P-38 flight file follies - opinions and input sought
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Thread: P-38 flight file follies - opinions and input sought

  1. #1

    Icon9 P-38 flight file follies - opinions and input sought

    Guys, I am in the process of rebuilding / updating the historical 82nd Fighter Group campaign and completing the part 2 when the unit became part of the 15th Air Force. I have David Copley's permission to work with his P38 family and modify them for the campaigns.

    Mav has already helped me with one problem where AI were not appearing on the runway. (Thanks buddy)

    I am running into performance issues related to flying them in the campaigns. As the 82nd only flew P-38's, getting them to perform right is critical or it will become frustrating to fly the campaigns.

    I thought getting some input from the gurus here might be helpful. Here are the issues and what I have tried so far to affect a fix.

    Range:

    The P-38s had a range of 900 to 1,100 miles. CFS2 models - DCC and the stocker can only make 450 miles. Critical issue for the campaign. Evidently the CFS2 fuel rate consumption calculation is about double what it should be. Things I have tried (working with the P-38G air files):

    Changing the "Best Power Fuel Consumption" scalar in the aircraft.cfg file. I haven't found an equivalent value in the air file using Airwrench or AirEd. No results at all obtained from altering the .cfg file.

    Adjusting the mixture and RPM produces minimal results, maybe 50 miles or so. Not useful.

    Reducing the parasitic drag and the induced drag values in the air file, and the scalar values in the aircraft.cfg file, individually and in combinations with both. I can produce the range with about a 50% reduction in drag. However this also increases the aircraft top speed to 450 / 460 miles per hour. So this doesn't work either.

    The only solution I have found workable for the campaigns is to double the fuel gallons per tank and decrease the empty weight of the aircraft by the weight of the additional fuel. This keeps the aircraft performance the same and doubles the range to 900 miles. It's not historically accurate for the aircraft fuel load but I've run out of other options so I hope it's OK with everyone.

    I would like to have any other ideas or options to try. Any input guys?

    Aircraft performance:

    The P-38 was supposed to have great acceleration capability and climb performance recovery from slower speeds. The model has neither. it loses speed rapidly in turns and is slow to regain the speed lost when leveling out. In a dogfight, this is a problem.

    The engine power is correct so I think the problem is the thrust generated by the props. It's much too low. I've adjusted the prop MOI several times as well as the prop effectiveness value and have gained some performance but not nearly enough. The AI don't have the same problem, just the player aircraft. The only solution I have found is to increase the thrust scalar in the aircraft.cfg file to 1.2 (20% increase). The downside is once again an increase in the aircraft top speed. I can adjust this with an increase in the drag values. This decreases the range, but the additional fuel load / lighter empty weight compensates for that. However, this decreases the AI top speed. In either case the player will run away from the AI at full throttle in formation.

    Another factor is the abysmal throttle response. The RPM increase creeps up rather than a fast response as would be true in the real world (As a pilot, I know this to be true). More on that below.

    Again, I'm hoping someone has a better idea.

    Take off performance:

    Due to the slow throttle response it takes a fair amount of time for the second engine to match the power output of the first engine on start up - about 35 seconds for 10% power. The P-38 had no P-factor (prop torque pull effect) on the take off roll. But if the two engines RPM is not matched you really fight to keep it straight down the runway as the left engine is pulling more power.

    Further, when simply adding full power from the 10% throttle setting (once engine RPM is matched) to take off means the RPM spool up is so slow that the wing men overrun the player's aircraft. The only method to counteract that I have found is up to the player's take off procedure discipline, which is to apply brakes and run up to 40% power - taking another 45 seconds - before releasing the brakes and adding full throttle.

    I have tried adjusting the engine throttle effectivity table in AirEd but it does not seem to change the RPM spool up rate much. It just decreases the RPM separation between 50% to 100% to a small amount. I have only been able to achieve a 5 second reduction in running up to 40% power while still maintaining a decent RPM separation between throttle settings.

    Anyone have a way to increase the throttle response to a realistic level?

    Well that's it. The P-38 air files become a kluge of workarounds to get something that works in a campaign, especially where there are any long distances involved.

