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April
30th, 1966.
Al White and Joe
Cotton prepared to take AV/2 past the final hurdle to having
"unlimited" status for Mach 3 flight -- a 30+ minute run at
Mach 3 to fully heat soak all systems. Shortly after
takeoff, Cotton retracted the landing gear. The nose gear
jammed into its door, and as good as things had been going,
they were going bad now. The attempt to lower the gear using
the normal hydraulic system failed. Trying the backup
electrical system, Cotton heard a "pop" as THAT system went
dead. Given the Valkyrie's long, graceful neck, and the
intake design, retracting the main gear and landing on her
belly wasn't possible -- in fact, it was so impossible that
North American had never attempted to simulate
it!
White first brought
the XB-70 around for a touch-and-go, hoping that a hard
impact on the main gear would knock the nose gear loose and
let it fall to the extended position. Even after a second
try, however, the nose gear remained jammed. At this point,
bailing out and losing the aircraft was quickly becoming the
only option.
But there was fuel to
burn away in any case, so while people on the ground pulled
out plans and diagrams, White and Cotton circled around
Edwards slowly but surely. Finally, Cotton was sent to the
back of the cockpit to open service panels and check on
things for the people below. After more than an hour of this
(and 2 hours of flying), the problem with the backup system
was traced -- hopefully -- to a circuit breaker. Now all
Cotton had to do was find a way to short circuit the unit by
closing two contacts. Of course, the Valkyrie had no onboard
toolkit -- that would have made things too simple. But
Cotton HAD brought along his briefcase with his various
notes and plans, and opening it, he found a good, thick
paper-clip. Straightening out the paper-clip, then grasping
the middle of it with a leather glove, Cotton carefully
reached in and ZAP! short circuited the breaker. As Al White
hit the switch to extend the gear, and was rewarded with the
sound of a working backup system, Cotton gratefully dropped
into his seat. As several newspapers exclaimed the following
day, a "39 cent paper-clip saves $750 million
aircraft!"
And indeed it
had.
In the landing,
however, the main gear bogies had been damaged, and would
take two weeks to repair -- although this was a tiny price
compared to losing the aircraft. Unbeknownst to everyone
involved, the loss of the AV/2 wasn't avoided, but merely
postponed a little longer.
Finally, on May 19th,
flight number 39, AV/2 flew at Mach 3 for 33 minutes, and a
total of 62 minutes beyond Mach 2.5. In just 91 minutes, the
Valkyrie travelled over 2,400 miles -- an average speed of
more than 1500 miles per hour, including takeoff and
landing! Finally, all remaining concerns about skin
separation were laid to rest. The improved methods used to
build AV/2 were more than up to the task of sustained Mach 3
flight.
After this, AV/2 flew
to test stability and control at subsonic and supersonic
speeds. On May 22nd, 1966 (exactly one year before I was
born!), AV/2 thrilled the spectators at the Armed Forces Day
show at Edwards, including a couple of supersonic passes
over the crowd.
At this point, with
all systems tested, the XB-70 program prepared to move into
Phase 2, where NASA would become much more involved, and
extensive sonic boom and handling tests would begin. New
pilots would join the program, including NASA Chief Test
Pilot Brigadier General Joe Walker, who had just wound down
the X-15 program. Not only did Walker have an "astronaut"
rating (given to any pilot who flew higher than 50 miles,
which the X-15 did), he had flown the X-15 beyond Mach 6
(4,100 mph) in level flight (a later flight by Pete Knight
with external tanks did more then 4,500 mph). Also joining
the program was USAF Major Carl Cross.
At the same time,
both Al White and Joseph Cotton would gradually ease out of
the program, with Cotton going on to test newer planes for
the Air Force, and White to work on other projects at North
American. The Valkyrie had reached her goals, and been
tested successfully. Al White had achieved his goals for the
XB-70 program.
In preparation for
Phase 2, AV/2 was refitted with even more data recording
equipment, costing more than $50 million. These instruments
would give a better look at a number of phenomena that
couldn't be thoroughly tested in a wind tunnel --
information regarding body flex, flutter, and pressure. At
the same time, NASA began setting up a large number of
ground sensors to precisely measure the effect of sonic
booms.
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