|37000 Feet||Browse and search NASA's
Aviation Safety Reporting System
|Local Time Of Day||1201 To 1800|
|Locale Reference||airport : yak.airport|
|Altitude||agl single value : 0|
|Operator||common carrier : air carrier|
|Make Model Name||B737-400|
|Operating Under FAR Part||Part 121|
|Flight Phase||landing : roll|
|Route In Use||approach : instrument precision|
|Affiliation||company : air carrier|
|Function||flight crew : first officer|
|Affiliation||company : air carrier|
|Function||flight crew : captain|
oversight : pic
|Experience||flight time last 90 days : 180|
flight time type : 150
|Anomaly||excursion : runway|
ground encounters other
|Independent Detector||other flight crewa|
other flight crewb
|Resolutory Action||flight crew : regained aircraft control|
Flight Crew Human Performance
Prior to commencing ILS runway 11; we intermittently monitored the ASOS; which reported airport winds between 040-050 degrees at 5 KTS with visibility fluctuating between 1 - 1 1/4 mi with light snow and mist. The snow removal crew had briefed us on the runway condition and provided us with mu readings in the upper 20's; I believe the actual numbers were 28; 28; and 29. As we approached the runway; the conditions had worsened considerably and we broke out at minimums with approximately 1/2 mi visibility and heavy snow. The captain made a normal landing; the speed brake deployed and he engaged the thrust reversers. Upon touchdown; the aircraft began to drift to the right. The captain had already stowed the thrust reversers and was trying to correct back to center. The aircraft continued to drift right towards the runway edge lights. The right main landing gear crossed outside the runway lights. The left main landing gear remained inside the lights and the aircraft was now in a left yaw but still not correcting. The aircraft slowed and the captain was able to regain enough control to direct the aircraft back to the center of the runway and bring it to a normal stop. At some point between the time we were sliding and the time we regained control of the aircraft; the master caution had illuminated; and I noted that the #1 engine had failed. I announced we had a #1 engine failure and immediately started the APU. After reviewing the engine indication instruments; we determined that the #2 engine was operating normally and the aircraft could be taxied to the ramp under its own power. While we were turning the aircraft around in order to back-taxi to the ramp; the runway surface was very slick. It was obvious by our tire tracks that we had landed in snow covered slush. The captain proceeded slowly and was able to maintain control and taxied to the ramp where we completed a normal shutdown and deplaned the passenger. About 30-40 mins after we blocked in; the captain walked out to the runway to find approximately 1-2 inches of fresh snow over a layer of slush. Later; while sitting in operations; we overheard the runway crew discussing the accuracy of the mu meter. There was concern the meter was not working properly and may need to be calibrated. As the runway crew prepared the runway for the arrival of another flight; the mu readings were in the teens although the snowfall was lighter than when we arrived. The crew felt those readings were not accurate and that the grip tester needed