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I have the book too, but am at work all day so won't be able to cross reference it until tonight. At this point I'm going off the original spec chart especially because the figures listed for speed and all that is lower and probably more realistic.Performance figures I used are from Page 47 of the book listed in a previous post.
Junkers Ju 288/388/488 by Karl-Heinz Regnat. It is Black Cross volume 2.
There are stats for the 288A, the 288B and the 288C.
I used the ones from the column headed 288A and the last stat listed is the crew which says three for that version. the other two models are listed as having the four man crew.
Other sources may well vary.
Why? The speed is lower at that altitude than at 6km when it should be higher due to the less dense air lowering drag. That is entirely in line with the lower capability supercharger, which the chart I posted notes says HP output was lower at the higher altitude. The weight gain would be a factor, but AFAIK the Ju288B did not plan to use the Jumo 222 E/F until very late in the war. Again I'll have to double check the book you mentioned when I get home tonight.I would be very questioning of performance numbers for 8000 meters altitude. The JU 222 A/B engines were single stage, two speed supercharged engines. The 288B (four man crew) is supposed to have been planned for the 222 E/F with a two stage supercharger and that is a lot more believable for top speed or cruising at 8000 meters. In the chart/table on page 47 of that book the 288B is listed as having a lower ceiling than the 288A despite the 2 stage supercharger. Of course picking up almost 4000kg of weight certainly didn't help.
IIRC 2 out of 3 engines tested did. And the 100 hour test is a continuous 100 hours of operating. The B-29 engine did indeed have several issues, but it seems a lot of it was related to the areas where they were operating, since tropical climates were not helping the issue of overheating, which when coupled with the magnesium materials used in it led to fires. That was more similar to the issues of the BMW 139 and Japanese Homare engine given that all of those were air cooled radials than the liquid cooled Jumo 222.I would note (and have noted it before) that just because ONE engine makes it through a type test in a test cell (on the Bench?) doesn't always mean that all production engines are going to last as long. Napier Sabre being a case in point. Not to pick on the British too much the Wright R-3350 used in the B-29 passed it's type test in 1939 and we know how well that worked out. XB-29 No 1 required 17 engines to log 99 1/2 flight hours. Perhaps one engine lasted all 99 1/2 hours and the other 3 needed frequent replacement. I don't know. I do know that there were a number of engines that squeaked through type tests that were nothing but trouble for several years in service.
Sorry but saying that the Jumo 222 passed a type test doesn't prove much of anything one way or the other. The fact that 280 something engines built only got under 9 airframes into the air says a lot more. I have noted it before, The RR Peregrine, with 301 engines built, kept two squadrons of Whirlwinds in Service for over 1 1/2 years.
They were quoting blast radius details from Luftwaffe manuals about the bombs. The details weren't the game's damage model.I am not going to place much credence in a computer game damage model unless somebody can show how it was done. One of these popular computer games uses the same rate of fire and damage model for ALL 20mm guns in the game.
I get your point, but using two radial air cooled engines as an example vs. a liquid cooled engine in a different layout is not the best counter example given how different the engine styles and issues are.The American type test was 150 hours, The R-3350 had to pass it several times, every major change requires a new type test. Or every power rating change requires a new type test.
US test was as follows.
At least 150 hours of running, including
10 hours at take-off power.
40 hours at rated power or 91% of take-off power, which ever is greater.
10 hours at overspeed.
The take off part of the test may be done continuously or up to 120 five minute periods alternated with 120 five minute periods at idle.
Similarly the overspeed test is may be broken into a series of 30 or 60 second periods of overspeed alternated with 5 minute periods at idle.
Passing a type test is also not really related to or an indication of average over-haul life. R-3350s started their service career (not experimental use) at about 100hrs average life.
By the end of WW II they averaging 400 hours, in airline use in the 1950s they were occasionally making it to 3000 hours. These late engines only had to have one example pass a 150 hr type test at the specified rating/s.
Point is that one engine successfully getting through a type test is no guarantee that early production (or even later production) engines will have a successful career.
