B737-700
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 171
Situational Awareness
Aircraft Equipment Problem Critical
Flight Crew Diverted; Flight Crew Landed As Precaution; Flight Crew Overcame Equipment Problem; General Declared Emergency
Aircraft; Human Factors
I was the Pilot Flying. During climb; passing approximately FL320 to FL330 the number one Bleed Trip Off light illuminated. We followed the QRH and the light extinguished. We continued to climb and approximately three to five minutes later; the number one bleed valve tripped again. We followed the QRH again but this time we couldn't keep the light extinguished. Following the QRH; we turned the left pack off to prevent two pack operation from one bleed source and turning the remaining pack to high flow. At the same time we were leveling off at FL400. We now started to analyze our situation of operating at FL400 with one pack and the ramifications of our malfunctioning aircraft further down line. During that discussion; the right pack tripped off. We both immediately felt the cabin altitude climbing and the F/O immediately donned his oxygen mask. I saw the cabin rate indicator climbing toward 1;000 fpm. I then donned my oxygen mask as well. We started a descent and the F/O declared an emergency. I initially had problems communicating because I didn't realize my boom MIC was blocking my mask MIC. Passing through approximately FL350 to FL360; I attempted to regain the right pack by pressing the reset button. It was successful and we continued our descent at a more comfortable rate. We referenced the QRH for Cabin Abnormal Warning/Abnormal pressurization; Pack Trip Off; and Emergency Descent. The passenger oxygen masks never deployed and I failed to record how high the cabin altitude actually reached. We continued our descent to 10;000 feet as a precaution and made contact with our Dispatcher. She was informed of our situation including malfunctions. We then made the decision to divert. I made a PA informing the customers of an aircraft problem that necessitated a descent to a lower altitude and we would be diverting as a precaution. The rest of the flight; descent; and landing were uneventful. After the PA; I talked with the flight attendants and they all reported they felt the cabin climbing as well. They also reported the passengers were pretty calm during the whole event and many were complimentary over the handling of the situation; which I attribute to the calm professionalism of the inflight crew. All connecting passengers were accommodated to their destinations and the remaining passengers continued with us on another aircraft.
Climbing out between FL320 and FL330 had a left BLD trip off light. Accomplished QRH BLD trip off checklist. Pushed trip reset. Reset the BLD trip off light. Within three minutes; left BLD trip off light. Accomplished QRH BLD reset itself. Within one minute. Left BLD trip off light. Performed QRH for BLD light not extinguishing. Turned off left pack. Leveling at FL400; right pack trip off light. Felt ear drums popping and noticed cabin altitude increasing. Donned oxygen mask and established communication. Captain started to descend at that time so I declared an emergency and told ATC that we were descending. While descending the Captain pushed the trip reset and that reset the left BLD trip off light and the right pack trip off light. The aircraft pressurized like normal. We continued the descent to 10;000 feet and told ATC that PSI was under control. We decided to divert to have the aircraft looked at. I think we started to descend too early and could have waited longer before descending.
B737-700 flight crew experiences a left bleed trip passing FL320 for FL400; which is successfully reset. Bleed trip reoccurs at FL400 and cannot be reset; resulting in the left pack being turned off in compliance with QRH. The right pack then trips and an emergency descent is initiated. During the descent both packs are reset successfully but the crew elects to divert for maintenance.