Modifying Boeing 747 roll control surface law


The lateral control of the Boeing 747 employs five spoiler panels, an inboard aileron between the inboard and outboard flaps, and an outboard aileron which operates with flaps down only on each wing. The five spoiler panels on each wing also operate symmetrically as speedbrakes in conjunction with the most inboard sixth spoiler panel. 

While X-plane simulator takes into account the control geometries, it does not simulate the control system accurately meaning that for all flight conditions and configurations, all lateral control surfaces are moving providing a non-realistic roll control response. In order to test the accuracy of X-plane lateral dynamics the aircraft had to be edited in Plane Maker and set the exact roll control surface law.

For the high speed case that was under consideration only the inboard ailerons (10 deg down and 20 deg up maximum deflection) and the outboard spoilers (40 deg maximum deflection) were set. This configuration provided a very good agreement to the state-space model of the airplane proving X-plane’s ability to accurately predict the roll-response for this type of aircraft. Exact results soon to be presented in a symposium.

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1 Response to Modifying Boeing 747 roll control surface law

  1. Jeffrey Chen says:

    Dear Sir,
    I am a developer for X-Plane’s 747-400 enhancement project. The original 747 flightmodel was extremely inaccurate in its control deflections, control blowdown, and control lockouts. We have fixed many many issues with the 747, from engine fuel consumption to the roll spoilers. After detailed research we found exact information of the angles of deflection for each of the six spoiler panels (some act as speedbrakes only, some only as roll spoilers, others as both, but also in varying degrees of motion). Contact me if you want the enhanced version of the 747, as I’m afraid any research you do on the default flightmodel will be very inaccurate. Believe me, the default flightmodel is nowhere close to actual performance.

    -Jeffrey Chen,

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