FlatSpinMan Posted January 27, 2013 Posted January 27, 2013 Post information about aircraft performance here, or in this forum at least. The goal of such discussion is to try to determine the historical performance of aircraft using data from various sources. The goal is not to win an argument or score points off other members. THE RULES 1. Back up any assertion with evidence. 2. Keep an open mind when reading new information that contradicts your own ideas. Allow that you may in fact be mistaken. 3. Do not quote long passages. Quote only the relevant sentences. 4. Keep discussion civil at all times or be suspended. 5. Do not make sarcastic little comments just to score points. Reminders - This forum has an "ignore" function. If someone's posting style bothers you, add them to your Ignore list, then get on with your life. - If someone has crossed a line, report them to the moderators. Do not fan the flames of the fire. I will be moving content from other threads into this one when I have time. Once that is done I will unlock this thread. Content from "What planes were in this conflict" thread. Posted 14 January 2013 - 23:45 JG52Karaya, on 14 Jan 2013 - 22:20, said: Forget the 670kmh figure, thats an overoptimistic one! I know the report that mentions that particular figure and it also has the Bf109G-1 quoted as achieving 700kmh at 7km which is even more optimistical... I don't defend any specific performance. I just wanted to point out there is a problem with F-4 performance especially from developers point of view because this usualy means two opposite groups in one player community. Basically one claims max speed has to be higher than 635 (up to 670km/h) and one claims it should be 635 at best. OT. The G-1 700km/h is noted as "calculated", not test result. Edited by JG1_Pragr, 14 January 2013 - 23:48. Next post Posted 15 January 2013 - 23:07 JG1_Pragr, on 14 Jan 2013 - 23:45, said: I just wanted to point out there is a problem with F-4 performance especially from developers point of view because this usualy means two opposite groups in one player community. Basically one claims max speed has to be higher than 635 (up to 670km/h) and one claims it should be 635 at best. Honestly I dont see the problem here! 635kmh is as said the topspeed @1.32ata and 2500rpm which corresponds to ~1250PS, there's no denying. That the Bf109F-4 obviously would be faster using 1.42ata and 2700rpm (1350PS) is I think quite logical, by how much exactly is the question. Again I would deem a topspeed of 650kmh reasonable Next post Quote Honestly I dont see the problem here! 635kmh is as said the topspeed @1.32ata and 2500rpm which corresponds to ~1250PS, there's no denying. That the Bf109F-4 obviously would be faster using 1.42ata and 2700rpm (1350PS) is I think quite logical, by how much exactly is the question. Again I would deem a topspeed of 650kmh reasonable 650km/h seems about right but let's face it once we get to actually fly the planes there will be plenty of threads where FM complaining will be in full swing. We will just have to wait and see for now... Edited by 4./JG53_Wotan, 15 January 2013 - 23:13. Next post osted 16 January 2013 - 09:22 Quote According to e.g. Kurfust's site the plane with this engine limitation reached 670km/h at 6.2km. This usually splits any community into two opposite sides: one fully support such high performance of 109F-4 and one claiming the maximum shall be 635klm/h only. It should not split anything. The 635kph is consistant with climb and combat power and the 670 with take off and emergency power, both in the limits of normal variation for aircraft performance. Off course we need to open the compressibility correction can of worms as well. Rechlin offers different numbers than Mtt due to the application of compressibility error. They were not the only ones to apply a compressibility correction but not all the corrections where the same during the early 1940's. Next post Posted 19 January 2013 - 19:02 I/JG3_Pragr, on 14 Jan 2013 - 23:45, said: I don't defend any specific performance. I just wanted to point out there is a problem with F-4 performance especially from developers point of view because this usualy means two opposite groups in one player community. Basically one claims max speed has to be higher than 635 (up to 670km/h) and one claims it should be 635 at best. OT. The G-1 700km/h is noted as "calculated", not test result. Some German speed charts for these planes (F-4,G-2) were not corrected with compresibiliy error. It is known fact. Thats why maximum speed at higher alts are not accurate. The same thing is with some FW 190 charts. So what Karaya said about maximum speed for these planes is accurate: "Forget the 670kmh figure, thats an overoptimistic one! I