Scroll down for behind-the-scenes footage
of the engineering of the model airplanes for the
Shortly after producers of
"The Aviator" began gearing up to make their epic film biography of Howard
Hughes, aircraft engineer and USC grad Joe Bok received his first Hollywood
contract. But when Bok, who normally builds flying drones for the military,
pored over it, he noticed an unusual stipulation: It called for not one, but two
copies of every aircraft model to be used in the film.
"I asked, 'Why two?'" recalls Bok (also correctly spelled "Bock"). "And they said, 'Because when you crash the first one, we want the second one on the runway with the propeller spinning.'"
Thus began Bok's own high-pressure epic, which started in earnest when Bok, the head of the 35-employee shop Aero Telemetry Corp., brazenly told the big-money Hollywood producers that he didn't need to build duplicates because his models wouldn't crash.
For Bok, however, the decision to forgo the obligatory Hollywood crash duplicate was a high-wire act based more on engineering intelligence than guts. Contrary to typical movie studio logic, Bok believed that radio-controlled model airplanes wouldn't crash if designed according to classical aerodynamic theory and endowed with sufficient size and weight. That's why he and a staff of six engineers decided to build models considered gargantuan in the world of radio-controlled aircraft, the biggest being a 30 ft wide, 648 lbs version of Hughes' infamous XF-11 reconnaissance plane. By most measures, even Bok's "small" models were big: His version of Hughes H-1B racer sported an 18-ft wingspan and weighed in at 450 lbs, while his scale-model of the fabled "Spruce Goose" measured 26 ft from wingtip to wingtip, and weighed 375 lbs.
"I've never seen an electric-powered model the size of his Spruce Goose," notes radio-controlled aircraft aficionado Don Hofeldt, who helped with the Goose's design.
Indeed, Aero Telemetry's models were mammoth for Hollywood, which is typically more inclined to employ brief shots of tiny models. But Bok believed that size was a necessity, especially in light of Hollywood's track record.
"I've been out here for 20 years and I know almost everyone who has ever tried to fly an airplane for a movie," says Bok, who has resided in the area since playing football for, and earning an aerospace engineering at, the University of Southern California during the 1980s. "And all the models have crashed, and they've all looked hokey."
Aerospace engineer Joe Bok brazenly told the big
money Hollywood producer that his models wouldn't
But Bok, by aiming to avoid that distinction, increased the pressure on
himself and his staff. Hollywood executives, aware of Bok's no-net approach, all
but threatened him with penalties for failure.
"They made it pretty clear that if we didn't show up on shooting day, or if we were late, or if the models didn't work, they would have $4 million worth of people and equipment standing idle," Bok recalls. "In terms of pressure, it was worse than any military customer we ever had."
Hollywood Pressure Cooker
Eight brushless dc motors spun the propellers and
lifted the 375 bulk of the Spruce Goose seaplane in Long Beach
Size notwithstanding, Aero Telemetry's tasks would have been manageable were they not salted with complexity and with nearly impossible time constraints. The project, which started with the construction of a scale model of Hughes ill-fated XF-11 reconnaissance plane, suddenly took on greater proportions after "The Aviator's" producers lost their full-scale model of the H-1 racer following a crash that destroyed the plane and took the owner's life.
Still in shock over the sudden turn of events, the producers approached Bok in August 2003 and asked if he would be willing to build an H-1 scale model in tandem with the XF-11 that his staff was already constructing.
"I told the producers, 'We've got to build it large enough so that it looks and flies like a real airplane,'" Bok recalls.
Aero Telemetry engineers hold the XF-11 model while
its engines warm up prior to test flight on Catalina
After the two parties reached an agreement, Bok and his staff temporarily set the XF-11 aside and began work on the H-1 racer, which would become the Best Picture nominee's most important scale model. Hours after the agreement was reached, Aero Telemetry's staff began making 3D CAD models of the H-1, and then quickly hogged out of a foam block of the fuselage, adding wood and carbon-fiber box spars for the wings. Bok hired "sculptors" to carve the model's features into the foam fuselage and then approached expert surf board makers to lay up the carbon fiber and resins for the composite wings. Molds for the wings were designed using a software program called Rhinoceros from Robert McNeel & Associates and airfoils were completed with CompuFoil software from SoarSoft Software.
"We had a whole army of sculptors working on it," Bok says. "Once they got it all per-fect, they began putting fiberglass over it."
In all, Aero Telemetry used six engineers, including one design engineer, one hydraulics engineer, one software engineer, and two electrical engineers. They also employed two machinists on lathes for the engines, two on Bridgeport mills, and one on a computer numerical control (CNC) mill.
Will the real Leonardo please stand up? To provide a
pilot for the radio-controlled airplanes that flew, Aero Telemetry sewed
molded Leonardo DiCaprio cases onto dolls sized to match the scale
Bok's staff, however, points to the retractable landing gears (used on both the XF-11 and H-1 racer) as the biggest design challenge. Because the models existed in a netherworld that lay somewhere between hobbyist aircraft and Cessna-sized planes, no commercial landing gear fit the bill.
