SPPF  Software Pin Programming Function 
SPR  Service and Performance Report 
SPRDR  Spreader 
SPRT  Support 
SPS  Service Process Solution 
SPSA  Supplier Product Support Agreement 
SPST  Single Pole Single Throw 
SPS/B  Superseded by 
SQ  Squelch 
SQ-FT  Square-Feet 
SQW  Square Wave 
SR  Senior 
SRD  Shorted Rotating Diode 
SRD  System Requirement Document 
SRE  Surveillance Radar Element of GCA 
SRF  Servicing and aircraft condition parameters Reporting Function 
SRKL  Structural Repair Kit List 
SRKM  Structural Repair Kit Manual 
SRM  Structural Repair Manual 
SRPS  Safe Redundant Power Supply 
SRPSU  Slide Release Power Supply Unit 
SRS  Speed Reference System 
SRU  Shop Replaceable Unit 
SS  Sky/Shading 
SSA  System Safety Assessment 
SSA  Side Slip Angle 
SSALS  Simplified Short Approach Light System 
SSALSR  Simplified Short Approach Light System Runway Alignment 
SSB  Single Side Band 
SSC  Single Stroke Chime