Project Martin A-30 Baltimore - Page 3
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Thread: Project Martin A-30 Baltimore

  1. #51

    Interesting findings.

    Hello Ivan,
    Hmmmm... Interesting, thanks very much for your comments.

    Possibly itīs the Beckwith Gauge programmed for a slightly different CPU - i.e. Pentium, and it reacts differently to the AMD CuadCore that I have, or maybe itīs Windows XP instead of Windows 98. Iīll try it in the Pentium 4 Laptop here with Win98 as soon as I have time to rig it up.

    I found that implementing any kind of Emergency Power to use with Key F10 does have its advantages: I gives 6 more HP for Meth-Alcohol and Water Injection, and 7 for WEP. So now the speed I get at 15000 ft is 314 or 315 mph if the SL max. is at 284 mph, and 320 mph if the SL max. is 290 or 289 mph. I chose Water Injection because it doesnīt ruin the engine - the water-cooling factor seems to be beneficial.

    To possibly widen the performance vs. altitude difference range, I lowered the friction and torque even more, to .39 and .585 again, but it didnīt get any better, not even going down as far as .30 with friction and 0.557 with torque.

    I even tried fiddling the Induced Drag vs. Zero Lift Drag even more - i.e. ID at over 7000 and 0LD at about 60, but there was no change either. Possibly Iīll go for 290 mph at SL and 320 mph with Water Injection.


    Iīll see... Thanks again!
    Cheers,
    Aleatorylamp

  2. #52
    Hello Aleatorylamp,

    I hadn't wanted to get into any significant detail on the Martin Baltimore, but could not really do anything useful without doing some research myself, So....

    I am pretty convinced now that the data you are using from the table on Page 112 of Monografie Lotnicze 97 is simply incorrect.
    It appears to be contradicted by multiple other sources.

    I have some serious doubt as to whether the engine models specified are actually correct and am pretty sure the power ratings and maximum speed at altitude for the Baltimore Mk.V are both incorrect.
    A lot of the other data and drawings are pretty good, but I do not believe the engine data is good.

    I suggest you do some general research with other sources and see if you come to the same conclusion.

    - Ivan.

  3. #53

    Source reliability

    Hello Ivan,

    Nice conclusion... What it clear is that there are several different pieces of information for the same parameters, but I donīt know enough about aircraft engines to deduce which of these pieces of information could be the most plausible ones, in order to discover which was the most reliable source.

    I believe Iīve seen all the different specs I can get at, and the main problem is that the early and later models are not differentiated in some cases. The main information required for an .air file would be the maximum speeds, and here there are quite a few different ones. This is 305, 308, 320 and 329 mph, with or without some altitude reference.

    Of course this is a rather lamentable state of affairs, proven by the impossibility of making speeds tally at different altitudes in CFS1.

    2951 RPM max for all altitudes in CFS1 (2600 RPM on your computer):
    This coincides with the criteria of a CV propeller, but the charts rather suggest Constant Horsepower and varying RPM.

    Iīd set critical altitude at 25000 ft, thinking that the ceiling would be the criteria, but I found out that itīs the altitude upto which the blower maintains its power, in this case the 44 Mpsi. Probably mistakenly, Iīve kept Mpsi at 44 for 15000 ft., so Iīll conduct some test correcting this.

    The Specific Engine Flight Chart states an emergency maximum for 12000 ft at 41 Mpsi and maximum continuouus at 15000 ft at 41 Mpsi, so possibly the critical altitude setting for 44 Mpsi would be the 12500 in the MitchellC .air file.

    Well, At the moment, with 2591 RPM on my computer (2600 on yours), and 44 Mpsi all round, Iīm getting:

    500 ft: 1670 hp - 294.3 mph (280.6 mph without WEP)
    15000 ft: 1885 Hp - 320 mph (311.8 mph without WEP)

    Looking at the performance of the MitchellC, which appears to have about 40 Mpsi for 15000 ft, so as I said before, Iīll see what happens if I reduce ctirical altitude to ther 12500 ft given there.

    Cheers,
    Aleatorylamp

  4. #54
    Hello Ivan,

    Setting the critical altitude to 12500 like on the MitchellC, reduced performance at altitude a bit, although the Mpsi setting still remains at 44.

