BOISE, ID, USA
N25BH
CESSNA 402B
N3408Q
Piper PA-34-200T
AT 2059 MDT, A LIGHTNING STRIKE OCCURRED, RESULTING IN A POWER OUTAGE IN THE AIR TRAFFIC CONTROL (ATC) TOWER. ELECTRICAL POWER WAS RESTORED, BUT SOME EQUIPMENT (INCLUDING THE RADAR COMPUTER AND VOICE RECORDERS) REMAINED INOPERATIVE FOR A TIME. AT ABOUT 2121 MDT, CESSNA 402B, N25BH, CONTACTED GROUND CONTROL (GC) AND WAS CLEARED TO TAXI FROM THE EXECUTIVE HANGAR TO RUNWAY 28R FOR TAKEOFF. ABOUT 1 MINUTE LATER, PIPER PA-34, N3408Q, CONTACTED GC AND WAS CLEARED TO TAXI FROM THE REGIONAL HANGAR TO THE DEPARTURE RUNWAY. DARK NIGHT CONDITIONS AND RAIN PREVAILED AT THE TIME. AS THE CESSNA WAS PROCEEDING EASTBOUND ON THE PARALLEL TAXIWAY TO RUNWAY 10L/28R, THE PA-34 WAS EXITING AN ADJACENT RAMP AREA (WHERE OTHER AIRCRAFT WERE PARKED). THE TWO AIRPLANES CONVERGED AT THE TAXIWAY INTERSECTION, BUT NEITHER PILOT SAW THE OTHER PLANE IN TIME TO AVOID A COLLISION. THE CESSNA'S LEFT WINGTIP/FUEL TANK WAS SLASHED OPEN BY THE PA-34'S RIGHT PROPELLER, WHICH RESULTED IN A FUEL SPILL AND SUBSTANTIAL DAMAGE TO THE CESSNA'S LEFT WING; THE PA-34'S RIGHT WING RECEIVED MINOR DAMAGE. INVESTIGATION REVEALED THAT GC DID NOT PROVIDE ANY ADVISORIES AFTER THE INITIAL TAXI CLEARANCE; AN ALARM (CAUSED BY AN EQUIPMENT FAILURE) DISTRACTED THE TOWER CONTROLLER(S), WHO NEVER VISUALLY IDENTIFIED THE PA-34.
On April 7, 1995, at 2123 hours mountain daylight time, N25BH, a Cessna 402B, operated by American Check Transport, Denver, Colorado, collided on the ground with N3408Q, a Piper PA-34-200T, operated by Regional Express, Pocatello, Idaho, as both airplanes were taxiing for takeoff from the Boise Air Terminal in Boise, Idaho. The Cessna 402B was substantially damaged and the Piper PA-34-200T sustained minor damage. The airline transport rated pilot in the Cessna 402B, the sole occupant, was not injured. The commercial pilot in the Piper PA-34-200T, the sole occupant, was not injured. Visual meteorological conditions prevailed and instrument flight rules flight plans were filed for both flights. Both airplanes were being operated under 14 CFR 135 as on-demand domestic cargo flights. Both twin-engine airplanes were taxiing for takeoff from the Boise Air Terminal at the time of the accident. According to both pilots, the Cessna was taxiing eastbound on taxiway Alpha as the Piper was turning onto the same taxiway from the north. The Cessna's left wing fuel tip tank entered the propeller arc from the Piper's right engine and was slashed open, spilling fuel. Seven slashes, each about one inch in width and 20 inches in length, were uniformly spaced along the entire side of the fuel tank. There was no fire. The right wing tip of the Piper sustained minor damage. According to FAA Air Traffic Control (ATC) tower personnel at the Boise Air Terminal, a lightning strike caused an electrical power outage at the control tower at 2059. About ten seconds later, auxiliary power was available, and most of the equipment was back on line. At 2103, main power was restored to the tower; however, the radar computer and voice recording systems remained inoperative. An airways facility technician was not on duty at the time of the power outage and was later called in to service the inoperative equipment. No voice recordings at the time of the accident were available due to the equipment failures caused by the lightning strike. According to ATC personnel at the Boise Air Terminal, a reconstruction of the events leading to the accident was produced. The reconstruction was "... based upon controller statements and interviews with all personnel involved...." According to the ATC reconstruction, the pilot of the Cessna 402B contacted Boise Ground Control and requested clearance to taxi from the Executive Hangar for departure about 2121. The Executive Hangar is located north of the center point of the Boise Air Terminal and to the west of the control tower. Ground control instructed the Cessna pilot to taxi to Runway 28R. About one minute later, the pilot of the Piper PA-34-200T contacted Boise Ground Control and requested clearance to taxi from the "south side." Ground control instructed the Piper pilot to taxi to Runway 28L at the intersection of his choice. At 2123, the Cessna pilot contacted Ground Control and stated that he "hit the Piper." About 8 minutes after the accident, the voice recorders were restarted. This was verified via an aural examination of tower tapes. According to the FAA ATC ground controller on duty at the time of the accident: [The Cessna pilot] called ready