"There was simply nothing out there that we could use," notes Butch Fleck, an Aero Telemetry mechanical engineer who also had experience designing landing gears for Boeing 747s and DC-9s. "We needed something generic and simple, but strong enough to stand up to the impact of landing, and that just didn't exist."
Out of necessity, the staff solved the problem by building landing gears from scratch. The H-1 racer used two 20-lb retractable wing gears that included a 2,000-psi, 24V hydraulic pump from Parker Hannifin's Oildyne Division, powered by a pair of 12V lead-acid batteries wired in series. The pump provided pressure to a 0.5-inch-diameter linear hydraulic actuator, specially machined by Aero Telemetry's staff to actuate the landing gear's wheels.
The company's engineers say that the gear design, which required four weeks of 18-hr days for two engineers and four machinists to complete, was critical. If it didn't work, the planes would have crash-landed and set filming back by months. "We had to support a hard landing and a heavy aircraft," Fleck says. "If it failed, it would have shut down the whole show."
"Tweener" Poses Power Train Challenges
Being a "tweener" project that existed between the world of commercial aircraft and hobbyist planes meant that the company's engineers also needed to develop their own power trains, including engines, electric motors, and gearboxes.
The H-1 racer model, for example, used a 360-cc two-stroke gasoline engine with twin cylinders re-bored to produce more power. Aero Telemetry's engineers also designed a special exhaust system and gearbox to squeeze more power from it.
Bok's biggest departure from conventional radio controlled modeling, however, was his use of electric motors to lift the 26 ft wide, 375 lbs Hercules or "Spruce Goose." Working with Hofeldt, a hobbyist who buys gas models and converts them to electric, the company developed a system to power the model's eight 16-inch propellers.
SolidWorks drawings done by Aero Telemetry show the
retractable landing gear, recessed in the wing...
...and the hydraulic actuator for the H-1'a main
In the end, Aero Telemetry employed eight small brushless dc motors, each powered by a tiny battery pack containing 20 nickel-metal hydride cells, thus providing enough thrust to lift the wooden model from the water in Long Beach Harbor, where its maiden flight was filmed.
"There were 300 people in costume on barges there in the harbor, watching the model take off," Hofeldt recalls. "It was an amazing sight."
Equally important, however, was the company's use of telemetry to control the planes. From the outset, "The Aviator's" producers called for the radio-controlled models to fly in areas populated by actors on the ground. Serious operational errors, especially with models weighing between 400 and 700 lbs, could have been fatal for onlookers.
"It would have been like a cruise missile coming in," Bok states.
To control the models, Bok chose military-grade transmitters and receivers, augmented by custom-designed RF sections, operating at typical military frequencies (1.4 GHz). The higher frequency was used, he says, because such frequencies are more tolerant to electromagnetic interference.
Using the in-house-designed controls, Bok says the planes exceeded all expectations. The XF-11 made its first flight on Nov. 21, 2003, followed two days later by the flight of the lumbering Spruce Goose in Long Beach Harbor.
"We didn't crash a model and didn't have so much as a glitch," he says. "We never lost control of the planes for even a split second."
Moreover, Aero Telemetry's H-1 racer made its critical flights in the California Desert on Nov. 4, 2003, a scant three months after the company reached agreement with the movie's producers. Scenes of Bok's flying model ended up playing a critical role in the movie, along with computerized models (so-called "CG" models), and static models (for ground shots). Ultimately, Bok's H-1B model followed in the historical tracks of the record-setting original by flying 160 mph, reportedly the fastest half-scale model (manned or unmanned) ever built.
"The radio-controlled model was a huge component of the success for its sequence in the movie," notes Aviator executive producer, Chris Brigham. Shots of the XF-11 and Hercules models were also used in the film, along with computerized models.
Bok expects the impact made by his company's models to have a lasting effect on Hollywood, which in the past five years has made a hard turn toward computer graphics. He says his company is now negotiating with directors Steven Spielberg and Clint Eastwood to do aircraft models for the in-the-works film "Flags of Our Fathers."
"This is groundbreaking; Hollywood has never used models this big," Bok concludes. "It's going to change the way these kinds of special effects are done, for years going forward."
Reach Senior Editor Chuck Murray at firstname.lastname@example.org
|Hughes' aircraft—A comparison of key characteristics of Hugh's actual planes versus the models
||Set speed record (352 mph)
||1,000-hp radial piston engine
||Flew 160 mph
||360 cc twin-cylinder
||Crashed in Beverly Hills
|| Two, 28-cylinder radial engines
||Flew 150 mph
||273 cc twin-cylinder
||Eight radial seaplane engines
|Spruce Goose model
|| Flew 90 mph
||Eight electric motors
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