Taken in isolation, this accident is simply the case of a crew missetting their altimeters, confusing inches with millibars. But there is much more to it than that.
— James Albright
Updated:
2017-09-15
This was another incident in a series of 13, 11 of which pointed to a problem with the Crew Resource Management culture at Pan American World Airways at the time. They were able to reverse this culture and became one of the safest airlines in the world.
There isn't much available about this crash other than the basic facts. (If you have access to more, please hit the "contact" button and let me know.) It does beg the question: how can the world's premier international airline (at the time) have pilots who would have made such a basic mistake. I think it was a part of the airline's culture: their pilots were not subject to a lot of oversight. To learn more about this culture, see: Crew Resource Management. There are lessons that still apply today.
1
Accident report
- Date: 12 June 1968
- Type: Boeing 707-321C
- Operator: Pan American World Airways
- Registration: N798PA
- Fatalities: 1 of 10 crew, 5 of 53 passengers
- Aircraft fate: Damaged beyond repair
- Phase: Approach
- Airport (departure): Bangkok-Don Muang International Airport (VTBD), Thailand
- Airport (arrival): Calcutta-Dum Dum Airport (VECC), India
2
Narrative
- Pan Am Flight 1 was a round-the world flight from Los Angeles (LAX) to New York.
- The Boeing 707, "Clipper Caribbean", was on a visual approach to Calcutta (CCU) when it struck a tree and crashed 1128m short of the runway.
- Weather at Calcutta was poor with a 400 ft ceiling and less than two miles visibility in rain.
- The crew of "Clipper Caribbean" misunderstood the pressure reported to them by air traffic control. They didn't set the QNH at 993 mb, but instead set the QFE at 29.93. This resulted in a difference of the indicated altitude of 360 feet. The airplane consequently descended below decision height with flaps extended to 50 degrees.
Source: Aviation Safety Network
3
Analysis
The existing thoughts on this accident point to QFE versus QNH as well as confusing millibars (or Hecto Pascals) with inches. The aircraft "descended below decision height" on a visual approach. I'm not sure how they came up with a 360 foot difference. We clearly don't have all the facts here.
There is a lot of missing information, but given what is said about this accident:
- 0.993 Millibars = 29.32 inches Hg
- Setting 29.93 results in an error of (29.93 - 29.32) x 1000 = 610 feet.
- VECC Elevation: 16 feet
4
Cause
What little exists "out there" points to the crew setting the wrong value in their altimeters and ending up flying below a safe approach altitude.
References
(Source material)
I don't have any primary source material on this crash. Can you help? Please let me know.