ERA12LA356

The failure of the co-pilot to properly close and latch the passenger door before departure, and the flight crew's failure to ensure that the door was secure by using the door warning system. Contributing to the accident was the flight crew's inadequate use of checklists.

About 3 minutes into the positioning flight, at 3,000 feet, the flight crew heard a "loud bang" and became aware that the main passenger door had separated from the airplane. The pilot declared an emergency, diverted to a nearby airport, and landed without further incident. The separated passenger door was subsequently found on a nearby golf course. The co-pilot reported in a written statement that he closed the main passenger door and checked for a green light to ensure that it was secure. In a subsequent interview, he reported that he "believed" that the door warning lights were working, but he could not positively recall seeing the "Door Safe" light illuminated after closing the door. He also did not remember activating the "Recall" switch before takeoff. Ramp security video showed that the main passenger door appeared to close; it then re-opened momentarily and closed again before the airplane taxied out of the ramp area. The co-pilot reported that he re-closed the door because it did not secure on the first attempt. An examination of the recovered door and the door frame did not reveal evidence of a pre-existing mechanical malfunction or failure that would have precluded normal operation. The top half of the door was crushed from the impact with the ground, which prevented establishing the condition of door rigging before the accident. An examination of the fuselage revealed a skin puncture that matched the location of the door pull-out handle and is consistent with the door being in the open position when the puncture occurred. Although the door's external handle was found in the closed position, smudging on the fuselage was consistent with the handle's movement from the open to the closed position during impact with the fuselage. Although it is apparent from the cockpit voice recording that the flight crew referenced the pilot checklist at some stages during ground operations, crew challenge and response items were sporadically mentioned. After the sound of the passenger door closing, neither crewmember mentioned the door warning lights. At no point during ground operations through the takeoff sequence were the doors, door warning lights, or master caution system mentioned. The co-pilot mentioned the "Annunciator" check in the Before Takeoff checklist; however, no "Recall" response was noted on the recording. Activating the recall switch would have alerted the flight crew to an unsecured door before takeoff.

