DENVER — The Federal Aviation Administration (FAA) issued an Emergency Airworthiness Directive Tuesday night after debris from a United Airlines Boeing 777 fell on several Broomfield neighborhoods Saturday.
The Emergency Airworthiness Directive requires U.S. operators of airplanes equipped with certain Pratt & Whitney PW4000-112″ engines — the type of engine on the United Boeing 777-200 that failed — to inspect the engines before further flight.
A fan-blade failure occurred on the flight to Honolulu just after the plane departed from Denver International Airport (DIA). The pilot made an emergency landing back at DIA, and no one was hurt from the falling debris or on the flight. The failure resulted in damage to the engine, an in-flight engine fire and damage to the airplane.
Several parts of the Pratt & Whitney engine were collected to determine the cause.
After reviewing the data and considering safety factors, the FAA determined operators must conduct a thermal acoustic image (TAI) inspection of the large titanium fan blades at the front of each engine to detect cracks on the interior surfaces or in areas that can’t be seen in a visual inspection.
The FAA will review results on a rolling basis. It may revise the directive to set a new interval for the inspection or subsequent inspections, depending on the initial results and further investigation. The previous inspection interval for the engine was every 6,500 flight cycles.
In a statement, Pratt & Whitney said the fan blades from the PW4000-112″ engine are unique to the specific engine. The inspection process will require the fan blades to be shipped to Pratt & Whitney to be inspected at their FAA-authorized repair station.
Pratt & Whitney said approximately 125 Boeing 777 aircraft have the specific engine.
A statement from Pratt & Whitney read, in part:
Pratt & Whitney is coordinating all actions with Boeing, airline operators and regulators. The safe operation of the fleet is our top priority. Pratt & Whitney commends the flight crew operating United Airlines flight 328 for their professionalism. Further investigative updates regarding United Airlines flight 328 will be at the discretion of the NTSB.
Boeing also provided a statement, saying it supports the FAA’s guidance on the inspection requirements.
United Airlines already grounded their fleet of Boeing 777s with the Pratt 7 Whitney PW4000-112″ engines Sunday. They are the only U.S. carrier affected by the order. In a statement Tuesday, the airline said:
“On Sunday, we voluntarily removed 24 Boeing 777 aircraft powered by Pratt & Whitney 4000 series engines from our schedule. We’ve been working with the NTSB on their investigation and will comply with the FAA’s Emergency Airworthiness Directive to ensure all 52 of the impacted aircraft in our fleet meet our rigorous safety standards.”
The investigation into why the engine failed is ongoing, and the NTSB says it’s too early to draw conclusion on what caused the failure. Safety experts say the investigation will focus on why the fan blades snapped and whether mistakes were made in manufacturing, maintenance or inspections.