The Obama administration is violating a judge’s order to turn over documents in the Aug. 6, 2011, shootdown of a U.S. helicopter — call sign Extortion 17 — that killed members of SEAL Team 6 in Afghanistan, a watchdog group is charging.

On the fourth anniversary of the worst one-day loss of military life in the war on terror, families of the dead say they are aghast that the government will not honor basic requests under the Freedom of Information Act.

“It has now been four years since Extortion 17 was shot down,” said Doug Hamburger, whose Army air crew son, Patrick, was one of the 30 Americans killed. “I find it quite disturbing that the government is not willing to give us the answers we deserve. I find it very irritating that we will not question the Afghans about their knowledge of what took place that night.”

U.S. Central Command’s official investigation concluded that a rocket-launched grenade from a Taliban fighter standing near the landing zone clipped a rotary wing, sending the Ch-47 Chinook into a violent downward spin. It was the worst day for fatalities in the history of naval special warfare.

The tragedy took some of the glow off SEAL Team 6’s grand achievement just three months earlier: A team penetrated Pakistan airspace, infiltrated a compound in Abbottabad and killed al Qaeda leader Osama bin Laden.

The families accept the fact that a single shot brought down the helicopter. But some say the official report, which contained no direct criticism of decision-makers that day, did not delve deeply enough.

They believe SEAL Team 6 had a target on its back and that persons inside the Afghan National Security Forces may have tipped off the Taliban that night in Tangi Valley. That is why, they say, a fighter just happened to be stationed in a turret within 150 yards of a landing zone that had never been used before.

A Defense Department special operations official told a House subcommittee last year that there is no indication the mission was compromised by the Afghans.

Family members are hoping Freedom Watch, a watchdog legal group led by Larry Klayman, can force new disclosures using the power of the FOIA process.

Since filing a lawsuit, Mr. Klayman says, he has been “stonewalled” by the Justice Department, the Defense Department, the CIA and the National Security Agency.

U.S. District Judge Richard J. Leon in February signed an order requiring the Obama administration to release documents on a continual basis through the spring and summer. The Justice Department said at least 50 documents in the Pentagon have been identified as relevant, but only one has been turned over. And Justice unilaterally set a new deadline for the release and then ignored it, Mr. Klayman said. Throughout, he said, Justice lawyers have refused to take his phone calls.

“They don’t even produce under their own self-imposed deadline,” Mr. Klayman told The Washington Times. “We’re pleading with the judge to do something, and he’s just sitting on it.”

In one of his motions, Mr. Klayman stated: “As this Court must be aware, this is not an ordinary Freedom of Information Act case, it involves obtaining records concerning the deaths of Navy SEAL Team 6 and other special operations forces on a mission with the call sign Extortion 17. The families of these deceased heroes have been stonewalled by the Obama Department of Defense and the Obama National Security Agency in disrespect over their sons’ unexplained tragic deaths. Many of these family members are undergoing psychological care over what has become a double tragedy: the deaths of their sons and the cover-up for which these family members feel betrayed by their own government.”

Mr. Klayman said the NSA has agreed to provide some information. Since the agency’s main task is to eavesdrop on phone and Internet messages, it may have recorded communications related to the attack.

A Justice Department spokeswoman said there would be no comment beyond its court filings. Its lawyers have told the judge that the process of locating relevant documents and removing classified information takes time.

The mission

It was exactly four years ago, at 2:22 a.m., that a rebuilt conventional CH-47 Chinook helicopter took off from a forward operating base, carrying some of the most skilled and advanced warriors ever molded by U.S. special operations.

Onboard were 17 members of SEAL Team 6; five naval special warfare operators, including one to intercept communications and another to handle Bart the war dog; five Army flight crewmen, including a National Guard and an Army Reserve pilot; and three Air Force personnel. The force included seven Afghan soldiers and an Afghan interpreter.

The mission itself has proven controversial to some family members. The immediate reaction force (IRF) was assembled hastily for insertion into Tangi Valley to help Army Rangers capture fleeing Taliban.

The Rangers were not in need of rescue. Military officers interviewed by investigators said they could not recall an IRF ever being sent for such a mission.

The Chinook was descending on a noisy battlefield where Apache helicopters and a C-130 gunship had been buzzing overhead for three hours, alerting Taliban fighters. Planners selected a landing zone that had never been used before. The Chinook had no Apache escort, as did the Ranger team that enjoyed the element of surprise when it touched down hours earlier.

The two Apaches, Gun 1 and Gun 2, on scene were never emphatically told to move near the landing zone to scan for threats. They stayed fixed on enemy “squirters,” or runners, until just a few minutes before landing.

“Honestly, sir, I don’t think anybody had really looked at the LZ,” said the pilot of Gun 1. “I mean, at any time if we would have found these squirters, or they would have found weapons, we were — the way I was understanding it, we were going to be clear to engage due to the fact that they had weapons, but we had to [positively identify] them first.”

He added: “So we hadn’t started looking at the LZ yet, just due to there was so much more of a threat to the east with the squirters. I would say that on the three-minute call is when Gun 2 started looking at the LZ, giving an LZ brief op. I would say that was the first time that we really had eyes on the LZ.”

No one saw two Taliban armed with grenade launchers standing on a mud-brick turret well within range of the descending chopper.

The navigator on the AC-130 gunship said there was simply too much gun and engine noise to think that the Chinook could make an undetected entrance.

“One of the other things that we did talk about — kind of what you’re hitting on, sir, is about the fact that, you know, for three hours we had been burning holes in the sky,” the officer told investigators. “You’ve got [Apaches] flying around, so there’s a lot of noise going on and, basically, this entire valley knows that there’s something happening in this area. So, to do an infil on the X or Y, you know, having that element of surprise in the beginning of an operation is good, but by the time we’ve been there for three hours, and the party’s up, bringing in another aircraft like that, you know, may not be the most tactically sound decision.”

Today, some family members are not just disappointed in the investigation and the FOIA process, but also in how the House Oversight and Government Reform subcommittee on national security conducted a brief hearing in Feb. 2014.

No family members were allowed to testify. The Pentagon’s witness stuck to a theme that no mistakes were made that night, though the investigative file contained testimony from a number of witnesses saying the mission was riddled with missteps.

“The hearing as it took place was meant to honor the heroes of Extortion 17 instead of to answer our questions,” Mr. Hamburger said.

“During the last several years it is evident that our government has spent a lot of time and resources covering up the truth on many things from both our allies and the American public,” Mr. Hamburger added. “Things like Benghazi and the NSA. I am afraid that with this FOIA case that the government is purposely delaying turning over documents because they need the time to redact and to delete things they do not want the American public to become aware of.”

Charlie Strange, whose Navy cryptologist son, Michael, was on Extortion 17, told The Times last year that it was too much of a coincidence for Taliban to be standing so near the landing zone.

“Somebody was leaking to the Taliban,” said Mr. Strange. “They knew. Somebody tipped them off. There were guys in a tower. Guys on the bush line. They were sitting there, waiting. And they sent our guys right into the middle.”