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Engine failure due to main bearings failure?


Hiromachi

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Yesterday, during evening flying session two instances of engine failure occured to me. Previously I had no issues with FW-190 engine operation and last failure happened over a year ago, so I was pretty stunned.

So what have happened is that during the dive I felt as if I hit a wake turbulance or something of this nature, with aircraft shaking pretty violently. Immediately after this my RPM went to 0 and MP gauge shown fluctuating needle, jumping from 1.1 to 1.4 Ata. But engine clearly produced no power and attempts to restart it failed. Fortunately I was able to glide myself back home.

 

Second time I experienced similar behavior as well during the dive, when I tried to follow the target below. Same story, weird engine behavior and then complete loss of power. Second time in less than 2 hours and I knew this wasnt accident or random situation, but something else.

And then I was reminded of this:

Supercharger is adjusted for TO (or wet WEP if available) MP at SL at full throttle at low speed. Ram pressure, though, can be a problem, but the speed builds up not too fast to make MP adjusting unavailable.

At climb at higher altitudes the MP can be higher than at the SL.

 

The new kind of failures we will introduce is a main bearings failure due to LOW MP... in less than a minute the bearings will be dead. Thus, it will cure the bad habit to retard throttle at high speed.

https://forums.eagle.ru/showpost.php?p=4053153&postcount=1900

 

Yes, in both instances I was descending at high speeds (600+ km/h) with throttle partially closed (1.4 - 1.5 Ata or more). Thus, the brief explenation above fits the factual situation and results. Yet I dont recall this mechanic being explained in depth in any changelog, so I would like to ask Yoyo if he could provide more extensive description.

Most importantly:

- why it happens ? I thought that main bearing failure is caused by lugging the engine, thus it shouldn't happen when you retard the throttle because there is very low load. Or I could see damage to bearings when moving throttle suddenly and in a wide range (i.e. slamming forward or something);

- what is the safe limit of engine operation vs speed ? I mean, throttle is the main mean to control acceleration in descend. One doesnt want to overspeed and exit dive with no wings, so running with full throttle might not be the good idea at all times in dive.

- how can it be observed prior to happening ? I cant recall seeing any feedback prior to it happening.

 

Thank you for the answer in advance. I'd really like to learn more about to avoid such situations in the future.

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I’ve had some lurch in the p51 lately in high speed dives, guess this explains it pretty cool it’s in already.

 

My observations in p51 was a sudden yaw movement due to engine not providing any torq, like you at first I thought it was wake turbulence but when the engine and MP dropped out was like oh boy what’s this...


Edited by Sniper175

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I'm not a mechanical expert and would like to understand by which causality chain low manifold pressure will cause main bearing failure. I would expect such a failure when there is lack of lubrication but fail to see how low MP would disrupt lubrication. Can somebody explain?

LeCuvier

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  • ED Team
Yesterday, during evening flying session two instances of engine failure occured to me. Previously I had no issues with FW-190 engine operation and last failure happened over a year ago, so I was pretty stunned.

So what have happened is that during the dive I felt as if I hit a wake turbulance or something of this nature, with aircraft shaking pretty violently. Immediately after this my RPM went to 0 and MP gauge shown fluctuating needle, jumping from 1.1 to 1.4 Ata. But engine clearly produced no power and attempts to restart it failed. Fortunately I was able to glide myself back home.

 

Second time I experienced similar behavior as well during the dive, when I tried to follow the target below. Same story, weird engine behavior and then complete loss of power. Second time in less than 2 hours and I knew this wasnt accident or random situation, but something else.

And then I was reminded of this:

 

https://forums.eagle.ru/showpost.php?p=4053153&postcount=1900

 

Yes, in both instances I was descending at high speeds (600+ km/h) with throttle partially closed (1.4 - 1.5 Ata or more). Thus, the brief explenation above fits the factual situation and results. Yet I dont recall this mechanic being explained in depth in any changelog, so I would like to ask Yoyo if he could provide more extensive description.

Most importantly:

- why it happens ? I thought that main bearing failure is caused by lugging the engine, thus it shouldn't happen when you retard the throttle because there is very low load. Or I could see damage to bearings when moving throttle suddenly and in a wide range (i.e. slamming forward or something);

- what is the safe limit of engine operation vs speed ? I mean, throttle is the main mean to control acceleration in descend. One doesnt want to overspeed and exit dive with no wings, so running with full throttle might not be the good idea at all times in dive.

