59-06-04 NAVION: Tusco Corporation (Navion) Applies to All Models.
Several failures of hydraulic actuating cylinders have occurred causing the loss of the use of the flaps and the landing gear to collapse.
To prevent further difficulties of this nature, the following items must be accomplished by May 1, 1959, and at each periodic inspection thereafter.
(1) Inspect the flap and landing gear actuating cylinders for cracks. If any cracks appear, the cylinder must be replaced.
(2) Determine, by means of a hydraulic gage, that the hydraulic system pressure relief valve is adjusted to 1125+25, -0 p.s.i. Excessive pressures could cause damage to the components of the system.
(3) Hydraulic fluid restrictors are required in the nose gear lines, Serial Numbers 1271 and subsequent, main gear lines, Serial Numbers 1790 and subsequent, and flap lines, all serial numbers.
(4) Inspect the linkage adjustments of the landing gear bungee springs and the flap stops anddetermine that they have been properly adjusted in accordance with appropriate service manuals.
(Tusco Corporation Service Letter No. 79 dated December 23, 1958, covers this same subject.)