Tuesday, March 03, 2009

Chicago-O'Hare air traffic controller blamed for near mid-air collision

NTSB logoThis past July, there was a near mid-air collision at Chicago-O'Hare International Airport between a departing American Eagle ERJ-145, and a Learjet LR60 that was arriving on an intersecting runway. No one was injured, and neither aircraft was damaged in the July 22, 2008 incident, but it was a very close call: according to ground radar (ASDE-X) analysis and radar replay, the LJ60 passed 325 feet above and slightly behind the departing E145. 

A 'probable cause' report issued recently by the U.S. National Transportation Safety Board (NTSB) cites "[t]he LC-10 [Local Control] controller's failure to ensure the appropriate separation between two airplanes operating on runways where flight paths intersect" as the cause the incident.

Here is the timeline of events, from the NTSB report:
At 1243:09, the ORD tower local control 10 (LC-10) controller instructed the E145 pilots to taxi into position and hold on runway 32L at taxiway M. The LC-10 controller issued a wake turbulence advisory to the pilots and advised them to expect about a 2 1/2 minute delay before "we can getcha rollin". The E145 pilots acknowledged the clearance. The runway 32L/taxiway M intersection is approximately 8,800 feet from the runway 9R final approach path.

At 1244:57, the LJ60 pilot contacted the north local controller (NLC) and reported over Lance, the runway 9R outer marker, located about 4.1 nautical miles from the approach end of the runway. The NLC cleared the LJ60 pilots to land on runway 9R and advised them to "plan a left turn on runway 32R" during their landing roll. The LJ60 pilots acknowledged the clearance and repeated the exit information.

At 1245:27, the LC-10 controller cleared the E145 for takeoff stating, "...runway 32L at [taxiway] M, cleared for takeoff, turn right heading 330 [degrees]." The controller did not provide any information regarding the LJ60 that was about 2.5 miles from the runway 9R runway threshold. The E145 pilot acknowledged the takeoff clearance. At 1245:45, EGF298 commenced its takeoff roll.

According to the local monitor's statement, he recognized the potential conflict between the E145 and LJ60 and told the LC10 controller to advise the departing aircraft to stay low.

About 1246:13, when the LJ60 was about 3/4 of a mile from runway 9R, the NLC instructed the LJ60 pilots to "...go around maintain 4,000 [feet msl]." According to the LJ60 pilot-flying's (PF) statement, the pilot not flying observed the E145 on runway 32L and told the LJ60 pilot flying (PF) "Climb, climb, there is an MD80 on takeoff roll on [runway] 32R."

At 1246:19, the LC-10 controller advised the E145 pilots to "...stay low...stay low traffics above you."

At 1246:26, the ASDE-X data revealed that the closest recorded proximity occurred as the LJ60 passed about 150 feet laterally and about 325 feet above the E145. About 13 seconds later, the NLC instructed LJ60 pilots to "Turn right heading 140 [degrees], contact Chicago departure control on 127.4." The pilots acknowledged the clearance.

At 1246:27, the LC-10 controller instructed E145 pilots to "Climb and maintain 5 [thousand feet], sorry about that." A few seconds later, the pilots acknowledge the clearance.

At 1246:43, the E145 pilots said, "...it was interesting." About 19 seconds later, the LC-10 controller instructed the E145 pilots, "Contact Chicago departure 125.4." [NTSB ID: OPS08IA011A]
The report also includes statements from the pilots on both aircraft. The crew on the Lear spotted the ERJ nearly concurrently with the controller's go-around instruction. The PNF (pilot not flying) told the NTSB "...We never received a TCAS (Traffic Collision Avoidance System) advisory - either alert or resolution - during the go-around."

Meanwhile, the ERJ captain, who was the PF, said, "...As I called gear up after rotating, I see a Learjet at 11 o'clock converging directly with our flight path. I immediately leveled the aircraft at 200 feet above the runway to avoid a collision and maintained runway heading. The tower issued an alert to level off two seconds later, as the Lear [jet] passed directly over our cockpit. I am estimating 600 feet separation. The controller apologized."

The American Eagle first officer, who was the PNF, said, "...From my vantage point, all I saw was an aircraft directly above us moving left to right at no more than 200 feet of separation vertically. The Captain immediately initiated a level off at no more than 200 feet AGL until we were instructed to continue the climb. The tower apologized and continued working aircraft, handed us off to departure where the flight continued without further incident."

The NTSB report notes that "The LC10 position, located on the south side of the tower cab that has an external view of the runway 32L/9R intersections. The tower was equipped with digital radar and ASDE-X displays. ORD managers reported that the ASDE- X did not have crossing runway logic installed, and the ASDE-X did not alarm during the incident.