Lockheed Martin’s F-35 Lightning II has been grounded after the fifth generation fighter’s integrated power package (IPP) failed on Tuesday.
AF-4, a conventional takeoff and landing variant of the Joint Strike Fighter, was undergoing a ground maintenance run at Edwards Air Force Base in California when the IPP failed. All 20 flyable F-35s were subsequently grounded.
The Air Force Times reports that the joint programme office (JPO) suspended flight operations as “the prudent action to take at this time until the F-35 engineering, technical and system safety teams fully understand the cause of the incident.”
“Once the facts are understood, a determination will be made when to lift the suspension and begin ground and flight operations,” the JPO said.
Government and contractor teams are reviewing the incident to find out what caused the IPP to fail. The IPP functions as an auxiliary power unit, emergency power system and environmental control system. The electrical system has been the cause of a number of major incidents – in 2007 an electrical short disabled some flight controls of aircraft AA-1.
This week’s grounding is one of many to hit the F-35. In March, the F-35 fleet was briefly grounded after AF-4 experienced a dual generator failure that was traced to faulty maintenance procedures. After both generators shut down in flight, the IPP activated and allowed the F-35’s flight control system to continue functioning.
Meanwhile, the carrier-based F-35C was suspended from flying between June 17 and 23 over a software problem that could have caused flight control surface malfunctions. And in October last year, the F-35 fleet was grounded after Lockheed detected a software problem that could have caused the fuel pump to shut down above 10 000 feet.
All of the US Air Force’s fifth generation fighters are grounded as an investigation into the oxygen system aboard Lockheed Martin’s F-22 Raptor continues. The Air Force grounded its entire fleet of 165 F-22 Raptors, out of 187 on order, following a stand down from May 3 after reports of “oxygen system malfunctions” that could have caused pilot hypoxia (oxygen starvation).
There have been nine suspected cases of hypoxia during F-22 operations since mid-2008, and recently there have been 14 recorded OBOGS incidents up until the stand down.
Air Force officials say the onboard oxygen generating system (OBOGS) may have been a factor in the crash of an F-22 in November last year. Captain Jeff Haney was killed when his F-22 crashed into the ground on November 16 during a night training flight with another F-22.
Since January, Raptors had been kept at altitudes below 25 000 feet during the ongoing investigation in order to lessen the risk in case the oxygen system did indeed cause the crash. If the OBOGS failed at 25 000 feet pilots would have time to recover to lower altitudes where there is enough oxygen in the atmosphere. This is not the case when the aircraft flies at its 50 000 feet ceiling.
Late last month it emerged that F-22 pilots may have been suffering the effects of toxins ingested during flight as particulates from hot oil, burned antifreeze and propane turned up in blood samples of pilots from six out of seven F-22 bases.
Air Force officials could not say when the F-22 will return to the air.