Bristol Hercules passed a type test, early versions in Wellingtons sometimes didn't make 30 hours, later ones got much better, post war ones were an order of magnitude better.
about you stop commenting until I do so I can debunk your bullshit?
Here's a trick, how about you stop the casual insults mate. We can do this without them, so be civil.Alright, you're obviously trying to derail the thread. Stop being a douche.
I get what you're saying. Going through Ferdinand Brandner's memoir (he was the head engineer of the Jumo 222 project) they started the project in 1937 and had completed the first perfect 100 hour bench test in March 1940. He says it was not ready then, much as you're pointing out about other engines, and required two years to get production ready, with a start date for mass production in July 1942 set.Well, we can look at the Allison engine in 1940. It had passed a type test and yet in US service in 1940 it had to be down rated to a max rpm of 2770rpm instead of 3000rpm while the engines were rotated out of service and sent back to Allison for a rework that involved both a new crankcase and a new crankshaft, to be done at Allison's expense. Something like 288 engines were involved. Later Allison's got a lot better.
The Napier Sabre has already been mentioned several times. The RR Vulture may have been mentioned more than once. The Continental XI-1430 has been mentioned, it passed a type test but engines delivered to Lockheed and McDonald were not only troublesome but didn't come close to making the promised power. All had passed type tests or they wouldn't have been put in aircraft for testing the aircraft. Experimental engines were put in known aircraft to keep the variables down, much like Junkers used a Ju 52 for flight trials of the Jumo 222 engine. Large, multi seat aircraft also offered room for extra instruments and engineers/technicians to monitor engines still in development while in flight.
Passing a type test didn't seem to mean as much as was hoped, engines that failed a type test could be real trouble.
The engines that are used for a type test are usually tool room samples and not built on production machinery or using normal production workers.
The ignition system on the Jumo 222 seems bizarre in the extreme, every other aircraft engine used dual ignition (two spark plugs per cylinder) for two reasons. One was safety in that should one magneto fail all cylinders still had one functioning spark plug. engine performance was reduced due to less than ideal flame front propagation the cylinder, but one could assume that some sort of cruise power (or high cruise power) was still available. Some sources on the Jumo 222 claim that each magneto fired both plugs in 1/2 the engine. If a magneto fails 12 cylinders out of 24 would still function completely as normal while 12 cylinders wouldn't function (fire) at all. Try pulling four of the plug wires on an eight cylinder car and see how it runs. Potential vibration problems are astronomical.
The Jumo 222 A/B-2's cylinder bore was increased .20 in (5 mm) to 5.51 in (140 mm), while its stroke remained unchanged at 5.31 in (135 mm). This change increased the Jumo 222 A/B-2's displacement by 214 cu in (3.50 L) to 3,044 cu in (49.88 L). The H-beam articulated connecting rods of the early engines were replaced with an I-bean articulated connecting rod design. The engine's compression ratio may have been raised to 6.735 to 1, and valve diameters may have been altered slightly. The Jumo 222 A/B-2 had a balance pipe between the intake manifolds of adjacent cylinder banks. Engine speed was limited to 2,900 rpm in an attempt to increase its reliability. The Jumo 222 A/B-2's maximum power at 2,900 rpm was 2,500 hp (1,864 kW) for takeoff and 2,490 hp (1,857 kW) at 16,404 ft (5,000 m). Climbing power at 2,700 rpm was 2,250 hp (1,678 kW) at sea level and 2,050 hp (1,529 kW) at 16,404 ft (5,000 m). Cruising power at 2,500 rpm was 1,900 hp (1,417 kW) at sea level and 1,750 hp (1,305 kW) at 16,404 ft (5,000 m). The engine's fuel consumption at cruise power was .449 lb/hp/hr (273 g/KW/h) at sea level.
Stats:The Jumo 222A/B-1-powered Ju 288 V5 made its maiden flight on 8 October 1941. Brandner had managed to talk his way onto the aircraft for the flight, which was completed without issue. For the Ju 288, the Jumo 222 turned a four-blade Junkers VS 7 propeller that was a 13 ft 1 in (4.0 m) in diameter. An annular radiator was positioned in the cowling, and experiments were conducted on Ju 288 V5 using a ducted spinner to deliver cooling air to the radiator.
