Above and Beyond: Too Much, Too Soon
* By General Robert L. Cardenas, U.S. Air Force (Ret.) As told to James
P. Busha
* Air & Space Magazine, July 01, 2009
In 1941, When it appeared that Britain's battle against Germany might
fail, the U.S. Army Air Forces called for a bomber that could fly 10,000
miles with a 10,000-pound payload. Northrop responded with the XB-35
Flying Wing; Consolidated offered the XB-36 Peacemaker.
In 1947, my boss, Colonel Albert "Bullet" Boyd, chief of the Army Air
Forces Flight Test Division at Wright Field in Ohio, sent Glenn Edwards,
Danny Forbes, and me-"los tres amigos"-to the barren California
wasteland known as Muroc Army Air Field, along with civilian flight test
engineer Richard Smith. We shared Danny as copilot. We had all the fun
of flying, and Dick Smith had all the work of reducing our collected
data into readable form.
The YB-49 demonstrated that putting jet engines on an airframe designed
for piston engines made the aircraft faster but not better. (NASM (SI
Neg. #93-11863~A)) I was supposed to have flown the propeller-driven
version of the Flying Wing, the XB-35. But I had told Colonel Boyd that
any engineer who put a propeller on the trailing edge of a wing did not
deserve his diploma. The air flowing over the top of the wing has a
different temperature, velocity, and dynamic pressure than the air
flowing under it, so those little propeller blades had to cut through
two different air masses in microseconds, and the difference caused
flutter.
The Army Air Forces decided the XB-35 needed jet engines, so Northrop
converted two -35s to YB-49 all-jet Flying Wings. No. 42-102367 was
instrumented for stability and control; no. 42-102368 was built for
performance flight tests. In early 1948, my crew-copilot Danny and
flight engine er William Cunningham-flew no. 368 from the Northrop
factory in Hawthorne to Muroc to begin performance tests.
Early tests consisted of finding the best speed for takeoff, climb,
stall, opening the bomb bay doors, and landing. Each test had its own
set of problems-some minor, some that almost killed me. On my first
takeoff, the airplane accelerated too rapidly, causing the gear doors to
blow off. I could either pull the Flying Wing up at a high angle of
attack on takeoff or pull back on the power and wait the 90 seconds for
the gear to retract. The problem was that the jet-powered Wing was
designed around the propeller-driven XB-35, which operated at slower
speeds. Northrop had simply swapped prop engines for jets, and of course
the speed of the aircraft increased.
After leveling off, I would be rocked back and forth in my seat in
unison with the sloshing of the fuel that was stored behind me in a big
rubber bag, with no baffles, buried in the wing. I tried opening the
bomb bay doors-they were sucked right off.
Concerned about the upcoming stall tests, I consulted Paul Bikle, chief
of the Flight Test Division's performance engineering branch, who told
me I would not get a clean stall with the YB-49-I'd get a wingtip stall.
He said that unlike the airflow over a standard wing, air over the
Flying Wing would be pushed sideways, or span-wise, and as the flow
increased toward the tip, lift at the wingtip would rapidly decrease,
causing the wing to pit ch up. The split flaps were on the wingtips with
the rudders, and he advised me that I might get a full wing stall if I
were to trim the entire split flaps either up or down, rather than use
the yoke.
Along with getting the Flying Wing to stall, I also got the ride of my
life.
I leveled the YB-49 at 20,000 feet, pulled back on the throttles, and
waited for it to stop flying. Because most of the shudder you get in a
stall comes from the tail, not the wing, I knew I wouldn't get a big
shudder. Sure enough, when the tailless airplane quit flying, instead of
the normal shudder just before the nose drops, I experienced a violent
pitch forward into a negative-G tumble, which pulled my rear end out of
the seat. In a microsecond, I realized that I had no aerodynamic flow
over any control surface that would allow me to recover. It was as if
you took a nice, crisp, clean dollar bill out and let it go; it would go
spinning around its center. The engineers later called it a lateral roll
and said I had encountered inertial coupling.
Fortunately, the throttles were mounted up above my head, not down on
the console where they normally are. There were two handles, one for the
four left engines and one for the four right, just an arm's length away.
I was able to grab the left throttle and apply full power, which caused
the aircraft to cartwheel. I was thrown into an inverted spin-one thing
I knew how to get out of. I recovered at about 800 feet. After I landed,
I wrote a brief report: "This aircraft is never to be intentionally
stalled." Later that night, I went to Pancho's Happy Bottom Riding Club
for a drink.
On June 5, 1948, Glenn Edwards and Danny Forbes were killed at Muroc
while flying YB-49 no. 368. It hit the ground upside down, so flat it
didn't have much of a sideways motion. The wing areas outboard of the
engines were found 15 miles downstream. Colonel Boyd told me to finish
the tests in the other airplane.
In the fall of 1948, I flew no. 367 in a series of stability and control
tests. The YB-49 was beautiful-it was just like flying a fighter. But it
was not a bomber, and it had many deficiencies: The biggest problem was
that it was way ahead of its time, well before the advent of computers.
