Cessna 172 accident at California, 31 Mar 1987

Accident narrative

On March 31, 1987, about 0958 local time, a Cessna 172 and a Piper PA-32RT-300 collided in midair about one mile north of the departure end of runway 33 at Metropolitan Oakland International Airport in California. The collision occurred at an approximate altitude of 1,000 feet msl in visual meteorological conditions. Both airplanes were destroyed. The two occupants of the Cessna and the single pilot of the Piper were killed, and a security guard on the ground was seriously injured by falling debris.

**The flights**

The Cessna 172, operated by the Alameda Aero Club, was on an instructional flight from Oakland to the Livermore, California, practice area. The flight instructor had accrued 1,250 flight hours, and her passenger was a student pilot taking his second instructional flight.

The Piper PA-32, operated by North Star Aviation, Inc., was on a cargo ferry flight. The pilot had accrued an estimated 1,825 flight hours, including about 115 hours in the Piper PA-32. The flight had originated in Sacramento around 0400, departed Oakland around 0705 to offload cargo in Chico and Marysville, and was returning to Oakland to receive cargo.

**The sequence of events**

At 0944:18, the Cessna requested clearance to taxi to Oakland's runway 33. At 0954:54, the Piper reported that it was nine miles north of the airport with the current Automatic Terminal Information Service information. At 0955:15, the Oakland north tower controller told the Piper to plan on a right entry to runway 27R. At 0955:32, the Cessna was cleared for takeoff from runway 33 with a "right turn out" approved.

At 0957:33, the Piper reported that it was "over the green tank, turning downwind." The green tank was a large natural gas storage tank used as a visual reporting point for north field operations. At 0957:36, the tower controller responded, "Northstar 1950, Oakland tower, not in sight. Cleared to land runway 27 right, wind one niner zero at five.

Neither flight was given traffic advisories. No further transmissions were received. Witnesses described the two airplanes approaching each other relatively head-on and striking left wing to left wing. The airplanes spun out of control and fell to the ground. The Cessna fell into a Pacific Gas and Electric Company storage facility and caught fire, seriously injuring the guard. The Piper fell into a shallow portion of San Leandro Bay.

**What the investigation found**

The main wreckage of both airplanes was found within a 2,500-foot diameter circle. Sections of the left wings of both airplanes separated in flight and were found away from the main wreckage sites. Paint transfers and slash marks indicated the airplanes collided with a relative heading angle of approximately 45 degrees and a relative pitch angle of about 10 degrees. Radar and visibility data indicated that each airplane was within the viewing area of the pilot of the other airplane for at least 20 to 30 seconds before the collision.

The investigation examined noise abatement procedures at the airport. Previously, departing aircraft flew well to the west of the green tank. However, on February 5, 1987, the airport manager installed signs directing departing pilots to maintain a heading of 360 degrees until reaching a freeway. This new procedure caused departing aircraft to fly over or east of the green tank. Because arriving aircraft also flew east of or over the green tank, the new procedure reduced the separation between arriving and departing aircraft. The Board found that the airport manager implemented these signs without FAA approval. The FAA air traffic manager learned of the signs but did not object to them or initiate steps to remove them.

The Board also noted that the north tower Bright Radar Indicator Tower Equipment (BRITE) was taken out of service for routine maintenance about 20 minutes before the accident. The controller cleared the Piper to land without visually confirming its position and did not issue traffic advisories to either airplane. The Board believed that despite the unavailability of the BRITE, the controller should have issued traffic advisories because he knew the general direction of the Cessna's flightpath and had heard the Piper report its location.

The investigation reviewed the Piper pilot's medical history, noting he had undergone radial keratotomy surgery on both eyes in late 1985. Because medical literature was inconclusive regarding the likelihood of adverse visual effects following this surgery, the Board was unable to determine the extent to which the surgery may have adversely affected the pilot's visual acuity.

**Probable cause**

The National Transportation Safety Board determined that the probable cause of this accident was "the failure of each pilot-in-command to see and avoid the other aircraft and the failure of the local controller to perceive the traffic conflict and issue traffic advisories. Contributing to the accident was the reduction in airspace separation between arriving and departing aircraft at Oakland's north field runways caused by the failure of the FAA to exercise its authority over airspace management and the Oakland airport authority's establishment of noise abatement departure patterns without FAA approval. Also contributing to the accident was the decision to remove the BRITE radar from service while the tower was in operation."