluate the engine at its operational limits and demonstrate its capability beyond the most extreme operating conditions.

Nobody would ever want to run engines that cost almost 30 million (and several million to overhaul) anywhere near that level. Most takeoffs are derated for various reasons including wear and tear. What GE is trying to do and prove by being able to operate so much higher than max thrust is to make the number of hours the engine can stay on the wing. The current record holder for hours on the wing is the RB211-535E4 which achieved 40,000 hours. This type of durability and reliability is like gold to operators.

The GE9X, according to Ted Ingling, is supposed to break the GE90-115B records in triple redline / cold weather conditions - but the 777X needs less thrust while being larger due to the redesigned wing. The GE9X could produce more power than the 115B (its a larger fan diameter GE-115B is 128 inches, the GE9X is 132 in). The GE9X has changed the fan blades to have steel leading edges and glass-fibre trailing edges to better absorb impacts, deal with FOD, with more flexibility than carbon fiber.

The GE9X will be 10% more efficient than any of the previous GE90 series.

The new GE9X engine has been designed with durability, reliability and efficiency in mind along with the 777X new wing (much larger - this is why the wingtips fold) more weight and passengers will go further on less thrust and the newer engines, despite being larger, will run with less operating thrust to try and maximize time on the wing and time between overhauls while saving 10% or more in fuel.
 
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Starlionblue
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Re: GE9X Record Breaker

Sun Jun 23, 2019 1:53 am

stratclub wrote:
The 747-8 could easily take off at over a million pounds but to the best of my knowledge Boeing never has because MTOW is certified at 875,000 pounds. They certainly could easily do it except bragging rights have no place in something as conservative as aviation.

Once the flight envelope etc is defined you just plain old do not intentionally exceed it. Like I said, aviation in reality is a very conservative endeavor. In the jet age, Boeing and if my info is correct Airbus have never lost an aircraft during validation testing. When you consider the extent of testing and the performance modern airliners are capable of, that stat is pretty amazing.


For the record, Airbus did lose an A330 in pre-delivery testing. https://en.wikipedia.org/wiki/Airbus_Industrie_Flight_129
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
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Francoflier
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Re: GE9X Record Breaker

Sun Jun 23, 2019 3:25 am

It's interesting that they would break thrust records with the GE9X.

My understanding of the whole 777X idea was that they would keep the same MTOW and give it a new wing to improve efficiency. They were essentially trying to reduce the required thrust to lift the same weight, and through this reduce fuel consumption.

The GE90-115 was that powerful partly because it needed to compensate for a severely underwinged airplane.

I'd say the records that everybody in the industry want to see broken are SFC figures, not thrust.
If the engine is capable of so much more thrust than required, what does it mean for the operators? Longer on-wing times through increased margins? Higher flat-rated temperature/altitude? The possibility of higher than required fuel burn? A combination of all of the above?
(Genuine question...)
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Faro
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Re: GE9X Record Breaker

Sun Jun 23, 2019 6:51 pm

Funny that they should do this when the engine is rated at circa 105K lbs thrust for operational use. My guess is they simply did it because they could.

I severely doubt whether GE will provide a thrust bump option up to that level of thrust, among others because of Mvca / Mvcg considerations.


Faro
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mickrussom
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Re: GE9X Record Breaker

Sun Jun 23, 2019 9:30 pm

Faro wrote:
I severely doubt whether GE will provide a thrust bump option up to that level of thrust, among others because of Mvca / Mvcg considerations


I don't think anyone expects to get more than the stated 105000 lb/thrust. This engine might be unique for the operators because 105000 is likely be a breeze for the engine to produce. Imagine an engine that can be operated at 100% with no risk of wear, etc. Imagine an engine in the 105000 lb thrust class that can hang on the wing for tens of thousands of hours. Imagine strapping this engine, with larger, stronger and more flexible fan blades to a plane with a much larger wing that needs less thrust to carry more weight and passengers around... That engine for all intents is the GE9x.

