Dangers to aviation Part I - Curt Lewis

HIDDEN DANGER:

A Special Report On The Intertropical Convergence Zone

By Roger Rapoport

Editor's Note: This is the first in an exclusive series of Flight Safety Information articles on the growing problem of commercial airline accidents in the intertropical convergence zone.

During the past six years three commercial airline crashes taking the lives of 506 passengers and crew have pinpointed a growing problem challenging outstanding legacy airlines and lesser known carriers alike. Two of these tragedies took place in 2014, five years after the traveling public was alerted to this challenge by the disappearance of a plane in the South Atlantic.

While the companies flying these planes , Air France, Air Algérie and Air Asia operate on vastly different business models, it's clear that in each case special challenges presented by adverse weather in the intertropical convergence zone were misunderstood by inadequately trained flight crews.

Hundreds of thousands of passengers fly through the intertropical convergence zone ITCZ every day. Few realize that the best pilots find special weather conditions here that go well beyond their experience in the classroom and in the air. It doesn't matter whether you are in your first year of flying or have many thousands of hours behind you, chances are your airline training did NOT offer special instruction on the unique challenges that this potentially deadly zone. Even now, in the wake of these three devastating accidents, training at many carriers fails to address this important challenge. 

The ITCZ is a constant presence in the world and as Professor Debbie Schaum of Embry Riddle University explains: "If you haven't taken an aviation weather class from a meteorologist chances are you probably don't understand the dynamics of thunderstorms and heights to which structural icing can impact aircraft in this area of the world." 

On a map the ITCZ looks like a floating equator. Its latitude depends on the season. In the summer the ITCZ is north of the equator and during the winter it moves south with the greatest variations in the western Pacific and Indian Ocean 

Typically the active parts of the ITCZ form over warmer waters where storm activity varies depending on the season. In the summer the ITCZ is very active in the Atlantic north of the equator and during the winter it is a strong force in the Southern Indian Ocean. 

For pilots the significance of this zone can not be overstated. 

For example most Atlantic hurricanes get their head start in the ITCZ off the coast of Africa during late summer and fall. And during the winter all hell breaks loose in the Indian Ocean south of the equator creating cyclones in Australia as well as scary convective storms in Africa where clouds top out at 50,000 feet. 

"The problem," says Schaum, "is that most pilots, dispatchers and air traffic controllers don't understand the dynamics of these weather problems. This is a problem that the best automation and engineering design can't eliminate. Even the newest plane in the sky equipped with the latest onboard weather radar can run into trouble here. One storm in the ITCZ could be a once in a lifetime phenomenon that tests skills of even the most experienced pilots."

Why is there so little aviation training on the impacts of the ITCZ on flight?

"We concentrate a lot over land because of the dynamic forces caused by land," says meteorologist Schaum. "Since the water is smoother, oceans normally get much less attention in training. We gear much of our flight instruction in the U.S. for the northern hemisphere and the mid latitudes where icing caused by thunderstorms doesn't reach the altitudes it can in the ITCZ. 

"Except for the summertime over the Atlantic we don't really deal that much with the ITCZ in the northern hemisphere. In the parts of the world where the problem exists flight crews don't get adequate instruction."

The three ITCZ related accidents in the southern Atlantic, the Java Sea and Africa are well known. But Schaum is quick to point out that "many other flights also encounter these conditions which cause significant icing at high altitudes where they are not normally expected. Because more planes are flying these ITCZ routes this problem is magnified. Until pilots, dispatchers and controllers are trained to recognize the subtleties of these hazards at altitude this dangerous problem will continue."

Next: Air France 447, ITCZ Accident Waiting To Happen