    I'd appreciate any ideas that might improve any of these issues.
    Cheers,

    Captain Kurt
    ------------------------------------------------------
    "Fly, you fools!" Gandalf the Gray

  2. #2
    Redding Army Airfield Allen's Avatar
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    2 engines or more and you hit the warp fuel bug. No known fix but for using unlimited fuel. Also note at a long distance no matter how much fuel you add to the .air file CFS2 and warp will eat it. Found this out when testing a Lancaster
    "Let Being Helpful Be More Important Than Being Right!" Some SOH Founder.

  3. #3

    Question Reply...

    Kurt,

    Do you have Pen32Win's P-38 airfile and .cfg modifications?

    IIRC, in the 20th Fighter Group using the P-38H for the first several missions, there is an escort mission from Kings Cliffe to Bordeaux, France. You can make it there and back with drop tanks.
    Attached Files Attached Files
    "Rami"

    "Me? I'm just a Sea of Tranquility in an Ocean of Storms, babe."

    My campaign site: http://www.box.net/shared/0k1e1rz29h
    My missions site: http://www.box.net/shared/ueh4kazk3v
    My scenery site: http://www.box.net/shared/knb1l0ztobhs2esb14rb

  4. #4
    Captain: I've had some success with the Catalina, flying from Henderson to Rabaul and back by leaning out my mixture and reducing prop pitch after takeoff before warping. Have you tried that?
    "De Oppresso Liber"

  5. #5
    Hi guys

    Warp doesnít decrease the fuel consumption of the P38 for whatever reason. Adding additional fuel adds range no problem. Maybe a difference because itís classification is fighter and not most other multi engine aircraft?

    I have the planes equipped with 165 gallon drop tanks which work fine. The campaign issue occurs when they have to be dropped for a fight and the player still has over 450 miles to go to get home. Without the tanks though there couldnít even be a campaign. They are required for 95% of the missions. These guys flew long range missions most of the time.

    Using the Lindbergh leaning method does add some range but only about 50 miles. It should add a lot more but thereís CFS2 for you.

    what is really needed is some way for the fuel consumption value / calculation to be halved and I donít know how todo that. 🤔
    Cheers,

    Captain Kurt
    ------------------------------------------------------
    "Fly, you fools!" Gandalf the Gray

  6. #6
    Quote Originally Posted by Captain Kurt View Post
    The only solution I have found workable for the campaigns is to double the fuel gallons per tank and decrease the empty weight of the aircraft by the weight of the additional fuel. This keeps the aircraft performance the same and doubles the range to 900 miles. It's not historically accurate for the aircraft fuel load but I've run out of other options so I hope it's OK with everyone.
    The aircraft performance will be accurate with full fuel load, but this accuracy will be lost as the fuel amount decrease and the flight model will be totally unrealistic with near empty fuel tanks. The aircraft will then be much lighter than what it should be.

  7. #7
    Kurt


    Would " Aircraft Airfile manager V1.0" be any good???

    For changing some of fuel capacity or weight???

    Also have DP-AFE airfile editor by Masakazu Irie..... if it's any good???

    M

  8. #8
    Hi guys, thanks for the responses.

    Roxanne you are correct of course - one more issue. However I am trying to fit the overall performance into a set of conditions in a specific campaign. The extra fuel comes into play once drop tanks are released in order to fight. At that point = 100% fuel. Once the fight is concluded, the pilot will have to get back to base without running out of fuel. Typically the only point at which the plane would have low fuel would be at arrival at base and for landing. I'll test out low fuel handling for landing maneuvering and see how it affects to performance.

    Mav, thank you. I have Aircraft Airfile Manager, but I would like to check out DP-AFE and see if it would be a better solution than AirEd and AirWrench is working for me.
    Cheers,

    Captain Kurt
    ------------------------------------------------------
    "Fly, you fools!" Gandalf the Gray

  9. #9
    Hi Kurt

    See if any good???

    Mav
    Attached Files Attached Files

  10. #10

    words from an enthusiastic amateur..

    CK,

    I would seek out a copy of Aircraft Airfile Manager v2.2. It's optimised for FSX, but it's full of useful notes about the various entries in the airfile, & you can even, should you wish, alter values on those airfile curves.

    First a caveat. I don't use Airwrench, but base most of my tweaking on Aired & AAMv22. I've often found when converting LR aircraft that a lot of FS9 airfile values simply give you more problems than they solve. Most of what I've learnt is from observation of impacts after adjusting entries in the airfile.

