Vulnerability of liquid cooled engines

[Jenisch]

Hello,

Liquid cooled engines have a popular fame of being vulnerable. In the case of the P-51, this is well know. However it's practically not mentioned in the case of other acft like the Spit, 109 and Yak. And perhaps what is most curious: the IL-2 used a liquid cooled engine.

I'm wondering at which point such "vulnerability" is a myth or not...

 

[tyrodtom]

Look at a cutaway of a IL-2, and you'll see lots of armor of various thickness covering all the important points.
A good example is the coolant radiator, it has a air intake in front of the cockpit, that then goes down to below the floor to the radiator itself buried in the middle of the fuselage, protected on all sides by armor.

 

[CobberKane]

there was a pretty comprehensive thread on this forum a while back concerning the relative durability of radial v inline engines. One body of thought held that the difference between was overstated, the other was that the weight of anecdotal evidence and pilot opinion was right and the radial engines were much more battle resistant. Personally I'm in the latter camp. There are just too many accounts of radial engine fighters returning with massive engine damage, and as many of inline engines stopped by minor hits to the cooling system

 

[Shortround6]

Comparing a protected engine/radiator like an IL-2 to a naked engine installation isn't quite fair unless you count the the weight of the protection (armor) as part of the powerplant.

Some radials had partially armored cowling and or armored oil coolers. We start arguing about the amount of protection each engine had instead of the engines themselves.

 

[Balljoint]

While not statistically sound, the film of the navy fighter –probably a Hellcat- still on the arresting cable with white hot metal gushing from the engine cowling makes a strong case.

 

[Ainene]

Hello,

Liquid cooled engines have a popular fame of being vulnerable. In the case of the P-51, this is well know. However it's practically not mentioned in the case of other acft like the Spit, 109 and Yak. And perhaps what is most curious: the IL-2 used a liquid cooled engine.

I'm wondering at which point such "vulnerability" is a myth or not...

P-51 is obviously getting compared with other American fighters.
But comparing with lighter European fighters... 3 fighters you mentioned(spit, bf-109, yak) - all were among easier ones to shoot down(damage-absorbing ability wise).
And Il-2 is very good example: how heavily armoured craft's survivability may be lowered thanks to water-cooled engine, with radiator(underbelly) damage among the most stable loss reasons.
example:
from soviet Il-2 pilot interview:

Один раз уже на пути домой: смотрю, температура воды больше 100 градусов. Видимо, в маслорадиатор попал осколок или пуля. Ведь в атаке бронезаслонку мы не закрывали — жарко, а двигатель работал на полной мощности. Это можно делать, только если погода прохладная, иначе мотор перегревался. Пришлось садиться в поле. Сел, покатился, остановился. Вылез из кабины и пошел по колее посмотреть. Оказалось, что в самом начале пробега самолет перепрыгнул траншею. Хорошо, что траншея была с бруствером и был запас скорости, а то бы скапотировал или сломал бы «ноги» шасси. Пришел домой: «Сержант Пургин, сел на вынужденную». В тот же день самолет привезли на машине.
В другой раз атаковали, вывел самолет из пикирования — та же история: давление масла падает, температура растет. Надо садиться на вынужденную, а РС еще не сбросил. Отстрелил РС. Скорость большая, высота — метров пятьдесят, а впереди, в трех километрах, — лес. Вот и решай, то ли машину разбить и самому погибнуть, пытаясь посадить ее на большой скорости, то ли скорость гасить, но тогда точно в лесу разобьешься. Кое-как, юзом, сбросил скорость, плюхнулся в поле. Когда меня потащило, то я по инерции дернулся вперед, и предохранительная скоба гашетки, которую я забыл закрыть, ударила меня в правый глаз. Выскочил из кабины, — я же не знаю, куда сел, то ли у наших, то ли у немцев — побежал в кусты, что росли у речки. Залез. Видеть уже могу только одним глазом. Смотрю, бегут из леса к самолету люди, добежали до самолета и бегут ко мне. Я пистолет достал, приготовился отстреливаться. Смотрю, звезды на фуражках, оказалась наши энкавэдэшники. Меня взяли, отвезли к врачу. Врач посмотрел: «Ничего, глаз не поврежден. До свадьбы заживет». Дал полстакана спирта, я выпил и пошел спать в сарай. Утром опухоль спала, глаз стал открываться. Собрался, позавтракал у них и пошел на аэродром.
Третий раз меня сбили, когда мы ходили на штурмовку станции Мерефа, южнее Харькова, который был у немцев. Наши войска еще только готовились к его штурму. Вел нас комэск Нютин. Атаковали станцию, а на выходе нас атаковал один «мессершмит». Надо же ему было попасть мне опять в маслорадиатор! Та же история — давление упало. Группа развернулась влево, а я, решив, что линия фронта ближе справа, развернулся туда. С трудом перетянул машину через город, тракторный завод, который был у немцев, прошел ниже труб и сразу за ним упал в поле с копнами сена.

