51-27-02 BOEING: Applies to all Model B-377 Aircraft equipped with Goodrich H-3-626 and H-3-650 Wheel Assemblies.
To be accomplished as indicated below.
As a precautionary measure to preclude serious hazards which may result from fatigue cracks in Goodrich H-3-626 and H-3-650 wheel assemblies, all wheels shall be carefully inspected with at least a 4x magnifying glass at the periodic inspection following each 50th landing. These inspections shall be conducted until the wheels must be retired from service. The wheels must be retired at the time replacement wheels are made available. Due to the fact that a large quantity of B-377 wheel halves were delivered to the operators without being assigned a serial number, the following description will identify both the wheel to be replaced and also the replacement wheel. The wheels to be retired from service are those wheels which have a tapered spoke and no reinforcing beading around the inner side of the spoke cutout area. Replacement wheels are those wheels which have a reinforcing bead around the inner side of the spoke cut-out area and have either straight or tapered spokes.
(Goodrich Service Bulletin No. 27, dated November 14, 1951, covers this identification problem in further detail.)
Type I - Cracks Progressing Across a Spoke.
The wheel should be rejected when there is more than one crack of this type to a spoke, when there is more than one crack in each spoke cutout, or when a crack is in excess of 1 inch in length.
Type II - Cracks Progressing Radially Across the Brake Drum Mounting Flange.
More than one crack of this type in any one spoke cutout will be cause for rejection.
Type III - Cracks in the Tie Bolt Recess and the Junction of the Drum Mounting Area.
This type crack is in a noncritical area and is cause for wheel rejection only when either of the following conditions occur:
1. The crack extends to the spoke cutout.
2. Developed cracks on either side of the recess progress to within 1 3/8 inches of each other.
The above wheel crack limitations are based on the recommendations of the B. F. Goodrich Co.
(Goodrich Service Bulletin No. 17 covers this subject and illustrates the three types of wheel cracks.)