Lysander Delanne

Lysander P12

This text was only possible after finding the June 1990 edition of the magazine "Aeroplane Monthly". Thanks Paul Deweer for helping to find this text.

Why a tandemwinged Lysander?

The Westland Lysander sure is a classic WW2 airplane. Less known is its P12 variant. Why this variant? It all starts with the Battle of France (September 1939 to May 1940). 88 of the 174 Lysanders were shot out of the sky. It proved that the Lysander with its maximum of two Browning guns in the rear cockpit was a easy prey for the German Messerschmitts. What was needed? More guns in the rear! But ... placing heavy guns in the tail will lead to a CG (center of gravity) going beyond the rear limit. Dangerous flight-behavior!

Westland meets Delanne

The Westland chief designer, Arthur Davenport, knew the Flying Flea of Henri Mignet. He also heard about another Frenchman, Maurice Henri Delanne, who was making a prototype of a tandemwinged fighter. The thinking became easy:

"Need heavy guns in rear leads to CG going too far backwards.Possible solutions:

  • less heavy guns
  • more backwards aft limit for CG

A larger wing in the tail would create more lift in the rear and a resulting more backwards CG range."

The Westland Lysander P12

The Delanne was close to what you needed. So... two persons were sent to Paris in early 1940 to meet Delanne. The technical director "Teddy" Petter and testpilot Harald Penrose Flew to Paris. Penrose even flew the Delanne 20T and was happy with its flight-behavior.

Prototype K6127

After a number of windtunnel tests with models the work on the prototype began. Lysander prototype K6127 lost its original rear cockpit and got a mock-up of a Frazer Nash turret.

Maiden flight: July 27, 1941.


Testpilot Penrose reports that all was like the original Lysander expect that the rudders only became effective at higher speeds (see disadvantages of Delanne). Weird thing was that the airplane proved to be ... more stable. That testflight ended with a loop. Now, if that is not a proof of confidence by its pilot. He sure liked it.

Later tests proved the wide CG range which is common in the Delanne configuration.

During later handling trials they did the tests in three conditions.

  1. CG at forward limit (45% of aerodynamic mean chord (AMC))
  2. CG at normal limit (52,3% of AMC)
  3. CG at aft limit (58,2% of AMC)


  • Rudders were ineffective below 64 km/h (40 mph).
  • Little swing to left if loading at aft limit.
  • Initial climb was like the original Lysander, only needing a little rudder.
  • Aircraft proved easy to fly
  • Rudder control became heavy at 450 km/h (280 mph). Below that speed it was rather light.
  • The automatic slots in the front wing caused problems when they changed position (close to open).
  • Dives were "smooth and remarkably steady".

The end of the Lysander P12

Before full tests were done, the official support was lost. The P12 was official of duty on June 13, 1944.

They first had thought that the Delanne concept could be used in other projects. Heavy bombers in special. A heavy (in weight and power) rear turret on those would be good. Petter proposed a four-engine bomber with a four gun turret to specification B.8/41. Westland thought about a Halifax modification with a turret in the rear.

The test-pilot Penrose proposed a rather light airplane, the Penrose Gremlin. Stress and performance calculations were already done. But the proposal never got build because the intended light engine (Wren) never got materialized. All the others engines at that time with the same performance were too heavy for this proposal. The engine was placed on the rear of the airplane and a heavier engine would have placed the engine needlessly backwards.

No more data is found yet about later English Duo-Mono projects.