4.13 development update discussion and feedback

[ElAurens]

Every inline engine I know of has an aluminum engine block, and I rather think that they are not 1 to 2 inches (25 to 50mm) thick.

However, I do agree that the inline engines are too fragile.

Fly the P40 for a while. I'm sure that the tail gunners could simply use
7.65 Browning Walther PPKs and bring them down with one shot.

[Janosch]

^Would you guys, like, have some raw data, like, you know, logfiles, tracks or screenshots to pass around, so others could verify your claims on the (perceived) shortcomings of damage modeling?

[Pursuivant]

Originally Posted by ElAurens

Every inline engine I know of has an aluminum engine block, and I rather think that they are not 1 to 2 inches (25 to 50mm) thick.

I believe that all WW2-era high performance aircraft engines had cast iron blocks and that cast aluminum blocks are mostly post-war. Remember, aluminum was a somewhat scarce resource for many nations during WW2, whereas mild steel was relatively common.

I admit to eyeballing the exact thickness of the engine block using cutaways of Merlin and Daimler-Benze engines. But, remember, inline aircraft engines are big (~3/4 metric tonne, nearly 1 English ton, vs. 200 kilos/300 lb. for auto engines) and are designed to deal with much greater forces than auto engines.

I'm not saying that aircraft engine blocks are bullet-proof by any means, since cast iron is relatively soft and brittle as steel goes. But they're going to be a bit tougher to penetrate than auto engines, which is mostly what you see being shot up by various guns on YouTube.

There are also four different damage states the game engine needs to model for damage effects to inline engines - no functional damage (i.e., pitting of the engine's exterior, but no penetration), penetration of the block around the gearbox (= oil leak and eventual failure or seizure of the engine due to gearbox overheating), penetration of the block around the cylinders (= coolant leak and eventual seizure of the engine due to overheating of cylinders) and the penetration of both the exterior block and one of the cylinders which results in loss of engine compression and a fuel leak in addition to the effects of a coolant leak).

As a variation on penetrating the cylinder, there's also the possibility of damaging one of the pistons, cylinder head or camshafts, or one of the spark plugs or part of the wiring harnes, which would reduce engine compression and possibly cause overheating or engine seizure without the fuel or coolant leak.

Since engines in IL2 are modeled as solid blocks of metal, it seems that the simplest way to model the different types of hits would would just be to assign random percentages of no functional damage, coolant leak, oil leak, fuel leak and compression loss/engine seizure based on bullet energy, with .50 caliber or better bullets having a chance of multiple different hits, but with .30 caliber bullets just getting one type of hit (and with fuel leak/loss of compression/engine seizure hits being very rare).

Given the fluid pressures and temperatures involved, I think that IL2 is realistic, if not a bit generous, in allowing damaged inline engine to survive as long as they do. But, since I'm ignorant about these things I'll defer to others with more experience.

[Pursuivant]

Originally Posted by Janosch

^Would you guys, like, have some raw data, like, you know, logfiles, tracks or screenshots to pass around, so others could verify your claims on the (perceived) shortcomings of damage modeling?

True, if you don't have pictures it doesn't exist!

I will try to upload pictures.

For others who wish to add pictorial evidence, set up a 16 bomber vs. 1 fighter QMB mission and turn arcade mode on.

To prove my point, be sure to use planes with weak rear defensive armament, like the Ju-88A or He-111H, or with massed rifle caliber MG in turrets, like the Wellington.

Use Ace level AI and stupid tactics like hanging out at 100-300 m right behind a bomber formation.

You'll get the results I described soon enough; loads of PK, pilot wounded and badly smoked/seized engines, usually following just a few bullet hits. As a bonus, you'll occasionally get a control cable hit (esp. for the older planes like the Bf-109 or the Soviet fighters) from hits that penetrate the engine and forward firewall.

