Doug Hughes, the under-the-radar postal worker who airmailed himself into the Washington limelight in a putt-putt flying machine, was charged with a felony Thursday and sent home to Florida to await prosecution, a day after he landed his gyrocopter on the U.S. Capitol grounds in a self-described “crazy” act of civil-aviation disobedience.

Still clad in the letter carrier’s uniform that he wore Wednesday during his low-altitude excursion from an airfield in Gettysburg, Pa., to the West Lawn of the Capitol, the 61-year-old advocate for campaign finance reform appeared in U.S. District Court in Washington, charged with violating registration requirements involving an aircraft, which is a felony.

Hughes, whose midday sortie through Washington’s highly restricted airspace apparently went unnoticed by military and civilian aviation authorities, also was charged with a misdemeanor count of violating national-defense airspace.

In court, the lanky Hughes, his gray hair mussed after an overnight stay behind bars, seemed eager to address Magistrate Judge Deborah A. Robinson. But federal public defender Tony Miles, representing Hughes, kept telling him to be quiet.

Robinson released Hughes pending a preliminary hearing May 8, and ordered that he remain confined to his bungalow in Ruskin, Fla. (population 17,000 or so), where he has worked at the local post office for about 11 years.

The contraption that landed on the Capitol’s West Lawn

As for piloting aircraft — including the type of ultralight contraption aboard which he descended from the sky Wednesday, carrying protest letters addressed to every member of Congress — the judge grounded him. And she instructed that he stay away from the Capitol and the White House when he returns to Washington for court hearings.

Hughes and Miles then hurried from the courthouse, declining comment.

“He’s not a psychopath,” Mike Shanahan, a friend of Hughes’s in Florida, said by phone Thursday. “I realize this stunt seems totally insane. But he’s not a nut. What he wanted to do was get America’s attention. And he sure did that.”

Meanwhile, as members of Congress vowed to investigate how the flying mailman managed to penetrate Washington’s air-defense system, the Secret Service on Thursday denied a report that it was tipped off to the impending incursion moments after Hughes’s takeoff

Last year, Hughes contacted his hometown newspaper, the Tampa Bay Times, and explained what he intended to do. On Wednesday, aware that Hughes’s plan was in motion, the Times published an article about his flight on its Web site before he landed. The paper said that while Hughes was in the air, a Times reporter called the Secret Service and the U.S. Capitol Police, informed authorities about the protest flight and asked whether they knew about it.

However, the Secret Service said in a statement Thursday that a reporter merely asked “if the Agency was aware of a permit obtained by a protestor named Doug Hughes to fly and land on the U.S. Capitol grounds via a gyro-copter.” The Times responded to the statement by saying that the reporter “never asked about a permit” and that he told the Secret Service “that a man who identified himself as a protestor from Tampa Bay wanted to land a gyrocopter on the Capitol lawn.”

The letters that Hughes had hoped to deliver — 535 of them, one for each voting member of the House and Senate — decried the Supreme Court’s 2010 ruling in Citizens United v. Federal Election Commission, which struck down limits on campaign donations by corporations and unions. Hughes declared “a voter’s rebellion” over the “corruption” of the electoral process by rich special-interest groups.

On Capitol Hill, there was less concern Thursday about Hughes’s message than how he delivered it — flying into the heart of the nation’s capital and alighting on the Capitol lawn about 1:30 p.m. in what amounts to an airborne go-cart, powered by something like a lawn mower engine, and kept aloft by an overhead rotor and a small propeller.

“How did it happen?” Sen. Charles E. Schumer (D-N.Y.) wondered aloud. “How did the helicopter get through? Why weren’t there alarm bells that went off? Why wasn’t it intercepted? Did we know about it? How far from the Capitol grounds did we know?”

Schumer, the Senate’s third-ranking Democrat, added: “Just saying it’s a little helicopter, or it’s one person, or it was harmless, does not answer these questions. And we need to know what happened.”

Sen. Ron Johnson (R-Wis.), chairman of the Homeland Security and Governmental Affairs Committee, said in a statement: “I am deeply concerned that someone has the ability to fly for over an hour through the most restricted airspace in our country, past the White House, and land on the lawn of the Capitol.”

