FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1949
1949 - 0114.PDF
FLIGHT January 2.0th, 1949 S O ARAB LEA IR ... the dive brakes according to the degree of failure. During the soaring season icing at these heights is unlikely. With this depth of soarable air the cloud streets properly come into their own; beautiful massive bands, stretching for miles, with a slightly beady structure to relieve the monotony. They seem to have developed a circulation of their own and steady lift is found along their flank, punctuated, here and there, by small areas of down-draught with improved lift in close attendance in which to circle and regain height. This is certainly the best depth of soarable air for thermal cross-country flights by the average pilot. I am not quite sure that it is not the best for all pilots when racing against time. It is certainly good enough for a gold " C " distance, and the only native one to date was done in it. Very different, not only in size but also in structure is the cloud picture presented by, let us say, a soarable layer 18,000 feet deep. The tall clouds have taken on the proper cunim shape. They extend well above the freezing level and precipitation takes place in the form of showers. The rhythm of vertical movement of air is vast, and there are wide gaps without thermals. The shower clouds tend to congregate in line squalls or cold fronts; this arrangement of the great amount of energy released by condensation tends to concentrate the strong .lifting power in narrow bands, and further enlarge the areas where no lift is met.. In the vicinity of these bands, strong downdraughts are encountered, and this wholesale churning of the air causes the wind to blow irregularly, both with regard to strength and direction. The suggested necessity to climb to three- quarters of the height of the soarable layer is therefore all the more imperative if dead areas are to be crossed. This involves protracted blind flying in clouds containing heavy rain, snow flakes and sometimes hail. Supercooled water appears to be omnipresent and icing of the airframe and pitot head a common occurrence. At low heights, below cloud base, itself varying much on either side of the average 3,500ft because of the redistribution of water by precipita- tion, the essential cloud structure hidden by the large grey pedestals of the cunims and the great number of low frag- ments cannot be discerned. It is true that clear areas are? found in the wake of cloud-bursts, but, in these, the lift is., mostly poor. It is only by climbing sufficiently high through a towering" cloud, and coming out into clear air through the side of it, that a more intelligible view is obtained. This arduous task must be repeated again and again in order to cover a - lot of ground. With the equipment at present available this is beyond the ability of the average soaring pilot. The; men who can fly thus are truly in the very top drawer of motorless flying. There is no better example of it than the flight which secured for Axel Persson the championship of the world at the F.A.I. Competition in Switzerland^ during which he climbed repeatedly to great heights whilst doing a goal flight from Samedan to Geneva. The attainment of the gold " C" conditions is, for men like Persson, only a matter of opportunity; given enough soarable air they will take it in their stride. But this achievement is well within the reach of lesser pilots. So far as the distance is concerned, I have already implied that 6,000ft of unstable air is sufficient; and for most people also best. In this country the limiting factor is that we are terribly cramped for space; and many a good flight has had to end because it had run out, not of thermal power, but of land. As for the height, if it is to be done by thermal soaring, difficult cloud flying is definitely involved. But there is a world of difference between steeling oneself for one grim ascent and purposely ploughing through a series of cunims, these buldozers of the sky. There again, to do the 10,000ft required, 11,000ft are sufficient and easier to cope with than 20,000ft; the accelerations are smaller and, with luck, icing might be avoided. A companion article by the same author will be published shortly. AMERICAN AIRSCREW ADVANCES Separate Self-contained Hydraulic System AN interesting .new development in airscrew technology has f~\ recently been announced by the Hamilton Standard Pro- A. JLpellers Division of "Oie 'United Aircraft Corporation. Whereas the conventional hydraulic airscrew is actuated by oil tapped from the lubrication system of the engine, and is thus limited to a. certain extent by the prior considerations of engine lubrication requirements, the new Hamilton Standard system comprises a separate and self-contained oil supply and acces- sory section unit for the airscrew. The integral oil control assembly, as it is officially known, embodies a complete accessory unit and a tank for the airscrew oil. It is designed for mounting behind the airscrew hub and concentrates all fundamental operating functions in one com- pact section; that is to say, the hydraulic pumps, constant-' speed governor, auxiliary motor for feathering and reversing, and the control valves, are all embodied in this single unit. Quite aside from considerations of installation convenience, this new departure, by permitting an oil supply separate from that of the engine, allows the use of a fluid primarily suitable for the airscrew itself. Furthermore, by employing larger capacity pumps and operating on lighter oil than previously possible, the assembly is stated to allow the use of airscrews having larger and wider blades for higher power absorption and greater thrust. These last factors can be assessed as being of some importance in meeting the high take-ofl and climb requirements of modern military transport aircraft and, in addition, there is some military advantage in that enemy damage either to the engine or the airscrew will not necessarily affect adversely the pilot'3 control of the other. The new assembly has passed U.S. Air Force and Navy type tests and performed satisfactorily during initial flight tests. Among aircraft on which it will be used are the Boeing C-97 Stratofreighter, Fairchild C-119 and R4Q Packets, Douglas C-124 Globemaster, Grumman SA-16, Chase C-123, and the Grumman JR25 Albatross. Hamilton Standard have also announced that they are sup- plying Hydromatic airscrews for the U.S. Navy's Martin carrier-based AM-i attack bomber. These airscrews are 14ft 6in diameter versions of the larger Hydromatics now inproduction for commercial and military transport type*. The four hollow-steel square-tipped blades have stronger cor^Bk tocope with the higher vibratory forces encountered in the tion of carrier-based aircraft.——, "" This annularc9»mg surrounds the airscrew tyrises the oil tank, c.s.u., • and valve units.
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