    Stray entries in the aircraft.cfg can also cause issues, especially with AI planes, so I like to start with a stripped down, works for CFS2 aircraft.cfg, with all the flight tuning entries set to 1.00. I then work as much as possible with the airfile, because that affects the AI flight behaviour as well as the player aircraft.

    I find that some airfile entries are best left at cfs 2 nominal values (record 1204 wing incidence = the AI like it best if it's between 0 & 1 deg), (record 1101, lift entries left at the values used by the stockers).

    Particular to the range issue, I've discovered record 508 & 509 can be tweaked to increase range. Lower record 508 & you reduce your fuel burn. The trade off is your speed reduces, so you need better prop tables, or lower drag entries.
    The slope of record 509 & it's final value alters your speed, & also influences fuel burn.

    I would also look at record 1101 angle at zero lift, as that can impact on induced drag (also the value entered in record 1204 for induced drag). If these are out of whack, you compensate with better prop tables, but then fuel burn increases. They're all interlinked.

    Lot's of amend/fly/review cycles, but if I then have the speed, (plus ceiling) & range about right, only then do I look at handling. There are lots of ways to adjust flight handling within the airfile.

    Some value elements of record 1101 can be adjusted, you can adjust record 320 control surfaces, the 1500+ record series can help model handling quirks, & don't forget those values in record 1500. They seem to relate to "agility". Another way of improving AI behaviour, used by Tango Romeo & Talon, was to modify the MOI numbers in the airfile, making them more responsive. So, there are different ways to recover combat handling, but only after you've got the major numbers where you want them.

    I hope this helps.

  11. #11
    Hi Guys,

    Mav - Thanks for letting me try DP-AFE. Basically it identifies the hex locations for each air file entry, and you can cut and paste other air file entries but not much else - at least that I could figure out. I think it would be helpful if you were hex-editing a file to quickly identify and find specific sections and code lines.

    UncleTgt - Very comprehensive. I'll have to experiment with some of that.

    I make almost all adjustments to the air file. I don't like to mess with the .cfg file much because most, though not all, of the effect is on the players aircraft making it a different airplane from the AI. I try to make sure the .cfg and .air file values are matched. It's not universal though, I think there is some cases where the .air file supersedes the .cfg file. A case in point is that changing the fuel quantity in the .cfg file has no effect on the players aircraft. Whatever is in the .air file is what the players aircraft will have. I have to assume that the opposite can be true too, where some value in the .cfg file would supersede the .air file for the AI behavior. But there are two places I will adjust the .cfg.

    One is the empty weight CG position to correct the player aircraft balance / trim in the case where a plane is nose or tail heavy. Incidentally I have also noted this is a case where a .cfg entry affects the AI landing behavior. If a plane is too nose heavy, the AI will land nose down instead of rounding out. Fix the balance in the .cfg file and the AI will level out to land. The other is for prop and or power scalar just enough enough to take off without being run over by wing men. This is a bit of a cheat but so many other factors would be involved to correct the issue that I don't find fighting it to be worth the many hours of testing changes.

    Sections 507 Engine torque vs fuel air mixture and 508 Engine torque vs RPM reductions reducing speed and fuel burn make sense to me. If I understand the effect correctly, essentially what that means is you are reducing the effective engine BHP? In simple terms lower power = lower fuel consumption. If correcting the speed loss through lower drag values, then that would also increase the range possible because of less skin friction, would it not? Much the same effect as reduced fuel consumption. Have you found this decreases climb rate and creates speed loss in maneuvering, or not?

    I'm going to experiment with record 1204 and reduce the drag to see what results I can get. I am already working with the 1101 record Drag Coefficient - Zero Lift value and the Skin Friction Coefficient value which both increase speed and increases range. Keeping the speed correct limits much of the range increases though. As you say, virtually every value is linked to affecting some other value and/or aircraft performance.

    I have some follow up questions for you, if I may?

    When you say angle at zero lift in 1101, which sub record specifically are you referring to? Primary Aerodynamics doesn't have a record named like the description.

    I am now wondering if the 1204 incidence and 1101 set of Lift values are linked to whether an AI add on plane will land or not. Worth an experiment to see anyway.

