The stabilized bombing approach equipment used by the Bureau of Ordnance contains a small precisely machined dash-pot which is required to give a viscous damping effect on the response of the automatic pilot. Various damping fluids have been used in the past but no one fluid has been found capable of operating over the entire temperature range encountered (-406F to 130°F).nThis Laboratory has investigated the damping character¬istics necessary for satisfactory operation of the S.B.A.E. and has studied the viscosity-temperature behavior of a number of promising liquids using two S.E.A.E units obtained by the Bureau of ordnance. Investigations were made using laboratory methods coordinated with a flight test made at N.P.G., Dahlgren, Va.nIt has been found that due to the broad damping re¬quirements of the S-B-A-E- and to the considerable manual adjustment available in the instrument to compensate for the change of viscosity with temperature, the problem is much simplified.nUtilizing these properties and the exceptionally flat viscosity temperature characteristics of either of two new petroleum oils or the newer organo-silicon fluids, it was found possible to obtain a single damping fluid capable of covering the whole range of temperature encountered in service.nIt was found that the two S.B.A.E. units varied in their construction and showed differences in their behavior. These _ differences have been more than allowed for in preparing the present specifications for the proper dash-pot fluid. If, however, still greater differences occur among dash-pots in use, the present specifications will include a large fraction and merely restrict somewhat the temperature ranges of useful¬ness of the extremely variant S.B.A.E. units.
展开▼
