The first KC-135 Stratotanker has returned to the Fairchild Air Force Base after receiving what is known as the Block 45 upgrade, which includes cockpit instrument panel improvements and other changes intended to update the aircraft.

A base spokeswoman wasn’t sure how many of the 30 refueling aircraft currently assigned to Fairchild would undergo the modifications, but a recent article in the Fairchild Flyer, the base’s newspaper, said 22 of the base’s tankers are scheduled to receive the upgrade over the next seven years. 

Major John Chappelle, a KC-135 evaluator pilot at Fairchild, says the biggest piece of the Block 45 upgrade involves the instruments panel. 

In the planes that are being modified, what’s called a Block 40 panel, featuring mostly analog components and few digital ones, is being upgraded to a fully digital liquid crystal display that is said to improve the aircraft’s ability to relay information to the flight crew. 

“The display has been combined onto one digital screen, rather than several smaller gauges,” says Chappelle. “It’s a newer system that brings weather radar and other data up on screen. Having that information all in one place is advantageous for situational awareness.” 

Another change made possible through the upgrade was the replacement of the autopilot system. The new system is a modernized version that helps the aircraft respond better during air refueling. 

“A more responsive autopilot is useful when refueling because it’s more precise, and it keeps the aircraft as stable as possible during the process,” says Chappelle. 

Other updates in the Block 45 upgrade included a digital flight detector, a new radar altimeter, new navigation equipment, and several other minor changes to the interface.  

Chappelle says the Block 45 upgrades are expected to bring the KC-135s in line with modern avionics, and Air Force officials estimate the modifications will extend the life of the tankers until 2040. 

The Block 45 upgrades are completed at Tinker Air Force Base in Oklahoma City.

Chappelle says it takes about 20 hours of training to familiarize pilots with operating the new systems. 

According to Chappelle, the KC-135 can hold up to 30,000 gallons of fuel and can dispense from 1,000 to 6,000 pounds of fuel a minute, depending on the aircraft being refueled. 

While some bases are beginning to use the new KC-46 Pegasus for air refueling, currently there aren’t enough of them to replace the KC-135 models, so the Air Force remains focused on maintaining and upgrading the older aircraft.