- how can it be observed prior to happening ? I cant recall seeing any feedback prior to it happening.

 

Thank you for the answer in advance. I'd really like to learn more about to avoid such situations in the future.

 

I have no idea about the failure. Main bearings failure is only on its way to the project. The track could help.

Ніщо так сильно не ранить мозок, як уламки скла від розбитих рожевих окулярів

There is nothing so hurtful for the brain as splinters of broken rose-coloured spectacles.

Ничто так сильно не ранит мозг, как осколки стекла от разбитых розовых очков (С) Me

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  • ED Team
I'm not a mechanical expert and would like to understand by which causality chain low manifold pressure will cause main bearing failure. I would expect such a failure when there is lack of lubrication but fail to see how low MP would disrupt lubrication. Can somebody explain?

 

The mechanics of the piston rod and crankshaft is balanced with regards of inertia forces and gas pressure forces. At low MP lack of gas pressure forces causes more disbalance and higher bearing loading.

Ніщо так сильно не ранить мозок, як уламки скла від розбитих рожевих окулярів

There is nothing so hurtful for the brain as splinters of broken rose-coloured spectacles.

Ничто так сильно не ранит мозг, как осколки стекла от разбитых розовых очков (С) Me

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At low MP prop starts shifting from pulling to braking the plane so the forces are shifted, But as i think about it V 12 are less prone to this typ of damage because number of main bearing per cylinder is much greater then in radial engine.

It simply looks like this you want to keep some tension on internal parts of the engine and you don't want to be cranking loose at high rpm, Same with rollers bearing if it is not loaded properly rollers can stop rolling and it will kill bearing quick.

I don't remember exactly in which NK-8 or D-30 engines designers reduced rollers numbers(half) in one of the shaft bearings because of low bearing load, later 2 il 62s crashed during catastrophic engine fail it came out that bearing was loaded too much.


Edited by grafspee

System specs: I7 14700KF, Gigabyte Z690 Aorus Elite, 64GB DDR4 3600MHz, Gigabyte RTX 4090,Win 11, 48" OLED LG TV + 42" LG LED monitor

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Hi all,

yes this is true. Mass, Inertia, and Centrifugal Force are balanced in the engine/propeller assembly, when cruising, however the propeller is constantly trying to move forward faster than the aircraft is. in other words the propeller is constantly trying to rip itself from the engine, due to the forward thrust of the propeller. The engine is built to withstand this forward motion, through thrust bearings, and the thrust in the gear train is actually designed too pull rearwards on the prop and crankshaft to help compensate.(this is important). so we wing over in a dive. the problems occur when the propeller starts to drive the engine, instead of the engine driving the propeller. in example, diving at less than full pitch on the prop or suddenly pulling back on the power in a dive... the prop just wants to separate from the engine,((reduction gear)) plus the gear train is loaded in the opposite direction, because the prop is driving the engine, instead of the engine driving the prop , as designed. the Anton had similar issues with breaking the supercharger impeller shaft, but it was a gear train backlash issue at low (under 1000) RPM, due to the rough running of the radial engine causing chatter in the gear train, and the impeller shaft was the weak link in the chain.

Yo-Yo is right when he said there may be some hurt feelings when the P-47 drops, just in engine management wise, as the 2800 goes, (and all radials)... if it had a weak link, the main bearings were it. man I want my Jug.

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thank you I am glad it helped. it is really due to working the powertrain in the opposite direction of witch it is designed., and as the Jumo goes, If I remember correct, it had roller bearings on the crank and rods, so bearing thrust was even more critical

We are Virtual Pilots, a growing International Squad of pilots, we fly Allies in WWII and Red Force in Korea and Modern combat. We are recruiting like minded people of all Nationalities and skill levels.



http://virtual-pilots.com/

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If engine is equipped with prop reduction gear box i think reversed thrust will not affect engine crank shaft it self but only the gear box. I think main bearings fail is due to what Yo-Yo said.