I'm not sure why having an engine "under-rated" for its maximum thrust is being perceived this way. Clearly GE thinks that the engine can go more thrust, even more than the GE90-115B - but there is no application for it - it already can be applied to an aircraft that can easily seat over 420 passengers and go 7500 - 8700 nmi ((exit limit 450, could be over 550 if Boeing put back the Type A exist doors seen in the 300ER, but Boeing decided nobody will need more than 450 passenger seats on an AC like this))

If GE can demonstrate huge fuel economy increases and huge maintenance and reliability increases with many thousands or tens of thousands of more on-wing time and time between major services/overhauls this should appeal to everyone.
 
PerVG
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Re: GE9X Record Breaker

Tue Jun 25, 2019 12:09 pm

mickrussom wrote:
Its very likely. Ted Ingling (GE Aviation’s GE9X program manager ) said the GE9x has unofficially beaten the GE-115B record thrust in cold weather triple red line conditions and stated a new record for the books will be forthcoming.


That means at least 121% of rated thrust.. very impressive. But also seems a bit of wasteful overengineering.
 
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Starlionblue
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Re: GE9X Record Breaker

Tue Jun 25, 2019 12:53 pm

PerVG wrote:
mickrussom wrote:
Its very likely. Ted Ingling (GE Aviation’s GE9X program manager ) said the GE9x has unofficially beaten the GE-115B record thrust in cold weather triple red line conditions and stated a new record for the books will be forthcoming.


That means at least 121% of rated thrust.. very impressive. But also seems a bit of wasteful overengineering.


I assume this "overengineering" means you get more margin in normal operation, meaning less wear, meaning lower maintenance costs. So maybe not so wasteful.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
PerVG
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Re: GE9X Record Breaker

Tue Jun 25, 2019 5:06 pm

Being an engineer myself I can say that, in general, overengineering is indeed a wast of money and resources/weight, maybe.
Now, I'm not presuming to know more than GE about their own engine, and I'm sure that there are good reasons for it being as it is. It's just that 20%+ seems like a rather high margin.

On a side note, people tend to be very defensive and see negativity where there is none, in this forum.. Why is that?
 
Max Q
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Re: GE9X Record Breaker

Tue Jun 25, 2019 6:20 pm

Over engineering seems like a good idea when you’re on one engine four hours from land


Better yet it will prevent that from happening
The best contribution to safety is a competent Pilot.


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PerVG
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Re: GE9X Record Breaker

Tue Jun 25, 2019 6:38 pm

Overengineering is not the same as good engineering, although it might seem like it. ;)
 
stephanwintner
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Re: GE9X Record Breaker

Tue Jun 25, 2019 11:30 pm

Cold weather, alone, allows for quite a bit more thrust than, for example, a hot day takeoff. I'm not sure what precise values are used for a rating, but keep in mind that the rated thrust is not what the average engine makes. Every single engine in the fleet, worn or not, should be capable of exceeding that value.

The pilot calculates MTOW and takeoff performance (at runway altitude, and temperature) to ensure proper clearance to all nearby terrain, with some margin, and the aircraft is supposed to not merely meet the curves used for that calculation, but exceed them. Even a worn out engine, which was always a poor performer, is still supposed to exceed those curves.

I can't speak from data, but it would not surprise me if the average, brand new engine, redlined, would beat it's rating by 5%. Maybe more. Add in another 5 or 10 from cold weather, and that's a good part of the way there. If the engine is a test engine, and life is not a concern, then of course some margins can be exceeded as well.
 
Farsight
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Re: GE9X Record Breaker

Sun Jun 30, 2019 1:09 am

Well...i can’t wait to see the new record figures, im going with 131,000lbs
 
chiki
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Re: GE9X Record Breaker

Mon Jul 08, 2019 3:12 pm

Farsight wrote:
Well...i can’t wait to see the new record figures, im going with 131,000lbs
Seen a record of 134k on Twitter Image

Sent from my SM-J415F using Tapatalk
 
estorilm
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Re: GE9X Record Breaker

Mon Jul 08, 2019 7:38 pm

mickrussom wrote:
Farsight wrote:
The GE9X could produce more power than the 115B (its a larger fan diameter GE-115B is 128 inches, the GE9X is 132 in).

Don't forget the numerous increases in fan diameter; the current / final design of the 9X as it sits is 134" not 132".
 
chiki
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Re: GE9X Record Breaker

Fri Jul 12, 2019 7:40 pm

Well confirmed
Image

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Eyad89
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Re: GE9X Record Breaker

Fri Jul 12, 2019 7:59 pm

Question is, why?