    The 1500 record is listed as an unknown. What effect does decreasing the two sub records value have on maneuverability and vice versa, increasing the value? What do you define agility as? i.e is it control response speed, or faster roll rates, climb, etc.? Is one of the sub values more effective than the other?

    As a follow up to where I am at so far with the P-38s:

    I have been able to increase the ranges with the correct fuel loads some but not enough. However by adding 100 extra gallons = to 600 lbs I can get around 580 to 600 miles range. Still well shy of the real world aircraft of 800 to 1000 miles but is enough for the campaign to work. The 600 lbs is negligible on the planes flight performance. That means I needn't decrease the aircraft empty weight. The original estimate estimate required 1,800 extra pounds of fuel which would have required an empty weight reduction for the plane to fly well with full tanks. That weight reduction does affect the performance as the fuel falls below 40% in testing. (Thanks Roxanne for bringing that up)

    I have been able to decrease the throttle response time by approximately 50%. Still not real world but is much better and a useful improvement.

    I've not been able to increase the prop thrust to a useful degree and am still stuck with increasing the thrust scalar in the .cfg file coupled with the take off procedure to get off the runway without the wing men overrunning the player. This seems to be necessary only when carrying the heavy drop tanks but 95% of the campaign missions require the external fuel tanks. The missions the 82nd flew were almost exclusively LR and VLR.

    Are we having fun yet?
    Cheers,

    Captain Kurt
    ------------------------------------------------------
    "Fly, you fools!" Gandalf the Gray

  12. #12
    Kurt,

    My descriptions may be a bit vague, posting away from home at the moment.

    Record 1101: Something like Fuselage angle at min drag may be a better description

    I've seen comments that altering record 507 doesn't have any impact, & this may be especially true given most people use auto fuel management - it's a combat sim after all

    re. record 1500 - I've noticed a difference in handling if these values are changed, but as most of my tweaking has been with heavy LR freighters recently, I couldn't be prescriptive on the impact. The listing against these values in AAM2.2 definately suggests lower values mean more agile (Spitfire, Fw190).

    My reference to agility is subjective. It's a feeling, & is mainly informed by watching the AI responses in dogfights. It "might" mean record 1500 is a numerical value for control response lag perhaps?

  13. #13
    Another thought - what's the stock airfile for the P38F like for range? IIRC this aircraft was a player aircraft in the OOB sim wasn't it?

    If i'm correct, then the airfile of the stock P38 might be a better starting point than the FS9 conversions (in terms of AI behaviour).

    Or, maybe the Jap stock A6M's have better prop tables for long range/fuel burn?

    Just some random thoughts ...

  14. #14
    Hi UncleTgt

    I thought I'd test out your thought about the stock P-38F and the Zero.

    The stock P-38 has a range of only 330 miles and a top speed 15 mph too slow, so nothing to gain there. Adjusting the speed through a decrease in drag gained 63 miles in range which is right about where I started out with the air file I am using.

    I replaced the P-38 prop with the Zero prop values and only gained 11 miles in range. It also increased the mph speed but only by 4 mph.

    It was a possibility but only a small gain there unfortunately.

    Thanks for the ideas, it's interesting to explore them.
    Cheers,

    Captain Kurt
    ------------------------------------------------------
    "Fly, you fools!" Gandalf the Gray

  15. #15
    to get off the runway without the wing men over-running the player.
    Your using the same aircraft for both , but the Ai carry no ammo weight , and no fuel weight ,
    If you use a separate Ai and it,s own cfg record , you could add the missing weight as pilot 2 load ,
    as long as you maintain the same center of gravity ,

    Just an observation , the sim loads in air free flight , and the player aircraft always,s set,s to 90 % throttle open ,
    never max ?? The question I pose then is the Ai not governed by the same method ?
    The player can go to 100 % and may explain it,s inheritant abilily to slowly pull away from the Ai wing men ,
    that,s just my 2 bit,s -- Sarg

  16. #16
    Hi Sarg

    I've got the planes to where they can stay ahead of the wing men on take off if the player runs the engines up to 40 to 60% before applying full power. I have the throttle response adjusted to where the power spools up reasonably quick now.The issue is the weight of the drop tanks - I think like you say the AI does not add the weight. It doesn't happen when the aircraft is clean.

