Date: 201204
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Light: Daylight
Aircraft: B767-300 and 300 ER
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Parked
Aircraft component: Leading Edge Slat
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Flying
Human factors: Other / Unknown; Situational Awareness
Anomaly: Aircraft Equipment Problem Critical
Detector: Person Maintenance
When detected: Routine Inspection
Result: Aircraft Aircraft Damaged; General Maintenance Action; General Flight Cancelled / Delayed
Contributing factors: Manuals; Procedure; Human Factors; Aircraft
Primary problem: Aircraft

Narrative: Captain and I flew company ETOPS B767-300 from ZZZ-ZZZ1. I was the pilot flying and the approach; landing; roll out; and taxi-in all seemed normal for ZZZ1. If the Leading Edge (L/E) Slat failed during any of the flying phases; it would have been hard to detect without an aural warning and EICAS due to the usual adverse roll and pitch issues (gusty; variable winds) associated with an approach into ZZZ1. We exited Runway X and taxied back to the gate area; crossing Runway Y; staying in contact with Tower the entire time (she activated 121.9 Ground at that time; but told us to stay with her.) I retracted the slats/flaps after leaving the runway and completed the After Landing Checklist. Captain fuel-chopped the left engine taxiing in and we parked; shut down; completed all checklists and paperwork; then exited the aircraft. I was not aware that there was an issue with the L/E Slat until the next day. At no time during our approach; landing; roll out; taxi in; and shut down was there any aural warning as to a L/E Slat Disagree. Amber EICAS messages to that effect never occurred and if they came on after the left engine was fuel-chopped; may have been lost in the normal shutdown messages.Without an aural and visual warning and without the L/E Slat Protection System preventing extension or retraction with a damaged slat; there is no way we could have known about the damaged slat or even taken any action. If the Protection and Warning Systems failed in flight with a damaged slat; the end result could have been much worse if the weather was marginal or if the crew was less experienced. Even if the slat and warning and protection system failure occurred on the ground; this raises serious safety concerns on my part about the reliably of the flap safety systems on our B767's. I am not sure when the Ground crew noticed the damaged slat. It was well after we left. Why is unknown. That is the part that concerns me. Maintenance is ongoing. Hard to suggest anything at this time because there are too many unknowns.

Callback: Reporter stated the left wing outboard #3 leading edge slat was found damaged with the slat canted up on one end and down on the other. Initially; Flight Operations thought the damage occurred on landing; however; he was recently informed the incident occurred after they had left the aircraft and prior to the outbound Flight crew arriving. The incident was considered a post flight maintenance-induced ground damage that occurred when Maintenance was cycling the flaps and slats. During the retract cycle the #3 Slat actuator either froze or a slat track had jammed. The outbound flight was canceled and the B767-300 ETOPS aircraft was out of service for two or three days; due to the amount of damage to the other slats. The #3 Slat was replaced.



Synopsis: A day after landing a B767-300 ETOPS aircraft; a First Officer was informed the #3 Leading Edge Slat was found damaged; canted sideways; and not fully retracted.