When the crew of 787 Line No. 86 completed a functional check flight on March 25, it seemed the completion of final certification tests of the modified battery for the FAA was just days away.

Yet, despite apparently making good progress with both the installation of the revised lithium-ion battery system and associated ground tests, the final series of certification testing appears to have dragged on for longer than expected. When Boeing won FAA approval for its certification test plan on March 12, company officials commented three days later that tests could be wrapped up and submitted to the airworthiness authority within 1-2 weeks.

Reports on approximately 19 key tests have yet to be submitted to the FAA to show compliance with the special conditions which will enable the aircraft to return to service. The culmination of these involves a single certification demonstration flight using Line 86, an aircraft eventually destined for LOT Polish Airlines, and a ground test using development test aircraft ZA005, which will involve a deliberately induced battery failure.

The functional test flight took place at least two days later than originally hoped, and by March 28 both the follow-on certification flight- and battery-failure ground tests had yet to occur. The target date for completion for all is now thought to be in early April.

However, while frustrating for the company and its 787 operators, Boeing indicates the addition of a few more days for testing is less significant when seen in the context of the relative duration of the overall grounding, which enters its 74th day on April 1. “We are very close” Chairman/CEO James McNerney said March 28 at the U.S. Chamber of Commerce’s Aviation Summit in Washington. “It will be sooner rather than later. The tests will be completed in several days and I have a high degree of confidence that the data will tell us—and the FAA, who are the decision-makers—that the fix is what we it need to be [able to] get this airplane back in service in due time.”

While Boeing is not commenting on the status of the tests, or the reasons for the longer-than-expected execution of the final phase, program sources indicate the delays have more to do with aircraft and system readiness than discoveries of issues with the modified battery system. Both aircraft, like all their 787 sisterships, have been grounded since mid-January and, in a similar way to a car that has not been run for months, require extra attention to become fully operational for the final FAA certification tests. Yet Boeing says the 2-hr. 9-min. functional check flight of Line No. 86 on March 25 went “according to plan.”

The flight was described as “a normal Boeing production check flight intended to validate that all systems function as designed.” During the flight, the crew cycled the landing gear and “operated all the backup systems, in addition to performing electrical system checks from the flight profile,” adds the manufacturer.

Another issue that also appears to have taken Boeing off-guard is a report from Reuters that the FAA may be considering imposing a temporary restriction of the 787’s extended twin operations (ETOPS) clearance as a result of the battery modification. The ETOPS clearance allows the twin-engine aircraft to operate up to 330 min. flying time from a primary or alternate airport. ETOPS approval is pivotal to the 787’s viability because it allows the aircraft to be used over long routes traditionally reserved for three- and four-engine aircraft.

Calling the Reuters report “pure speculation,” Boeing says that VP/Chief Project Engineer Mike Sinnett’s statements last month in Tokyo that “there will be no restrictions on the aircraft and no limit to ETOPS,” reflect the company’s position. The FAA, which will only begin to review the data for compliance with the AD following the certification flight of Line No. 86, says it is premature to say if there will be any change to the current certification base of the 787.

Pending completion of certification and FAA approval for battery system modifications, Boeing aims to immediately restart production test flights at Everett, Wash., as well as its Charleston, S.C., production site. Several production test flights are also set for 787s that have been stored at a paint facility near Fort Worth for the duration of the grounding of the fleet that followed two separate battery failures in January.

Separately, the National Transportation Safety Board announced its upcoming forum, “Lithium-Ion Batteries in Transportation,” will be held on April 11-12. The NTSB event, which was announced on March 7 when it released its interim factual report on the Jan. 7 Japan Airlines’ 787 battery fire investigation, will focus on design, development and performance of the batteries as well as related regulatory and safety aspects of the technology.