    I've not experienced the plane dropping out of warp at 90% throttle. At least in campaigns. It can be 100% or whatever throttle setting was when you warp. Does that happen to you in campaigns?
    Cheers,

    Captain Kurt
    ------------------------------------------------------
    "Fly, you fools!" Gandalf the Gray

  17. #17
    Nope not in campaigns , player aircraft throttle maintains position of before warp, ,

    Are you running auto fuel management ? or selective tank controls ,

  18. #18
    I've been following this thread since it started and decided to lookup the specs for the P-38.

    The P-38 had 410 gallons of fuel without drop tanks and a range of 450 miles, not 900 miles.The fuel was carried in tanks in the wings with 3 tanks in each wing.1 tank in each wing carried 90 gallons,60 gallons and 55 gallons.On all models the wing tanks carried the same amount.

    Some of the drop tanks were 250 gallons and 300 gallons.

    TheBookie

  19. #19
    Redding Army Airfield Allen's Avatar
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    Range numbers are a mess. It depends on straight range or combat radius. Also power setting and altitude and anything on the plane to make drag have effect. This takes me back and this is why I gave up caring about fuel load and burn.

    This manual for the H,J,L list fuel at 306 gal or 416 gal clean.
    https://archive.org/details/PilotTra...e/n43/mode/2up
    https://www.scribd.com/document/2775...-Flight-Manual

    Manual for the H,J has more useful charts and list 416 gal clean.
    http://www.avia-it.com/act/profili_d.../P-38H_J_L.pdf

    P-38J Tactical Planning Characteristics & Performance Chart
    http://www.wwiiaircraftperformance.o...ical-chart.jpg

    Using "Manual for the H,J" and "P-38J Tactical Planning Characteristics & Performance Chart" Range with 900 gal of fuel should be 1,000 miles tell out of fuel at 10,000 feet with power settings 2600 RPM and 44 inHg. This should get each engine at 1,100 HP and burning 113 gal per hour. US manual lack any speed that you should be flying at.

    If I'm remembering right Range divided by Endurance for the average speed. So in this case 1000/3.8=263 MPH as the average speed.
    "Let Being Helpful Be More Important Than Being Right!" Some SOH Founder.

  20. #20
    Quote Originally Posted by Captain Kurt View Post
    Guys, I am in the process of rebuilding / updating the historical 82nd Fighter Group campaign and completing the part 2 when the unit became part of the 15th Air Force. I have David Copley's permission to work with his P38 family and modify them for the campaigns.

    Mav has already helped me with one problem where AI were not appearing on the runway. (Thanks buddy)

    I am running into performance issues related to flying them in the campaigns. As the 82nd only flew P-38's, getting them to perform right is critical or it will become frustrating to fly the campaigns.

    I thought getting some input from the gurus here might be helpful. Here are the issues and what I have tried so far to affect a fix.

    Range:

    The P-38s had a range of 900 to 1,100 miles. CFS2 models - DCC and the stocker can only make 450 miles. Critical issue for the campaign. Evidently the CFS2 fuel rate consumption calculation is about double what it should be. Things I have tried (working with the P-38G air files):

    Changing the "Best Power Fuel Consumption" scalar in the aircraft.cfg file. I haven't found an equivalent value in the air file using Airwrench or AirEd. No results at all obtained from altering the .cfg file.

    Adjusting the mixture and RPM produces minimal results, maybe 50 miles or so. Not useful.

    Reducing the parasitic drag and the induced drag values in the air file, and the scalar values in the aircraft.cfg file, individually and in combinations with both. I can produce the range with about a 50% reduction in drag. However this also increases the aircraft top speed to 450 / 460 miles per hour. So this doesn't work either.

    The only solution I have found workable for the campaigns is to double the fuel gallons per tank and decrease the empty weight of the aircraft by the weight of the additional fuel. This keeps the aircraft performance the same and doubles the range to 900 miles. It's not historically accurate for the aircraft fuel load but I've run out of other options so I hope it's OK with everyone.

    I would like to have any other ideas or options to try. Any input guys?

    Aircraft performance:

    The P-38 was supposed to have great acceleration capability and climb performance recovery from slower speeds. The model has neither. it loses speed rapidly in turns and is slow to regain the speed lost when leveling out. In a dogfight, this is a problem.