77X needs less thrust. Was this increase in thrust planned? Or was it more than expected?
 
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Stitch
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Re: GE9X Record Breaker

Fri Jul 12, 2019 8:24 pm

Eyad89 wrote:
Question is, why?


It is just a by-product of the certification program where it is required to run the engine at maximum fan speed, core speed and exhaust gas temperature so when you do so with this engine, that is the thrust that is generated. It will never come close to those conditions in airline operation so that is why the rated thrust is lower.
 
426Shadow
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Re: GE9X Record Breaker

Fri Jul 12, 2019 11:35 pm

Eyad89 wrote:
Question is, why?

77X needs less thrust. Was this increase in thrust planned? Or was it more than expected?


With 3 years on this site and nearly 600 posts i refuse to believe that you haven't heard of triple redline tests.

Every engine flying today can make much more power than the certified numbers. That doesn't mean its good for the engine, so all engines are de-rated.
Do it on three, One.....THREEEEEEE! Just got the nuts hangin out.
 
Eyad89
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Re: GE9X Record Breaker

Sat Jul 13, 2019 9:27 am

426Shadow wrote:

With 3 years on this site and nearly 600 posts i refuse to believe that you haven't heard of triple redline tests.

Every engine flying today can make much more power than the certified numbers. That doesn't mean its good for the engine, so all engines are de-rated.


Stitch wrote:

It is just a by-product of the certification program where it is required to run the engine at maximum fan speed, core speed and exhaust gas temperature so when you do so with this engine, that is the thrust that is generated. It will never come close to those conditions in airline operation so that is why the rated thrust is lower.


Alright, I guess I wasn't clear in my question.

During the extended block cycle tests, why did the GE9X achieve higher thrust than GE90? I am not asking why it produced more than the GE9x rate thrust, of course.

I am trying to couple this with the fact that the second stage variable inlet stator vane is wearing faster than expected.

Stator vanes wear due to exposure to higher temperature. That's why rise in turbine inlet temperature has always been linked to improvements in material technologies. Higher temperatures means higher thrust. Now, at 134K pounds of thrust, the higher inlet temperature at the second stage could have been higher than what GE engineer expected, and hence the stator vanes failed faster than expected.

Two questions here:

1- Did the stator vane fail because it wasn't designed properly?
2- Or was the design all good but inlet temperature was higher than expected?

With the engine producing more thrust than even GE90, I am guessing it's more of the second point.

Note: it's interesting that the 1st stage stator vanes had no problems even though the inlet temperature would be higher.
 
426Shadow
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Re: GE9X Record Breaker

Sat Jul 13, 2019 5:16 pm

Eyad89 wrote:

Two questions here:

1- Did the stator vane fail because it wasn't designed properly?
2- Or was the design all good but inlet temperature was higher than expected?

With the engine producing more thrust than even GE90, I am guessing it's more of the second point.

Note: it's interesting that the 1st stage stator vanes had no problems even though the inlet temperature would be higher.



Not gonna lie, I doubt anybody here could tell you #1 for certain. And even if they could, why would they?

As far as number 2? Without the data it's anyone's guess.
Do it on three, One.....THREEEEEEE! Just got the nuts hangin out.
 
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kitplane01
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Re: GE9X Record Breaker

Sun Jul 14, 2019 5:44 am

stratclub wrote:
They certainly could easily do it except bragging rights have no place in something as conservative as aviation.


I gotta say you're missing some significant history, which is full of flights for bragging rights. If you want the most recent example,
https://www.cnn.com/travel/article/spee ... index.html
 
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kitplane01
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Re: GE9X Record Breaker

Sun Jul 14, 2019 5:47 am

mickrussom wrote:
Farsight wrote:
Then how was the 127,000lbs figure achieved during GE90 testing?

Triple red line testing of the engine in a test bed with a potentially sacrificial SETT (second engine to test - after certification this will be the reference design).

GE Aviation ran the GE90-115B ran for approximately 60 hours at triple-red-line conditions (maximum fan speed, core speed and exhaust gas temperature) to evaluate the engine at its operational limits and demonstrate its capability beyond the most extreme operating conditions.


