Model Shelf: XB70 Valkyrie
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The North American XB70 was conceived at the end of the 1950s as the next generation of American long range heavy bombers. Progress in the design and building of large jet aircraft had been rapid in the decade after the end of the Second World War, when the legendary piston engined names of the conflict on the American side - the B17 Flying Fortress, B25 Mitchell and B29 Superfortress - were made obsolete by the advent of the turbojet. Almost as soon as the war ended the US had prototype jet bombers taking to the skies, and within a few more years small jet fighters were passing the speed of sound. The obvious next step was to combine the two - a supersonic bomber to strike at the heart of any enemy country, armed with a nuclear warhead. The first effort was the Convair B58 Hustler, first flown in 1956; with its triangular delta wing and crew of three it could take its lethal payload at speeds of Mach 2 (twice the speed of sound). But with the cold war arms race with the Communist Soviet Union escalating constantly during the decade even the huge leap forward of the Hustler was not enough. The US Air force needed a real monster, not just a fighter jet on steroids. In the interim Boeing had provided the giant B52 Stratofortress, an impressive but resolutely subsonic bomber, to carry the nuclear deterrent while a supersonic bomber was developed.
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The end result of North American Aviation's efforts was big - as can be seen by the size of the box and the parts laid next to an SR71 Blackbird of the same scale. Nose to tail the XB70 is as long as a Boeing 767 airliner, but with only a two man crew aboard. Underneath the wings is the huge pod containing six General Electric jets designed specifically for the XB70 - or the 'Valkyrie' as it was officially codenamed. The large housing should also have been the bomb bay for carrying a nuclear strike weapon, but that particular role for the plane never came to fruition.
Unfortunately for the Valkyrie by the time it took flight for the first time in 1964, the world's military defence picture had been radically altered from the beginning of the project by huge advances missile technology. By 1959 it was clear that jet bombers were easy targets for the new generation of SAMs - Surface To Air Missiles - and high altitude was no escape as the Soviets made clear by shooting down an American U2 spy plane from 70,500 feet in 1960. Meanwhile larger ICBMs - Intercontinental Ballistic Missiles - and smaller nuclear warheads combined for a strike weapon that made any nuclear armed aeroplane pointless. So the focus for aircraft shifted to low altitude penetration below enemy radar, something the huge XB70 was not designed for. The much cheaper, easier to operate and maintain Boeing B52 stayed as the primary heavy bomber aircraft for the US Air Force, a role it retains. Smaller, multi role supersonic 'fighter bombers' like the F105 Thunderchief and F4 Phantom became the order of the day, as the Cold War superpowers fought a proxy war of ideologies in Vietnam using conventional non nuclear weapons.
The most distinctive feature of the plane are the folding wingtips.
At high speed the outer third of the huge triangles could pivot down almost to 90 degrees vertical. The theory behind this was that the plane could then surf on its own supersonic shockwaves without lots of speed sapping air resistance, a feature called 'Compression Lift'. The sharp triangular air intakes under the fuselage were shaped to push the air into the two channels formed by the folding tips, keeping the shockwaves under the wings until they came out of the back.
Few planes ever built can match the visual drama of the Valkyrie at cruise speed with its wings folded fully down. This model comes with two sets of wing joints - one for up and one for fully down - to attach the tips to, and the natural inclination is to use the down setting. When mocked up with tape however it is crystal clear that the plane cannot sit on its landing gear with the wings lowered. Since my intention was always to display the XB70 next to the SR71 and other 1:72 planes wheels-down that meant having the wings up. Strangely though the kit does not provide two alternate sets of forward canard wings to match the main wing. In nearly every operational photograph of the plane on the ground, and when landing and taking off the two forward wings are trimmed with flaps down, but that option is unavailable in the kit. So this Valkyrie sits wheels down but canards up, as it appeared sometimes at airshows or in the service hangar.
Few planes ever built can match the visual drama of the Valkyrie at cruise speed with its wings folded fully down. This model comes with two sets of wing joints - one for up and one for fully down - to attach the tips to, and the natural inclination is to use the down setting. When mocked up with tape however it is crystal clear that the plane cannot sit on its landing gear with the wings lowered. Since my intention was always to display the XB70 next to the SR71 and other 1:72 planes wheels-down that meant having the wings up. Strangely though the kit does not provide two alternate sets of forward canard wings to match the main wing. In nearly every operational photograph of the plane on the ground, and when landing and taking off the two forward wings are trimmed with flaps down, but that option is unavailable in the kit. So this Valkyrie sits wheels down but canards up, as it appeared sometimes at airshows or in the service hangar.
