Colgan 3407 final approach chronology

Air traffic contol tapes that have surfaced regarding last night’s fatal crash of a Colgan Air Bombardier Q400 (flying as a Continental Express) on approach to New York’s Buffalo Niagara International Airport after a flight from Newark indicate that pilots were in the final stages of the approach and would have begun configuring the aircraft for landing, most likely lowering the landing gear and adding flaps.

The instrument approach chart for the instrument landing system (ILS) approach to Runway 23 at Buffalo is below, with expanded views and a transcipt (done by me) shown as well. Note that the airport elevation is 728ft and the normal ILS decision height is 1,060ft, or 332ft above ground level. Colgan 3407 appears to have been level at 2,300ft when some event precipitated the crash.

BUF ILS23.JPG

 

Here’s an expanded top-down view of the approach, showing the location of the plane where communications with Buffalo Approach Control begin. Below that is a sideview showing Klump (which is marked by a bolded X), also known as the outer marker or final approach fix, and its relationship to the airport, 4.4nm away. At typical approach speeds of about 120kt, the aircraft would take about 3 minutes to fly from KLUMP to the airport.

 

BUF_test1.jpg

 

 

ILS23_BUF.JPG

Communications from the air traffic control recordings start when the aircraft would have been approximately at the location labeled “Radio Call 1″ and flying at 2,300ft, the intercept altitude for the glideslope. The “outer marker” referred to in the recording is KLUMP, the location of a radio aid located 4.4nm from the runway end, a position where an aircraft has both left-right and vertical (glideslope) information on an ILS. Sections in ( ..) are my notes. 

Buffalo Approach - Colgan thirty-four zero seven. Three miles from Klump (the final approach fix intersection). Turn left heading two-six-zero (260 degrees). Maintain two-thousand three hundred (2,300ft) until established localizer (left-right guidance for an instrument approach – Localizer is shown as a triangle with the vertex on the airport). Cleared ILS approach runway 23

Colgan 3407 - Left two-sixty” (260 deg), two-thousand three hundred (2,300ft) until established (on the localizer) and cleared ILS 23 approach. Colgan thirty-four zero seven.

13 seconds later:
Buffalo Approach  - Colgan 3407 contact tower one two zero point five. (Buffalo air traffuc control tower frequency of 120.3 MHz). Have a good night.

Colgan 3407 – Thirty-four zero seven (shows that she acknowledged the call)

 

Below is roughly where the aircraft would have been at this time:

BUF_test2.jpg

 

53 seconds later (Colgan 3407 should have been over KLUMP and reported in to tower):

Buffalo Approach – Colgan thirty-four oh seven. Approach?

Colgan 3407 – No answer

The air traffic controller tapes are available on Flight’s website. Note the unanswered calls from Colgan 3407, and later, a request from Northwest 920 on departure to climb direct to 10,000ft in order to expedite passage through the icing. Controllers then request to officials notify state police and others to look for Colgan 3407 about 5 miles from the airport. The “marker” the controller refers to is KLUMP.

Icing, always a concern for commuter aircraft in winter weather, was reported on the approach (a Delta Airlines flight approaching the airport after Colgan 3407 reported picking up ice from 6,500ft down to 3,500ft during the approach. A departing aircraft also asked Buffalo controllers for a continuous climb to 10,000ft in order to quickly pass through the icing layer.

Investigators will invariably explore whether a configuration change or change in autopilot status may have caused an abrupt upset to the aircraft, an event that would have been picked up by the cockpit voice recorder and flight data recorder, assuming the devices survived the crash. Officials at the crash site reported very little lateral damage in the area, indicating a steep vertical descent.

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