Adopted: July 1, 1942
File No. 3451–41
REPORT OF THE CIVIL AERONAUTICS BOARD
of the
Investigation of an Accident Involving Aircraft in
Scheduled Air Carrier Operation
A Lockheed model 18-08, NC 25639, was extensively damaged in an accident which occurred about noon, August 1, 1941, at the Municipal Airport, Colorado Springs, Colorado. It was owned and operated by Continental Airlines, Incorporated. The crew consisted of Captain Marshall B. Woodworth, Jr., and Co-pilot Charles H. Collins, Jr., both of whom were properly certificated and appropriately rated. There were two non-revenue and five revenue passengers aboard the aircraft. No injuries were received by any of the occupants.
The flight, designated by the carrier as No. 7 of August 1, 1941, originated at Wichita, Kansas. Its destination was Denver, Colorado, and intermediate stops were scheduled at Hutchinson, Kansas, Garden City, Kansas, Pueblo, Colorado, and Colorado Springs, Colorado. The flight proceeded without incident and reached the vicinity of Colorado Springs on schedule. Weather conditions were favorable and Co-pilot Collins made the approach and the landing. Prior to the landing, the routine cockpit check indicated that the landing gear was down and the hydraulic system was functioning properly. The landing, made with the tail wheel locked and flaps extended, was normal until the aircraft had rolled about 300 feet. Then, when the speed of the aircraft had decreased to about 15 m.p.h., the left landing gear retracted. The left wing settled to the ground and the aircraft came to rest after turning about 180 degrees in a left groundloop.
After the accident the aircraft was raised and the landing gear, the visual signal system, and the hydraulic system were checked. It was found that all operated normally with the exception of the four-way selector valve of the hydraulic system and the left safety latch, on which the plunger was bent. A detailed examination revealed that the four-way selector valve had developed an internal leak, which apparently caused a reduction in hydraulic pressure at the time of the landing. The reduced pressure in the system together with the simultaneous sticking of the left safety latch was apparently responsible for the retraction of the left side of the landing gear.
There is no reason to believe that the crew had operated the landing gear retracting lever during the roll of the airplane on the ground. This is substantiated by the fact that had the lever been operated, both sides of the landing gear would have collapsed simultaneously instead of the left side only.
PROBABLE CAUSE: Malfunctioning of the landing gear hydraulic system.
BY THE BOARD
/s/ Darwin Charles Brown
Secretary