[Pursuivant]

Pictures

#1: Yak 1B - Pilot arm wound through gap between forward armor plate/engine firewall and cockpit combing at medium-long range.

http://forum.1cpublishing.eu/attachm...1&d=1401765054

#2: P-40B just after getting "shot-shotted" at extreme range through the propeller boss by Ace He-111H-2 gunners. Note the remarkable accuracy since the nearest enemy plane is over 700 meters away! (So much for fixing "sniper" AI gunners. .) I got the "engine overheat" message within seconds after the hit, and the engine was whining badly indicating that engine seizure was going to happen just a few seconds later. This problem seems to be unique to the P-40 series.

http://forum.1cpublishing.eu/attachm...1&d=1401765076

#2 P-40B just after getting shot at medium long range by Ace He-111H-2 gunners at a slight angle off. Engine smoking badly due to oil leak with only a few minutes of life left. The bomber that inflicted the hit was over 300 meters away, just outside of the frame in the upper right hand corner. Note the remarkable grouping of two bullets within 1 foot of each other against a maneuvering target!

http://forum.1cpublishing.eu/attachm...1&d=1401765088

Happy yet?

And, mind you, I didn't have to work for these results at all. They represent 3 consecutive missions!

[ElAurens]

Pursivant, you had better do some more research,

The Merlin had an aluminum engine block with steel cylinder liners.

From Wiki:

Basic component overview (Merlin 61)

From Jane's:[25]
CylindersTwelve cylinders consisting of high-carbon steel liners set in two, two-piece cylinder blocks of cast "R.R.50" aluminium alloy having separate heads and skirts. Wet liners, ie. coolant in direct contact with external face of liners. Cylinder heads fitted with cast-iron inlet valve guides, phosphor bronze exhaust valve guides, and renewable "Silchrome" steel-alloy valve seats. Two diametrically opposed spark plugs protrude into each combustion chamber.PistonsMachined from "R.R.59" alloy forgings. Fully floating hollow gudgeon pins of hardened nickel-chrome steel. Three compression and one oil-control ring above the gudgeon pin, and one oil-control ring below.Connecting rodsH-section machined nickel-steel forgings, each pair consisting of a plain and a forked rod. The forked rod carries a nickel-steel bearing block which accommodates steel-backed lead-bronze-alloy bearing shells. The "small-end" of each rod houses a floating phosphor bronze bush.CrankshaftOne-piece, machined from a nitrogen-hardened nickel-chrome molybdenum steel forging. Statically and dynamically balanced. Seven main bearings and six throws.CrankcaseTwo aluminium-alloy castings joined together on the horizontal centreline. The upper portion bears the wheelcase, supercharger and accessories; and carries the cylinder blocks, crankshaft main bearings (split mild-steel shells lined with lead bronze alloy), and part of the housing for the airscrew reduction gear. The lower half forms an oil sump and carries the oil pumps and filters.WheelcaseAluminium casting fitted to rear of crankcase. Houses drives to the camshafts, magnetos, coolant and oil pumps, supercharger, hand and electric starters, and the electric generator.Valve gearTwo inlet and two exhaust poppet valves of "K.E.965" steel per cylinder. Both the inlet and exhaust valves have hardened "stellited" ends; while the exhaust valves also have sodium-cooled stems, and heads protected with a "Brightray" (nickel-chromium) coating. Each valve is kept closed by a pair of concentric coil-springs. A single, seven-bearing camshaft, located on the top of each cylinder head operates 24 individual steel rockers; 12 pivoting from a rocker shaft on the inner, intake side of the head to actuate the exhaust valves, the others pivoting from a shaft on the exhaust side of the head to actuate the inlet valves.

The Allison V 1710 also had an aluminum block, as did the Daimler Benz DB series, as did the Hispano and it's Russian copies, etc... etc... etc...

If these large (26+ Litre) engine had been made of cast iron they would have been far too heavy for aircraft use.

[Pursuivant]

Originally Posted by ElAurens

The Merlin had an aluminum engine block with steel cylinder liners.