to taxi. I told him to taxi to runway 28R. [The Piper pilot] called ready to taxi southside. I told him to taxi to runway 28L, intersection of his choice. I saw an aircraft taxiing from the area of the Western Express hangar, but couldn't see anyone taxiing from the southside. I used the FDIO to change N3408Q to TN3408Q. I then went to the north side of the tower cab, then the southeast corner of the tower to find an alarm that was ringing. [The Cessna pilot] said he had hit a Piper on the taxiway. Further investigation revealed that the ground controller utilized "less than 30 seconds to use the FDIO, and just a few seconds to realize that it was the tape alarm that was ringing." These distractions occurred about the time of the accident. No advisories were provided to the pilots of either airplane by the ground controller after taxi clearance was given. According to the pilot of the Cessna 402B: As I was approaching [taxiway intersection] A5 on the parallel taxiway I was unaware of any other aircraft on or approaching the taxiway. As stated above, parked aircraft parallel to the runway (10L-28R) I believe partially blocked my view of the approaching [Piper] Seneca from the ramp in addition to a rain covered windscreen. My scan just prior to the collision was to the right, as I was checking for any aircraft exiting from the active 28R runway. As my scan returned to the front of my aircraft, I noticed an airplane (Seneca) at my approximate 9 o'clock position. The Seneca was just turning onto the parallel taxiway at approximately a 45 degree angle to my aircraft. At this time our wingtips contacted with my left wing over the Seneca's right wing. The Seneca's propeller tips opened up my airplane's left tip fuel tank as I passed. I am estimating my speed at 15 [miles per hour] which I believed was a safe speed considering I could see no other aircraft on or near the taxiway and was not advised of any traffic near my taxi route. According to the pilot of the Piper PA-34-200T: I switched to tower frequency and called for taxi clearance. The tower controller stated "TN3408Q, taxi runway 28R intersection of your choice.".... Then I proceeded south on taxiway "Alpha S." It was raining and I could see lightning in the distance east/southeast. It was hard to see the yellow taxiway centerline. I turned left onto taxiway "Alpha." As I was converging with the taxiway centerline I suddenly noticed a light out of the corner of my eye. Not knowing what it was I stopped on the taxiway. Seconds later to my disbelief a 400 series Cessna collided with my right wing. In response to statements provided by ATC personnel indicating that the Piper pilot was given taxi clearance to runway 28L, not runway 28R, the Piper pilot stated: Had I been given clearance to runway 28L, I would have inquired of ATC as to the reason why 28R was unavailable. The reason that I would have asked the controller is that in order to taxi to runway 28L, one must taxi across runway 28R and then eastbound to the runway end, requiring more time and distance to taxi. This type of clearance also would have enabled me to cross runway 28R (FAR 91.129i). This would have prompted another question to the controller regarding which taxiway he would like me to use to cross runway 28R. The Piper pilot also refuted ATC controller statements that indicated the Piper pilot stated he was "southside" at the time of his taxi request. The Piper pilot stated that he did not say "southside," but "the Regional Hangar," just as he had always done. The Piper pilot stated that there was no reason why he would have stated "southside," because the Regional Hangar is on the north side of the field next to the control tower. The Piper pilot further stated that the ground controller may have thought he heard "southside" because another group of Piper cargo airplanes operate from there. According to meteorological observations and pilot statements, the accident occurred in dark night conditions during periods of rainfall and gusting wind conditions.
FAILURE OF BOTH PILOTS TO PERFORM ADEQUATE VISUAL LOOKOUT DURING TAXI, AND THE GROUND CONTROLLER'S FAILURE TO IDENTIFY THE POSITION OF THE PIPER PA-34 BEFORE ISSUING TAXI INSTRUCTIONS. FACTORS RELATING TO THE ACCIDENT WERE: DECREASED VISIBILITY DUE TO DARKNESS AND RAIN, PARTIAL FAILURE OF ATC EQUIPMENT DUE TO A LIGHTNING STRIKE, AND DIVERTED ATTENTION OF ATC PERSONNEL DUE TO THE PARTIAL FAILURE OF ATC EQUIPMENT.
Source: NTSB Aviation Accident Database
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