What happened
Upon arriving in the vicinity of Bridgeport Airport, the pilot-in-command received ATIS information indicating a visibility of 1/2 mile in snow and fog. The ILS Runway 06 approach was active, and braking action advisable reports were in effect due to thin wet snow covering all surfaces. During the approach, with the second-in-command at the controls, the pilot-in-command verified that the hydraulic pressure gauge was normal and performed a brake test.
The tower controller informed the crew that a Navajo had recently landed and reported good braking action, with a 250-foot ceiling and 3/4 mile visibility. As the Hawker Siddeley HS-125 descended through the overcast, the aircraft broke out of the clouds approximately 400 feet above the ground. The runway appeared dry, though blowing snow was present.
The aircraft touched down approximately 1,463 feet beyond the approach end of the 4,677-foot runway. The second-in-command reported a lack of braking effectiveness and deployed the flaps to assist in slowing the aircraft. As the airplane failed to decelerate sufficiently, the crew approached the 1,000-foot marker, at which point the second-in-command applied the emergency brakes and subsequently the parking brake. Despite these efforts, the airplane continued off the end of the runway, struck a non-frangible fence, and came to rest with approximately 4 feet of the aircraft protruding onto a public access road. There were no injuries.
The investigation
Post-accident examination of the aircraft's airspeed indicator showed a reference speed set at 117 knots. According to the airplane flight manual, the uncorrected landing distance on a dry runway for this estimated weight was approximately 2,610 feet; however, calculations using the manual's chart for slippery runways determined the equivalent scheduled landing distance available was only about 2,150 feet.
Airport records confirmed a NOTAM had been issued the day of the accident stating that all surfaces had thin wet snow. An air traffic controller observed slush spraying from the aircraft during its rollout. A subsequent test of the aircraft's braking system revealed no mechanical abnormalities.