Noob question. Differential thrust to 'maneuver' the B2 would make sense given that it is a huge aircraft and not very maneuverable.
My sources tell me that the B-2 is more maneuverable than publicly perceive and officially acknowledged. The flying wing design is inherently unstable to start. But for what we are talking about, the reason why for 'penetration mode' the B-2 would employ the less efficient asymmetric engine thrust to change heading is to reduce the odds of potential rise in RCS by not using or minimizing flight control surface deflections.
The B-2 could 'bank' to turn. Or use 'split rudders' to create asymmetric drag on one wing tip to change heading. Or use asymmetric engine thrust but this would be less efficient since the engines are not as far apart as the 'split rudders' on the wing tips. Using asymmetric engine thrust may be less efficient and may require longer time to effect a heading change, but it is the mode that offer the highest odds of preserving its low RCS while traversing hostile airspace.
But the F-22 and F-35, what advantages can it hold with that very slow turning maneuver? Would it make make sense that the aircraft turn rapidly, create a 'blimp' on the radar and assume the VLO path 'disappearing' again?
I will clarify.
What I meant to explain was more the flight control system's ability to couple itself with the ECM to preserve the aircraft's RCS.
But first, I must show some of the modern flight control system's features...
Flying the F/A-18F Super Hornet
The first demonstration involved the virtual speedbrake effectiveness and handling in this configuration. The F/A-18A-D, like the F-15 series, employs an upper fuselage hydraulically deployed speedbrake. The Super Hornet has no such device, yet achieves the same effect through what can only be described as digital magic. The speedbrake function is produced by a balanced deployment of opposing flight control surfaces, generating drag without loss of flight control authority or change in aircraft pitch attitude.
Dave demonstrated the speedbrake function, and I was asked to observe over the shoulder and in the mirrors the raised ailerons, lowered trailing flaps, raised spoilers and splayed out rudders. Deceleration is smooth and there is no observable pitch change.
At Mach 0.63 Dave invited me to fly another 360 aileron roll, to observe that the aircraft retains considerable control authority despite the fact that the rudders are splayed out, and the ailerons, spoilers and flaps are generating balanced opposing pitching moments. I applied roughly 1/2 stick input and the aircraft very cleanly rolled through 360 degrees at about 90 degrees/sec roll rate. I commented on the lower roll rate and Dave observed that we were significantly slower, he then proceeded to demonstrate the roll again with a full stick input, producing around 180 degrees/sec with a slight overshoot on recovery. The aircraft feels very stable throughout the manoeuvre and there is no observable change in control forces or control input response by the FCS.
The F-18 have no dedicated speedbrake device. Instead, if the pilot engage the 'speedbrake function', the FLCC will coordinate the appropriate flight control surfaces deflections to create as high drag as possible while maintaining complete stability, and even if the pilot want to maneuver when these surfaces are deflected to create high drag.
That is the flight control laws.
For the B-2, F-22, and F-35, we coupled their FLCS to the analysis inputs from the ECM. What the ECM does is to analyze all seeking radars regardless of source directions, determine the signal with the highest threat potential, usually based upon signal strength, then send that analysis to the FLCC. The FLCC then determine the best aspect angle to present to that threat direction with the lowest possible RCS after it has taken into consideration other mission requirements such as final target location, altitude, and speed. Just like how the F-18's flight control laws maintained stability while the aircraft is under high drag condition for speedbrake, the B-2's flight control laws strives to maintain as low RCS as possible against an EM threat.
For the F-22 and F-35, it would not be as much a hardship because they are much more maneuverable than the B-2 so yes, the F-22 could make a more rapid attitude change with a calculated risk of momentary increased RCS. In fact, the system is advanced enough that it would know when that calculated increased RCS approaches a 'danger' level and would limit a particular maneuver so as not to breach that level.
When I read this...
Raptor debuts at Red Flag, dominates skies
"The thing denies your ability to put a weapons system on it, even when I can see it through the canopy," said RAAF Squadron Leader Stephen Chappell, F-15 exchange pilot in the 65th AS. "It's the most frustrated I've ever been."
I have a pretty good guess at how advanced that capability really is. The aircraft is in a dogfight and can still attempt -- quite successfully -- to limit its RCS exposure to the enemy based upon its analysis of the enemy's radar. And did it without hindering the pilot's flying.
None of this is possible without the appropriate advances in control hydraulics, avionics hardware, and elegant flight control laws codes.
