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Aviation History
1939
1939 - 0821.PDF
MARCH 23, 1939 FLIGHT. a Commercial Aviation ASSISTING THE BLIND APPROACH A Sensitive Rate-of-climb Indicator Described : The Cobb-Slater Variometer UNTIL suph a time as radio engineers develop a reliable means by which an approach descent can be regulated, pilots will continue to depend on the indications of a sensitive altimeter when making a blind approach to a terminal airport. In difficult conditions the rate-of-climb indicator, or variometer as the sailplane people describe it, could be extremely useful were it not for the fact that the normal instrument of this type suffers considerably from lag. What is claimed to be a lagless variometer has recently been produced as a direct development of the instrument which is used in sailplanes, wherein immediate and very accurate indications of up-currents and down-currents are most im portant. As designed for aeroplane use this variometer, the ' Cobb-Slater, consists of a vertical block of transparent material with two finely tapered holes bored vertically, each tube con taining a small spherical piston. One of these pistons is coloured green to indicate ascent, and the other coloured red to indicate descent, the rates in each case being shown on a scale between the tubes. A small lever at the base of the instrument controls a damper for use in bumpy conditions. The tubes are connected to a reservoir of air contained in two vacuum flasks. The old type of instrument, operated by a diaphragm and embodying a fixed leak, suffers from considerable drag as well as loss in the transmission of the motion from the diaphragm to the indicator. With a fixed leak, too, inaccuracies must occur over a wide range as, in order to produce sensitivity, a very fine leak is required. Strict accuracy in such instances is only to be obtained if the degree of leak varies directly with the rate of change in ascent or descent. A Cavalier Claim OF considerable legal interest is the filing of a suit against Imperial Airways (Bermuda), Ltd., by the widow of one of the passengers who lost his life in the accident to Cavalier in January. Mrs. K. Miller, who was herself one of the ten rescued passengers, is claiming damages to the extent of £40,000 on the allegation of negligence and misconduct on the part of the brew Reform, in Australia IN a report which has recently been discussed by the Australian Federal Cabinet the "reform" of Australian commercial aviation is being strongly urged. This report is the work of an inter-departmental committee which was set up recently by Mr. Thorby in respftnse to criticism. Its recommendations include an increase in subsidy of £100,000, bringing the total to more than £400,000; the speed ing-up of time-tables over certain routes; and the rationalisa tion of the services to eliminate overlapping. It is pointed out in connection with the latter, for instance, that two highly subsidised companies are operating against an unsubsidised organisation between Sydney and Townsville (Queensland); these two subsidised companies are, in fact, Qantas Empire Airways and W. R. Carpenter, while the unsubsidised services are operated by Airlines of Australia. There is also a duplica tion of the Sydney-Melbourne route, both Australian National Airways and Ansett Airways running services. A recent attempt by A.N.A. to buy out Ansett resulted in a deadlock. Scandinavian Additions HTHE Scandinavian air transport network is being consider- •*• ably expanded this year. The Copenhagen-London ser vice, operated by D.D.L., for instance, will be extended to Oslo, the Condors being run through from Copenhagen, via Gothenburg and Kristianssand, and this service will be main- rained all the year round. Passengers from Oslo will be able to reach London in less than 6 hours after June 1, when the new schedule is started. An additional through service will be run by D.N.L., using a chartered Douglas D.C.2, from Oslo, via Kristianssand and Amsterdam, to London. D.D.L. will also run a new service from Kristianssand, via Aalborg, to Copenhagen as from line 1, with a new connection to Hamburg. The ordinary Oslo-Gothenburg-Copenhagen service will be operated by land- planes and also maintained throughout the year. One of the Norwegian Army's new Capronis has been chartered for the night-mail feeder service between Oslo and Gothenburg which starts on April 18. In Norway, Ju.52 seaplanes will, as before, operate the