the failure of both pilots to maintain an adequate visual lookout, resulting in both airplanes colliding in flight. Contributing to the accident were: 1) inadequate approach/departure control service by ATC approach/departure personnel, and the failure of the radar approach controller to advise the local tower controller of the change in approach procedure for N51ML; 2) the excessive and extraneous radio communications by the local controller which prevented both pilots from providing timely position information during the critical period prior to the midair collision.