We started out the day with a pre-mission brief that included all the jumpers and my aircrew. The jumpers then rode a bus to the jump site while we prepared the aircraft for the mission. The preflight, start up and the flight to the practice area all went without incident and we arrived for our first “stick” of jumpers.
It took us some time to climb to altitude, as we were loaded with gas and had a full cabin. Each follow-on jump went just as the one before and we soon were low on fuel and had to return to base to refuel. Once we’d refueled the aircraft and gotten a meal, we returned to the jump site for another set of lifts.
As we started our second hour of lifts, boredom set in. While we were leveling off for the jump, my co-pilot rogered my call of 13,000 feet and then I heard a very weird laugh. That caught my attention and I looked over at him to see what was so funny. What I saw wasn’t funny in the least. My co-pilot looked back at me with bluish lips and a big grin that made me wonder about hypoxia. I then pulled off my own glove to look at my nail beds, which were also a blue shade. I said that we were finished once the jumpers were away and my co-pilot looked at me, laughed and asked, “Why?”
As the jumpers departed, I took control of the aircraft, started a descent and called the ground party to notify them we were returning to the airfield for fuel and a crew change. I then contacted the operations center and arranged for another crew to go out and finish the final two hours of lifts that day.
Once we were on the ground, I pulled my crew together for a debrief and told them that once we were finished, we were all going to the flight surgeon’s office to get checked out. I explained to the flight surgeon what had transpired and he looked everyone over. Once we received a clean bill of health, we returned to the unit, where I talked with the commander and safety officer about crew limits on high-altitude flying. I recommended each crew be limited to only two lifts of 2.5 hours’ duration per day and that those flights be separated by another crew flying a 2.5-hour flight.
What had seemed a simple flight requiring little skill on the aircrew’s part took an interesting, potentially deadly turn. As in this case, the effects of hypoxia can be cumulative. Because of that, keep an eye on your crew and use situational awareness to watch for hidden hazards in each mission and flight. The composite risk management worksheet showed an overall low risk for this mission " that is, until we found good reason to elevate the risk.
Initially, we believed the risk of hypoxia was removed as long as we limited ourselves to a maximum of 30 minutes above 10,000 feet. However, the cumulative effects of repeatedly operating at above that altitude on a cold day unexpectedly increased our risk. Fortunately, we learned that lesson without having to sacrifice an aircraft and crew to pay for it.

FYI
For related reading on the effects of hypoxia and ways to help keep crews safe during high-altitude operations, check out the story “Better Air for Aircrews” online at https://safety.army.mil/knowledge_online/february2010/BetterAirforAircrews/tabid/1637/Default.aspx

Page last updated Fri July 1st, 2011 at 10:16