Narrative:

We encountered a complete loss of directional control while attempting to park the aircraft at the gate. Everything appeared to be normal until the last 25 ft of taxi-in. We were coming in single engine with the #2 engine shut down. I was taxiing very slow; around 3-5 mph. I was straight on the lead-in line when all of a sudden the nose of the aircraft started to yaw to the right and it felt like we were 'sliding on ice.' the running engine was at idle by this time. I immediately tried to steer the jet back to the left by using left nosewheel tiller. It was totally ineffective. I was ultimately able to stop the aircraft with differential braking. It appeared we had drifted 4-6 ft right of the lead-in line. It happened so fast that we were basically 'along for the ride.' it was a tense and somewhat unsettling couple of seconds. I asked the first officer to pull out the tow-in checklist; as I realized we had a serious malfunction. The guide man kept signaling me to continue in; so I gave him the hand signal to hook up the head set. Once we had established communication; I advised him that I had lost directional control; and that we would need to be towed in. All surfaces at the airdrome were bare and dry except for an area around the gate. It looked 'wet' around the parking area. The temperature was in the mid 40's. I asked the guide man if there was any ice down there. He said no; but there was a lot of 'soapy water' from a ramp sweeper that had come through earlier. We were towed to the gate and accomplished our checklists. I asked the first officer to call ramp control and advise them of what happened so they could look into it; and possibly rectify the situation. I did not want anyone else to have the same thing happen to them. I was taxiing at a very slow pace! If I had been going just a few KTS faster; we would have had too much inertia to stop before we hit the aircraft parking next to us or ramp equipment in the area. I thought that was the end of my somewhat eventful morning. I was wrong. As we were deplaning the passenger; the phone in the jetway rang. I was saying goodbye to the people; so the purser went out to answer it. I could see her on the phone. I immediately sensed something was wrong by the expression on her face. I walked over to her and she just looked at me with concern in her eyes and handed me the phone. It was a zone controller who was saying in a frantic voice to 'stop deplaning; stop deplaning. We have an out of limits center of gravity...don't let any more passenger off the airplane...we have to move some cargo or it is going to tip on its tail;' or something to that effect. I said this is the captain and I understand. Call us back when you have it under control. I ran back into the airplane and made an announcement to the people to stop where they were. I was very frank. I explained the situation and asked for their understanding and cooperation; but it was a matter of safety. Within a few mins the phone rang -- zone called and said it was ok to continue deplaning. Things were starting to make a little more sense to me now. We had a bigger problem than I initially realized. The first officer and I gathered all the paperwork and our gear and proceeded up to the flight office to report this situation to flight management. With the help of a flight manager we called maintenance to write up what happened just in case there was a mechanical problem. Although at this point; I knew in my mind what was the likely culprit. Looking back now; I have a few comments and observations I would like to make. When we got our final weights in san diego; I saw we had a center of gravity of 39.1%. I made the comment to the first officer that 39% was a 'pretty aft center of gravity;' but it was within limits. From my experience in the military; I became very familiar with a wide range of center of gravities and the effect they can have on aircraft stability and performance. That being said; I would like to know exactly what happened with our load planning. Was there a mistake made? Were we ever within tolerances? Was I dispatched illegally? Something was obviously wrong. Why was I; the captain; the last to know? Airplaneshave fallen out of the sky because they were out of center of gravity limits. Our load planning has had all kinds of reported problems. It's my understanding that we are under extra scrutiny from the FAA because of these problems. At this time I do not have all the facts concerning what exactly happened. How did they know to call us and tell us of our situation? Someone knew something; but when and how did they know? The bottom line is this: thank god my quick reaction; luck and judgement prevented this incident from becoming an accident. No wonder why the airplane wouldn't turn left. There wasn't enough weight on the nosewheel. I almost bent metal and/or injured ramp personnel today. I am not happy to know improper load planning played an integral part in this.

Related reports:

Google
 

Original NASA ASRS Text

Title: A320 EXPERIENCES UNCTLABLE YAW DURING PARKING AT GATE. LATER DETERMINED A FAR AFT CTR OF GRAVITY AND A SLICK RAMP SURFACE RESULTED IN LOSS OF DIRECTIONAL CTL WITH THE NOSEWHEEL STEERING.

