Flight, March 1934

THE AIRPLANE DEVELOPMENT CORPORATION “V.I"

   THE "V.I." is the first machine to be produced by the Airplane Development Corporation of Glendale, California. This Corporation is a subsidiary of the Cord Corporation, of Chicago, which, with Mr. E. L. Cord as President, operates the Stinson Aircraft Corporation, Lycoming Motors, the Auburn Automobile Co., and several other engineering firms. About two years ago, when the demand for very fast transport aircraft was first heard in the U.S.A., Mr. Cord secured the services of Mr. Gerard Vultee, who for several years was chief engineer of the Lockheed Aircraft Co. Designed and constructed at the Grand Central Air Terminal at Glendale, California, the machine made its first test flights about a year ago, and recently ten machines of similar type were ordered by American Airways.
   The aircraft is an all-metal, single-engined, nine-seater, low-wing, cantilever monoplane, with retractable undercarriage. The wing, which is tapered both in plan form and thickness, is in three parts, the centre section, which is built integrally with the fuselage, and two outer sections which are bolted to the centre section. The structure of the wing is of the "shell" type, and is claimed to be very rigid in torsion. A smooth outer covering of Alclad sheet is attached to longitudinal corrugations which run the entire length of the wing. A removable panel on the under surface of the wing affords ready access to the interior for inspection and repair. Ailerons of high aspect ratio statically balanced about their hinge axis to eliminate flutter are fitted.
   The fuselage of metal monocoque structure is oval, having no longitudinal bracing. Alclad sheet covering is used, composed of overlapping riveted panels. As the panels are relatively short in proportion to the total length in the fuselage, it is not necessary to "form" the sheeting. It is possible to remove one or more of the panels from the fuselage by drilling out the rivets. These panels may be flattened out, and, using the flattened panel as a template, a new piece of sheet may be cut out and drilled. This operation can be performed by any reasonably skilled metal worker, and requires no special jigs or apparatus. All tail surfaces are of "shell" construction, the monoplane cantilever tail plane and the fin being built into the fuselage. Instead of an adjustable fin, a flap on the trailing edge of the rudder is used for trimming purposes. Similar flaps are fitted to the elevators and are operated by means of a lever in the pilot's cockpit. The provision of these small flaps eliminates the difficulty experienced in aircraft of this type in operating an adjustable tail plane at high speeds.
   The retractable undercarriage is a novel type of construction. The gear is operated by rotary motion about a pivot, the interior operating mechanism being merely a worm drive. An electric motor drive is operated by the pilot by a switch, and this lowers the undercarriage in about seven seconds. Emergency manual control, suitable warning devices and a pointer in the cockpit indicating the position of the landing gear at all times, are provided. The gear itself is composed of a single cantilever duralumin strut of rectangular section, to the upper end of which is fastened a segment of a worm wheel. The lower end of this box-like strut contains an oleo shock absorber unit to which a stub axle is attached. To this strut is fastened an automatically operated fairing which completely closes the wheel well and renders the bottom surface of the wing perfectly flush when the gear is retracted. A single cable runs from a suitable point on the landing gear back through the fuselage to the tail wheel. This cable partially retracts the tail wheel, as the undercarriage itself is retracted.
   A Wright "Cyclone" Model F.2 radial air-cooled engine, rated at 700 h.p. at 1,900 r.p.m., is mounted in the nose and enclosed in an N.A.C.A. cowling. A three-blade adjustable pitch metal airscrew is fitted. Fuel tankage for a range of 800 miles (1287,5 km), 123.2 gall. (560 litres), is provided in the centre section.
   The pilot's compartment is immediately behind the engine, aft of the fireproof bulkhead, and is fitted with a Vee-type inward sloping windscreen. The pilot sits on the port side and a mail compartment of 20 cu. ft. (0,57 m2) capacity occupies the starboard side of the cockpit. A soundproof bulkhead fitted with a small door separates the pilot from the passenger compartment. The eight passengers are seated two abreast, separated by a 12 in. {304,8 mm) aisle and the cabin seats are adjustable to three positions. The fuselage is 62 in. (1574,8 mm) high and 52 in. (1320,8 mm) wide. Behind the last seat is the main cabin door, and opposite this door is a fully equipped lavatory. Immediately behind the lavatory is the passengers' baggage compartment, and to the rear of this is the main radio installation. Standard equipment of the aircraft includes full night-flying instruments and flares, and complete two-way wireless.