Google translation(fixed it a bit)

One time on the way home: look, the water temperature is greater than 100 degrees. Apparently, the oil cooler had a splinter or a bullet. After the attack, we did not close bronezaslonku(=armoured door) - hot and the engine is running at full capacity. This can be done only if the weather is cool, or the motor overheating. I had to get into the field. He sat down, rolled and stopped. Got out of the plane and went on the track to watch. It turned out that at the beginning of run aircraft jumped the trench. Well, that was a trench parapet and had a stock speed, but it would skapotiroval(=nosed over) or would break the "legs" chassis. I came home, "Sergeant Purgin, sat on an emergency." On the same day the aircraft was brought to the car.
At other times attacked, brought the plane out of a dive - the same story: the oil pressure drops, the temperature rises. It should be forced to sit on, and the PC is not folded. Shot off the PC(RS-82). Great speed, height - fifty meters, and in front, three kilometers - wood. So decide, whether a plane smash and kill yourself trying to put her at high speed, or the speed to put out, but then just break it in the woods. Somehow, skid, slowed, plopped down in a field. When I was dragged, I jerked forward by inertia and trigger guard trigger, I forgot to close, hit me in my right eye. Jumped out of the car - I do not know where I landed, or our, or the Germans - ran into the bushes that grew by the river. Climbed. I can already see with only one eye. Look, running out of the forest to the airplane people ran to the plane and run to me. I've got a gun, ready to shoot. Watching the stars on their caps, was our enkavedeshniki(NKVD). I was taken, was taken to the doctor. The doctor looked, "Nothing, eye is not damaged. Before the wedding will live. " Given half a glass of alcohol, I drank and went to sleep in the barn. Morning swelling subsided, his eyes open. Going, they had breakfast and went to the airport.
The third time I was shot down when we went to attack the station Merefa, south of Kharkov, which was in German hands. Our troops were still preparing it's assault. Nyutin squadron commander led us. Attacked the station, and at the output we were attacked by one "Messerschmitt". Wow he had to get me back into the oil cooler! The same story - the pressure dropped. The group turned to the left, and I decided that the front line was closer to the right, turned back. Hardly a car pulled through the town tractor factory, which was the Germans, was below the pipe and immediately after it crashed into a field with haystacks.

 

[dobbie]

Unless there is armor applied, the liquid cooled engine is going to be more vulnerable than an air cooled engine simply because of the fact that the radiator and the piping present more area. And with an air cooled engine, less armor would be needed to protect it because you have less mass to cover.

 

[tomo pauk]

...
And Il-2 is very good example: how heavily armoured craft's survivability may be lowered thanks to water-cooled engine, with radiator(underbelly) damage among the most stable loss reasons.
example:
...

Thanks for posting the excerpt.
The radiator at underbelly was oil cooler, the water-glycol cooler being well protected in the tunnel shaped like shallow S letter. The experienced LW fighter pilot would try to sneak under and give it a burst or more; the experienced Stormovik pilot will of course try to deny that opportunity. Those less experienced being majority, however.

 

[davebender]

Liquid cooled engine block is probably tougher then an air cooled engine.

Wing mounted radiators and associated piping are the real problem. An easy way to place the heavy cooling system over aircraft center of gravity but fatal if aircraft gets shot in the wing.

 

[davebender]

Why go to that trouble if you have 20mm cannon with decent HE shells? Just rip big holes in the unarmored wings.

 

[drgondog]

A challenge for the statistics hounds is to narrow the data to relevant 'packages'

What was the threat envirionment?

What was the probabilty of a fatal hit at the altitude, speed and time acquired as a target?

How many times was the subject aircraft/powerplant exposed to a high threat environment?

What is the % of defined and verifiable losses?

Any set of data that anybody is aware of that address these discrimants?

 

[Ainene]

Why go to that trouble if you have 20mm cannon with decent HE shells? Just rip big holes in the unarmored wings.

Another hint:
(soviet statistics)
More then 20% damaged craft had damage to wings, but only 3% to oil cooler. Of aircraft that made it back(i.e. landed safely/crash-landed on field),not shoot down.
Il-2 was quite resistant to simple holes, and control wires in the wings were reserved. It is possible, but for this kind of kill better shoot tail(here control can be denied by single lucky shell,and tail control surfaces much simpler to rip off anyway).

 

[davebender]

MG151/20 fired 750rpm and 20mm mine shells contained 18 grams of HE. Why wouldn't you hit IL2 wing with several shells, each of which punches a 1 foot or larger hole? Single hit might not be fatal but 5 probably will be.

 

[GregP]

Regarding post # 11 Drgondog, as an engineer, it has always been my contention that if you don't save the data, there is virtually no chance of using it to discover how to best improve the process. I have always wanted to save the data once avionics became good, and use it to analyze missions for potential improvement. For instance, with today's avionics, it should be possible to know how many bullets/missiles. Etc. were shot, at what speed, at what power level, at what attitude and rate of climb or descent, at what angle, the g-load, and the relative coordination of the turn and bank indicator.

Even in WWII, it should have been possible to install bullet counters and have gun cameras on most WWII fighters. The fact that we didn't pay attention to these data mean the sum total of the biggest aerial war in history is difficult or impossible to analyze correctly since the available data are so inconsistent in their availability and are largely totally missing.

There is almost no excuse in modern warfare. The measn to record such things are light, relatively inexpensive relative to the rest of the aircraft, and would simplify analysis in all encounters.

 

[tyrodtom]

I remember in Hartmanns book he mentioned aiming for the oil cooler, as being his favorite way of bring down the IL-2.
The wings from behind are not a very big target, and if the other aircraft is manuvering, they're always changing position relative to you, while the fuselage will be in a more constant position as you mannuver with the other aircraft.

 

[Ascent]

The Mosquito and Beaufighter were both used in the anti shipping role, often on the same missions. Both are twin engined ,one is liquid cooled, the other air.

Do we have any direct comparison about engine survivability between the two?

 

[davebender]

Experts such as Hartmann can aim for the relatively small oil cooler. Normal pilots aim for center of mass and are lucky to land a burst on target.

 

[R Pope]

A bullet in the rad would be much more serious in a Mustang over Berlin than say a Spitfire over
London.......

 

[Jenisch]

Dont know if started in specific model, but the 109 could fly with a radiator out.

 

[Shortround6]

Only specifically equipped aircraft of certain models.