Date: 201402
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: B737-400
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Takeoff / Launch
ATC / advisory: Ground ZZZ; Ramp ZZZ; Tower ZZZ
Aircraft component: Turbine Engine Thrust Reverser
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Troubleshooting; Distraction
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Maintenance; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Detector: Person Flight Attendant; Person Flight Crew; Person Passenger
When detected: Taxi
Result: Flight Crew Rejected Takeoff; Flight Crew Took Evasive Action; General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Procedure; Aircraft
Primary problem: Aircraft

Narrative: During the spool up process of the engines during the takeoff roll; the Captain noted the #2 'Reverser Unlock' light illuminated and immediately rejected the takeoff at an estimated speed of less then 20 KTS.  I notified Tower of the rejection and our intention to vacate the runway at the next right turn off the runway. We were instructed to contact Ground. Ground issued a taxi clearance back to the ramp.  Approximately thirty minutes after our block-in; the passengers and crew noted the cabin filling with a haze and an odor similar to dust; like a vacuum bag exploding in a room. We immediately sent cabin crew to investigate the issue. I entered the cockpit for signs of APU or cargo compartment fire. We concluded it was not a fire but could not locate the immediate cause within the airplane. We shut down the AC Packs as the haze increased and I further investigated outside the aircraft and talked to the Mechanic for the possibility he may have accidentally sprayed a chemical near the Pack inlet while working on the Thrust Reversers (T/Rs). His role appeared to have no effect. No dust or contamination of the outside air or on the ground near the aircraft could be located.  Concurrently; we ordered the buses back to the ramp and contacted Ground to have the Fire Department standing by for medical treatment and fire protection near the aircraft. We deplaned the passengers for both their protection and our own while we investigated the issue further. The Airport Rescue and Fire crews investigated the aircraft and found no signs of fire or evidence of the event with the AC Pack ON or OFF. No treatment was given to any of the 99 souls on board the aircraft.  The additional event unrelated to the original rejected takeoff caused our window to complete the trip to be exceeded; and the trip canceled. While onboard the aircraft completing the paperwork for the T/Rs MEL; the Flight Mechanic identified the suspected cause while onboard the aircraft when I switched AC Packs from the left to the right. The cabin filled with a slight odor and irritation that he recognized as Skydrol. He investigated the likely sources of the hydraulic leak and identified several loose connectors on a hydraulic distribution manifold aft of the rear bulkhead. He corrected the issue and wiped clean the affected areas to identify the any other possible points of leaks during subsequent tests.  After several hours of work and not being able to produce the occurrence again the aircraft was released for flight and we loaded our passengers (guards) in preparation for departure. As soon as loading completed the cabin again started to fill with the same haze and odor; again causing us to deplane the passengers.  The Mechanic then began further maintenance to clear any contaminates in the environmental system.  We as a crew were able to produce a slight puff once more during this initial process by cycling between packs and operation of the isolation valve.  After several hours of clean air; we opted to started engine #2 to push a higher volume and higher pressure airflow through the system to clear any further remaining possible contaminates.  We were not able to reproduce any further events and the aircraft was again released for flight.The aircraft maintenance inspections should include regularly inspections of the affected area. Insure proper torquing of fittings during all maintenance work. Tracking of fluids and analysis of fluid levels over periods of time to identify possible leaks and identifying their source may have identified the issue before the event. Keeping the aircraft washed and clean would also help in identifying normal venting and abnormal leaks.




Synopsis: A B737-400 takeoff was rejected after the #2 REVERSER UNLOCK light illuminated and while at the gate for maintenance the cabin filled with haze and a SKYDROL odor. Maintenance found loose hydraulic manifold connectors behind the aft pressure bulkhead.