    I tried to get the Hp spanning from 500 ft to 15000 ft in a similar way to that on the MitchellC, arriving at following results:

    500 ft: 1603 Hp with 284 mph.
    15000 ft: 1830 Hp with 314 mph.

    If this looks plausible, then itīs better, but unless of course it doesnīt, then it isnīt.
    Now, in reality, I donīt really know what is correct any longer...

    If I knew more about aircraft engines, it shouldnīt really be too difficult for me to decide which maximum speed to use - 305, 308 or 320 mph, and at what altitutude. I think the one entry Iīve seen for 329 mph can be discarded - that much, I suppose I know. But for the others... Maybe the Mk I-III units would be candidates for 305-308 mph, and the MkV, 320 mph? I really havenīt a clue.

    Cheers,
    Aleatorylamp

  5. #55

    A matter of interpretation.

    Hello Ivan,
    Given the impossibility of getting maximum speed in the flight envelope to span 284 mph to 320 mph, possibly it is a matter of interpreting what the specifications say.

    I have seen at least 4 sources that state the maximum speed of the Mk.V Baltimore as 320 mph, and some include the altitude of 15000 ft here.

    I have seen 1 source stating 312 mph at 11600 ft, then, several others state max. speed at 305 or 308, without stating the altitude or model, and two more which say itīs 305 mph at 11.500 ft but donīt mention the model.

    Also, a few sources describing what the Baltimore flew like and the missions it did, donīt state specification details, but do say that the plane was capable of speeds above 300 mph, and that it had the performance of a fighters, being able to outrun some of them.

    This could imply that this speed was also possible at sea-level, and would consequently lead me to discard the 284 mph maximum speed at sea-level that you had initially suggested after extrapolating from the Mitchellīs performance. This speed also does not appear in any of the sources.

    So, for the sake of looking for a more realistic flight envelope, my exercise this time was to see if the speed range between Sea-Level and 15000 ft could span from about 305 mph to 320 mph, and I did a test. The result IS actually possible with procedural emergency power (no WEP enforced with F10):

    Aimed Power: 1700 hp
    Critical altitude 12500 ft
    Max. RPM all round: 2590 (2600 RPM on normal computers and yours)

    Sea-level: 1690 hp - 305.7 mph 44 Mpsi
    12500 ft: 1867 hp - 322.5 mph 44 Mpsi < this is the critical altitude.
    15000 ft: 1718 hp - 320 mph 40.1 Mpsi

    This seems to tie in with the information given by most sources. I wonder what this would be in your opinion? Useful, or useless codswallop?

    Cheers,
    Aleatorylamp
    Last edited by aleatorylamp; April 8th, 2016 at 11:01.

  6. #56

    Impossible???? Maybe Not....

    Hello Aleatorylamp,

    I was pretty sure tuning the maximum speeds to the range that you wanted wasn't very hard, so I decided to try it myself.
    I started with the Mitchell C AIR file and took a few screenshots to show the numbers I am getting on a Pentium 3 866 MHz before and after some very minor tuning.

    The picture of the Mitchell model has no real relevance but I thought it looked nice.

    The only tuning I did was to adjust the Zero Lift Drag down to 62 using AirEd.
    I did absolutely NOTHING else. No Engine Tuning was required to get this performance....

    If your target performance was 284 MPH @ SL and 320 MPH @ 15,000 feet, this would be close enough I think.

    The R-2600-13 on the B-25C and the R-2600-29 on the A-30A are close enough to be the same engine and you already have the AIR file containing my version of the R-2600-13.....

    - Ivan.
    Attached Thumbnails Attached Thumbnails Original-500.jpg   Original-12500.jpg   Original-15000.jpg   Revised-500.jpg   Revised-15000.jpg   MitchellC-FlightTest.jpg  


  7. #57
    Hello Ivan,

    Good heavens, how easy that was! A nice surprise, to say the least, thank you very much.

    The Germans say, "Why easy, when it can be done complicated too?".
    ("Warum einfach, wenn es auch komplitziert geht?").

    So for a start Iīll just take the whole MitchellC .air file and do the same. Then Iīll shift over the Wing section and adjust the weights, and fuel, but nothing else just in case something breaks!

    I was wondering about the 284 mph maximum speed at SL you had recommended, because it contradicts the information reflected in all the sources. As far as I can see, it comes from a calculation derived from the Mitchell, that had the same 1700 hp engines and similar performance, although it was a bit slower.