know the report that mentions that particular figure and it also has the Bf109G-1 quoted as achieving 700kmh at 7km which is even more optimistical. In reality the actual topspeed of the Bf109F-4 @ 1.42ata and 2700rpm was more like 650kmh at ~6km which puts it en par with the G-2 which (depending on source & build quality) is credited with achieving 650-660kmh at 6,7km - VVS even got 666kmh out of it. Most sources will say 7km but thats the calculated FTH for the DB605A-1, actual testings top out at 6,6 or 6,7km almost every time. I say give the Bf109F-4 the full 1.42ata boost, it is after all the way they were operated at the time. For any earlier scenarios we could just get a downrated version of the same plane with little effort (just cap the engine at Steig/Kampfleistung and that's it!)" And about La5 turn rate i have to note that 25 sec is for non sloted version, LA5 with slats got ab. 22 sec turn time at 1000m - still inferior to 109 and more equal to Fw 190 turn times. Edited by Kwiatek, 19 January 2013 - 19:06. Next post Posted 19 January 2013 - 23:15 Quote Some German speed charts for these planes (F-4,G-2) were not corrected with compresibiliy error. It is known fact. The Germans were the first to use compressible aerodynamics. Their lead scientist introduced the concept to the world, in fact. Almost everyone at the time used incompressible flow aerodynamics and just before the war a tabular method of accounting for compressibility in airspeed measurement became popular although it was not in universal use. If you are a member of AIAA, the American Institute of Aeronautics and Astronautics, their library is easily searchable to get the facts. Unfortunately I cannot post the conference lectures and reports detailing Germany's compressible aerodynamics research as we are limited to 5Mb on posting. On second thought and within the posting limits of the board, I can post this chart which clearly shows the difference between earlier compressiblity corrections and the research Germany was involved in: Attached Thumbnails Edited by Crump, 19 January 2013 - 23:30. Next post Posted 23 January 2013 - 00:10 Crump, on 22 Jan 2013 - 23:19, said: And normally aspirated engine. As an export variant, the P-400 was not equipped with a supercharger limiting its performance at high density altitude. What nonsense!!! All Allison engines mounted in airplanes had a supercharger. Edited by MiloMorai, 23 January 2013 - 00:10. Next post - SYN Ricky Posted 23 January 2013 - 00:23 Didn't they have just a 1-stage, 1-speed supercharger, making them perform better at low alt?
FlatSpinMan Posted January 27, 2013 Author Posted January 27, 2013 Next post El Aurens Posted 23 January 2013 - 02:59 Indeed all V 1710 Allison engines had a single speed/single stage supercharger, except those mounted on the P-38 which were turbo-supercharged. The prototype P-39 had the turbo installation as it was originally designed to be a bomber interceptor. The Air Corps changed it's role to what the British call "Army co-operation" and removed the high altitude performance requirement. Next post Ace of Aces Posted 23 January 2013 - 03:10 MiloMorai, on 23 Jan 2013 - 00:10, said: What nonsense!!! All Allison engines mounted in airplanes had a supercharger. Agreed...Apparently Crumpp is confusing a turbo-supercharger with a supercharger..If I recall correctly, at that time the US did not allow the turbo-supercharger to be exported, only plain ol superchargers versions. This restriction also affected the P-38 sales to the UK. Next post NZTyphoon Posted 23 January 2013 - 06:03 Just for interest here is the British opinion on the Airacobra I: (A Most Secret Place: Boscombe Down 1939-45 - Johnson and Heffernan, pages 91-92) Apparently the Soviets removed the 4 .303s in the wings. Next post Next post Crump Quote Apparently Crumpp is confusing a turbo-supercharger with a supercharger.. No just repeating what I have read. It appears that many authors have confused a sea level engine with an altitude engine assuming the sea level engine is not supercharged. The Allison V-1710E4 was a sea level engine. The engine did have a poor single stage supercharger but it is still a sea level engine. Next post MiloMorai Posted 23 January 2013 - 21:33 Quote The Allison V-1710E4 was a sea level engine. The engine did have a poor single stage supercharger but it is still a sea level engine. http://www.wwiiaircr...rcraft-1400.jpg Sea level was 15,000ft. Next post Ace of Aces osted 24 January 2013 - 00:50 Man that is a nice graph!I wish all the graphs had that much info in them!As for the data, 15k is nothing to snark at!Granted it would not have been the plane of choice for high alt escorts..But the performance of that single stage supercharger was good to go at the useful altitudes of ground support of the troops and explains why the Russians loved this plane so much! Edited by ACEOFACES, 24 January 2013 - 00:52. Next post Crump Milo, it does not have anything to do with any overboosted condition. An engine is classified by it's sea level performance at maximum continuous. 