The cockpit voice recorder (CVR) and flight data recorder (FDR) were forwarded to the NTSB Vehicle Recorders Laboratory in Washington, DC for readout and examination. The CVR was a L-3/Fairchild FA2100-1020, serial number 000244915. The two-hour recording contained good quality audio information. The unit was undamaged and the audio content was extracted without difficulty. A CVR group was formed, including the CVR Group Chairman and representatives from Bombardier and Majestic Jet. The entire recording was not transcribed. The transcription began with the sound of a thunk and click, similar to a main cabin door closing, at 15:31:38 (HH:MM:SS). Three seconds later, a second click and thunk could be heard, consistent with the main cabin door closing and latching. There was no mention of door warning lights by either crewmember immediately after the door closing sounds. At 15:34:18, there was a sound of an engine increasing, similar to an engine starting. No mention of a "Before Start" checklist was noted. At 15:35:42, a sound similar to a second engine start was noted. At 15:36:22, the "After Start" checklist was called for. At 15:37:40, the "Taxi" checklist was called for. At 15:43:06, the flight was issued takeoff clearance. At no point during the ground operations through the takeoff sequence were the doors, door warning lights, or master caution system mentioned. During the "Before Takeoff" checklist, the co-pilot mentioned the annunciator; however, the pilot did not respond with "Recall" as is listed in the checklist item. For additional information on the CVR and its audio recording and transcript, refer to the Cockpit Voice Recorder Group Chairman's Factual report, located in the public docket for this accident investigation. The FDR was a Loral/Fairchild F1000, serial number 00633. The FDR contained about 174.4 hours of data. The recorder was in good condition and the data were extracted normally from the recorder. A review of the data revealed that the vertical and horizontal acceleration parameters were not working. The FDR data indicated the aircraft took off on a magnetic heading of about 92 degrees. During the entire flight, the aircraft commenced mostly left turns. At about 130 seconds after takeoff, the aircraft reached a maximum pressure altitude of 3,033 feet before beginning its descent. About 6.5 minutes later, the aircraft landed at a magnetic heading of about 95 degrees. For additional information on the FDR and its data, refer to the Flight Data Recorder Specialist's Factual Report, located in the public docket for this accident investigation. Integrity checks were performed on the main passenger door warning system and the aircraft master caution system. All lights associated with the door warning system were checked and illuminated when tested with the cockpit light test switch. No anomalies were found with the master caution light system, the "PASS DR READY" (passenger door ready) green light, or the "PASS DR UNLKD" (passenger door unlocked) amber light. An anomaly was found with the "PASS DR NOT RDY" (passenger door not ready) amber light. The light's designated ground was not available and the light would not illuminate when its circuitry was tested from the door interface. The PASS DR NOT RDY light illuminates only when the door T-handle is not stowed. According to the manufacturer, this anomaly would not affect the operation of the PASS DR READY (green) light as the PASS DR READY (green) light is an independent circuit. The three sets of splices from the cabin door warning system were examined at the NTSB Materials Laboratory. Each submitted splice had wiring installed on only one side of the splice. Each splice was x-rayed to determine if wiring at some point was present on both sides of the splice. There was no evidence of marks, scratches or any other damage consistent with a wire having been installed and then pulled out. In addition, there were no remains of wiring present in the open end. The integrity of the remaining door wiring harness found dangling from the airframe could not be verified because it was compromised (severed) when the main passenger door separated from the aircraft. The pushrod, connecting the upper latch cams and lower latch cams, was sent to the NTSB Materials Laboratory for failure analysis. The rod was bent approximately 45° at the center and had fractured at one of the threaded ends. The pushrod also showed two dents approximately 3 inches from the opposite and intact end of the rod assembly. The threaded bolt showed compressed thread crests on one side and outstretched thread valleys on the other side. The majority of the original threaded surfaces bore a layer of rust-colored oxidation. This surface oxidation was not present on any of the fracture surfaces. Examination of the fracture surface revealed dimple rupture, which is indicative of overstress. The cracked areas in the stretched thread valleys also displayed dimple rupture. No other indications of other failure modes, including corrosion leading to fracture, were found. The observed features are consistent with bending overstress of the pushrod. Aircraft Checklists The flight crew utilized a FlightSafety International Quick Reference Handbook checklist during ground operations prior to takeoff. On page N-4, (Normal Start), checklist item number 5 stated, "Doors….Checked/Secured." On page N-6, (Before Takeoff), checklist item number 8 stated, "Annunciator….Recall." Aircraft Systems The following descriptions for the passenger/crew entrance door, door warning system, and master caution and warning system were obtained from the Canadair Challenger Maintenance Manual. Passenger/Crew Entrance Door – Description The entrance door for passengers and crew opens downward and outward and is manually controlled from inside or outside the aircraft. Rollers are mounted on pull-in levers located on the fore and aft edges near the top of the door. Cams are secured to the fore and aft door frame in such a position to capture the rollers as the door approaches the closed position. This mechanism pulls the door into the full closed position to ease latch cam engagement. Guide plates are mounted below the pull-in levers on the door. These plates contact rollers mounted on the door frame and centralize the door as it closes. Four latch cams on the door rotate around four spigots on the door frame to hold the door closed. Two cams are located at the top edge of the door and one on each side at approximately the mid-point. The latch cams are rotated by a handle and a system of push rods and torque tubes. The upper cams have a detent in which a spring-loaded pawl seats. The handle assembly consists of a single-lever internal handle located on the forward side of the stair and an external handle. The external handle stows into a recess in the outer skin of the door and in this position, the recess acts as a lock for the latching mechanism. Door Warning System - Description The passenger/crew door warning system in the flight compartment consists of two amber lights and a green light. The amber lights indicate that the door is unlocked and not ready; the green light indicates a door ready condition. The amber unlocked and not ready conditions activate the master caution system causing the amber DOORS annunciator to come on and the master caution lights to flash. Proximity switches are mounted at each door latch. These switches, together with a proximity switch on the external door handle, cause the passenger/crew door UNLOCKED light to go out when the latches are in the fully latched position and the external handle is stowed. A proximity switch on the inner lever causes the passenger/crew door NOT RDY light to go out when the inner lever is stowed. Micro