The Federal Aviation Administration (FAA) has said that it is ordering immediate inspections of Boeing 777 planes with Pratt & Whitney PW4000 engines before further flights after an engine failed on a United flight on Saturday February 20.
The engines are used on 128 older versions of the plane accounting for less than 10% of the more than 1,600 777s delivered and only a handful of airlines in the United States, South Korea and Japan have been operating them recently.
Operators must conduct a thermal acoustic image inspection of the large titanium fan blades on each engine, the FAA said.
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The National Transportation Safety Board said earlier this week that a cracked fan blade from the United Flight 328 engine that caught fire was consistent with metal fatigue.
"Based on the initial results as we receive them, as well as other data gained from the ongoing investigation, the FAA may revise this directive to set a new interval for this inspection or subsequent ones," the FAA said.
In March of 2019, after a 2018 United engine failure attributed to fan blade fatigue, the FAA ordered inspections every 6,500 cycles. A cycle is one take-off and landing.
On Wednesday February 24, South Korea's transport ministry ordered the grounding of all local airlines' Boeing 777s with PW4000 engines and will ban foreign carriers with those planes from entering its airspace from Thursday February 25.
A day earlier it instructed airlines to inspect the fan blades every 1,000 cycles following guidance from Pratt. An airline would typically accumulate 1,000 cycles approximately every 10 months on a 777, according to an industry source familiar with the matter.
The US FAA said in 2019 that each inspection was expected to take 22 man-hours and cost $1,870. It did not provide updated estimates this week.
A spokesperson for Pratt, which is owned by Raytheon Technologies , said that fan blades will need to be shipped to its repair station in East Hartford, Connecticut, for the latest inspections, including those from airlines in Japan and South Korea.
Boeing said that it supports the FAA's latest inspection guidance and will work through the process with its customers.
It had earlier recommended that airlines suspend the use of PW4000-powered planes while the FAA identified an appropriate inspection protocol, and Japan imposed a temporary suspension on flights.
Japan's transport ministry said on Wednesday February 24 that it is examining the FAA directive and has not yet decided what action to take. ANA Holdings and Japan Airlines (JAL) said that they will comply with any directives from the Japanese regulator.
The FAA spent the last two days discussing the extent of the inspection requirements, according to sources with knowledge of the matter.
On Monday February 22, the FAA acknowledged that after a JAL engine incident in December it had been considering stepping up blade inspections.
United, which is the only US operator of the older PW4000-powered 777s, had temporarily grounded its fleet before the FAA announcement. The airline said that it will comply with the airworthiness directive.
United has warned of possible disruptions to its cargo flight schedule in March as it juggles its fleet after its decision to ground 24 Boeing 777-200 planes, according to a notice sent to cargo customers.
Plunge In Demand
Another 28 of United's 777-200 planes were already grounded before the incident on February 20, amid a plunge in demand.