14 CFR Part 1 will tell you it is by Take Off rating but that is because there are only two major types of superchargers used today and you can tell by the take off rating application whether you have a sea level supercharger or altitude engine. The premise is the same though today. If you get a V-1710-35 graph, you will see the rated power at maximum continuous falls from sea level. If you compare an altitude engine such as the BMW801, you will see that power increases at maximum continuous from sea level to FTH. The graph you posted is from Bell Laboratories and clearly labeled P-39C and not P-400. Only three P-39C made it into service with the RAF and the P-400/P-39C was withdrawn from service in December 1941. Most of the contracted RAF P-400's were sent to the Soviet Union and many were taken back by the USAAF to be used in the 12th Air Force in the desert. The promises Bell labs made for the P-400 performance were not realized by the customer, the RAF. Hence, the customer withdrew the aircraft from service and cancelled further purchases because the product that could not do what the manufacturer claimed it could!! Edited by Crump, 24 January 2013 - 08:39. Next post MiloMorai [EDITED OUT UNNECCESSARY SWIPE AT ANOTHER MEMBER] Posted 24 January 2013 - 22:58 Quote The graph you posted is from Bell Laboratories and clearly labeled P-39C and not P-400. [EDITED]The Bell Aircraft Corp, founded by Larry Bell did make airplanes tho. Quote The promises Bell labs made for the P-400 performance were not realized by the customer, the RAF. Hence, the customer withdrew the aircraft from service and cancelled further purchases because the product that could not do what the manufacturer claimed it could!! The British purchase of the airplane was based on the claimed performance of the XP-39 that used turbosuperchargers to augment its mechanical supercharger. "Unfortunately, Bell's glossy advertising brochures did not distinguish between the performance of a lightly-loaded, unarmed, highly-polished experimental prototype and a production fighter heavily-loaded with military equipment and armament, and the British were to rue the day that they ever looked at an Airacobra. " Quote Only three P-39C made it into service with the RAF and the P-400/P-39C was withdrawn from service in December 1941. No 601 Squadron relinquished its 13 Airacobras in March of 1942 in favor of Spitfires. Quote If you compare an altitude engine such as the BMW801, you will see that power increases at maximum continuous from sea level to FTH. The FTH of the BMW801D ranged from 1800m @ 2100rpm (1.1ata) to 1300m @ 2300rpm (1.2ata) to 700m @ 2400rpm (1.32ata) to 800m @ 2700rpm (1.42ata). Normal power rating (2600rpm) of the V1710 went from 960bhp SL to 1000bhp at 13,800ft (4200m). Next post Crump Posted 24 January 2013 - 23:37 Quote No 601 Squadron relinquished its 13 Airacobras in March of 1942 in favor of Spitfires. P-400's and NOT P-39C's.... Different supercharger design than the P-39C. Quote The FTH of the blah blah blah An engine is classified by it's sea level performance at maximum continuous. 14 CFR Part 1 will tell you it is by Take Off rating but that is because there are only two major types of superchargers used today and you can tell by the take off rating application whether you have a sea level supercharger or altitude engine. It is really that simple, Milo. Perhaps a trip to your local airfield and a discussion with a knowledgeable A&P will help you see the difference. I am sure most of readers can examine the power charts below and see the trends in altitude performance at a constant manifold pressure and rpm. The Allison drops off with altitude while the BMW increases in power at a constant manifold pressure and rpm up to FTH. That is the basic difference between an altitude engine and a sea level engine. Attached Thumbnails Next post Aces of Aces Posted 25 January 2013 - 02:19 Crump, on 23 Jan 2013 - 09:55, said: The Allison V-1710E4 was a sea level engine. The engine did have a poor single stage supercharger but it is still a sea level engine. That is not true, by definition..Allow me..First the definitions..DEFINITION OF A SEA LEVEL ENGINEQuote A reciprocating aircraft engine having a rated takeoff power that is producible at sea level only. DEFINITION OF AN ALTITUDE ENGINE Quote A reciprocating aircraft engine having a rated takeoff power that is producible from sea level to an established