    Well then, letīs see how it goes now! Thanks again.
    -Yes, the picture does look nice! ...I like the slightly negative dihedral.

    UPDATE:
    I used the MitchellC .air file and transferred the weight, fuel and main wing parameters over.
    I also had to transfer the smaller propellers diameter: 11 ft instead of 12.58 ft.
    Zero Lift Drag is at 69 and induced drag is at 6800, as opposed to your 62 and 6750.
    The results I got are as follows, all at 2592 RPM:

    500 ft: 44 Mpsi, 1618 hp, 284.0 mph
    12500 ft: 44 Mpsi, 1788 hp, 327.4 mph (speed considerably higher than yours)
    15000 ft: 40.3 Mpsi, 1654 hp, 326.0 mph (speed slightly higher than yours).

    Obviously the smaller propeller is giving the higher readings.
    I could perhaps try reducing torque and/or increasing friction a bit.

    Cheers,
    Aleatorylamp
    Last edited by aleatorylamp; April 9th, 2016 at 02:34.

  8. #58

    Almost bang on!

    Hello Ivan, again!

    Before moving the Friction or Torque Graphs, it occurred to me to lower Boost Gain from 2.54 to 2.4, which in turn lowered the Manifold Pressure slightly at altitude.

    Now the results are very much closer:
    500 ft: No change: 1618 hp, 284 mph, 44 Mpsi
    12500 ft: 1770 Hp 326.2 hp, 43.5 Mpsi
    15000 ft: 1615 hp, 322.6 mph, 39.5 Mpsi

    This seems to be acceptable, Iīd wager.

    Cheers,
    Aleatorylamp

  9. #59
    Hello Aleatorylamp,

    Perhaps you don't care, but I think you should check out the Yaw-Roll coupling if you plan on developing from the MitchellC AIR File.
    There were a lot of factors that were tuned to make that happen and offhand, I don't remember where they all were, so that is why I was recommending against it.

    I get the distinct impression that you did not really understand the Engine Tuning Tutorial.
    I am not saying my method is the ONLY way, but if you are intending to use it, it helps to be consistent.

    Without getting into the extreme detail, here is the basic idea:

    1. We need to tune THREE points on the graph of Power versus Altitude:
    They are at Sea Level, Critical Altitude, and Service Ceiling.

    2. Tuning the Sea Level Power should be done first.
    We need to match Three Pieces of Data: Manifold Pressure, RPM, and Horsepower.
    I usually do this by adjusting Torque.

    3. Next is the Power at Critical Altitude.
    This is done by ADJUSTING SUPERCHARGER BOOST.

    4. Last is tuning the Service Ceiling / Absolute Ceiling and this is done by adjusting Torque and Friction and balancing their effects so that the Sea Level Power is not altered significantly.

    .....So....

    Leave the Torque / Friction alone at this point and just drop the Supercharger Boost a little bit.

    Did you notice the choices I made as far as tuning the power curve for the Mitchell?
    Note that the Sea Level Power and Critical Altitude Power are both a touch lower than one might expect.
    This was done so that the power curve would not be too high at any point in between.

    There are other ways to tune the performance without affecting the power curve but there are other side effects.

    For what it's worth, earlier versions of the Mitchell were slightly faster than mine.
    I built the B-25C/D or Mitchell Mk.II because I thought it was a good balance of combat capability and flight performance.
    Later versions were even slower.

    Perhaps it is worthwhile for you to post a little of the development and service history of the Baltimore.
    Various conflicting information simply did not make sense until I read a bit about the history and put together the most likely scenario.
    That history and logical developments is why I do not believe the Page 112 Table is correct.
    Also worthy of discussion is how the Baltimore derived from the Maryland and perhaps a little speculation as to why the US military gave it an official designation but never used the aeroplane operationally.

    - Ivan.

  10. #60
    Our messages crossed. I started my post around the same time you did and was interrupted by guests.
    Perhaps you DO understand what I was trying to explain in the Engine Tuning Tutorial.

    - Ivan.

  11. #61
    Hello Ivan,
    I hope you enjoyed your guests!

