Investigation Summary
The accident occurred as the DC-10 was conducting an ILS approach to Runway 33L. At approximately 500 feet short of the runway threshold, the aircraft struck the approach light piers located in Boston Harbor. The impact sheared off the right main landing gear and caused the aircraft to skid across the runway before coming to rest in a marshy area 3,000 feet from the threshold. The fuselage broke apart near the tail, and the left engine caught fire. The NTSB investigation highlighted a critical design issue regarding the DC-10's wheel clearance: the ILS glide slope provided minimal clearance over the approach lights, leaving very little margin for error when wind shear increased the descent rate. Furthermore, the investigation noted that the cabin floor between stations 1530 and 1850 collapsed, a failure mode similar to that seen in American Airlines Flight 96, which hindered the evacuation by jamming emergency exits and forcing passengers to exit through a break in the roof.
Final Conclusions
The NTSB determined the probable cause was the captain's failure to recognize and arrest an increased rate of descent induced by low-level wind shear. This occurred during the critical transition from automatic flight under instrument conditions to manual flight with marginal visual cues. The board also cited the minimal wheel clearance provided by the ILS glide slope for wide-bodied aircraft as a contributing factor that diminished the pilot's ability to recover.
Video Analysis
Iberia Flight 933 Aftermath Footage — Original news footage and aftermath of the Iberia Flight 933 crash at Boston Logan International Airport, including interviews with survivors and views of the wreckage.
If playback is blocked, the owner has disabled embedding — use the link above.
Airframe & Maintenance
Crew Experience
Captain
Jesus Calderón Gaztelu, age 53
First Officer
Alfredo Perez Vega, age 54
Flight Engineer
Celedonio Martin Santos, age 42
Radio Operator/Navigator
Candido Garcia Bueno, age 51
Systems & Failure Modes
ILS Glide Slope
The investigation found the glide slope transmitter provided insufficient wheel clearance (less than 20 feet) for wide-bodied aircraft like the DC-10 at the runway threshold.
Fuselage Floor
The floor between stations 1530 and 1850 collapsed upon impact, deforming seat tracks and jamming the rear emergency exits.
Interesting Facts
- 01The aircraft was only nine months old at the time of the accident.
- 02All 168 passengers and crew survived, though 16 people were treated for injuries.
- 03Only four of the eight emergency exits could be operated due to floor deformation and mechanical failure.
- 04The aircraft was written off and scrapped in 1974.
- 05The accident was the third major crash at Logan Airport within a five-month period in 1973.
Safety Actions & Advisories
A-74-77
Relocate ILS glide slope transmitter sites to provide a larger margin of safety for wide-bodied aircraft during Category I approaches.
A-74-80
Issue an advisory circular describing wind shear phenomena and emphasizing the need for pilot awareness of descent rates during autopilot transitions.
A-74-81
Modify pilot training programs to include knowledge of wind shear and proper techniques to counter its effects.