Though it never made it as an operational plane the XB70 had a successful career as a high speed test bed for supersonic research, first with the Air Force and then in cooperation with NASA. Build up of high temperature was a big barrier to high speed flight for such a large plane. To stop the airframe from melting the majority of the structure was stainless steel with the then-cutting edge material titanium used where heat built up the most. Three research planes were planned, though only two were built in the end. The kit provides the markings for both; 20001, the first, and 20027, the second plane, rolled out in 1965. 20001 proved itself unable to consistently reach the target speed for the project of Mach 3 (approximately 2200 mph at altitude) because of instability. It only went that fast once. 20027 was altered in various details and was consistently able to reach three times the speed of sound. Space Shuttle apart, the two Valkyries are still by far the largest aircraft to travel so quickly.
While the original was an amazing bit of engineering, it must be said that this kit of it is not so brilliant. For such a large model the fit is pretty atrocious and plenty of filler was needed make the joints in the nose pieces and the blend between wing and fuselage suitably smooth. The with the wings placed together the two halves of the left one are off at the back by a good quarter of a centimetre. I'm not obsessive enough to fix that and it's only visible if the model is picked up and examined from underneath. The little cockpit seats also seem strangely oversized, needing shoving back at a.very steep rake to fit inside the nose.
In real life these seats were both fitted with a capsule ejector system - the pilots would not stand a chance of survival ejecting at Mach 3 without protection so the whole seat was designed to slide back into an enclosed clamshell shroud that was blown out of the cockpit. The cockpit itself bears a passing resemblance to a 1960s airliner, there's a little more room than in a fighter and the crew sit side by side. There are a few clues to the nature of the beast they were flying in the control panel; the switch to drop the folding wing tips, the six throttle levers and the Mach meter.
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One of the primary goals of the XB70 was to provide a test bed for planned SSTs- Supersonic Transports - the seemingly inevitable end result of aerospace progress in the the 1960s. The Anglo-French Concorde project was moving forward quickly by 1966 and the plane was supposed to be helping the American giants to build a supersonic airliner too. That year though, disaster struck. 20027 was destroyed in a crash over its home stomping grounds in the California desert. The cause was not a balls-out high speed run or extreme testing manoeuvre but a photo shoot. The second and faster XB70 was joined on one of it's flights by a formation of fighters for a photo op for engine manufacturer General Electric. During the formation one of the fighters, an F104 Starfighter flown by famed Nasa pilot Joe Walker strayed a little too close to the Valkyries right wing. The event was not cleared with the highest level of Air.force command and little forward planning had been done. The huge roiling air vortices barrelling off the giant delta wings caught the smaller plane, picked it up and threw it across the XB70s twin tail fins, knocking them both off and destroying the Starfighter. The larger plane carried on for a short while bit without the tail fins it gradually fell into a spin, then a tumble, then a nose up stall. Both pilots made to eject but only one made it. Captain Al White parachuted to safety but co-pilot Major Carl Cross's seat would not retract back into it's clamshell shroud. At such low speeds the complex system was defeated by the high G-forces of the tumbling plane. The incident cost two lives, one 750 million dollar plane and the jobs of several air force commanders.
The collision left only one XB70 left, the older and less refined 20001, and curtailed the useful life of the program. By the time the Concorde first flew in March 1969 the last Valkyrie had been retired and flown for the last time. In truth the plane would not have made a practical base design for a passenger SST. It was extremely expensive to run, costing millions every outing, and only flew in the benign environment of the western USA and only for around three hours at a time. The folding wings would never have been allowed in a civil airliner; had they ever stuck down the XB70 could not have landed. The pilots reported some unusual episodes of poor handling and buffeting in flight, and even the habit of the very long nose to 'porpoise' uncomfortably up and down while taxiing around on the ground. Concorde did not reach quite the same speeds, but it did it with two fewer engines, no forward canard wings for extra lift and, of course, a full load of 100 passengers and their baggage. Outwardly appearances between the two planes are similar, but looked at more closely Concorde was clearly more a sophisticated form than the Valkyrie - as to be expected as it was developed several years later.
