And Those Other Guys ... the Su-35, T-50, J-20, and Others

[steel_selachian]

Figured I'd start this thread to discuss some of the newer Russian/Chinese aircraft popping up these days - the developmentally-delayed Sukhoi Su-35 and the in-testing T-50, as well as Chengdu's just-revealed J-20 - as a companion to discussion of the F-35. While some factors like performance and capabilities are murky, we might be able to discuss how much these designs might proliferate - for instance, Sukhoi's been marketing the Su-35 for a while and a few analysts seem to expect every third-world air force to pick some up, but at present they only have 48 orders from the Russian Air Force (I've seen some references to an order for 24 from Venezuela, but I have trouble figuring whether that's shinola or something else starting with s...). Another topic might be how quickly these things can get into service - Russia has stated the T-50 will get into service in 2015 and China expects J-20s in service before the close of the decade, but again that might be a load.

Commence!

[old_pop2000]

Hi Steel:
Another good topic for a thread. Before we begin to do a 1v1 analysis of fighters, let me bring in some, not so interesting thoughts. 1v1 performance analysis is interesting and valuable, but it can be very misleading. An example is at the start of Rolling Thunder in 1965, if you had done a 1v1 analysis of an F4B Navy fighter or the USAF version, the F4C, versus the Mig-17, the F4B would have been expected to win the engagement, under most conditions. It was a mach 2 aircraft, with a long range search, acquisition and tracking radar, with heat seeking and radar guided missiles and two crewmen with good rearward visibility for the era. The Mig was subsonic, no missiles, short ranged and no radar. It could out maneuver the F4 but not out dive it, or out climb it.

Well, that wasn't what happened. First, the F4 radar systems could not tell friend from foe. If it saw an incoming bogie, without visual identification, it could not interrogate the opponent. So, we got ROEs calling for visual identification. That eliminated almost immediately the advantages of radar and the AIM-7 BVR capability and put the heavier F4 into the Migs best flight envelope. Next problem was the fact that the F4B radar lost lock, when it looked down because no moving target indicator system was incorporated. If the Mig dived to the deck, the radar lost lock. Next, the AIM-7, was totally unreliable due to the fact that we had never really test flown it in dogfights to see how the tubes would withstand the G forces and hold up in moisture laden environment of South Vietnam. Now, pilots had to ripple fire two missiles to get one to fire and track. We also found out that the missiles had a narrow engagement envelope which, if the Mig turned quickly enough, it could easily outmaneuver the missiles. The story gets worse with smoky engines, and no guns. Another issue that 1v1 doesn't explain is maintenance. It isn't how many aircraft you can put up on the first mission. It's how many you can put up on the last mission. The Russian's are notorious for suddenly failing to supply sufficient spares during the times of need for third world countries. Combat tend to eat up spares rapidly and your force of sophisticated Su-35s or T-50s will be just so much junk sitting on the runways due to lack of parts. 1v1 comparisons rarely take this kind of stuff into account. The Russians always build simple, robust weapons that work in all environments which is good for assault rifles, tanks, and trucks maybe, but not for Mach 2 aircraft. They are sophisticated, delicate machines that can break after a hard landing and need regular maintenance to be completely effective.

However, 1v1 analysis is fun but many unknown factors can negate any performance advantage. The key is to remember that air warfare is not always 1v1, but 2v1, 2v2 etc. The guy with aircraft who can do back flips is not necessarily the guy who will win the battle. Battle force management and air doctrine will, over time be the deciding factors for air supremacy, not a 1v1 encounter. BTW, in the Gulf War, there were some close friendly fire incidents with coalition aircraft. The coalition had not had time to consider IFF problems in combat, so even US F-15s had some tension filled moments. So, 20 years after the end of the Vietnam war, the problem of identifying your opponent at BVR was still with us.

Now, what about this new chinese stealth fighter and the PAK-FA?

P.S. Steel, this is your thread, but could we include ACM in our discussion? Your decision, I don't want to derail your excellent thread topic.

[steel_selachian]

ACM could be a point of discussion, but I'd like to steer it more towards how many of these birds are likely to be produced and how many export customers Russia and the PRC can expect to find for them - as stated, one of my impetuses for starting this thread was that I was trying to figure out if Venezuela has a firm order for Su-35s or if that's another purported buy that's fallen through since Venezuela's economy started going downhill. 1v1 comparisons do make for interesting discussion, but my general rule is that armchair theory usually doesn't match what happens in combat (there's your example with the F-4B/C and the MiG-17, plus I'm sure the two North Vietnamese MiG-17 drivers who managed to get knocked down by A-1 Skyraiders in 1965 and 1966 were pretty damn surprised when it happened).

