On July 21, 2007, approximately 1600 Pacific daylight time, a Boeing Stearman A-75, N56551, nosed over during the landing roll at Felts Field, Spokane, Washington. The private pilot and his passenger were not injured, but the airplane, which is owned and operated by the pilot, sustained substantial damage. The 14 CFR Part 91 personal pleasure flight originated at the same airport about 10 minutes prior to the accident. The flight was being conducted in visual meteorological conditions. There was no report of an ELT activation. According to the pilot, soon after touching down on the main gear, the left brake locked up, and the airplane began to veer toward the edge of the runway. During his attempts to keep the airplane rolling straight, both bottom wings came in contact with the runway surface, and before he could get it stopped, it flipped over onto its back. According to the FAA Inspector who responded to the scene, the airplane's left tire had created a significant skid mark starting at a point just past where the airplane touched down. There was no evidence of skidding of the right main gear tire. The FAA inspector's post-accident inspection of the airplane did not reveal any clear reason for the malfunction of the left brake. In a telephone conversation with the NTSB Investigator-In-Charge (IIC), the inspector said that it was his opinion that the brake mechanism had malfunctioned/locked either while the airplane was in the air, or during the touchdown sequence. During a telephone conversation, the pilot gave the NTSB IIC a detailed description of the accident sequence, but he failed to submit an NTSB Form 6120.1/2.