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Flight
History
(Part One)
5:30am, 21 September,
1964
Al White (Chief Test
Pilot from North American) and Colonel Joseph Cotton (USAF)
begin their pre-flight inspection of the Valkyrie. Today's
plan isn't a taxi test, or an engine run-up. White and
Cotton will lift the XB-70, the heaviest plane ever built,
into the skies above the Mojave Desert and fly from North
American's Palmdale facility to Edwards Air Force Base, the
Air Force's Flight Test Centre (AFFTC).
And this is no
ordinary flight plan! Once the Valkyrie is over Edwards AFB,
it calls for retracting the landing gear, and accelerating
the XB-70 beyond the speed of sound at 30,000 feet over the
desert. In doing so, North American Aviation will receive a
$125,000.00 bonus from the Air Force.
At 6:10, White and
Cotton climb aboard the Valkyrie to begin the pre-flight
checklist. 35 minutes later, engine number one is started
and brought up to operating temperatures. Just moments
later, in the process of starting engine number two, caution
lights go on in the cockpit indicating a failure in the
engine's cooling loop. Both engines are shut down, and a few
minutes later, the problem is tracked down to a circuit
breaker that is reset. The process of starting the engines
is begun anew at 7:14 and goes off without a hitch. Finally,
with 132,000 pounds (the weight of an SR-71!) of fuel
indicated, the XB-70 begins taxiing towards the runway. This
is a delicate affair, because the XB-70 has demonstrated a
major problem with braking at low speeds (a violent chatter
that caused the XB-70s braking distance from just 5 mph to
be 400 feet!), making manoeuvring a tedious
affair.
Finally, at 8:24, the
Valkyrie is aligned on the runway. Al White advances the six
throttles to maximum afterburner, and the XB-70 begins its
takeoff run. At 193 mph, White rotates the long neck of the
XB-70 into the air, establishing a nine degree
Angle-of-Attack for the wing. At 205 mph and 4,853 feet of
runway, the 387,620 pounds of the Valkyrie lifts into the
blue sky for the first time. Per the flight plan, speed was
held at 310 mph and the gear left down for the flight to
Edwards. No unusual handling problems occurred during this
time.
At 8:51, the XB-70
was over Edwards, and, having met up with all the chase
planes involved, Cotton retracts the landing gear. A minute
later, waiting for the retraction indicators to go "green,"
a chase plane calls out that the retraction had failed. The
right side main gear had stopped midway through the
retraction sequence.
In order to be
compact and save space, the XB-70s main landing gear used a
complex sequence of motions. From an extended point, the
wheel assembly would first rotate 90 degrees (becoming
perpendicular to the normal direction of travel). Then, the
unit would be rotated 90 degrees vertically, so that rear
set of wheels were almost touching the top of the gear's
main strut. At this point, the main gear would rotate
backward until it was level within the fuselage.
Now, however, the
right side gear had stopped after only completing the first
motion (rotating perpendicular to the direction of flight).
The chase plane reported seeing blue streaks on the fuselage
behind the gear doors, and that some kind of fluid was
continuing to leak out. A leak in the hydraulic system was
the suspected culprit, but in mid-flight, the only thing to
do was to re-extend the landing gear before a loss of
pressure made it impossible to do so. Cycled back to the
extended position, the gear locked itself back into place,
and the Valkyrie continued on her alternate flight plan,
proceeding with some low speed handling tests, which showed
stability and control to be more than acceptable -- it was
better than the B-52!
Half an hour later,
the number three engine was showing 108 percent rpm, and was
shut down. White and Cotton then proceeded to line up for
landing on the 15,000 foot runway at Edwards. Almost 110
feet in front of the landing gear, combined with the nose-up
attitude required to land the big delta wing, it was
difficult for the pilots to judge their altitude above the
runway, or the actual point of touchdown (it was not until
the tenth flight that Al White stopped using the chase
planes to call out his altitude). Aiming for touchdown 2,000
feet down the long runway, White smoothly set the XB-70 on
the ground.
Almost immediately
trouble set in. Although White and Cotton couldn't sense it,
a pressure surge in the brake system had locked the rear
wheels of the left side main gear, causing a fire. Notified
of this, White let the Valkyrie coast to a stop, using
10,800 feet of runway. Once the fire was extinguished,
repairs had to be made before the XB-70 could be taxied
away.
On October 5th, 1964,
White and Cotton again took the Valkyrie into the air, again
with the intention of achieving supersonic flight (This
time, there would be no bonus, but following this flight,
North American would be assessed penalties for each
additional flight until the XB-70 broke the sound barrier).
Following takeoff, with a chase plane on each side, the
landing gear was retracted, then lowered, then retracted
again without a problem. With the landing gear up and stowed
away, the XB-70 climbed up to 28,000 feet and accelerated to
600 mph (Mach .85) in preparation for supersonic
flight.
Here again gremlins
struck the Valkyrie. The primary hydraulic system began
losing pressure, and the XB-70 headed back to Edwards. By
the time she was on her final approach, the landing gear had
to be lowered using the emergency electrical system. The
actual touchdown on the lake bed was uneventful, and the
XB-70 rolled to a stop after 10,000 feet.
A week later, on
October 12th, 1964, the Valkyrie burst through the sound
barrier for the first time, reaching a speed of Mach 1.1
before decelerating beneath the sound barrier and breaking
back through several times to check trans-sonic
stability.
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