It was late in the night around 0030 hours on June 9, 2015. I woke up to a call on my door and found my Principal Director (Ops) at my doorstep to break the news of an overdue aircraft CG 791, which had gone for MR sortie from Chennai at 1805 hours on June 8 with an endurance of 0620 hours, and was expected to return to base at 2200 hours.
We Immediately rushed to the Ops Room at Coast Guard Headquarters and learnt that the aircraft had earlier contacted Chennai Flight Information Centre (FIC) at 2100 hours and reported about its departure from the area to return to base i.e., Chennai as scheduled at 2200 hrs. There being nil communication with the aircraft, the Flight Information Centre (FIC) Chennai declared the aircraft overdue at 2230 hours.
Incidentally, no ‘MAYDAY’ call had been received from the aircraft. Besides, the Emergency Locator Transmitter (ELT) and Personal Locater Beacon (PLB) transmission signals had also not been received. On enquiry, ATC Trichy reported tracking of the aircraft till 2123 hours in position 32 nm northeast of Karaikal Light on the Tamil Nadu coast. It was also ascertained from the INMARSAT Service Provider that the SATCOM of the Dornier CG -791 had suddenly powered off at 2124 hours.
The aircraft CG 791, a latest induction into the CG Dornier fleet in February 2014 from Hindustan Aeronautics Ltd, was manned by a very experienced crew namely Dy Comdt Vidya Sagar, Dy Comdt Subash Suresh and Dy Comdt M K Soni, having more than 2000 hours of flying experience. In fact, since inception in 1986, the Dornier fleet in the service had an excellent safety track record besides having clocked more than two lakh flying hours.
Although it was a dark night, with <g data-gr-id="251">moon rise</g> at 2312 <g data-gr-id="250">hourrs</g>, the weather in the area was partly cloudy with wind speeds of 15-20 knots, sea state two-three and did not pose any particular challenge.
On receipt of the information regarding aircraft overdue, a prompt and massive search and rescue effort in area 45 NM around the last known position (datum) of aircraft was launched by the Coast Guard Region (East), Chennai for locating the missing CG Dornier, under code name ‘Operation Talash’. The Regional Commander was himself in the Coast Guard Ops Room at Chennai coordinating the search operation. A CG Dornier was immediately pressed into search operation at night and four Coast Guard/Naval ships at sea were diverted for augmenting the search efforts.
However, as time passed by through the night, our worst fear of aircraft ditching into sea deepened.
By <g data-gr-id="253">day break</g>, four more CG/IN ships were also sailed from Karaikal and Chennai. One CG AOPV with Helo embarked was also sailed from Chennai. Naval long range maritime reconnaissance Aircraft P8i was tasked for search in <g data-gr-id="292">area</g>. CG Interceptor Crafts ex Puducherry were also deployed for close coast search. The Coastal Security Group of Tamil Nadu State Police, State Fisheries and SIB Chennai were sensitised regarding the missing CG Dornier and requested to keep a sharp look out. Despite intense air-sea coordinated search, no aircraft debris/survivor could be sighted. Subsequently, the search area was extended to 70 nautical miles.
Leaving no stone unturned to accomplish the mission, the ICG approached the Indian National
Centre for Ocean Information Services (INCOIS), Hyderabad with a request to run its SAR model programme for the missing aircraft and to identify the Most Probable Area (MPA). The software prediction was corroborated with the search area planned by ICG. <g data-gr-id="296">Assistance</g> of the National Remote Sensing Agency (NRSA) was also sought for analysis of the Satellite imagery of the area for possible location of the aircraft as also debris.
When survivors/debris were not found despite massive search over two days, based on <g data-gr-id="301">Internet</g> search of earlier air crashes over <g data-gr-id="302">sea</g>, it was presumed that the aircraft would have settled on the sea-bed. The subsequent search was, therefore, directed towards locating the missing aircraft on the <g data-gr-id="255">sea bed</g>. The assumption that the aircraft probably had nose-dived into sea was further corroborated by the last radar tracking of CG 791 received from Flight Information Centre (FIC) Chennai on June 11, which indicated that the aircraft had suffered very rapid loss of altitude prior to loss of contact.
