Forum: Civil and General Aviation

I've got a few questions about the aircraft engines. I get some information from my mother who works for GE, but I want some info from more people who work in the field.

First, of the major manufacturers, GE, PW, and RR, what are teh major characteristics of each. The GE seem teh most powerful for the most part. The PW are usually lighter than the others. The RR engines seem to well... suck. They are heavier, burn more fuel, and have less thrust than the others.

For military engines, I know nothing about who makes what good.

Who has the best SFC's?

Why haven't they replaced the 8 old engines on the BUFF with 4 newer, better engines if they are making more anyway?

How does jet fuel ignite when the engine starts? Is there some sort of spark plug like in a car or is it the fact that the compressor raises the temperature enough for the fuel to autoignite?

What exactly is spool and how do you have multiple of them in a single engine?

F-16.net Sponsor

Jet engines 101.

http://www.grc.nasa.gov/WWW/K-12/airplane/shortp.html Go to Turbine engines. This is a massive resource for everything that flies. Lots of theory to.

Or you could just go to GE`s own site . It has some very good engine animations in Java. Even though it`s just a sales pitch for it`s own products....

Officially, the worlds leading engine manufacturers are , in this order...

1.GE
2.RR
3.P/W.

The GE 90 is the most powerful jet in the world, developing 127,900 lbs of thrust in tests. Recognized by Guiness. In use, airlines will never use this amount of thrust. Engine thrust is nowadays controlled by digital FADEC. Full Authority Digital Engine Control. A kind of ECU for aircraft.

RR uses triple spool designs while GE uses twin spool. This makes the RR engines generally shorter and lighter.

To get similar thrust, the RR engine will spin more slowly than a twin spool design, increasing reliability, reducing maintenance costs.
(Spool is defined as a group of compressor stages rotating at the same speed)
All will become clear when you get an umderstanding of basic jet design.

Ok, here's something else I thought of. Why do variable inlets exist? It's a very newb thing to ask, but I haven't gotten to that information yet in any of my classes. How does the air flow work that the variable inlet geometry is superior? Also, why is this not possible in stealth aircraft? Couldn't something be designed to all this to work without the increased radar signature?

Synpa, excellent presentation. Couldn't have done it better. Lord of Bunnies, Rolls Royce engines "suck"??? There are no such engines as Rolls Royce. Incorporation of iceless, heatless inlet cones, a ratchet locking spline shaft system that prevents turbine disintegration, what are you talking about? 23% more thrust than engines in the same category and every class?

VIGV's exist to allow relative wind to impact the fan and sometimes subsequent stages of the compressor to be extremely efficient, more so than fixed stators. They are in series with the alpha unit system, pitot/static system and FCC's to prevent compressor stalls and allow overall better acceleration/decelleration, supreme reaction with throttle motion, optimal fuel flow/conservation, and downright better performance.

GE builds the best engines, PERIOD! Rolls builds darned dependable engines that give me 1.14 times as much thrust as the American competitor. In certain military jets I’ll take the RR any day of the week! And when I can’t go RR, I’ll go GE vs. Pratt & Shitney. I know that comment will “Papa Off” Miss Angela but the truth is the truth. Laughing

And remember, all jet engines suck and blow... Rolling Eyes

Hey, sorry. I'm just reporting what I saw in civil aircraft. I was looking through Jane's for some info gathering for one of my lab mates and I began looking at the effects of the different engines. From what I saw, the RR engines have a higher TO distance, shorter range, and weight more. This isn't for some specific plane I noticed it for most aircraft I was looking at, Airbus and Boeing. I don't know about for military engines, but for civil they certainly appear to not have the power advantage. Correct me if I'm wrong, but I believe the CF6-80C2 is the world's most reliable engine. Sorry if I'm a little biased against Rolls, my mother works with GE and she's working on the F414. The Rolls (Allison, I think they are an American partner or something like that) parts in the engine keep failing in tests and they don't want to change it.

Anyway, anybody know about respective SFCs?

How about widemouth GE vs smallmouth GE?

trailmix wrote:

How about widemouth GE vs smallmouth GE?

The engine is the same; it is the inlet size (and only on the F-16) that widemouth/smallmouth refers to.

Lordofbunnies, I thought GE Allison and RR were working on the F-120 engine???? A lot of the parts are derivatives from the F-414 though.....
If your mom works for GE, that explains her bias!!!!!!!!!!!!!!!!!!!!!!!!!!

I personally think RR, being a MUCH smaller company than either GE or P/W has done remarkably well even trying to compete. That impresses me the most.
Engine parts failures in new engines do happen with exhaustive testing. I am sure problems will be ironed out! Testing always pushes engines beyond what they are designed to do, to set safety and technical standards.

JR, didn`t realise P/W had such a bad rep`? Shocked

I think GE and Allison are different companies. In fact, I believe Allison is part of RR in the states. The US Navy got sued by the state of California (friggin' hippies Rolling Eyes

) for putting out to many emissions. Thus, the planes needed to be revamped or some such. They are working on updating the F414 so it meets California emission standards or some such. They may have also wanted an upgrade for the SH so it performs better. I don't know much about it, but in 5 consecutive test after giving them months, Allison has still not made a part that won't crack. So far the results are significantly reduces NOx and unburned hydrocarbons.

I'm trying to ignore my bias against the other companies (even though GE is paying for college... sort of Wink

) to look at it analytically. How are maintenance on the different engines and how are the respective SFCs?

