A Chinese AF Fighter Jet Crashed Near Chengdu

thunderchief

thunderchief

Senior Member
Considering that dilemma about one or two-engined fighter , there is actually whole mathematical theory explaining and modeling various pros and cons . I will try to explain simplest possible example :

Let's assume we have J-10 with one AL-31 engine and Su-30 with two of the same . To simplify matters we will also assume those engines to be identical , with same probability of failure . For example Pf=0.01 at 100 hours (I invented those numbers , they don't have anything to do with real engines ) .

Now, for a J-10 , probability of crash after 100 h would be 1% and probability of fully operational status would be 99% (1-Pf) . Again, as I said, I disregarded other factors .

But for a Su-30, probability of crash (failure of both engines) would be Pf x Pf = 0.0001 i.e. 0.01% . So far so good , you would say . But probability of fully operational status would be (1-Pf) x (1-Pf) = 0.9801 i.e. 98.01% , lower then J-10 ! because Su-30 needs both engines in running condition to be fully operational . Su-30 has 1.98% chance for developing problems on one engine (either of them) and remaining grounded (although not destroyed) .

Therefore, if you decide to buy two-engined fighters instead of those with single engine, you would probably start with smaller number (twin-engined planes are usually more expensive then single-engined ones ). You would have less total write-offs , but at the same time you could expect less overall availability of your planes .
 
N

no_name

Colonel
kwaigonegin said:
Fighter pilots have nerves of steel after all they are conditioned and trained to do what they do! There have been literally hundreds of cases if not thousands where pilots flew with a lost wing, shredded fuselage, and what not. Heck if you take WWII into account the heroics of fighter pilots is almost legendary including the kamikazes.

Test pilots are a breed even above that. Was he rattled? .. sure but I guarantee you he didn't have to change his skivvies afterward like what most of us would probably have done.

Another case of a pilot who fought with the controls to avoid populated area and stayed with his damaged jet the entire way in was Yuri Gagarin. He was a hero when he was alive and he truly died a hero's death as well.
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And the most ballsy of all I think would be astronauts, at first selected from among test pilots. The first guy to go into space and the first to land on the moon have to be very collected individuals.

-Isolated from rest

-No previous experience/cases to draw from

-If something happens you are pretty much on your own.

-Every single strange vibrations/sounds is gonna drum on your nerves.
 
kwaigonegin

kwaigonegin

Colonel
thunderchief said:
Considering that dilemma about one or two-engined fighter , there is actually whole mathematical theory explaining and modeling various pros and cons . I will try to explain simplest possible example :

Let's assume we have J-10 with one AL-31 engine and Su-30 with two of the same . To simplify matters we will also assume those engines to be identical , with same probability of failure . For example Pf=0.01 at 100 hours (I invented those numbers , they don't have anything to do with real engines ) .

Now, for a J-10 , probability of crash after 100 h would be 1% and probability of fully operational status would be 99% (1-Pf) . Again, as I said, I disregarded other factors .

But for a Su-30, probability of crash (failure of both engines) would be Pf x Pf = 0.0001 i.e. 0.01% . So far so good , you would say . But probability of fully operational status would be (1-Pf) x (1-Pf) = 0.9801 i.e. 98.01% , lower then J-10 ! because Su-30 needs both engines in running condition to be fully operational . Su-30 has 1.98% chance for developing problems on one engine (either of them) and remaining grounded (although not destroyed) .

Therefore, if you decide to buy two-engined fighters instead of those with single engine, you would probably start with smaller number (twin-engined planes are usually more expensive then single-engined ones ). You would have less total write-offs , but at the same time you could expect less overall availability of your planes .
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The rule of thumb is if you can afford it always go twin engines. the only exception is if you the numbers to make up for operational deficiencies.

Obviously engine reliability is key as the more reliable an engine is the overall availability of a single is closer to that of the twin. These are the things politicians don't think about when making large capital purchases.

I would not buy the J10 for those reasons unless I can afford more than I need especially if I'm a small country. Same with the F35 but luckily the F135 is more realiable than the Al31 or even Ws10 and most partner countries in the JSF program have the advantage being 'in-network' i.e NATO and can rely others to help in times of need.

This is another reason why China really needs to step up in making their own indegenous turbofans with higher reliability and lower maintenance cycles but they already know that I think.
 