Flight, October 1935

TWO AMERICAN MONOPLANES
By C. N. COLSON

   IT is not often that one is privileged to try out foreign aircraft in the country of their origin, so when, during a recent visit to the United States, I was given this opportunity I seized it with alacrity.
   The two machines with which I shall deal are both single-engined jobs, but there any similarity ceases. I chose them because they are at opposite ends of the scale, and I am therefore relieved of the doubtful pleasure of comparing them.
   The first is the Vultee, which I flew by invitation of Mr. E. L. Cord, whose Aircraft Development Company's plant I visited at Los Angeles.
   I had heard a great deal about the impression the Vultee had made on American pilots - how it was, perhaps, one of the nicest machines most of them had flown, how comfortable it was, and how its high cruising speed was revolutionising their ideas of air transport schedules. For that reason I had begun to think that this aeroplane must be a veritable paragon, and I wondered where the snags, if any, lay. Now, after handling the machine (ought I to say "ship"?) myself, I am not only as enthusiastic as they, but even go further and wonder why a Vultee has not been sent over here and why the licence has not been taken up by one of the firms who have recently been in the public eye in the matter of obtaining licences.
   Except for the forward-sloping windscreen, general cleanliness, retractable undercarriage, and certain details of manufacture, the Vultee does not differ radically from many other all-metal low-wing monoplanes with radial air-cooled engines; but the combination certainly puts it in a class by itself. The forward-sloping windscreen eliminates reflections of the kind which make it difficult for a pilot to look out when there is a background of bright clouds and also adds several m.p.h. to the speed. The efficacy of this feature has, it will be remembered, been proved in this country (as witness the result of the King's Cup Air Race) by Mr. F. G. Miles in his Falcon, and also in his Merlin.
   The cleanliness, achieved by careful attention to detail construction, wing-root and tail fairings, as well as other not-so-readily discernible points, results in a high performance, and also maintains a clean flow over the tail controls, so that there is ample control at all speeds and no evidence at all of those two bugbears of low-wing design - buffeting of the tail plane at large angles of incidence and sudden loss of elevator and/or rudder control when landing.
   I found the machine perfectly delightful to fly and quite unusually steady in bad weather. She has, of course, the fairly heavy "big ship" type of controls to be found on most American air transport machines, which require only a minimum of movement. It is possible that English pilots will expect something lighter on a machine of this size, but, personally, I think the American standard is best, particularly when it is remembered that the Vultee cruises at speeds of over 200 m.p.h.
   The speed of this machine makes it a most desirable transport aircraft and, at the same time, leads one to think very seriously of its possible military value. A machine of this construction could literally be sprayed with machine-gun bullets without any vital part being hit, and even as a transport machine its performance is away above that of many light bombers.
   A large cabin seating eight people in comfort, a lavatory, ample baggage accommodation, and a pilot's cockpit with full dual control; all this sounds a pretty big lump to expect a normal single-engined machine to carry, but this is what the Vultee achieves, and at over 200 m.p.h.
   The Wright Cyclone engine is supercharged and, using 87 octane fuel, with a boost pressure of about 36/38 in., the power output for the take-off is between 700 and 800 h.p., but once in the air the power taken is normally decreased greatly.
   Flying between San Diego and Los Angeles, a distance of 127 miles, which I covered in thirty-four minutes, I maintained an altitude of 5,000ft., and, according to the engine chart, the boost pressure of 25m. meant that I was taking only 425 h.p. out of the engine, but, nevertheless, the A.S.I, registered a steady 195 m.p.h. Allowing for the altitude and temperature (it was very hot outside, indeed, some 85 deg. on the ground), we must have been doing over 200 m.p.h. comfortably, the fuel consumption then being about 38 gallons per hour.
   At a higher altitude the economy is even more marked, and the pilots of the American Air Lines who use Vultees between Fort Worth, Texas, and Chicago generally try to fly between 8,000ft and 10,000ft. I made that flight myself later, and therefore had a good opportunity of judging the machine both from the passenger's and the pilot's points of view. It was not, perhaps, quite as quiet as some of the larger twin-engined machines but it is very easy to talk to one's neighbour, and there was an outstanding lack of vibration.
   A performance of this nature is, of course, quite useless if the take-off and landing characteristics are bad, but in the Vultee they are definitely good. When necessary the flaps can be lowered a few degrees and, with the engine throttle wide open, the machine can be taken off in quite a small space, but even without the flaps, or using the maximum allowable engine boost, the take-off is of the order of 15 sec. Landing is perfectly straightforward; the flaps provide as coarse a gliding angle as can be desired, and the speed is not unduly high. The operation of both the flaps and the undercarriage is simple in the extreme, either by an electric motor or by hand, and it is possible to stop the former in any desired position, the electric motor stopping automatically when they are right in or right out.
   Thus, then, the performance in the air. The Vultee is no less interesting from the constructional point of view. It has often been said that all-metal monococque construction is costly and does not permit of rapid production. Neither can be said of the Vultee. Throughout, there is evidence of the care and thought which has been given both to economical production and to economical output. The fuselage is truly monococque in that there are no longitudinal members, the skin doing the work of the longerons in more normal designs. In the shops the jigs are set up to secure absolute interchangeability, even to the replacement of one of the plates of Alclad forming the skin of the fuselage. This has actually been proved by replacing a damaged plate with one sent from stock in the factory to an aerodrome where no special skilled labour or equipment was available.

Projected Improvements

   The riveted heads all over the exterior of the machine do, of course, detract to some extent from the performance., and it is intended that all riveting shall be replaced by spot welding just as soon as this method of construction is permitted by the authorities. Even now spot welding is used whenever possible, as, for example, for the doors and nearly all the non-stressed parts. The general adoption of this method will make the Vultee the cleanest aircraft imaginable. The wings are built up with the double-skin system common to most metal cantilever jobs where the inner skin is corrugated and the outer skin is flat, the two being riveted together. Alclad sheet is used throughout. With this system the skin takes its share of the stress and forms a rigid, stable structure with the comparatively light rib and spar system built between the top and bottom surfaces.
   So much for the Vultee.
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