It was quickly determined that the cause of the divergence was the Styrofoam cockpit enclosure. As the vehicle's sideslip angle reached minus two degrees, a yawing force rapidly built up that exceeded the ability of the yaw thrusters to counteract. The fix decided on was simply to remove the top of the enclosure, thus venting it and eliminating the excessive yawing force. It was also possible from the wind tunnel results to develop a preliminary flight envelope for the LLTV, defining its allowable maximum airspeed at various angles of angle of attack and sideslip. All this had to be verified by flight test, however, since it was not possible in the tunnel to obtain good data with the engine running.