XB-70 VALKYRIE | Wake Vortex crash explained

The Valkyrie was the fastest and largest nuclear  strike bomber ever made and could fly its whole   mission at a staggering Mach 3. That is flying from New York to   LA in a little more than an hour. This was a remarkable design with   many innovations which pushed the boundaries  of aeronautics propulsion and materials.  But its history was cut short and  only two of these planes ever flew.  One of these was destroyed in a tragic mid-air  crash in 1966 while flying in close formation. A central factor in this mid-air  crash was the aircraft's wake vortex.   Let's take a closer look at this fascinating  phenomenon to understand the role it played.   Aircraft disturb the air they pass through.  In the process they churn up these horizontal mini tornadoes. This wingtip vortex is  the most energetic portion of the turbulence   but they are a small part of a much bigger wake. Even something as light as a  paper plane disturbs the air.  These mesmerizing visuals illustrate  the wake turbulence perfectly.  The plane stays up by pushing the air downwards. The bunched up air below the wing is at higher pressure. The pressure tries to equalize by curling around the tips of the  wing and this is what generates the vortex.  It is remarkable how the air is churned  up by something weighing so little.  Thanks to Elliot Seguin and Nick Schrader for  allowing the use of their captivating footage. Just imagine the immense wake  caused by more than 200 tons of air   being churned up by the Valkyrie bomber. Wake turbulence can be dangerous and violent. It  can easily flip a smaller aircraft upside down. A lot of fuel is wasted  generating wake turbulence.  There is an unavoidable energy penalty. It is the price wings pay to produce the lift to stay aloft. Short stubby wings generate the largest vortex. On the other extreme gliders achieve the smallest  vortex possible by having such long slender wings. The longer the wing the smaller the  vortex and the less energy is wasted. In this way gliders eke out every  shred of performance possible. The outside of the tip vortex rotates up. Birds fly with less effort if they tuck their wing into the upwash generated by the bird in front. Each bird passes the benefit on to the next. Before we get to the accident let us look  at the aircraft and how it came to be.  The Valkyrie was a cutting-edge  wonder from North American Aviation.  Their previous designs included  the World War 2 Mustang. The Korean War Sabre and the X-15 rocket plane.  In 1957 a contract was awarded with the  intent to build a fleet of these bombers.  Its mission was to deliver a nuclear  strike on the USSR at Mach 3.  But rapid advancements in missile technology meant the XB-70 was already obsolete before its first flight. The plan was to make it immune from Soviet defenses by flying too fast and too high. However intercontinental ballistic missiles would deliver nuclear weapons faster  cheaper and without risking pilots.  And the Soviets developed missiles that  could potentially shoot down the bomber.  And so by 1961 the XB-70  program no longer had a purpose.  Instead of cancelling the project outright  two prototypes were built to collect Mach 3   flight test data for use in the design of  future supersonic flight and propulsion.  The first prototype flew in 1964.  The second prototype was  destroyed in this mid-air crash.  In an attempt to salvage the project alternate  purposes for the plane were suggested.  These included a space vehicle launch  system and a supersonic passenger version.   But none of these ideas were realized. Sonic boom tests of the XB-70 helped the US to   decide to ban commercial supersonic flights over  land because of the distress the booms caused. This aircraft had multiple innovative  features. The windshield and nose ramp pivoted. They were lowered so the pilot  could see a head at slow speed   and raised when supersonic for streamlining.  It's wing tips folded in flight. They could be set to 25 and 65 degrees. When lowered they harnessed compression lift  from the supersonic shock wave and improved   directional stability when flying at Mach 3. Its rudders hinged with an unusual forward cant   which allowed for the finer control  movements essential when traveling so fast. A photo-shoot was requested by General Electric  to publicize five aircraft powered by its engines.  The number two prototype was the  centerpiece of this formation as   they were filmed for promotional material. For greatest visual effect the pilots were   encouraged into a tight formation by the  camera crew who were flying in a Learjet. The formation flew for 40 minutes in a  racetrack pattern over the California desert.  