MD-80 CAPT DESCRIBES THE CONDITIONS THAT LEAD TO SPOILER RETRACTION AFTER AUTO DEPLOYMENT ON LNDG.

Narrative

THERE ARE CONDITIONS IN WHICH THE SPOILERS WILL SOMETIMES STOW AFTER TOUCHDOWN. THE CONDITIONS ARE LNDG AT GROSS WEIGHTS BTWN 125000 AND 130000 POUNDS; AND A FORWARD C.G. LONGITUDINALLY; WITH A TRIM INDEX GREATER THAN 6; AND USUALLY AT 8 OR HIGHER; AND A XWIND COMPONENT USUALLY 10 KNOTS OR GREATER. IN ADDITION; LNDG ON AN UPSLOPING RWY; OR ON CERTAIN RWYS WITH TERRAIN FEATURES THAT PROMOTE DOWNDRAFTS AT THE THRESHOLD DURING WINDY CONDITIONS; OR LARGE TEMPERATURE DEWPOINT SPREADS FROM MID-DAY TO LATE AFTERNOON THAT TEND TO GENERATE (SINKERS) DURING THE FLARE; WILL EXACERBATE THE TENDENCY FOR THE SPOILER LEVER TO STOW DURING LNDG. THE REASON THE SPOILER LEVER STOWS IS THAT; UNDER THE ABOVE CONDITIONS; YOU ARE OFTEN TOUCHING DOWN WITH THE THROTTLES ABOVE THE 22 DEG SWITCH. WHEN THE MAINS TOUCH; THE SPOILER LEVER COMES BACK; THE SYSTEM THEN SENSES THE THROTTLES BEYOND 22 DEGS AND THE SPOILER LEVER THEN STOWS ITSELF. THIS OCCURANCE IS NOT A MALFUNCTION OF THE SYSTEM; BUT IS DUE TO A SET OF CIRCUMSTANCES THAT ARE NOT ENCOUNTERED TOO OFTEN. WHEN I SEE THESE CONDITIONS PRESENT DURING THE APCH; I BRIEF THE FO ON THE POSSIBILITY OF HAVING THE SPOILERS STOW THEMSELVES AFTER TOUCHDOWN. SOMETIMES THEY DO AND SOMETIMES THEY DON'T.