In multi‐engined aircraft a device, e.g., a relay, is provided which operates, should one engine stall at take‐off or shortly after take‐off, to shut off the other engine or engines to bring about balance of the craft. The circuit of the device includes two switches, one of which is influenced within a pre‐determined dynamic pressure range by a Pitot tube and the other of which is adapted to be closed by a member influenced by the difference in the speeds of the engines. As shown, the relay 21, 22 is connected to the pivot 7 of a bell‐crank switch lever 6 and through a battery 23 and switch 26 to a contact 14 on a member 13 pivoted on a slidable member 15 carrying contacts 24, 25. The member 13 is loosely connected to sleeves 10, 11, actuated by governors 10, 11 driven by the engines. The contacts 24, 25 are connected to a contact 9 on a quadrant 8 over which the switch member 6 is moved by a diaphragm in a casing 4 to which are connected the dynamic and static pressure conduits 3,2 of a Pitot tube 1. The arrangement is such that the dynamic pressure immediately after take‐off is just sufficient to close the switch 6, 9 and then, if one engine stalls, the member 13 is moved to cogage the contact 14 with one or other of the contacts 24, 25 and thus energize the relay. The distance between tile contacts 24, 25 may be adjustable.
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