The widow of a deceased Army helicopter crew chief is suing four of America’s largest defense manufacturers, alleging her husband’s MH-60 Black Hawk helicopter was improperly assembled and maintained, causing its engine to suddenly shut off at a critical moment.

Emil Rivera-Lopez, originally of San Juan, Puerto Rico, was 31 when his helicopter crashed off the coast of Yemen during a training mission on August 25, 2017. The Army pronounced him dead six days later. His body was never recovered.

According to a complaint filed recently in U.S. District Court for the Southern District of Georgia, members of Rivera-Lopez’ family are suing Lockheed Martin, United Technologies and General Electric — each of which play a role producing or maintaining the military’s Black Hawk helicopters — for failing to properly install certain critical engine parts, allegedly causing a catastrophic fuel leak. An automated system then overreacted to the fuel leak and shut the whole engine down when it shouldn’t have, the complaint alleges.

The lawsuit does not explain how it obtained the information about what caused the crash. The Army has not publicly released the results of its investigation into the incident.

Five other individuals, whose names were withheld from the legal complaint because of the secret nature of their work, were rescued. According to the complaint, they all suffered injuries.

An Army spokesman declined to comment, citing ongoing litigation. A spokeswoman for Lockheed Martin’s Sikorsky Aircraft Corporation declined to comment. Media representatives from United Technologies and General Electric did not respond to requests for comment.

Attorneys representing the plaintiffs include Mary Schiavo, a former inspector general of the U.S. Department of Transportation.

“The bottom line here is this matters to the families and children of those involved,” Schiavo said Friday in a phone interview. "... we will make sure it doesn’t happen again.” She added that she expected the suit to take a long time to resolve and said that the plaintiff attorneys followed all the rules in bringing the complaint forward.

The Black Hawk helicopter is among the most trusted and widely-used aircraft in the U.S. military arsenal. For decades it has been relied on by military Special Forces operators to conduct covert missions in austere, chaotic conditions. They have often been used to deliver Navy SEALs and other Special Forces operatives into hard-to-reach combat zones while taking enemy fire, or pluck stranded individuals from the sea while hovering just a few meters above the water.

Keeping old aircraft flight-worthy has been a challenge across the military services. Attorneys representing Rivera-Lopez’ family allege the manufacturers did not tell the Army about important equipment shortcomings, and did not include important information in manuals.

Specifically, an engine part called a “T-fitting” allegedly had not been screwed tightly enough to prevent a fuel leak. And a separate engine part called a “full authority digital electronic control unit,” produced by a subsidiary of United Technologies, allegedly malfunctioned and caused the engine to shut down.

Companies producing the Black Hawk “had knowledge that the subject aircraft was defective, dangerous, unsafe, and not airworthy and had knowledge of the unreasonably unsafe design, manufacturing defects, engine and [electronic control unit] problems, assembly errors and flaws, and defective manuals and instructions as well as the magnitude of risk for serious bodily injury and death if those systems were to fail,” the complaint alleges.

At the time of his death, Rivera-Lopez was an experienced aviator and combat veteran who had survived numerous deployments in the U.S. war on terror, according to an Army obituary.

He been a member of the 160th Special Operations Air Regiment, an elite cadre of Army aviators trained to fly covert missions in the middle of the night. Known informally as the “Night Stalkers,” the unit has been involved in numerous high-profile missions including the 2011 raid in which Osama bin Laden was killed.

The 160th airborne was established in 1981 and has often been relied upon to deliver Navy SEALs and other Special Forces operatives on dangerous missions, often flying in poor visibility or under heavy enemy fire. It employs some of the military’s best and most experienced pilots.

A comparatively higher likelihood of crashing has long been an accepted risk for those who join the Night Stalkers, even when there are no equipment failures.

According to a 2015 history of the U.S. military’s Special Operations units by Sean Naylor, the Night Stalkers have historically conducted training missions in darkness, with pilots using night-vision goggles to navigate.

“During the first years of the unit’s existence the 160th crashed helicopter after helicopter striving to overcome the challenges of operating in darkness,” Naylor wrote. “In one grisly seven-month period in 1983, the battalion lost sixteen men and four helicopters.”

Although the unit got its crash rate under control over time, all five military services have faced challenges keeping old aircraft ready to fly.

A database of known military aircraft crashes maintained by MilitaryTimes counted 18 crashes last year involving UH-60 Black Hawk helicopters in 2018 alone. The total number of crashes across all military aircraft types increased from just over 900 in 2013 to more than 1,200 in 2017, MilitaryTimes found, even though the total number of flight hours went down.

The increase came as the sequestration budget cuts put a financial squeeze on the Pentagon’s maintenance budget after 2013, and U.S. airstrikes against ISIS ramped up in 2014.

Clarification: An earlier version of this article described Staff Sargaent Emil Rivera-Lopez as an Army helicopter pilot. He was an MH-60M helicopter crew chief and repairer.