The FAA also will require new maintenance
procedures and crew training for the passenger jet, the Boeing 737.
The 737 is the most widely used commercial
jet in the world. There are more than 1,200 of them in the United
States and more than 3,500 of them worldwide. According to Boeing,
a 737 takes off or lands somewhere in the world every 5.5 seconds,
and approximately 1,000 of them are in the air at any given time.
The design changes to the rudder system of
the 737 come after a lengthy study by a 22-member team of independent
experts from government and industry. The panel was commissioned to
look into problems with the rudder after two high-profile crashes
were attributed to malfunctions with the system’s controls.
Although the new design has yet to be finalized,
the FAA and Boeing say it will create the reliability and redundancy
needed to deal with certain rare failures, requiring independent,
backup rudder controls.
After two fatal crashes in the early 1990s
attributed to previously unsuspected rudder failures, National Transportation
Safety Board investigators determined the current system did not provide
adequate backup.
Jets now in service will continue to fly,
but once the new rudder design is ready to implement — probably in
2003 — the airlines will have to install it in all versions of the
737, new and existing. The retrofitting of existing 737s will be complex
and costly, and could take five years, finishing in 2008, says the
FAA.
Other Changes, Too
In addition, the FAA announced today that the airline industry,
by March of 2001, would have to implement changes in how they maintain
and operate 737s, and how they train flight crews to deal with sudden,
unintended deflections of the rudder, which are extremely rare occurrences.
The FAA found that the current emergency
procedures to deal with a jammed rudder were so confusing that when
they tested them in a flight simulator with 10 different crews,
all of them failed.
Although rare, the jammed rudder condition
can be fatal if not correctly identified, and was not known to be
a problem prior to two crashes, both involving 737s. The NTSB identified
the condition, in which the rudder deflects completely to the opposite
side of that commanded by the pilot, after exhaustive investigation
into the crash of USAir Flight 427 in Pittsburgh, in 1994, which
killed all132 people aboard. It was then also attributed as the
cause of an earlier crash of a United Airlines 737 near Colorado
Springs, Colo. in 1991, which killed all 25 people aboard.
The rudder is the vertical portion of the
tail which enables the nose of the plane to move left and right.
737s Are Safe
At a press conference today announcing the changes, the FAA went
to great lengths to stress that the current fleet of 737s is extremely
safe, repeating the point at several intervals.
“Today’s 737 is an incredibly safe airplane,
period,” said John Hickey, manager of the FAA’s Transport Airplane
Directorate in Seattle. “Data shows it is the safest airplane that
we’ve ever approved.”
He pointed out that the FAA previously
ordered three major modifications to the 737 rudder system, all
of which have already been implemented.
“All U.S.-registered 737s have all those
changes in place. Since then, we have had no verified report of
any 737 rudder anomalies,” said Hickey.
“The reason we’re taking this additional
step is that the 737 is the most popular plane flying,” Hickey said.
“It’s going to keep going on and on, there’s another 30 to 40 years
of life to it, so to get to the ultimate state of safety we felt
that the rudder redesign was the right thing to do.”
The single-aisle, twin-engine jet began
service in 1968, and is now in its ninth generation, or version,
of production.
In a statement, Boeing also stressed the
safety of the existing design of the 737. “These enhancements should
be taken in context,” said Carolyn Corvi, vice president and general
manager of the 737 program. “The 737 family has been, and continues
to be, among the safest of all jetliners. … But we believe even
this airplane can be enhanced. So we are simplifying flight crew
procedures, increasing maintenance oversight, and modifying the
rudder control system.”
Investigators at the NTSB were heartened
by the announcement, pointing out that they had recommended the
design change to the 737 rudder a year and a half ago. They say
the earlier changes to the rudder system mandated by the FAA, while
helpful, did not address their concern over the failures they had
found to be responsible for the two accidents.
“This is a good first step,” NTSB spokeswoman
Lauren Pedruzzi said of the pending design changes.
Even though the FAA has no jurisdiction
over non-U.S. airlines, most top foreign airlines are likely to
follow the agency’s lead in this kind of safety matter, especially
if they fly into the United States. The FAA can ground planes of
a foreign airline once they are in the United States if the agency
deems them to be unsafe.
Two
Tragic Accidents
The two fatal accidents have been attributed to a severe malfunction
of the 737’s rudder. Both were mysterious events that occupied years
of investigators’ efforts before yielding answers.
In 1991, a United Airlines 737 was approaching
the airport at Colorado Springs, Colo., when it suddenly pitched
sharply to the right and down, and crashed in an almost vertical
dive into the ground, killing all 25 people aboard.
NTSB investigators initially suspected
a strong mountain wind known as a “rotor” as well as a rudder malfunction.
But eventually, they attributed the crash
to a sudden, unintended deflection of the rudder completely over
to the opposite side that the pilot intended.
In 1994, a USAir 737 was approaching Pittsburgh’s
airport when it encountered turbulence from a plane landing just
ahead of it. As the pilots tried to counter the effects of the turbulence
using the rudder, the plane banked sharply to the left, rolled upside
down, and eventually crashed nose-first. All 132 people aboard were
killed.
The NTSB blamed a jammed rudder for the
accident.
As a result of these two crashes, and another
rudder incident where the pilots recovered the plane, the NTSB issued
22 recommendations relating to the 737’s rudder system, starting
in 1996. The most sweeping of these was presented in 1998, in the
final report into the crash of USAir flight 427, calling for a complete
redesign to the rudder to provide what it called a “reliably
redundant system
|
HOME
PRINT THIS PAGE