That said, there has been some interesting speculation about the T-50 and J-20 as far as ACM goes. We don't have weights for either bird as far as I'm aware, and both are likely going to need design changes before entering production, but they are big aircraft - 66 ft. in length for the T-50 and an estimated 70 for the J-20. I'd expect both to be heavier jets than the F-22. Also, even under the most optimistic estimates they won't be fielded until the end of this decade, and that seems like a really abbreviated period to work the bugs out of a complex aircraft (it took the F-22 that long to go from prototype to preproduction, with another 5 years for IOC). Which means that in a hypothetical dogfight circa 2020 they might be immature designs facing US F-22s and pilots that have a decade and a half of operational flights and exercises under their belts.

[old_pop2000]

ACM could be a point of discussion, but I'd like to steer it more towards how many of these birds are likely to be produced and how many export customers Russia and the PRC can expect to find for them - as stated, one of my impetuses for starting this thread was that I was trying to figure out if Venezuela has a firm order for Su-35s or if that's another purported buy that's fallen through since Venezuela's economy started going downhill. 1v1 comparisons do make for interesting discussion, but my general rule is that armchair theory usually doesn't match what happens in combat (there's your example with the F-4B/C and the MiG-17, plus I'm sure the two North Vietnamese MiG-17 drivers who managed to get knocked down by A-1 Skyraiders in 1965 and 1966 were pretty damn surprised when it happened).

That said, there has been some interesting speculation about the T-50 and J-20 as far as ACM goes. We don't have weights for either bird as far as I'm aware, and both are likely going to need design changes before entering production, but they are big aircraft - 66 ft. in length for the T-50 and an estimated 70 for the J-20. I'd expect both to be heavier jets than the F-22. Also, even under the most optimistic estimates they won't be fielded until the end of this decade, and that seems like a really abbreviated period to work the bugs out of a complex aircraft (it took the F-22 that long to go from prototype to preproduction, with another 5 years for IOC). Which means that in a hypothetical dogfight circa 2020 they might be immature designs facing US F-22s and pilots that have a decade and a half of operational flights and exercises under their belts.

No problem, I will stay within your area of discussion. As to weight, if we assume a one to one thrust to weight ratio based on the engine thrust, the T-50 will probably top out at 33 tons. Looking at her design, the J-20 is probably a 20-30 ton aircraft.

As far as when they will be fielded, the Russians tend to be low risk takers in the field of military technology. They might develop a new aerodynamic shape, but use upgraded engines from previous designs and same goes for electronics, hydraulics and pneumatics. This eliminates reinventing the wheel and shortens development and production cycles. We, in the west, tend to start with a clean sheet of paper, using new engines, electronics and aerodynamic design. This lengthens the development period. Development for the Russian aircraft will proceed faster, with sizeable orders from third world nations. The problem is the reliability of russian supply pipelines and training. Many nations want production in their own country, and that hurts the Russians over time. One other problem is the large, single piece ground support equipement that has to be moved in one big piece. That can hinder movement of aircraft to advanced fighter bases. The west tends to build modular units that are far smaller and lighter, making them easier to move and reposition. Remember the 1v1 analysis problems? This is one it does not take into consideration. If you can't move the GSE, you don't move the plane or perform maintenance. Testing on the ground, without using the engines requires both portable power and an ice cream machine for cooling of the electronics. Without them, nothing happens. If you have to use the engines, this puts extra wear and tear on them and uses lots of fuel. They are also noisy as hell on the ground, trust me.

[steel_selachian]

No problem, I will stay within your area of discussion. As to weight, if we assume a one to one thrust to weight ratio based on the engine thrust, the T-50 will probably top out at 33 tons. Looking at her design, the J-20 is probably a 20-30 ton aircraft.

