Incident Overview

Date: Friday 25 April 1969
Aircraft Type: Lockheed EC-121R Super Constellation
Owner/operator: United States Air Force – USAF
Registration Number: 67-21493
Location: 6 km W of Nakhon Ratchasima Royal Thai Air Force Bas – ÿ Thailand
Phase of Flight: En route
Status: Destroyed, written off
Casualties: Fatalities: 18 / Occupants: 18
Component Affected: Aircraft Structure (specifically wings, propellers, and engine components).Aircraft Structure (specifically wings, propellers, and engine components).
Category: Accident
An EC-121R, 67-21493, conducted a combat tactical mission from Korat, Thailand, at 15:20 with a scheduled takeoff and contact with departure control. The flight initially established communication and requested information regarding a thunderstorm cell near the base. After takeoff, the aircraft was vectored around the thunderstorms and requested a right turn. Following takeoff, the crew was instructed to maintain runway heading and radar vectoring. Prior to takeoff, the pilot was advised to turn right to two eight zero degrees. The flight experienced turbulent conditions, including a significant shift in wind direction, and subsequently impacted with ground gear, engine power, and ultimately, crashing into a rice paddy. The impact caused significant damage to the aircraft’s structure, resulting in a large debris field. The aircraft’s trajectory was altered, leading to a rightward veer and subsequent impact with a tree stump, culminating in a crash 300 yards from the touchdown point.An EC-121R, 67-21493, conducted a combat tactical mission from Korat, Thailand, at 15:20 with a scheduled takeoff and contact with departure control. The flight initially established communication and requested information regarding a thunderstorm cell near the base. After takeoff, the aircraft was vectored around the thunderstorms and requested a right turn. Following takeoff, the crew was instructed to maintain runway heading and radar vectoring. Prior to takeoff, the pilot was advised to turn right to two eight zero degrees. The flight experienced turbulent conditions, including a significant shift in wind direction, and subsequently impacted with ground gear, engine power, and ultimately, crashing into a rice paddy. The impact caused significant damage to the aircraft’s structure, resulting in a large debris field. The aircraft’s trajectory was altered, leading to a rightward veer and subsequent impact with a tree stump, culminating in a crash 300 yards from the touchdown point.

Description

An EC-121R, 67-21493, callsign “BATCAT 21” from the 554th Recon Sq, was scheduled for a combat tactical mission out of Korat, Thailand. BATCAT 21 started engines approximately 15:20 and commenced taxi to run-up position at 15:30. After completing engine run-up, the flight was cleared for takeoff by Korat Tower at 15:54 and was advised to contact departure control. BATCAT 21 established contact with departure control and requested information on the position, direction of movement and speed of the thunderstorm cell near the base. Departure control advised BATCAT 21 that the thunderstorm was over the base and extended 20 miles southwest. BATCAT 21 requested a right turn after takeoff and radar vectoring around the thunderstorms. The controller requested the crew to maintain runway heading and indicated that he would vector the aircraft around the thunderstorms. Prior to becoming airborne, BATCAT 21 was advised that he was cleared to turn right to two eight zero degrees. The flight reported airborne at 15:58 and departure control advised the heading was two eight zero degrees and he would radar identify BATCAT 21. This was acknowledged and a short time later the crew requested to make a right turn if possible as it was very turbulent. Korat departure control approved the request. No further transmissions were received from BATCAT 21. The aircraft impacted with the ground gear up, engine power METO. The initial point of impact was in a rice paddy at a ground speed of 221 knots. Indicated airspeed was approximately 150-160 knots. As the aircraft traversed the rice paddies the under part of the wings and the propellers began to disintegrate. A dike separating the rice paddies, 80 yards from impact, started the disintegration of the accessory section of the engines. The right wing then struck a tree stump causing the path of the aircraft to veer slightly right. It continued on this path an additional 30 yards, struck another stump and returned to its original path across the ground, striking a tree with the number 2 engine and exploding 255 yards from impact. The fuselage continued down the rolling hill separating the two rice paddy areas and flipped to the right (the right side of the cockpit being the pivot point), finally coming to rest 300 yards from the touchdown point. At approximately two and one half miles after lift-off and about 500 feet altitude, the aircraft entered a down draft which also was an area of strong wind shear. The aircraft experienced turbulence, but more significantly, the relative wind swiftly changed from a 20 knot head wind to at least a 20 knot tail wind. As the aircraft descended it entered the region closest to the ground where the tail wind was the strongest. Witness reports and wind damage estimates indicate the there was a most likely 60 knot tail wind at the surface when the aircraft crashed.

Primary Cause

Turbulent flight conditions, specifically the rapid shift in wind direction and the subsequent impact with terrain, likely exacerbated the aircraft’s instability and contributed to the crash.Turbulent flight conditions, specifically the rapid shift in wind direction and the subsequent impact with terrain, likely exacerbated the aircraft’s instability and contributed to the crash.

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