This manual lists spares and repair parts; special tools; special test, measurement, and diagnostic equipment (TMDE), and other
special support equipment required for performance of direct support and general support maintenance of the AN/TPN-18A. It
authorizes the requisitioning and issue of spares and repair parts as indicated by the source and maintenance codes.
This Repair Parts and Special Tools List is divided into the following sections:
a. Section II. Repair Parts List. A list of spares and repair parts authorized for use in the performance of maintenance. The list
also includes parts which must be removed for replacement of the authorized parts. Parts lists are composed of functional groups in
numeric sequence, with the parts in each group listed in figure and item number sequence.
b. Section III. Special Tools List . Not applicable.
c. Section IV. National Stock Number and Part Number Index. A list, in National item identification number (NIIN) sequence, of all
National stock numbers (NSN) appearing in the listings, followed by a list, in alphameric sequence, of all part numbers appearing in
the listings. National stock numbers and part numbers are crossreferenced to each illustration figure and item number appearance.
Explanation of Columns
a. Illustration. This column is divided as follows:
(1) Figure number. Indicates the figure number of the illustration on which the item is shown.
(2) Item number. The number us ed to identify item called out in the illustration.
b. Source, Maintenance, and Recoverability (SMR) Codes .
(1) Source code. Source codes indicate the manner of acquiring support items for maintenance, repair, or overhaul of end
items. Source codes are entered in the first and second positions of the Uniform SMR Code format as follows:
PA -Item procured and stocked for anticipated or known usage.
PB -Item procured and stocked for insurance purpose because essentiality dictates that a minimum quantity be available
in the supply system.
PD-Support item, excluding support equipment, procured for initial issue or outfitting and stocked only for subsequent or
additional initial issues or outfitting. Not subject to automatic replenishment.
MD-Item to be manufactured or fabricated at the depot maintenance level.
AO-Item to be assembled at organizational level.
AH-Item to be assembled at general support maintenance level.
AD-Item to be assembled at depot maintenance level.
XA-Item is not procured or stocked because the requirements for the item will result in the replacement of the next higher
XD-A support item that is not stocked. When required, item will be procured through normal supply channels.
Cannibalization or salvage may be used as a source of supply for any items source coded above
except those coded XA and aircraft support items as restricted by AR 700-41/42.
(2) Maintenance code. Maintenance codes are assigned to indicate the levels of maintenance authorized to USE and REPAIR
support items. The maintenance codes are entered in the third and fourth positions of the Uniform SMR Code format as follows:
(a) The maintenance code entered in the third position will indicate the lowest maintenance level authorized to remove,
replace, and use the support item. The maintenance code entered in the third position will indicate one of the following levels of
0 -Support item is removed, replaced, used at the organizational level.
F -Support item is removed, replaced, used at the direct support level.
H -Support item is removed, replaced, used at the general support level.
D -Support items that are removed, replaced, used at depot, mobile depot, specialized repair activity only.
(b) The maintenance code entered in the fourth position indicates whether the item is to be repaired and identifies
the lowest maintenance level with the capability to perform complete repair (i.e., all authorized maintenance functions).
This position will contain one of the following maintenance codes:
F -The lowest maintenance level capable of complete repair of the support item is the direct support level.
H -The lowest maintenance level capable of complete repair of the support item is the general support level.
D -The lowest maintenance level capable of complete