Investigation Summary
The accident originated from a last-minute change in departure runways. The crew originally planned to depart from runway 28L, but discovered it was closed for maintenance. They elected to use runway 01R, which was significantly shorter. Due to a series of communication errors between dispatch and the crew, the pilots believed they had 9,500 feet of runway available when the actual distance from the displaced threshold was only 8,500 feet. Furthermore, the crew increased their flap setting from 10 to 20 degrees for the shorter runway but failed to recalculate their V-speeds. They attempted to rotate at speeds intended for a 10-degree flap setting, which required more runway than was available. As the aircraft struggled to lift off, it struck the Approach Lighting System (ALS) structures at the end of the runway. Three 17-foot lengths of angle iron penetrated the fuselage, one of which impaled a row of seats and another severely injuring two passengers in the aft cabin. The impact also severed hydraulic lines for systems 1, 3, and 4. The captain dumped 180,000 pounds of fuel over the Pacific before returning to SFO. During the landing, the aircraft veered off the runway and came to rest on its tail due to a center-of-gravity shift as passengers rushed to the rear exits, causing the nose gear to lift off the ground.
Final Conclusions
The NTSB determined the probable cause was the pilot's use of incorrect takeoff reference speeds. This was the result of a breakdown in the carrier's operational control system, specifically: (1) irregularities in the collection and dissemination of airport information regarding runway closures and lengths; (2) errors in aircraft dispatching; and (3) failures in crew management and discipline regarding the recalculation of performance data following a configuration change.
Video Analysis
Bleeding Out Over San Francisco | Pan Am 845 — A detailed look at the near-disaster of Pan Am 845, where a Boeing 747 struck runway structures during takeoff and fought for survival with crippled hydraulics.
If playback is blocked, the owner has disabled embedding — use the link above.
Airframe & Maintenance
Crew Experience
Captain
Calvin Y. Dyer
First Officer
Paul E. Oakes
Flight Engineer
Winfree Horne
Relief Pilot
Wayne E. Sagar
Relief Flight Engineer
Roderic E. Proctor
Systems & Failure Modes
Hydraulic Systems
The Boeing 747 has four independent hydraulic systems. The impact with the ALS structures severed lines for systems 1, 3, and 4, leaving the crew with only system 2 and significantly degraded flight control authority.
Takeoff Reference Speeds (V-speeds)
The crew failed to update V1, Vr, and V2 speeds after changing the flap setting from 10 to 20 degrees, leading to a delayed rotation that exceeded the available runway length.
Emergency Evacuation Slides
When the aircraft tipped onto its tail, the forward evacuation slides became dangerously steep (nearly vertical), leading to 8 serious back injuries among passengers exiting the plane.
Interesting Facts
- 01The aircraft involved, N747PA, was the second Boeing 747 ever built and the first to enter commercial service for Pan Am.
- 02Two passengers were seriously injured by angle iron from the light towers that pierced the cabin floor during takeoff.
- 03The aircraft was carrying 708,002 pounds at takeoff, but the NTSB calculated the maximum safe weight for the actual runway length was only 697,400 pounds.
- 04During the evacuation, the aircraft's center of gravity shifted so far aft that it settled on its tail, lifting the nose gear into the air.
- 05After retirement in 1991, the aircraft was stored at Norton AFB; in 1999, it was disassembled for transport to Namyangju, South Korea, where it served as a restaurant. Claims that it was painted in a church livery were later debunked before it was finally scrapped in 2010.
Safety Actions & Advisories
Dissemination of Airport Information
The NTSB recommended improvements in how airlines collect and distribute temporary airport changes (NOTAMs) to dispatchers and flight crews.
Crew Training and Discipline
The accident was used as a case study to emphasize the critical need for crews to re-verify all performance data whenever a takeoff configuration or runway change occurs.