LAX94LA137
LAX94LA137

On February 24, 1994, about 0915 hours Pacific standard time, a Waco YMF-5, N50YM, nosed over during landing on runway 24 at the McClellan-Palomar Airport, Carlsbad, California. The pilot was conducting a visual flight rules (VFR) local area flight. The airplane, operated by Air Mikie International, Oceanside, California, sustained substantial damage. The certificated airline transport pilot, the sole occupant, received minor injuries. Visual meteorological conditions prevailed. The flight originated at McClellan-Palomar Airport at 0858 hours.

The pilot indicated in his accident report that he was conducting a maintenance test flight. A mechanic had just completed an annual inspection on the airplane.

Initially, the pilot did a ground static run-up with the parking brake set. After the ground run-up, he shut down the engine and inspected the airplane for fluid leaks. Everything checked normal. He then boarded the airplane, started the engine, and requested a taxi clearance from the ground controller.

After receiving the taxi clearance, the pilot applied power, but the airplane would not move. He then noticed that he had not released the parking brake. He said, in part:

"...I depressed the brake pedals to remove the parking brake. It did not work. I then tried pushing in the T-handle which sets the parking brake. This did not release it either. I called the mechanic over and told him the parking brake was not releasing. Finally, I tried pushing in the handle and depressing the brake pedals, simultaneously. The handle then clicked off into [the] normal position. [The] brake pressure was relieved on the pedals and the plane [airplane] felt free to move forward...."

During the taxi to the runway, the pilot applied the brakes and they operated normally. The pilot departed the airport without incident and flew to the practice area. The airplane functioned normally during the climb, level off, and routine maneuvers. The pilot then returned to the airport.

The pilot said that the landing conditions were excellent with clear skies and the winds were calm. He executed a "soft wheels landing." As the airplane transitioned to the tail low position, the airplane yawed to the left and its nose violently pitched down. The pilot was unable to control the airplane with the appropriate flight controls application.

A Federal Aviation Administration (FAA) airworthiness inspector conducted the on-scene examination. The inspector said that the pilot told him the facts, conditions, and circumstances as related in the accident report. The mechanic told him that the pilot had released the brakes by the time he arrived at the airplane during the initial parking brake problem.

The mechanic told the FAA inspector that he accomplished the annual inspection by using a checklist provided in the maintenance manual. He said that he inspected the parking brake system for operation, overall condition, and security as required by the checklist. With the lower fuselage panels removed, the mechanic observed normal operation of the parking brake valve with the brakes on and off.

The FAA inspector found the parking brake control valve midway between the full on and full off position. The brakes were locked. An unidentified person released the brakes from the cockpit. The FAA inspector and mechanic observed that the control arm on the valve rotated toward the off position, but did not go to the full off position; the brakes, however, released. The FAA inspector observed that the parking brake control cable was bent near the area where it attaches to the valve actuating arm. After the mechanic disconnected the cable from the valve, the valve rotated freely to both extremes.

The FAA inspector examined the airplane's maintenance records and found no evidence that the parking brake system had been previously worked on. The mechanic told the inspector that the maintenance manual contained no procedures for rigging the parking brake system.

The FAA inspector also found several pages missing from the airplane flight and maintenance manuals. The manufacturer's general manager provided the FAA inspector with copies of the missing pages. The maintenance manual procedures for releasing the parking brake differ from the airplane flight manual. The maintenance manual does not refer to applying brake pedal pressure before pushing in the brake T-handle. The airplane flight manual provides a "CAUTION" note with respect to releasing the parking brake. The note states:

DO NOT PUSH PARKING BRAKE CONTROL "T" HANDLE OFF BEFORE APPLYING BRAKE PRESSURE - DOING SO CAN BEND THE CABLE RESULTING IN THE CONTROL VALVE NOT BEING TURNED ALL THE WAY OFF. SUBSEQUENT BRAKE OPERATION MAY RESULT IN UNWANTED PARKING BRAKE APPLICATION.

This caution is not a required instrument panel placard. The required placard only notes setting of the parking brake control.

The owner transported the airplane to the manufacturer's facility in Lansing, Michigan. The FAA inspector tagged the airplane to prevent any repairs on the airplane until examined by an FAA manufacturing inspector, from the Detroit, Michigan, Manufacturing Inspection Satellite Office (MISO).

The FAA manufacturing inspector examined the airplane and found no discrepancies. He noted that the bent cable was actually designed with a small bend where the wire passed through the clevis. He said the parking brake functioned the same as a factory new airplane.

The FAA manufacturing inspector reported that the company revised the Airplane Flight Manual on December 12, 1993. The revision places an increased emphasis on the parking brake operation. The accident airplane did not have the newer flight manual revision. He also said that of the 57 airplanes built by the manufacturer, 11 of them were involved in similar accidents.

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