David Repsher, 45, and Matthew Bowe, 32, were injured on July 3 when the Flight For Life helicopter they were aboard crashed on take-off from the St. Anthony Summit Medical Center in Frisco, a mountain town about 70 miles west of Denver.
The pilot, Patrick Mahany, was killed in the crash.
The men had been en route to a public relations event at a Boy Scout camp and there were no patients on board.
Repsher is in critical condition at a Denver-area hospital with burns over 90 percent of his body, while Bowe suffered severe internal injuries and is permanently disabled, the pair's lawyer, Peter Rietz, said in a statement.
Named as defendants are the helicopter's operator, Air Methods Corp. of Englewood, Colorado, and the aircraft's manufacturer and distributor, Airbus Helicopters S.A.S. of France and Airbus Helicopters, Inc. of Grand Prairie, Texas.
The lawsuit, filed in Summit County District Court in Colorado, alleges that mechanics employed by Air Methods "failed to properly repair, maintain and inspect" the AS350-B3e helicopter, the complaint said.
The suit, which seeks unspecified monetary damages, also alleges that the helicopter was designed and built by Airbus Helicopters, a unit of Airbus, with flaws to its tail rotor system which malfunctioned and made the aircraft "uncontrollable in the event of a failure, especially at low speeds, hover and/or liftoff."
Additionally, the aircraft was not "crashworthy" and its fuel tank ruptured and burst into flames when it struck the ground.
"David Repsher's body was on fire at the time he was extricating himself from the helicopter wreckage," the complaint said.
Air Methods did not immediately respond to a request for comment.
A spokesman for Airbus Helicopters said they had not seen the lawsuit and have no comment on it.
"Everyone at Airbus Helicopters Inc. is extremely saddened by this accident and our thoughts continue to be with the medical crew and their families and the pilot's family," the company said in a statement.
"We and our French affiliate, Airbus Helicopters, are actively cooperating with and assisting the National Transportation Safety Board in its investigation of the accident."
AIR METHODS CORP: http://registry.faa.gov/N390LG
NTSB Identification: CEN15FA290
Nonscheduled 14 CFR Part 135: Air Taxi & Commuter
Accident occurred Friday, July 03, 2015 in Frisco, CO
Aircraft: AIRBUS HELICOPTERS INC AS350B3E, registration: N390LG
Injuries: 1 Fatal, 2 Serious.
This is preliminary information, subject to change, and may contain errors. Any errors in this report will be corrected when the final report has been completed. NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.
On July 3, 2015, at 1339 mountain daylight time, an Airbus Helicopter Inc. (formerly American Eurocopter) AS350B3e helicopter, N390LG, impacted the upper west parking lot 360 feet southwest of the Summit Medical Center helipad (91CO), Frisco, Colorado. A post-impact fire ensued. Visual meteorological conditions prevailed at the time of the accident. The helicopter was registered to and operated by Air Methods Corp and the flight was conducted under the provisions of 14 Code of Federal Regulations Part 135 on a company flight plan. The airline transport pilot was fatally injured and two flight nurses were seriously injured. The public relations flight was en route to Gypsum, Colorado.
According to Air Methods the helicopter was flying to the American Spirit of Adventure Boy Scout Camp near Gypsum, Colorado, for a public relations mission. Multiple witnesses observed the helicopter lift off from the ground-based helipad, rotate counterclockwise, and climb simultaneously. One witness estimated that the helicopter reached an altitude of 100 feet before it started to descend. The helicopter continued to spin counterclockwise several times before it impacted a parking lot and an RV to the southwest of the Flight for Life hangar and helipad. The helicopter came to rest on its right side, was damaged by impact forces, and was charred, melted, and partially consumed by fire.
FAA Flight Standards District Office: FAA Denver FSDO-03
Pilot Patrick Mahany, a decorated Vietnam veteran who spent his last 27 years flying as a Life Flight pilot, was killed in the July 3, 2015 crash.