higher altitude as a result of supercharging or turbo charging. Now for an example of a sea level engineHere is a typical sea level engine power graph where X is altitude and Y is power Note the higher the altitude the less power is produced..That is to say at NO altitude above sea level is the power equal to (or greater) than power at sea level..Now with these definitions and examples in place.The only way the power plant in the P-39/P-400 could be called a 'sea level engine' is if the rated power at sea level is ONLY obtainable at sea level.But as we can see from the following P-39 tests, i.e.P-39 performance tests Most of the tests show the rated takeoff power is producible from sea level to an established higher altitude..And therefore the P39/P400 power plant is an altitude engine..BY DEFINITION!In summary, based on the definitions and information provided here.It is wrong to refer to the P39 (or or an equivalent equipped P400) as a 'sea level engine' powered airplane when in fact it meets the definition of an 'altitude engine' powered airplane.. Edited by ACEOFACES, 25 January 2013 - 07:27. Next post NZTyphoon Posted 25 January 2013 - 03:57 Crump, on 24 Jan 2013 - 23:37, said: P-400's and NOT P-39C's.... Different supercharger design than the P-39C. No, it was exactly the same GE supercharger used on the V-1710-35 which was in the P-39C ; V-1710.E.4 was the designation given to the export V-1710-35. These tests show the Full Throttle Height (FTH) of the E.4 to be 10,300 ft, while that of the E.12, with different supercharger gearing, has a FTH of 13,000 ft. (Recommended reading http://www.amazon.co...8/dp/0764305611)
FlatSpinMan Posted January 27, 2013 Author Posted January 27, 2013 Next posts (and these are reeeaaallyy pushing it - I don't care that they are are technically within the rules - the intent is clear) Posted 25 January 2013 - 10:15 Quote BY DEFINITION! B) Posted 25 January 2013 - 10:47 I see your '1' and raise you '8'ONE February 5, 1941 Pursuit One-Engine YP-39, A.C. No. 40-30 Subject: Acceptance Performance Test Section: Flying Branch Serial No: PHQ-M-19-1185-A Engine: Allison V-1710-37 Climb Data ALT BHP ------------ S.L. 1090 5,000 1090 * 10,000 1090 * 13,600 990 * NOTE in the test above the established power at this higher altitude is equal to the rated takeoff power at sea level, and is therefore an 'altitude engine' by definition TWO July 17, 1941 Pursuit Single Engine P-39C, A.C. No. 40-2988 Subject: Flight Tests Section: Flying Branch Serial No: PHQ-M-19-1266-A Engine: Allison V-1710-35 Climb Data ALT BHP ------------ S.L. 1150 5,000 1150 * 10,000 1150 * 13,050 1030 * NOTE in the test above the established power at this higher altitude is equal to the rated takeoff power at sea level, and is therefore an 'altitude engine' by definition THREE December 3, 1941 Pursuit Single Engine P-39D, A.C. No. 41-6722 Subject: Flight Tests Section: Flying Branch Serial No: PHQ-M-19-1325-A Engine: Allison V-1710-35 Climb Data ALT BHP ------------ S.L. 1150 5,000 1150 * 10,000 1150 * 12,400 1150 * 13,650 1080 * NOTE in the test above the established power at this higher altitude is equal to the rated takeoff power at sea level, and is therefore an 'altitude engine' by definition FOUR November 25, 1942 Pursuit Single Engine P-39M-3, A.C. No. 42-4706 Subject: Flight Tests Section: Flight Serial No: FS-M-19-1511-A Engine: Allison V-1710-83 Climb Data ALT BHP ------------ S.L. 1185 5,000 1210 * 9,900 1250 * 15,000 1040 * NOTE in the test above the established power at this higher altitude is GREATER than the rated takeoff power at sea level, and is therefore an 'altitude engine' by definition FIVE October 17, 1942 Pursuit Single Engine P-39N-1, A.C. No. 42-4400 Subject: Flight Tests Section: Flight Serial No: FS-M-19-1487-A Engine: Allison V-1710-83 and 85 Climb Data ALT BHP ------------ S.L. 1170 5,000 1200 * 10,000 1230 * 11,000 1235 * 15,000 1060 * NOTE in the test above the established power at this higher altitude is GREATER than the rated takeoff power at sea level, and is therefore an 'altitude engine' by definition SIX November 24, 1942 Pursuit Single Engine P-39N-1, A.C. No. 42-4400 Subject: Flight Tests Section: Flight Serial No: FS-M-19-1510-A Engine: Allison V-1710-85 Climb Data ALT BHP ------------ S.L. 1355 5,000 1375 * 7,500 1390 * 10,000 1265 * NOTE in the test above the established power at this higher altitude is GREATER than the rated takeoff power at sea level, and is therefore an 'altitude engine' by definition SEVEN 4 August 1943 Pursuit Single Engine P-39Q-5, AAF No. 42-19615 Subject: Flight Tests Section: Flight Serial No: ENG-47-1631-A Engine: Allison V-1710-85 Climb Data ALT BHP ------------ S.L. 1360 5,000 1382 * 7,400 1400 * 10,000 1260 * NOTE in the test