In the 15 days since ZA002, Boeing’s second of six 787 flight test aircraft, suffered a fire in its aft electrical equipment bay, forcing a fleet-wide halt in certification testing, the airframer is days, if not hours, away from releasing its findings of its investigation and disclosing the impact to the aircraft’s first delivery, say company and industry sources.
An additional delay to the 787′s entry into service with All Nippon Airways is now a virtual certainty, the length of that delay, however, is yet unknown.
While some analysts have suggested the 787′s first delivery could slip to 2012, an additional delay of more than nine months, Boeing’s previous six delays have never shifted the schedule more than six months at a time. A six month slide beyond today’s February 2011 plan would place handover to ANA around August of 2011, more than three years after its original target.
Equally important in establishing the root cause of the fire, reported to be foreign object debris (FOD) that caused a short in the panel, is ensuring primary electrical system redundancy remains intact if such an incident were to reoccur. One program source indicates FOD clogging an air duct that cools the P100 panel may be a culprit.
The Seattle Times, citing a source close to the program, reported the 787 fleet, including 23 production aircraft in Everett, have been searched for FOD.
Though the fire, which happened while on approach to Laredo, Texas, and its root cause, revealed an Achillies heel in the 787′s electrical system that must be resolved before the Dreamliner can enter service.
In an internal message to program employees last week, Scott Fancher, 787 program manager and general manager said “we have made good progress in replicating the effects in our integration labs”.
While the specific “effects” have not been disclosed, under normal operation, a drop out of the P100 panel, feeding electricity from the left engine’s twin variable frequency starter generators (VSFG) to aircraft systems, should have compensated by prioritizing the flow of electricity from the right VSFGs into the healthy P200 panel for distribution. Instead, the fire caused 787 to perceive it had lost electrical power completely, causing the Hamilton Sundstrand-built ram air turbine (RAT) to deploy.
The RAT supplies just 10 kVA of electricity, a fraction of the up to 1.45 megawatts of power generated by the aircraft’s primary systems, including the APS-5000 auxiliary power unit (APU). Sources familiar with the incident say the APU, which supplies power to the P150 power distribution panel, was not running at the time of the fire.
The result, was the loss of four of five, heads down displays (HDD) and the twin heads up displays (HUD), as well as autothrottle control and a “cascading” series of failures.
However, Boeing concluded that with its twin Trent 1000 engines still running, ZA002 was “in a configuration that could have been sustained for the time required to return to an airport suitable for landing from any point in a typical 787 mission profile,” a defense of the 2008 Federal Aviation Administration’s special condition imposed on the aircraft’s electrical system, as well as its sought-after extended twin engine operations (ETOPS) certification.
Since their November 9 grounding, Boeing has received permission from the FAA to relocate three 787s. ZA001 and ZA005 returned to Boeing Field from remote testing in South Dakota and California, respectively, and ZA004 was ferried to the company’s Everett facility for maintenance.
Fancher added “re-positioning these airplanes back to Seattle will better prepare us for any modification that are needed as a result of this event.”
The extent of those modifications is another unknown and covers a wide spectrum of possibilities from a limited software modification all the way to complete redesign of the more-electric systems architecture of the 787.
At its inception, the Boeing used the 787 to push the outer envelope aerospace manufacturing, materials and systems, the three attributes that define an aircraft’s development.
The airframer had encountered great pain with the 787′s globally distributed supply chain in 2007 and 2008, a composite structural flaw in the aircraft’s side-of-body in 2009, and now in 2010 a potentially significant change to the aircraft’s electrical system.
Late discovery of design changes following treacherous incidents is not new to Boeing commercial development programs.
Nearly 28 years to the day earlier, the third of five 757 flight test aircraft suffered severe engine damage during a natural ice build up test on its Rolls-Royce RB211 engines,
An FAA representative onboard the aircraft, which was also being co-piloted by an FAA pilot, said at the time of the incident remarked: “We almost lost one.”
The incident prompted a late design change engine that was not validated by the FAA until nearly the last minutes before the type was handed over to Eastern Airlines in late 1982, followed by its January 1983 entry into service.