History of Flight
On November 18, 2016, at about 1117 Pacific standard time, a Cessna 172N, registration N6610D, sustained substantial damage when it impacted terrain during final approach to Half Moon Bay Airport (HAF) in Half Moon Bay, California. The private pilot sustained serious injuries, and the passenger was fatally injured. The personal flight was conducted under 14 Code of Federal Regulations Part 91 in visual meteorological conditions. No flight plan was filed for the flight, which originated from Sacramento Executive Airport (SAC) at about 1015 and was destined for HAF.
The pilot reported checking weather before departure, which indicated winds from the southwest. After departure, he requested visual flight rules flight following to HAF. While approaching HAF, he made position reports on the airport's common traffic advisory frequency and requested traffic information. Another pilot responded that winds were from the southeast up to 15 knots and runway 12 was in use.
The pilot entered the airport traffic pattern for runway 12. On the final leg, the visual approach slope indicator (VASI) lights indicated the airplane was high. At about 800 ft mean sea level (msl) and 65 knots, he reduced power to intercept the VASI glideslope. Continuing with full flaps (30°) at 60 knots and about 500 ft msl, the airplane encountered light turbulence. Concerned about strong buffeting at normal approach speed, the pilot elected to land at a higher airspeed. He retracted the flaps to less than 20° while adding power to stay on the glideslope. Immediately after these adjustments, he felt strong turbulence violently rock the airplane, causing the wings to dip left then right. He felt a strong downdraft, and the airplane entered a steep right bank. Despite applying full power, back pressure, and left aileron and rudder, he could not correct the descent and right bank. He observed runway 12 about 90° to his right but could not reach it due to low altitude. Noticing large trees, he maneuvered to drag the airplane's tail on the ground, then closed his eyes before impact.
Personnel Information
The pilot held a private pilot certificate with ratings for airplane single-engine land and instrument airplane. He reported 1,145 total flight hours, with 884 hours in the accident airplane make and model. In the preceding 90 days, 30 days, and 24 hours, he had flown 16.7, 10.4, and 1 hour respectively. His most recent flight review was on July 21, 2015, in the same make and model. He was issued a third-class FAA medical certificate on April 15, 2015, with the limitation that he must have available glasses for near vision.
Aircraft Information
The airplane was a 1979 Cessna 172N, a single-engine, high-wing, fixed landing gear, four-seat aircraft. It was powered by a 180-horsepower Lycoming O-360-A4M engine, serial number RL-12115-36E, driving a Sensenich metal, 2-bladed, fixed-pitch propeller. Maintenance records showed the last annual inspection was on April 5, 2016, at engine total time 1,068.9 hours and airframe total time 5,768 hours. The airplane and engine had accumulated 173.2 hours since that inspection.
Meteorological Information
At 1115, the HAF weather reporting facility, about ½ nm southeast of the accident site, reported wind from 190° at 10 knots with gusts to 14 knots, visibility 10 statute miles, sky clear, temperature 17°C, dew point 3°C, and altimeter setting 30.03 inches of mercury. A weather study revealed a weak temperature inversion between 400 and 600 ft msl near the accident site. Between 1100 and 1200 PST, the vertical environment changed from unstable to stable. The stable layer trapped updrafts or downdrafts created by wind flowing over terrain to the west and southwest of the airport, creating an environment favorable for low-level wind shear and turbulence below 600 ft msl.
Wreckage and Impact
The airplane descended into a residential area about 1,822 ft northwest of the HAF runway 12 threshold. Initial impact was identified by two parallel rubber tire marks on a street about 245 ft southwest of the main wreckage. The airplane continued northeast across an open field, struck a wooden fence, then the southeast corner of a home's roof, followed by impact with a utility truck. The right wing tip and a landing gear strut were found in the front yard. The wreckage path continued about 60 ft northeast. The nose landing gear was located about 30 ft northeast of the utility truck. The main wreckage came to rest on the southwest corner of a second home, with the lower fuselage flush against the brick structure and the engine firewall upright on the ground. The empennage separated behind the rear passenger seats and folded over the cabin, with the vertical stabilizer and rudder on the ground. The cabin and cockpit were destroyed by impact forces. The left wing remained attached; the right wing separated and impacted a parked white cargo van. The engine, propeller, and one landing gear strut were under the right wing. The left and right main landing gear wheels were found about 42 ft north of the fuselage.
Additional Information
A performance study using radar data showed the airplane approached HAF from the north, entered at 45° to the upwind leg for runway 12, at about 86 knots indicated airspeed (KIAS) and 1,000 ft msl. It slowed to about 80 KIAS and descended to 700 ft msl on downwind. The airplane then made a continuous 180° left turn from downwind to final. At 1116:20, radar showed airspeed about 57 KIAS, altitude 500 ft msl (about 440 ft above ground level), at the apex of a 10°-bank left turn. Pitch changed from about 5° nose up to about -3° nose down, and the airplane accelerated as it descended until impact about 1117:10.
The Pilot Operating Handbook (POH) estimates stall speeds between 31 and 40 knots calibrated airspeed (KCAS), depending on flap position and bank angle. The POH recommends a slightly higher approach speed under turbulent air conditions. The FAA Airplane Flying Handbook recommends adding one-half the reported surface wind gust to the normal final approach airspeed when landing in turbulent conditions. The handbook also advises that retraction of wing flaps during an approach suddenly decreases lift and causes the airplane to sink rapidly.