DEPARTMENT OF THE NAVY
OFFICE OF THE CHIEF OF NAVAL OPERATIONS
WASHINGTON 25, D.C.

OP-503E1/am
Ser: 879P50

4 April 1951

AVIATION CIRCULAR LETTER NO. 9-51

From: Chief of Naval Operations

To: All Ships, Stations, and Units concerned with Navy Aircraft

Subj: Special Suffix to Model Designation for Aircraft Involved in Conversion

1. Purpose. To establish a reporting procedure which will identify conversion aircraft in the controlling custody of Materiel and Services, Bureau of Aeronautics; and to establish a definite understanding as to how and when the model designation changes for all conversion aircraft.

2. Cancellation. No cancellations are involved. Reporting procedures established in ACL 75-50 are hereby augmented for reporting custodians of aircraft in the controlling custody of Materiel and Services, Bureau of Aeronautics.

3. General Procedure. "Conversion" is work done to an aircraft which changes the aircraft enough to warrant change of the model designation thereof (e.g. TBM-3E to TBM-3W2, JRB-5 to SNB-5, etc.). Aircraft may be converted either while in the controlling custody of a major operating command or while in the controlling custody of Materiel and Services, Bureau of Aeronautics. The reporting procedure is different for the two cases as follows:

a. Conversion of aircraft in custody of major operating commands. The model designation changes only if and when the rework process of conversion is completed, and OpNav X report of that completion will show in the "model designation" column both the old and the new, with the old opposite the "from" line and the new opposite the "to" line.

b. Conversion of aircraft in custody of Materiel and Services. Bureau of Aeronautics.

(1) As soon as an aircraft is selected to be converted, regardless of the status and how long before it will be converted, the reporting custodian shall report on OpNav X a change in model designation of the aircraft. The entry will show, in OpNav X column for "model designation" the old designation opposite the "from" line and, opposite the "to" line, will show the model designation which the plane will be after conversion plus the letter "X" suffixed thereto (e.g. from TBM-3E to TBM-3W2X, from JRB-4 to SNB-5X, from F6F-5 to F6F-5KX, etc.). The suffix "X" to a model designation will mean "to be converted to this model, but conversion not completed".

(2) After reported change of model designation as above and until the process of conversion is completed, records and reports shall identify the aircraft with the new designation plus suffix "X". This includes aircraft log books, flight records, OpNav A and C (or equivalent), OpNav X, Y, and Z and the like. In case the decision to convert an aircraft is reversed after its selection has been reported, the reverse of 3b(1) should be reported on OpNav X.

(3) When the rework process of conversion is completed, OpNav X report of that completion will show in the "model designation" column a double entry with the model designation plus "X" opposite the "from" line and with the model designation without "X" opposite the "to" line. (Example: from TBM-3W2X to TBM-3W2). Thenceforth, of course, the latter will prevail as identification of the model.

4. In some cases, for certain models specified by the Chief of Naval Operations, converted aircraft begin a new service life in accordance with planning factors for the new model designation. For such aircraft, concurrent with change of model designation in accordance with 3b(l) above, records and reports of aircraft will reflect a turnback of service tour data (number of tour, months in last tour, hours in last tour) and "flying hours since acceptance" from whatever it may have been to zero. Thenceforth, such data will, be accumlated in the same manner as if the plane were accepted by the Navy on the date the model designation changed. However, as long as the aircraft remains in the Bureau of Aeronautics, Materiel and Services custody, OpNav X column G entry for "month and year of service tour" will continue to reflect the date the Bureau of Aeronautics, Materiel and Services last received controlling custody of the aircraft.

/S/
H. S. DUCKWORTH,
By direction.