AN ACR MLG FLC GETS A SLAT DISAGREEMENT LIGHT AND FINDS THAT THE SLATS; IN FACT; DID NOT EXTEND TOGETHER AND A ROLLING MOMENT DEVELOPED. AFTER A PERIOD OF ANALYSIS; A NO-SLAT; TRAILING EDGE FLAP ONLY LNDG WAS SAFELY MADE AT VREF +25 KTS.

Date: 1997-04 · Aircraft: DC-9 30

Anomalies: aircraft-equipment-problem-critical|other-unspecified

Synopsis

AN ACR MLG FLC GETS A SLAT DISAGREEMENT LIGHT AND FINDS THAT THE SLATS; IN FACT; DID NOT EXTEND TOGETHER AND A ROLLING MOMENT DEVELOPED. AFTER A PERIOD OF ANALYSIS; A NO-SLAT; TRAILING EDGE FLAP ONLY LNDG WAS SAFELY MADE AT VREF +25 KTS.

Narrative

STARTED A VISUAL APCH TO RWY 23L AND EXTENDED SLATS AND FLAPS WITH AUTOPLT ENGAGED. OBSERVED SLAT DISAGREEMENT LIGHT ON AND BLUE SLAT EXTENDED LIGHT DID NOT ILLUMINATE. ALSO GOT WINDSHEAR LIGHT WITH NO AURAL WARNING OR ACFT PITCH CHANGE. RECEIVED STALL SHAKER INTERMITTENTLY AT HIGHER THAN EXPECTED AIRSPD. EXECUTED A GAR AND PROCEEDED W OF THE AIRFIELD TO ANALYZE THE PROB. REQUESTED TO REMAIN VFR AT 3500 FT MSL. WE VERIFIED ABNORMAL SLAT DEPLOYMENT WHILE I HAND FLEW THE ACFT AND THE CAPT REVIEWED THE COMPANY ABNORMAL PROCS. WHEN FLAPS WERE EXTENDED THE ACFT STARTED A ROLL TO THE L. WE SELECTED FLAPS ONLY (NO SLATS) FOR APCH AND LNDG. AFTER LNDG WAS COMPLETE AND WE CLRED THE RWY WE TERMINATED THE EMER AND RELEASED THE FIRE TRUCKS. WHILE THE SIT WAS RESOLVED WITH NO COMPLICATIONS SEVERAL FACTORS LIMITED CREW REACTION AND RESOLUTION TIME. FUEL WAS ONLY ENOUGH TO FLY TO AND LAND AT DEST. WE CONSIDERED LNDG WHERE MAINT WAS AVAILABLE; BUT WERE LIMITED TO LNDG ONLY AT DEST. NO DISCRETE COMPANY FREQ WAS AVAILABLE TO ADVISE DISPATCH; OR TALK WITH MAINT PERSONNEL. MAINT AVAILABLE AT TYS WAS NOT IMMEDIATELY AVAILABLE AND HAD TO BE CALLED OUT AFTER THE SIT WAS RESOLVED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THIS FO OF A DC9-30 SAID THAT THE ARPT WAS SURROUNDED BY TSTMS WHILE THEY WERE MAKING THEIR APCH. THE FIRST THAT THEY KNEW OF THEIR SLAT PROB WAS WHEN THE SLAT DISAGREEMENT LIGHT ILLUMINATED. THEY ALSO NOTED THAT THE 'BLUE' SLAT EXTEND LIGHT WAS NOT ON. AS THE FO STARTED TO TROUBLESHOOT THE SLAT PROB THE CAPT TOOK THE ACFT AND STARTED A TURN TOWARD RWY 23L. THE WINDSHEAR ALARM LIGHT ILLUMINATED; BUT WITHOUT AN AURAL WARNING. THIS WAS LATER DETERMINED TO HAVE BEEN CAUSED BY A SLIGHT SLIP THAT RESULTED FROM THE UNEVEN SLAT DEPLOYMENT. AS THE CAPT WAS ROLLING OUT OF THE TURN AND STARTING TO SLOW; THE STALL WARNING ACTIVATED AND THE FLC DECIDED TO GAR. AS THE FLC WAS PERFORMING THE GAR THEY DISCOVERED THAT THE STALL WARNING WOULD ACTIVATE AT SPDS AS HIGH AS 210 KIAS; MUCH HIGHER THAN ANTICIPATED FOR THIS CONFIGN. THEY THEN HAD THE FO FLY THE ACFT WHILE THEY RETRACTED AND THEN EXTENDED THE FLAPS AND SLATS; AND THE FO NOTED THAT THERE WAS A PRONOUNCED ROLLING MOMENT WHICH WAS NOT PRESENT DURING THE INITIAL EXTENSION. THEY THEN PROCEEDED WITH THE ALTERNATE; TRAILING EDGE FLAP EXTENSION BY USE OF THE SPLIT FLAP/SLAT HANDLE ON THE CTR AISLE STAND. THIS WAS SUCCESSFUL AND THE FO CONTINUED THE APCH AT NORMAL APCH +25 KTS; WHILE THE CAPT MONITORED THE ACFT. THE RPTR SAID THAT JUST AS HE WAS FLARING TO TOUCHDOWN A LARGE GUST HIT THE ACFT AND THE TWR CALLED RPTING AT 25 KT TAILWIND. THE RPTR SAID THAT HE TOUCHED DOWN AT THAT TIME AS THE AIRSPD DROPPED FROM THE EFFECT OF THE TAILWIND GUST. THE TOUCHDOWN AND ROLLOUT WAS NORMAL. MAINT DETERMINED LATER THAT A SLAT ACTUATOR HAD FAILED AND THEY REPLACED IT.

Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.