Date: 201404
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Light: Daylight
Aircraft: Medium Large Transport
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Landing
Airspace: Class B ZZZ
ATC / advisory: Tower ZZZ
Reporter organization: Government
Reporter function: Supervisor / CIC
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Communication Breakdown
Second reporter function: Captain
Anomaly: ATC Issue All Types; Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Other / Unknown
Detector: Person Air Traffic Control; Person Flight Attendant
When detected: Taxi
Result: Air Traffic Control Issued New Clearance; Flight Crew Landed As Precaution; Flight Crew Returned To Gate
Contributing factors: Aircraft; Equipment / Tooling
Primary problem: Equipment / Tooling

Narrative: Aircraft X had previously departed and we were advised (by TRACON) thereafter that they planned on returning to land here due to an indication that a panel was open and they requested no assistance. A low-level potential emergency alert was passed on to the Port Authority; and they responded with several fire trucks as a preemptive measure. After Aircraft X landed and was turning off Runway X (the only active runway at the time); I noticed an unidentified target on the ASDE-X. This target was just behind them as they exited. I immediately advised the Local Controller of this and seconds later determined with binoculars this was not a false target but a large piece of metal. Local Controller quickly advised the following aircraft (on short final) that debris was on the runway. This flight did land without incident but was visibly steering well left of centerline to avoid the hazard. Fortunately; there was not enough space between these two arrivals to squeeze an awaiting departure in between. As stated in my previously filed report under 'Safety Problem'; the ASDE-X never issued an alarm. As the second aircraft was landing the Port Authority's Duty Officer that responded along with the emergency trucks advised that there were several areas of debris left by the Aircraft X and the runway was immediately closed. Two aircraft were given go-around instructions; departures were stopped and the TRACON began holding arrivals for at least 4 minutes as the hazard was removed. The severity of the damage incurred by the Aircraft X (right engine cowling torn) became apparent only after the debris had been spotted and they had turned the aircraft eastbound onto the taxiway. From the Tower vantage point; this side of the aircraft was not visible on the Visual Approach. As a witness to this; I can only say that the event qualified as a significant safety hazard. And that it was very lucky to have occurred during daylight hours. I am relieved we avoided a potential 'Concord-like; catastrophic event.Other than recommendations given in my previous report relating to this: The TRACON provided no extra space on these succeeding; arriving aircraft - which would have been nice. It is not unusual for a departing aircraft to return to the field for precautionary reasons; but - when they do - this instance shows the benefit that extra time could provide. In this case; there was very sufficient room behind the arriving aircraft in order for them to have done so. However; like I said above; being that we were a single runway operation at this time it is a good thing that there was not a lot of space as we likely would have had a departure directly behind Aircraft X. Aircraft X flight crew gave us no indication that part of their plane was left on the runway. Primary debris (which was picked up on the ASDE-X) was mid-field between taxiways Tango and Juliet; about where most departing aircraft are reaching V1 speed; or the point of no stopping before the water off the end of [our departure airport's] runway. Though I personally work the CIC position rarely; from my training I seem to recall that selecting the 'Significant Event' check box in a required report [this] is done when an incident that is potentially newsworthy occurs. The wreckage that was left on the runway potentially witnessed by passengers of the arriving airline as well as any passenger on board Aircraft X able to see the tremendous damage on that side's engine may have led them to be truly; rightfully scared for their safety. So when I hear the powers that be directing my supervisor to not qualify this as significant; it boggles my mind that this real and present danger that existed can be seemingly written off as 'not a big deal'. Clarification on logging events in that system and qualification procedures might need to be reviewed.


Second narrative: Met copilot at aircraft; preflight was accomplished with no issues noted; normal departure; very nice smooth; clear morning. Shortly after cleanup Number 1 Flight Attendant rang to relay a passenger had reported a loose panel on the right wing. My first thoughts were of a 'shark bite' flap or perhaps a floating spoiler. All cockpit indications were normal; no unusual vibrations; roll; yaw; or noise. Based on the lack of any abnormal indications my first inclination was to continue our climb out. I asked for more information and the Flight Attendant offered to take a cell phone picture; which was brought it to the cockpit. The picture appeared to be an unknown; rectangular panel on the wing; obviously open. At this point we advised Approach that we would like to return. Based on our landing weight; approximately 133 KTS; well below maximum; the flight conditions; and the lack of any indications of a serious problem indicted by the performance and feel of the aircraft we elected to return to [our departure airport]. I decided not to declare an emergency; we were very close to [our departure airport]; and my perception that this was a nuisance; not an emergency situation. At this point we assumed it would be a relatively minor fix to close whatever was open. The touchdown was smooth and roll out was non eventful from our perspective in the cockpit. On taxi in another aircraft reported that we had lost a part on the runway. We both assumed the open panel had torn loose. Only after parking did we realize that the right engine cowl had actually blown open and the mysterious panel was actually a piece of engine cowl that had been bent over the wing. The picture was a great idea; but from the angle I could not exactly identify the object. I should have requested another from a different angle. I have to assume the inboard nacelle was being held shut or close by air forces. There was never any mention of an engine panel; we all were thinking small wing panel. If we had known of the cowl; nacelle problem I would have declared an emergency; opted for the longer runways of [a nearby airport] and hopefully would have used little or no reverse. This may have mitigated the damage upon landing. I also knew [our departure airport] had maintenance; and several more flights to [our destination]; this also influenced my decision to return to [our departure airport] if indeed the aircraft was to go out of service. My First Officer is very conscientious and thorough. I have no doubts that he performed a professional preflight inspection. Perhaps we should review the guidance on the cowl latch preflight section.


Synopsis: Air carrier aircraft had engine cowling depart the aircraft on departure. Controller advises Local Control and city closes runway due to large amounts of debris on runway.