    With Yaw-Roll coupling, do you mean Adverse Yaw or perhaps Roll Moment due to ailerons? Is this because of the dihedral on the Baltimore, that the MitchellC didnīt have?
    I havenīt done much flying with the plane so I donīt know what it feels like yet, but Iīll see.

    I think I understood most of the Engine Tuning Tutorial, although perhaps not perfectly.
    My main problem was adjusting the increased power after reducing the MitchellCīs 12.58 ft propeller blades to the Baltimoreīs 11 ft ones. Obviously I didnīt want to fiddle with the propeller tables!

    I did indeed adjust friction and torque graphs for the SL performance first, at 44 Mpsi and 2600 RPM, but I had to keep the Hp on the low side, like it is on the MitchellC .air file, so as not to get far too much power at altitude. Hence no 1700 Hp.

    I left the critical altitude as 12500 ft as it was in the MitchellC file. I found no reference to it in any sources. I suppose I could adjust that too, but what to? The 2-speed single blower had L and H settings, depending on altitude. Maybe L below 9000 ft and H above? I donīt know, but it wonīt work for CFS1 anyway. I suppose critical altitude could be anything from 10000 to 12500.

    Then, the problem with adjusting friction and torque again for higher altitude was that it affects the SL performance too, so had to do it a different way. As Iīd read about the boost gain in the Tuning Tutorial, I applied that, and I think it worked rather well. As you stated in your last post, you are absolutely right, it was the best thing to do, although it did take me some time to realize!

    Yes, I noticed the choices youīd made, and why, as regards as regards Sea Level Power and Critical Altitude Power - they are both a little lower.
    In my case I couldnīt curb a small surge in speed at critical altitude, but on the other hand, at 15000 ft performance is more correct.


    I read about the basically similar Martin 167 Maryland, with its 1050 Hp engines, its tight fuselage and the same bomb-load, and how the Baltimore was developed from it. It had the same wings, but a deeper fuselage, to enable the crew to move around inside, although it was still very cramped. Then, the higher 1600 hp engine power gave better performance, even more when the engines were upgraded to 1660 hp, and finally to 1700 hp ones.

    Both models seem to have been built for the East-European theater. I suppose the Americans didnīt want to use them because they were developing the Mitchell and the Marauder, which they liked more. Also I noticed that initially the designation A-30 was for the Maryland... However, I havenīt got enough time to provide a summary of the aircraftīs development history, or speculating too much about it - I donīt know enough.

    Working on the .air file is still a bit confusing. I still donīt understand why we are using 284 mph max. speed at Sea-Level, as this does not appear anywhere in the sources, but I accept it gladly because you know much more about the subject than I do!

    Anyway, after getting the .air file into a more or less acceptable state, I want to get on with actually building the plane. At the moment itīs only a cardboard model made with 2D templates like a toy - enough for .air file tuning, though!


    Cheers,
    Aleatorylamp
    Attached Thumbnails Attached Thumbnails Baltimore1.jpg  

  12. #62
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    i've been following the conversation with interest, when,
    "only a cardboard model made with 2D templates like a toy
    "
    caught my attention.
    i've been thinking about doing the same with the a-20.
    what scale did you use?
    got any pictures to post?

    hahaha...ooops.
    i took your statement literally.
    sometimes the magic works.
    sometimes it doesn't.

  13. #63

    A Little Bit of History

    This is the Development History as I understand it:

    The Martin 167 Maryland or A-22 was developed for a USAAC competition for a Light Bomber.
    The competition was won by the Douglas A-20 Havoc.

    The French ordered it because it was available and could be produced quickly.
    When France fell, Great Britain took over the French orders and placed more of their own.
    The Maryland had no ability for the crew members to change positions or even communicate with each other.
    The Baltimore was designed to cure some of these problems.
    Communications was added and though there still was no ability for another crew member to take over for the pilot if needed.
    Engines were also upgraded to the Wright GR-2600-A5 and later the GR-2600-A5B series which gave 1600 HP.

    When Lend-Lease was adopted, the Baltimore needed to become "Lend-Lease"-able.
    In order to qualify for Lend-Lease, it had to be adopted by and produced under contract to the US Military.
    Thus the Baltimore Mk.III became the Martin A-30.
    The engines for US military aircraft are GFE, so R-2600-19 engines of 1600 HP were substituted.
    I don't know if at some point they were uprated to 1660 HP or if the description just changed.
    The Mk.III to Mk.IV changed to a Martin instead of Boulton-Paul turret and different guns and the designation changed to A-30A.