...friggin' hippies Wink

Your bias against RR is justified...RR is a major player in the commercial aircraft sector with its Trent series.However,in the supersonic fighter aircraft sector RR has nothing to offer and dwindled into insignificance compared to P&W and GE ..Believe it or not RR has singlehandedly developed only three engines since 1945 ..Bac lightning,Harrier,and the jet trainer Hawk and that's all...Amazing isn't it...All others were either licence production such as Phantom or joint ventures with others Tornado,Eurofighter,Jaguar and so forth..If you take a look at the immense range of engines developed by Pratt&Whitney alone since 1950..The difference between them is obvious..Today RR is learning from Pratt how to build state of the art jet engines ( Joint Strike Fighter)..Since the second world war,both GE and Pratt have revolutionized the jet engine technology with new innovations such as High by-pass turbofan ratio technology for commercial aircraft..I can't recall any from RR..

Come on guys, know your history!
Since 1945, RR has developed at least 8 series of major engines, just off the top of my head. Today, GE ask RR to be partners in specific projects, like the JSF. The worlds biggest engine maker GE are not fools.

Innovation and other FACTS ????? Ok... lets see....
The RR Eagle engine was the first engine to power an aircraft across the Atlantic ocean.

RR engined aircraft set world speed records on several occasions with it`s "R" engine. This engine also held , land and water speed records.Later thr "R", Avon and Spey held land speed records. RR helicopter engines hold world speed records.

America`s legendary P-51 Mustang was powered by RR Merlin engines.

In 1946, the RR Nene engine powered the US navy`s Grumman Panther. Pratt and Whitney built the Nene under licence.

The Conway engine introduced the bypass principle.

The RR Spey engine powered the A-7, flown by the USN and USAF. The Spey was built under licence in the US.

The turbofan engine, originally called the bypass turbojet by its inventors.....RR. The first turbofan, the RR Conway.

The worlds first Turboprop engine...by...RR!

RR powers 17 different airliners, GE 14, P/W 10.

RR has 50,000 engines in service with 500 airlines. 2,500 corporate users and over 100 millitaries. RR`s product range is far more diverse than GE or P/W.

In 1997, a Boeing triple 7 recorded the worlds longest commercial flight of nearly 11,000 miles at 553mph....Powered by RR Trents.,

Guys, the list goes on... GE and P/W have produced many firsts as well. I particularly like GE engines. Don`t knock RR, they nearly went bust in 1971, came back and are near the top of their game.

Lordofbunnies, how is the University Technology Centre going, the one set up by Purdue university and RR??????????? That`s your university isn`t it? Very Happy

By the way, the Phantom flown by the RAF was powered by the RR Spey engine. ALL engine manufacturers collaborate to some degree on engines now, they are so damn expensive to build from scratch!!!!
Yes, Allison are owned by RR....No, I don`t work for RR!!!!!!!!
Lastly, the US Navy has chosen Bae and RR to provide a major component for its all electric drive new class warships...... RR cant be that bad can they??? Very Happy

snypa777,

Very well said. You folks look at what the Harrier engine does and how it performs and tell me RR doesn't do some fabulous work, and that's just on example. Start reading and learn what is, and has, happened.

I will gladly and confidently fly my GE, RR, or Allison engine any day of the week. And in that order...

''America`s legendary P-51 Mustang was powered by RR Merlin engines.''

No, initially it was powered by a 1250 horspower, liquid-cooled Allison V-1710 engine...The RAF wanted a more powerful engine for their Mustang's and started fitting them with Merlin's..But here came the rub ..Merlin engines were susceptible to carburetor stall which cost many RAF pilots lives during the Battle of Britain 1940 ..(The major weakness of Spitfire compared to Messerschmitt 190's fuel injection turbo)Also USAF pilots who fitted their Mustang's to increase the power and the high altitude capacity complained about the technical deficiencies of the MERLIN..

''The turbofan engine, originally called the bypass turbojet by its inventors.....RR. The first turbofan, the RR Conway.''

Wikipedia is not the best source of information...

The first high-bypass turbofan engine was the GE TF9 built to power the C5 GALAXY military transport aircraft.

Most of the very-large engines in this class were pioneered in the US by PW and GE which for the first time as outcompeting England in engine design. Rolls-Royce also started the development of the "high-bypass turbofan", and although it caused a considerable trouble at the time, the RB 211 would go on to become one of their most successful products.

''RR`s product range is far more diverse than GE or P/W.''

Really ??,you obviously didn't take time to look at what they have developed since 1950,'s.Talking about product range diversity,you don't include PW's Space Propulsion Division and it's products..do you?

''In 1997, a Boeing triple 7 recorded the worlds longest commercial flight of nearly 11,000 miles at 553mph....Powered by RR Trents''.,

Yes ,on the other hand British Airways has chosen the GE instead of RR to power it's own 777's.The biggest shock ever for RR even bigger than 1971.
62% of all A-380 customers selected Engine Alliance due to innovation and superiour engineering...

''Lastly, the US Navy has chosen BAe and RR to provide a major component for its all electric drive new class warships...... RR cant be that bad can they??? ''

This was a political decision ..The US is selling 10 times more weapons and technology to the UK than it buys from there.. BAe today is desperately trying to merge (taken over) with Boeing or Lockeed to gain access to future high technology projects under development in the US..

No,of course RR can't be that bad.. Alone the idea of using gas turbines as ship propulsion was really great and genius..

Everyone with specific stats on RR and opinions - RIGHT ON!!

Forum: Civil and General Aviation

Aircraft Engines - Civil and Military