Even the Warthog: US Air Force Grounded Dozens A-10s After Hypoxia Incidents

The US Air Force temporarily grounded almost three dozen A-10 Warthog attack jets at an Arizona Air Force base in 2017 following three incidents involving symptoms of hypoxia mirroring similar mysterious hypoxia cases across the Navy and Air Force last year.

Two of the three episodes occurred in November in the air, during flights out of Davis-Monthan Air Force Base, Arizona, according to Air Force spokesman Capt. Josh Benedetti. In both cases the A-10's backup oxygen system kicked in allowing the pilots to return safely to base. A third pilot suffered from hypoxia symptoms while he was still on the ground.

The root cause of the incident that took place in the sole aircraft outfitted with the older liquid oxygen system (LOX) was later successfully diagnosed and fixed — the Warthog had issues with the oxygen regulator and cabin pressure systems. But investigators haven't yet determined the cause of the problem on the aircraft equipped with the newer Onboard Oxygen Generation System (OBOGS).

The whole fleet of 28 OBOGS-equipped A-10s assigned to Davis-Monathan had to be grounded for about a week, Aviation Week & Space Technology reported.

All combat aircraft generate oxygen for their crews while flying at altitude. The problem of pilots coming down with hypoxia symptoms has plagued US military aircraft, with similar incidents reported in recent years on the F-22 Raptor, F-35 Joint Strike Fighter, F/A-18 Hornet, the US Navy's T-45 Goshawk training jet fleet, and even the Air Force's T-6 prop-driven trainers.

Root causes of many of these incidents remain unsolved; they can vary from engines to the oxygen-generating capability of the aircraft itself.