10/31/2009. Two Grebes, J7400 and J7385, were specially modified in 1926 for air-launching experiments in connection with the Airship Development Programme and were carried under the British rigid airship R-33. They were slung from its keel by quick release attachments on the upper wings and were braced by struts from the airship's structure to stabilize them and prevent oscillation. The Jaguar engines were started by means of a Bristol gas starter carried inside the R-33 and connected to the engines by flexible piping.

On 21 October, 1926, after an ascent from Pulham in Norfolk, one Grebe was released at about 2,500 ft (762 m) and, after diving for about 100 ft (30 m), it leveled out and flew for several minutes before landing back at Pulham. The second aircraft was also successfully released from a slightly higher altitude after some difficulty in starting the engine and made a safe landing at Cardington. Both aircraft were flown by pilots from the Royal Aircraft Establishment at Farnborough, Flying Officers R. L. Ragg and C. Mackenzie-Richards.

J7400, shown here attached to airship R-33, was later converted to a two-seater.