Anyone interested in 'tuning up' flight dynamics on this DC-4?
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Thread: Anyone interested in 'tuning up' flight dynamics on this DC-4?

  1. #1

    Anyone interested in 'tuning up' flight dynamics on this DC-4?

    I don't know if anyone does requests, but I figured I'd ask. There's a real nice Buffalo DC-4/C-54 air tanker model (visual model in particular) but it flies like a brick. Here's a link to the model, unfortunately I couldn't find it here so please excuse me for using a link to another simulation site:

    http://www.flightsim.com/file.php?cm=INDEXCALL&sPos=0 It's the 5th one down the page. dc4_v21.zip

    Obviously, it's a heavy old piece of vintage iron and I don't expect it to perform out of character, but this pig can barely get off the ground. The flight dynamics (specifically takeoff performance) are definitely unrealistic. I don't have the exact performance numbers myself, but I know that fully loaded DC-4 air tankers used to take off from Hemet-Ryan Airport all day long.

    So I use that as a benchmark to show how far off the performance of this model is. Not only can I not get off the ground at Hemet-Ryan without overrunning the end of the strip by 50 meters, but the thing claws for every foot of altitude you can get until you finally get up to 130 KIAS. To show how far off this is from the real aircraft, the runway in FSX depicts the current runway at Hemet-Ryan, which has actually been lengthened since the DC-4s used to fly there.

    The rest of the flight model's aspects seem fine. It's the takeoff and initial climbout where the performance is totally unrealistic. So I'm not sure where one would start, but since it flies fine once airborne and up to speed --I wonder if just giving the engines a smidge more power would do the trick. I have no clue if it's a lack of speed or a lack of lift... but when I take off, I'm holding the brakes and allowing the engines to reach full song before I start my takeoff roll. Even with that, I'm only at 93 KIAS by the end of the runway. Flaps are extended fully and I still can't get off the ground until 98 KIAS which occurs well after I'm in the dirt.

    The next problem occurs once finally leaving the ground. Any attempt at gaining altitude results in the airspeed bleeding off. You're stuck trying to maintain 20 feet of altitude with an aircraft that refuses to accelerate in anything but level flight. Obviously cleaning up the aircraft needs to happen because you need to get some airspeed, but you can't because anything less than full flaps puts you right back on the ground. It is POSSIBLE to get into the air after much wrangling, but it's an unrealistic struggle for altitude that leaves you traversing the countryside under 100 feet for two or more miles.

    Anyone want to take a crack at it? I will salute you! :salute:

  2. #2
    You do not state which of the two models you are flying. There are two FM's, one representing the A-F variants and one for the latest release of the G variant. Reading the included docs and checklist, it states that flaps should be at 20 and rotate at 105knots.

    Before Takeoff
    Run-up Complete
    Flaps to TAKEOFF - 20 degrees
    Trim: 1 mark above center
    Flight Controls: Full Travel
    Transponder: SET
    Cowl Flaps: MID (down one click)

    Takeoff
    Throttle to Takeoff Power (full throttle)

    Rotate at 105 kts @ MTOW: 73,000 lbs
    Gear UP @ positive rate of climb (≤500 fpm)
    Flaps UP > 120 kts
    at 140kts, 300 ft AGL, 500 fpm: METO Power (43" MAP, 2550 rpm)

    Climb
    >140 kts, 1500 ft AGL: Climb Power (40" MAP, 2300 rpm)
    Climb @ 135-145 kts, 500-1000 fpm
    Maintain MAP with throttle as you climb
    Radar (if fitted): ON as required
    Seat Belts: as required


    I had no issues getting either model off the ground on a 5000' runway with 1 notch of flaps at 105-110knts. Climbout was no issue and she gained speed nicely at 500fpm climb.

    Be sure you have a little nose up trim, and that throttle is at 100%.
    Milton Shupe
    FS9/FSX Modeler Hack

    My Uploads at SOH - Here
    Video Tutorials - Gmax for Beginners

  3. #3
    Milton, thanks for the reply I really appreciate it! Thanks for all the info as well!

    Just had to come back in here and eat my own words. I used the flap position you mentioned, and set the trim WAY up... and got off the ground on Hemet's 4300 foot runway! Had a good climbout as well. I have to take back everything I said about this model, because I was able to emulate the exact 180 degree left traffic ascending departure flown by the air tankers. Thanks again Milton.

  4. #4
    I would suggest a a start to get the AFSD utility by Herve Sors and see what HP and thrust the engines are developing on takeoff. If the thrust and drag are in the correct proportion, but both low, the acceleration will be slow, if they are in proportion, but high, the acceleration will be too fast. Also check that the props are fully advanced to high RPM.

    Something to consider is that the fire bombers weren't going far and carried little fuel. So czech the loadout and total weight.

    Cheers: T

  5. #5
    Just downloaded and tested this with 30% fuel and 5800 lbs payload. Easily off the rwy at about 2500 ft. Developing 1380 hp at 45" and 2700 RPM, thrust is 2624 lbs.

    Cheers: T

  6. #6
    Quote Originally Posted by fliger747 View Post
    Something to consider is that the fire bombers weren't going far and carried little fuel. So czech the loadout and total weight.
    Thanks T

    That's an impressive takeoff distance! You're right, the sorties typically were not that far... but I'm not sure on the fuel they'd run, because they would generally fly 5 or 6 hours without having to refuel.

  7. #7
    Quote Originally Posted by airattackimages View Post
    Milton, thanks for the reply I really appreciate it! Thanks for all the info as well!

    Just had to come back in here and eat my own words. I used the flap position you mentioned, and set the trim WAY up... and got off the ground on Hemet's 4300 foot runway! Had a good climbout as well. I have to take back everything I said about this model, because I was able to emulate the exact 180 degree left traffic ascending departure flown by the air tankers. Thanks again Milton.
    I am happy that you have this sorted out. I always find FSAviator's flight models to be spot on.
    Milton Shupe
    FS9/FSX Modeler Hack

    My Uploads at SOH - Here
    Video Tutorials - Gmax for Beginners

  8. #8
    Quote Originally Posted by Milton Shupe View Post
    I am happy that you have this sorted out. I always find FSAviator's flight models to be spot on.
    I'm happy too, I appreciate your help! I was always bummed out that I couldn't fly this gorgeous machine. Now I can! And of course, having actual specially made air tankers with accurately modeled retardant tanks are rare! Another reason I look forward so much to the F7F and P2V5/7.


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