Oslo- In the Cobb-Slater variometer the slightest movement of air through the outer tube is registered by the indicator piston, which takes up a position in the tube where the airflow corre sponds to the rate of rise or fall; the leakage of air past the in dicator is thus automatically and constantly adjusting itself to the variations. When the indicators are both at zero they seat on valve faces. It is this last feature which makes the instrument very sensitive and ensures almost complete absence of lag. When one indicator is showing a maximum rating the leak is such that no pressure is built up in the reservoir, while at rates of ascent or descent greater than the maximum a bypass comes into action to relieve any tendency towards the building- up of pressure. With fixed leak instruments this pressure- building tendency in the reservoir at high readings is marked, with a consequently high degree of lag. This type of variometer has the additional advantage of simplicity. A number of sensitive variometers have been evolved in the past, but only at the expense of durability. Since there is no mechanism, in the true sense, in the Cobb- Slater device, it should be virtually indestructible. The type at present in production for aeroplane use covers a rate of change between plus or minus fifteen hundred feet per minute, the lowest graduation being 50 ft./min. This graduation is fin. from the zero mark, so that, for blind- approach use, rates as low as 20 ft./min. can be gauged. The Cobb-Slater variometer, which has been tested through out the winter by Air Dispatch on their Paris newspaper ser vice, has been made by Mr. R. B. Cobb, of Matlock. En quiries are being handled by Mr. F. W. Griffiths, Air Couriers, Ltd., Airport of London, Croydon, Surrey. Kristianssand-Stavanger-Haugesund-Bergen daily service, while a daily service will also be run between Bergen and Kirkenes, and a semi-daily service between Bergen, Kirkenes and TromsO. An application from the private company, Wessels, Flyselskap, to open and operate a new direct service between Oslo and Stockholm, using an 8-seater Caproni landplane, has been refused by the Norwegian Government on the ground that safety required the use of seaplanes. An agreement, as already stated, has been made between Aeroflot and A.B. Aerotransport to resume operation of the Stockholm-Riga-Moscow service, the period being increased from 3 to 6 months. The service opens on May 3 and will be kept going until November 4. The schedule is arranged to connect with Aerotransport's Stockholm-Amsterdam ser vice, which means that the Moscow-London journey may be made in one day. Aerotransport, as well as D.N.L., are both concerned with new Polish expansion schemes. A direct ser vice may be run between Warsaw and Stockholm, and another service from Warsaw via Gdynia and Ronne (isle of Born- holm, Denmark) to Copenhagen. The Finnish company, Aero, has decided to regularise the experimental Helsinki-Balticum-Berlin service, and intends to add a third daily schedule on the Helsinki-Stockholm run when the company's new F.W. Condor has been delivered. The internal Finnish lines, Helsinki-Tammerfors and Helsinki- Viborg, will be operated daily from May 1 to August 31, and an additional service will be run from Tammerfors, via Vasa- Uleaborg to Kemi between June 15 and August 15. A sub- Arctic airline is being planned to connect Rovaniemi with Lappland. A machine fitted with skis started experimental flights at the beginning of this month. Other forthcoming additions now being considered are a service between Immola and Willmanstrand, and a service from Viborg, via Sordavala, to Joensuu. Reorganisation in Italy CONSIDERABLE changes are being made in the internal and external air service network of Ala Littoria and Avio Linee Italiane. The former is to extend its Rome-Haifa service (as already announced in Flight) to Baghdad and Basrah, and the Rome-Bucharest line to Constance. New services will be started linking Milan and Budapest, via Vienna, and Brindisi with Bari. The present Venice-Prague service will be sub stituted by one calling at Trieste and Bratislava. Avio Linee will no longer fly through to Bucharest on the Turin-Belgrade service, and will make new runs between Turin and Marseilles, Milan and Brussels, and Rome, Budapest, Warsaw and Gdynia. The seasonal internal air lines will also be increased in number. Most of the changes will be made on April 16.
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