He added that he wants “a full accounting by all federal organizations entrusted with securing the United States from this and similar events.” That Hughes was able to pull off the stunt, Johnson said, is “a reminder that the risk to America and Americans is ever present.”

Hughes’s friend Shanahan, also a letter carrier in Ruskin, said he and the gyrocopter enthusiast have long worked together and became close about five years ago, bonding over their shared worry that big-money interest groups are ruining the United States.

“This is not something against rich people,” Shanahan, 65, said. “They enjoy their yachts and their charity balls and things like that. That’s fine. They’re not out to take over the country. But we have a handful of rich people and special interests that are trying to do exactly that, and they’ve corrupted the government.”

He said: “We’re both very concerned about that. In fact, I’m writing a book. But Doug was always talking about wanting to do something more spectacular.”

Two years ago, Shanahan said, he and Hughes created a Web site warning their fellow citizens about the looming threat to the republic.

“We had it up for six months or so, and we weren’t getting anywhere with it,” Shanahan recalled. “It was frustrating because nobody cared. And we were trying to think of ways to get a little more public awareness. Now, Doug had just bought that gyrocopter. And one day he said: ‘You know, I’ve come up with an idea. Tell me what you think of this.’ ”

Shanahan said he was aghast. “My reaction was, you don’t do that in D.C.! I told him, ‘Look, you got all these agencies there, all these guys with all these kinds of weapons, and they will see you coming, and they will kill you.’ ”

Hughes, a Vietnam War-era Navy veteran, “is a very intelligent person, a very detail-oriented person, and he is tenacious,” Shanahan said. “I realize now he wasn’t taking what I was saying to him as a warning. He was taking them as problems to be solved.”

According to the Tampa Bay Times, Hughes was methodical in orchestrating his stunt. Even though “a Boy Scout with a BB gun could shoot me down,” he concluded that authorities most likely would hold their fire, worried that a mailman plunging from the clouds in a ball of flames wouldn’t look good on the TV news.

In 2010, Hughes’s 24-year-old son committed suicide in Florida, driving his car into oncoming traffic and killing another motorist. “I’ve come to realize that it did change him,” Shanahan said of Hughes. “He just decided that we’re all going to die, and you might as well die for a good reason. So he was willing to risk his life in hopes of saving the country.”

Hughes got in a truck and hauled his gyrocopter to Gettysburg Regional Airport.

Wednesday morning, Al May, who was visiting the airfield, saw Hughes talking on his cellphone through a headset as the gyrocopter puttered down the runway, preparing for takeoff.

Hughes apparently was on the phone with Shanahan. “He said he was up north and was going to do it,” Shanahan said. The call lasted maybe 15 seconds before Hughes hung up.

Seconds later, May said, Hughes came buzzing down the runway, his tiny motor packing all the roar of a lawnmower, then banked and headed due south toward Sugarloaf Mountain in Maryland.

“I waved to him,” May said.

On a lot of days, the airport sits silent. There is no control tower and no restaurant. There are no aviation services. Fewer than 20 small planes occupy several hangars around the narrow asphalt strip. When Hughes pulled up with his gyrocopter in tow, May helped him push it onto the runway. Hughes was wearing his postal service jacket and had a plastic postal tray filled with his letters to Congress.

“The guy acted perfectly normal,” May recalled of Hughes, who is married and has an adolescent daughter. “He said, ‘I’m just going to fly around here.’ ”

In Ruskin, Hughes’s wife, Alena Hughes, answered their home phone Thursday and immediately handed it to Paul Carr, a local attorney whom she has retained. The felony charge against Doug Hughes carries a prison sentence of up to three years; the misdemeanor is punishable by no more than a year behind bars.

“It looks to me like an official postman was delivering mail to Congress,” Carr said. “That might be a crime; I don’t know. Doesn’t seem like one to me.”

Informed that the 535 letters were taken as evidence, he said: “Well, that to me is unlawful interference with the U.S. mail.”

Halsey reported from Gettysburg. Duggan and Alexander reported from Washington. Mike DeBonis, Peter Hermann and Mary Pat Flaherty contributed to this report.