JACKSON FLORES / RIO DE JANEIRO & DAVID LEARMOUNT / LONDON
Airline cites windshear as likely cause of F28 loss on approach to Chachapoyas
Controlled flight into terrain (CFIT) or windshear have emerged as two possible factors in the crash of a Transportes Aereos Nacionales (TANS) Fokker F28 during approach to Chachapoyas, north-east Peru on 9 January. Local pilots familiar with the area believe the F28 may have turned toward a cloud-covered mountain when the crew believed it had passed it. The airline, however, believes windshear was to blame.
A search helicopter discovered the wreckage 46h after it was reported missing (Flight International, 14-20 January). There were no survivors among the 47 people on board.
The wreckage was discovered on a mountainside 28km (15nm) north west of Chachapoyas Airport. The only navigational aid at the airfield is a VOR, and aircraft arrivals are made visually through the type of terrain known bylocal aviators as a "nailbed" to carry out a circling approach. The Peruvian investigators say that the TANS crew, arriving from the west, were familiar with Chachapoyas and were expecting to land on runway 13.
Airfield elevation is 8,300ft (2,520m) and the F28's wreckage was found at the 10,200ft level on the slopes of the 11,430ft Cerro Boloje. The weather at the time was good visibility with no precipitation, but Cerro Boloje would have been overcast.
TANS suggests windshear was a likely cause because in that sector of the Andes mountains winds with a vertical component can be powerful. The airline believes that the aircraft was in a descending right turn when it was hit by a down draught. Investigators estimate that the aircraft hit the mountain at an angle at an airspeed of 160-200kt (300-370km/h). Local aviators who know the approach say that the normal procedure approaching from the west is to pass Cerro Boloje and then turn right to acquire the airfield visually.
The cockpit voice and flight data recorders have both been recovered and sent to the USA for analysis.
Meanwhile, the Turkish government has confirmed that the THY Turkish Airlines BAE Systems Avro RJ100 which crashed at Diyarbakir on 8 January was on its planned approach path but had descended well below its minimum descent height, 639ft above the airfield's 2,180ft elevation.
The impact point was slightly below the airfield level (Flight International, 14-20 January). There were only five survivors among the 80 people on board. The crew was carrying out a VOR/distance measuring equipment approach but had not, the authorities confirm, requested any radar assistance.
Source: Flight International
