Narrative:

Pilot bulletin XXX discusses the recent approval of the 'APU on demand' program for ETOPS flights in the 737. The bulletin; however; gives no information about exactly what components have been modified and what data has been collected in order to support this program. Absent additional information; I have serious safety concerns regarding this operation. The 737 was not originally designed to operate 180 ETOPS. It is already one level lower on the safety ladder than the other two-engine airplanes that have an instantaneous backup source of electrical power available should both engine generators quit. That's why we run the APU in ETOPS airspace: the 737 doesn't have an hmg (hydraulic motor generator) or a RAT (ram air turbine); and running the APU is the only way we have an instantaneous backup source of electrical power.so now we're going to leave the APU off and hope it starts if we need it when both engine generators quit [over the ocean]? The checklist in the 737 for a dual engine generator failure says; 'APU start attempts are not recommended above 25;000 feet. With both busses off; only one start attempt is recommended.' the implication is that in this situation we're supposed to descend to FL250 on battery power prior to attempting an APU start. And while we're making this descent in non-radar airspace; we can't talk to anyone because the HF radios don't work on battery power. The autopilots don't work; the pressurization is manual control only; the right IRS drops offline after five minutes; the fuel pumps don't work; and the engines may flame out (that's what the checklist says). And then what happens if the APU doesn't start? In that case; in all likelihood we're going to have a crash after the battery dies. Seriously; how did this pass the scrutiny of the supposed safety management system? And the only information the pilots get is; 'tech ops is modifying aircraft components in order to improve APU start capability.' what are they modifying? Does it improve the start reliability to 100% successful up to the service ceiling of the airplane after an extended cold soak?the company chose to operate the 737; an airplane that already has fewer systems redundancies than other airplanes; on 180 ETOPS routes. Now you're removing the only backup source of electrical power and telling us to just hope it works if we really need it? I just can't buy the argument that it's an equally safe option; particularly when the details supporting this decision are kept hidden.

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Original NASA ASRS Text

Title: B737 Captain questioned the wisdom of a new APU procedure within the ETOPs area in flight.

Narrative: Pilot Bulletin XXX discusses the recent approval of the 'APU On Demand' program for ETOPS flights in the 737. The bulletin; however; gives no information about exactly what components have been modified and what data has been collected in order to support this program. Absent additional information; I have serious safety concerns regarding this operation. The 737 was not originally designed to operate 180 ETOPS. It is already one level lower on the safety ladder than the other two-engine airplanes that have an instantaneous backup source of electrical power available should both engine generators quit. That's why we run the APU in ETOPS airspace: the 737 doesn't have an HMG (Hydraulic Motor Generator) or a RAT (Ram Air Turbine); and running the APU is the only way we have an instantaneous backup source of electrical power.So now we're going to leave the APU off and hope it starts if we need it when both engine generators quit [over the ocean]? The checklist in the 737 for a dual engine generator failure says; 'APU start attempts are not recommended above 25;000 feet. With both busses off; only one start attempt is recommended.' The implication is that in this situation we're supposed to descend to FL250 on battery power prior to attempting an APU start. And while we're making this descent in non-radar airspace; we can't talk to anyone because the HF radios don't work on battery power. The autopilots don't work; the pressurization is manual control only; the right IRS drops offline after five minutes; the fuel pumps don't work; and the engines may flame out (that's what the checklist says). And then what happens if the APU doesn't start? In that case; in all likelihood we're going to have a crash after the battery dies. Seriously; how did this pass the scrutiny of the supposed Safety Management System? And the only information the pilots get is; 'Tech Ops is modifying aircraft components in order to improve APU start capability.' What are they modifying? Does it improve the start reliability to 100% successful up to the service ceiling of the airplane after an extended cold soak?The company chose to operate the 737; an airplane that already has fewer systems redundancies than other airplanes; on 180 ETOPS routes. Now you're removing the only backup source of electrical power and telling us to just hope it works if we really need it? I just can't buy the argument that it's an equally safe option; particularly when the details supporting this decision are kept hidden.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.