above the established power at this higher altitude is GREATER than the rated takeoff power at sea level, and is therefore an 'altitude engine' by definition EIGHT 9 October 1943 Pursuit Single Engine P-39Q-5, AAF No. 42-19615 Subject: Flight Tests Section: Flight Serial No: ENG-47-1651-A Engine: Allison V-1710-85 Climb Data ALT BHP ------------ S.L. 1310 5,000 1330 * 8,100 1350 * 10,000 1255 * NOTE in the test above the established power at this higher altitude is GREATER than the rated takeoff power at sea level, and is therefore an 'altitude engine' by definition PS I would love to hear your explanation..As to why you chose to use data from a test that clearly states WITHOUT RAM in the title of the test Edited by ACEOFACES, 25 January 2013 - 11:25. Posted 25 January 2013 - 11:17 Quote NOTE in the test above the established power Not at a constant manifold pressure and rpm..... Quote PS I would love to hear your explanation as to why you chose to use data from a test that clearly states WITHOUT RAM I would love to hear your explaination on why RAM effects make any difference to whether the aircraft engine is classified as a sea level or altitude engine. #199 ACEOFACES( Posted 25 January 2013 - 11:34 Crump, on 25 Jan 2013 - 11:17, said: Not at a constant manifold pressure and rpm..... Care to post/provide a link to the definition of 'altitude engine'..That states the manifold pressure and rpm must be held constant..Or is it safe to assume this is just another one of your 'personal' definitions you just came up with to support your claims?PS I would also love to hear your explanation..As to why you chose to use data from a test that clearly states V-1710-33 in the title of the test..When you were talking about the V-1710.E.4, which is the export notation for the V-1710-35Reason I ask is that engine is very different from the engines use in the P-39..In that even as early as February 5, 1941 the YP-39 was already using the later E models, aka -37 AllisonWhere...V-1710C,, said: "C" series engines, military model -33, producing between 750 and 1050 hp at 2600 rpm. These engines came in two groups, one group rated at full power at sea level, the other rated at full power at high altitude. As noted, there were two versions..Just out of curiosity, which version is depicted in your -33 graph that you are using as proof.And...V-1710E,, said: "E" series engines, 35, -37, -83, -85 producing 1100 to 2830 hp at 3000 rpm. These engines were a complete redesign, and did not share many components with the earlier engine series. Almost all components were interchangeable with later series engines and the V-3420, and could be assembled as right hand or left hand turning engines in either pusher or tractor applications. Note these engines..The ones I provided data on!States they were a complete redesign and thus had nothing in common with the V-1710-33 data you provided..Which just makes it even stranger as to why you picked -33 data?So would you please explain why/how you think the early 'C' engine test data your provided says anything to the later 'E' model engines used in the P-39sThanks in advance! Edited by ACEOFACES, 25 January 2013 - 12:19. #200 NZTyphoon Posted 25 January 2013 - 13:02 Crump, on 25 Jan 2013 - 11:17, said: Not at a constant manifold pressure and rpm..... Wrong assumption http://www.wwiiaircr.../P-39/AH573.pdf AH573: V-1710 E.4 identical to the V-1710-35: 2,600 rpm constant, 37.2 Hg constant to FTH 10,300 feet AH701: V-1710 E.4 2,950 rpm constant 42" Hg to FTH 13,000 feet http://www.wwiiaircr...-5_42-19615.pdf V-1710-85 3,000 rpm constant, 55 Hg constant Besides, this is not an aircraft performance thread. Edited by NZTyphoon, 25 January 2013 - 18:52. Next post Ace of Aces Posted Yesterday, 00:51 NZTyphoon, on 25 Jan 2013 - 13:02, said: Wrong assumption Indeed..I should point out that the eight tests I posted, were all done at constant RPM, most of the tests didn't document the M.P. but the ones that did showed the MP to be constant..At which point someone may wonder why I didn't post these values?The answer is simple..The RPM and MP values do not factor in and are thus not part of the DEFINITION of an 'altitude engine'.. Only the altitude and power are used in the DEFINITION of an 'altitude engine', so one has to wonder why RPM and MP was even mentioned.. But it is neither here nor there in that as I noted, the RPM and MP was constant.For those that care to go back and verify this by clicking on the link I provided, Don't confuse/use the data collected during the 'Cruising Speed' testing as some here may have done? In that in 'Cruising Speed' testing the engines are not operated at full power levels and therefor the RPM and MP is NOT constant. Edited by ACEOFACES, Yesterday, 00:59.