I stand corrected then, and I feel stupid because I looked at that very page and somehow missed the aluminum reference. It also appears that cast aluminum block engines date to WW1 (Hispano-Suiza produced the first one).

Anyhow, that would explain why some inline engines are so vulnerable. Bullets will generally go right through aluminum, although some grades of aluminum make decent armor (the M113 APC had 3/4" of aluminum armor which prevented penetration by most small arms fire).

So, it's not so simple as figuring joules of energy vs. mm of homogenous rolled armor and dividing by some factor to get penetration of cast iron!

[Pursuivant]

More pictures

#1 Bf-109E-4 getting smoked by a Wellington III Ace gunner at medium range (~300 m when hit) from a shot from above. I didn't play it out, but I'd suspect that the engine has 5-10 minutes to live. Also notice two different bursts of MG fire passing extremely close to the plane from other Wellingtons at extreme range (600+ meters). Kind of a poster child for toning down Ace AI gunners, especially since most gunners were trained to hold their fire until the enemy got within 500 m.

http://forum.1cpublishing.eu/attachm...1&d=1401771087

#2 Bf-109E-4 getting smoked by a Wellington III at medium range (300 m) by a shot through the prop. Expected engine life 5-10 min.

http://forum.1cpublishing.eu/attachm...1&d=1401771087

#3 Same as above but notice the remarkably tight grouping of hits on the Bf-109s nose at 450+ meters!

http://forum.1cpublishing.eu/attachm...1&d=1401771087

#4 P-51B flamed by Ace Wellington III gunner at about 200 meters while maneuvering. While the shot doesn't show it effectively, one .30 caliber bullet was sufficient to set the forward fuel tank on fire, and another shot smoked the engine. A better view would have shown the bullet hitting right in the middle of the forward fuel tank. And this wasn't a fire that broke out after fuel hit the engine, the plane was suddenly engulfed in flames.

http://forum.1cpublishing.eu/attachm...1&d=1401771087

[Pursuivant]

A couple more pictures of the P-51B's vulnerabilities.

#1: P-51B after getting zapped by the nose gunner of an Ace AI Wellington III at about 200 m range while closing at about 550 kph, so perhaps about 750-800 kph total closing speed. Normally, I'd call this a fair hit - lots of extra energy, close range and I wasn't maneuvering much - except that you'll notice that none of the bullets' trajectories actually directly penetrates the engine block or the cooling system! (The bullet at the top was also glancing.)

Even with a soft aluminum engine block and lots of extra energy on the bullet, there's a good chance that realistically all of those bullets would have ricocheted rather than penetrating.

And, ONE glancing shot was sufficient to instantly seize up the engine. No warning, just a dead engine. Not realistic behavior even for a mortally wounded engine.


http://forum.1cpublishing.eu/attachm...1&d=1401800105

#2 P-51B after getting hit by the tail gunner of an Ace AI Wellington III at 450 m. This one caused a coolant leak, so perhaps 5-10 minutes of engine life.

In addition to a remarkably tight bullet grouping by the quad machine guns (almost no dispersal at all - the bullet in the wing is from the head on pass I took earlier) at extreme range, you'll also notice that the bullet that inflicted the fatal damage penetrates exactly where the P-51 had 1/4" of armor plate! So, either an AP bullet or the armor plate over the coolant tank isn't properly modeled.

http://forum.1cpublishing.eu/attachm...1&d=1401800123

[DuxCorvan]

@Pursuivant: Those pics show what the problem really is, and is not engine frailty: it's the incredibly unrealistic gunner accuracy in this game, when most RL reports and accounts testify gunners were more a dissuasive resource than a real threat for pursuing fighters, except at close distance and straight flying.

As I've stated many times gunners in this game -both AI and human- have it too easy to aim and shoot. AI because it cheats, humans because a real gun station would never move as fast, accurately and lightly as a mouse pointer.

If real gunners were so effective, then contraptions like the Defiant would have been a resonant success, and not the failure they were.