Flight, August 1928
THE BACH "AIR YACHT"
An American Three-Engined Monoplane
MULTI-ENGINED aircraft - especially those fitted with three engines - are apparently gaining increasing favour with American aircraft designers, for during the last few months
a number of machines of this class have been produced by various firms. In the majority of cases, also, the type of machine adopted is the high-wing cabin monoplane, which is very much in fashion just now, not only in America, but on this side of the Atlantic as well.
A recent American machine of this class - the three-engined high-wing monoplane - is the Bach "Air Yacht," produced by the Bach Aircraft Co., of Santa Monica, California, and described below. The Bach "Air Yacht" is a ten-place cabin machine designed to meet the requirements for commercial work on airways, and although following the lines of the popular type referred to above, it possesses several distinctive characteristics of its own.
It is, it is claimed, particularly suitable for the demands of airways passenger service - its wide-track landing gear of 17 ft. making for good take-off and landing on uneven ground; the comparatively thick, tapering, "semi-cantilever" wing, strongly braced, providing an ample structural safety factor; and the rigid construction of the fuselage, built in the form of a stout shell completely surfaced with plywood, affording all the protection of a closed motor car, are all features adapted with this end in view.
When the machine was flight tested at Clover Field, Calif., last August, an actual speed of 135 m.p.h. was attained with the engines running at less than full throttle, seven passengers on board, and with sand ballast equivalent in weight to two more passengers. It was also demonstrated that flight could be maintained on the centre engine alone, or any combination of the smaller wing engines.
The centre engine is a 250 h.p. Waterman 9-cyl. air-cooled radial, while the two wing engines are smaller ones, being 100 h.p. Kinner 5-cyl. air-cooled radials. The central engine is mounted in the nose of the fuselage, and the wing engines are suspended below by struts in such a manner as to absorb most of the vibration within the mounts. Each of these wing engines is housed in a neat streamlined cowling, and are located several feet to the rear of the centre engine. Head resistance, so far as the engines are concerned, is thus reduced to a minimum - which, in fact, holds good elsewhere in this machine, exposed surfaces having been faired or streamlined.
The wings, which, as previously stated, are of fairly thick section, taper from root to tip, and are in two main sections, being attached to a central root, formed on the top of the fuselage, which contains the fuel tanks. The latter contain fuel sufficient for a 7-hours' flight, while the oil tanks are built in the engine mounts, within the cowling.
Wing bracing is by streamlined struts, sloping out and up from the bottom of the fuselage to the wings, via the wing engines. Of the tail surfaces only the rudder is balanced.
The fuselage is of the cabin type, of deep rectangular section tapering to a vertical knife edge at the rear. The pilot's cockpit is located in the nose immediately behind the centre engine and just forward of the leading edge of the wing. A curved wind shield conforming to the general outline extends up to the leading edge of the wing, affording the pilots ample protection from the elements and at the same time providing an excellent visibility.
Dual "Dep" control is fitted, and the two seats are arranged on either side of a large door giving easy access to the passenger cabin. The latter, which has a displacement of 228 cub. ft., is luxuriously fitted up, the walls and arched roof being finished in matched grain gumwood. The chairs are deep and comfortable, and in the sides of the cabin are large non-shutterable glass windows, adjustable from within. Fittings are of satin-finish silver, while electric cigar-lighters, card tables, concealed ice-water tank, and lavatory (with hot water) are some of the conveniences provided.
In addition to the passenger cabin there is a luggage space of 40. cub. ft. If required, the machine can be converted into a freight carrier in 10 minutes.
The landing gear, which, as before stated, is exceptionally wide, has proved to be highly efficient in tests. The landing shock is taken up by a hydraulic absorber permitting a vertical displacement of 14 in. Lesser taxying shocks are taken by the usual rubber absorbers enclosed within the wing motor nacelles. Sauzedde wheels and brakes, with 35 by 8 in. tyres, are controlled in unison by a hand-brake lever within the cockpit, or operated independently for taxying by the rudder bar.
In conclusion, it may be mentioned that besides the "Air Yacht" the Bach Company have produced two other types - the C-S.1, a small three-seater cabin biplane, and the C-S.2, a four-seater of similar type.
The principal characteristics of the Bach "Air Yacht" are as follows :-
Span 52 ft. 3 in.
O.A. length 37 ft. 3 in.
Wing area 412 sq. ft.
Weight, empty 2,650 lb.
Weight, laden 5,500 lb.
Weight per sq. ft. 13-3 lb.
Weight per h.p. 12-2 lb.
Speed range 40-120 m.p.h.
Fuel capacity 150 gals.
Everling Quantities (Metric)
High-speed figure 11-3