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Short Mayo Composite in model diorama

21 January 2013

Short Mayo Composite in model diorama

The Mayo Composite consisting of the mothership Maia and Mercury with  Martin M-130 Pan Am Flying Clipper  in the background — photo by Joseph May

During the intense competition beginning in the early 1930s to be the major airline to carry mail across the Atlantic Ocean. Major Mayo of the Short Brothers aircraft company arrived at a clever engineering solution to increase range and payload with what is known as the Mayo Composite — simply put the cargo carrying aircraft lifted into the air by the mothership flying boat. Simple in concept, perhaps, but the details in the making of this design make it an extraordinary one. The Mercury could be loaded to a much greater weight than it could take off with since the Maia would carry both aircraft aloft until the Mercury could safely fly away carrying mail across the Atlantic Ocean. Aerodynamically, Mercury could shed the parasitic drag penalty needed to lift off once aloft and in flight — clever thinking.

A moment in the life of the Mayo Composite tied to her anchor buoy as a member of the flight crew steps off a lighter — photo by Joseph May

The mothership was the Short Brothers S.21, Maia — the predecessor to the famous Empire flying boat design with four Bristol Pegasus air cooled radial engines. The cargo carrying aircraft was the Short Brothers S.20 design know as Mercury, powered by four Napier-Halford Rapier V air cooled in-line engines. The Mayo Composite would take off using all the power of the eight engines and, as the airspeed increased during flight, Mercury’s wings became the primary lift, as the lift of Maia’s wing fell away, which ensured a positive separation would occur when commanded. Mayo used the nature of forces in the engineering concept to ensure that Mercury absolutely had to separate from Maia but only at the proper moment. Also part of the ingenious design was the separation procedure with a system of three locks. First a pair of locks for each set of pilots would be released to allow the automatic release locks to function — and these automatic locks would not spring release until the design separation speed of 150 mph (240kph) had been attained. The Mayo Composite relied on mechanics and aerodynamic forces in an age before computerization and electronic sensors. 

A better view of Mercury and her twin floats as well as the air cooled in-line engines — photo by Joseph May

Flights were successful but not in terms of economy though the initiative of the designer and the daring of the flight crews were exemplary. Alas, neither Maia or Mercury have survived but we have many skilled modelers who have crafted miniature replicas of the Mayo Composite, few of them if any more skilled than Jim Lund who made this model diorama I saw on temporary display at the San Francisco Airport Museum & Library in an exhibit entitled, Oceans by Air: scale models and photographs by Jim Lund.

A view of Maia’s bows with pennant, perhaps fallen, in the lighter — photo by Joseph May

Though not containing references or citations this link regarding the Mayo Composite is a wonderfully written essay rich in detail about this extraordinary part of aviation’s history — it is part of Mike’s Engineering Wonders: vintage pages from the 1930s.

The idea of the Mayo Composite has not disappeared, though, it has evolved to the use of JATO (jet assisted take off) bottles for overloaded aircraft — which are jettisoned after becoming airborne — once again ridding the aircraft of the parasitic drag needed only for getting aloft.

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4 Comments leave one →
  1. 21 January 2013 06:06

    A bold concept, indeed! Juan Trippe and Pan American Airways had better luck with the Sikorsky, Martin, and Boeing flying boats for trans-oceanic routes, without the need for a “piggy back” aeroplane… [These scale models are beautiful.]
    (Joe: Should you be in the TPA Bay area on February 2nd, we are looking for a speaker at our FAHS annual general meeting and luncheon. It will be a small group. Please advise.)

    • travelforaircraft permalink*
      21 January 2013 10:37

      Of course you are right. Trippe was able to get no less than the three U.S. aviation companies to compete and produce transoceanic ranged aircraft. The British could not, so the Mayo Composite was created while the Germans created a system where Dornier floatplanes were catapulted off of ships. The German and British aircraft carried only mail where Trippe’s PAA aircraft also carried cargo and passengers. No comparison really, I would think.

      I’d consider it a privilege to speak at the FAHS meeting and thank you for the consideration:) I’ll be in touch by email.

      • Allan Damp permalink
        23 January 2013 10:26

        The big problem for the British was the lack of competition. All transport aircraft back then were commissioned by the Minstry of Aviation, with virtually no consultation with the airline (also a Government department) that was going to operate the airplanes.

      • travelforaircraft permalink*
        31 January 2013 10:25

        Yes, I think that it is hard to argue the point.

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