wet runway accidents
|Building grooved runways and investing in
modern runway friction recording equipment are
essential for making landings safe.
An Indian Airlines Airbus A320 lands in heavy rain at
Chennai airport. — Photo: A. Ranganathan
ON AUGUST 2, 2005, an Air France A-340
overran the runway at Toronto. The aircraft was destroyed in
a post-accident fire. Exactly a month earlier, a Bangladesh
Biman DC-10, overran the runway at Chittagong. The aircraft
suffered extensive damage. An Air India 747, which overran
the runway at Mumbai on July 30, 2005, was lucky to escape
with no damage except to reputations. Even before the
enquiry got under way, several armchair pundits blamed the
pilots. Are they aware of what is involved in a wet runway
All the accidents mentioned took place
while landing in heavy rain. All the planes involved
experienced crosswind (where the surface wind blows from the
side) and tailwind conditions. This combination is
dangerous. During a heavy downpour the water depth can vary
along the runway, depending on the condition and the slope.
The aircraft wheels can hydroplane if the depth is
sufficient to prevent them from making proper contact with
the runway. This makes it very difficult to stop the
aircraft within the confines of the runway.
Why do accidents happen on wet runways?
The main reason is that the pilots do not get the correct
information on the actual runway condition. The only
information a pilot gets is that the runway is "wet."
What is a wet runway? For the pilot, the
runway is considered "wet" when the depth of water on it is
less than 3 mm. This is what the flight manuals state. If
the depth is more than 3 mm, the runway comes in the
category of "slippery" or "contaminated." These differences
in water depths will change the actual landing distance by a
very large amount.
The aircraft requires 40 per cent more
runway to stop on a "wet" runway; on a contaminated runway
the figure increases by 300 per cent. Thus, if an aircraft
requires 6,000 feet of runway for a landing on dry runways,
it would require 8,400 feet on a wet runway, and more than
18,000 feet of runway if the conditions are contaminated!
Thus, when a pilot receives a report that
says the runway is wet, he assumes that the depth of water
is less than 3 mm and that a 40 per cent addition to the
landing distance will make for a safe landing. In reality,
the actual depth of water on the runway can be as much as 3
inches during a heavy monsoon downpour. This would bring it
into the "contaminated" category. In 30 years of airline
flying, I have never heard of a runway condition report
other than "wet."
Accidents on wet runways are on the
increase. Experience levels of pilots in the airlines are
dropping due to the rapid expansion of the aviation sector.
Unfortunately, training and regulations are not keeping up
with the times. There seems to be an unnecessary emphasis on
testing pilots for manoeuvres that are next to impossible on
modern jets such as 737NGs and the A-320s. This prevents
airlines from using the available training time on
simulators for carrying out exercises demanded by accident
enquiry recommendations. Many of the accidents in the recent
past have involved aircraft with old technology, without
modern safety features that are inbuilt into new generations
Studies by the Directorate-General of
Civil Aviation (DGCA) have established that more than 45 per
cent of all landing accidents take place during the monsoon
or in heavy rain.
The DGCA constituted the Approach and
Landing Accident Reduction task force in 2000, after the
introduction of the topic by the Flight Safety Foundation of
the U.S. I was a member of the Core Group of the ALAR India
task Force. The objective of the ALAR project was to reduce
landing accidents by 50 per cent in five years. Officials of
the Airports Authority of India were members of the task
force. In spite of being aware of the accident statistics,
nothing significant has been done to improve the runway
conditions nor has there been any effort to make the airport
environment safer. Not a single runway in India is grooved.
During the deluge in Mumbai last month,
the airfield was completely contaminated with slush and
debris. The secondary runway was opened for operation
without even carrying out proper runway friction tests.
Runway 14 has a down slope towards the second half, and this
makes it positively dangerous during heavy rain.
Building grooved runways, investing in
modern runway friction recording equipment, and proactive
runway condition reporting are essential for making landings
safe. What is required is commitment to flight safety.
(Capt. Ranganathan, an
airline pilot with 19,000 hours experience, specialises in
accident prevention studies.)