Lightning Rods Protect F-35 Lightnings From Lightning At Exercise Northern Lightning

There is a real risk that a lightning strike could cause a fire or an explosion if dangerous gases are not purged from the jet's fuel system.

Air National Guard

In what can only be described as the height of irony, personnel at Volk Field in Wisconsin have erected lightning rods to protect F-35A Joint Strike Fighters, also known by their official nickname Lightning II, from, well, lightning. On top of all that, this is taking place during a major joint exercise called Northern Lightning.

This year's iteration of Northern Lightning kicked off on Aug. 10 and is set to run through the end of this week. The F-35As from Vermont's 158th Fighter Wing's 134th Fighter Squadron, the first Air National Guard unit to receive the type, are not the only aircraft taking part. Air National Guard F-16C/D Vipers, as well as F-22 Raptors and T-38 Talons from the Air Force's active component, U.S. Navy F/A-18E/F Super Hornets, and L-139E aggressors from private contractor Draken International, are among the main players participating in the exercise. You can read more about Northern Lightning in this past War Zone piece.

The stunning image of five F-35s sitting underneath three lightning rods, seen at the top of this story and in full below, was taken on Aug. 11 "after a day of flying training," according to the caption. The lightning rods appear to be versions of LBA Technology, Inc's portable PLP-38-MOB model, which the Marine Corps also purchased to shield their F-35Bs from lightning strikes at deployed locations in 2018, which you can read about in more detail in this past War Zone piece.

Air National Guard

The core issue that requires the use of the lightning rods at all is the F-35's main fuel tank and the rest of the aircraft's fuel system. Unless the interior of the tank and the associated fuel lines are kept "inert," there is a well-established risk that residual fuel vapors, as well as oxygen, could build up inside. If the plane is not "inerted" properly, a lightning strike could potentially lead to a major fire or even a catastrophic explosion. There is also a risk that lightning strikes might cause damage to the components of the already much-maligned Autonomic Logistics Information System (ALIS), which the Air Force is in the process of phasing out, in the jets.

LBA Technology

An LBA PLP-38-MOB lightning rod in its deployed configuration.

Unlike a metal-skinned aircraft, the F-35's composite material structure also "does not provide inherent passive lightning protection," the Marine Corps explained when buying its lighting rods two years ago. "The lightning rods being requested are needed for deploying aircraft to any expeditionary airfield in support of combat operations or training exercises that do not support all lightning protection requirements."

The F-35s do feature Onboard Inert Gas Generation Systems (OBIGGS) that are designed to pump nitrogen-enriched air into the fuel system to prevent the buildup of these other dangerous gases. However, the reliability of this system was recently called into question after the discovery of damage to tubes that connect the OBIGGS to the main fuel tank earlier this year, which Bloomberg was first to report.

Lockheed Martin halted deliveries of F-35As to the Air Force for much of June after the issue first appeared, but subsequently determined that "it appears this anomaly is occurring in the field after aircraft delivery," according to Defense News. The F-35 Joint Program Office subsequently recommended that units institute a flight restriction that prohibited A models from operating within 25 miles of lightning or thunderstorms. 

It's unclear if this has been rescinded since then or if it also applied to the short and vertical takeoff and landing capable F-35Bs that the U.S. Marine Corps operates or the carrier-capable F-35Cs that the U.S. Navy flies. We do know that Marine F-35Bs are regularly seen with the rods in place when parked in different locales.

Even when it's working properly, there have been questions in the past about the OBIGGS overall efficacy. 

“The aircraft does not maintain residual inerting after flight for the required interval of 12 hours, which is a lightning protection requirement,” the Office of the Director of Operational Test and Evaluation had warned back in 2015 specifically with regards to the F-35B variant. “If the residual inerting cannot be improved, aircraft maintainers will be required to purge fuel tanks with external nitrogen more frequently or alternative lightning protection strategies (e.g., lightning-protected shelters), will have to be adopted.”

Regardless, it's obvious from the lightning rods at Volk Field is that "alternative lightning protection strategies" are still very much in use to help prevent lightning from blowing up the Lightnings when they're out on the tarmac.

Contact the author: joe@thedrive.com