    Some time during the production run of the Mk.IV, the engines were upgraded to the R-2600-29 which offered 1700 HP.
    The USAAF never used the A-30 series operationally and production ceased in 1944.

    I do not believe the R-2600-13 was ever used in this aeroplane.
    I do not know how close the R-2600-19 is to the GR-2600-A5B in detail, but the output is pretty similar.
    From the 1946 edition of Jane's, I have some reference information but have not taken the time to read it.
    The Sea Level speed of 284 MPH was from the footnote at the bottom of the Page 112 Data Table.
    You be the judge of whether it is accurate or not.
    The Polish Kagero books tend to be pretty good with a lot of primary sources but in this case, I believe at least with the engine models, there were significant errors.

    Although the Baltimore and Mitchell used some of the same engines, they are not really competing designs.
    The Baltimore is a Light Bomber with a maximum bomb load of 2000 pounds.
    The Mitchell is a Medium Bomber and carried 2-3 times the bomb load.

    This is a fairly informal summary and interpretation of what I have found thus far.

    It is pretty hard to design without doing some research in detail because one has to have a target to design toward.

    - Ivan.

  14. #64
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    if i might add my two cents...
    forget about the 284mph.

    as Ivan has said,
    "The Sea Level speed of 284 MPH was from the footnote
    at the bottom of the Page 112 Data Table."

    it should also be noted,
    there are two *** 284mph footnotes.
    one for the Mk I, the second for the Mk II.
    since you are working on the Mk V,
    the 284mph footnotes are irrelevant.
    sometimes the magic works.
    sometimes it doesn't.

  15. #65
    Hello Smilo, hello Ivan!

    It was getting very confusing indeed as regards the SL max. speed, wasnīt it?
    Actually Iīd been thinking that it would have been the earlier models which would have had the 284 mph.

    Thanks for the clarification.

    Well, well, OK then... so my thoughts about the MkVīs SL performance being above 300 mph are more likely, and it will not be necessary to reduce the Boost Gain after all. So, looks like itīs back to square one then. Too bad I threw out all the previous .air file trials, thinking Iīd finally arrived at the correct one. Anyway, it was an interesting exercise.

    Ivan, a good historical development summary - nicely done!

    UPDATE:
    I found my notes in the waste-bin so it wasnīt too difficult to get close to what Iīd had before.
    I got it better than that too, by lowering the critical altitude to 9000 ft - this reduces the power surge at altitude quite a lot, and I then kept the Boost Gain at 2.45, and corrected the Drags.
    So, this is where itīs now, all at 2591 RPM aka 2600 RPM:
    500 ft: 44 Mpsi, 1702 Hp, 305 mph.
    9000 ft: 44 Mpsi, 1825 Hp, 317.5 mph (power surge here)
    12000 ft: 44 Mpsi, 1871 Hp, 321.5 mph (power surge continues)
    15000 ft: 40.2 Mpsi, 1734 Hp,320.4 mph

    With the critical altitude at 9000 Iīd have expected the Mpsi to drop sooner... but such is life.
    Itīs looking quite good for the MkV, Iīd say. Would this be OK now, do you think?

    Cheers,
    Aleatorylamp
    Last edited by aleatorylamp; April 10th, 2016 at 13:20.

  16. #66
    Hello Aleatorylamp, Smilo,

    As I see it, Aleatorylamp is the author / designer and it is entirely up to him regarding data and design parameters.
    We are all coming up with differing interpretations though which is interesting.

    First of all, 13,500 feet is the critical altitude of the R-2600-29,

    The idea of a "Fast Bomber" is a relative concept: What was it faster than?
    The A-20 Boston / Havoc was truly a fast bomber but actually had less engine power with the R-2600-23 than the R-2600-29.
    Late models (Boston IV) would have been good for about 340 MPH @ 10,000 feet.
    The B-25 was probably good for 315 MPH @ 15,000 feet and was not known as a "Hot Ship".
    Later models such as the B-25J were only good for about 285 MPH at best altitude so were much slower.
    Strangely enough, the B-26 Marauder WAS known as a "Hot Ship" and was probably closer to 320 MPH at critical altitude in the early versions.
    Later versions were only good for about 290 MPH at best.

