‘Jump jet’ gets drafted for civilian flying duty

 - February 27, 2008, 8:58 AM

The Rolls-Royce Pegasus-powered roar that rent the air at St. Mary’s County Regional Airport in Leonardtown, Md., last November heralded a most unusual first flight, that of the only civilian British Aerospace (Hawker Siddeley) Harrier in the world. At the controls was Art Nalls, a former Marine and Harrier test pilot who fell in love with the Harrier the first time he flew one.

For Nalls, who has more than 1,400 hours in Harriers, flying his Harrier for the first time was like coming home. “It was like putting on an old pair of shoes,” he said. “Much easier than I thought.”

The good feelings lasted through that nearly flawless first flight and during most of the following day’s carefully planned flight. “I can’t tell you how much I was grinning from ear to ear,” he said, “and how pleased I was, up to the point I had the emergency [a hydraulic system failure], and how great it was flying. I was ecstatic.”
The many obstacles that Nalls and his team of volunteer Harrier wizards had to overcome to get to the first-flight stage began a few years ago with a casual discussion about whether or not it might be possible to buy and operate a Harrier.
After he retired from the Marine Corps, Nalls started a successful real estate development company in Washington, D.C., but couldn’t shake the flying bug and joined the Commemorative Air Force (CAF). He eventually started an airshow business, flying aerobatic routines in his L-39 jet.

But as much fun as he had flying the L-39, Nalls never forgot the passion he had for the Harrier. When noodling around the idea of buying a Harrier with his retired Harrier pilot friends, Nalls said he “realized that one of the number-one draws at airshows is the Harrier.” The jump jet can take off and land vertically, fly fast and do aerobatics. It also announces its presence with a gut-churning blast of pure jet fuel-driven power.

The idea of flying a Harrier outside the constraints and deep pockets of the military might seem crazy at first. But the more Nalls thought about it, the more the idea made sense. “If someone had approached me years ago and said you could operate
a B-17 or a MiG-15 or MiG-17, I would have said they’re nuts,” he recalled.

But organizations such as the CAF and individual owners fly complicated old airplanes safely every day. A B-17, Nalls said, is extremely complicated and maintenance-intensive. Nalls used to own a Yak-3 powered by an Allison V12 piston engine, and he found that during every flight he was just waiting for another 60-year-old part to break. By contrast, his L-39 “is the closest you can get to a maintenance-free airplane.”

Nalls, who used to be a Harrier maintenance officer, knows that the Harrier won’t be as maintenance-free as his L-39, but he predicts it shouldn’t be as bad as a WWII bomber. Jet engines, he said, are simple, consisting of “a steel tube, a shaft, 10,000 razor blades all spinning in the same direction with a fire in the middle.” Not much maintenance is needed if air and fuel flows properly into the engine and no birds and debris are ingested.

The way a civilian Harrier will operate enhances safety as well. The airplane is not a weapons system, so all that weight and complexity is removed; it won’t be flying low-level, high-speed missions that are easy targets for debris ingestion, and there are no corrosion problems associated with operating from ocean-going ships. Weight is reduced, the electrical load is lower, and this all helps reduce the demands placed on the engine. “It gets simpler and simpler as you go along,” Nalls said.

Nalls’ search for a decent Harrier began when he read that the British government was planning to shut down the Sea Harrier (see box on next page) program because of the high cost of maintaining the airplanes as an active weapons system. Nalls asked friends in the UK to keep their eyes open for possible purchase opportunities, and one day he got a call saying that there was an intact Sea Harrier available. The price was non-negotiable, although Nalls won’t say what it was. Not only was the Sea Harrier in impressive condition, he said, but the seller also had plenty of spares and support equipment.

After he bought the Harrier, Nalls spent six months arranging shipping and approval by the Bureau of Alcohol, Tobacco and Firearms to import the former fighter-
attack aircraft into the U.S. It took him more than a year to obtain all the technical publications he needed to reassemble and maintain the Harrier, which made the overseas trip in two shipping containers. The Pegasus engine had just been overhauled and pickled and was in terrific shape. The Harrier, which had logged 1,120 total flying hours, came with complete records.

It took Nalls and the St. Mary’s Harrier experts only three weeks to reassemble the Harrier and get it ready to fly. “We had to go through each system,” Nalls said. This included double-checking everything on all systems, including running the hydraulic system through its paces and checking all the filters, lines, hoses and pumps. The Harrier’s ailerons, elevators, flaps and brakes are hydraulically controlled so the hydraulic system is critical. The rudder is cable-controlled.

The Harrier mechanics studied the AC/DC electrical system and the cooling system, then replaced the original Martin Baker ejection seat with a Marine-style Universal Propulsion Stencel unit. The hardest part of the preparation was the pitot-static system, which is used for flight instruments and as an input for multiple weapons systems and the ejection seat.

