N48DL, Coast Guard Photo, from NTSB Accident Docket, Item 521814.

Eddie Sez:

The saddest part of this mishap is that the airplane was permitted to operate at 25,000 feet without oxygen equipment in the first place. The NTSB couldn't be bothered to recover the wreckage and the knowledge of what caused the mishap has sunk to the bottom of the Gulf, with the pilot. Regardless, there are many lessons to be learned:

  • Fuselage pressure leaks should be addressed immediately and repaired.

  • Oxygen supply and delivery equipment must be pre-flighted.

  • During every climb, part of your 10,000 foot check must be a check of cabin altitude. Most airplanes have a maximum cabin altitude between 6,000 and 8,000 feet. You certainly should not be above that at 10,000 feet aircraft altitude. You should know your normal cabin climb rate, typically around 300 fpm. Even if it takes you ten minutes to get to 10,000 feet aircraft altitude, you should not see more than 3,000 feet cabin altitude at that point. In any case, if it isn't where it should be, level off and investigate.

  • When troubleshooting a pressurization problem, donning oxygen quickly will not only improve your mental capabilities, it can keep you in the game if things go south quickly or insidiously.

  • When in doubt, descend.

What follows are quotes from the sources listed below, as well as my comments in blue.


Accident Report


Narrative

[NTSB Full Narrative]


Probable Cause

Figure: Cessna 421C Pilots Handbook Extract, from NTSB Accident Docket, Item 521805.

One of the saddest parts of mishaps like this is the FAA and NTSB can't be bothered to pursue them. In this case it was just an old private pilot who made a few foolish decisions in outfitting his airplane and then flying it where it wasn't equipped to be. But the real issue is that the FAA allows an airplane without oxygen equipment to operate at 25,000 feet in the first place.


See Also:

Abnormal Procedures & Techniques / Hypoxia

Abnormal Procedures & Techniques / Slow Onset Hypoxia

Technical / Oxygen


References

NTSB Aviation Accident & Synopsis Narrative, N48DL, ERA12LA290