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What is this giant dorsal like fin on the B-1 bomber?

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posted on Mar, 6 2006 @ 11:13 AM

In the first two pics, it shows the B-1 bomber with that dorsal fin connected all the way to the tail. The two pics below shows that they don't have it. What does that dorsal fin hold? What does it do? How come the later B-1 bombers don't have it?

posted on Mar, 6 2006 @ 11:21 AM
Based on my memory it is for structural stability in 'sweep" back wing designs. F-111 is similar by less pronounced......

posted on Mar, 6 2006 @ 11:43 AM
That's one of the B-1A prototypes. A large dorsal spine was a modification fitted to the prototypes that housed a powerful ECM system designed to help them penetrate Soviet airspace if WW3 broke out.

Joe Baugher - B-1A

Despite the cancellation of the production program, the Carter administration allowed the flight testing of the B-1A to continue. Most of the effort involved the avionics, in particular the defensive systems. In addition, General Electric continued to work on improvements for the F101 engine, and most of the contractors kept their engineering teams intact. Perhaps most important, work continued in reducing the radar cross section of the aircraft. Less than a month after the cancellation, 74-0160 launched a SRAM on July 28, 1977 at an altitude of 6000 feet over the White Sands missile range. This aircraft was later modified with an advanced electronic countermeasures system mounted in a dorsal spine, and Doppler beam sharpening was added to the forward-looking radar. 74-0158 had achieved Mach 2.0 in April of 1976, and after completing its stability and control tests was placed in storage in 1978. On October 5, 1978, 74-0159 achieved a speed of Mach 2.22, the highest speed achieved during the B-1A program.

Interesting find, I never knew about this before.

[edit on 3/6/06 by xmotex]

posted on Mar, 6 2006 @ 04:32 PM
Those are pictures of the B-1A model which was cancelled by Jimmy C. When the USAF restarted the B-1 program in the mid 80’s they produced the B-1B which was a modified version of the B-1A. Obviously one of the differences is that it does not have the fin, I believe they removed it because it increased its RCS. They also removed the fin because by this time the B-2 was rolling around and they switched B-1’s role to an interim bomber because the B-2 was going to be the long range deep strike bomber.

I must say though, I do like it better without the fin.

posted on Mar, 6 2006 @ 04:58 PM

'Corus-Altman' (or similar, it's been awhile) Crosseye jamming system, fitted to Prototype numbers 3 and 4. It supposedly was repackaged in the B-1B as part of the ALQ-101 suite (this time as a long stripline type buried aperture, still in the spine...).

Crosseye works by creating a wavefront distortion that creates a steering error by mixing phase and amplitude at 180` to create the RF equivalent of a 'shakey picture' mirage type effect in some (multichannel monopulse) systems.

If you have a wide enough baseline Rx capability to get bearing discretes for the squint angle (what I'm guessing the long blade was for, orthagonally opposed to the smallest RCS axis of the jet as it was) of the relevant threat bands, you can do phase/amplitude waveform analysis to techniques-program two or more active Jx sources to either 'flip', 'creep' or 'retroflect' a given set of signal:return overlaps between each other and the target weapons in a way that creates massive threat antenna tracking errors which are subsequently fed to the missile autopilot.

The problem then being that there is still a far field shadow that many modern seeker processors can see around the edges of the jam strobe by comparing sum:difference effects in their MP tracking softeware, especially in advanced proportional autopilots. Kind of like seeing the shadow of a car back-halo'd by the very brightness of it's headlights.

Whether this is sufficient to create a HOJ type effect is debateable depending on what other things you (the victim) are doing to mess with the target LOS rate but it should be noted that the B-1B is now stripped of virtually all elements of the ALQ-101 and uses a much simpler ALE-50 based towed repeater jam system as it's principle RF defense.


posted on Mar, 6 2006 @ 05:25 PM
congratulations!. How does it feel KPI?

Informative, non aggressive, AND CONCISE"!!!

I knew you could do it.

Incidentally, Im not so great. Until this thread I never noticed that the dorsal fin had been removed from the B-1
I knew the B-1B looked different but that particular changed completely passed me by

[edit on 6-3-2006 by waynos]

posted on Mar, 6 2006 @ 09:01 PM
To me, the dorsal fin looks like an extended vertical stabilizer, but according to other posters, it holds other significance apparantly.

Shattered OUT...

posted on Mar, 6 2006 @ 09:35 PM
Wow - I didn't even know they built them like that.

I was going to guess that it was the Pentagons personal On-Star systems Antenna in case there was trouble with the aircraft.

posted on Mar, 6 2006 @ 10:22 PM
All of thing I knew just the top two B-1 Deltaboy posted is fourth B-1A

This B-1A is the fourth prototype. It was on the static at Farnborough in 1982. It's now preserved at Wright-Patterson AFB in Dayton

external image
I believe that rest of prototype of B-1A hasn't this long dosal fin, I don't think this dosal fin for aerodynamic way but maybe for electronics.
Here is a interesting phenomina:
some words introduce the pictrure maybe wrongly

76-0174 at the United States Air Force Museum. Photo taken with a 1987 Porsche 928. This was the fourth and last B1A built. It was used to test the defensive avionics package that is being used in the B1B.

[edit on 6-3-2006 by emile]

posted on Mar, 7 2006 @ 06:17 PM
wow, I don't think I've heard anything about cross-eyed jammers in about 9 years. Which also goes to say I can't remember most of what I did hear, except that it wasn't very much.

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