Three FAA inspectors from the Dulles, Va. FSDO spent three days climbing all over the Harrier before granting the experimental- exhibition airworthiness certificate. Finally, on Jan. 10, 2007, the inspectors signed the airworthiness certificate.

By August, Nalls had the Harrier ready for its first flight as a civilian aircraft. But during one of the last planned ground taxi attempts, the engine’s little gas-turbine starter disintegrated, and Nalls didn’t have a spare on hand. “It’s a little jet engine the size of a Folger’s coffee can,” he said. “It produces 87 horsepower and there’s no other way to start [the Pegasus].”

Investigating what was left of the old starter, Nalls learned that whoever had overhauled it before had neglected one important final step, peening over the tab on a safety washer for a retaining bolt. “It spins at 87,000 rpm,” he said, “with a clearance of 32 thousandths [of an inch]. All it’s got to do is contact the nozzle face at 87,000 rpm and she’s gone, spitting blades all over the place.”

Nalls finally found two more starters, and on November 10 the conditions were perfect for the first flight.

First Flight, Finally
Once the starter problem was solved, Nalls and team held a briefing in preparation for the first flight from the 4,150-foot runway at St. Mary’s County. Nalls flew a rolling takeoff, and right after liftoff the radio failed. Fortunately, he had briefed for this possibility and the team members in the chaseplane–a Beech Baron–knew exactly what was on Nalls’ test card and also knew to help him with any necessary radio calls.

Everything worked fine, although one caution light illuminated, warning of a problem with cooling in a rear equipment bay, and there was one small fuel leak. Nalls flew for about 15 minutes then landed conventionally (horizontally). The warning light was the result of a missing panel in the equipment bay, but the temperature inside the bay wasn’t actually higher than normal. The radio and fuel leak were fixed and the team celebrated the first flight.

On November 11, Nalls took off again after the team briefing. Twelve minutes into the flight, the number one hydraulic system failed completely. The failure was later discovered to be the result of a burst hydraulic line.

The Harrier has two hydraulic systems, but the number two system powers only the elevator and ailerons. That means no brakes, no flaps and possibly no landing gear if the emergency system doesn’t work. The big problem for Nalls was that it would be impossible to stop at St. Mary’s without brakes, and in any case, the drill for failure of the primary hydraulic system is to land vertically.

Landing vertically is not a problem if the landing gear works. But Nalls was unable to get the gear all the way down. He decided to go to Patuxent River Naval Air Station, just minutes away, instead of returning to St. Mary’s. He had asked the folks at Pax River months earlier if he could operate the Harrier from there, but they had refused. The hydraulic failure, however, was a first-class emergency, allowing Nalls the discretion to handle it as he saw fit. The safest option was Pax River.

Nalls knew that landing a Harrier with the gear up in a hover is a dangerous move, but it is also the only and approved way to land a gearless Harrier. The tricky part is that unless such a landing is executed perfectly, the nose might cant forward, collapsing the cockpit and causing the ejection seat to fire. “It can be fatal,” Nalls said. “I was between a rock and a hard place. I hadn’t hovered in 16 years and I had 20 minutes worth of fuel; the pucker factor goes up in a hurry.”

Nalls asked his ground crew to meet him at Pax River and kept trying positive-g maneuvers to force the gear to come down, which it finally did. The Harrier ended up hovering perfectly. “There was plenty of thrust, plenty of control and the engine performance was there,” Nalls said. “It trimmed up nicely and we did a very soft vertical landing.” The landing light, which acts as a secondary indicator that the nosegear is down, was on. Shortly after touchdown, the nosegear collapsed and the nose fell about five feet onto the ground. This flight turned out to be the first time a civilian pilot has ever hovered any aircraft with jet thrust, according to Nalls, and he is asking the FAA to issue him a special rating for powered lift (no rotating wings like a tiltrotor).

The Harrier suffered damaged gear doors, a broken com antenna and a snapped-off pitot-static boom. Some ribs inside the nose were also damaged, but since they no longer have to carry a heavy radar they aren’t of structural significance.

To get the broken Harrier back to St. Mary’s, Nalls had to make arrangements with the local police to tow it in the middle of the night the eight miles from Pax River to his home airport. Patrons exiting local pubs on the route were more than a little surprised to see a Harrier being towed down the road surrounded by a police escort with Nalls sitting in the cockpit wearing a bright red Santa suit.

New parts were easy to find this time and Nalls and crew expected to have the Harrier ready to fly again this month, after more extensive hydraulic system testing. This time, Nalls plans to keep the landing gear down for a while, practice more takeoffs and landings, then expand the envelope.