The further development mentioned above was the A/B-2 version.The Junkers Jumo 222 A/B-1 had a 5.31 in (135 mm) bore and stroke. The engine had a total displacement of 2,830 cu in (46.38 L). The Jumo 222 A/B-1 initially produced 2,000 hp (1,491 kW) at 3,200 rpm. At the expense of reliability, further development eventually pushed its maximum power at 3,200 rpm to 2,500 hp (1,417 kW) for takeoff and 2,200 hp (1,641 kW) at 16,404 ft (5,000 m). Climbing power at 2,900 rpm was 2,260 hp (1,685 kW) at sea level and 2,090 hp (1,559 kW) at 16,404 ft. Cruising power at 2,700 rpm was 1,900 hp (1,617 kW) at sea level and 1,700 hp (1,268 kW) at 17,060 ft (5,200 m). The engine's fuel consumption at cruise power was .477 lb/hp/hr (290 g/kW/h) at sea level. The Jumo 222 A-1 weighed 2,690 lb (1,220 kg), and the Jumo 222 B-1 weighed 2,745 lb (1,245 kg). The engine had a diameter of 3 ft 10 in (1.16 m) and was 7 ft 5 in (2.25 m) long.
Work on the Jumo 222 would continue, but the engine was no longer a priority. Brandner stated that, at the time, various Jumo 222 engines had completed 20 100-hour test runs, and many at Junkers felt that the engine was basically ready for production. However, further issues with the connecting rod bearings caused a developmental delay that extended from January to March 1942. The connecting rod bearing failures took a long time to resolve with experimentation of different bearing materials and lubrication techniques. Ultimately, a new connecting rod design was employed, the antimony alloy bearing material was replaced with a tin alloy, and the synthetic engine oil used was switched to a natural oil with an increased sulfur content. Due to tin shortages, antimony had been substituted early in the engine's development.
Various versions of the Jumo 222 were flown in approximately 11 aircraft: three Ju 52 test beds, six Ju 288s (V5, V6, V8, V9, V12, and V14), one Fw 191 (V6), and one He 219 (V16). Jumo 222 engines were also planned for the Heinkel He 219B and C and the Hütter Hü 211 heavy fighters. Engines were not ready for the He 219B and C airframes, and the two Hü 211 prototypes were destroyed while under construction during an Allied bombing raid in December 1944. Some sources state that Jumo 222 engines were fitted to a four-engine Heinkel He 177 (V101), as the burned out remains of this aircraft were found at Cheb in Czechoslovakia. However, examination of the aircraft reveals the engine's exhaust stacks were in the standard four and eight o'clock positions for a Daimler-Benz DB 603 engine rather than the 2, 6, and 10 o'clock positions for the Jumo 222. The Jumo 222 was proposed for numerous other aircraft designs ranging from fighters, like the Focke-Wulf Ta 152, to bombers, like the Heinkel He 177. However, none of these plans came to fruition. A total of 289 Jumo 222 engines were built.
While the Jumo 222 was not trouble-free, its development progressed as well as could be hoped for considering it was a new engine design, the repeated changes to engine requirements and design, and that the ongoing war resulted in material shortages. Some contend that the changing Ju 288 and Jumo 222 requirements were intentionally made to cause the aircraft and engine to fail.
Heinrich Koppenberg was the managing director of Junkers, the only German company producing both aircraft and aircraft engines. Koppenberg had become a powerful man who worked himself into various positions that gave him control over many strategic resources. Erhard Milch was the Air Inspector General of the Luftwaffe and in charge of aircraft production. He had gained increasing control over aircraft procurement in Germany. Milch felt that Koppenberg and Junkers would have an aircraft production monopoly and economically ruin other companies if the current Ju 288, Jumo 222, and other company projects were successful. New large-scale Junkers production orders meant that resources at other companies would be allotted to produce Junkers products under license rather than develop their own. Some contend that Milch began to alter the official requirements just as they were about to be met by Junkers. After Ernst Udet, head of the T-Amt (Technisches Amt, Technical Office of the RLM), committed suicide on 17 November 1941, Milch took his place. Milch now had the power to dictate programs for the Luftwaffe. Acting as the RLM's authority, Milch continued to change project requirements, which left Junkers to perpetually chase the goal. Koppenberg was imprisoned in April 1942 when Junkers repeatedly failed to achieve what the RLM asked of them. While the above may be true, it is also true that the Jumo 222 had its own design issues. Brandner felt the engine was "developed to death" with its numerous displacement changes and constant design revisions.
