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Hello to all:

I am building a real hardware of an autopilot panel of a 747-200. This panel has a selection of "IAS HOLD" that maintains the airspeed "IAS" constant, varying the RATE of CLIMB to maintain the IAS constant. This is made to constant thrust power of the engines. I was proving with the variable of the FSUIPC $3460 but I don't achieve him to work. Can somebody help me???. Can I use another variable to do this?? Thanks.

Jose

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I am building a real hardware of an autopilot panel of a 747-200. This panel has a selection of "IAS HOLD" that maintains the airspeed "IAS" constant, varying the RATE of CLIMB to maintain the IAS constant. This is made to constant thrust power of the engines. I was proving with the variable of the FSUIPC $3460 but I don't achieve him to work.

None of the variables in the 2nd table of the programmers guide should be used if there's an alternative method -- because they were found and mapped "by fluke" in FS2000 and cannot be guaranteed in anything later. I state this at the head of that table I think.

That particular offset (3460) is clearly marked as NOT supported for FS2002 (see the "No" in the rightmost column?).

It isn't needed in any case. ALL the autopilot controls and read-outs are mapped in their FS98 compatible places, 07BC through to 0810. I'm surprised you even wanted to look further afield! The airspeed value is at 07E2. Of course you also need the autothrottle armed (0810) and the airspeed hold selected (07DC).

If you have difficulty finding things, try using your viewer's search function. It would be nice to have an index, I know, but there's not enough hours in the day!

Regards,

Pete

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Hi Pete:

thanks for your help. My questions is:

You write: "It isn't needed in any case. ALL the autopilot controls and read-outs are mapped in their FS98 compatible places, 07BC through to 0810. I'm surprised you even wanted to look further afield! The airspeed value is at 07E2. Of course you also need the autothrottle armed (0810) and the airspeed hold selected (07DC)."

I need to control the IAS varying the rate of climb with autothrottle at climb power (constant power). If I use 07E2, 0810 and 07DC, the IAS is controlled by the thottle not by the pitch. Thank you very much.

Jose

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I need to control the IAS varying the rate of climb with autothrottle at climb power (constant power). If I use 07E2, 0810 and 07DC, the IAS is controlled by the thottle not by the pitch. Thank you very much.

You vary the vertical speed (07F2), part of autopilot I told you about, to control the pitch, monitoring the IAS and adjusting V/S accordingly. How else do you think it can be done?

You said you were trying to use offset 3460 (AUTOPILOT AIRSPEED HOLD CURRENT, not supported) which would have been only the autothrottle airspeed setting -- the same as the one at 07E2, as I clearly pointed out.

The A/T does not control pitch, it controls throttle -- if you set too high a climb rate the A/T will fail to reach its set IAS. If you dive then the A/T cannot hope to reduce speed unless you assist with speed brakes.

If you are programming your own A/P then do it by use of elevator, aileron and throttle inputs. If you want to use the FS one you have to use the controls provided. The only one controlling pitch in altitude acquisition is the vertical speed value.

You should really be able to control this by setting "Vertical Speed Hold", but the way the FS A/P is written I think you have to set Altitude Hold mode and set a target altitude (which you can keep changing of course -- or set 65000 feet for climb, 0 feet for descent).

Regards,

Pete

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