to be recalibrated. They then decided to use a tapley decelerometer which produced significantly different results. Supplemental information from acn 686404: we broke out at minimums from the ILS approach in heavy snow. After a normal landing and reverse selection; the aircraft began to drift to the right. Rudder input and reverse stowage had no effect on directional control. The right main gear eventually went outside the runway edge lights; but the left main gear remained inside them. As the aircraft slowed. Directional control was regained and the aircraft was stopped on the normal runway surface. During the rollout; the master caution light came on and the first officer said the #1 engine had failed. After we were stopped; all seemed ok except for the #1 engine; so I taxied to the ramp. After shutdown; we checked with the flight attendants. They were fine and had not really noticed anything wrong; nor had the passenger; who then deplaned normally. Prior to our approach; we were given mu readings in the high twenties; or 'fair' braking action. I have landed numerous times on runways with mu's in that range; and have always been able to easily control the aircraft with gentle steering and braking inputs. This time my inputs had no discernable effect leaving me with a 'helpless along for the ride' feeling. While turning around to taxi in; I thought the runway seemed more slippery than I had previously experienced. I walked out to the runway to find a little over 1 inch of new snow over a slush layer. I don't believe that the braking action was 'fair' at the time of our touchdown; or that the runway was properly prepared given the amount of snow on it when we landed. While sitting in operations waiting for flight to arrive; we were listening to the runway crew as they werepreparing the runway for landing. They were getting mu readings in the teens at that time. The runway crew thought those low readings were not accurate and that the mu meter needed to be recalibrated. They offered a conversion from their tapley value; but overflew the airport and continued to juneau. I thought that was a wise decision. Preventive measures. I don't think the runway surface was suitable for landing by the time we landed due to the rapid rate of heavy; wet; snow accumulation. I'm sure the snow removal crew did the best they could preparing for us; but I believe the wet snow; rapidly accumulating over a slush layer; made the mu values given to FSS; and then to us; quickly become obsolete. I also believe it caused our aircraft to hydroplane until the speed was reduced and I could steer again. I can only say that if ground personnel determine that 'heavy; wet' snow is accumulating faster than it can be cleared to maintain satisfactory runway condition; then both arrs and departures should be suspended. I realize that this is pretty subjective. I should say that we had just landed in cdv a little over 1 hour previous. There was also heavy snow falling there at the time; and we also broke out right at ILS minimums just as we did at yak. The difference is that it was colder there and the snow was much lighter and seemed 'dry' as opposed to what was falling at yak. We could easily steer; stop; taxi; and turn around on the runway there even though the WX observation was essentially identical to what we encountered at yak. This is kind of a tough thing to judge with the temperature; and the variable characteristics that 'snow' can have; all thrown into the mix; not to mention any existing runway contamination before the current snow began. I don't think a machine can make the judgement. I know this brings up a lot of 'schedule' issues; but I don't think snow squalls of the intensity falling when we landed in yak last very long.
