New pictures just released by the Air Force show us the B-21 Raider in ways we’ve never seen it before. Among the photos is an incredible overhead view of the first test article B-21 approaching a KC-135 refueling aircraft for what may have been the platform’s first-ever mid-flight refueling. We also got to see the Raider from the side as it approached the tanker’s refueling boom.
There’s a good chance that we actually saw footage of this very air-to-air refueling exercise back in March, thanks to aviation photographer Jarod Hamilton. who sent Sandboxx News these videos of the same B-21, the first of two known aircraft in flight testing, refueling over California.
This new picture of the B-21 from above, in particular, gives us an incredible view of the Raider’s unusual windscreen layout, which includes two large windows up front that are oriented more up than forward, and smaller but equally unusual-looking angular windows to either side. This unusual window layout actually tells us quite a bit about the Raiders’ design priorities and how these stealthy bombers actually operate day to day.
Cockpit glass and canopies are a huge concern when it comes to designing stealth aircraft, because they often are made with right angles and radar waves can pass right through them to bounce off the non-stealth items found inside, like ejection seats and even the pilot’s helmet. In order to minimize the chances of the cockpit glass having a negative impact on the bomber’s stealth, windows are designed to be as small as possible with no radar-reflecting 90-degree angles. They’re then coated in materials like Indium Tin Oxide that prevent radar from passing through the glass, which, collectively, makes for a much stealthier crewed aircraft.
In most long-range bombing operations, the pilot or pilots onboard the aircraft spend very little time actually looking out of that glass, primarily flying at high altitudes, in pitch darkness, off of instruments alone. So, the placement and size of these windows is informed directly by the few operations pilots still need to look outside the aircraft to accomplish: namely, mid-flight refueling and checking to make sure the runway is clear while taxiing on the ground.
That’s why those large center windows are oriented more upward, rather than forward, so pilots can see the tanker they’re refueling from as they position themselves for the boom operator, leaving those side windows for checking the runway.
Above those windows on the center of the bomber’s fuselage, we can see cutouts, commonly called “ejection egress panels,” for the two-person crew’s ejection seats.
Outboard of the cockpit, we can see the B-21’s new air intakes that are much more flush with the airframe than the bubble intakes found on the B-2 Spirit; this further reduces the aircraft’s chances of being detected from the front.
Directly behind the intakes on the airframe you can just barely make out the supplemental or auxiliary pop-up air inlets. These open when the engine needs bigger gulps of air than its recessed primary intakes will allow – particularly during take-off. Once the jet is airborne, those panels seal shut again, leaving practically no gap behind to compromise the jet’s stealth.
In front of the cockpit windows, you can also see air data sensor ports that, as David Cenciotti pointed out for The Aviationist, look very reminiscent of the same ports on the B-2. These sensors help to determine the bomber’s airspeed, altitude, and vertical speed, among other things.
In the press release that accompanied these photos, the Air Force describes the B-21 as “the most fuel-efficient bomber ever built,” claiming that it consumes “only a fraction of the fuel” of legacy bombers.
“The B-21’s fuel efficiency is one of the core components of its lethality” said Air Force Chief of Staff Gen. Ken Wilsbach. “This long-range strike bomber will reduce the demand on our tanker fleet and free up assets to support the joint force. This will provide a wider range of employment options and the deterrence our nation requires.”
This can certainly be credited to the airframe’s incredibly streamlined and aerodynamically efficient design that prioritizes very high-altitude flight; but there’s also a good chance that this bomber is powered by only two engines, rather than four, as we saw in the Raider’s predecessor, the B-2 Spirit.
That might not be as big of a deal as some tend to think, however, because the latest generation turbofan engines in American service today are much more powerful and fuel-efficient than the engines found in the B-2.
The B-2 Spirit is powered by four GE General Electric F118 non-afterburning turbofan engines that each produce a maximum of 17,300 pounds of thrust, for a combined total of around 69,200, at a combined weight of 12,800 pounds.
Related: Why the B-21 Raider is much more than an updated B-2 Spirit
There have long been rumors that the B-21’s engines would be based directly on the Pratt & Whitney F135 afterburning turbofan engine found in the F-35 – which is the most technologically advanced and powerful fighter engine in service today. With the afterburners removed, a pair of these engines would produce a combined 56,000 pounds of thrust (roughly 19% less than the B-2) at roughly the same or less weight, while cutting procurement and maintenance requirements in half.
Considering the B-21 is smaller than the B-2 and will likewise carry a smaller payload, a 19% reduction in max thrust in exchange for being able to operate two engines instead of four would arguably be well worth it.
There are currently two B-21 Raiders in active flight testing. Low-rate initial production is already underway and the aircraft is expected to enter service as soon as next year. The program is progressing so well that Northrop will incur a roughly $477 million loss to increase bomber production rate and the Pentagon invested a whopping $4.5 billion to increase Northrop’s B-21 production capacity by an estimated 25%.
This investment, and the rush to field more Raiders, doesn’t seem to reflect an increased buy over the 100 bombers on order, but rather the Air Force’s confidence in the platform and their desire to get more bombers into service sooner, rather than later.
Feature Image: The B-21 Raider being refueled by a KC-135 tanker. (U.S. Air Force)
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