The UK's Civil Aviation Authority (CAA) has revoked its ban on Boeing 777s fitted with Pratt & Whitney 4000 engines. The operating ban was introduced on February 23rd, two days after a United Airlines 777-200 suffered engine problems over Denver.

The UK lifts ban on the 777

The UK will repeal its ban on Boeing 777s with PW4000-112 engines after imposing a temporary ban in February. After a sequence of incidents involving the engine type, several countries, including the U.S, Japan, the U.K and South Korea, temporarily banned the plane from their airspace pending further review.

The catalyst for the ban was United Airlines flight UAL328 on February 20th. The flight made headlines worldwide after suffering uncontained right engine failure mid-flight over Denver, with debris scattering over the city. On the same day, a Boeing 747-400F with PW4000 engines experienced engine failure after taking off from Maastricht, with debris injuring two people in a small Dutch village.

In the immediate aftermath, several airlines grounded their 777 fleets on recommendation from Boeing. According to Boeing, there are 128 777s fitted with the PW4000 engine option, with some older -200, -200ER and -300 models affected. No UK operators were affected by the ban, including British Airways which has a mix of Rolls-Royce and GE engines powering its 777 fleet.

A few days after the UA flight incident, the FAA released an emergency airworthiness directive mandating thermal acoustic imagery of fan blades. The UK's CAA stressed at the time of introducing the ban that it was a “precautionary measure until appropriate safeguards are in place" and will be kept under constant review.

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Other incidents involving PW4000 engines

The infamous United Airlines flight UAL328 incident is not the only time PW4000 engines have encountered problems. In December, a Japan Airlines Boeing 777 experienced an engine cowling problem which led to an uncontained engine failure. Japan Airlines flight JL-904 suffered the issue soon after departing from Okinawa, making an emergency landing approximately 35 minutes after takeoff.

Boeing itself was aware of the engine cowling problems on some of its 777s. The aerospace manufacturer discussed strengthening the protective engine cowling on select planes as far back as two years before the UA flight incident. Another United Airlines 777 suffered engine failure in 2018, experiencing a similar issue to the Denver incident.

According to an FAA document from 2020,

“Boeing has decided to redesign the fan cowl instead of trying to modify existing fan cowls to address both the structural strength concerns and moisture issues."

How many 777s are affected?

It is important to note that only a small number of 777s were affected by engine issues. 777s with either Rolls-Royce or GE engines were unaffected by the ban and have remained operational. A total of 128 Boeing 777s are equipped with PW4000 engines. United Airlines pulled 24 of the planes immediately, with other airlines following suit.

Do you think the ban has been lifted at the right time? Let us know your insights in the comments.