Original NASA ASRS Text
Title: B737-400 CREW LOSES CTL OF THE ACFT ON LNDG ON SNOW AND SLUSH COVERED RWY. SEVERAL RWY LIGHTS ARE DAMAGED BEFORE CTL IS REGAINED. FAULTY MU METER BRAKING ACTION READINGS MAY HAVE CONTRIBUTED.
Narrative: PRIOR TO COMMENCING ILS RWY 11; WE INTERMITTENTLY MONITORED THE ASOS; WHICH RPTED ARPT WINDS BTWN 040-050 DEGS AT 5 KTS WITH VISIBILITY FLUCTUATING BTWN 1 - 1 1/4 MI WITH LIGHT SNOW AND MIST. THE SNOW REMOVAL CREW HAD BRIEFED US ON THE RWY CONDITION AND PROVIDED US WITH MU READINGS IN THE UPPER 20'S; I BELIEVE THE ACTUAL NUMBERS WERE 28; 28; AND 29. AS WE APCHED THE RWY; THE CONDITIONS HAD WORSENED CONSIDERABLY AND WE BROKE OUT AT MINIMUMS WITH APPROX 1/2 MI VISIBILITY AND HVY SNOW. THE CAPT MADE A NORMAL LNDG; THE SPD BRAKE DEPLOYED AND HE ENGAGED THE THRUST REVERSERS. UPON TOUCHDOWN; THE ACFT BEGAN TO DRIFT TO THE R. THE CAPT HAD ALREADY STOWED THE THRUST REVERSERS AND WAS TRYING TO CORRECT BACK TO CTR. THE ACFT CONTINUED TO DRIFT R TOWARDS THE RWY EDGE LIGHTS. THE R MAIN LNDG GEAR CROSSED OUTSIDE THE RWY LIGHTS. THE L MAIN LNDG GEAR REMAINED INSIDE THE LIGHTS AND THE ACFT WAS NOW IN A L YAW BUT STILL NOT CORRECTING. THE ACFT SLOWED AND THE CAPT WAS ABLE TO REGAIN ENOUGH CTL TO DIRECT THE ACFT BACK TO THE CTR OF THE RWY AND BRING IT TO A NORMAL STOP. AT SOME POINT BTWN THE TIME WE WERE SLIDING AND THE TIME WE REGAINED CTL OF THE ACFT; THE MASTER CAUTION HAD ILLUMINATED; AND I NOTED THAT THE #1 ENG HAD FAILED. I ANNOUNCED WE HAD A #1 ENG FAILURE AND IMMEDIATELY STARTED THE APU. AFTER REVIEWING THE ENG INDICATION INSTS; WE DETERMINED THAT THE #2 ENG WAS OPERATING NORMALLY AND THE ACFT COULD BE TAXIED TO THE RAMP UNDER ITS OWN PWR. WHILE WE WERE TURNING THE ACFT AROUND IN ORDER TO BACK-TAXI TO THE RAMP; THE RWY SURFACE WAS VERY SLICK. IT WAS OBVIOUS BY OUR TIRE TRACKS THAT WE HAD LANDED IN SNOW COVERED SLUSH. THE CAPT PROCEEDED SLOWLY AND WAS ABLE TO MAINTAIN CTL AND TAXIED TO THE RAMP WHERE WE COMPLETED A NORMAL SHUTDOWN AND DEPLANED THE PAX. ABOUT 30-40 MINS AFTER WE BLOCKED IN; THE CAPT WALKED OUT TO THE RWY TO FIND APPROX 1-2 INCHES OF FRESH SNOW OVER A LAYER OF SLUSH. LATER; WHILE SITTING IN OPS; WE OVERHEARD THE RWY CREW DISCUSSING THE ACCURACY OF THE MU METER. THERE WAS CONCERN THE METER WAS NOT WORKING PROPERLY AND MAY NEED TO BE CALIBRATED. AS THE RWY CREW PREPARED THE RWY FOR THE ARR OF ANOTHER FLT; THE MU READINGS WERE IN THE TEENS ALTHOUGH THE SNOWFALL WAS LIGHTER THAN WHEN WE ARRIVED. THE CREW FELT THOSE READINGS WERE NOT ACCURATE AND THAT THE GRIP TESTER NEEDED TO BE RECALIBRATED. THEY THEN DECIDED TO USE A TAPLEY DECELEROMETER WHICH PRODUCED SIGNIFICANTLY DIFFERENT RESULTS. SUPPLEMENTAL INFO FROM ACN 686404: WE BROKE OUT AT MINIMUMS FROM THE ILS APCH IN HVY SNOW. AFTER A NORMAL LNDG AND REVERSE SELECTION; THE ACFT BEGAN TO DRIFT TO THE R. RUDDER INPUT AND REVERSE STOWAGE HAD NO