Bevilaqua’s back-of-the-envelope calculations suggested that the drive shaft could supply a phenomenal 28,000 horsepower, enough to make the lift fan support nearly half the hovering weight of the airplane. “Several of my colleagues sat up and said ‘Holy smoke!’ ” chief engineer Rick Rezabeck recalls, “ ‘You’re going to have 28,000 shaft horsepower running through the middle of a fighter jet.’ That’s about half the level that the Navy puts through the shaft of a destroyer. So the whole question was: Would it hold itself together and could we make it mechanically and structurally sound enough so it was reliable and added up to a viable jet fighter?”
“We’re dead in the water!” For nearly a year, Boeing engineer George Bible had been experimenting with a novel composite material for the delta wing of the JSF, a project that grew out of a series of Boeing decisions to make sturdy and cost-efficient components for its new fighter.
The concept was a winner: Build the wing as a rugged, one-piece metal structure, sandwiched by two layers of composite—an upper skin and a lower skin. To make the skins more durable, Boeing would embed carbon fibers in an advanced thermoplastic resin. But no one had tried to build a wing skin 30 feet across from a single piece of thermoplastic. Now, as Bible stared at his ultrasound monitor, it was clear that the skin was riddled with bubbles.
The experiment had begun encouragingly enough. Bible’s team had spent weeks laying down sheets of carbon fiber into resin until the wing skin was 90 sheets deep but still less than an inch thick. It was then cured in a massive oven-like autoclave under high pressure, which forced the fibers to blend with the resin. Emerging from the oven, the quality of the first upper skin seemed to bode well for Boeing’s gamble. But the lower skin had a more complex shape, and patches of the material ended up sticking to the mold. One of the advantages of working with thermoplastic is that it can be “re-cooked” if defects show up in the manufacturing. Bible’s team added more release agent—similar to cooking spray—to the mold and tried again. This time the skin didn’t stick but the pressure hoses leaked, and out came the bubble-ridden mess that had distressed Bible.
Bible launched a desperate effort to make the advanced resin pay off: If he cooked the wing yet again, perhaps the bubbles would disappear. For 30 hours the team members held their breath. Gingerly, they peeled away the orange pressure bags—and Bible’s face fell. Patches were still sticking to the mold, and there were wrinkles where the resin had been compressed unevenly. Now Bible felt as if the weight of the whole JSF program was on his back. “If we don’t have a wing skin, we don’t have an airplane,” he said. “We don’t make first flight—it’s pretty much ‘game over.’ ”
As the wing-skin crew struggled, Boeing’s main design team wrestled with its own crisis. The Navy had come back with new demands for performance and weapons-carrying capability. Flight simulators revealed that, with the extra weight on its delta wing, Boeing’s airplane could no longer meet the Navy’s demands. For months, the engineers worked on various fixes. Some sparked protracted debate, notably a design for a novel tail configuration advanced by a former McDonnell Douglas engineer, Ralph Pelikan. A normal four-post fighter tail layout features a twin pair of tail surfaces. The Pelikan tail would replace this conventional layout with a striking two-post layout in which just two angled tail surfaces controlled both pitch and yaw.
In October 1998, top Boeing designers weighed the advantages and penalties of Pelikan’s design. One argued that it offered greater pitch control at high angles of attack. Then the stealth experts pointed out that two tails would have a lower radar signature than four. “We can’t afford to have any question at all over our signature,” argued Fred May. “I vote for the Pelikan tail.”
But another engineer came up with a surprising objection: Despite the fact that the Pelikan tail would eliminate the need for two control surfaces, it might actually end up heavier. The bigger hydraulic pumps and cylinders needed to operate the larger surfaces would end up adding at least 200 pounds to the design. Meanwhile, team leader Dennis Muilenberg was worried about customer perception. He believed that the JSF office viewed Lockheed’s conventional fourpost tail as a lowrisk approach. Should Boeing also go with a tried-and-true design? “On the other hand,” he added, “if we end up looking like we’re the followers and Lockheed’s the leader, it might be a strategically bad thing.”
Eventually it fell to Muilenberg to break the stalemate. Despite earlier doubts, he concluded, “We need to do something to our configuration that will give us an advantage. I think the Pelikan tail does that. We’re going to have to work the hell out of weight, but I can’t imagine anyone better at doing that than the Boeing team.”
But days later, Muilenberg’s team reversed its decision. Fresh analysis suggested that the weight penalty of the Pelikan tail might be more like 800 or 900 pounds, and this and other factors tipped the balance in favor of a conventional four-post tail.