Narrative:

While on a repositioning flight from hio to pdx on an IFR clearance in VFR conditions at 4000 ft MSL, I observed an over charge indication on my battery. I immediately began to troubleshoot the problem. While I could see pdx throughout the event, and could have proceeded to the airport in VFR conditions, I continued to follow ATC instructions for traffic flow and monitored other aircraft visually and by use of onboard TCASII. When the problem could not be remedied, I asked for priority handling while I continued to troubleshoot the problem and verifying with the emergency checklist. The over voltage and battery problem was becoming worse and I was concerned that I could be developing a thermal runaway with the nicad battery. At this point I needed to get the airplane on the ground. I received instructions to turn to heading 020 degrees which I acknowledged. The first officer and I saw another airplane inbound to runway 28L at about 2 O'clock and low from our position. My flight path would take us above and behind the airplane inbound for the runway 28L. My procedure during any VFR arrival is to look outside and monitor my TCASII for other air traffic. This procedure is for additional safety margin. This is what I did throughout this event. I heard the controller call another airplane and tell them 'I have an airplane with an emergency/priority and I need to get them on the ground.' while continuing to troubleshoot, I lost all radio equipment and ahrs screens for a few moments, and so, lost communications with ATC. I got the equipment turned back on, then I called the controller and asked, 'portland are you still with me?' the controller asked for my altitude and I informed her that I was on my way to 2500 ft. I do not believe the controller knew the first officer and I had the other airplane in sight, that my battery indications were rapidly worsening, and my TCASII showed no other aircraft in my flight path. I was now very busy in the cockpit. I had the other airplane in sight and was well clear, and I needed to get my airplane on the ground. She told me to 'climb immediately' and I complied back to 4000 ft. The airplane inbound for the other runway was well clear from us at all times and passed underneath our flight path. I was instructed by a new controller to descend again and intercept the localizer and was cleared for the approach. I complied. The fire equipment followed me and stood by. I shut down the airplane and inspected the battery with the fire crew at the ready. I was asked by pdx tower to call pdx approach supervisor and I complied. I explained that my cockpit was very busy during those few moments, attempted to explain to the supervisor that I had a situation that was quickly deteriorating with the airplane. He didn't seem concerned. He said that the controller 'would like to get her hands around my throat.' I then called my pilatus representative and described the battery and system malfunction event. Perceptions: controller did not know that I was in VFR conditions and was concerned about traffic separation minimums. Judgements: since I could see the other aircraft, I determined that I was able to maintain safe separation from the other airplane. Decisions and actions: I decided that my deteriorating situation required immediate action to get my aircraft on the ground before I had a thermal condition in my nicad battery. I was able to maintain safe separation from other aircraft and so I turned to assigned heading and descended in preparation to turn to the airport as quickly as I could. Factors affecting the quality of human performance: the controller was very busy and I was unable to state my condition while dealing with the worsening situation. I decided I had to take action immediately while maintaining VFR separation. Since the situation was changing rapidly, including temporary loss of radios and instruments, I was unable to communicate in a timely manner. The controller did not know I was able to maintain traffic separation. I believe she thought there was danger of a collision.

Google
 

Original NASA ASRS Text

Title: PILATUS PC-12 CREW HAD THE DEVELOPING POTENTIAL OF A NI-CAD BATTERY THERMAL RUNAWAY IN PDX CLASS B. THE CREW DECLARED AN EMER AND PROCEEDED TO PDX. THE APCH CTLR BECAME AGITATED BECAUSE THE PC-12 INTERFERED WITH AN ACR ON APCH.

