A First Officer reports damage to an aft pressure bulkhead door and floor plate of a B727 cargo freighter; caused by a hand operated type pallet jack that was not properly secured. Temporary repairs using an engineering order were not adequate resulting in a loss of cabin pressurization on the next flight; at FL290.
Synopsis
A First Officer reports damage to an aft pressure bulkhead door and floor plate of a B727 cargo freighter; caused by a hand operated type pallet jack that was not properly secured. Temporary repairs using an engineering order were not adequate resulting in a loss of cabin pressurization on the next flight; at FL290.
Narrative
Aircraft 'X' was being brought in to replace Aircraft 'Y' which was down for an engine change. Enroute; the crew flying Aircraft 'X'; had a pallet jack break loose and damage the aft pressure bulkhead door. Maintenance was notified and we were briefed about the damage. The crew and I arrived at the airport and were told by Maintenance that it would be a few hours for repairs. Maintenance received the engineering authorization for the repair and made the temporary repairs to the aircraft and installed the aft pressure bulkhead door from Aircraft 'Y' onto Aircraft 'X'. After repairs were completed; a Mechanic refused to sign off the repairs; stating they didn't make the repairs and wouldn't sign them off. The Mechanic then quit. Another Mechanic came in and inspected the aircraft repairs for some time and signed the aircraft off. We loaded the aircraft and began to taxi out. While taxing out the Captain received a call from the Company telling us not to depart and that the aircraft needed another inspection and signoff from another Mechanic. The other Mechanic was brought in and that Mechanic inspected the aircraft for about one hour and then signed it off for flight. We departed the airport without any problems. We completed the departure procedure with transition and continued the climb to FL290. Upon reaching FL290 the aircraft began to depressurize and the cabin altitude high alarm activated as the cabin was now above 10;000 feet and slowly climbing. We donned our oxygen masks and performed the appropriate procedures. The Captain transferred control to me with instructions to start a rapid descent to FL220 and not to declare an emergency. I advised ATC we needed an immediate descent for a pressurization problem and ATC cleared us for lower. After reaching FL220 the cabin stabilized at an altitude of about 8;000 FT. We then climbed up to FL230 (proper altitude for direction of flight and approved by ATC) and the Captain contacted the Company (the cabin remained at 8;000 FT). The Company indicated for us to continue to our destination. If the problem got worse; we were given a couple of preferred diversion airports. The Company also recalculated our fuel burns for the new lower flight level and indicated we had enough fuel to reach destination. We also experienced some avionics problems enroute. I suggested a couple of times that we should divert; but was over ruled by the Captain and the flight landed at destination without further incident. The Captain wrote up the pressurization system prior to the next crew arriving. The flight then departed with another crew for two more revenue legs before it was taken offline and flown to our heavy maintenance base.
NASA callback
Reporter stated their aircraft have a special smooth steel flooring that covers the cargo floor rollers and can be installed by two mechanics in approximately two hours; allowing the use of a hand operated pallet jack. The B727 was being ferried to another station; to replace another B727. Maintenance had installed the steel floor prior to the ferry; but did not secure the pallet jack to the floor tie downs. During rotation the pallet jack had rolled the entire length of the cabin floor and the jack forks had slammed into the aft pressure bulkhead door at floor level; with approximately 200 pounds of equipment weight still on the pallet jack. Reporter stated the aft pressure bulkhead door was replaced. Part of the engineering order temporary repair; also included using a silicon sealant to even out the door threshold plate that was bent; when the pallet jack forks had hit and wedged under the door and floor threshold plate. The silicon sealant was used to create a smooth surface to allow the door lower pressure seal to seat against and hold pressurization. Reporter stated he believes the problem with the Mechanics signing off the repair work; was due to the required inspection items (RII) not being properly accomplished. Reporter stated cabin pressurization loss occurred two times after the temporary repairs were signed off; before anyone realized; that whenever the cabin reached 5.9 PSI differential pressure; did the cabin pressure start dumping. Maintenance removed the aft pressure door bent floor threshold sill plate and found bent stringers and the floor plate cracked. The sealant had covered the crack. Only when the cabin differential pressure reached 5.9 PSI differential; would the pressure be great enough to actually force the floor plate crack to open up and start dumping the cabin pressure. Reporter stated the Flight Engineer was also responsible for verifying the pallet jack and tie downs were secure. They had also lost their ADI and GPS navigation during the first pressurization loss.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.