As far as when they will be fielded, the Russians tend to be low risk takers in the field of military technology. They might develop a new aerodynamic shape, but use upgraded engines from previous designs and same goes for electronics, hydraulics and pneumatics. This eliminates reinventing the wheel and shortens development and production cycles. We, in the west, tend to start with a clean sheet of paper, using new engines, electronics and aerodynamic design. This lengthens the development period. Development for the Russian aircraft will proceed faster, with sizeable orders from third world nations. The problem is the reliability of russian supply pipelines and training. Many nations want production in their own country, and that hurts the Russians over time. One other problem is the large, single piece ground support equipement that has to be moved in one big piece. That can hinder movement of aircraft to advanced fighter bases. The west tends to build modular units that are far smaller and lighter, making them easier to move and reposition. Remember the 1v1 analysis problems? This is one it does not take into consideration. If you can't move the GSE, you don't move the plane or perform maintenance. Testing on the ground, without using the engines requires both portable power and an ice cream machine for cooling of the electronics. With them, nothing happens. If you have to use the engines, this puts extra wear and tear on them and uses lots of fuel. They are also noisy as hell on the ground, trust me.

True, and the simpler design process can also hurt things. Re-using off-the-shelf stuff can speed up the testing and deployment of an aircraft, but it may also mean something that doesn't work as well. Remember that a key part of the F-22s' and F-35s' capabilities revolve around the LPI AESA radars designed for those aircraft. Having a stealth fighter that announces its presence to everyone within a few hundred miles when it lights off the radar isn't much use. Now the Russians do have their Irbis-E system included on some Su-30s and the Su-35, but I'm not really convinced that will do the trick. Likewise, you have other issues like stealth coatings and the fact that the engine exhausts will have to be completely redone to reduce the all-aspect RCS and IR signature. Also, until the Chinese finally get their indigenously produced WS-10 engine working to spec they'll be dependent on the Russians for fighter engines. Doesn't sound like fun.

As far as Third World orders, one has to consider these aren't bargain 60s-vintage MiGs - the estimates I've seen for the Su-35's pricetag range from $45 million to $65 million per copy. It's going to be hard for a lot of tinpot militaries to scrape together the cash to buy a squadron - as is some Su-27/30 customers have only been able to afford single-digit buys. Presumably the T-50 and J-20 will be somewhat more expensive, which means I really don't see them going that far. India will almost certainly buy a goodly number of T-50s (they underwrote much of the project), and if Pakistan hasn't completely gone to pot by then a buy of J-20s might come up as a counter. Vietnam has been postulated as a T-50 customer, which I can see as plausible if China has J-20s. Some Middle Eastern countries might be interested; the Saudis have bought Russian gear before and we're unlikely to give them F-35s anytime soon. Between sanctions and financial problems Iran is trying to establish a homegrown arms and aircraft industry. As far as South America, Brazil may be interested, but I can't really see any of their neighbors ponying up the money - Venezuela has gotten considerably less ambitious about arms purchases lately, which is one reason I think the mentions of them plunking down for 24 Su-35s and more Su-30s are probably bunk. Most Western and Western-leaning militaries will probably be interested in F-35s by the 2020s, when economy of scale will have probably dropped the price somewhat.

[old_pop2000]

True, and the simpler design process can also hurt things. Re-using off-the-shelf stuff can speed up the testing and deployment of an aircraft, but it may also mean something that doesn't work as well. Remember that a key part of the F-22s' and F-35s' capabilities revolve around the LPI AESA radars designed for those aircraft. Having a stealth fighter that announces its presence to everyone within a few hundred miles when it lights off the radar isn't much use. Now the Russians do have their Irbis-E system included on some Su-30s and the Su-35, but I'm not really convinced that will do the trick. Likewise, you have other issues like stealth coatings and the fact that the engine exhausts will have to be completely redone to reduce the all-aspect RCS and IR signature. Also, until the Chinese finally get their indigenously produced WS-10 engine working to spec they'll be dependent on the Russians for fighter engines. Doesn't sound like fun.

