History of the Flight
The pilot was conducting circuit practice at Shoreham Airport using Runway 20. After four uneventful circuits with touch-and-go landings, while on late downwind during the fifth circuit at approximately 1,100 ft aal, the engine began to cough and lose power. The pilot pumped the throttle, confirmed the magnetos were on, and ensured the mixture was rich. He could not recall whether the carburettor heat was selected on. The engine subsequently lost all power. The pilot made a MAYDAY call and selected a field to the north-east for a forced landing. He set two stages of flap, then full flap as he approached. The aircraft touched down "fairly flat" but nosewheel first, causing the aircraft to bounce and the nose landing gear leg to collapse. The aircraft came to rest on its nose. The pilot exited without injury.
Pilot's Actions
The pilot reported that he had performed the same downwind checks on each of the previous circuits, including verifying the mixture was rich and selecting carburettor heat on for 10 seconds. He noted that he had practised forced landings with an instructor the week before, which helped him enter an "autopilot mode" when selecting a field and setting up the approach. He believed he flared too early due to a downhill slope, leading to the nosewheel-first touchdown.
Aircraft Examination
Examination the day after the accident revealed nearly full fuel. Spark plugs appeared normal, the crankshaft rotated freely with plugs removed, and no oil leaks were observed. Fuel flowed freely from the disconnected carburettor hose. Fuel tank drain checks showed a few droplets of water from the left tank and none from the right. Both magnetos were secure with no evidence of slippage. The carburettor heat valve operated normally, and actuating the throttle caused fuel to eject from the fuel jet. The carburettor was installed on another engine and ran normally. At the time of writing, the engine core had been removed for overhaul. The engine had accumulated over 2,500 hours since its last complete overhaul, exceeding the manufacturer's recommended TBO of 2,400 hours, but was operated under an approved extension programme.
Meteorology
The METAR at Shoreham Airport ten minutes before the accident indicated wind from 250° at 9 kt, visibility over 10 km, few clouds at 1,500 ft and scattered at 1,900 ft, temperature 9°C, dewpoint 6°C, and relative humidity 81%. At circuit height (1,100 ft aal), the temperature would have been about 2°C colder, raising relative humidity to approximately 93%. According to the CAA’s risk of carburettor icing chart, the temperature and dewpoint spread indicated a serious risk of carburettor icing at any power setting.
Pilot Training and Currency
The pilot obtained his Private Pilot’s Licence in 2018 after 54 hours training in a Piper PA-28. His SEP rating expired on 31 August 2020. After flying infrequently, he resumed at Shoreham in November 2022, requiring five flights with an instructor before being cleared to fly solo. The instructor noted issues with checks but signed him off as "ready to fly solo" without specifying aircraft type. The pilot believed he was cleared to fly both the PA-28 and the Cessna 152, while the school thought he was cleared only for the PA-28. Neither the school nor the instructor verified his licence expiration. The pilot subsequently obtained a new SEP rating on 18 January 2023.
Carburettor Heat Usage
The flight manual for the Cessna F152 specifies selecting carburettor heat on during the 'Before Landing' checklist on downwind and leaving it on until landing unless performing a go-around. However, the pilot's instructor taught a technique of selecting carburettor heat on for 10 seconds on downwind to check for ice, then off, then on again before reducing power on base leg, and off on final. This technique deviated from the manual's instructions. The CAA Safety Sense Leaflet recommends selecting carb heat on during downwind checks to remove ice.