Last message: 'We are climbing 550...'
CHENNAI: "Victor Tango Alpha Pappa Golf calling Chennai radio. We are from Hyderabad heading for Chittoor. Departed Begumpet at. We are climbing
550 (5,500 ft). Expected time of arrival at Chittoor."
"Roger."
That was the last radio communication between the pilot of the fateful helicopter carrying Andhra Pradesh chief minister Y S Rajashekhar Reddy and the Flight Information Region (FIR) in Chennai. That was around 9.10 am. After a few minutes, the pilot radioed the Hyderabad control that he would be in contact with Chennai, following which Hyderabad handed over the control to the Chennai FIR.
"We haven't heard anything from the chopper after that," an air traffic official privy to the last communication told TOI, explaining the fire-fighting that followed. According to protocol, if no communication is received from an aircraft 30 minutes after its control is handed over to an FIR, the centre goes about plotting three phases: Uncertainty phase, alert phase and distress phase, each at an interval of 30 minutes.
Hearing nothing from the chopper, which was to communicate using a high frequency radio (HF), Chennai FIR kept switching between two HF radios, 6655 KHz and 8909 KHz. "Chennai radio calling Victor Tango Alpha Pappa Golf. Are you reading?" No reply. FIR then tuned into the very high frequency (VHF) band of 123.4 MHz, usually used for communication between pilots.
"We wanted to see if the pilot lost our frequency and was trying some other pilot. When there was still no reply, we tried the universal emergency frequency 121.5 MHz, to which any pilot in an emergency situation is expected to tune in. That too drew a blank," the source said.
FIR then initiated the 'uncertainty phase' and sent out signals to all air traffir control stations and airports in the vicinity such as Tirupati, Mangalore, Visakhapatnam, Bangalore and Hyderabad about the missing chopper.
The 'alert phase' started around 10.40 am and all the stations were called up to inquire about any signals they received. The air traffir management and Airports Authority of India top brass were then informed before going into the 'distress phase'. Subsequently, the regional coordination centre attached to the FIR took over the case.
