PURPOSE: To predict wing collapse in advance on behalf of a pilot to generate an alarm by detecting effective ram pressure from the difference between detected atmospheric pressure and ram pressure in a wing, and generating an alarm in the case of the effective ram pressure being smaller than the allowable minimum value of effective ram pressure over the specified time.

CONSTITUTION: An atmospheric pressure sensor 10 measures atmospheric pressure changed by the flying atmosphere of a paraglider. A ram pressure sensor 11 measures ram pressure in the wing piece of the paraglider. Both measured results are inputted to the differential circuit 12 of a pressure discriminating circuit 16, and the difference between both is computed and inputted to a comparing circuit 14 as effective ram pressure Pa. The comparing circuit 14 compares the effective ram pressure Pa with the allowable minimum value Pth of effective ram pressure stored in a storage circuit 13, and in the case of the state of Pa<Pth continuing for the specified time or longer, an alarm signal Sa is outputted to an alarm device 17, and the alarm device 17 generates an alarm.