We may never know what really happened aboard missing Indian Air Force aircraft

In all these years that I've been involved with air accident investigations and run an aviation magazine, the one aspect that has always intrigued me — and has even teetered on the brink of bizarre — has been the phenomenon of a crash that occurs at cruising altitude. I use the word "bizarre" advisedly because in the aftermath it is often something out of the ordinary that triggered the tragedy. From missiles to pilots gone nuts to electrical storms and other Hollywood scenarios, it is dramatic and confusing.

And then there is the one which has no conclusion: Like the IAF AN 32. Bad weather? Metal fatigue? Structural failure? All of the above? We might never know.

Contrary to popular opinion, aircraft are not constantly in touch with Air Traffic Control (ATC) or on the radar. Several times a day, scheduled flights lose contact; if they are above large water bodies or over thick jungles. Static can also cause a break in communication.

File photo of AN-32 flight. YouTube

File photo of AN-32 flight. YouTube

Now, and it's a one in a million chance, but if the IAF AN 32 was over water and lost contact for a few minutes when the catastrophic event occurred, they would not have been able to send out a Mayday message or give any clue as to what series of complications were occurring.

Radio Transmission Silence (RTS) is not in itself scary because even if you are not in touch, there are protocols to follow to maintain safety. It's just that airlines do not like to panic passengers though they are flying "blind"; so it isn't a very common subject of discussion. And it isn't really blind because even if they are not in touch, they are being tracked from point to point as per their flight plan. If not through voice, the ATC is updated of each checkpoint by text when the aircraft passes it.

But things change in a crisis.

The AN 32 was probably on radar since the route from Chennai to Port Blair does not pass over a massive body of water like with a trans-Atlantic flight, where you could be out of contact for three hours. But if there was RT failure in an ageing aircraft because a radio transponder malfunctioned and you are flying unassisted in a bad storm or have to vector from your set speed and direction and altitude there could be disorientation.

Into this confusion, if there is structural failure caused either by metal fatigue or by the aircraft exceeding its structural limits, even through wind sheer or turbulence or a pressure failure, what could occur is a mid-air break-up or an aerodynamic stall. They would be unable to communicate their emergency or the reasons leading for it.

What we then get is the statement; the aircraft disappeared off the radar at a specific point. So what happened up there? The tragedy becomes a mystery.

We fall back on research as we wait for the black boxes (Flight data recorder and cockpit voice recorder) to be recovered...in this case from the depths of the sea. Not always possible.

Research shows there have been 77 incidents with the AN 32 since 1986. An aircraft ages not in man years but by the number of items it compresses and decompresses.

This fleet is certainly aged by that measure and the suspicion of a number of incidents on this aircraft including a port door pressure leak and a leak in the port wing root add to the conclusion the plane had a catastrophic failure. If there was a loss of hydraulic pressure, the aircraft would turn into a bucking bronco and out of the ambit of crew control. If it goes into a dive, it will not pull out of it.

In some ways these are the worst of aviation crashes because not only is life lost but no one knows why and sometimes there is no closure. Even if we find the wreckage, recovering the black boxes will be very difficult. We can second guess the combination of bad weather and structural collapse all we like but this flight has probably taken its secret with it forever.

What should be done is to check out the rest of the AN 32 fleet for signs of metal fatigue.

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Updated Date: Jul 24, 2016 15:06:20 IST

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