56-03-03 NAVION: Applies to All Models.
Compliance required as indicated.
Cracks starting at the wing centerline attaching bolt hole in the wing rear spar junction fittings (P/N 145-14070) at wing Station O have been found on a number of Navion aircraft.
To correct this, it will be necessary to inspect all Navions for this condition as soon as practicable but not later than May 1, 1956. Access to these fitting may be gained through the main wheel wells.
If no cracks are found, 3/16-inch thick 1010 steel (or equivalent) end plates, properly radiused for a snug fit, should be installed in each fitting prior to the next 50 hours of flight time.
If cracks are found, they should be stop-drilled with a No. 60 (0.040 drill and the end plates as described above should be installed prior to the next flight.
No further inspections will be necessary upon installation of these end plates.
(Ryan Navion Service Bulletin No. 23 dated December 5, 1955, covers this same subject.)