PowerPoint Presentation

AIR TRAFFIC CONTROL HUMAN FACTORS CASE STUDY

| Integrated Safety Training Workshop: Human Factors

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ATC CASE STUDY

TranscriptDouble-click in Preview Mode to open

| Integrated Safety Training Workshop: Human Factors

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CASE STUDY DISCUSSION: SITUATION

What human factors influenced the United Airline dispatchers?

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CASE STUDY DISCUSSION: SITUATIONWere any mistakes, lapses, or slips made by the tower controllers?

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CASE STUDY DISCUSSION: SITUATIONWhat factors do you think contributed to the decisions made at the TRACON?

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ILT HUMAN FACTORS VIDEO 2

FEMALE NARRATOR:

Most incidents that occur in the operational environment contain human-factors issues. Let's walk

through a chain of events in a real-life example to see how such human-factors issues can lead to a

significant loss of separation.

MALE NARRATOR:

A chain of events began with two United Airlines aircraft, one inbound and one outbound at the same

time, having identical call signs. According to United Airlines procedures, when two United aircraft have

the same call sign and will be in the air at the same time, dispatchers must add an appendix to

differentiate them.

However, in this instance, two dispatchers in separate locations identified the issue and, in an attempt

to correct it, inadvertently chose the same appendix -- the letter "T."

While working departures, Local Controller 1 encountered a problem when trying to tag up the

outbound United 541T. The system wouldn't allow it because there was already an airborne aircraft

with the same call sign.

Local Controller 2 overheard the problem. This was an issue that occurred frequently at the airport, so

the controller believed the duplicate data block was the result of coasting. The controller decided to

help by doing a track drop that removed the inbound United 541T from the radar.

Local Controller 2 did not recognize from the available information that this aircraft, United 541T, was

active on an ILS for one of the parallel runways.

Meanwhile, at the TRACON, they had been experiencing ghosting target issues. Coincidentally, there

was a Flexjet in the same area in which the ghosting targets tend to appear and where the United data

block had just been dropped.

The sector weather at the TRACON included a severe tailwind that transitioned to a headwind, causing

aircraft to be fast on approach but slowing down as they descended.

The TRACON controller, for the sector where ghosting had occurred, was busy with the unbalanced

arrival distribution and focused on the area in which the compression was occurring, about 20 miles or

less from the airport.

At this time, the inbound United 541T checked on to the sector frequency at approximately 40 miles

from the airport.

The TRACON controller acknowledged the check-in and issued a speed instruction. Inbound United

541T was the last aircraft in a stream of traffic, so the controller foresaw a break in traffic.

The TRACON controller discussed the ghosting issue with other TRACON controllers, and they noticed

that the Flexjet slowed down but the ghosting United 541T didn't.

It was then that they began to suspect that the ghost target was actually an arriving aircraft.

At about the same time, inbound United 541T called twice on the radio, asking why they were rapidly

overtaking the SkyWest aircraft ahead of them. On the second call, the TRACON controller

acknowledged the United pilot.

After obtaining the aircraft's position, the TRACON controller gave an immediate climb instruction and

told the pilot to fly runway heading.

Simultaneously in the tower, Local Controller 1 broke out the leading aircraft to the left, re-establishing

separation and course divergence with the inbound United aircraft.

Throughout the event, the closest proximity between the two aircraft? .77 nautical miles.

FEMALE NARRATOR:

So, how did this happen? After the event, a human factors investigation was conducted to uncover the

human errors that caused this chain of events to occur.