The approval follows a multi-year delay that frustrated airline customers.
The Federal Aviation Administration has certificated Boeing’s 737 Max 7, ending a yearslong process that has been held up by design changes and heightened regulatory oversight.
The agency said it issued an amended type certificate for the smallest variant of the 737 narrowbody aircraft family on 3 August, reflecting “years of sustained work to resolve complex technical issues and complete a thorough review of the airplane’s design and supporting safety analysis”.
“Throughout the process, the FAA performed or directly reviewed significant work involving flight controls, system safety assessments, human factors, flight crew alerting and other novel, complex or safety-critical areas, while also requiring testing, design changes and additional analysis where necessary,” the FAA adds.
The approval marks a major milestone for Boeing, which at one point had aimed to have the Max 7 in service in 2019.
The approval leaves the largest variant of the narrowbody family, the Max 10, as the only variant not yet certificated. Boeing has said it expects the FAA will approve the Max 10 before year-end, and the company anticipates beginning to deliver both Max 7s and 10s in 2027.
“Our team of dedicated engineers and test experts worked through challenges, an extended pandemic and the transition to new certification processes,” says Boeing Commercial Airplanes chief executive Stephanie Pope. “Through it all, our team stayed focused on completing all requirements and delivering a safe and more capable airplane to our customers.”
Boeing started the Max 7’s test programme in 2018 and has since completed more than 1,000h of flight and ground tests.
With the Max 7, Boeing introduced design changes, including to the pilot-alerting and engine anti-ice systems.
It redesigned the anti-ice system to address the problem of engine inlet barrels getting too hot in some circumstances.
Boeing added “turbulators” on the forward fan cases ahead of the Max’s twin CFM International Leap-1B engines. Those devices make air entering the engine swirl, drawing in cooler air and reducing temperatures, the company has said.
The anti-ice redesign also includes a new “flow restrictor” that limits how much hot air strikes critical components; new insulation blankets around inlet ducts, circuit breakers, and wiring; a “fault redundancy” pressure switch; and an integrated air systems controller for the engine anti-ice valve.
“These changes provide pilots clearer information and warnings and prevent the engine inlet from overheating and potentially weakening the surrounding structure,” the FAA says.
Boeing has orders for 295 737 Max 7s, with US discount carrier Southwest Airlines holding 254 of them, according to fleet data provider Cirium.
The Max 7 has 3,800nm (7,038km) of range and can carry 135-160 passengers in two classes, Boeing says.
Story updated on 3 August to include comments from Boeing.
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