Narrative: WE ENCOUNTERED A COMPLETE LOSS OF DIRECTIONAL CTL WHILE ATTEMPTING TO PARK THE ACFT AT THE GATE. EVERYTHING APPEARED TO BE NORMAL UNTIL THE LAST 25 FT OF TAXI-IN. WE WERE COMING IN SINGLE ENG WITH THE #2 ENG SHUT DOWN. I WAS TAXIING VERY SLOW; AROUND 3-5 MPH. I WAS STRAIGHT ON THE LEAD-IN LINE WHEN ALL OF A SUDDEN THE NOSE OF THE ACFT STARTED TO YAW TO THE R AND IT FELT LIKE WE WERE 'SLIDING ON ICE.' THE RUNNING ENG WAS AT IDLE BY THIS TIME. I IMMEDIATELY TRIED TO STEER THE JET BACK TO THE L BY USING L NOSEWHEEL TILLER. IT WAS TOTALLY INEFFECTIVE. I WAS ULTIMATELY ABLE TO STOP THE ACFT WITH DIFFERENTIAL BRAKING. IT APPEARED WE HAD DRIFTED 4-6 FT R OF THE LEAD-IN LINE. IT HAPPENED SO FAST THAT WE WERE BASICALLY 'ALONG FOR THE RIDE.' IT WAS A TENSE AND SOMEWHAT UNSETTLING COUPLE OF SECONDS. I ASKED THE FO TO PULL OUT THE TOW-IN CHKLIST; AS I REALIZED WE HAD A SERIOUS MALFUNCTION. THE GUIDE MAN KEPT SIGNALING ME TO CONTINUE IN; SO I GAVE HIM THE HAND SIGNAL TO HOOK UP THE HEAD SET. ONCE WE HAD ESTABLISHED COM; I ADVISED HIM THAT I HAD LOST DIRECTIONAL CTL; AND THAT WE WOULD NEED TO BE TOWED IN. ALL SURFACES AT THE AIRDROME WERE BARE AND DRY EXCEPT FOR AN AREA AROUND THE GATE. IT LOOKED 'WET' AROUND THE PARKING AREA. THE TEMP WAS IN THE MID 40'S. I ASKED THE GUIDE MAN IF THERE WAS ANY ICE DOWN THERE. HE SAID NO; BUT THERE WAS A LOT OF 'SOAPY WATER' FROM A RAMP SWEEPER THAT HAD COME THROUGH EARLIER. WE WERE TOWED TO THE GATE AND ACCOMPLISHED OUR CHKLISTS. I ASKED THE FO TO CALL RAMP CTL AND ADVISE THEM OF WHAT HAPPENED SO THEY COULD LOOK INTO IT; AND POSSIBLY RECTIFY THE SITUATION. I DID NOT WANT ANYONE ELSE TO HAVE THE SAME THING HAPPEN TO THEM. I WAS TAXIING AT A VERY SLOW PACE! IF I HAD BEEN GOING JUST A FEW KTS FASTER; WE WOULD HAVE HAD TOO MUCH INERTIA TO STOP BEFORE WE HIT THE ACFT PARKING NEXT TO US OR RAMP EQUIP IN THE AREA. I THOUGHT THAT WAS THE END OF MY SOMEWHAT EVENTFUL MORNING. I WAS WRONG. AS WE WERE DEPLANING THE PAX; THE PHONE IN THE JETWAY RANG. I WAS SAYING GOODBYE TO THE PEOPLE; SO THE PURSER WENT OUT TO ANSWER IT. I COULD SEE HER ON THE PHONE. I IMMEDIATELY SENSED SOMETHING WAS WRONG BY THE EXPRESSION ON HER FACE. I WALKED OVER TO HER AND SHE JUST LOOKED AT ME WITH CONCERN IN HER EYES AND HANDED ME THE PHONE. IT WAS A ZONE CTLR WHO WAS SAYING IN A FRANTIC VOICE TO 'STOP DEPLANING; STOP DEPLANING. WE HAVE AN OUT OF LIMITS CTR OF GRAVITY...DON'T