New tail-end images of the first B-21 bomber undergoing engine runs and taxi tests outside Northrop Grumman’s facilities in Palmdale, Calif. show vertical features that have industry experts scratching their heads regarding some prominent elements.
The new photo, posted on Reddit by user Folding_White Table, shows two vertical features rising from the B-21’s upper midsection.
The two vertical armatures rise from just above the wing root of the blended wing body on both the port and starboard side, just above where the engine core or cores are likely placed. It’s unclear from the photo whether they are symmetrically positioned on the aircraft.
Based on previous photos, the vertical features are retractable.
At least one of the armatures was visible in an earlier, first view of the B-21’s aft deck, which circulated online in October. However, the angle of that photo made it hard to determine whether it was part of the aircraft or a background object.
This is the first look at the new B-21 Raiders rear-end.
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In a Reddit post, u/Folding_White Table said the photos were taken from the intersection of 40th Avenue East and Avenue N in Palmdale, right at the fence line of Northrop Grumman’s end of Air Force Plant 42. The photographer said the spot offers a “perfect view of runway 25/7, 22/4 and Site 4,” on the closest public road to Northrop’s facilities.
Industry experts asked to comment on what the objects might be—and speaking strictly on background, given the sensitive nature of the B-21—offered a range of speculation about the verticals.
A common interpretation is that the vertical armatures are coverings for auxiliary air intakes in the open position and are extended to allow more air into the engines for ground operations.
However, two experts disputed that, saying the armatures may be too far back on the aircraft and too slender to serve that purpose efficiently. One also noted that the armatures are “unusually tall” for such a purpose and so thin that the opening they putatively cover might not be big enough to supply the necessary air.
The verticals also appear to be triangular and pylon-shaped, rather than flat.
Experts ruled out that the verticals are antennas or sensors, as they would ruin the B-21’s stealthy shape if extended during an operational mission. They also discounted that they are extendible “saber drains” for venting fuel, as they are too far forward, and fuel vents are typically positioned at the aircraft’s tail.
Another possibility is that the features are there to disrupt a ground-based sensor from learning something about the B-21’s radar cross-section. The stealthy F-117 and F-35 both have a removable, faceted device that makes them more visible to air traffic controllers and increases their radar cross-section. On those aircraft, the objects are removed for combat.
On the B-2, which was manifestly the design basis for the B-21, the auxiliary air intakes are set just above and aft of the intake and give the appearance of four curved paddles, with two above each intake.
The B-21’s vertical armatures are also near—but outboard of—an unexplained dark feature on the surface of the aircraft on both sides of the central hump or spine. This feature is also visible in the forward-quarter of an image of the aircraft released by the Air Force. It is inboard of the engine inlets in that image—not in line with them—on the side of the spine.
In both the forward and rear-view images, this feature is rounded and apparently teardrop-shaped, and darker than the aircraft’s overall light gray paint color. It also seems to have depth, with a potential wedge-shaped shadow within.
One expert suggested the dark feature is a mechanism to disperse the large quantity of heat likely generated by the B-21’s avionics, hence its proximity to a potential bleed air feature from the engines.
Another speculated that this darker feature could be a bleed air vent necessitated by the B-21’s serpentine inlets, which are air tunnels that conceal the engine fan blades but potentially create an airflow bottleneck ahead of the engines. The argument against this explanation is the fact that the feature isn’t in line with the likely position of the engines within the aircraft body.
As more and clearer views of the B-21 emerge through the taxi test process, the purpose of these new features may become more apparent.