Investigation Summary
The accident was traced to a structural failure in the pylon assembly of the No. 2 engine. The midspar fitting, a critical component connecting the engine pylon to the wing, failed due to fatigue cracking. Boeing had previously identified this specific fitting as susceptible to cracking and issued service bulletins (later mandated by FAA Airworthiness Directives) requiring their replacement with a more robust design. Shortly after liftoff, at an altitude of approximately 20 feet, the fitting failed, causing the engine to detach. The investigation revealed that Omega Aerial Refueling Services had ceased the required repetitive inspections of these fittings in 2003. This decision was based on a records review of the aircraft's history which indicated that a previous owner had already installed the upgraded, fatigue-resistant fittings in 1983. However, physical examination of the wreckage proved this maintenance entry was erroneous; the original, failure-prone fittings were still installed on the aircraft at the time of the crash.
Final Conclusions
The NTSB determined the probable cause was the failure of a midspar fitting susceptible to fatigue cracking that should have been replaced per an airworthiness directive. A significant contributing factor was an erroneous maintenance entry by a previous owner, which falsely stated the newer fittings had been installed, leading the current operator to terminate required safety inspections.
Photographic Evidence (1)
Video Analysis
Maintaining Lies | The Crash Of Omega Air Refueling Services Flight 70 — An analysis of the maintenance errors and structural failures that led to the engine separation and crash of an Omega Air Boeing 707 tanker at Point Mugu.
If playback is blocked, the owner has disabled embedding — use the link above.
Airframe & Maintenance
Crew Experience
Captain
Former Navy pilot and United Airlines First Officer.
First Officer
Former Navy pilot qualified on DC-10 and 707.
Flight Engineer
Former US Air Force C-141 Starlifter crew member.
Systems & Failure Modes
Midspar Fitting
A right-angle structural component that attaches the engine pylon bulkhead to the wing's forward drag support fitting.
Nacelle Droop Stripes
Visual indicators intended to show maintenance crews if the nacelle support structure has shifted or broken.
Interesting Facts
- 01The aircraft was operating as a non-military public aircraft under contract with the U.S. Navy.
- 02The No. 2 engine midspar fitting failed at the radius where the horizontal tangs merge with the center lug.
- 03Boeing had reported 45 cases of midspar fitting cracks and 3 prior engine separations before this accident.
- 04The aircraft had previously been involved in a bird strike and runway overrun at Sydney Airport on December 1, 1969, while registered as N892PA with Pan Am.
- 05Post-crash inspection confirmed the aircraft still had the original 1969-style fittings despite records claiming a 1983 replacement.
Safety Actions & Advisories
Maintenance Record Verification
Source ↗The accident highlighted the danger of relying solely on historical maintenance logs for life-limited or AD-mandated structural components without physical verification during heavy maintenance cycles.
FAA Airworthiness Directive Compliance
Source ↗The NTSB emphasized that operators must ensure physical compliance with Airworthiness Directives (ADs), particularly when acquired aircraft have complex maintenance histories involving multiple previous owners.