LET ANY MORE PAX OFF THE AIRPLANE...WE HAVE TO MOVE SOME CARGO OR IT IS GOING TO TIP ON ITS TAIL;' OR SOMETHING TO THAT EFFECT. I SAID THIS IS THE CAPT AND I UNDERSTAND. CALL US BACK WHEN YOU HAVE IT UNDER CTL. I RAN BACK INTO THE AIRPLANE AND MADE AN ANNOUNCEMENT TO THE PEOPLE TO STOP WHERE THEY WERE. I WAS VERY FRANK. I EXPLAINED THE SITUATION AND ASKED FOR THEIR UNDERSTANDING AND COOPERATION; BUT IT WAS A MATTER OF SAFETY. WITHIN A FEW MINS THE PHONE RANG -- ZONE CALLED AND SAID IT WAS OK TO CONTINUE DEPLANING. THINGS WERE STARTING TO MAKE A LITTLE MORE SENSE TO ME NOW. WE HAD A BIGGER PROB THAN I INITIALLY REALIZED. THE FO AND I GATHERED ALL THE PAPERWORK AND OUR GEAR AND PROCEEDED UP TO THE FLT OFFICE TO RPT THIS SITUATION TO FLT MGMNT. WITH THE HELP OF A FLT MGR WE CALLED MAINT TO WRITE UP WHAT HAPPENED JUST IN CASE THERE WAS A MECHANICAL PROB. ALTHOUGH AT THIS POINT; I KNEW IN MY MIND WHAT WAS THE LIKELY CULPRIT. LOOKING BACK NOW; I HAVE A FEW COMMENTS AND OBSERVATIONS I WOULD LIKE TO MAKE. WHEN WE GOT OUR FINAL WTS IN SAN DIEGO; I SAW WE HAD A CTR OF GRAVITY OF 39.1%. I MADE THE COMMENT TO THE FO THAT 39% WAS A 'PRETTY AFT CTR OF GRAVITY;' BUT IT WAS WITHIN LIMITS. FROM MY EXPERIENCE IN THE MIL; I BECAME VERY FAMILIAR WITH A WIDE RANGE OF CTR OF GRAVITIES AND THE EFFECT THEY CAN HAVE ON ACFT STABILITY AND PERFORMANCE. THAT BEING SAID; I WOULD LIKE TO KNOW EXACTLY WHAT HAPPENED WITH OUR LOAD PLANNING. WAS THERE A MISTAKE MADE? WERE WE EVER WITHIN TOLERANCES? WAS I DISPATCHED ILLEGALLY? SOMETHING WAS OBVIOUSLY WRONG. WHY WAS I; THE CAPT; THE LAST TO KNOW? AIRPLANESHAVE FALLEN OUT OF THE SKY BECAUSE THEY WERE OUT OF CTR OF GRAVITY LIMITS. OUR LOAD PLANNING HAS HAD ALL KINDS OF RPTED PROBS. IT'S MY UNDERSTANDING THAT WE ARE UNDER EXTRA SCRUTINY FROM THE FAA BECAUSE OF THESE PROBS. AT THIS TIME I DO NOT HAVE ALL THE FACTS CONCERNING WHAT EXACTLY HAPPENED. HOW DID THEY KNOW TO CALL US AND TELL US OF OUR SITUATION? SOMEONE KNEW SOMETHING; BUT WHEN AND HOW DID THEY KNOW? THE BOTTOM LINE IS THIS: THANK GOD MY QUICK REACTION; LUCK AND JUDGEMENT PREVENTED THIS INCIDENT FROM BECOMING AN ACCIDENT. NO WONDER WHY THE AIRPLANE WOULDN'T TURN L. THERE WASN'T ENOUGH WT ON THE NOSEWHEEL. I ALMOST BENT METAL AND/OR INJURED RAMP PERSONNEL TODAY. I AM NOT HAPPY TO KNOW IMPROPER LOAD PLANNING PLAYED AN INTEGRAL PART IN THIS.

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.