B737-700 flight crew experiences a left Wing Body Overheat at FL410 and complies with QRH procedures; including diversion due to forecast icing at destination. During descent passing FL390 The right wing body overheat illuminates; necessitating an emergency descent.
Synopsis
B737-700 flight crew experiences a left Wing Body Overheat at FL410 and complies with QRH procedures; including diversion due to forecast icing at destination. During descent passing FL390 The right wing body overheat illuminates; necessitating an emergency descent.
Narrative
We received a Left Wing Body Overheat light about 1;000 NM away from destination. Following the QRH we closed the isolation valve switch; turned off the left pack switch; the number one bleed switch; and verified the wing anti-ice switch was off. At that point the wing body overheat extinguished. We communicated with Dispatch and Maintenance Control. Because of existing icing conditions at destination we were unable to continue. We coordinated a diversion plan to ZZZ where the weather was VFR and planned to land with 11;000 LBS of fuel. A little over 200 NM away from ZZZ ATC cleared from FL410 to FL340. Passing FL390 the Right Bleed Trip Off light illuminated. I quickly glanced at the QRH as I already had it out from the previous checklist and pushed the trip reset button. We both noticed the cabin starting to rise through 9;000 FT so we donned our oxygen mask and initially had trouble establishing communications because we both forgot we had to push a switch to talk. When it clicked that we had to press the intercom switch we established communications. I don't know how long it took but it seemed like a while. During the time of trying to establish communications the Captain started the emergency descent and I declared a depressurization emergency descending to 10;000 FT. I then looked up to put the start switches to FLT and continued on with the Bleed Trip Off Checklist with the bleed not able to reset. I then looked to see if we were in a good emergency descent condition verifying that all the steps had been accomplished. The Captain was flying a great emergency descent.I began to review the Cabin Altitude Warning or Rapid Depressurization Checklist as the cabin altitude passed 14;000 FT. Before accomplishing the full procedure; I quickly cycled the bleed switch off then on and pressed the trip reset button once again. The Bleed Trip light went out and I selected the pack back to auto. At that point the pack started to stabilize the cabin. The cabin reached 15;000 FT at its highest point when it started to reverse its' direction. The cabin altitude descended below 10;000 FT before the aircraft reached 10;000 FT. When the pressurization was stabilizing I reviewed and completed the Emergency Descent Checklist. The cabin pressurization and temperature both looked normal. The Captain notified the flight attendants and the passengers of the situation. The flight attendants confirmed the oxygen masks were indeed down as indicated. We evaluated our fuel load and notified Dispatch. We then informed ATC we would continue to ZZZ for a visual landing and we had recovered pressurization of the aircraft.I think the emergency descent should be a memory item once again. We very much need hot mics in all the aircraft. Our initial confusion about the final step of pushing the toggle switch to talk took up valuable time. That is one of the first times I have ever pushed that switch. I also had to push it while running checklists and moving switches. This is a great example of why lack of hot mics is a safety of flight issue.
Second reporter narrative
We had a Wing Body Overheat on the left side. The QRH had us shut the left bleed off and required us to change our destination due to an Airmet for ice at destination. When given a step-down altitude from FL390 to FL340; the right bleed trip off light illuminated. We asked for lower while continuing our descent to FL340 and ATC said unable. We started to lose cabin pressurization. We donned our oxygen masks attempted crew communication. We declared an emergency and said we were going to 10;000 FT. I was the pilot flying and the First Officer was running the QRH Checklists. We regained control of the right bleed through about FL180. Once the cabin altitude was below 10;000 FT we pulled our oxygen masks off and made sure we communicated with the flight attendants; passengers; ATC; Dispatch; and each other. We continued on and landed safely. Upon reaching the gate the amount of personnel and the questions being asked made it a little harder to make sure everything that needed to be done got done. I wrote up a couple write ups on the airplane but I later called Maintenance because I felt I had overlooked a writeup. I went back towards the aircraft and called Maintenance Control about this to see if they wanted me to add it. They informed me they would take care of any additional write ups. We were pulled from flight duty and deadheaded back to base. After evaluating that decision I think it was the correct action by Management because we would have been thinking about this flight while flying the next one.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.