GB1349403A - Instrument flight system - Google Patents

Abstract

1349403 Aircraft control W W MELVIN 24 June 1971 29668/71 Headings B7G and B7W [Also in Division G3] An aircraft is controlled in the approach mode by correcting for displacement from a desired glide path by controlling the thrust level so as to bring both the said displacement and its rate of change to zero, and by simultaneously controlling the pitch of the aircraft to maintain a desired angle of attack. A thrust command computer 14 derives a signal representing the displacement L<SP>1</SP> as a function of the desired vertical bearing Q from the glide path origin, the deviation ## from this and the altitude L above the runway, and a shaping network (48), Fig. 6 (not shown), calculates a desired value of dh/dt proportional to the displacement; this is compared with the actual value of dh<SP>1</SP>/dt and the difference signal # displayed on a thrust command indicator 16 and/or used to control an automatic throttle. Thus a smooth return to the glide path is ensured since # tends to zero with L<SP>1</SP>. Likewise in pitch command computer 11 the pitch angle #, glide path angle γ and desired angle of attack α d are used to derive a signal # representing the difference between a desired value of dα/dt proportional to the deviation and the actual value of dα<SP>1</SP>/dt, and this is displayed on pitch command indicator 12 and/or fed to the automatic pilot. Different modes of operation may be chosen by means of selector 22. In override mode a desired angle of attack may be selected manually; when not in this mode the angle of attack selector is driven by a servomotor to indicate the actual angle of attack so that there is a smooth transition when this mode is selected. In take-off mode there may be a timer providing a greater angle of attack for the initial portion of take-off. Other modes provide for cruise, altitude hold, maximum range and turbulence.