Pilot error was the likely cause for the chopper crash that led to Chief of Defence Staff General Bipin Rawat's death last month, sources said Wednesday afternoon. Sources said the Mi-17V5 helicopter carrying Gen Rawat, his wife Madhulika, and 11 other armed forces personnel - from the Sulur Air Force base in Tamil Nadu's Coimbatore to the Defence Staff Services Colleges in Wellington - crashed after a CFIT, or Controlled Flight Into Terrain, occurrence.