    The engine power is correct so I think the problem is the thrust generated by the props. It's much too low. I've adjusted the prop MOI several times as well as the prop effectiveness value and have gained some performance but not nearly enough. The AI don't have the same problem, just the player aircraft. The only solution I have found is to increase the thrust scalar in the aircraft.cfg file to 1.2 (20% increase). The downside is once again an increase in the aircraft top speed. I can adjust this with an increase in the drag values. This decreases the range, but the additional fuel load / lighter empty weight compensates for that. However, this decreases the AI top speed. In either case the player will run away from the AI at full throttle in formation.

    Another factor is the abysmal throttle response. The RPM increase creeps up rather than a fast response as would be true in the real world (As a pilot, I know this to be true). More on that below.

    Again, I'm hoping someone has a better idea.

    Take off performance:

    Due to the slow throttle response it takes a fair amount of time for the second engine to match the power output of the first engine on start up - about 35 seconds for 10% power. The P-38 had no P-factor (prop torque pull effect) on the take off roll. But if the two engines RPM is not matched you really fight to keep it straight down the runway as the left engine is pulling more power.

    Further, when simply adding full power from the 10% throttle setting (once engine RPM is matched) to take off means the RPM spool up is so slow that the wing men overrun the player's aircraft. The only method to counteract that I have found is up to the player's take off procedure discipline, which is to apply brakes and run up to 40% power - taking another 45 seconds - before releasing the brakes and adding full throttle.

    I have tried adjusting the engine throttle effectivity table in AirEd but it does not seem to change the RPM spool up rate much. It just decreases the RPM separation between 50% to 100% to a small amount. I have only been able to achieve a 5 second reduction in running up to 40% power while still maintaining a decent RPM separation between throttle settings.

    Anyone have a way to increase the throttle response to a realistic level?

    Well that's it. The P-38 air files become a kluge of workarounds to get something that works in a campaign, especially where there are any long distances involved.

    I'd appreciate any ideas that might improve any of these issues.
    You need to rework the airfile, not the air.cfg. The air.cfg engine parameters are limited. Remember the Lindeberg trick: use full propeller with poor mixture. It's the historical solution. We, at CFS2, forget to use the throttle gauge when flying. By the way, warps are done using full fuel!

    Cheers

    Pepe

  21. #21
    Good discussions guys.

    The P-38F and P38G had 300 gallons usable (total 306 gallons) in wing tanks while the P-38J and P-38L models had 410 gallons as the Bookie is describing. Drop tanks normally available to commanders in the field were 165 gallons (most commonly used) and 300 gallons (for VLR and ferry flights) not commonly used.

    Range is often used interchangeably to describe combat range, i.e. a radius out and back, or total distance possible in a straight line. Not the same things at all obviously, and unfortunately because different sources use the term without defining which of the two meanings they were using, it causes great confusion.

    Range numbers quoted on internet sources vary so using official AAF books is helpful, but not the absolute reality. Lockheed and their test pilots argued with the Air Force that their operating instructions were too conservative to get the best performance from the P-38 and Lindbergh proved he could double the endurance and range of the airplane over what the official operating instruction provided.

    And that in reality is totally variable depending on altitude flown, speed flown, winds aloft, throttle settings, prop settings, mixture lean setting, aircraft loaded weight, fuel grade, condition of the airframe itself i.e. clean or how dirty, even whether the airframe was painted or left in aluminum.

    However, CFS2 is a relatively simplified world and therefore we use a absolute numbers to model flight with.

    So let's look at the official Operating Manual and the P-38 Tactical Chart. BTW that Tactical Chart is a late war official document as it incorporates operational lessons learned over the previous 2 years regarding RPM and mixture settings.

    The Tactical chart shows the P-38 F&G (i.e. the 300 gal numbers) had a "Maximum Cruise" at 25,000 feet range/endurance of 600 miles and 2.2 hours. The Pilot's Operating Manual says maximum cruise with autolean mixture is 63 gals per hour per engine = 126 gals per hour. Maximum cruise was between 250 and 300 mph. So do the numbers correlate. 300 gallons/126 gph = 2.38 hours. If we use 275 miles per hour as an average we get 2.38 hours X 275 mph and we get 654 miles. That is close when none of the other variables above are not in the mix.

