06 March 2000 12:23
Copyright © 2000 The Seattle Times Company
Local News : Tuesday, February 22, 2000
told FAA in secret of 737 rudder hazard before 1994 crash
by Byron Acohido
Seattle Times staff reporter
for years that pilots had no way to overcome dangerous rudder
problems that could occur while flying 737 jets at low speeds,
but waited until after two planes crashed to acknowledge the
problem, newly released court documents indicate.
The documents, which include letters from Boeing to the Federal
Aviation Administration, were filed in a lawsuit against Boeing
and its rudder-parts supplier, Parker Hannifin Corp., by the
families of two people who died in the 1994 crash of a US Airways
737 near Pittsburgh.
The suit, filed in Chicago, was settled late last year, with
Boeing agreeing to pay $25.5 million to the two victims' families.
The Seattle Times then asked Cook County Circuit Court Judge
Judith Cohen to release records that might otherwise be sealed
in the wake of the settlement. This week, Cohen ordered most
of the court papers released.
The documents establish the companies' long-standing awareness
of the rudder's propensity to deflect on its own. What's more,
the papers show Boeing discovered in the early 1980s that there
was little pilots could do to recover from some rogue deflections,
yet failed to point out the significance of that finding to
safety regulators and airlines.
Boeing insists it did nothing wrong, and
everything it was required to by federal safety regulations.
Records from the court file indicate:
Boeing's original 1963 patent for the valve that controls the
737's rudder, along with other documents, describe potentially
catastrophic consequences from the valve jamming and causing
the rudder to deflect on its own.
While certifying the 737-300 for commercial service in 1984,
Boeing conducted flight tests that showed at low speeds - below
what's called a "crossover speed" - there was nothing
a pilot could do to neutralize a jammed rudder.
Boeing waited until 1992 - the year after a defective rudder
flipped a United Airlines 737-200 slowing to land in Colorado
Springs - to discuss the safety implications of the crossover-speed
hazard with the FAA. Twenty-five people died in the Colorado
In discussing the hazard with the FAA, Boeing insisted that
the agency keep the information to itself, saying it was a trade
secret. The FAA complied.
Two years later came the Pittsburgh crash. The US Airways 737-300
was slowing to land when a rudder deflection twisted it into
a precipitous dive, killing all 132 onboard.
It wasn't until late 1995 - after the National Transportation
Safety Board (NTSB) inadvertently learned about the crossover-speed
danger - that 737 pilots began flying faster during takeoffs
and landings to minimize the hazard.
Those disclosures helped the families of two Pittsburgh crash
victims, Thomas Kinsey and Denise Jenkins, win the settlements
from Boeing and Parker Hannifin.
On the eve of the opening of a jury trial in November, the
companies agreed to pay Kinsey's wife, Ramona, $14 million and
Jenkins' husband, Christopher, $11.5 million.
But Ramona Kinsey remains bitter. Boeing officials, she says,
"blame everything that goes wrong on somebody else. They
don't care who they hurt or what they say or what they do. They'll
do anything to get off their responsibility."
After The Times requested the court records, Boeing took the
unusual step of compiling a 16-page, point-by-point rebuttal
of issues raised by Kinsey's Chicago-based attorney, Donald
Nolan. The company gave the rebuttal to reporters this week.
In it, Boeing says it has never misrepresented anything about
the 737's design and never suppressed any safety information.
The company accuses plaintiffs' attorneys of making "inaccurate
arguments" in court proceedings.
Mike Denton, director of project strategy and development at
Boeing, said in an interview this week that federal regulations
do not specifically require manufacturers to account for a crossover-speed
hazard. Additionally, Denton said, the FAA itself participated
in the 1984 flight tests during which the crossover speed was
"We discussed it openly . . . this is the way the airplane
behaves, so noted, but in my perception it was not seen as an
issue," Denton said. "I think we were open and honest
in our dealings with the FAA and the airlines."
However, court records show that data from those tests made
no references to any safety risk. Regulators and airlines now
consider the phenomenon a hazard.
Nolan, Kinsey's attorney, said Boeing more than doubled its
settlement offer once the company's knowledge of the crossover-speed
hazard emerged as a central issue in the lawsuit.
"Up until the day before the trial, they said they would
never pay more than $5 million, but that night they paid $14
million," Nolan said. "That settlement speaks far
louder than any press release about what a good product they
have. We had damaging evidence against them and they did not
want to have a finding by a jury in the United States that
the 737 is defective."
Rudder still a safety concern
The 737, the world's most widely used model with more than 3,100
jets in service, is statistically very safe. Older model 737-100s
and -200s have crashed 1.06 times for every million flights,
while newer model 737-300s, -400s and -500s boast a crash rate
of just 0.41 per million. That compares to a rate of 1.83 crashes
per million flights for all commercial jets.
But the rudder remains a safety concern for the NTSB. Last
March, the board ruled that rudder jams had caused the 737 crashes
in Colorado Springs and Pittsburgh, without specifically identifying
what went wrong with the valve. The board also has blamed rudder
jams for the near crash of an Eastwind Airlines 737 in Richmond,
Va., in June 1996 and the emergency landing of a Metrojet 737
in Baltimore last February.