Yo-Yo will we get fatal gearbox case fail in extreme dives so we can loose prop some day ? Last i checked i climbed to 40k ft and dived straight down nothing happened


Edited by grafspee

System specs: I7 14700KF, Gigabyte Z690 Aorus Elite, 64GB DDR4 3600MHz, Gigabyte RTX 4090,Win 11, 48" OLED LG TV + 42" LG LED monitor

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  • ED Team
If engine is equipped with prop reduction gear box i think reversed thrust will not affect engine crank shaft it self but only the gear box. I think main bearings fail is due to what Yo-Yo said.

Yo-Yo will we get fatal gearbox case fail in extreme dives so we can loose prop some day ? Last i checked i climbed to 40k ft and dived straight down nothing happened

 

No, the main damage is exactly for the cranck shaft bearings for the reason that the plain bearings are very sensitive to the local pressure. And, by the way, for some radial engines the power-on pressure was very close to the maximal for the allowed for bearings alloy. So, any, power-off disbalance leads to overstressing.

Ніщо так сильно не ранить мозок, як уламки скла від розбитих рожевих окулярів

There is nothing so hurtful for the brain as splinters of broken rose-coloured spectacles.

Ничто так сильно не ранит мозг, как осколки стекла от разбитых розовых очков (С) Me

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No, the main damage is exactly for the cranck shaft bearings for the reason that the plain bearings are very sensitive to the local pressure. And, by the way, for some radial engines the power-on pressure was very close to the maximal for the allowed for bearings alloy. So, any, power-off disbalance leads to overstressing.

 

I was talking about forces on shaft created by prop drag, when gear box is present and prop no longer pulling or pushing crank shaft in engine case, so how this can affect crank shaft in any way.(forces parallel to crank shaft axis)

I though that main crank shaft is mounted on the rolling bearings in radial engines not plain bearings, probably im wrong about it.

German planes are the best if you cut throttle Control unit will reduce rpm problem solved :)


Edited by grafspee

System specs: I7 14700KF, Gigabyte Z690 Aorus Elite, 64GB DDR4 3600MHz, Gigabyte RTX 4090,Win 11, 48" OLED LG TV + 42" LG LED monitor

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Hi all,

yes this is true. Mass, Inertia, and Centrifugal Force are balanced in the engine/propeller assembly, when cruising, however the propeller is constantly trying to move forward faster than the aircraft is. in other words the propeller is constantly trying to rip itself from the engine, due to the forward thrust of the propeller. The engine is built to withstand this forward motion, through thrust bearings, and the thrust in the gear train is actually designed too pull rearwards on the prop and crankshaft to help compensate.(this is important). so we wing over in a dive. the problems occur when the propeller starts to drive the engine, instead of the engine driving the propeller. in example, diving at less than full pitch on the prop or suddenly pulling back on the power in a dive... the prop just wants to separate from the engine,((reduction gear)) plus the gear train is loaded in the opposite direction, because the prop is driving the engine, instead of the engine driving the prop , as designed. the Anton had similar issues with breaking the supercharger impeller shaft, but it was a gear train backlash issue at low (under 1000) RPM, due to the rough running of the radial engine causing chatter in the gear train, and the impeller shaft was the weak link in the chain.

Yo-Yo is right when he said there may be some hurt feelings when the P-47 drops, just in engine management wise, as the 2800 goes, (and all radials)... if it had a weak link, the main bearings were it. man I want my Jug.

 

The P47D 30 has dive breaks so it's not a huge issue. The P51D on the other hand falls apart around 490 to 505mph.So not being able to idle in a dive will make the P51D so much more painfull to dive in.

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The P47D 30 has dive breaks so it's not a huge issue. The P51D on the other hand falls apart around 490 to 505mph.So not being able to idle in a dive will make the P51D so much more painfull to dive in.

 

P-51 dont have radial engine so wont be affected you just need to follow manual so minimum MP is something like 25"

Btw you can cut throttle but you will have to drop rpm before

-30 had automatic prop pitch so it will lower rpm at lower MP

im kind afraid of modeling this by by ed i already can see jammed engines because you cut throttle at landing approach.

Same with 67" in p-51 once you use it for more then 3 min engine will blow on you even after you land it and turn it of it will bang you in the face :P "BANG"


Edited by grafspee

System specs: I7 14700KF, Gigabyte Z690 Aorus Elite, 64GB DDR4 3600MHz, Gigabyte RTX 4090,Win 11, 48" OLED LG TV + 42" LG LED monitor

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