As far as Third World orders, one has to consider these aren't bargain 60s-vintage MiGs - the estimates I've seen for the Su-35's pricetag range from $45 million to $65 million per copy. It's going to be hard for a lot of tinpot militaries to scrape together the cash to buy a squadron - as is some Su-27/30 customers have only been able to afford single-digit buys. Presumably the T-50 and J-20 will be somewhat more expensive, which means I really don't see them going that far. India will almost certainly buy a goodly number of T-50s (they underwrote much of the project), and if Pakistan hasn't completely gone to pot by then a buy of J-20s might come up as a counter. Vietnam has been postulated as a T-50 customer, which I can see as plausible if China has J-20s. Some Middle Eastern countries might be interested; the Saudis have bought Russian gear before and we're unlikely to give them F-35s anytime soon. Between sanctions and financial problems Iran is trying to establish a homegrown arms and aircraft industry. As far as South America, Brazil may be interested, but I can't really see any of their neighbors ponying up the money - Venezuela has gotten considerably less ambitious about arms purchases lately, which is one reason I think the mentions of them plunking down for 24 Su-35s and more Su-30s are probably bunk. Most Western and Western-leaning militaries will probably be interested in F-35s by the 2020s, when economy of scale will have probably dropped the price somewhat.

The Su-35s avionics suite is to be the basis for the T-50 aircraft and that more than enough capability as it is right now. One area of problems is cooling for the aircraft. Any hot spot on the plane will be detectable by IR detectors and sights. The cooling system itself can be a source of the heat and you have insulate and keep it cool. I don't see any real issues with the Russian avionics suite having the necessary capability. On paper, ours might look better, but again, combat will tell the story.

I can't really see any third world orders coming from the South American countries. Venezuela has been put on the US no sell list but the rest aren't. As for the Saudi's, they have two or three Iraqi wars to use as examples of russian equipment. They have plenty of money to buy good US made equipment and we are already in country to help with training. It's a no-brainer.

[JMS]

I disagree, the US has been reluctant to sell up to date technology to countries South of El Paso, which forced most to turn to other sources, that's why Mirages sold so well (Chile, Argentina, Brazil, Peru, Ecuador, Colombia and Venezuela had them). Only in the 90s more up to date gear was sold (only first hand sale, though was F-16 to Chile). Even now, they are wary of US gear. Chile has bought a lot of F-16s from the Netherlands to replace their older planes, but Peru bought MiG-29s under Fujimori (and was less than thrilled), Brazil went for French Mirages, and everyone's favorite bought Su-30s. Colombia bought Kfirs.

[old_pop2000]

I disagree, the US has been reluctant to sell up to date technology to countries South of El Paso, which forced most to turn to other sources, that's why Mirages sold so well (Chile, Argentina, Brazil, Peru, Ecuador, Colombia and Venezuela had them). Only in the 90s more up to date gear was sold (only first hand sale, though was F-16 to Chile). Even now, they are wary of US gear. Chile has bought a lot of F-16s from the Netherlands to replace their older planes, but Peru bought MiG-29s under Fujimori (and was less than thrilled), Brazil went for French Mirages, and everyone's favorite bought Su-30s. Colombia bought Kfirs.

The US government has always been reluctant to sell sophisticated weapons to the South American countries due to their volatile political and social nature. They don't want the aircraft and technology falling into the wrong hands. I agree with that idea. These countries use those weapons more against their own country than others. They really are not threatened by anyone out of the South American continent. It's probably safer, in my estimation. Most of the purchases are probably used aircraft. Equador is seeking former South African Mirage III jets. How really effective these aircraft are going to be is problematic.

[steel_selachian]

The US government has always been reluctant to sell sophisticated weapons to the South American countries due to their volatile political and social nature. They don't want the aircraft and technology falling into the wrong hands. I agree with that idea. These countries use those weapons more against their own country than others. They really are not threatened by anyone out of the South American continent. It's probably safer, in my estimation. Most of the purchases are probably used aircraft. Equador is seeking former South African Mirage III jets. How really effective these aircraft are going to be is problematic.

Well, it depends on what the nation in question's priorities are - most are concerned with maintaining basic air sovereignty and dropping bombs on insurgent groups in the jungle. At the worst, a real war with a neighboring country, most would be fighting an equally obsolete air force. Very few countries in the world face the real, no-kidding possibility of going up against a true modern air force or extensive IADS. So there aren't may countries south of the Rio Grande that would really consider buying something as sophisticated as a T-50 or J-20. Brazil (with a decent economy, a large regionally-powerful military, and offshore territorial claims over oil fields) and Venezuela (bat-doody nuts) are two exceptions, but even they will probably look no farther than 4th-gen aircraft. A Gripen, Rafale, F/A-18E, or Su-30 is more than enough technological terror for those nations.

