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  1. Roy Holmes

    MSFS CJ4 - N1% Throttle Position / Amount

    Mark, If you want to understand what corrected means in the context of engine performance go have a trawl in the Aircraft Design Flight dynamics forum or download "FS Thrust vs Altitude calculations" from page 11 of the Resources part of this website. I have a nasty feeling that the MSFS team...
  2. Roy Holmes

    Takeoff-roll at TOGA Engine Issues

    I see your point, but is it relevant? First, what is the difference for N2, not CN2? I think it is 103.2 Second, If you want N1 to be exactly 104 at 0.1 Mach so that thrust is more accurate, change CN1 in 1502 rather than messing up the whole thing by changing 1503/1504. It is an interesting...
  3. Roy Holmes

    Takeoff-roll at TOGA Engine Issues

    You are wrong At 0.1M and SL, Sqrt(Theta2) = 1.0002, so for 104% N2, CN2 would be 104/1.0002=103.8962% N2 would be 103.8962*1.002 =104. So N2 stays at 104% when at full throttle at all Mach numbers and altitudes. Once you have created the tables, forget about corrected values. If it does not...
  4. Roy Holmes

    Takeoff-roll at TOGA Engine Issues

    Not exactly, CN2=N2/Sqrt(theta2) N2=CN2*Sqrt(theta2) At 0.1M and SL, Sqrt(Theta2) = 1.0002, so for 104% N2, CN2 would be 104/1.0002=103.8962% N2 would be 103.8962*1.002 =104. Remember the uncorrected value should vary with throttle only, altitude and Mach should not change it much except a tad...
  5. Roy Holmes

    Takeoff-roll at TOGA Engine Issues

    I have a strong suspicion that the engine code has been changed. For example, with a single shaft turbine, ie N1=N2 and 1502 (n2_to_n1_table) set accordingly, N1 is different from N2. On the ground after start you will get the idle N1 you have set, but once you start to move it goes up to...
  6. Roy Holmes

    MSFS2020 New [FLAPS] Section parameters

    The main requirement from flaps is to allow the airplane to fly slower usually in connection with take off and landing. Since the weight is relatively constant that means they need to generate the same lift but at lower speed. Lift is proportional to indicated speed squared and directly with...
  7. Roy Holmes

    MSFS fully free castering tailwheels...

    Tailwheel steering has a complex set of effects. First, a tailwheel airplane is unstable in yaw when taxying and a lot of the effort by the pilot involves trying to follow the centreline of the taxiway. You steer the airplane by using differential wheel brakes or the rudder effect of propwash...
  8. Roy Holmes

    Fishtailing, oscillation at speed

    This is probably due to the new "Realistic flight dynamics" which assumes that all aircraft bounce around when flying. And yes the controls are too sensitive but that can be adjusted. Roy
  9. Roy Holmes

    MSFS2020 New [FLAPS] Section parameters

    The bit that worries me is the mess they are making of jet performance. That was one part of the old sim that worked really well and they now have PIDs where you don't need them, response is awful and as for accuracy, it has disappeared. What is the point of getting drag perfect if the thrust...
  10. Roy Holmes

    MSFS2020 New [FLAPS] Section parameters

    Slats or leading edge flaps are used to allow the wing to go to higher angles of attack (AOA) without boundary layer breakaway. The can delay the stall by quite a lot depending on the wing design. Lack of slats is one of the biggests issues in the sim when designing a swept wing fighter which...
  11. Roy Holmes

    MSFS2020 New [FLAPS] Section parameters

    Bernt, Could be something else changes for the last positions. The F-4 I flew years ago had bleed air blowing on the leading edge slats when down and also on the trailing edge flaps in the full down position. The air was bled from the compressor stage of the engines. Roy
  12. Roy Holmes

    MSFS2020 New [FLAPS] Section parameters

    The flight_model.cfg for the A320 covers Flaps.0 which are type 1, trailing edge and Flaps.1 which are type 2, leading edge. The additional 4 numbers only appear on the trailing edge flaps. The third number for both is the fraction for lift and drag added according to angular position. 0 to 1...
  13. Roy Holmes

    MSFS Fixing turboprop behavior

    The engine behaviour has changed with MSFS compared to how it worked for years in FS,FSX and P3D. There is no information in the SDK about this and I am amazed they changed from the FS method which worked really well for jets and adequately for turbo props. Right now I'm working on flight...
  14. Roy Holmes

    MSFS Start up issue

    Thanks guys, The problem was Xbox related and I now have it loading. Roy
  15. Roy Holmes

    MSFS Start up issue

    When I bought MSFS I got the Microsoft Flight Simulator Digital Ownership app add-on. I still have it somewhere in my C drive. When I start the sim I get to the desert view then a message comes up "Please insert the Microsoft Flight Simulator Game Disc" which I do not have. I understand that...
  16. Roy Holmes

    Prop wash ruins the entire ground handling in MSFS

    The program is full of mistakes. I do not fly props but the single stage turbojet I'm working on has 99% N1 and 50% N2. It has the correct N1 to N2 data entry but that seems to be ignored. If the airplane is moving with the throttle shut idle RPM is 70% which means you cannot slow down in the...
  17. Roy Holmes

    Descent and Negative TSFC

    When cruising at constant altitude your energy comes from fuel being burnt and turned into thrust, so TSFC means something. When you climb you have an additional call on the fuel burn to generate potential energy. When you descend your fuel consumption is reduced because you use stored potential...
  18. Roy Holmes

    Some doubts on Table 1506

    1506 input is CN1 and Mach number 1506 output is thrust scalar versus CN1 and Mach There is no real value of thrust and no value of weight involved in constructing 1506, the table outputs are scalars that apply to any engine irrespective of its actual thrust. A figure of 1.0 as a scalar in the...
  19. Roy Holmes

    Some doubts on Table 1506

    There is something odd about that data. It suggests that for a constant 82.5% CN1 you have a wide range of corrected fuel flow. If that is the case it is dealing with a very large range of atmospheric variation, not a standard atmosphere. The whole point about corrected values is that you get...
  20. Roy Holmes

    Some doubts on Table 1506

    For a constant flight condition, same Mach, altitude and CN1 or N1 thrust is equal to drag. Drag is made up of form drag and induced drag. Form drag is constant because speed is constant, but induced drag varies with angle of attack which is a function of lift. As weight reduces so does the...
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