Waco S series

Aircraft Picture - Waco YKS-6 of 1936 at Sun n'Fun, Lakeland, Florida, in April 2009

Role: single-engine light cabin biplane
National origin: United States
Manufacturer: Waco Aircraft Company
First flight: 1935
Status: several airworthy in 2009
Primary user: small commercial operators and private owner pilots
Developed from: Waco C series

The Waco S Series is a family of American cabin biplanes produced by the Waco Aircraft Company starting in 1935.

Development and designations

The Waco closed cabin biplanes, initially known as the C (for Cabin) series were all unequal span, staggered single bay biplanes. They were fabric covered, the wings having a wooden structure and the control surfaces and fuselage constructed from metal frames. The wings were braced with outward splayed N form interplane struts plus a strut connecting the centre section rear spar to the bottom of the forward interplane strut, following Waco's standard practice. They had a fixed tailwheel undercarriage, which could be partially or completely faired. There was seating for 4/5 including the pilot. Most were powered by 7 cylinder radial engines of different makes.

When Waco released its slightly larger custom cabin series, those Cabin series aircraft it continued to produce were redesignated as 'Waco Standard Cabin series', with the final designation letter changing from C to C-S to S. For instance in 1935 the YKC became the YKC-S, then the YKS-6 in 1936. All three were indistinguishable from each other. Waco used numeric suffixes like -7 to indicate a subvariant introduced in 1937 and so on.

From about 1937, all S series aircraft had wings of constant chord. Externally, the S series differed from the Custom or later C series in continuing with early C series features such as ailerons on both wings, linked by a prominent strut, and square edged rear side windows. Like many Waco aircraft, the S series were available with several different engines.

Operational history

The S series proved to be popular with both commercial and private pilots and over 50 were still airworthy in 2001, including examples of the CPTP VKS-7F version. During the Second World War several S series aircraft were impressed by the USAAF as the UC-72K.

Variants

(per Simpson, 2001, p. 575 and Green, 1965, p. 307)

DKS-6
HKS-7
UKS-6
225 hp (168 kW) Continental W-670-K
UKS-7
225 hp (168 kW) Continental W-670-K
VKS-7
240 hp (179 kW) Continental W-670-M The -7F model was used in the CPTP program, F indicating that flaps were fitted.
VKS-7F
240 hp (179 kW) Continental W-670-M The -7F model was used in the CPTP program, F indicating that flaps were fitted.
YKS-6
225 hp (168 kW) Jacobs L-4
YKS-7
225 hp (168 kW) Jacobs L-4
ZKS-6
225 hp (168 kW) Jacobs L-5
ZKS-7
225 hp (168 kW) Jacobs L-5

Specifications (VKS-7F)

Data from Green, 1965, p. 307

General characteristics

Crew: 1
Capacity: 3 or 4 passengers
Length: 25 ft 3 in (7.70 m)
Wingspan: 33 ft 3 in (10.13 m)
Height: 8 ft 6 in (2.59 m)
Wing area: 244 ft (22.69 m)
Empty weight: 2,256 lb (1,023 kg)
Gross weight: 3,250 lb (1,474 kg)
Powerplant: 1 x— Continental W-670-M, 240 hp (179 kW)

Performance

Maximum speed: 145 mph (233 km/h)
Cruise speed: 127 mph (204 km/h)
Range: 518 miles (833 km)
Service ceiling: 13,000 ft (3,962 m)
Rate of climb: 850 ft/min (4.3 m/s)

Bibliography

Green, William (1965). The Aircraft of The World. Macdonald & Co. (Publishers) Ltd.
Grey, C.G. (1972). Jane's All the World's Aircraft 1938. David & Charles (Publishers) Ltd.
Simpson, Rod (2001). Airlife's World Aircraft. Airlife Publishing Ltd. ISBN 1-84037-115-3.
Brandley, Raymond (1981). Waco Airplanes Ask Any Pilot - The Versatile Cabin Series. R.H. Brandly. ISBN 0-9602734-2-5.

Waco S series Pictures

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Source: WikiPedia