    The Tactical Chart also says the P-38F P-38G had a "Long Range" at 10,000 feet range/endurance of 800 miles and 4.5 hours. The Pilot's Manual shows autolean could be adjusted down to a minimum of 31 gals per hour per engine = 62 gals per hour when setting the engines at 1600 RPM and 27 manifold pressure. So 300 gallons/62 gph = 4.83 hours. Again close. What speeds then are we talking about if we are getting to 800 miles? at 4.5 hours it is 177 mph and at 4.83 hours it is 165 mph. These figures match what Lindbergh was teaching to the P-38 Groups in the Pacific which eventually got back to officialdom and incorporated in the P-38 manuals and performance tables.

    The P-38 J and P-38L numbers (i.e. the 424 gal numbers) check out in the same way.

    So my clean configuration targets are between 600 to 800 miles distance for the P-38F and P-38G, and 840 to 1175 miles distance for the P-38J and P-38L at 10,000 feet.

    For me, CFS2 air files are difficult to model because the game algorithms don't seem to accurately calculate the flight file values. Especially the fuel burn per hour calculations. That value in the flight files is nowhere near the rate used in the game, no matter what throttle, mixture and manifold pressures are used. Invariably a change to one value in the air file makes unwanted corresponding changes to other performance numbers. Or perhaps it's just me and my limited understanding of various aerodynamic values. Carefully inputting all of the real world values that can be identified from all available sources into the air file produces a plane's performance in the game that does not come close to the real aircraft's reported performance. Usually much too low. Very frustrating. I am left with jiggering values until I get the performance in the game that the real plane was supposed to have.

    But so far, I have the P-38F and P-38G reaching 703 miles at 10,000 feet and keeping the reported top speed at 20,000 feet and at sea level. The P-38J and P-38L are being difficult. They are reaching 833 miles at 10,000 feet and keeping the reported top speed at 25,000 feet. However the sea level speed is about 20 mph too high. I'm still working on it but I am about ready to sacrifice the sea level speed and call it good enough for government work so I can move on with building the campaign. I still have about 20 missions to go to complete it.

    Thanks for everyone's input.
    Cheers,

    Captain Kurt
    ------------------------------------------------------
    "Fly, you fools!" Gandalf the Gray

  22. #22
    Quote Originally Posted by Captain Kurt View Post
    Hi UncleTgt

    I thought I'd test out your thought about the stock P-38F and the Zero.

    The stock P-38 has a range of only 330 miles and a top speed 15 mph too slow, so nothing to gain there. Adjusting the speed through a decrease in drag gained 63 miles in range which is right about where I started out with the air file I am using.

    I replaced the P-38 prop with the Zero prop values and only gained 11 miles in range. It also increased the mph speed but only by 4 mph.

    It was a possibility but only a small gain there unfortunately.

    Thanks for the ideas, it's interesting to explore them.
    ALL original CFS2 airfiles have incorrect drag values. Reducing drag values, I succeed to get more range and speed to F4F, F6F and other planes They behave as the real thing. I intended to upload them but my computer crashed. I became so depressed that I decide to give me a little time of CFS2...

    Maybe I'll redo them.

    Pepe

  23. #23
    I did a test flight with the P-38G,taking off from Henderson.Round trip was 945 miles.

    300 gallons of fuel,climbed 10,000ft and speed was 189 mph (165 kts ).When back at Henderson still had 11% of fuel.

    The airfile and cfg were edited by Pen32Win and Talon.

    TheBookie

  24. #24
    Hi TheBookie

    I have those air files too. I am getting some of the numbers I want with the G now. I tested both with the same test mission set ups to see how they compared to see if I have been wasting my time. The distance test is set up for when the planes run completely out of fuel.