EFFECT ON DIRECTIONAL CTL. THE R MAIN GEAR EVENTUALLY WENT OUTSIDE THE RWY EDGE LIGHTS; BUT THE L MAIN GEAR REMAINED INSIDE THEM. AS THE ACFT SLOWED. DIRECTIONAL CTL WAS REGAINED AND THE ACFT WAS STOPPED ON THE NORMAL RWY SURFACE. DURING THE ROLLOUT; THE MASTER CAUTION LIGHT CAME ON AND THE FO SAID THE #1 ENG HAD FAILED. AFTER WE WERE STOPPED; ALL SEEMED OK EXCEPT FOR THE #1 ENG; SO I TAXIED TO THE RAMP. AFTER SHUTDOWN; WE CHKED WITH THE FLT ATTENDANTS. THEY WERE FINE AND HAD NOT REALLY NOTICED ANYTHING WRONG; NOR HAD THE PAX; WHO THEN DEPLANED NORMALLY. PRIOR TO OUR APCH; WE WERE GIVEN MU READINGS IN THE HIGH TWENTIES; OR 'FAIR' BRAKING ACTION. I HAVE LANDED NUMEROUS TIMES ON RWYS WITH MU'S IN THAT RANGE; AND HAVE ALWAYS BEEN ABLE TO EASILY CTL THE ACFT WITH GENTLE STEERING AND BRAKING INPUTS. THIS TIME MY INPUTS HAD NO DISCERNABLE EFFECT LEAVING ME WITH A 'HELPLESS ALONG FOR THE RIDE' FEELING. WHILE TURNING AROUND TO TAXI IN; I THOUGHT THE RWY SEEMED MORE SLIPPERY THAN I HAD PREVIOUSLY EXPERIENCED. I WALKED OUT TO THE RWY TO FIND A LITTLE OVER 1 INCH OF NEW SNOW OVER A SLUSH LAYER. I DON'T BELIEVE THAT THE BRAKING ACTION WAS 'FAIR' AT THE TIME OF OUR TOUCHDOWN; OR THAT THE RWY WAS PROPERLY PREPARED GIVEN THE AMOUNT OF SNOW ON IT WHEN WE LANDED. WHILE SITTING IN OPS WAITING FOR FLT TO ARRIVE; WE WERE LISTENING TO THE RWY CREW AS THEY WEREPREPARING THE RWY FOR LNDG. THEY WERE GETTING MU READINGS IN THE TEENS AT THAT TIME. THE RWY CREW THOUGHT THOSE LOW READINGS WERE NOT ACCURATE AND THAT THE MU METER NEEDED TO BE RECALIBRATED. THEY OFFERED A CONVERSION FROM THEIR TAPLEY VALUE; BUT OVERFLEW THE ARPT AND CONTINUED TO JUNEAU. I THOUGHT THAT WAS A WISE DECISION. PREVENTIVE MEASURES. I DON'T THINK THE RWY SURFACE WAS SUITABLE FOR LNDG BY THE TIME WE LANDED DUE TO THE RAPID RATE OF HVY; WET; SNOW ACCUMULATION. I'M SURE THE SNOW REMOVAL CREW DID THE BEST THEY COULD PREPARING FOR US; BUT I BELIEVE THE WET SNOW; RAPIDLY ACCUMULATING OVER A SLUSH LAYER; MADE THE MU VALUES GIVEN TO FSS; AND THEN TO US; QUICKLY BECOME OBSOLETE. I ALSO BELIEVE IT CAUSED OUR ACFT TO HYDROPLANE UNTIL THE SPD WAS REDUCED AND I COULD STEER AGAIN. I CAN ONLY SAY THAT IF GND PERSONNEL DETERMINE THAT 'HVY; WET' SNOW IS ACCUMULATING FASTER THAN IT CAN BE CLRED TO MAINTAIN SATISFACTORY RWY CONDITION; THEN BOTH ARRS AND DEPS SHOULD BE SUSPENDED. I REALIZE THAT THIS IS PRETTY SUBJECTIVE. I SHOULD SAY THAT WE HAD JUST LANDED IN CDV A LITTLE OVER 1 HR PREVIOUS. THERE WAS ALSO HVY SNOW FALLING THERE AT THE TIME; AND WE ALSO BROKE OUT RIGHT AT ILS MINIMUMS JUST AS WE DID AT YAK. THE DIFFERENCE IS THAT IT WAS COLDER THERE AND THE SNOW WAS MUCH LIGHTER AND SEEMED 'DRY' AS OPPOSED TO WHAT WAS FALLING AT YAK. WE COULD EASILY STEER; STOP; TAXI; AND TURN AROUND ON THE RWY THERE EVEN THOUGH THE WX OBSERVATION WAS ESSENTIALLY IDENTICAL TO WHAT WE ENCOUNTERED AT YAK. THIS IS KIND OF A TOUGH THING TO JUDGE WITH THE TEMP; AND THE VARIABLE CHARACTERISTICS THAT 'SNOW' CAN HAVE; ALL THROWN INTO THE MIX; NOT TO MENTION ANY EXISTING RWY CONTAMINATION BEFORE THE CURRENT SNOW BEGAN. I DON'T THINK A MACHINE CAN MAKE THE JUDGEMENT. I KNOW THIS BRINGS UP A LOT OF 'SCHEDULE' ISSUES; BUT I DON'T THINK SNOW SQUALLS OF THE INTENSITY FALLING WHEN WE LANDED IN YAK LAST VERY LONG.
Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.