278 AIRCRAFT ENGINEERING October, 1929 Magnetic Compasses with Remote Control Detail s of an Important Contribution to the Science of Aerial Navigation by a Leading German Firm By Dipl.-Ing. Friedrich Hauptmann 3 . Greatest Magnetic Correction Factor.—The many H E basis of all navigation is the compass. covered. The necessary air is delivered by means flights which have already been carried out with I t will therefore be readily understood that of a small air motor, placed in any convenient thi s apparatu s go t o prove tha t the magnetic correc for years th e greatest efforts have been made position on the fuselage, a reducing valve in the maste r compass bringing down the induced draught tio n factor of the master compass is very good, to improve the compass, to make it come up to all t o a constant pressure. With the course setter an d tha t the accuracy of the compass, owing to its th e requirements of flight. Unfortunately, this is th e housing of the mother compass over the flexible favourable position in the rear of the fueselage, only possible by means of a compromise, because th e qualities required in a good compass, as far as shaft is turned, together with the nozzles which is of a high order. construction is concerned, tend to contradict one ar e attached to the housing. The course setter 4. Good "Damping."—As far as "damping" another . These desiderata are: — an d nozzles are turned until both of them are is concerned, a new path has been opened up with equall y covered by the eccentric disc—that is, until thi s compass. It should be pointed out that this 1. Extreme legibility. th e course indicator shows "nil. " is not a "wet " compass, but a "dry " one, whose 2 . Light weight and small bulk. dampin g can be arranged by electro-dynamic I n practice, the apparatu s is used as follows:— 3 . Big magnetic correction factor. methods , since its system swings between two copper Th e pre-arranged course is fixed on the course 4 . Good "damping." plates . setter , and the pilot flies so that the indicator 5. Rest—i.e., after deflection, quickest possible alway s shows "Nil. " If he deviates to the left of 5. Rest is th e result of the electro-dynamic damp retur n to rest. his course, the indicator will swing to the left and ing, with correspondingly short swinging period. vice versa. Seven Desiderata.—For the Askania Compass it is claimed that the seven desiderata postulated are fulfilled in the following manner:— 1. Legibility.—This can be increased at will—it is only dependable on the sensitivity of the pressure gauge, or course indicator. The Askania Works in Berlin supply wit h this apparatus a course indicator which shows a deflection of about 15 mm. for a deviatio n of 5° from the set course. In the case of a n ordinary pointer compass, to indicate a 5° devia tion by a 15 mm . deflection, the pointer would need t o be arranged with a diameter of about 350 mm. Thi s is one essential advantage of the magnetic distan t drive compass. In constructing this pneu mati c drive it is possible to get any degree of legibility, while retaining small size in the needle system . 2 . Small weight and small size. 6. Position must be easily readable from pilot's Weight. Size. seat. Compass 1·3 kg. .. Diameter, 140 mm., height 165 mm . 7. Most favourable position magnetically. Course setter, 0·500 Diameter, 110 mm., depth Fro m th e foregoing it will be noticed tha t Items 1 kg . 85 mm . an d 2 are contradictory, because if the compass is Course indicator, Height, 36 mm., breadth, 124 t o be read accurately, the dial must be large, and 0·50 0 kg. mm., depth 138 mm . th e compass will be heavy, and take up a lot of room. Again, points 6 and 7 contradict each other . The pilot's seat in most machines is, mag 6. Fitting so as to be easily read from Pilot's Seat.— netically speaking, the most unfavourably possible As already mentioned, only the course indicator position, because of the engine, starter, and all need be fitted near the pilot's seat (see Fig. 3, the other metal and electrical objects in its imme showing the large instrument panel), and this pro diat e neighbourhood, all tending to influence the vides an ideal magnetically influenced instrument compass to its detriment. for course flights. A solution is offered by the magnetic distant 7. Magnetically favourable fitting is achieved by drive compass. As can be seen from the illustra selecting the least magnetically influenced position tions, it consists of three parts: — on the machine, for placing the master compass Th e compass itself, called the master compass, ou t of sight and out of reach of th e flight-personnel. Th e course setter, and A further advantage, by no means negligible, is The course indicator. th e arrangement of the apparatus from the point of Th e master compass is generally mounted in the view of navigational control. The separation of rear part of the fuselage, which is magnetically the th e master compass, course setter and course most favourable position in the machine. The indicator provides th e simplest method of co-opera course indicator is fitted in a position easily seen tion between pilot and observer, and at the same b y the pilot, and is connected by two simple air tim e saves the already busy pilot the work of pipe-lines to the master compass. The course readin g his compass. If the observer requires sette r is fixed near the navigator—or should no a n alteration of course, he turns the course setter special navigator be carried on the machine within unti l the new course is set. The course indicator easy vision of the pilot—and is connected by a flexi- will naturally show left or right of "Nil," as the ble drive to the master compass. case may be, and the pilot, who only need attend Th e method of working this apparatus can be t o the course indicator, alters the direction of the seen from the drawing (Fig. 2). The magnet itself machin e until the pointer again reads "Nil, " that does not carry a pointer, but a small eccentric disc. is t o say, until th e machine is lyin g on her new course, Thi s controls two opposed nozzles in such a way as set by the course setter. tha t normally both nozzles are covered by the disc. Th e Askania Compass has already been tested on If the magnetic needle deviates, then one nozzle man y flights, amongst which may be mentioned the is covered somewhat more, and the other corre crossing of the Atlantic from East to West, by spondingly less, by the disc. A pressure gauge, Köhl, Hünefeld and Fitzmaurice. The Deutsche th e course indicator, connected with both these Luft Hansa has also used the pneumatic compass nozzles then shows a deflection. This indicator on the Berlin-Konigsberg night service for more should read "nil " when both nozzles are equally tha n 275 flying hours with satisfactory results.
Aircraft Engineering and Aerospace Technology – Emerald Publishing
Published: Aug 1, 1929
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