    The British never used this aeroplane outside the Mediterranean Theater and the USAAF never chose to use the aeroplane at all.
    One has to wonder why this was the case.

    I believe the reason the aircraft got the reputation for outrunning fighters was because the fighters it met were all on the slower side.
    The Italian Biplanes were quite slow with the exception of the latest Fiat CR.42 with the Daimler Benz engine and those were very rare.
    With the exception of the Macchi C.202 just about all the Italian Monoplanes were also fairly slow early in the war.

    One thing worth noting is that 284 MPH @ Sea Level would still make it able to escape all but the latest model Spitfires.

    Aleatorylamp, you need to decide how much you trust the data from the Kagero book.
    In general, I believe their data is pretty good, but they DO make mistakes as I pointed out regarding engine specifications.

    One last thing worthy of note if you believe the 284 MPH @ Sea Level speed for early Baltimores is that
    100 HP extra on the Baltimore Mk.V would only mean about 5 MPH increase.
    The extra drag of the late model Martin turret and especially for the Boulton-Paul turret would account for about the same IMO.

    - Ivan.

  17. #67
    Hello Ivan,

    Thanks for your well-explaned e-mail.

    Well, in German they say:
    "Wer hat die Wahl, hat die Qual"
    - i.e. He who has the choice, has the torture...

    So, Iīll have to decide which .air file Iīll use!
    Cheers,
    Aleatorylamp

  18. #68
    Hello Aleatorylamp.

    Yes, you get to have fun with this one.
    I have a much more interesting Engine Tuning task with the Allison V-1710-81 for the P-40N.
    The numbers there REALLY don't fit well with the way CFS handles WEP so the result is certain to be a compromise solution.

    - Ivan.

  19. #69
    Hello Ivan,

    And I thought it was I who was having difficulties...
    ...but maybe itīs more fun when the toil is greater because success is also greater afterwards.

    As the Allison engine you are talking about has a single-stage, single-speed blower as far as Iīve been able to see, one is led to believe that CFS1 would have no problem in handling it, but from what youīve just said, that doesnīt seem to be the case.

    Just out of curiosity, I wonder what it is that CFS1 canīt handle here - is the cieling too high, the power difference to great, or is it the automatic manifold pressure regulator?

    Anyway, good luck!
    Cheers,
    Aleatorylamp

  20. #70
    Hello Aleatorylamp,

    When operating above Maximum Continuous, there generally is a restriction on conditions of use or duration.
    Any power setting above Maximum Continuous is not unlimited.
    From a practical consideration, some engines are much more durable and can take continuous operation above this setting regardless of what the manual says.

    The late model Allison engines had more supercharging and thus less tolerance for over-boosting (WEP).
    I don't believe it is reasonable to allow unlimited use of the WEP power rating of 1480 HP when in theory, the take-off rating is only 1200 HP.

    The problem comes when I tried to match the T-O power output and found that the WEP power output is way too high.
    Both ratings are at 3000 RPM and the Manifold Pressure settings are stated in the manual so there is not much room for adjustment.
    This is the first problem.

    The second problem comes from the way CFS handles WEP.
    CFS simply raises the Manifold Pressure when WEP is engaged.
    Above the engine's critical altitude, this should have no effect because there is no additional Supercharger capacity that can be used.
    Unfortunately CFS continues to let the MP increase which has the effect of raising critical altitude with WEP while in reality, it should be lower.

    - Ivan.

  21. #71
    Hello Ivan,

    Thanks for the interesting details on the different ways that this engine was made to do what it did, overcoming certain limitations.

    Also interesting will be the possible ways to be found in the .air file to make the engine do its work and overcome the simulatorīs limitations!

    Cheers,
    Aleatorylamp

  22. #72

    Builderīs block

    Hello all!
    Just to send a sign of life...
    For the moment I must be under a spell of Builderīs Block - if I were were a writer it would be Writerīs Block. Workwise thereīs a teaching job Iīve got at midday until Spetember that gets in the way of lunch and housework, but hopefully Iīll have my energy back with some free afternoons as soon as the afternoon classes take their holidays in June.
    Cheers,
    Aleatorylamp

  23. #73
    Hello Aleatorylamp,

    Regarding Builder's Block:
    We have all been there. Hopefully this too shall pass.
    I have been having a bunch of other issues to deal with lately as well as other things I have wanted to do.

