AD 57-25-01

57-25-01 Applies to All Aircraft engaged in Spraying Operations, Including Restricted Purpose Aircraft Certificated Under CAR Part 8 Equipped With Diaphragm Type Spray Pressure Regulators Vented in the Cockpit.

Compliance required by February 1, 1958.

A recent accident was caused by the failure of the diaphragm in a spray pressure regulator which permitted spray fluid to enter the cockpit through the regulator vent. Since this accident, reports have been received of several other cases of failures of these units. To prevent the release of toxic vapors into cabins or cockpits of spray planes, it is required that all diaphragm type pressure regulators be vented to the outside of the airplane. This venting may be accomplished similar to the spray tank venting noted in Section 2.415, Appendix A, of CAM 8 by means of a suitable tubing or hose extension to the outside of the fuselage.