The first run on the rocket sled took place on 30 April 1947 with ballast. The sled ran off the tracks. The first human run took place the following December. Instrumentation on all the early runs was in the developmental stage, and it was not until August 1948 that it was adequate to begin recording. By August 1948, sixteen human runs had completed, all in the backward-facing position. Forward-facing runs started in August 1949. Most of the earlier tests ran to compare the standard Air Force harnesses with a series of modified harnesses. This was to determine which type gave the best protection to the pilot.