[old_pop2000]

Well, it depends on what the nation in question's priorities are - most are concerned with maintaining basic air sovereignty and dropping bombs on insurgent groups in the jungle. At the worst, a real war with a neighboring country, most would be fighting an equally obsolete air force. Very few countries in the world face the real, no-kidding possibility of going up against a true modern air force or extensive IADS. So there aren't may countries south of the Rio Grande that would really consider buying something as sophisticated as a T-50 or J-20. Brazil (with a decent economy, a large regionally-powerful military, and offshore territorial claims over oil fields) and Venezuela (bat-doody nuts) are two exceptions, but even they will probably look no farther than 4th-gen aircraft. A Gripen, Rafale, F/A-18E, or Su-30 is more than enough technological terror for those nations.

Most nations in that region are in the self defense mode. If you examine their aircraft and capability, it is sad. Look at the most recent Alto-Cenepa border war between Peru and Equador. The Peruvians were sadly lacking in experience and good aircraft. So, afterward, they went to Belarus and Russia, to buy a conglomeration of 15 Mig-29s, three of which have already crashed. Both sides had to have foreign loans to outfit their ground and air defenses. Equador probably did the best in the air, managing to maintain air supremacy over the battlefield and keeping their Jaguars in reserve. It was a typical border war, and this has happened in this region many times. None can finance expensive aircraft, nor do they really need them. Gripens, Rafales, F-18s or SU-30s are beyond their capability or financing. Kfirs, Mirage III, 5 and Jaguars are about the best they can really handle. This small border war is typical of the small wars in the region. BTW, the number of operational aircraft at any one time is very low. Many airframes were just that, airframes.

[steel_selachian]

Weenie roast, anyone?

http://www.flightglobal.com/articles/2011/08/24/361215/npo-saturn-reveals-cause-of-pak-fa-engine-flame-out.html (http://www.flightglobal.com/articles/2011/08/24/361215/npo-saturn-reveals-cause-of-pak-fa-engine-flame-out.html)

[old_pop2000]

Weenie roast, anyone?

http://www.flightglobal.com/articles/2011/08/24/361215/npo-saturn-reveals-cause-of-pak-fa-engine-flame-out.html (http://www.flightglobal.com/articles/2011/08/24/361215/npo-saturn-reveals-cause-of-pak-fa-engine-flame-out.html)

Looks like my lighter when I smoke my pipe. "Lights the first time, everytime".

[steel_selachian]

Looks like my lighter when I smoke my pipe. "Lights the first time, everytime".

Makes me wonder how realistic the Russian assertion is that they'll have production fighters in service by 2015.

As a related note, the Pentagon apparently believes the PRC's J-20 will be operational by 2018.

[old_pop2000]

Makes me wonder how realistic the Russian assertion is that they'll have production fighters in service by 2015.

As a related note, the Pentagon apparently believes the PRC's J-20 will be operational by 2018.

I wouldn't be all that worried about the J-20, it will cost about two to three times more than the latest they are now producing and examining Chinese quality control means that they will have production and maintenance issues with the bird. I doubt they can keep many flying. All show and not much go. Probably the birds that are able to be maintained will be good AtoA platforms, but not much else.

[steel_selachian]

I wouldn't be all that worried about the J-20, it will cost about two to three times more than the latest they are now producing and examining Chinese quality control means that they will have production and maintenance issues with the bird. I doubt they can keep many flying. All show and not much go. Probably the birds that are able to be maintained will be good AtoA platforms, but not much else.

The real issue with the J-20 appears to be the progress on the WS-15 engine for the production variant. There's no guarantee that the PRC won't start producing reliable jet engines, but at present they're still dependent on Russian-built powerplants. Their current WS-10 series engines have a lifetime of about 30 hours versus 400 for the Saturn AL-31F.

http://www.washingtonpost.com/wp-dyn/content/article/2010/12/24/AR2010122403009.html

There's also the question of defining "operational" here; whether that will mean the planes and trained crews are available in sufficient numbers to make a serious impact. The Pentagon review also appears to be under the impression that the J-20 is more likely a long-range LO fighter-bomber/maritime strike platform than an air-superiority design.

http://www.defense.gov/pubs/pdfs/2011_CMPR_Final.pdf

[old_pop2000]

The real issue with the J-20 appears to be the progress on the WS-15 engine for the production variant. There's no guarantee that the PRC won't start producing reliable jet engines, but at present they're still dependent on Russian-built powerplants. Their current WS-10 series engines have a lifetime of about 30 hours versus 400 for the Saturn AL-31F.

