In Sergeant Bigglesworth C.I.D., the Renkell Swan was a light civilian aircraft used by the gang of jewel thieves led by ex-Nazi fugitive Julius Hans Gontermann.
According the Rudolf Preuss, manager of the Renkell works, Ludwig Renkell designed the Swan towards the end of the war hoping to cash in on a potential civilian market.
When Biggles examined the aircraft, he found it very well-equipped, with all necessary instrumentation and a roomy cabin. However he was suspicious of a number of things. The equipment in the aircraft would make the final product expensive, in the order of some two thousand pounds, and this would price it out of the market. Moreover, the fuel capacity was unusually large, capable of giving it a range of some two thousand miles. Too much for a light civil type. Finally, he noticed the absence of a radio. There was a thick bulkhead which would do little more than contribute to excessive weight. Perhaps that bulkhead concealed a compartment with a radio, probably hidden because it was more capable than a civilian light aircraft would need. Finally, the prototype had been painted a dull unattractive yellow ochre colour--not very appealing for a civilian type. Biggles speculated that this might be because it was being used in the Libyan desert where various names associated with Renkell, notably Kurt Baumer, had served during the war.
The Renkell Swan as imagined by Francis Bergèse in Le cygne jaune (Miklo). There is not much description in the text except that it is of a ochre colour which this is. Biggles observed a family resemblance in the shape of the rudder. The artist has faithfully reproduced this as can be seen by comparing it with the drawings of the Renkell Wolf. However the original novel states that Renkell preferred ovals. The rudder here is not oval.