FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1947
1947 - 1489.PDF
SEPTEMBER 4TH, 1947 FLIGHT 249 Marathon loads are taken as shear by bolts attaching the lower contour member of the root rib to the fuselage. The rear spar has a continuous top boom member which spans the fuselage, and picking-up to this on the centre line is a fore-and-aft bolt which acts as a shear member in taking the cross component of the drag loads. Wing ribs are light, built-up, strut-braced members which are pitched fairly close to- gether, those abaft the rear spar having a curved lower profile to ac- commodate the flap shroud. The outer wing panels are attached to the centre-section immediately out- board of the outer engines, the main spar joint being made with fork- and-lug pin-jointed straps to the booms, whilst the light rear spars are pin-join ted through fish plates. Fuel tank capacity is broken up into four units, two in each wing totalling 120 gallons per side ; the tanks are crash-proof, flexible, bag-type cells. Whilst on the subject, we may mention that the original fuel system was laid out so that each engine was served by its own fuel tank, it having been theoretically established that with one engine out the remaining three engines would, on their own supply, give 85 per cent of the range otherwise available by using the dead engine's fuel. On ranges of the Marathon order this loss was considered negligible compared with the saving The centre section I outer- panel wing joints are made at the main spar (left) with pin - jointed boom straps, and at the rear spar (right) with re- inforced fish-plates. of complication and the potential dangers inherent in complicated fuel systems. However, certain operators insist upon haling cross-feeds as between the inner and outer engines of each wing, although there is no cross-feed as between the port and starboard installations and thus no fuel line near the fuselage. The inboard nacelles are hung from the main spar and 110m doubled nose ribs and the rear spar, whilst the out- hoard units do not pick-up the main spar; the engine mountings are quite conventional and such as to provide ready access for servicing. Actuating gear for the high-lift/low-drag flaps is housed in the tails of the nacelles, the flap reaction loads being taken solely through the nacelle structure; each flap is supported at its inner and outer ends by simple guide rails which resist lateral bending. It is worth noting that the Marathon is the only British four-engined commercial air- <raft fitted with high-lift/low-drag flaps. The fuselage is dome-head riveted, as are the wings, with the exception of the first 30 per cent chord where the rivets are flush. Fuselage skin panels vary between 20 and 24 yftuge; wing skins vary between 16 and 24 gauge, and tail surfaces between 20 and 26 gauge. At the rear of the fuselage the top is cut away to accom- The overhung nosewheel (above) can be steered or freely-castoring at will. The main landing wheels (right) are lever-mounted on forward-retracting breaker struts. modate the tailplane, the cut-out being covered with flat decking. Tailplane spars pick up in pin-joint fashion to reinforced semi-frames at the respective stations, the rear- ward of which takes the main loads. The rudders use a horn-type aerodynamic balance in conjunction with nose mass-balancing, but elevators have no nose balance so the mass-balance weights are externally carried on lever arms. The same thing applies to the ailerons. The undercarriage is of Miles design throughout and employs the maker's own oleo-pneumatic shock absorber units, the main undercarriage wheel mounting being o$the type now known as levered suspension. A useful feature in connection with the undercarriage is that taxying lights are fitted to each main leg, this scheme having, we believe, been experimentally proven in the R.A.F. during the war. The nose wheel can be used either in free-castering self-centring form or, by engaging a mechanical linkage, can be steered by actuation of the rudder pedals. In the air the Marathon exhibits very pleasant charac- teristics ; take-off is remarkably short and the general noise level in the cabin pleasantly low. The fact, however, that the exhaust pipes of the Gipsy Queen engines emerge on the starboard side of each nacelle makes the port side of the cabin noticeably noisier than the starboard. Despite the fact that most operators would prefer maximum inter- changeability of engines to the attainment of minimum noise level, it would be worth while considering a modification to the port inner engine exhaust to eliminate this drawback. Briefly, the Marathon should supply qualities which are ever increasingly demanded, namely, speed and economy without sacrifice of safety. MARATHON DATA Four de Havilland Gipsy Queen 71 Engines of 330 b.h.p. Driving 7ft 6in dia. 3-blzde D.H. c.i. feathering airscrew* Span 65ft Length 52ft lin Height I3fc- 9in Wing area, gross ... 500 sq ft Aspect ratio Flaps area per win^ Gross weight Wing loading Cabin volume M»x. speed, at 6,3COft Mix. cont. cruise, at lO.COCft ... Recomm. econ. cruise, at lO.OCO't Max. still air range Distance to clear 50ft Initial rate of cfimb Initial rate of climb, three engines 8.5 32.8 sq ft 16,550 Ib 33 Ib/sq ft 760 cu ft 230 m.p.h. 210 m.p.h. 175 m.p.h. 900 miles 815 yds I.125ft/min 650ft/min
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