On the basis of the powering-off of the INMARSAT, the loss of contact by the Trichy Radar Control, and inputs received from Chennai ATC radar, the datum was re-appreciated as 11.3 nautical miles NNE of the initial datum. Likely ditching of aircraft in and around revised datum was further substantiated by sighting of a <g data-gr-id="252">multi-coloured</g> sheen of oil in concentric circles 05 nautical miles away from revised datum, indicative of oozing of fuel from aircraft.
Not to ignore any lead whatsoever in furtherance of the search, an input by a Cuddalore fisherman regarding sighting of fireball at about 2315 hours on June 8 while fishing in area was thoroughly <g data-gr-id="276">investigated,</g> and ruled out as the timing of sighting of <g data-gr-id="256">fire ball</g> was not matching with that of the missing of aircraft contact from Trichy Radar at 2123 hours. Further, no debris of missing aircraft was sighted in the area substantiating the claim.
Having searched the most probable area over land and at sea, Indian Navy was requested for the services of a Survey Vessel and Submarine to locate the Sonar Locator Beacon (SLB) of the missing aircraft. Further, NIOT was also requested to deploy their Research Vessel Sagar Nidhi.
Accordingly, INS Sandhayak was deployed for underwater search on June 12. The major challenge in the conduct of the sub-sea search was the steep gradient of seabed in the search area and thermocline. Though the Survey Vessel did <g data-gr-id="254">pickup</g> sub-surface transmission on 37.5 KHz frequency, in position 1.5 NM South southwest of Revised Datum June 12, suspected to be from the Sonar Locator Beacon (SLB) of the missing aircraft, a firm position could not be localised as no subsequent transmissions were received.
The Naval Operations Data Processing and Analysis Centre (NODPAC), Kochi, which collates oceanographic data from various sources with an aim to provide inputs to submarines for optimal underwater search, offered valuable advice on bathymetry, depth and seabed profile of search area, ideal search parameters including direction of approach/sensor placement and potential hindrances to accurate location of aircraft, such as multiple intercepts due to bottom scatter.
On June 13, IN submarine Sindhudhwaj arrived and commenced Search in area of 15x15 Sq NM. The submarine reported sporadic sub-surface reception in Band-2 i.e. between 8-40 KHz but the signal being weak, no position could be established. Subsequently, an NIOT team equipped with Black Box Detector embarked onboard Coast Guard Ship Vigraha commenced search in area but did not detect any signal. Thereafter, the Naval Submarine continued search in the area until arrival of NIOT Research Vessel Sagar Nidhi, which was pulled out from an ongoing research mission.
R V Sagar Nidhi arrived on June 15 and commenced seabed profiling around the Revised Datum spanning 10x10 Sq NM. However, no aircraft debris was located. After the NIOT vessel vacated the area, INS Sindhudwaj once again resumed search in the area but to no avail. We, thereafter, requested the services of Multi Support Vessel (MSV) Olympic Canyon of Reliance Industries for undertaking Sub-surface search utilising its onboard Remotely Operated Underwater Vessel (ROV).
Despite being bound by Production Sharing Contract, in Joint Venture with two other partners, in an utmost noble humanitarian gesture, RIL readily agreed to provide the vessel, free of cost. Here, I would like to place on record our sincere gratitude to PMS Prasad, Executive Director and Prem Kumar Verma, President Production of RIL Mumbai and DIG (Retd) DB Prasad, Vice President, RIL Kakinada for their timely support in lending the services of MSV Olympic Canyon.