http://www.washingtonpost.com/wp-dyn/content/article/2010/12/24/AR2010122403009.html

There's also the question of defining "operational" here; whether that will mean the planes and trained crews are available in sufficient numbers to make a serious impact. The Pentagon review also appears to be under the impression that the J-20 is more likely a long-range LO fighter-bomber/maritime strike platform than an air-superiority design.

http://www.defense.gov/pubs/pdfs/2011_CMPR_Final.pdf

Hi Steel:
In examining the J-20's specs, this is one very big aircraft probably weighing in excess of 75,000 lbs. It is more in the class of the FB-111. This means probably a very hefty fuel supply for long range. Again, we are working with brochure knowledge. The engines on such a heavy aircraft will be absolutely vital and had better be very reliable, because they won't fly well, if at all on one engine.

As to the Pentagon, they have a propensity to use one or more foreign weapons as a way of opening up the coffers of the Congress, I've seen it more times than I can think of. I remember the issue with the MIG-25 and how they now needed a bird to deal with it. As usual, Congress bit and only later did we learn it was a flash in the pan, and not a real threat except to airliners.

[Ed Rotondaro]

The real issue with the J-20 appears to be the progress on the WS-15 engine for the production variant. There's no guarantee that the PRC won't start producing reliable jet engines, but at present they're still dependent on Russian-built powerplants. Their current WS-10 series engines have a lifetime of about 30 hours versus 400 for the Saturn AL-31F.

http://www.washingtonpost.com/wp-dyn/content/article/2010/12/24/AR2010122403009.html

There's also the question of defining "operational" here; whether that will mean the planes and trained crews are available in sufficient numbers to make a serious impact. The Pentagon review also appears to be under the impression that the J-20 is more likely a long-range LO fighter-bomber/maritime strike platform than an air-superiority design.

http://www.defense.gov/pubs/pdfs/2011_CMPR_Final.pdf

Steel:

When you say that the WS-10 engines have a lifetime of 30 hours, I assume you mean that the engines then need to be overhauled and rebuilt? Or is the engine totally trashed after 30 hours use? If so the operational life of an aircraft with this engine is to short to effective.

[old_pop2000]

Steel:

When you say that the WS-10 engines have a lifetime of 30 hours, I assume you mean that the engines then need to be overhauled and rebuilt? Or is the engine totally trashed after 30 hours use? If so the operational life of an aircraft with this engine is to short to effective.

Hi Ed:
The lifetime figure means that the engine has to be removed and overhauled after 30 hrs. That is extremely low for any aircraft. The TF-30's in the F-14 had a life of 700 hrs before removal for maintenance, the F414 for the F-14B had a life of 1000 hrs. Most airliners had engine lifes of over 4000 hrs. In the MIG-25 the engine lifetime meant that the engine had to be scrapped as it was not economical to repair.

One of the biggest factors that cause short engine life is turbine blade creep. That is the deformation of the blades due to high temperatures. The blades are normally made, in todays engines from a nickel superalloy. One of the issues for engine builders is predicting the deformation of the blades with temperature. It requires the manufacturer to understand the deformation physics in detail, down to the molecular level and predicting it with computer sims. Keep in mind that a 20 degree Celsius increase in turbine inlet temperature can lead to a .5% increase in fuel economy which for a fighter means increases in range and a lower fuel load. That translates to higher payloads for a given range. So it is vital. Russian and Chinese developers are notoriously bad in these areas because of the lack of specialized metals and computer sims to predict this sort of problem. There are two conditions for it; Low temp and high stress; high temp and low stress. Both of these conditions will cause creep in the engine.

All rotating areas of the engine will be subject to creep but the compressor sections don't experience it much, due to the much lower temperatures. They will experience cracking and impact deformation from small objects in the atmosphere. The shafts that the turbine and compressors are mounted on will experience bending and deformation simply from use. You can also have lubrication issues. Bearing failures are really prevalent in engines and I suspect this engine is having these kinds of problems. Bearing alloys, construction and lubrication along with design of the bearing structure is absolutely critical. Too much stress on the bearings from a reduced support structure and it does matter how much oil you put on the bearing. Bearing and load inspection is absolutely critical This is vital in high performance aircraft especially.

