General Electric’s second package of upgrades for the GEnx-1B engine on the Boeing 787 has been certificated by the FAA.

Approval of the performance improvement package (PIP II) comes as Boeing completes its first week of flight testing for the improved engine since conducting a check flight on 787 development aircraft ZA005 on April 9. Until that time the aircraft, which had begun flight tests of the PIP II package late last year, was grounded along with the rest of the fleet following a series of battery failures in early January.

GE was granted FAR 33 engine certification following a meeting with the regulator on April 12. Certification was originally targeted for late in 2012, but was delayed because of lack of suitably cold weather last year for icing tests.

The package is designed to bring the performance of the engine up to the original GE-powered 787 fuel burn specification.

Development of a series of upgrades began following the discovery that the baseline version was around 3% adrift.

The performance of the initial PIP I package, which was certified in August 2011 and entered service with Japan Airlines in April last year, has resulted in better than expected fuel burn on initial aircraft, according to the carrier.

With the PIP II, which is due to enter service later this year, GE is optimistic that overall aircraft-level performance will reach or exceed initial goals.

The GEnx-1B is designed to have 15% better fuel efficiency than the CF6-80 it succeeds.

The PIP II package, which also included a higher rating of 78,000-lb.-thrust for the stretched 787-9, includes an effective increase in fan diameter of 0.5 in., optimized outlet guide vanes, a higher-flow low-pressure compressor, improved high-pressure compressor aerodynamics and durability improvements in the high-pressure turbine and combustor.