The sensory and response capabilities of a human were too slow to keep
up with the Flying Wing's ever-changing dynamics. I've been accused of
saying the YB-49 was unstable, but what I actually said was that it was
marginally stable about all three axes and could go unstable at
aft-center-of-gravity loadings. That's why I would not sign off on the
airplane. The YB-49 would have to wait for technology to catch up.
In November 1948, I briefed Air Force generals about my concerns. In the
audience was Jack Northrop. After I spoke, he stood and said, "I have
the highest regard for Major Cardenas and his abilities as a test pilot.
Obviously I have not been kept informed. He looked at the people he
brought with him. "It looks like Northrop has a lot of work to do," he
said. An engineer in the audience said, "You have an impossible task,"
to which Mr. Northrop replied, "General, I'm surprised you have people
in your employ who think the impossible really is impossible." That sort
of broke up the hearing.
On February 9, 1949, I was ordered to fly the YB-49 to Andrews Air Force
Base, near Washington, D.C., for President Harry Truman's air power
demonstration. We flew nonstop to Andrews in four hours and 20 minutes,
setting a transcontinental speed record. President Truman inspected the
Flying Wing and even climbed up in the cockpit. While I was showing him
the interior, he turned to me and said, "Looks pretty good to me, son. I
think I'm going to buy some." I bit my tongue and just smiled. The
president asked the chief of the Air Force, "Why don't you have this
young whippersnapper fly this down Pennsylvania Avenue at treetop level?
I want the people to see what I'm going to buy." I knew my boss was
never going to order me to fly a huge experimental aircraft at treetop
level over the heart of the nation's capital.
Well, he did.
As I dodged radio towers, I lost track of Pennsylvania Avenue along the
way. I never realized how heavily forested Washington was. All the trees
made it very hard to see straight ahead as I roared low over the city.
Toward the end of my flight I thought I was in the clear-until the big
white dome of the Capitol filled my canopy. I abruptly pulled up to
avoid smashing into it.
General Boyd sent Major Russ Schleeh out to spot-check some of the
flight data that Glenn and I had collected. After Russ made three
flights in the Wing, he confirmed our data points and concurred with our
thoughts on the YB-49. On a later flight attempt, the nose gear
collapsed out on a Muroc lakebed, destroying the last of the test
aircraft and almost killing Russ. That ended the program.
Robert Cardenas retired from the U.S. Air Force after 34 years of
service.
A police detective lieutenant by day and an aviation writer by night,
Jim Busha takes frequent breaks in his 1943 Aeronca L-3.
* By General Robert L. Cardenas, U.S. Air Force (Ret.) As told to James
P. Busha
* Air & Space Magazine, July 01, 2009
In 1941, When it appeared that Britain's battle against Germany might
fail, the U.S. Army Air Forces called for a bomber that could fly 10,000
miles with a 10,000-pound payload. Northrop responded with the XB-35
Flying Wing; Consolidated offered the XB-36 Peacemaker.
In 1947, my boss, Colonel Albert "Bullet" Boyd, chief of the Army Air
Forces Flight Test Division at Wright Field in Ohio, sent Glenn Edwards,
Danny Forbes, and me-"los tres amigos"-to the barren California
wasteland known as Muroc Army Air Field, along with civilian flight test
engineer Richard Smith. We shared Danny as copilot. We had all the fun
of flying, and Dick Smith had all the work of reducing our collected
data into readable form.
The YB-49 demonstrated that putting jet engines on an airframe designed
for piston engines made the aircraft faster but not better. (NASM (SI
Neg. #93-11863~A)) I was supposed to have flown the propeller-driven
version of the Flying Wing, the XB-35. But I had told Colonel Boyd that
any engineer who put a propeller on the trailing edge of a wing did not
deserve his diploma. The air flowing over the top of the wing has a
different temperature, velocity, and dynamic pressure than the air
flowing under it, so those little propeller blades had to cut through
two different air masses in microseconds, and the difference caused
flutter.
The Army Air Forces decided the XB-35 needed jet engines, so Northrop
converted two -35s to YB-49 all-jet Flying Wings. No. 42-102367 was
instrumented for stability and control; no. 42-102368 was built for
performance flight tests. In early 1948, my crew-copilot Danny and
flight engine er William Cunningham-flew no. 368 from the Northrop
factory in Hawthorne to Muroc to begin performance tests.
Early tests consisted of finding the best speed for takeoff, climb,
stall, opening the bomb bay doors, and landing. Each test had its own
set of problems-some minor, some that almost killed me. On my first
takeoff, the airplane accelerated too rapidly, causing the gear doors to
blow off. I could either pull the Flying Wing up at a high angle of
attack on takeoff or pull back on the power and wait the 90 seconds for
the gear to retract. The problem was that the jet-powered Wing was
designed around the propeller-driven XB-35, which operated at slower
speeds. Northrop had simply swapped prop engines for jets, and of course
the speed of the aircraft increased.
