On October 20, 2003, at 1618 mountain standard time, a Piper PA-28-235, N9338W, collided with the ground while attempting to return to the Falcon Field Airport, Mesa, Arizona. The airplane was being operated by the owner/pilot under the provisions of 14 CFR Part 91. The private pilot and passenger both sustained serious injuries. The airplane was substantially damaged. The personal local flight was originating at the time. Visual meteorological conditions prevailed, and no flight plan had been filed. The flight departed from runway 22R. During the initial climb, the pilot reported a loose panel and tried to return to the airport. The airplane collided with terrain about 250 yards southwest of runway 4L. A witness reported that the airplane departed with an open cowling. After lifting from the runway, the airplane turned left and then stalled. The witness lost visual contact with the airplane when it descended below a tree line. Post accident examination of the airplane by the National Transportation Safety Board investigator-in-charge (IIC) revealed that the attachment fittings for the cowling on the right side were unlatched and not damaged. The left attachment fittings for the cowling were latched and deformed. The IIC made repeated requests for the pilot to complete NTSB Form 6120.1/2 but no reply was received.