MSV Olympic Canyon arrived on June 19, and commenced sub-surface search utilising underwater camera fitted on ROV over six likely positions identified by Coast Guard, each spanning 500x500 mtr. The vessel picked up underwater transmission on 37.5 kHz in eight positions in vicinity of Revised datum from its Hull-mounted, High Precision Acoustic Positioning Equipment (HIPAP). An extensive search was carried out by MSV using ROVs in 2.0 x 1.3 NM block indicated by the intercepts. When no positive results were achieved the MSV departed area for contractual commitments June 23. Subsequently, Sindhudwaj resumed search on June 25, yet no tangible pickups were reported.
As surface search by CG and Naval ships and aircraft continued in the area, submarine Sindhudwaj was once again deployed for the third time on July 5. This time around, the Submarine picked up a heavy barrage of Band-2 (8-40 kHz) transmission in two positions. One was 3 NM South of Revised Position and the other was 5 NM northeast of Revised Position. The pick-ups were inconclusive and the submarine departed area on July 6.
While an unprecedented massive search effort was in progress, managing the emotionally charged family members of the ill-fated crew was indeed an equally unprecedented challenge. Considering that the best way to tackle such uncertainty is to keep the family members abreast of the ongoing search efforts, they were provided with regular updates and even detailed presentations and personal briefings at the Ops room at Chennai, besides moral and logistic support. Regular press briefs / press briefing were also issued by the Regional Headquarters at Chennai to keep the media posted on the developments at every stage.
The DGICG also visited Chennai for a first-hand update and to meet the family members of the aircraft crew. A Board of Inquiry was ordered to investigate into the circumstances leading to the disappearance of CG 791.
When nearly a month into the incident, the search was not yielding any tangible results, the desperate family members of crew attempted to seek solace in predictions from astrologers. In order to fulfil the wishes of family members based on such predictions, search over was carried out over land along Tamil Nadu coast and also in Andaman & Nicobar waters. Assistance was even sought from the Sri Lankan authorities for search in their jurisdiction.
At one stage, when we were unable to localise underwater acoustic transmission (ping), we scouted for any advanced technology available elsewhere in the world. Consultation with professional surveyors and salvers indicated that all possible measures and technologies available for locating the aircraft at such depths were already being exploited by us. Smit International, Singapore indicated that the maximum depth at which they had so far undertaken salvage operations was only 610 metres, whereas the depth in the probable search area was around 1,000 meters.
In order to refine our search efforts and obtain expert opinion, we also held consultations with several international agencies viz., Japan Coast Guard (JCG), Korean Coast Guard (KCG), Australian Maritime Safety Agency (AMSA) and Transportation Safety Board (TSB), Canada.
Meanwhile, Reliance accepted Coast Guard’s request to redeploy its MSV Olympic Canyon. The MSV arrived area on July 10 and once again commenced sub-surface search using ROVs & HIPAP.
Fortunately, within a few hours, the refined sub-surface search yielded results and MSV Olympic Canyon located the debris of CG 791 around position 03 NM South of the Revised Position on July 10. The vessel successfully recovered the Flight Data Recorder (FDR) and Cockpit Voice Recorder (CVR) along with other parts of the disintegrated aircraft from a depth of 922 mtrs. Subsequently, few human remains (bones) were also recovered. Finally, Operation ‘Talash’ for the search of the missing CG Dornier 791 was terminated on July 14. It was no consolation to the families, but at least now there was a much needed closure to the case. The CVR and FDR have been sent to ECIL, Hyderabad and OEM, USA respectively for retrieving the data.
Besides the countless man hours and working nights by all those engaged in the planning and execution of SAR efforts, the relentless and most intense SAR operation for CG 791 involving 5243:05 hours of surface search by ships, 258:15 hours of air search and 719:41 hours of sub-surface search, spanning over 33 days, is possibly the first in the maritime history of India.
The author is Deputy Director General (Operations & Coastal Security) at Coast Guard Headquarters, New Delhi