Problem is the point defense system they had and how quickly any fighter could not only rise the to the appropriate altitude (6km probably), but then close the distance and get into attack position. And hope the bomber didn't spot them and dive away. Even then I'm not sure the MiG-3 could catch even the 2000hp version with the lower spec sheet given that it's top speed was only slightly higher than the Ju288, but it wouldn't matter largely because MiG-3 was largely withdrawn from most service by 1943.Well, as far as the Russians intercepting it, you may be right. By 1943 there weren't a whole lot of MIG-3s left in service. Perhaps a bit over 300 defending the Moscow area?
Development was continuing at a slow pace and the Russians could have come up with something (and diverted some production of AM engines from the Il-2) if the Ju 288 was causing a big problem.
I'll stick with the opinion of the head engineer of the project about it being production ready, especially since the version in question was good enough to be fitted to 5 prototypes and worked in that role and the engineer in question felt confident enough about it to ride in the first flight it was fitted to a Ju288 prototype. Also note in the Karl-Heinz Regnat book you cited earlier that the last prototype of the Ju288 fitted with the Jumo 222 worked perfectly. That would be the V14 prototype (288B variant) that entered testing in August 1942. Earlier ones apparently also worked very well as well.I am not sure about translations between "bench tests" and type tests.
For the P & W R-2800 it was first run Sept 13, 1937 (this may have been a 9 cylinder single row test rig).
By Nov 18th 1937 they had 100 hours of running time.
By Aug, 15th 1938 they had 1000 hours of running time.
By July 1st 1939 they completed two type tests, Engine No1 at Wright Field and engine No 2 at the Pratt & Whitney factory. At the completion of the type tests they had 3300 hours of run time on the test/development engines. All was ground running.
July 12, 1939 was the first test flight in the Vultee Y-19.
Feb 12, 1940 say 5000 hours of running time completed.
March 25th 1940 was when the completed the model test of the first contract model.
Granted Production R-2800s were a lot more trouble free than Wright R-3350s.
However problems with high cylinder count engines seem to go up near exponentially.
P & W had 15,000 hours of ground running on the 28 cylinder R-4360 to get to about the same stage of development as the R-2800 had with 3,500 hours. And remember. the R-4360 used R-2800 cylinder barrels, R-2800 cylinder heads (and valve gear) and either R-2800 pistons and rings or darn close to it (connecting rods were probably different).
So in the US you had bench running, bench tests, type tests, model tests, and flight tests. How that translates to German practice I don't know. Or how different letters/memos/documents were translated.
Wright had some of their troubles (but certainly not all) with the R-3360 because of the almost 6.5 million dollars (62.5 million in year 2000 dollars) flushed down toilet on the Tornado project which included 1,632.35 hours of testing on six 42 cylinder engines, 1,200 hours on two 14 cylinder engines and 130 hours on a 6 cylinder test engine. The Tornado project didn't come close to resulting in a useable aircraft engine. This division of effort (and work on the later R-2600 and R-1820 models) certainly did nothing for the R-3350.
If the RLM evaluators decided the JU 288 wasn't going to meet the performance goals with the early Jumo 222 engine then you are back to the choices listed earlier. Accept the lower performance. Delay production and demand new versions of the engine with more power. Scrap the whole program and start over.
Are their any documents that say Milch made the decisions on his own evaluation or was he relying on reports from engineering staff? Granted he could exert pressure on such a staff but few manufactures are going to admit their own estimates are a wrong.
So, to answer the question "how would it perform?" as an individual aircraft it would be formidable assuming the projected performance criteria were met. As a weapons system, I think the results would have been less than hoped for.