USAF Suspects Carbon Monoxide in F-22 Grounding

The prolonged grounding of the U.S. Air Force's F-22 Raptor fleet may be due to carbon monoxide entering the cockpit via the aircraft's oxygen system, two sources said.

Investigators say carbon monoxide may have caused the grounding of the F-22 fleet. The gas generated by the planes' jet engines may have gotten into cockpits at a base in Alaska, where pilots often start the engines inside a hangar before takeoff. (U.S. Air Force)

Service leaders grounded the stealthy twin-engine fighter May 3, after 14 incidents when F-22 pilots suffered "hypoxia-like symptoms."

Air Force officials initially suspected a problem with the aircraft's On-Board Oxygen Generation System (OBOGS), but that is looking less likely, the sources said.
Instead, investigators now suspect that carbon monoxide generated by the plane's jet engines is getting into the cockpit.
Part of the problem may be the procedures used at Elmendorf Air Force Base, Alaska, where most of the known incidents have occurred. Because of the harsh climate, pilots often start their jet engines inside a hangar before taking off. Investigators suspect that exhaust gases are getting trapped in the building and subsequently sucked back into the engines, where they enter the bleed air intakes that supply the OBOGS, sources said.
The design and placement of the intakes, which are located within the engines' compressor sections, are fairly standard for jet aircraft.
There is no immediate fix in sight, sources said.
Asked for comment, an Air Force spokesman said he had no further information at this time.
"The safety of our aircrews is paramount, and the Air Force continues to carefully study all factors of F-22 flight safety," said Maj. Chad Steffey.
However, a July 21 press release says Air Force Secretary Michael Donley has ordered the service's Scientific Advisory Board to conduct a "quick-look study" of "aircraft using on-board oxygen generation systems."
One aviation safety expert said that if the hypoxia is being caused by carbon monoxide in the cockpit, the gas is likely being generated by the plane's engines.
"I would think that it has something to do with exhaust flow somehow getting into the oxygen generating system," said Hans Weber, who sat on the U.S. Federal Aviation Administration's Research, Engineering and Development Advisory Committee, and is president of Tecop International, a San Diego consulting firm.
Even a small amount of the colorless, odorless gas can have serious effects, Weber said.
"It doesn't take a large concentration of carbon monoxide to start affecting people, making them ill - and not just ill but really diminishing their ability to perceive anything."
Weber said the difficulty of the fix will depend on the problem.
If the carbon monoxide is being ingested because the engines are being started in confined spaces, a fix could be as simple as moving the jet outside, Weber said. If the engine must be started inside the hangar, the startup of the oxygen system might be delayed until the jet is out in the open, he said.
But if dangerous levels of carbon monoxide are entering the cockpit despite these changes, the Air Force might have to add bulky cartridges or scrubbers to the life-support system, he said.
The U.S. Navy has had similar problems with the OBOGS on its F/A-18 Hornet, which sucked carbon monoxide into its oxygen system during carrier operations.
Between 2002 and 2009, Hornet aviators suffered 64 reported episodes of hypoxia, including two that killed the pilots, according to the July-August 2010 issue of "Approach," a Navy Safety Center publication.
Some 77 percent of the incidents happened in single-seat Hornets, which saw 3.2 incidents per 100,000 flight hours. The two-seat version saw 1.7 incidents per 100,000 flight hours.
According to Navy documents, "Prolonged exposure to jet engine exhaust while sitting behind another aircraft waiting to take off and operating with low bleed air pressures can result in carbon monoxide (CO) breaking through … into the pilot's breathing gas."
The Navy modified the planes' OBOGS to fix the problem, has had no recent similar incidents, and is not currently investigating the systems, Naval Air Systems Command officials said.

U.S. Navy: Tests Show Fire Scout Improvements

More than a thousand hours of flight time carried out this year by deployed Fire Scout unmanned helicopters is evidence that the system is working through its developmental problems and showing itself able to deliver a reliable reconnaissance and surveillance capability, the program's U.S. Navy managers said.

Three Fire Scout unmanned helicopters sit ready for shipment from Maryland to Afghanistan on April 13. Fire Scouts have performed better on deployment than in tests, program managers claim. (Kelly Schindler / U.S. Navy)

"Since May 21, we've got over 718 hours of flight time in Afghanistan," said Capt. Patrick Smith, the Navy's Fire Scout program manager at Naval Air Station Patuxent River, Md. "We have a monthly goal of 300 hours, and in June we hit 307. In July, we're tracking toward 375 hours. Our reports back from our U.S. and allied customers have been very, very favorable. And this is why I would call all the work done in early 2011 a success. The proof is in the pudding with what we're doing in Afghanistan."

Two Fire Scout systems, including six aircraft and their control units, were sent to Afghanistan in April and May at the request of combatant commanders. Another system with two aircraft has been deployed to the Mediterranean Sea and Horn of Africa region aboard the frigate Halyburton.
"We've put over 435 hours of flight time from USS Halyburton," Smith said, despite the June 21 loss of one of the aircraft over Libya. A replacement aircraft was soon sent out to the frigate, he added.
The reliability of the MQ-8B Fire Scout was recently called into question by an "early fielding report" prepared by the Pentagon's Office of the Director, Operational Test and Evaluation (DOT&E). The report, which relied on data and observations completed this spring, claimed the control data link between airborne drones and their ground-based controllers was "fragile," and that the Navy's test program was not realistic or complete.
The Navy plans to buy up to 168 Fire Scouts from Northrop Grumman to operate from ships at sea. The program is still in its test phases, and is not expected to be declared operationally effective until 2013.
The DOT&E report chided the program for an inability to provide a "time-sensitive" asset, and claimed that half the missions flying from the Halyburton were unsuccessful.
"The deployment had two purposes," Smith said. "Integration with the ship to support anti-piracy and maritime operations, and as a proof of concept with our special operations forces in supporting sea-based intelligence, surveillance and reconnaissance operations.
"We've had some fantastic collection of data," Smith said. "We've had very good reports from the customers."
Smith did not dispute the DOT&E report's findings that the early spring tests at Webster Field in southern Maryland were difficult.
"We were surging to meet the Afghan deployment," he said. "We were able to prove out all the hot weather changes that were incorporated. All the payload issues. And train the crews.
"We were not able to execute a major scenario that would truly simulate what they would see in Afghanistan. We were able to do it in parts, but not altogether."
Among the problems, he said, were range limitations, scheduling issues, and the availability of aircraft and people.
"We were also packing up the systems to ship them to Afghanistan," said Cmdr. Manny Picon, the program's military lead.
"We have a bit more hindsight now than was available then they wrote the report," Smith said. "The big thing we're tying to get out is we understand the issues. We've had issues with the data link as reported in the early fielding reports. We look at the flight hours as more of an indicator as to how we've been able to produce."
A well-publicized event last year when a Fire Scout headed for Washington after its data link was lost was due to a software problem that's been fixed, Smith said. Reliability has not been a significant factor on the deployed systems.
"With Halyburton and in Afghanistan, we've not seen similar behavior, losing the links, that we saw at Webster," Smith said, nor have there been major problems in restoring lost links. "Yes, they've had dropped links, but it has not impacted missions. It's been restored and missions have continued. I would classify them as minor interruptions, as you'd have with any radio system. Our datalink reliability is in the high 90 percentages."