I've always wondered .. how does one achieve triple-red-line conditions? Is there some guarantee that max fan speed and max core speed always produces exactly max EGT? That doesn't sound likely. Or that max core speed at max EGT always produces max fan speed?
 
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kitplane01
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Re: GE9X Record Breaker

Sun Jul 14, 2019 5:51 am

stephanwintner wrote:
Cold weather, alone, allows for quite a bit more thrust than, for example, a hot day takeoff. I'm not sure what precise values are used for a rating, but keep in mind that the rated thrust is not what the average engine makes. Every single engine in the fleet, worn or not, should be capable of exceeding that value.


That's not true for the part 91 fleet (Cessna Piper Mooney). Is it really true for the airliner fleet?
 
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kitplane01
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Re: GE9X Record Breaker

Sun Jul 14, 2019 5:54 am

If the engine can clearly produce more than rated thrust .... why is that not allowed during emergencies?

Example: If some particular flight is weight limited because of engine-out concerns, and the engine had an extra bit of thrust just for emergencies, then one could increase weight. (Assuming enough rudder, strong enough pylon, etc.)

I would assume there are some emergencies where an extra 10% of thrust for 5 minutes would make things better/easier. And it's availability would help with some operational restriction.
 
waly777
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Re: GE9X Record Breaker

Sun Jul 14, 2019 5:59 am

kitplane01 wrote:
If the engine can clearly produce more than rated thrust .... why is that not allowed during emergencies?

Example: If some particular flight is weight limited because of engine-out concerns, and the engine had an extra bit of thrust just for emergencies, then one could increase weight. (Assuming enough rudder, strong enough pylon, etc.)

I would assume there are some emergencies where an extra 10% of thrust for 5 minutes would make things better/easier. And it's availability would help with some operational restriction.


The 77W has this option with the thrust bump. However this means faster engine wear & tear.
The test of first-rate intelligence is the ability to hold 2 opposed ideas in the mind concurrently, and still function
 
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Starlionblue
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Re: GE9X Record Breaker

Sun Jul 14, 2019 6:46 am

kitplane01 wrote:
If the engine can clearly produce more than rated thrust .... why is that not allowed during emergencies?

Example: If some particular flight is weight limited because of engine-out concerns, and the engine had an extra bit of thrust just for emergencies, then one could increase weight. (Assuming enough rudder, strong enough pylon, etc.)

I would assume there are some emergencies where an extra 10% of thrust for 5 minutes would make things better/easier. And it's availability would help with some operational restriction.


There are a couple reasons:
- If you're down to a single engine, you don't want to dramatically increase the risk of failure by running on the bleeding edge of performance.
- The take-off and go-around calculations assume an engine failure at the worst possible time, with the thrust level on that day (including any flex/derate). In other words you don't need more.
- Wear and tear increases significantly at the top end of the thrust range. Which is why almost all take-offs use some sort of reduced thrust.

That being said, on A330 and A350 the TOGA limits are different with an engine out. 10 minutes at TOGA, as opposed to 5 minutes with both engines. Are the engines different with an engine out? Of course not. However, in normal operation, you're extremely unlikely to need TOGA for more than a few minutes, so I'm guessing RR simply limits wear and tear by imposing a 5-minute limit. On the other hand, with an engine out, wear and tear take a back seat to safety.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
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kitplane01
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Re: GE9X Record Breaker

Sun Jul 14, 2019 6:58 am

waly777 wrote:
kitplane01 wrote:
If the engine can clearly produce more than rated thrust .... why is that not allowed during emergencies?

Example: If some particular flight is weight limited because of engine-out concerns, and the engine had an extra bit of thrust just for emergencies, then one could increase weight. (Assuming enough rudder, strong enough pylon, etc.)

I would assume there are some emergencies where an extra 10% of thrust for 5 minutes would make things better/easier. And it's availability would help with some operational restriction.


The 77W has this option with the thrust bump. However this means faster engine wear & tear.


My question was about an extra bit of thrust only used in emergencies. Never used in normal operations. There should be no extra wear and tear (unless you have an emergency).

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