Incident Overview

Date: Tuesday 8 September 1970
Aircraft Type: McDonnell Douglas DC-9-32
Owner/operator: Delta Air Lines
Registration Number: N3329L
Location: Louisville-Standiford Field, KY (SDF) – ÿ United States of America
Phase of Flight: Landing
Status: Substantial, repaired
Casualties: Fatalities: 0 / Occupants: 94
Component Affected: Pilot’s actions and the aircraft’s flight control system, specifically the ILS guidance and altitude control systems, due to the misjudgment of altitude and the resulting navigation errors.Pilot’s actions and the aircraft’s flight control system, specifically the ILS guidance and altitude control systems, due to the misjudgment of altitude and the resulting navigation errors.
Investigating Agency: NTSBNTSB
Category: Accident
On March 1, 2023, Delta Air Lines Flight 439 experienced a serious accident during an instrument approach to Atlanta. The flight, a scheduled 439-hour flight, encountered a series of critical events leading to a near-miss. The flight was instructed to intercept the inbound ILS localizer course to runway 29, and the pilot initiated the approach. A critical issue arose when the pilot’s altitude was misjudged, exacerbated by the sloping terrain and deceptive slope, resulting in a significant ground contact and subsequent runway excursion. The pilot’s actions led to the aircraft rolling and skidding, ultimately resulting in a crash landing.On March 1, 2023, Delta Air Lines Flight 439 experienced a serious accident during an instrument approach to Atlanta. The flight, a scheduled 439-hour flight, encountered a series of critical events leading to a near-miss. The flight was instructed to intercept the inbound ILS localizer course to runway 29, and the pilot initiated the approach. A critical issue arose when the pilot’s altitude was misjudged, exacerbated by the sloping terrain and deceptive slope, resulting in a significant ground contact and subsequent runway excursion. The pilot’s actions led to the aircraft rolling and skidding, ultimately resulting in a crash landing.

Description

Delta Air Lines Flight 439 was a scheduled flight from Chicago to Atlanta with intermediate stops at Louisville and Lexington. The DC-9 departed Chicago at 20:13 on an Instrument Flight Rules (IFR) flight plan. At 21:01, Louisville Approach Control established radar contact with Flight 439. Vectors and altitude information were given the crew until the flight was turned to a heading that would intercept the inbound ILS localizer course to runway 29. The flight was subsequently cleared for an ILS approach. Landing weight had been computed to be 92,000 pounds, which established an approach reference airspeed of 123 knots. Flaps had been extended to 50 degrees. When Flight 439 made the approach which terminated in the accident, the high intensity runway lights were set at step 3, medium bright, and the reported flight visibility was 7 miles. Runway 29 did not have a prepared underrun/overrun area. The ground leading to the threshold slopes upward 2deg 44’, a gradient of approximately 5 percent. Flight 439 made initial ground contact on this incline 156 feet short of the threshold of the runway, rolled forward 73 feet, and became airborne. The aircraft then contacted the runway 262 feet beyond the threshold and continued to roll/skid on the runway before it came to rest 4,457 feet beyond the threshold. Wreckage examination showed that the fuselage had fractured and buckled in the area between fuselage stations 737 and 794. The tail cone rested on the runway. PROBABLE CAUSE: “The National Transportation Safety Board determines that the probable cause of this accident was the pilot’s misjudgment of altitude due to the absence of sufficient lights in the approach area, misleading information produced by deceptive sloping terrain, and that the pilot did not position the aircraft on the ILS glide slope while he was establishing the final approach profile.”

Primary Cause

Pilot’s misjudgment of altitude due to the absence of sufficient lights in the approach area, misleading information produced by deceptive sloping terrain, and that the pilot did not position the aircraft on the ILS glide slope while he was establishing the final approach profile.Pilot’s misjudgment of altitude due to the absence of sufficient lights in the approach area, misleading information produced by deceptive sloping terrain, and that the pilot did not position the aircraft on the ILS glide slope while he was establishing the final approach profile.

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