The model at least gives a little insight into the struggles of developing such a complicated machine in the real world. One concern I had with the model is that the undercarriage would not hold the weight of the plane. To stop the whole thing tipping back on it's tail I had added a little extra ballast to the nose section but that added load on the wheels - hence the care to let the wheels set without any stresses. The wheels themselves needed painting in two colours as the original has silver painted tyre sidewalls to prevent the wheels absorbing heat in the wheelwells.
Another feature that takes time to finish with a decent result is the cockpit canopy. The age of the XB70 design is given away in the lines of the nose window. There's no rounded one piece canopy here; it's flat panels look like a cheap conservatory, but it was designed to fold down to aid pilot visibilty for landing - a useful feature also adopted by Concorde. The model gives the option of having the window in lowered position too, but since,as we've established, it can't have to its takeoff configured front wings anyway then I've kept it in its sleekest setup. Aesthetic reasons also mean that I've put the markings on for number 20001 - the only one that ended up wearing the Nasa logos after the 1966 crash- because what plane doesn't look cooler with 'Nasa' written on its tail fins?
Perhaps it's a good thing the Valkyrie never dropped bombs in anger. It can sit next to the Blackbird as another high speed plane that never fired a gun or bombed a village. In real life 20001 is in the US Air Force Museum in Ohio, as it has since it last flew in 1969, it's speed unmatched by any bomber since. Ironically the threat of the XB70 sent the Soviet Union into frenzy of spending and development making interceptors that could keep up. Hence the MiG 25 'Foxbat', introduced in the mid 1970s, a hugely expensive, massively overpowered Mach 3 fighter plane the Russians plowed piles if money into that they might have been better spending elsewhere. So, in its way, the XB70 did do it's bit for the battle during then cold war by showing what the Americans were capable of.
The collision left only one XB70 left, the older and less refined 20001, and curtailed the useful life of the program. By the time the Concorde first flew in March 1969 the last Valkyrie had been retired and flown for the last time. In truth the plane would not have made a practical base design for a passenger SST. It was extremely expensive to run, costing millions every outing, and only flew in the benign environment of the western USA and only for around three hours at a time. The folding wings would never have been allowed in a civil airliner; had they ever stuck down the XB70 could not have landed. The pilots reported some unusual episodes of poor handling and buffeting in flight, and even the habit of the very long nose to 'porpoise' uncomfortably up and down while taxiing around on the ground. Concorde did not reach quite the same speeds, but it did it with two fewer engines, no forward canard wings for extra lift and, of course, a full load of 100 passengers and their baggage. Outwardly appearances between the two planes are similar, but looked at more closely Concorde was clearly more a sophisticated form than the Valkyrie - as to be expected as it was developed several years later.
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Another feature that takes time to finish with a decent result is the cockpit canopy. The age of the XB70 design is given away in the lines of the nose window. There's no rounded one piece canopy here; it's flat panels look like a cheap conservatory, but it was designed to fold down to aid pilot visibilty for landing - a useful feature also adopted by Concorde. The model gives the option of having the window in lowered position too, but since,as we've established, it can't have to its takeoff configured front wings anyway then I've kept it in its sleekest setup. Aesthetic reasons also mean that I've put the markings on for number 20001 - the only one that ended up wearing the Nasa logos after the 1966 crash- because what plane doesn't look cooler with 'Nasa' written on its tail fins? 
There are some impressive 'What if?' Models on show online, made up to show the plane in futures that never happened; as it might have appeared if it had made it's way to Vietnam, or been a nuclear stand off deterrent, or a spy plane. Given the cost and complexity it was almost inevitable that the XB70 never made it to the front line. But what really scuppered it was it's size and inability to fly slow and low as well as high and fast. The current front line for the USAF of the swing wing B1 Lancer and B2 Spirit 'Flying wing' stealth bomber are just as useful as performing sneak raids under the radar as they are cruising to the target at high altitude.
Perhaps it's a good thing the Valkyrie never dropped bombs in anger. It can sit next to the Blackbird as another high speed plane that never fired a gun or bombed a village. In real life 20001 is in the US Air Force Museum in Ohio, as it has since it last flew in 1969, it's speed unmatched by any bomber since. Ironically the threat of the XB70 sent the Soviet Union into frenzy of spending and development making interceptors that could keep up. Hence the MiG 25 'Foxbat', introduced in the mid 1970s, a hugely expensive, massively overpowered Mach 3 fighter plane the Russians plowed piles if money into that they might have been better spending elsewhere. So, in its way, the XB70 did do it's bit for the battle during then cold war by showing what the Americans were capable of.
