FlightFollowerATC Suspended After Directing Southwest 737 to Inspect NORDO Aircraft, (Loss of Separation) 2011
On 27 March 2011, Southwest Airlines Flight 821 was approaching Orlando when controllers asked the Boeing 737 crew to visually inspect a Cirrus SR-22 that had been out of radio contact. The instruction created a dangerous situation because the two aircraft were assigned the same altitude. The Southwest crew eventually saw the Cirrus, but the aircraft came within 100 feet vertically and 0.1 nautical mile laterally. The event became an NTSB investigation into a loss of separation and the handling of an unresponsive aircraft.
Accident Facts
- Date
- 27 March 2011
- Registration
- N293WN / N1487C
The Cirrus was not simply ignoring ATC
The NTSB record provides important detail that is easy to lose in the phrase 'NORDO aircraft.' The Cirrus pilot reported that he continued hearing other traffic but could not establish contact with controllers. He tried several frequencies and attempted to reach Jacksonville Center, while trying to determine how to continue toward Kissimmee.
The aircraft was therefore not described as intentionally refusing to communicate. The problem was a communications breakdown that left controllers without normal two-way contact and the pilot without a reliable way to receive instructions.
The 737 was turned into the search aircraft
Controllers asked the Southwest crew to fly close enough to the Cirrus to look for signs of a problem. The crew agreed and was vectored toward the aircraft. Both aircraft were assigned 11,000 feet, making the inspection itself a separation risk.
When the Boeing approached, the Cirrus pilot saw the large jet coming from behind and received traffic alerts from the aircraft's onboard system. The NTSB recorded the closest point of approach as 100 feet vertically and 0.1 mile laterally, far inside the normal IFR separation standard of 1,000 feet or three nautical miles.
The incident exposed a problem in the response to lost communications
The Southwest crew's role was to provide visual information, not to become responsible for separating the aircraft. The NTSB record describes the request as an attempt to determine whether the Cirrus had a visible problem, but the resulting geometry created a near-midair situation.
After the encounter, the Cirrus established communication with Jacksonville Center and was vectored to Kissimmee, where it landed uneventfully. Southwest continued to Orlando. The incident therefore ended without a collision, but the investigation showed how quickly a response intended to improve situational awareness could create a second hazard.
The documented finding
“The closest point of approach between the two aircraft, both assigned operating altitudes of 11,000 feet MSL, was 100 feet vertical and 0.1 mile lateral.” — National Transportation Safety Board, OPS11IA428
Conclusion
The important lesson from OPS11IA428 is not that a radio-silent aircraft is automatically dangerous. The Cirrus pilot was trying to re-establish contact. The critical issue was how the system responded to the communications failure. Using a large passenger aircraft as a visual observer placed two aircraft on converging paths at the same altitude. The NTSB investigation documented the resulting loss of separation in precise terms, showing why procedures for handling NORDO aircraft must preserve separation even while controllers are trying to determine whether the aircraft needs assistance.