20190720022542I

This report is #A-SW-29-19-007

During pushback from Nashville int'l airport, Nashville, TN (bna) gate C13, the cockpit crew of southwest airlines (swa) flight 1555, aircraft-N7887A, was starting engines with tow-bar connected to tug. Another company aircraft, N243WN, operating as swa flight 4580, taxied forward, at direction of ground crew (hand signals only), and collided with right wingtip aircraft N7887A. No injuries occurred and both aircraft received minor damage. Both aircraft were removed from service for repairs.

Rain was reported, and lightning was in the area at time of incident. The crew of aircraft N7887A realized their aircraft had been hit and communicated with the tow-tractor (non-verbal-signal) to tow the aircraft back to the gate (C13) for jetway access. The ground crew (wing-walkers aka marshals) were using hand signals since company policy prevented use of electronic voice equipment due to lightning being in the area. Aircraft N7887A was pushed from gate C13 after aircraft N243WN was pushed from gate C14.

Aircraft (N7887A) tug had stopped but had not yet disconnected the towbar. Aircraft N243WN began to taxi initiating a right turn away from aircraft N7887A. Shortly after beginning their right turn, the left wingtip of aircraft N243WN collided with right wingtip of aircraft N7887A. Aircraft N243WN was notified via radio of possible collision with aircraft N7887A, and returned to gate 14. No emergency evacuations were conducted

Pilot of aircraft N243WN (related report#A-SW-29-19-008) stated;

"The airplane of gate 13 had stopped for a while and there was no indication from any ground personnel that there was a clearance problem. I made the assumption that the airplane had been positioned to give us enough clearance to turn away from it as it usually is the case."

The pilot of N243WN was unaware the wingtips overlapped with gate-13-airplane (connected to the tug off gate 13), thus begin to taxi unaware there was inadequate clearances to avoid ground collision. The wingwalker (person closest to the collision point) was also a new employee (hired within past year) and was unsuccessful gaining captain's attention once he became aware of inadequate clearance (pending collision).

Operational factors, the ground crew pushed airplane from gate 13 and parked in position that company airplane (N243WN) had inadequate wingtip clearance to taxi to avoid collision. Night-time-conditions and the rain may have reduced visibility contributing to ground crew & cockpit crew (N243WN) visibility. The weather (lightning) prevented company-ramp-personnel from using their primary means of communications between the ramp personnel and cockpit crew. The company.s safety-procedures prevented verbal communications via wireless headsets between the ground crew and cockpit crew. Therefore, hand signals were being used (non-verbal-signals) as primary communications, this appears to have been the primary factor to this event.

Investigation revealed the risks associated with the pushback procedures, at bna, were acceptable, considering; one hazard was identified regarding a guide agent not being able to communicate to the same effectiviness as when headset are worn. Data did not support a hazzard of using headsets during condition (code) yellow. Corrective action of allowing headsets during condition (code) yellow was briefed and approved by the company. Implementation is contingent on rollout of new wireless headset system.

Company will follow-up with cmo once the implementation (rollout of new wireless headset system) is completed.