After leveling off, I would be rocked back and forth in my seat in
unison with the sloshing of the fuel that was stored behind me in a big
rubber bag, with no baffles, buried in the wing. I tried opening the
bomb bay doors-they were sucked right off.
Concerned about the upcoming stall tests, I consulted Paul Bikle, chief
of the Flight Test Division's performance engineering branch, who told
me I would not get a clean stall with the YB-49-I'd get a wingtip stall.
He said that unlike the airflow over a standard wing, air over the
Flying Wing would be pushed sideways, or span-wise, and as the flow
increased toward the tip, lift at the wingtip would rapidly decrease,
causing the wing to pit ch up. The split flaps were on the wingtips with
the rudders, and he advised me that I might get a full wing stall if I
were to trim the entire split flaps either up or down, rather than use
the yoke.
Along with getting the Flying Wing to stall, I also got the ride of my
life.
I leveled the YB-49 at 20,000 feet, pulled back on the throttles, and
waited for it to stop flying. Because most of the shudder you get in a
stall comes from the tail, not the wing, I knew I wouldn't get a big
shudder. Sure enough, when the tailless airplane quit flying, instead of
the normal shudder just before the nose drops, I experienced a violent
pitch forward into a negative-G tumble, which pulled my rear end out of
the seat. In a microsecond, I realized that I had no aerodynamic flow
over any control surface that would allow me to recover. It was as if
you took a nice, crisp, clean dollar bill out and let it go; it would go
spinning around its center. The engineers later called it a lateral roll
and said I had encountered inertial coupling.
Fortunately, the throttles were mounted up above my head, not down on
the console where they normally are. There were two handles, one for the
four left engines and one for the four right, just an arm's length away.
I was able to grab the left throttle and apply full power, which caused
the aircraft to cartwheel. I was thrown into an inverted spin-one thing
I knew how to get out of. I recovered at about 800 feet. After I landed,
I wrote a brief report: "This aircraft is never to be intentionally
stalled." Later that night, I went to Pancho's Happy Bottom Riding Club
for a drink.
On June 5, 1948, Glenn Edwards and Danny Forbes were killed at Muroc
while flying YB-49 no. 368. It hit the ground upside down, so flat it
didn't have much of a sideways motion. The wing areas outboard of the
engines were found 15 miles downstream. Colonel Boyd told me to finish
the tests in the other airplane.
In the fall of 1948, I flew no. 367 in a series of stability and control
tests. The YB-49 was beautiful-it was just like flying a fighter. But it
was not a bomber, and it had many deficiencies: The biggest problem was
that it was way ahead of its time, well before the advent of computers.
The sensory and response capabilities of a human were too slow to keep
up with the Flying Wing's ever-changing dynamics. I've been accused of
saying the YB-49 was unstable, but what I actually said was that it was
marginally stable about all three axes and could go unstable at
aft-center-of-gravity loadings. That's why I would not sign off on the
airplane. The YB-49 would have to wait for technology to catch up.
In November 1948, I briefed Air Force generals about my concerns. In the
audience was Jack Northrop. After I spoke, he stood and said, "I have
the highest regard for Major Cardenas and his abilities as a test pilot.
Obviously I have not been kept informed. He looked at the people he
brought with him. "It looks like Northrop has a lot of work to do," he
said. An engineer in the audience said, "You have an impossible task,"
to which Mr. Northrop replied, "General, I'm surprised you have people
in your employ who think the impossible really is impossible." That sort
of broke up the hearing.
On February 9, 1949, I was ordered to fly the YB-49 to Andrews Air Force
Base, near Washington, D.C., for President Harry Truman's air power
demonstration. We flew nonstop to Andrews in four hours and 20 minutes,
setting a transcontinental speed record. President Truman inspected the
Flying Wing and even climbed up in the cockpit. While I was showing him
the interior, he turned to me and said, "Looks pretty good to me, son. I
think I'm going to buy some." I bit my tongue and just smiled. The
president asked the chief of the Air Force, "Why don't you have this
young whippersnapper fly this down Pennsylvania Avenue at treetop level?
I want the people to see what I'm going to buy." I knew my boss was
never going to order me to fly a huge experimental aircraft at treetop
level over the heart of the nation's capital.
Well, he did.
As I dodged radio towers, I lost track of Pennsylvania Avenue along the
way. I never realized how heavily forested Washington was. All the trees
made it very hard to see straight ahead as I roared low over the city.
Toward the end of my flight I thought I was in the clear-until the big
white dome of the Capitol filled my canopy. I abruptly pulled up to
avoid smashing into it.
General Boyd sent Major Russ Schleeh out to spot-check some of the
flight data that Glenn and I had collected. After Russ made three
flights in the Wing, he confirmed our data points and concurred with our
thoughts on the YB-49. On a later flight attempt, the nose gear
collapsed out on a Muroc lakebed, destroying the last of the test
aircraft and almost killing Russ. That ended the program.
Robert Cardenas retired from the U.S. Air Force after 34 years of
service.
A police detective lieutenant by day and an aviation writer by night,
Jim Busha takes frequent breaks in his 1943 Aeronca L-3.