Anyway, those are just some of the issues that can lower engine life. One factor in engine life is simply good day to day maintenance and inspections. Our boys are good at it, theirs are not.

Apologies to Steel, I knew this answer so I provided it.

[steel_selachian]

Hi Ed:
The lifetime figure means that the engine has to be removed and overhauled after 30 hrs. That is extremely low for any aircraft. The TF-30's in the F-14 had a life of 700 hrs before removal for maintenance, the F414 for the F-14B had a life of 1000 hrs. Most airliners had engine lifes of over 4000 hrs. In the MIG-25 the engine lifetime meant that the engine had to be scrapped as it was not economical to repair.

One of the biggest factors that cause short engine life is turbine blade creep. That is the deformation of the blades due to high temperatures. The blades are normally made, in todays engines from a nickel superalloy. One of the issues for engine builders is predicting the deformation of the blades with temperature. It requires the manufacturer to understand the deformation physics in detail, down to the molecular level and predicting it with computer sims. Keep in mind that a 20 degree Celsius increase in turbine inlet temperature can lead to a .5% increase in fuel economy which for a fighter means increases in range and a lower fuel load. That translates to higher payloads for a given range. So it is vital. Russian and Chinese developers are notoriously bad in these areas because of the lack of specialized metals and computer sims to predict this sort of problem. There are two conditions for it; Low temp and high stress; high temp and low stress. Both of these conditions will cause creep in the engine.

All rotating areas of the engine will be subject to creep but the compressor sections don't experience it much, due to the much lower temperatures. They will experience cracking and impact deformation from small objects in the atmosphere. The shafts that the turbine and compressors are mounted on will experience bending and deformation simply from use. You can also have lubrication issues. Bearing failures are really prevalent in engines and I suspect this engine is having these kinds of problems. Bearing alloys, construction and lubrication along with design of the bearing structure is absolutely critical. Too much stress on the bearings from a reduced support structure and it does matter how much oil you put on the bearing. Bearing and load inspection is absolutely critical This is vital in high performance aircraft especially.

Anyway, those are just some of the issues that can lower engine life. One factor in engine life is simply good day to day maintenance and inspections. Our boys are good at it, theirs are not.

Apologies to Steel, I knew this answer so I provided it.

Hey, that's why we tolerate having you around :p

As a further note, the WS-10 is apparently the first Chinese production turbofan to feature single-crystal blades, which is a key means of tolerating higher engine temperatures without deforming the fan blades.

[old_pop2000]

Hey, that's why we tolerate having you around :p

As a further note, the WS-10 is apparently the first Chinese production turbofan to feature single-crystal blades, which is a key means of tolerating higher engine temperatures without deforming the fan blades.

And I thought it was my handsome face, rats. :cool:

http://iweb.tms.org/SUP/processuperalloys/01-1022-205.pdf

[Ed Rotondaro]

Dennis and Steel:

I can understand now why having spares either parts or total systems (engines, avionics) are just as necessary as the plane itself. Considering that modern warfare demands many sorties by an airforce (naval or ground) to suppress the other side's CCC as well as military assets, any aircraft with WS-10 engine would not be able to function for very long. The war would be over before the engine was rebuilt. Thanks for the info.

[old_pop2000]

...
I can understand now why having spares either parts or total systems (engines, avionics) are just as necessary as the plane itself. Considering that modern warfare demands many sorties by an airforce (naval or ground) to suppress the other side's CCC as well as military assets, any aircraft with WS-10 engine would not be able to function for very long. The war would be over before the engine was rebuilt. Thanks for the info.

Hi Ed:

One last comment about this. The Chinese will have to improve that engine's reliability to well over 300 hrs. This is a very heavy aircraft and will not fly well on one engine, if at all. Engine removal is not a task performed at forward airfields, the equipment such as engine dolly's and such, are too heavy to move forward and too valuable along with the technicians. So, the plane will have to be flown to a rear area airfield and serviced at that point. Now, the squadron will be a plane short, so that has to remedied by sending a replacement aircraft forward. Engine replacement on modern aircraft is much easier, since all you have to do is unzip the dzus fasteners, disconnect the fuel and electrical lines, run the engine dolly underneath the engine and crank it up underneath, disconnect the engine bolts to the mounts, and lower the engine, dropped the dolly and slide the engine out the bottom of the plane. Sounds simple, but it really requires some good techs to do it cleanly and quickly. You then slide the new engine into place, reconnect the lines, fasten the engine bolts, then test the engine before securing the fuselage panels.

