An instrument designed for use on ships from which aircraft are to be launched by catapult (or assisted take off gear).

The indicator is metallic, possibly anodised aluminium. A rectangular frame carries a rotatable inset circular scale 112 mm in diameter, reading 0–180 (black)–0 (red) with radial slot labelled 'Wind you feel', scaled 0–90 with a slider controlled from reverse side. The rectangular frame carries a scale on the right-hand edge, labelled 'Wind ahead 90–0 Wind astern 0–70'. On the left-hand upper corner, a slot carries a locking lever labelled 'Ship’s speed'. On the right-hand corner is a locking lever labelled 'Wind' and 'Wind astern'. At the bottom is the notation 'SRE'. The rear is labelled 'Ship’s Course', 'S.A. Ltd London' and 'Serial number A 89193'. It also has a circular scale 0–360 degrees with a radial slot marked 0 -60 with sliding knob and locking knob, labelled 'True Wind Knots'.

Case: A mahogany or similar hinged wood case with leather handle, keyhole but no key, felt-lined, marked AP NO. 3281

Accompanied by a booklet (210 x 139 mm), 'SRE True Wind Calculator' by Simmonds Aerocessories Ltd, London, with photographs.

Aircraft must take off or be launched into wind. An aircraft carrier having a flight deck can be turned into the wind, thus maximising the airflow into which the aircraft is to be launched. On other ships such as battleships the superstructure prevents the aircraft being launched along the ship’s length. The ship must be turned so that the combined vector effect of wind due to the ship’s speed and the true (meteorological) wind is maximised and the ship’s catapult can be turned into the effective wind. This instrument is used to perform the calculations.