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Aviation History
1962
1962 - 0297.PDF
FLIGHT International, 22 February 1962 299 FLIGHT SYSTEMS the control wheel temporarily disengages the autopilot, which then takes over again to right the aircraft when the manual manoeuvre is completed. Joy-stick autopilot controllers for one-handed control of pitch and turn are being tried. GILFILLAN BROTHERS THE glide-path and ranging portions of Gilfillan Regal, designed as a "common system" landing aid, were set up at FAA's Atlantic City Experimental establishment in March 1960 and a good deal of ground and flight testing have proved at least the basic operating principles. Ground vehicles and several types of aircraft have been used, and at least 60 successful automatic landings have been made. Regal employs a pair of vertical aerials which form an interference null marking centre of a beam effectively 0.05° wide. The aerials nod to sweep the beam and are energized only during the downward scan to avoid ground clutter. Range signals are derived by DME interrogator responder techniques on a time-shared basis. Elevation angle is indicated by beam coding so that the angle and range are derived by the airborne equipment and used as appropriate to the autopilot. Localizer guidance would be provided by an equivalent horizontal aerial system, but because the azimuth element may not be needed for some time in view of ILS localizer improvements, only the elevation portion is at present under test. Gilfillan propose a "full-scale" system with all safety provisions and 12° vertical and 30 mile range capability for transport use. Range can be extended to 80 miles for full guidance of high- performance aircraft. For helicopters or STOL aircraft a version for up to 30° glide-slopes is offered. A lightweight, portable version, each element weighing 2,0001b, is proposed for tactical use, and a 4001b version of reduced angular accuracy and data rate is offered for field use. Various degrees of approach or landing performance can be had, according to the airborne equipment used. Measurements have shown coverage corresponding to minimum elevation angle of 0.25° from the ground beneath the aerial (upper limit is thought to be 19.5°) and range coverage to 18 miles in clear weather and at least ten miles in rain. Azimuth coverage of the elevation system has been found at ±45° from the centre line. An elevation angle accuracy of ±0.05° has been statistically shown. Receiver instability has made range accuracy measurements diffi cult but ± 100ft is estimated in the touch-down area. Interference from caravans 1,000ft in front of the aerial was minor in some areas. Aircraft or trucks 400ft in front caused significant inter ference, but Regal is considered "definitely compatible with typical airport environments." Four types of aircraft have been fitted for Regal trials and a fifth is being equipped. First was the FAA C-54G with Sperry A-12 autopilot, Sperry variable fixed-path flare computer giving glide- path lock-on, automatic throttle-back and decrabbing, Sperry autothrottle, Regal receiver-decoder and co-ordinate converter, Collins FD-105 flight director coupled to the flare computer, Regal range dial and a facility for selecting glide-slopes from 1° to 5°. Ten "smooth and repeatable" automatic landings were made last month. An Aero Commander was fitted with Lear L-5B autopilot (modi fied for close pitch control, decrabbing and "beeped" pitch trim), Sierra Research continuous recomputing flare-out computer, a USAF flight director, Regal altitude-distance readout and Regal receiver without co-ordinate converter. More than 100 automatic approaches have been made, 50 of them with automatic touch-down. The suitability of Regal for small aircraft and for this type of autopilot and flare computer have been demonstrated. A USAF C-131 has been equipped by Sperry Phoenix as a typical military transport. The installation was relatively experimental and included a Sperry recomputing flare computer with automatic decrabbing, a USAF flight director and Regal receiver and co ordinate converter. Little work has been done with this type, but 50 manual approaches, 13 of them ending in touch-downs have been completed. A more operational autopilot is to be installed. The 161b, transistorized airborne receiver for Gilfillan Regal Bendix Eclipse-Pioneer have fitted two B-25s for Regal landings with two different recomputing flare computers for USAF/FAA evaluation. Accelerometer augmentation of Regal rate of descent information and a triple tape instrument showing height, height rate and range to touch-down have been tried. Flight tests began in 1960 and several of the" automatic approaches have culminated in automatic touch-downs. A USAF T-33 is being fitted with more compact equipment for manual or automatic Regal landings. A continuously recomputing flare computer is being developed by Lear Astronics. Computer studies recently completed indicate that this system and Regal will give a touch-down spread of ±200ft with a sink rate of 2±lft/sec, 16ft Regal glide-slope aerials, which scan at 2.5 cycles/sec Qm
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