Introduction
On 19 May 2013, a Piper PA-28-140 Cherokee, registration G-ATRR, was destroyed when it struck a tree during an approach to Runway 26 at Caernarfon Airport, Gwynedd. The aircraft was operated by a private pilot on a cross-country flight from Blackpool to Caernarfon. The pilot, aged 61, held a Private Pilot's Licence and had 90 hours total flying experience, with 72 hours on type. Of the three persons on board, the pilot and a five-year-old grandchild sustained serious injuries, while an adult passenger received fatal injuries.
History of the Flight
The pilot had pre-booked the aircraft online several weeks earlier. On the morning of the accident, he arrived with his passengers and found the aircraft parked on the ramp. After checking fuel contents—less than required—he taxied to the pumps, filled each tank to the tab, then returned to the parking area and shut down the engine to board. The front right seat was occupied by the pilot's adult son, and the pilot's grandson sat in the rear left seat. After taxiing, pre-departure checks were completed at the holding area. The aircraft departed Runway 28 and turned left onto a southerly course, following a coastal route at altitudes between 1,000 ft and 2,500 ft amsl.
As the pilot approached Caernarfon, he made several radio calls to RAF Valley but did not establish contact. He then contacted the Caernarfon Airport Air-Ground radio operator, who advised that Runway 26 was in use and the circuit clear. The pilot requested a straight-in approach. The radio operator observed the aircraft on a wide right base-leg, joining final at about 4 nm. The approach appeared normal, and the pilot made a 'finals' call at about 1.5 nm. The operator acknowledged and provided surface wind from 270° at 5 kt.
Witnesses reported the aircraft flying very low and slowly on final approach. It struck a tree and dropped to the ground in a steep nose-down attitude just inside the airfield boundary. The crash alarm was sounded; the airport fire service and subsequently local fire service attended. An air ambulance helicopter already airborne in the area diverted to the airport, providing rapid medical assistance. The adult passenger was fatally injured; the pilot and child were freed and transferred to local hospitals with serious injuries.
Meteorological Information
The day featured a weak pressure pattern across the UK with a light north to north-easterly airflow. Satellite imagery at 1000 hrs showed stratocumulus cloud along the north Wales coast; no precipitation was indicated. Surface observations indicated extensive low-level stratocumulus with bases between 2,500 ft and 3,500 ft. The 0950 hrs METAR from RAF Valley, 16 nm north-west of Caernarfon, reported surface wind 330° at 4 kt, visibility 10 km or greater, few cloud at 1,900 ft, scattered at 2,400 ft, overcast at 3,200 ft, temperature 13°C, dewpoint 8°C. The 0950 hrs METAR from Hawarden, 20 nm south-east of the en-route track, reported surface wind 360° at 2 kt, visibility 10 km or greater, broken cloud at 2,500 ft, temperature 13°C, dewpoint 7°C.
A carburettor icing probability chart indicated that, assuming a reducing temperature and similar dewpoint above the surface, the latter part of the flight operated in the blue sector: 'serious icing at any power'. The CAA Safety Sense Leaflet 14 notes that engines at reduced power settings are more prone to icing, and that partially closed butterflies can be more easily restricted by ice.
Recorded Information
A portable device recovered from the aircraft (an Apple iPad mini running SkyDemon software) provided GPS-derived position, track, altitude, and groundspeed data from 0930 hrs to 1018 hrs. The data showed the aircraft following the coastline to Llandudno, then altering track towards Bangor and Caernarfon. Over the Menai Bridge, it climbed from 1,100 ft; at Caernarfon, about 3 nm from the airport, it was at 1,570 ft and 80 kt groundspeed at 1015 hrs. It then descended towards the final approach track for Runway 26, initially at about 300 ft/min, then at about 960 ft/min (at 2.2 nm from threshold, groundspeed 103 kt). At 1.25 nm and 710 ft aal, the aircraft was on final approach track, with descent rate increasing to about 1,400 ft/min. As it approached 350 ft aal, descent rate reduced; at 0.87 nm, groundspeed was 85 kt and reducing. At about 500 m from the start of the paved runway, the aircraft was at 130 ft aal, groundspeed about 60 kt, descent rate 250 ft/min. With wind from 270° at 5 kt, airspeed would have been near 65 kt. The descent rate then momentarily increased while groundspeed gradually reduced. Shortly after, about 80 m east of the paved surface, the aircraft struck the top of a tree at a groundspeed of about 49 kt (estimated airspeed 54 kt) before impacting the ground.
Airport Information
Caernarfon Airport, elevation 14 ft amsl, has a licensed asphalt Runway 08/26, 935 m long and 23 m wide. There is also an unlicensed Runway 02/20, alongside which are two wind turbines at 140 ft aal. To the east of Runway 26, adjacent to the airfield boundary, lies a leisure park with mobile homes and caravans, extending 300 metres east of the boundary.
Witness Information
Multiple witnesses reported that the aircraft was lower than usual on approach. Some noted a high nose attitude; several commented on a flat flight path and very slow speed. One witness was drawn by an unusual noise, describing the engine as "trying to pick up and popping" and thought the pilot may have pumped the throttle three or four times. Another reported hearing the engine "spluttering and seemed to backfire", while others said the engine was running but at low power.
Investigation
The investigation did not find any evidence of a failure within the engine. However, the atmospheric conditions were conducive to carburettor icing. The pilot reported a loss of power at a late stage of the approach and being unable to reach the airfield.