Airprox Serious incident Boeing C-40B (737-700BBJ) ,
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ASN Wikibase Occurrence # 314506
 
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Date:Monday 18 April 2011
Time:17:06 LT
Type:Silhouette image of generic B737 model; specific model in this crash may look slightly different    
Boeing C-40B (737-700BBJ)
Owner/operator:United States Air Force
Registration:
MSN:
Fatalities:Fatalities: 0 / Occupants:
Aircraft damage: None
Category:Serious incident
Location:Camp Springs, Maryland -   United States of America
Phase: Approach
Nature:Military
Departure airport:
Destination airport:Camp Springs-Andrews AFB, MD (ADW/KADW)
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
Narrative:
A Boeing 737 (B737), callsign EXEC1F and a heavy Boeing C-17, call sign Reach 3115, were being provided radar vectors for instrument landing system approaches to the runway by a controller at the Potomac Terminal Radar Approach Control (TRACON) facility. The controller vectored the C-17 onto the base leg of the traffic pattern ahead of the B737 to join the localizer for the approach. At this point, the airplanes were separated by 4.45 miles on a converging course with a closure rate of 180 knots. The C-17 was subsequently vectored to join the localizer and cleared for the approach.
The controller then issued a wake turbulence advisory to the B737 and informed the pilot he would be 4 miles in trail of the C-17. The pilot of the B737 acknowledged the advisory, but, at this point, the airplanes were 3.62 miles apart. The minimum required wake turbulence separation was 5 miles. Both airplanes were directed to contact the air traffic control tower local controller. As both airplanes reduced their speeds for landing during final approach, their separation was reduced to 2.81 miles. The minimum instrument flight rules separation was 3 miles. The local controller authorized the B737 to make "S" turns on final approach to increase separation; however, when the B737 was 2 miles from the landing threshold, the B737 pilot told the local controller, "it doesn't look like we're going to make this," since the C-17 was still conducting the landing roll on the runway. The B737 pilot was instructed to perform a go-around, entered a left downwind for the runway, and landed uneventfully.
The TRACON controller responsible for the wake turbulence operational error reported after the incident that he confused the minimum wake turbulence separation requirements for a B737 following a C-17 with the requirement for a B757 following a B757. The B757 requirement was 4 miles. The TRACON controller had been involved in 4 other operational errors in the 4 years preceding this incident.

Probable Cause: The misapplication of wake turbulence and instrument flight rules (IFR) separation criteria by air traffic controllers.

Accident investigation:
cover
  
Investigating agency: NTSB
Report number: OPS11IA499
Status: Investigation completed
Duration: 8 months
Download report: Final report

Sources:

NTSB OPS11IA499

Location

Revision history:

Date/timeContributorUpdates
02-Jun-2023 17:56 ASN Update Bot Added
03-Jun-2023 06:23 harro Updated

Corrections or additions? ... Edit this accident description

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