    With Pen32Win/Talons P-38G w/300 gallons the numbers:

    Distance at 275mph cruise is 569 miles.
    Distance at 165 mph cruise is 1187 miles
    Top speed at 25000 feet is 414 mph (19 mph too high)
    Top speed at S/L is 359 mph (19 mph too high)
    RPM spool up time to 10% both engines is 30 seconds

    With the P-38G files I have been working on w/300 gallons numbers:

    Distance at 275mph cruise is 574 miles.
    Distance at 165 mph cruise is 1109 miles
    Top speed at 25000 feet is 398 mph (3 mph too high)
    Top speed at S/L is 360 mph (20 mph too high)
    RPM spool up time to 10% both engines is 19 seconds

    I'm still short distance on max cruise 275 mph (mean of high and low mph stated in Manual) and too high on top speed at 25,000
    I know to get to the aircraft performance I will have to cheat a little bit. CFS2's game algorithms aren't all that precise and I am trying to get good performance numbers versus exact physical specifications. So by adding 24 gallons of fuel and adjusting the drag to get correct stop speed at 25,000 feet I get these performance numbers.

    Distance at 275mph cruise is 600 miles. (exact)
    Distance at 165 mph cruise is 1253 miles
    Top speed at 25000 feet is 395 mph (exact)
    Top speed at S/L is 359 mph (19 mph too high)
    RPM spool up time to 10% both engines is 19 seconds

    I am at a loss to adjust the 165 mph cruise and the sea level speeds. When I do that, the 275 mph cruise distance and the top speed at 15000 feet decrease significantly. So I am going with the lesser of two evils and keep the 275 mph cruise and 25000 feet numbers.

    BTW here is where the stock DCC P-38G numbers are at.

    Distance at 275mph cruise is 560 miles.
    Distance at 165 mph cruise is 1077 miles
    Top speed at 25000 feet is 405 mph (10 mph too high)
    Top speed at S/L is 356 mph (196 mph too high)
    RPM spool up time to 10% both engines is 35 seconds
    Cheers,

    Captain Kurt
    ------------------------------------------------------
    "Fly, you fools!" Gandalf the Gray

  25. #25
    Hello Captain Kurt,

    There are quite a few things that can be done to tune the cruise performance of your aircraft.
    I work with CFS1, but the principles should be the same.
    Keep in mind that a drastic change such as reducing the Coefficient of Drag of your airframe MAY allow you to hit one particular target performance parameter, but it usually screws up some thing else if the AIR file was well tuned to begin with.

    First of all, are you actually using the recommended RPM and Manifold Pressure settings for cruise according to the Pilot's Manual?
    Is the Engine Power output approximately where the manual would suggest it should be?
    The chances are that it won't be.
    I believe that most people, myself included, only bother fine tuning the output at Maximum RPM and Military and Emergency Manifold Pressure settings.
    This can be adjusted by using Records 508 and 509 and POSSIBLY Record 507 as well.
    I don't know if you configure with Auto-Mixture or how CFS2 handles Auto-Rich and Auto-Lean.
    CFS1 basically does not, but I am working on a project to address that issue in a way.

    If you haven't already tried it, Jerry Beckwith's Test Panel is a really excellent tool to let you know what the numbers are that you are actually working with.

    If you are getting the expected Engine HP output and believe the airframe drag is correct but are still not able to achieve the correct cruising speeds, check also whether you are flying at the correct altitude.
    Note that an escort mission in Europe is typically flown at higher altitudes and higher speeds and range tends to be SHORT.
    The extreme ranges that were achieved in the Pacific were flown at much lower altitudes, very low RPM, coarse propeller pitch, and wide open throttle with little to no supercharger boost.

    If you find that the altitude is correct but speeds are still too slow, then perhaps it MIGHT be worthwhile to do some tuning with the Propeller Tables.
    If you intend to go that way, before you start, it is worthwhile to determine what conditions should NOT be affected by your tuning.
    Typically this would be
    Maximum Speed at Sea Level
    Maximum Speed at Altitude
    Best Climb Speed.
    What you are looking for is Propeller Efficiency and Pitch at a particular range of Advance Ratios.
    Typically the Advance Ratio at Cruise is going to be pretty different from Maximum Speed, but it may not be that different from the Best Climb Speed.
    If you make any adjustments here, go slow and try to keep the curves as contiguous as possible.
    It is worthwhile to build a spreadsheet as I did for my "Flying Swallow" (Kawasaki Ki 61-I Hien) Project to see what might be happening when the simulator interpolates between curves.

    Without knowing any more, it is hard to make any very specific suggestions.

    By the way, when you doubled the fuel tank capacities in an attempt to increase range, did you also try to reduce the fuel weight per gallon from the standard 6.0 pounds per gallon down to 3 pounds per gallon?

    - Ivan.

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