JtD Posted January 27, 2013 Posted January 27, 2013 For what it's worth, as can be easily seen on the chart Crump posted, the normal rating of the Allison V-1710-33 was 840hp at sea level @~35" boost, 2600 rpm, giving it an output of 960hp at its rated altitude of 12000 feet. Likewise, the military rating of 960hp at sea level @~39" boost, 3000rpm, gave it an output of 1070hp at an altitude of 13200 feet.
MiloMorai Posted January 27, 2013 Posted January 27, 2013 FSM, this thread is going to be a real mess in no time, when there could be dozens of topic subjects being discused.
Crump Posted January 27, 2013 Posted January 27, 2013 http://www.wwiiaircraftperformance.org/P-39/AH573.pdf DEFINITION OF A SEA LEVEL ENGINE A reciprocating aircraft engine having a rated takeoff power that is producible at sea level only. This ends the debate. Thank you NzTyphoon for finding the report on the British P-400's.
GOAT-ACEOFACES Posted January 27, 2013 Posted January 27, 2013 (edited) http://www.wwiiaircraftperformance.org/P-39/AH573.pdf Allison1710E4 ratings.jpg This ends the debate. Thank you NzTyphoon for finding the report on the British P-400's. Ends the debate? Hardly.. As for your current post.. Not sure what you think the power setting time limits for a level-flight and take-off condition, i.e. 1) max time limit of 5 mins for level-flight at 42.5Hg 2) max time limit of 5 mins for take-off at 44.5Hg have to do with a powerplant qualifying as a sea-level engine? Note the definition you quoted for a sea-level engine says NOTHING about the power setting time limits in the definition.. Only power output at altitude is used in the definition of a sea-level and altitude engine. Do you have anything to support your claim that a sea-level engine is defined by the time limits of the power settings? In the mean time, You might want to take a peak at the thread I posted on the sea-level engines vs. altitude engines. I think you find I address a few of your previous misconceptions. sea-level engine vs. altitude engine More importantly.. Would you be so kind as to tell us why you decided to use the power setting time limits data from the AH573 report, instead of the climb test data from the AH573 report that shows the RPM and MP are constant from sea level up to 10,300ft! Not that the RPM and manifold pressure has anything to do with the definition of a sea-level engine! I only bring that up because you were the one trying to imply the RPM and MP did have something to do with the definition of a sea-level engine.. When you said the RPM and MP was NOT constant in the eight P39 test reports I posted. Even though the RPM and MP was constant in those reports. So I find it strange that you NOW decided to ignore the fact that the RPM and MP data is constant in your current post.. Is that the reason you decided to switch? Because these tests do in fact show the RPM and MP are constant, which contradicts your earlier statement that the RPM and MP was NOT constant in these P39 tests? If not, could you please tell us why you switched from using the RPM and MP data to the time limits data. In that I think your answer will be very telling! Thanks in advance! Edited January 28, 2013 by ACEOFACES 1
NZTyphoon Posted January 28, 2013 Posted January 28, 2013 (edited) Allison1710E4 ratings.jpg Quote DEFINITION OF A SEA LEVEL ENGINE A reciprocating aircraft engine having a rated takeoff power that is producible at sea level only. This ends the debate. Thank you NzTyphoon for finding the report on the British P-400's. However, this is Crump's original definition of a "sea level engine", explaining why the website definition he just cited is wrong: Edited by Crump, 24 January 2013 - 08:39. Milo, it does not have anything to do with any overboosted condition. An engine is classified by it's sea level performance at maximum continuous. 14 CFR Part 1 will tell you it is by Take Off rating but that is because there are only two major types of superchargers used today and you can tell by the take off rating application whether you have a sea level supercharger or altitude engine. The premise is the same though today. If you get a V-1710-35 graph, you will see the rated power at maximum continuous falls from sea level. Here is a definition from from WW2: AH573's ratings on the climb at maximum continuous power and constant rpm, to the rated height of 10,300 feet, after which the boost (expressed in American Hg inches rather than the British +--) and power begins to reduce, thus the engine has a rated altitude of 10,300 ft: Looking at another Airacobra I AH701, tested at the same time as AH573, fitted with an Allison V-1710E.12 with a different supercharger gear ratio and tested using a higher continuous rpm and boost - the rated altitude is now 13,000 ft: "If you get a V-1710-35 graph, you will see the rated power at maximum continuous falls from sea level." http://www.wwiiaircraftperformance.org/P-39/P-39C_40-2988.pdf The V-1710-35 power ratings do not fall from sea level - 1,150 hp at 3,000 rpm to 10,000 ft: Edited January 28, 2013 by NZTyphoon