    Regarding the discussion of superchargers in the Warhawk thread, perhaps it is worth a (very) short thread of its own?
    I don't know if there is really a point though because we are both pretty much on the same page and I do not believe there is a solution to be found.

    - Ivan.

  24. #74
    Hello Ivan,

    Yes... every time I sit down and start AF99 I close it again... Thankfully this will pass in a few weeks as soon as I get my free afternoons back. I used to have free mornings, but they wonīt be back until september!

    Well, for superchargers, I wonder if thereīs enough new information for a thread of its own. From what Iīve been able to obtain during my experiments with some of the stock CFS1 models, it seems that there is enough evidence, at least in my humble opinion, for me to implement WEP in the last 10% of the normal travel of the throttle lever. Iīll most probably do it this way for the Baltimore.

    As the 90% throttle position for the limit between WEP and non-WEP is not altitude-dependant in CFS1, this can easily be marked as a reddish zone on the throttle gauge if necessary, but then, as the 90% power easily keyboard-set, this may not even be necessary.

    Anyway, this way, the bug by which WEP increases power above the ceiling, disappears.

    Cheers,
    Aleatorylamp.
    Last edited by aleatorylamp; May 7th, 2016 at 05:04.

  25. #75

    Supercharger in the .air file, aproximating the numbers

    Hello Ivan,
    Iīve been adjusting supercharger performance to try and get it closer to the values in the Specific Engine Flight Chart for the R-2600-13 engine, and I wonder if itīs getting to be satisfactory:
    From this chart, data pertinent to the .air file as a guide line, is:
    1) TAKE-OFF POWER
    2) MAXIMUM EMERGENCY POWER
    3) MAXIMUM CONTINUOUS POWER

    Low blower is indicated:
    - always for take-off at sea-level,
    - for max. emergency power under 10500 ft,
    - for max. continuous below 11000 ft.
    However, the CFS1 Blower is single-speed, being either OFF or ON. In this case, OFF from 0% to 90% throttle (NON-WEP FULL POWER), or ON, FROM 91% to 100% throttle (WEP).
    WEP is not implemented with F10, avoiding the above-ceiling performance distortion.


    The A-30 Baltimore MkV .air file has 2.15 boost gain, and speeds adjust quite well using a 0.53 Zero Lift Drag setting. What seems to be looking a bit low are some of the the Manifold Pressure values, but this keeps the power within more correct limits at altitude, and curbs the surge between 4500 and 6700 ft and also higher up.

    1) TAKE OFF POWER, (WEP)
    ---------------------------
    SPECIFIC ENGINE FLIGHT CHART, 2600 RPM:
    44.0 MPSI, 1700 HP, SEA LEVEL, LOW BLOWER
    A-30 Baltimore .air file:
    44.0 MPSI, 1701 HP, SEA LEVEL, 310 MPH - HP and MPSI seems fine.


    2) EMERGENCY MAXIMUM, (WEP)
    -------------------------------
    SPECIFIC ENGINE FLIGHT CHART, 2600 RPM:
    42.0 MPSI, 1700 HP, 4500 FT, LOW BLOWER
    41.0 MPSI, 1700 HP, 12000 FT, HIGH BLOWER
    A-30 Baltimore .air file:
    44.0 MPSI 1757 HP, 4500 FT, 316 MPH - 57 HP and 2 MPSI over.
    39.8 MPSI 1666 HP, 12000 FT, 320 MPH - 216 HP over and 1.2 MPSI under.

    3) MAXIMUM CONTINUOUS, (NON-WEP)
    --------------------------------------
    SPECIFIC ENGINE FLIGHT CHART, 2400 RPM:
    38.0 MPSI, 1500 HP, 6700 FT, LOW BLOWER
    39.0 MPSI, 1350 HP, 15000 FT, HIGH BLOWER
    A-30 Baltimore .air file:
    39.7 MPSI, 1591 HP, 6700 FT, 312 MPH - 91 HP and 1.7 MPSI over.
    32.4 MPSI, 1350 HP, 15000 FT, 311 MPH - HP exact, 6.6 MPSI under.

    Would you say this is getting close, or are we still far out?
    Thanks in advance for your time and your opinion!
    Cheers,
    Aleatorylamp

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