Quickie

Quickie

Colonel
Janiz said:
I doubt he was aiming for anything in particular. At best not hitting any heavily inhabited area.
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Well, he knew his aircraft was heading down towards the row of buildings. He couldn't avoid crashing into the buildings but he probably could still control his aircraft to crash into the least damaging part of the buildings, which was the fountain/staircases. If he wasn't aiming the fountain/staircases, the aircraft would have more likely missed the fountain/staircases due to its much smaller size compared to the size of the rest of the buildings.
 
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pflanker

New Member
kwaigonegin said:
I would not buy the J10 for those reasons unless I can afford more than I need especially if I'm a small country. Same with the F35 ....
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I think you misread Thunderchief's post. He was saying, counter intuitively single engine planes have statistically higher percentage of availability at time of war.

It is not completely pulling wool over everyone's eyes. If you have twin engines, the chance of either one or both engines needing repair is higher than if you have just a single engine. When action starts, more twin engine planes will be in the shop than single engine ones (not available for action given same number on both sides).

However, the equation gets more complicated when you also consider planes surviving engine failures. With good engine maintenance and low engine failure rate, the number of planes available should be about the same. Single engine has advantage of economy to acquire and operate
 
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thunderchief

thunderchief

Senior Member
pflanker said:
I think you misread Thunderchief's post. He was saying, counter intuitively single engine planes have statistically higher percentage of availability at time of war.
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Maybe I should make one historical example ;) For long time Mig-21 was favorite fighter plane of poor and undeveloped countries . Despite God-awful crash rate, somehow lot of them were always available for war. Having low price and relatively simple maintenance of course had to do lot with it .

Surprisingly, lot of those countries in modern times ordered Su-30 , complete opposite of Mig-21 (large,complex, twin-engined fighter) . Now, comparing with Mig-21 , Su-30 record is much better, with very few crashes , owning to the twin-engined configuration above anything else . But also, unlike Mig-21, lot of Su-30s are simply grounded for various maintenance-related reasons . In fact, countries like Venezuela or Indonesia may have all of their fighters accounted for, but very few of them would be available in case of war .

Therefore, there is a very fine calculation with many parameters which would yield optimum solution (i.e. fighter type) for given country , taking notice of financial status , potential adversaries, technological level etc ...
 
M

Mika Montero

New Member
Registered Member
antiterror13 said:
Also this incident could be a "blessing in disguise" .. it will force China to develop its own engine (e.g WS-10B) more seriously (even at the moment very very serious) and pump more $$$$$$
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"more seriously (even at the moment very very serious)" means = staffing all 90% of the engine development engineers with Right_Brain type (or Think without the Box type).

100 million Left_Brain type engineers (or Think inside the Box type) will not break this engine development bottleneck.

Am I right to say ... ... ??
... ...Unfortunately, in China, their system only reward the "Left_Brain type" who can flash and show their shiny famous university diploma.

In China, there are plenty of "innovative and genius farmers" who had invented many unusual items, but nobody give them any support to further develop their ideas, or invite those "innovative and genius Chinese farmers" to join engine development team.

:( Sadly because, they are just farmers who have never attended any formal schooling, right ?
 
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kwaigonegin

kwaigonegin

Colonel
pflanker said:
I think you misread Thunderchief's post. He was saying, counter intuitively single engine planes have statistically higher percentage of availability at time of war.

It is not completely pulling wool over everyone's eyes. If you have twin engines, the chance of either one or both engines needing repair is higher than if you have just a single engine. When action starts, more twin engine planes will be in the shop than single engine ones (not available for action given same number on both sides).

However, the equation gets more complicated when you also consider planes surviving engine failures. With good engine maintenance and low engine failure rate, the number of planes available should be about the same. Single engine has advantage of economy to acquire and operate
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Agreed. In times of war availability is more important than reliability. In a major war most front line fighters are expected to go on one way mission anyway. As long as the engine is 'realiable' enough to spool up and take off that is.

I know back in the 1980's NATO did a comprehensive analysis and came to the conclusion that almost all their fighter inventory will be depleted by the 6th week mark against any Warsaw Pact invasion in the European theater. After that it's basically tactical nukes once conventional arms are all but gone or destroyed. Luckily for all of us that scenario never became a reality!
In some ways the extreme cost and sophistication of manufacturing modern arms have made it impossible to keep up with war attrition even on the 'winning' side. Unlike WWII you don't really need to bomb as many factories. Back then they can churn out mustangs and Shermans like cupcakes.. Nowadays not so much.
 
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