Menasco Unitwin 2-544

Menasco Unitwin 2-544
Type
National origin USA
Manufacturer Menasco Motors Company
First run 1938
Major applications Vega Altair 8G and Vega Starliner models 2 and 22
Developed from C6S Super Buccaneer

Menasco Motors Company of Burbank, California was a well known manufacturer of inverted inline four and six cylinder engines. At the request of Lockheed Aircraft designers, Menasco produced an inverted twelve-cylinder air cooled aircraft engine by designing a common crankcase and gearbox for two of the six cylinder engines. The two crankshafts were combined with a unique double clutch gearbox to power a single propeller. The engine, known as the Unitwin 2-544, was a success, but did not enter production as no aircraft manufacturer designed an aircraft that used it.

Design and development

In mid-1935 Lockheed's chief engineer, Hall Hibbard, began discussing with Al Menasco, the president of the Menasco Motors Company in Burbank, the merits of coupling two Menasco C6S Super Buccaneer six-cylinder in-line engines mounted side-by-side, driving a single propeller.[1]

In 1937 Lockheed established the AiRover Aircraft Company as a subsidiary to give Lockheed a place in the personal aviation market. Hall Hibbard wanted AiRover to use Menasco's novel twin powerplant in its first aircraft. AirRover used components of various Lockheed aircraft to construct what was designated as the Lockheed Altair 8G to serve as a flying test stand for the unproven Menasco engine. This test bed was first flown in December 1937 and confirmed the merits of its powerplant, leading to the decision to proceed with the design of a similarly-powered five-seat feeder-liner.[2]

During 1938 the AiRover Company was reorganized as the Vega Aircraft Corporation, and with Mac V.F. Shortits installed as president, it started the design the new feeder-liner. Jack Wassail was the project engineer, and the aircraft was soon under construction in Vega's new A-1 plant, located at the recently purchased Lockheed Air Terminal.[3]

Applications

The Starliner was the first totally new Vega Airplane Company aircraft. It made its maiden flight at Burbank on April 22, 1939, with Vern Dorrell as pilot and J.B. Kendrick as engineering observer. This first flight, however, ended with an emergency when the propeller accidentally slipped into fine pitch. Vern Dorrell succeeded in landing on a vacant field, with minimum damage to the aircraft.
Once repaired, and modified with single vertical tail surface and an upgraded 640 hp Unitwin engine, the Starliner model 2 became the model 22 when it resumed its test flights. The Starliner was damaged again when Bud Martin had to land it on its main wheels when the nose wheel failed to come down. With the nose protected by the partially protruding front wheel, the aircraft again escaped with only slight damage to its lower cowling.
Repaired a second time, the Starliner satisfactorily completed a total of 85 flying hours; but due to its limited capacity of a pilot and four or five passengers, it was too small to satisfy the needs of the airlines. The only Starliner ended its life as a non-flying prop at a film studio.

Variants

The Unitwin was developed in at least three versions:

520 hp Unitwin Original version
600 hp Unitwin for the Starliner model 2
640 hp Unitwin for the Starliner model 22

Survivors

None of these engines are flying or in Museums.

Specifications (U 2-544)

Data from Peter & Rita Forbes' Engine Webpages

General characteristics

Components

Performance


References

  1. ↑ http://theautry.org/collections/aviation-development-in-southern-california-5
  2. ↑ Francillon
  3. ↑ http://www.pilotfriend.com/acft_manu/Lockheed%20Martin.htm
  4. ↑ aircraftone.com