FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1946
1946 - 2161.PDF
OCTOBER 31ST, 1946 FLIGHT 465 COURSE INDICATOR. \ dead-beat characteristics of thedirectional gyro, but is always . showing an actual magnetic course.An indicator tells the pilot that the gyro is correctly showing themagnetic heading and not merely behaving, through electrical failure,as a simple gyro. In the American version of theGyrosyn, this and the repeaters have a fixed compass card with amoving pointer and a '' tramline course-setter. The British type willhave a moving card and a fixed '' aircraft'' somewhat similar tothat used in an artificial horizon. Every effort has been made in the3'Lnstiument to make the actions of course holding and course-chang-ing by the pilot absolutely natural. This new dial form is shown in theaccompanying drawing. A further development is that of a specialnavigator's repeater with a six-inch dial showing individual degrees andwith a magnetic variation adjust- ment. When the navigator sets thenecessary local variation on the in- strument—in the same way as themillibar figures are set on a sensi- tive altimeter—the indication is #adjusted on all the repeaters to give a true course. Amplification But to return to the A. 12 automatic pilot itself. Once the electrically driven gyros for the various axes have provided their displacement signals, these must he increased sufficiently to provide the neces- sary control-operating power. This work is done by a flight amplifier which not only increases the strength of the signal, but adds a rate factor to the displace- ment signals. Other amplifiers, all in the same assembly, operate the compass, the turn and the alti- tude controls. Accessible outside the amplifier box are the adjustments provided for calibration to suit the characteristics and the control forces of each particular aircraft. These adjustments would be made during the flight tests after installation. No later re- setting is necessary for different conditions of weather. From the amplifier the power is taken to the servo control unit, which steps up its strength to oper- ate the servos. This unit is simply a D.C. motor driving three genera- tors to supply the power for the servo units operating the ailerons, rudder and elevators. These servos can be incorporated where most convenient in the nor- • jtnal control-cable runs, the cables 10*. oeing wound in each case around a drum which is driven by an electric- motor through a positive clutch. The main engagement levers, which may be operated separately or to- gether, control these clutches, and when not engaged the drums turn freely. The whole operation is strongly spring-loaded, so that there is no possibility of partial engage- ment or disengagement. In the case of the elevator trim-tab servo, this is engaged through a friction clutch only when the main elevator servo control is also engaged, and it is possible to overpower it. It is obvious that in any aircraft which are intended already to HEADING 'ICATOR LOCK &. SET CONTROL The British version of the Gyrosyn com-pass dial which has been designed so that all corrective' actions are natural. employ control servos, the installa-tion of a pilot of this type can con- veniently go hand in hand withcontrol layout development. Inci- dentally, the weight of the A. 12equipment is in the region of 120 1b. There are quite a number of laterapplications for such an automatic pilot, in addition to its normalfunctions. Work has been com- pleted in America on the develop-ment of an automatic approach system whereby the beam signalsas indicated on 'the cross-pointer dial are used to control the coursewhile the glide path is held con- stant, so that only the air speedwill remain to be regulated by the pilot. A further development isthat of automatic air-speed control, by which the throttles themselvesare moved to hold a constant speed during the approach. The routine for making an auto- matic approach—for which either a Sperry Microwave or the SCS.51 system can be used—is compara- tively simple. When the aircraft has been cleared for landing by airfield control, the undercarriage and flaps are lowered and speed reduced to that required on the final approach. The auto- matic pilot is set to give approximately a z\ deg glide angle, but the altitude control holds the aircraft level until the approach is to be started. The aircraft is flown to a posi- tion at which the localizer beam can be intercepted at an angle of 45 deg, and in a position sufficiently far out for the aircraft to be well below the glide path. The cross- pointer needle will thus be showing full upward deflection. Meanwhile the directional needle will be indicating full horizontal deflection. As soon as this has moved towards the centre of the instrument, the automatic approach con- trol is engaged so that its signals are fed to the automatic pilot. During this time a constant altitude has been retained, but as the glide-path needle also reaches its central position, the approach control is set to "connect" the automatic pilot to the glide-path signals, and the altitude control is then automatically switched off. Since the auto- matic pilot has already been adjusted to give a 2^ deg glide- angle, this is held unless the glide- path signals cause a correction. The A. 12 is, one understands, likely to be built in this country and, alongside other developments of our own, may have considerable influence on future aircraft control design and layout—particularly on large transports. The next move will be that of producing a version suitable for feeder-line types, for which the need for automatic con- trol assistance must be almost as great in bad weather conditions. The special navigator's master indicator dialc n which the magnetic variation can be set, this variation being then applied to theindications of ths instrument and of the repsaters. LESSONS FROM BIRDS SOME 2^0 people, including a num-ber of senior executives of the Fairey Aviation Co., Ltd., attendedthe lecture given by Capt. J. Laurence Pritchard, secretary of the R.Ae.S., atthe Fairey canteen on Oct. 17th. The lecture, one in the seriesarranged by Aerotech Flying Club No. 1, was entitled '' Bird Life and theAeroplane" and in it Capt. Pritchard had marshalled considerable evidenceIn show that man has much to learn from nature in the matter of flying.The next lecture, is on Nov. 7th.
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