Keep in mind, that now that the old engine is out, it has to be transported to an engine test and repair facility which might not be close. This begins the process of attrition on your supply of engines. Also, battle damage and in-flight engine failures can damage the engine and structure along with electrical lines, fuel lines, pneumatic lines and hydraulic lines along with supporting structures.

Other aspects that are not in the brochure knowledge, will be attacks on road networks, airfields that will disrupt this whole logistic process. Lack of spares to repair engines etc. One procedure that is important, is ground testing of the aircraft. On forward airfields, you will normally use engine power to perform the tests, but that will eat into the flight hours. Normally at rear area airfield, you have ground air conditioners and ground power units to eliminate that problem. They are few and far between but more importantly, they are heavy. This problem will easily eat up hours in flight time. It will take at least thirty minutes to preflight any aircraft before a combat mission. That varies depending on the mission and the number of sorties.

In summary, aircraft specifications and brochure knowledge are not the entire story, logistic support is the key to flight and combat. Fighter aircraft in combat, overstress structures and this can be transmitted to systems attached to that structure. This isn't a 737 which takes off, flies straight and makes gentle turns to land. The Chinese will not deploy this bird, without adequate support, I don't care how fancy it is. Pilots are notoriously hard on engines in combat shortening the flight hours. There are also other periodic checks that must be performed that do not require the engines removal, but are necessary. Aircraft availability decreases rapidly as combat operations progress without a good support structure for the birds.

Sorry for the lecture.

[old_pop2000]

Just to put some numbers on this concept of maintenance versus flight hours. The F-14 required about 50 hrous of maintenance for every flight hour. The F-18 Hornet only requires 10 hours of maintenance. The Swedish Saab Draaken requires about 50 manhours and the Eurofighter requires about 9 hours. Generally, the bigger and more complicated the bird, the more maintenance hours that are required. This is especially true for LO aircraft like the J-20, F-22 and others. Mission profiles have much to do with keeping the MMH/FH figures looking good. Beware of the brochure knowledge from the Chinese or the DOD about the J-20 having a MMH/FH that is low. They have to qualify that by type of mission profile. An A-G configuration is much harder on a bird and will increase the MMH/FH considerable. Other variables are:

1. take off rate

2. scheduling effectiveness

3. deviations from the flight schedule

4. total mission and non-mission capable rates.

The second one is vital for LO aircraft. Keep in mind that corrosion of the antiradar coating is of supreme importance and that means a special hanger to perform such maintenance and specialized equipment and materials along with trained maintenance crews.

Training missions for stealth aircraft usually doesn't require stealth, but combat missions certainly do. It all fits into the mix.

At the rate of 10 MMHR/FH, you may only get about two or three sorties per day from the aircraft based on a 24 hr day. Generally, you might fly only 12 to 16 hrs per day to give the flight crews and maintenance crews some rest. Maintenance crews don't rest during missions because there is always ground equipment maintenance and support functions to perform to get ready for the return.

[old_pop2000]

Just some thoughts about the J-20 and its stealth materials. Modern stealth aircraft generally have four methods of reducing the RCS and preventing the detection of the bird by bistatic radar system. They use a radar absorbing metal structure (classified) and radar absorbing materials along with shaping to prevent the detection. RAM is very maintenance intensive, although the USAF is now testing a new coating for the F-22 to reduce that maintenance. Frequently accessed panels must be inspected and resealed after every use. Nicks, corrosion etc. must be checked regularly. We have experience in the servicing of this material, the Chinese probably do not. Just because the J-20 is shaped like the F-22 and painted black, does not mean that it has all of that material or that its quality is the same or that they understand how to maintain it. RAM maintenance can contribute about thirty percent extra maintenance time to any aircraft. Brochure knowledge will not answer those series of questions. And they are serious questions. As I have stated, this is a very heavy large aircraft, which will work against stealth, so while it might be billed by DOD as a something to be concerned about, remember the concept of mirror-imaging. The characteristic of using your capabilities and applying them to your opponent. Don't assume because we have the material science and technology along with the maintenance capabilities, that the Chinese have the same capabilities. Mirror-imaging is what caused the furor over the Mig-25 until we obtained a copy and found it to be a real dud.