Narrative: WHILE ON A REPOSITIONING FLT FROM HIO TO PDX ON AN IFR CLRNC IN VFR CONDITIONS AT 4000 FT MSL, I OBSERVED AN OVER CHARGE INDICATION ON MY BATTERY. I IMMEDIATELY BEGAN TO TROUBLESHOOT THE PROB. WHILE I COULD SEE PDX THROUGHOUT THE EVENT, AND COULD HAVE PROCEEDED TO THE ARPT IN VFR CONDITIONS, I CONTINUED TO FOLLOW ATC INSTRUCTIONS FOR TFC FLOW AND MONITORED OTHER ACFT VISUALLY AND BY USE OF ONBOARD TCASII. WHEN THE PROB COULD NOT BE REMEDIED, I ASKED FOR PRIORITY HANDLING WHILE I CONTINUED TO TROUBLESHOOT THE PROB AND VERIFYING WITH THE EMER CHKLIST. THE OVER VOLTAGE AND BATTERY PROB WAS BECOMING WORSE AND I WAS CONCERNED THAT I COULD BE DEVELOPING A THERMAL RUNAWAY WITH THE NICAD BATTERY. AT THIS POINT I NEEDED TO GET THE AIRPLANE ON THE GND. I RECEIVED INSTRUCTIONS TO TURN TO HDG 020 DEGS WHICH I ACKNOWLEDGED. THE FO AND I SAW ANOTHER AIRPLANE INBOUND TO RWY 28L AT ABOUT 2 O'CLOCK AND LOW FROM OUR POS. MY FLT PATH WOULD TAKE US ABOVE AND BEHIND THE AIRPLANE INBOUND FOR THE RWY 28L. MY PROC DURING ANY VFR ARR IS TO LOOK OUTSIDE AND MONITOR MY TCASII FOR OTHER AIR TFC. THIS PROC IS FOR ADDITIONAL SAFETY MARGIN. THIS IS WHAT I DID THROUGHOUT THIS EVENT. I HEARD THE CTLR CALL ANOTHER AIRPLANE AND TELL THEM 'I HAVE AN AIRPLANE WITH AN EMER/PRIORITY AND I NEED TO GET THEM ON THE GND.' WHILE CONTINUING TO TROUBLESHOOT, I LOST ALL RADIO EQUIP AND AHRS SCREENS FOR A FEW MOMENTS, AND SO, LOST COMS WITH ATC. I GOT THE EQUIP TURNED BACK ON, THEN I CALLED THE CTLR AND ASKED, 'PORTLAND ARE YOU STILL WITH ME?' THE CTLR ASKED FOR MY ALT AND I INFORMED HER THAT I WAS ON MY WAY TO 2500 FT. I DO NOT BELIEVE THE CTLR KNEW THE FO AND I HAD THE OTHER AIRPLANE IN SIGHT, THAT MY BATTERY INDICATIONS WERE RAPIDLY WORSENING, AND MY TCASII SHOWED NO OTHER ACFT IN MY FLT PATH. I WAS NOW VERY BUSY IN THE COCKPIT. I HAD THE OTHER AIRPLANE IN SIGHT AND WAS WELL CLR, AND I NEEDED TO GET MY AIRPLANE ON THE GND. SHE TOLD ME TO 'CLB IMMEDIATELY' AND I COMPLIED BACK TO 4000 FT. THE AIRPLANE INBOUND FOR THE OTHER RWY WAS WELL CLR FROM US AT ALL TIMES AND PASSED UNDERNEATH OUR FLT PATH. I WAS INSTRUCTED BY A NEW CTLR TO DSND AGAIN AND INTERCEPT THE LOC AND WAS CLRED FOR THE APCH. I COMPLIED. THE FIRE EQUIP FOLLOWED ME AND STOOD BY. I SHUT DOWN THE AIRPLANE AND INSPECTED THE BATTERY WITH THE FIRE CREW AT THE READY. I WAS ASKED BY PDX TWR TO CALL PDX APCH SUPVR AND I COMPLIED. I EXPLAINED THAT MY COCKPIT WAS VERY BUSY DURING THOSE FEW MOMENTS, ATTEMPTED TO EXPLAIN TO THE SUPVR THAT I HAD A SIT THAT WAS QUICKLY DETERIORATING WITH THE AIRPLANE. HE DIDN'T SEEM CONCERNED. HE SAID THAT THE CTLR 'WOULD LIKE TO GET HER HANDS AROUND MY THROAT.' I THEN CALLED MY PILATUS REPRESENTATIVE AND DESCRIBED THE BATTERY AND SYS MALFUNCTION EVENT. PERCEPTIONS: CTLR DID NOT KNOW THAT I WAS IN VFR CONDITIONS AND WAS CONCERNED ABOUT TFC SEPARATION MINIMUMS. JUDGEMENTS: SINCE I COULD SEE THE OTHER ACFT, I DETERMINED THAT I WAS ABLE TO MAINTAIN SAFE SEPARATION FROM THE OTHER AIRPLANE. DECISIONS AND ACTIONS: I DECIDED THAT MY DETERIORATING SIT REQUIRED IMMEDIATE ACTION TO GET MY ACFT ON THE GND BEFORE I HAD A THERMAL CONDITION IN MY NICAD BATTERY. I WAS ABLE TO MAINTAIN SAFE SEPARATION FROM OTHER ACFT AND SO I TURNED TO ASSIGNED HDG AND DSNDED IN PREPARATION TO TURN TO THE ARPT AS QUICKLY AS I COULD. FACTORS AFFECTING THE QUALITY OF HUMAN PERFORMANCE: THE CTLR WAS VERY BUSY AND I WAS UNABLE TO STATE MY CONDITION WHILE DEALING WITH THE WORSENING SIT. I DECIDED I HAD TO TAKE ACTION IMMEDIATELY WHILE MAINTAINING VFR SEPARATION. SINCE THE SIT WAS CHANGING RAPIDLY, INCLUDING TEMPORARY LOSS OF RADIOS AND INSTS, I WAS UNABLE TO COMMUNICATE IN A TIMELY MANNER. THE CTLR DID NOT KNOW I WAS ABLE TO MAINTAIN TFC SEPARATION. I BELIEVE SHE THOUGHT THERE WAS DANGER OF A COLLISION.

Data retrieved from NASA's ASRS site as of July 2007 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.