Monday, December 29, 2014

AirAsia 8501

AirAsia 8501, an Airbus A320 aircraft with 162 souls on board disappeared Sunday morning over the Java Sea while enroute from the Indonesian city of Surabaya to Singapore in heavy weather. As of yet there has been no wreckage found nor any signals from the aircraft's emergency locator beacon. The last transmission from the aircraft was a request for a left course deviation and a climb from 32,000 feet to 38,000 feet with weather avoidance given as the reason.

The climb request was denied by air traffic control due to traffic conflicts. There were heavy thunderstorms in the area which are normally associated with the tropical weather in the region. Radar contact was lost with the aircraft several minutes after the denied request.

While it is too early and not enough is known about the fate of the aircraft, a few clarifications about flight near thunderstorms may be helpful.

Don't Mess with Mother Nature

Thunderstorms are dangerous things and can grow to heights above which all commercial planes are unable to climb. Flight through a thunderstorm is also extremely hazardous as the gusts, rain, and turbulence inside can easily bring down any aircraft flying today, including fighters. You simply do not penetrate a thunderstorm.

It may then seem unconscionable that air traffic control (ATC) denied the climb request. What must be remembered though is that the function of air traffic control is not weather avoidance but rather traffic separation. Weather avoidance is the primary duty of the pilot. Most ATC radars are not even equipped to show weather data.

Should a situation arise where a turn away from a large cell needs to be made immediately and ATC denies the request, pilots always retain what is called emergency authority to keep their aircraft free of hazards. In such a case, turning the aircraft away from a storm is always the safest course and should be done while advising ATC of your actions.

The best course of action is to plan your weather avoidance actions as early as possible. Airborne radar has a useable range out to several hundred miles to search for holes in the weather. Should there be no apparent safe passage through the weather, a turnback or diversion to another airport is always possible. As I said earlier, you don't fool around with thunderstorms.

Springtime and summer are the worst seasons for thunderstorms in North America and at times I've seen solid lines of storms stretching from Texas to the Great Lakes. Flying around these storms can take you hundreds of miles off course, even into Mexico or Canada to avoid them.

Stay Out of the Shadows

One of the shortfalls of airborne radar is that it can't see "through" especially thick storms to let you know what is on the other side. The danger is flying towards what you believe is a "hole" in a line of weather only to find a larger cell behind the first one that wasn't apparent. The area behind a thick cell might look clear but isn't. For this reason, pilots are warned to never fly into or towards a radar "shadow" or area behind a strong return.

Modern digital radars now display warning icons on the screen when a shadow is apparent but in the recent past the antenna had to be pointed at the ground to discern shadows. If there were no "ground returns" or reflections from the ground behind the cell, you knew it was a shadow.

Life Inside a Storm

Ok, so what happens if you really screw up and end up inside a thunderstorm? Nothing good. For starters, the ride is going to be really rough. The severe turbulence found inside a thunderstorm means that everything that is not locked, bolted or strapped down is going to fly. This includes carts, lap children and most likely all the luggage in the overhead bins as the doors will pop open. So there will be injuries and chaos.

The structure of the aircraft may also be in peril. A simple rudder reversal on an Airbus taking off from JFK back in 2001 caused the whole vertical stabilizer (tail) to break off. Forces inside a thunderstorm will be stronger and may cause engines to depart the wing and wings to depart the aircraft. Never good.

But let's assume the engines and wings stay on the aircraft. The next danger is the huge amount of rain that the engines will swallow. Jet engines have a fire burning in the hot section and if enough water gets poured into the engine, the fire will be put out. We call this a flameout. And like trying to restart a campfire in the rain, it won't easily relight.

So now you're a glider in severe turbulence looking for a place to land in heavy rain and wind with limited instruments. This situation is generally one pilots wish to avoid so we are well incentivized to stay out of thunderstorms.

So What Happened?

Getting back to the fate of AirAsia 8501, the Java Sea where the aircraft was last seen on radar is nowhere as large an area as the Indian Ocean where the Malaysian 777 disappeared. Also, the aircraft was in radar contact which really narrows the potential search area.

So while weather may have played a part in the disappearance, it is just too early to know.

As it happens, I've flown on AirAsia. I put my family on an AirAsia flight from Bangkok to Phuket on a vacation a few years back. I found the airline to be modern, professional and a delightful experience.

While our prayers go out to the families who have loved ones on the aircraft, we hope to know more in the near future.

1 comment:

  1. Anonymous6:13 PM

    I think this is my favorite blog! I mostly read it at work where I can't comment. But I am finally getting around to a comment from home. SO MUCH good info here about things none of us passengers can even imagine. Thanks,(Capt) Rob! Keep it coming.


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