RogerBW's Blog

Convair B-58 Hustler 11 March 2014

The Hustler was not just the first aircraft to be named after a pornographic magazine (this is a lie, it first flew nearly twenty years before that was thought of), it was the world's first operational supersonic bomber.

It is a product of the "high and fast" era of bomber design. Lessons from the Second World War and the early days of Korea said that bombers had to stay high to avoid gunfire from the ground, and fast so that they wouldn't be sitting ducks for defensive fighters. High altitude meant inaccurate bombing; the answer to that was nuclear weapons. So strategic bombers needed to be supersonic and high altitude, and if they couldn't be used in other roles that was acceptable.

The design process that led to the B-58 began in 1949 with a GEneralised BOmber Study issued by the USAF's Air Research and Development Command. Several manufacturers participated, and designs were winnowed out and refined, until in 1952 the Hustler was selected for full development. It first flew in 1956, and entered operational service in 1960, though as with many military projects cost and time overruns had nearly seen it cancelled several times before then.

The Hustler was designed primarily by Robert H. Widmer of Convair. It was a delta-wing aircraft powered by four J79 axial-flow turbojets, a solid military engine design intended for sustained supersonic flight (the same engine was used in the F-104 Starfighter and F-4 Phantom); it was intended to cruise at Mach 2 at altitude. It had a single defensive tail gun, though this seems to have been a hopeful gesture to traditionalism rather than a serious attempt to increase survivability. Rather than a bomb bay, it carried a jettisonable belly pod containing fuel and a single atomic bomb; the aircraft could in theory be refitted for conventional ordnance, but the full development work for this was never done.

The cockpit was advanced for its day, with warning lights and illuminated buttons, and the aircraft quickly grew a reputation as hard work to fly (in the end, 26 of the 116 produced would be lost to accident); in particular, maintaining fuel trim through changing speeds was crucial, and the automation wasn't always up to the job. Experienced crews from elsewhere in Strategic Air Command learned the basics of delta-wing aircraft with the F-102 Delta Dagger before shifting to the TB-58A training airframes. Upgrades to the design gave each crewman an escape capsule similar to what would be fitted later to the XB-70, F-111, and similar aircraft: though this in fact contributed to the loss of one Hustler, when the capsule closed accidentally, and the limited flight controls available to the pilot inside his capsule prevented him from getting home safely. Still later models included the ability to open the capsule from inside.

There was one particular failure mode of the Hustler which can fairly count as a lesson learned, since it has rarely been repeated: the supersonic spin. Assume one of the engines on the left side fails while the aircraft is in high-speed flight (not an un-heard-of occurrence). The other engines continue to run, so suddenly the right side of the aircraft is producing twice as much thrust as the left. The aircraft yaws to the left. Now the airflow to the other left engine engine starts to fail, as the incoming supersonic airstream that would normally reach it is being deflected and made turbulent by the fuselage and belly pod; that engine flames out, leaving only the right two engines running, and the rate of yaw increases. Even if the crew retain consciousness, the aircraft rapidly enters a flat spin and breaks up. The answer to this, apart from increasingly engine reliability, is to keep them closer to the centreline, so that a failure doesn't produce badly asymmetrical thrust

The Hustler's real problem, though, was that by the time it was in service it was obsolete. The Soviets looked at the "high and fast" attack profile, and built surface-to-air missiles. All of a sudden, it didn't matter if you were flying above where guns or most fighters could engage you: you were still dead.

Aircraft designs were hastily converted to operate "low and fast", hedge-hopping to reach their targets. But a Hustler at treetop level was subsonic (barely), and lost much of its already-unimpressive 1,700 mile combat radius. Adding pylons to let it carry four more nuclear weapons added flexibility but didn't help range, and Robert McNamara ordered in 1965 that the Hustler be retired by 1970. For nuclear attack, the ballistic missile was simply a better option, and the Hustler couldn't do anything else.

Had the SAM threat not materialised, there were plans for bigger and better Hustlers, most notably the B-58C, which would replace the J79s with four J58s, the same engine used on the SR-71. That aircraft was estimated to have a top speed of Mach 3, a 70,000-foot ceiling, and a range of 5,000 miles. Oddly, nobody believed this, and the project was quickly cancelled.

The Hustler was replaced, in effect, by the FB-111A, another Widmer design: slower, smaller, but cheaper, more flexible (it could usefully carry conventional weapons from the start), and in most other respects rather more capable (at least once the bugs were worked out).

  1. Posted by Owen Smith at 08:38pm on 11 March 2014

    The J79 was a great engine, so much so that it powered several US world land speed record jet cars once available as military surplus. If you have a bent turbine blade, just remove it and it's balancing partners offset by 120 degrees and you still have a working engine. I think I picked up that gem of wisdom from Art Arfons (of Greem Monster fame).

  2. Posted by RogerBW at 09:22pm on 11 March 2014

    Indeed. Just don't stick it out under the wing.

  3. Posted by John Dallman at 07:21pm on 12 March 2014

    ... Open the capsule from inside.

    Ah, the joys of explaining to designers that there needs to be a way out if the automation goes wrong.

  4. Posted by RogerBW at 09:13am on 13 March 2014

    I suspect that there was a sequencer which would close the capsule and then fire ejection charges, and nobody thought that one thing could happen without the other.

    The F-111 did this rather better by making the whole cockpit (and a bit of the fuselage behind it) the escape capsule, so there was no need to have moving parts inside the cockpit.

  5. Posted by Owen Smith at 11:30pm on 13 March 2014

    And on the F-111 you have the amusing detail that the joystick operates the bilge pump if the capsule lands on water. That's actually a design feature to be proud of, you're not carrying the weight of another handle.

  6. Posted by RogerBW at 11:47pm on 13 March 2014


    Of course, the F-111's escape capsule was bodged in to meet a Navy requirement, and presumably it was too much trouble to change things back later when the Navy stopped being interested.

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