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B752 / CRJ7, San Francisco CA USA, 2008

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Summary
On 13 January 2008, a Boeing 757-200 and a Bombardier CL-600 received pushback clearance from two adjacent terminal gates within 41 seconds. The ground controller believed there was room for both aircraft to pushback. During the procedure both aircraft were damaged as their tails collided. The pushback procedure of the Boeing was performed without wing-walkers or tail-walkers.
Event Details
When January 2008
Actual or Potential
Event Type
Ground Operations, Human Factors
Day/Night Night
Flight Conditions On Ground - Normal Visibility
Flight Details
Aircraft BOEING 757-200
Operator United Airlines
Domicile United States
Type of Flight
Origin San Francisco International Airport
Take off Commenced No
Flight Airborne No
Flight Completed No
Flight Phase Pushback/towing
PBT
Flight Details
Aircraft BOMBARDIER Regional Jet CRJ-700
Operator SkyWest
Domicile United States
Type of Flight Public Transport (Passenger)
Origin San Francisco International Airport
Intended Destination Boise
Take off Commenced No
Flight Airborne No
Flight Completed No
Flight Phase Pushback/towing
PBT
Location - Airport
Airport San Francisco International Airport
General
Tag(s) Aircraft-aircraft collision,
Inadequate Aircraft Operator Procedures
HF
Tag(s) ATC clearance error,
Ineffective Monitoring,
Procedural non compliance,
Violation
GND
Tag(s) On gate collision,
Aircraft / Aircraft conflict,
ATC clearance error,
Aircraft Push Back
Outcome
Damage or injury No
Aircraft damage Major
Causal Factor Group(s)
Group(s) Aircraft Operation,
Air Traffic Management
Safety Recommendation(s)
Group(s) None Made
Investigation Type
Type Independent

Description

On 13 January 2008, an out of service United Airlines Boeing 757-200 and a Bombardier CRJ-700 being operated by Sky West on a United Express scheduled passenger service from San Francisco to Boise ID received pushback clearance from two adjacent terminal gates in quick sucession. Both aircraft were subsequiently damaged as their tails collided in onditions of normal night visibility. The CRJ sustained damage to vertical stabiliser, rudder and elevator and the Boeing sustained damage to rudder and elevator. None of the 60 occupants of the two aircraft or any ground personnel were injured.

Investgation

An Investigation was carried out by the National Transportation Safety Board (USA) (NTSB). It was noted that the pushback of the Boeing was performed without wing-walkers or tail-walkers. The flight crew of the CRJ700 reported that during the final stages of pushback from gate 79, they were in a stopped position with both engines running while their ground crew was in the process of disconnecting the tug when the collision occurred. Company maintenance personnel stated they were pushing the 757 back from gate 80 without the use of wing-walkers or tail walkers to relocate the airplane to another location on the airport and did not see the CRJ. A review of ATC GND tapes showed that the 757 had initially been cleared for pushback onto taxiway Alpha from gate 80. About 40 seconds later, the ground controller had also cleared the CRJ to push back onto taxiway Alpha from gate 79. The recordings showed that the ground controller did not advise either aircraft of near simultaneous adjacent pushback operations. The controller stated that he believed there was room for both aircraft to push back and did not foresee a traffic conflict.

The NTSB determined that the Probable Cause of this accident as "the company tug operator's failure to maintain clearance (of the Boeing from the CRJ)during the pushback process".

A Causal Factor was also identified as "the ground controller's failure to alert the pilot of the CRJ and the tug operator of that aircraft to the simultaneous pushback occurring from adjacent gate".

A Contributor Factor was identified as "the Boeing's pushback operation without the use of wing/tail walkers".

The Final reports OPS09IA009A and OPS09IA009B of the Investigation were adopted on 28 August 2008 and published on 31 March 2010

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