New Delhi, May 26
Bad weather appears to be the cause of air ambulance crash in Faridabad yesterday that claimed 12 lives. This was indicated by Directorate General of Civil Aviation’s preliminary investigations, reports emerging from the aircraft’s operator and aviation experts.

It was on a particularly windy evening that the single-engine PC-12 aircraft hired by Delhi’s Apollo Hospital crashed into a densely-populated residential colony on the approach path of the Delhi airport, just about 15 minutes before its scheduled landing.

High-velocity winds may have caused some technical malfunction in the light-bodied aircraft, leading to its crash, said sources.

The crash has resulted in the government creating an independent panel to probe major aviation accidents. The move has separated the role of a regulator and an investigator which was being performed by the DGCA alone so far.

“The commander of the ill-fated aircraft reported to the Air Traffic Control that he was facing bad weather,” the Civil Aviation Ministry said.Aviation expert AN Hanfee terms the mishap as “one-off incident in which weather played an important part”. Hanfee says several aircraft coming to land at the Delhi airport around that time had experienced the weather trouble. “Many bigger aircraft reported similar situation, finding it difficult to land around that time. PC-12 (Pilatus) was fatally affected because of its smaller size,” he said.

Elaborating on prevailing conditions, he says the plains of North India are experiencing turbulence at higher altitudes because of a sustained high temperature hovering around 45 degree C at the ground. High temperatures heat the surface of the earth and subsequently the air above. When the air gets heated at different temperatures, gust and turbulence are created. They have the capability of destabalising even a huge aircraft like Boeing-777. “We know a case wherein a Boeing-747 lost 25,000 feet, dropping from the height of 40,000 feet to 15,000 feet after encountering an air pocket,” he says.

The PC-12 is a small aircraft in the 4740-kg category. In comparison, an Airbus-321 weighs around 82,500 kg, while the Boeing-777 is a mega 1,50,000- kg aircraft.

Besides the limitation of small size, the ill-fated aircraft was flying at such a low level that the pilots had no altitude to recover after encountering bad weather. Facing the storm, the commander of the aircraft sought permission to land, which was granted by the ATC, sources say.

Since PC-12 is a small aircraft, rules applicable to bigger aircraft do not relate to it. The aircraft does not either have the flight data recorder (DFDR) or the cockpit voice recorder (CVR). It just has small weather radar and a storm-scope, which gives the position of any static change in the atmosphere.

The problem with winds is that there’s no radar to make them visible, clouds and dust. “In such conditions, it is pure past experience that works,” says an experienced pilot.

This Air India pilot, who did not wish to be named, says that even though the two pilots of the aircraft did not have thousands of hours of flying experience, the crash was possibly neither due to pilot-error or any technical failure. “While flying, we follow the rule: fly-navigate-communicate. Had there been a technical failure, the pilot would have reported it to the tower, which he never did,” he said.

However, he does say that rules regarding small aircraft should be made more stringent. “At least an FDR should be fitted so that in case of the crash one knows what happened. Cockpit experience should be of a certain minimum level and in my opinion single engine aircraft should always fly under VFR (Visual Flight Rules)and during day. Even they are flying IFR (Instrument Flight Rules), they should only fly during daytime so that they know what is happening around them. Single-engine aircraft should not be allowed to fly in unpredictable weather,” he says, advising periodic checks of experience of the crew and maintenance of the aircraft.

The DGCA has formed a working group to review existing safety regulatory framework of general aviation, non-scheduled operators and air ambulance operations. It is also checking the maintenance record of the ill-fated aircraft. Meanwhile, the aircraft operator, Air Chartered Services India Private Ltd said the aircraft was in good condition “We have been flying the air ambulance service for the Delhi Apollo Hospital for the past six years,” an official said.