This summer, he hopes to start flying the regional airshow circuit. He plans to equip the Harrier with a smoke system and show audiences moves that the Marines can’t do in their more modern AV-8B Harriers.    

A Demanding Airplane

The Harrier “has an unbelievable sense of power. At idle it shakes like a bronco bull that wants to be let out of the chute. It idles at 28 percent, and you just think, holy cow, the thing is ready to rock and roll,” according to Art Nalls, operator of the only civilian Harrier.

Flying the Harrier is demanding, and Nalls said that a pilot without training would find it impossible to fly. “You’d kill yourself,” he said. The three people who had previously held his job at Patuxent River Naval Air Station died in Harrier accidents, he said, “and that’s the reason I got the job.”

In airplane mode, the Harrier flies like a high-performance jet, Nalls said. Empty weight is about 13,600 pounds, maximum fuel load 5,000 pounds and engine thrust 21,600 pounds, so the thrust-to-weight ratio is greater than one pound of thrust per pound of airplane. “It’s a hot rod.” The controls are very light and the roll rate extremely quick. “Most pilots think it’s twitchy,” he said.

Flying the airplane gets particularly tricky when the pilot is hovering using the Harrier’s unique vectoring thrust nozzles. The nozzles rotate from zero degrees (fully aft, and aligned with the longitudinal axis of the fuselage) to 98.5 degrees down from that datum. Since 81 degrees is pure vertical component as the airplane rests on the ground and in the hover, they rotate through 17.5 degrees past vertical. There are 12 important gauges in the Harrier, but they are tiny, so small that a quarter can cover each one. One shows duct pressure, an indication of the pressure of the bleed air from the high-pressure section of the engine compressor used for reaction-control nozzles in the nose, wings and tail, which help the pilot keep the Harrier stabilized during vertical flight.

Once the pilot lowers the main engine nozzles past 12 degrees, a butterfly valve automatically opens to route bleed air to the reaction control nozzles. “The flight control system is brilliant,” Nalls said. “If the pilot puts input to the rudder, it doesn’t matter if the reaction controls are pressurized or not; he just knows that the nose moves. It’s transparent to him.”

A key limitation of the Harrier is that it can hover for a maximum of 2.5 minutes, beyond which the reaction controls, powered by hot bleed air, must be allowed to cool for a corresponding amount of time.

The four thrust-vectoring nozzles are not hydraulically controlled but actuated using a lever next to the throttle on the left side of the cockpit, according to Nalls. The lever controls the nozzles using gears, shafts and motorcycle-style chains, but the nozzles are moved by more bleed air delivered by a high-pressure air motor servo mounted in the belly. When the lever is moved forward, the nozzles face aft (horizontal). As the lever is moved aft, he said, the nozzles rotate downward.

Early Harrier pilots learned a lot by experimentation, and one important lesson was how easy it is to lose control. “You travel through a regime where zero sideslip can be tolerated,” Nalls explained, “when going from wingborne to a hover.” The problem is that when the exhaust flow is bent 90 degrees via the nozzles in a hover, a force is created about 45 degrees off the downward thrust vector.

If both nozzles are blowing straight down, no problem. But if the Harrier sideslips at all, then the engine starts sucking more air into one intake on one side than the other intake. Then, because of the wing’s sweep, one wing develops more lift. “That combination causes a rolling moment,” he said, “and that rolling moment due to sideslip can exceed the pilot’s roll control authority, and you can’t stop it.” The only solution to this phenomenon– called intake momentum drag–is “don’t let it do that,” Nalls said. “You can feel it start to build. Get rudder in there, use everything simultaneously, rudder, stick and thrust.”

The Harrier carries enough fuel to fly for only 45 minutes until the tanks run dry. Nall’s flights usually last 14 to 15 minutes. In a stabilized hover, the engine burns about 32 gallons a minute, and landing from that position takes 15 seconds, so a landing is an eight-gallon affair.

For takeoff, if conditions are right, the Harrier can leap into the air vertically. But taking off horizontally is more efficient, and for every foot of roll the Harrier can carry an extra 56 pounds of fuel or payload.  

What kind of Sea Harrier?

Art Nalls’ British Aerospace Harrier (tail number XZ439) was built in 1979 as an FRS.1 and is the second oldest Sea Harrier ever built. The oldest one, XZ438, crashed and its rudder is installed on Nalls’ Harrier. He plans to retain the different color of the XZ438 rudder to commemorate the first Sea Harrier.

An upgrade program saw Nalls’ Harrier turned into an FRS.2 (fighter-reconnaissance, strike), then later to FA.2 configuration (fighter-attack). So now XZ439 is officially a Sea Harrier FA.2.

“It’s the oldest surviving Sea Harrier,” noted Nalls.