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ASN Wikibase Occurrence # 177632
Last updated: 10 December 2020
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Type:Silhouette image of generic C150 model; specific model in this crash may look slightly different
Cessna 150M
Registration: N3601V
C/n / msn: 15076559
Fatalities:Fatalities: 2 / Occupants: 2
Aircraft damage: Written off (damaged beyond repair)
Location:Lewisfield Plantation - Moncks Corner, South Carolina -   United States of America
Phase: En route
Departure airport:Moncks Corner, SC (MKS)
Destination airport:N. Myrtle Beach, SC (CRE)
Investigating agency: NTSB
The pilot of the F-16, who was operating on an instrument flight rules (IFR) flight plan, was in contact with air traffic control (ATC) and was provided radar vectors for a practice instrument approach to Charleston Air Force Base/International Airport (CHS), Charleston, South Carolina; the F-16 descended to an altitude of about 1,600 ft mean sea level as instructed by the air traffic controller. Shortly thereafter, the Cessna departed under visual flight rules (VFR) from a nearby nontowered airport; the Cessna pilot was not in contact with ATC, nor was he required to be, and had not requested traffic advisory (flight-following) services. As the Cessna continued its departure climb, the airplanes converged to within about 3.5 nautical miles (nm) laterally and 400 ft vertically, triggering a conflict alert (CA) on the controller's radar display and an aural alarm. About 3 seconds later, the air traffic controller issued a traffic advisory notifying the F-16 pilot of the position, distance, and indicated altitude of the radar target that corresponded to the Cessna, stating that the aircraft type was unknown. When the F-16 pilot replied that he was looking for the traffic, the controller issued a conditional instruction to the F-16 pilot to turn left if he did not see the airplane. The F-16 pilot did not see the airplane and responded, asking "confirm two miles?" The controller responded, "if you don't have that traffic in sight turn left heading 180 immediately." As the controller began this transmission, the F-16 pilot initiated a standard rate (approximately) left turn using the autopilot so that he could continue to visually search for the traffic; however, the airplanes continued to converge and eventually collided about 40 seconds after the controller's traffic advisory notifying the F-16 pilot of traffic. (Figure 1 in the factual report for this accident shows the calculated flight tracks for the Cessna and F-16.)

Air Traffic Controller and F-16 Pilot Performance

During postaccident interviews, the controller reported that when she observed the Cessna's target on her radar display as it departed, she thought that the airplane would remain within its local traffic pattern, which was not the case. Therefore, it was not until the airplanes were within about 3.5 nm and 400 vertical ft of one another that the controller notified the F-16 pilot of the presence of the traffic by issuing the traffic advisory, which was about 3 seconds after the ATC radar CA alarmed. (Federal Aviation Administration [FAA] Order 7110.65, Air Traffic Control, paragraph 2-1-21, "Traffic Advisories," states, in part, that a controller should "Unless an aircraft is operating within Class A airspace or omission is requested by the pilot, issue traffic advisories to all aircraft (IFR or VFR) on your frequency when, in your judgment, their proximity may diminish to less than the applicable separation minima. Where no separation minima applies, such as for VFR aircraft outside of Class B/Class C airspace, or a TRSA [terminal radar service area], issue traffic advisories to those aircraft on your frequency when in your judgment their proximity warrants it. ")

When the controller issued the traffic advisory, about 40 seconds before the eventual collision, the F-16 and the Cessna had a closure rate of about 300 knots. If the F-16 pilot had reported the Cessna in sight after the controller's traffic advisory, the controller likely would have directed the F-16 pilot to maintain visual separation, which is a common controller technique to separate aircraft. While the controller tried to ensure separation between the airplanes, her attempt at establishing visual separation at so close a range and with the airplanes converging at such a high rate of speed left few options if visual separation could not be obtained.

The options available to the controller when issuing instructions to the F-16 pilot to avoid the conflict included a turn, climb, some combination thereof, or not issuing an instruction at all. (An instruction to descend was not a
Probable Cause: The approach controller's failure to provide an appropriate resolution to the conflict between the F-16 and the Cessna. Contributing to the accident were the inherent limitations of the see-and-avoid concept, resulting in both pilots' inability to take evasive action in time to avert the collision.


FAA register:

Safety recommendations:

Safety recommendation A-16-51 issued 15 November 2016 by NTSB to FAA
Safety recommendation A-16-52 issued 15 November 2016 by NTSB to FAA



photo: NTSB

Revision history:

07-Jul-2015 15:52 gerard57 Added
07-Jul-2015 16:14 gerard57 Updated [Aircraft type, Narrative]
07-Jul-2015 16:25 harro Updated [Aircraft type]
07-Jul-2015 16:25 harro Updated [Aircraft type]
07-Jul-2015 16:25 harro Updated [Source]
07-Jul-2015 19:22 Iceman29 Updated [Source, Narrative]
07-Jul-2015 21:16 CTYONE Updated [Total fatalities, Total occupants, Source]
08-Jul-2015 16:04 Geno Updated [Time, Aircraft type, Registration, Cn, Other fatalities, Location, Nature, Source, Narrative]
11-Jul-2015 07:24 Chieftain Updated [Nature, Departure airport, Destination airport]
13-Nov-2016 18:44 Anon. Updated [Source]
16-Nov-2016 18:58 harro Updated [Time, Departure airport, Destination airport, Embed code, Narrative, Photo, ]
21-Dec-2016 19:30 ASN Update Bot Updated [Time, Damage, Category, Investigating agency]
01-Dec-2017 15:02 ASN Update Bot Updated [Other fatalities, Departure airport, Destination airport, Source, Narrative]

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