malfunctions  on  both  types  of  recorders  appear basically  the  same.  See  table  2-1  for  a  listing  of common malfunctions and corrective actions. EVALUATION  OF  ANOMALOUS FEATURES Anomalous  features  detected  in  a  recorder  trace from  either  the  AN/SSQ-56  (series)  recorders  or  the AN/BQH-7(A)   recorder   may   invalidate   the observation.  Another  probe  should  be  launched  after the  cause  of  the  problem  is  identified  and  corrected. Although  somewhat  dated,  the  Naval  Oceanographic Office  Reference  Publication,  RP  21,  Guide  To Common   Shipboard   Expendable   Bathythermograph (SXBT)   Recording   Malfunctions,  identifies   and explains   the   cause   of   many   trace   anomalies.   This publication  should  be  thoroughly  reviewed  by  every operator. Obvious  equipment  malfunctions  normally  occur in  less  than  10  percent  of  all  launches.  However, improper  handling  of  the  probes  can  cause  a  greater number  of  failures  than  normal.  Rough  handling  or improper storage of probes can cause the flattening or compaction of the wire in the probe and canister spools, abrasion of the insulation on the wire, or tangles in the wire.  These  failures  can  be  significantly  reduced  by storing  the  probes  away  from  extreme  temperatures  and humidity.  Probes  should  always  be  maintained  in  a vertical position with the protective cap (weighted end of  probe)  down. When   conducting   an   observation,   the   operator should be aware of the expected thermal characteristics in the area. Large variations in thermal structure is quite common  in  the  vicinity  of  ocean  fronts  and  eddies.  If anomalous features are detected in the trace that cannot be attributed to a malfunction or to an expected thermal feature, a second probe should be launched. EVALUATION OF  TEMPERATURE  AND DEPTH The evaluation of the temperature curve is a simple, straightforward  matter. The  observer  must  select significant levels on the temperature curve so that the entire  curve  may  be  reconstructed  by  connecting  the selected  points  with  straight  lines.  Temperatures  are read to the nearest tenth of a degree (°C or °F) and to the nearest meter or tens of feet of depth. Temperature  Gradients There are three terms that are used to describe the gradient  (or  trend)  of  the  temperature  trace  on  a bathythermograph   chart. The  first  term  is  positive temperature gradient, and is defined as an increase in water temperature with depth. The next term, negative temperature  gradient,  is  the  opposite  of  positive temperature  gradient,  and  is  defined  as  a  decrease  in water   temperature   with   depth.   The   last   term   is isothermal gradient. It is defined as no change in water Table 2-1.—Common Malfunctions in Bathythermograph Recordings SYMPTOM CAUSE CORRECTION Stylus  makes  erratic  excursions  to Leak from probe wire to salt water. Launch  new  XBT. the right of the chart paper. Stylus makes excursion all the way   Complete  wire  breakdown. Launch  new  XBT, to  left  of  chart  paper  and  remains there. Stylus  makes  erratic  excursions  to   Contamination,   such   as   excessive    Breech  pins  should  be  wiped the left of chart paper. salt  water,  between  breech  and thoroughly  and  new  XBT  inserted. canister. Recorder    completely    inactive, POWER  switch  to  OFF  or  power Replace   fuse. indicators   not   illuminated. cord   unplugged.   Fuse   blown. INTERLOCK   switch   open. HF   radio   transmission   affect   Electromagnetic  interference. Change  capacitor. recorder   stylus. 2-11