Let’s take another look at the air data ports and the B-2’s astro-inertial navigation system.
The US Air Force just released new close-ups of the B-2 during an aerial refueling that show some of the bomber’s signature nose sensors.
Over 30 years after its first public appearance, the Northrop Grumman B-2A Spirit is still an impressive sight. No matter how many times you’ve seen it: With its alien spaceship look, the Large Flying Wing and its peculiar system always attracts the interest of aviation enthusiasts and analysts around the world.
We’ve talked a lot about some of the Spirit’s coolest features, including the unique exhaust and “beaver tail” of the GLAS (Gust Load Alleviation System), or the rotating receptacle of the air-to-air refueling system. In September 2019, we also commented on some nice photos of a B-2 refueling from a KC-135 which offered a clear overview of the Pitot and Static ports, used for dynamic and static pressure measurement, in the front section of stealth bomber.
As explained in this article, every plane, even the smallest, requires pitot probes and static ports to determine the speed, altitude, and vertical speed of the plane. But, unlike most other aircraft, the B-2 does not carry external / protruding Pitot tubes (which would affect the aircraft’s radar cross section – RCS – making it less stealthy) and for this reason, for check, for example, the airspeed, the airplane uses static orifices embedded in the skin, in the nose, in front of the cockpit.
A new series of photographs has just been published by the US Air Force. It includes a US Air Force B-2 Spirit assigned to the 509th Bomb Wing, deployed to Iceland for a Bombardment Task Force mission, during refueling operations from a KC-135 with the 100th Air Refueling Wing of RAF Mildenhall, United Kingdom, over the Atlantic Ocean, September 6, 2021.
– DVIDSHub (@DVIDSHub) September 10, 2021
Like most photographs taken during the B-2’s Air-to-Air Refueling (AAR) operations, as well as the aerodynamic data ports integrated into the aircraft’s Hawk Beak, the images show, on the left wing of the Spirit, a circular window that covers the aircraft’s astro tracking system, which allows the aircraft to navigate in case GPS is denied.
Celestial tracking or astronavigation was the method used to calculate the position of the aircraft based on the position of a particular star or the sun before the advent of GPS. The basic approach is to aim at the sun or a particular star and calculate the position of the aircraft (missile or ship) from the angles of sight to the star. The calculation is based on very precise data on the positioning of the sun and certain reference stars at various times and locations.
While astronavigation has been largely replaced by GPS, astro-trackers are still used with some aircraft, including the B-2, which is said to operate a modified NAS-26 astro-inertial navigation system. For modern applications, the star tracking location is used to calibrate and update an inertial navigation system and, as noted, could be useful for autonomous navigations when GPS is unavailable.