Crump Posted January 28, 2013 Posted January 28, 2013 (edited) lol you so funny it ends nothing!, Sure it does. BHP = PLANK/33,000 P = Brake Mean Effective Pressure L = Length of the Stroke (does not change) A = Area of the Piston Head in square inches (does not change) N = Number of Power Strokes (RPM / 2) K = Number of Cylinders (does not change) Only thing that is variable is the Brake Mean Effective Pressure. Now manifold pressure is NOT BMEP but BMEP is a function of Manifold Pressure. In fact, the only things the pilot can control is the Pressure and RPM. So Explain how any power setting with a lower manifold pressure than the take off rating can produce more power? It cannot unless physics as we know it is altered. So the fact is, the V-1710-E4 is a sea level engine as used in the RAF P-400 series. Unfortunately we have all kinds of things confused in this thread. First of all, the P-39C is not the P-400. The RAF only recieved three P-39C's and the rest were delivered as P-400 export variants with the V-1710E4 engine. We also have a complete side track with some discussion on rated altitude which has nothing to do with the discussion. My airplane is normally aspirated but it has a rated altitude. I can maintain 25 inHG all the way to about 5,000 feet but that has nothing to do with the fact I cannot use my take off rating to climb out except to clear immediate obstacles. Like any sea level engine, I just have to keep moving the throttle up every now and then to maintain manifold pressure because it drops off with altitude. Unlike an altitude engine, it is not equipped with a density controller or pressure valve to maintain a constant pressure. Edited January 28, 2013 by Crump
GOAT-ACEOFACES Posted January 28, 2013 Posted January 28, 2013 (edited) Sure it does. BHP = PLANK/33,000 P = Brake Mean Effective Pressure L = Length of the Stroke (does not change) A = Area of the Piston Head in square inches (does not change) N = Number of Power Strokes (RPM / 2) K = Number of Cylinders (does not change) Only thing that is variable is the Brake Mean Effective Pressure. Now manifold pressure is NOT BMEP but BMEP is a function of Manifold Pressure. In fact, the only things the pilot can control is the Pressure and RPM. So Explain how any power setting with a lower manifold pressure than the take off rating can produce more power? It cannot unless physics as we know it is altered. So the fact is, the V-1710-E4 is a sea level engine as used in the RAF P-400 series. Unfortunately we have all kinds of things confused in this thread. First of all, the P-39C is not the P-400. The RAF only recieved three P-39C's and the rest were delivered as P-400 export variants with the V-1710E4 engine. We also have a complete side track with some discussion on rated altitude which has nothing to do with the discussion. My airplane is normally aspirated but it has a rated altitude. I can maintain 25 inHG all the way to about 5,000 feet but that has nothing to do with the fact I cannot use my take off rating to climb out except to clear immediate obstacles. Like any sea level engine, I just have to keep moving the throttle up every now and then to maintain manifold pressure because it drops off with altitude. Unlike an altitude engine, it is not equipped with a density controller or pressure valve to maintain a constant pressure. Not sure what you think the power setting time limits for a level-flight and take-off condition, i.e. 1) max time limit of 5 mins for level-flight at 42.5Hg 2) max time limit of 5 mins for take-off at 44.5Hg have to do with a powerplant qualifying as a sea-level engine? Note the definition of a sea-level or altitude engine says NOTHING about the power setting time limits in the definition.. Only power output at altitude is used in the definition of a sea-level and altitude engine. Which would have been clear had you read just a little more of the AH573 report, i.e. Note just below the power setting time limitations for level take-off and level flight data you used, there is the results from the climb testing.. Where you can see the manifold pressure is constant at 37.2Hg up to 10,300ft, i.e. ALT RPM Hg. 0 2600 37.2 2000 2600 37.2 4000 2600 37.2 6000 2600 37.2 8000 2600 37.2 10300 2600 37.2 12000 2600 35.2 As you pointed out.. if the MP is constant than the BMEP is constant and thus the BHP is constant! Since the BHP is constant up to 10,300ft Than the BHP is NOT decreasing with altitude up to 10,300ft. Thus the power plant used in this P39 test BY DEFINITION is an 'altitude engine' Hope that helps! S! Edited January 28, 2013 by ACEOFACES
MiloMorai Posted January 28, 2013 Posted January 28, 2013 (edited) An engine is classified by it's sea level performance at maximum continuous. So what is the max continuous of the V1710E4 engine? Certainly not 'take off' when it is limited to 5 minutes. Max continuous power When referred to in context with aero-engines, it means the highest power output or thrust at which the engine can be operated continuously without any time limit.Read more: http://www.answers.com/topic/maximum-continuous-maximum-continuous-power#ixzz2JEMTWL5R Edited January 28, 2013 by MiloMorai
Crump Posted January 28, 2013 Posted January 28, 2013 An engine is classified by it's sea level performance at maximum continuous. That is the quickest way to tell if you are flying an altitude engine or a sea level engine Milo. An engine is classified by it's sea level performance at maximum continuous. 14 CFR Part 1 will tell you it is by Take Off rating but that is because there are only two major types of superchargers used today and you can tell by the take off rating application whether you have a sea level supercharger or altitude engine. Like any sea level engine, I just have to keep moving the throttle up every now and then to maintain manifold pressure because it drops off with altitude. If you set the engine to maximum continuous and you have to keep moving the throttle forward to maintain manifold pressure as you climb, it is a sea level engine. That simple. The modern definition puts it in terms of take off power because it is the same thing. Power drops away with altitude and the engine develops maximum power at sea level. The two classifications of superchargers are the same today as they were back then, btw. Not sure what you think the power setting time limits for a level-flight and take-off condition, i.e. Just the definition of sea level engine. It has been a very revealing discussion and I wish you guys luck.