Chief test pilot Al White and Colonel Joe Cotton piloted the first flight of both the two prototypes. They were a regular crew of the XB-70. On this day Al White was piloting  the Valkyrie. For co-pilot Carl Cross this was his first flight in the bomber. Joe Cotton was flying as observer on the left of the formation in the passenger seat of the T-38. Cotton took the role of directing the formation. As the accident unfolded he gave Al White  feedback on the accident and damage status.  The other aircraft involved in  this crash was a F-104 Starfighter.  It was flown by Joe Walker. He  was NASA's chief test pilot.   He flew alongside the bomber to avoid the  wake. A wake forms all along the delta wing starting at the front and growing stronger all the way to the tip.  In his position alongside he could not see  where the wingtip was without craning his neck.   He could only guess how close the wing was  by using the forward fuselage as a reference. Air traffic control from Edwards Air  Force Base reported a b-58 on a speed run   at much higher altitude and posing no hazard. This radio call came 20 seconds before the collision. Joe walker may have looked up to locate the  aircraft and drifted into the wake of the bomber. While momentarily distracted his tail hit  the wingtip and he pitched up. The inside wing entered the dirty air of the vortex. It lost lift  from stalling in the steep angle of the airflow.  The stalled wing dropped from the reduced  lift which flipped the fighter upside down.   As it slid across the top of the bomber it sheared off most of the fins. The nose of the fighter was sliced off and hit  the wing. It burst into flames over the wing and went down in a huge fire trail. Walker was killed on impact. The pilot of the Valkyrie heard a loud thump. Joe Cotton called mid-air mid-air. He radioed that the bomber had lost vertical stabilizers. Without its vertical fins and  damaged wing it was mortally wounded.   The huge craft flew on straight for 15 to 20  seconds but then fell into a snap roll and   lost part of its left wing. It tumbled and  rolled into a flat spin while spewing fuel.   Al White ejected from the bomber it remains a  mystery why the co-pilot did not use his ejection capsule. It is likely the fierce g-forces from  the spinning prevented Carl Cross from retracting into his capsule. Or he was incapacitated by the  violent gyrations. The pilots had specially designed ejection capsules with clamshell doors for protection from the Mach 3 air blast. Before closing the doors the pilot had to retract  into the capsule and pull in his feet. Al White got his elbow caught in the doors but managed to  wrestle it loose before ejecting. The capsule had an inflatable cushion underneath to soften  the impact with the ground. but the cushion did not inflate because the clamshell door did not close fully from the elbow. Without the cushion Al white hit the ground very hard with a 32G impact and spent weeks recovering in hospital. Carl cross went down with the huge craft which crashed  in the Californian desert north of Barstow. This accident is routinely blamed on the GE photo-shoot  but Al White said this became an easy scapegoat. Joe walker was a top notch test pilot  he flew the x-15 rocket plane 25 times. He had flown nine chase plane  flights next to the Valkyrie.   Eight were in the 104. So he was very familiar  flying right up close like this. The photos show he was flying very close to the Valkyrie. Closer than the planes on the left. it seems inconceivable that Joe Walker with his exceptional skill and experience would collide in mid-air like this.   The length of the precision formation flying may  have been a factor. This required 40 minutes of unbroken focused concentration. Whether he became momentarily distracted while looking up into the sun to locate the b-58 or checking out something on the underbody of the bomber. But why he collided remains a mystery. This was a tragic freak accident which highlighted the dangers of wake turbulence. The learjet used by the camera crew belonged to  singer Frank Sinatra. This accident killed two top pilots and denied aviation further valuable flight test data from a highly innovative aircraft. The surviving XB-70 can be seen in  the national Air Force museum in Dayton Ohio. I hope to see you in my next video.

Channel: Mike Bell

Views: 696,006

Keywords: XB70, vortex, planes, aircraft

Id: B3bSCDYveBM

Length: 11min 20sec (680 seconds)

Published: Sat Dec 25 2021

Reddit Comments

[u/BlueWeatherGhost]

Probably the best explainer video I've seen on this infamous accident. Very well done animation.