FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1941
1941 - 1186.PDF
364 MAY 22ND, 1941. THE BELL CARIBOU Latest Information on this Ultra-modern American Fighter THREE CARIBOUS ON AN AMERICAN AERODROME : The Bell Caribou, known on the other side of the Atlantic as the''Airacobra, is one of the fighters which the United States will supply to Britain under the Lease-Lend Act. Its enterprisingly;; modern design has proved to be a success. ' THE Bell Caribou single-seat fighter, one of ouracquisitions under the American Lease and LendAct, should be seen in British skies this summer, and with its fierce armament will doubtless take toll of the enemy attackers. The Caribou, known in the United States as the Airacobra, is designed to an ultra-modern formula and gives promise of being most successful. It is notable for two outstanding features: the nosewheel. undercarriage, and the placing of the engine behind the pilot with a long shaft driving the tractor airscrew. Though there is not yet in service a British military aeroplane with a nosewheel undercarriage—the General Aircraft Cygnet and Owlet being the only examples in this -country of such enterprise in design—this type of undercarriage has been adopted enthusiastically in the United States. Its advan- tages are: shorter take-off, prevention of bouncing on land- ing, directional stability on the ground in a cross wind, and reduction of landing run by allowing more vigorous use of brakes. The nosewheel undercarriage has established itself beyond doubt, but its combination with transmission shaft is an interesting (departure from orthodoxy. Shaft-driven Airscrew Transmission of the engine power to the airscrew through a long shaft is not such a well-established engineering design, though it is probably no more difficult a problem than a successful nosewheel undercarriage. The main prob- lem involved is so to design the shaft that the engine-shaft- airscrew combination will not have vibration frequencies which could become dangerous and perhaps cause the failure of any one or all of these components. The Bell Company, however, has been able to deal with what is a very difficult technical problem, involving most abstruse mathematics and requiring exhaustive mechanical testing. For the Caribou has been built and flown for a considerable period and is the second of the Bell Company's productions with extension shafts^ The Airacuda, a twin-engined monoplane with the airscrews set behind the trailing edge, was the first. We are able to give some particulars of the Caribou by courtesy of Canadian Aviation. The fuselage is built on two longitudinal beams and the Allison V-12 engine is attached to these. The airscrew drive shaft is carried on inter- mediate supports and is stated to have '' universal joint action." The reduction gear box is attached to the front end of the fuselage longitudinal beams and the airscrew is driven from this. The fuselage beams attach at the rear to the monocoque fuselage and the structure of the pilot's cockpit, seat and- flying controls is also carried on these beams. The wing construction- is stressed-skin with two main spars, and these connect to the beams of the fuselage, where they pass through it. The spars are built of aluminium alloy extrusions, and the wings contain the fuel tanks. In the cockpit (which is, as would be expected, of just sufficient size for the pilot) the flight and engine instru- ments are grouped on two narrow panels at eye and chest level respectively. Such items as flap and undercarriage indicators and engine switches, gun switches and gun- charging levers, are on panels at each side of the main instrument board. Near the throttle lever on the left side is a folding arm rest. Brake application is by toe on the rudder bar. In addition to the indicators on the instru- ment board, a yellow knob emerges from the upper surface of each wing and from the fuselage nose when the under- carriage is stowed in the " up " position. The radio equip- ment is fitted neatly into a small panel below the engine instrument board and also between the pilot's ankles. The pilot's view is said to be unusually good. The landing gear is so designed that when at rest on the ground the thrust-line of the Caribou is at an angle of 5 deg. to the horizontal. At the take-off speed of 90 m.p.h. the angle of incidence with all three wheels on the ground is such that the lift is just equal to the weight; in other words, all three wheels leave the ground simul- taneously. It has also been arranged that, if landing off a 75 m.p.h. glide, the nose and main wheels touch sirnul- taneously. The nosewheel is not steerable, but has^ hydraulic stabiliser built in to prevent "shimmy." What armament will be fitted in the Caribou for use by the Royal Air Force is obviously a closely kept secret, but it will be heavy. There is plenty of opportunity to install heavier armament than we have yet seen in action against the Luftwaffe for, as well as guns in the wings, the absence of the engine in the fuselage nose provides plenty of space there. The airscrew hub is hollow and it is very likely that this will mount a shell-gun, perhaps a 37 mm. type. For the rest, we can only speculate as to whether it will be six heavy calibre (0.50m.) machine guns or four 20 mm. shell- guns and two machine guns. It may be significant that a big American factory has been built to produce these 0.50 machine guns, which are a big increase in weight over the 0.303 gun at present in wide use. Latest technical information on the Bell Caribou is as follows: Engine: Allison V-12 liquid-cooled of 1,150 h.p. maximum .'i'f' screw diameter: 124.5 in- Wing loading: 34.6 lb./sq. ft. F''**'loading: 6.4 Ib./h.fi. Wing area: 213 sq. ft. Span: ?4Jh Length: 29/f. cjn. Height: 9ft. 2i«. Weight, loaded: 7,379 ">•.Weight, empty: 5,347 Ib. Fuel capacity: 112 gals. Endurance- 2i hours' cruising.
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