MiloMorai Posted January 28, 2013 Posted January 28, 2013 So, what is the max contiuous for the V-1710E4 engine?
GOAT-ACEOFACES Posted January 28, 2013 Posted January 28, 2013 That is the quickest way to tell if you are flying an altitude engine or a sea level engine Milo. An engine is classified by it's sea level performance at maximum continuous. 14 CFR Part 1 will tell you it is by Take Off rating but that is because there are only two major types of superchargers used today and you can tell by the take off rating application whether you have a sea level supercharger or altitude engine. If you set the engine to maximum continuous and you have to keep moving the throttle forward to maintain manifold pressure as you climb, it is a sea level engine. That simple. The modern definition puts it in terms of take off power because it is the same thing. Power drops away with altitude and the engine develops maximum power at sea level. The two classifications of superchargers are the same today as they were back then, btw. Just the definition of sea level engine. It has been a very revealing discussion and I wish you guys luck. I noticed you didn't provide any links to anything supporting your definitions of a sea-level engine.. Does that mean it is safe to assume that these definitions are your personal definitions and nothing more?
NZTyphoon Posted January 28, 2013 Posted January 28, 2013 (edited) The modern definition puts it in terms of take off power because it is the same thing. Power drops away with altitude and the engine develops maximum power at sea level. Just the definition of sea level engine. In other words an engine developing 1,150 hp all the way from S.L up to 13,000 ft is not, by definition, a "Sea Level" engine - it is just as the British defined it during WW 2. Edited January 28, 2013 by NZTyphoon
FlatSpinMan Posted January 28, 2013 Author Posted January 28, 2013 Guys. Stop this crap. In my eyes it amounts to harassing another member and I don't see why. In there's so much quibbling over minutiae and all seemingly to prove that one guy may have been wrong or made a mistake. The tone of the posts is unpleasant and not at all necessary. You can expect some action on this as I have gas to intervene several times. As for the comment about this thread getting messed up, I agree. Of course people can make threads for specific aircraft and weapons. But don't do it like this. Locked again for reasons that should be perfectly clear. Any other threads that go like this will be locked immediately. We're not having this behaviour here.
Bearcat Posted January 28, 2013 Posted January 28, 2013 I have no idea what went on in this thread because it has been so heavily edited .. but my take on it gained from seeing how these things go in the past on other boards is.. If you are going to post on a subject with information you better make sure that that information is correct because you can bet your bottom dollar that someone will come up with either the right answer or a different one.. and some people come to these kinds of fights with the right weapons and some do not You can very often find a chart, a report or a pilot account to "prove" contradictory points in most of these arguments. I take most of them with a grain of salt although like Montgomery Scott stated so eloquently.. you can't change the laws of physics. It doesn't matter what the "real life" stats are for the most part.. and it is all moot until the sim comes out and we see what we will have to deal with. Much of this thread is just a bunch of chest thumping bombast as it relates to BoS for that very reason. All of those facts make me feel that if you are going to have these discussions then you need to keep it as civil as possible and if you are going to stick your neck out there then don't get your shorts in a knot if someone chops it off with different "facts" ... because in the end it is all relative. Two guys can test the same car/aircraft and get different results so take all that into consideration in these threads. 1
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