DURING a test flight on a prototype Javelin aircraft, a flutter incident occurred involving the loss of both elevators. The pilot was fortunately able to continue flying the aircraft using the tail trimming control and subsequently made a crash landing. At the time of the incident all the recording instruments were running. These included an automatic observer, a chart recorder of control circuit forces and a two‐axis vibrograph which was mounted at the top of the fin. A copy of part of the record from the latter instrument is shown in FIG. 1. The upper stepped line is the timing signal and the lower trace gives the lateral displacement at the top of the fin, the rather spasmodic oscillations corresponding to the fin bending frequency of 4·8 c.p.s. The diverging oscillation shown on the centre trace corresponds to the vertical displacement at the top of the fin. From this and a similar record obtained from the elevator circuit force recorder, it was concluded that the elevators fluttered symmetrically at a frequency between 21 and 22 c.p.s.
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