Boeing, while formally accepting the
NTSB's rulings, continues to blame the Colorado Springs
crash on a freak weather occurrence and the Pittsburgh crash
on pilot error. And the company maintains its examinations of
the rudder valves from the Eastwind and Metrojet 737s turned
up no evidence of jamming.
"Even today, this is a valve that's very, very reliable,
that hasn't seen any jams," Denton said.
The 737 is the only large commercial jet with a rudder controlled
by a single hydraulic valve. All other jetliners have multiple
valves backing up each other.
The rudder is the hinged panel on the upright tail section,
controlling the aircraft's left-to-right direction of travel.
The valve works by directing pressurized hydraulic fluid to
deflect the rudder. If the valve jams, it can direct fluid to
the wrong place at the wrong time, causing unwanted deflections.
When the FAA certified the single-valve rudder for the original
737-100 in 1967, Boeing assured the agency the valve would never
jam. Yet pilots soon began reporting rudder malfunctions disrupting
737 flights. The reports, now numbering in the hundreds, have
continued until today.
The FAA initially saw no great danger because Boeing had assured
the agency that even if the rudder valve did jam, pilots could
easily counter a rogue deflection by deploying wing panels called
It would take until last April for lawsuits to unearth company
records indicating Boeing, in fact, saw the crossover speed
as a potential hazard in 1984 while testing the new 737-300
for certification, even though the company at the time did not
specifically point out the hazard to the FAA.
It wasn't until investigators began asking pointed questions
about the Colorado Springs crash that the crossover speed emerged
as a safety concern.
In a Sept.
14, 1992, letter to the FAA, Boeing advised the agency that
the 737's comparatively small ailerons lacked the leverage to
neutralize a rudder deflection once the aircraft slowed below
the crossover speed.
In that letter,
Kenneth Usui, Boeing airworthiness manager, advised Donald Riggin,
manager of the FAA's aircraft-certification branch in Renton,
that Boeing considered information about the crossover speed
"proprietary" and was providing it "on a confidential
does not authorize the FAA to retain any portion of these materials,"
Usui wrote. "They should be returned to Boeing immediately
following use by the FAA, including any copies thereof which
the FAA may make in the course of its review."
decline to say how the agency responded. Boeing now says the
wording of Usui's letter acknowledging that the crossover-speed
hazard was standard practice, a routine means to keep sensitive
information from competitors.
"Certainly we thought we were open and honest about it,
but we weren't advertising it as a big deal," Denton said
of the 1992 letter. "It gets back to the FAA regulations.
There isn't a specific requirement that says this cannot occur.
It wasn't perceived as an issue, even in 1984 when we demonstrated
A month after the Usui letter, on October 8, 1992, officials
from Boeing and Parker Hannifin in Irvine, Calif., met in Seattle
to discuss what to do about new information that the 737 rudder
was capable of jamming in such a way that the rudder would move
in the opposite direction of a pilot's command.
The officials reviewed a cost-benefit analysis chart posing
four choices. The chart stated that the company could "do
nothing" and replace suspect rudder valves "only at
customer request." While costing Boeing nothing, that option
would result in "high safety concern" and possibly
raise questions about whether the 737 was properly certified
as safe to fly.
Alternately, the chart said, Boeing could "minimize safety
concern" by calling for installation of improved rudder
valves on all 737s in two to three years. Such action could
mean grounding some jets and result in "undue customer
Two other options were set forth in the chart: Boeing could
make rudder-valve improvements across the 737 fleet in either
four years or seven years, with corresponding costs and safety
The company chose seven years. According to the cost-benefit
chart, such a move would "reduce safety concern" while
avoiding the costly prospect of having to ground some jets until
improvements could be made.
Boeing's Denton said the do-nothing option wasn't seriously
considered. The choice of making improvements to the valve within
two to three years was rejected because Parker Hannifin couldn't
produce parts quickly enough and because airplanes might have
to be grounded at remote airports, he said.
"We came up with a plan that would allow them (airlines)
to do these fixes in a way that works best with their maintenance
operations," Denton said, noting that Boeing also asked
airlines to inspect the rudder every three to four months. "If
you allow them to do the work with people who normally do that
work, that's the safest way."
Simulator was more forgiving
On Sept. 8, 1994, a fully loaded US Airways 737-300 took off
from Chicago with an unimproved rudder valve. About an hour
later, while slowing for a routine landing approach into Pittsburgh,
the aircraft suddenly swerved left and dove 6,000 feet into
As part of the crash investigation, Boeing invited NTSB representatives
and officials from US Airways and the FAA to Seattle in late
1994 to fly a 737 flight simulator.
Each person who flew the simulator was able to easily recover
from a sudden rudder deflection simply by turning the control
wheel to deploy the ailerons and letting the jet's nose drop
to gain speed.
Boeing's interpretation: The US Airways pilots must have mistakenly
steered the jet into the ravine. Perhaps the pilots panicked
when the aircraft was jostled by the turbulence - known as wake
vortex - swirling from the wingtips of a Delta 727 flying four
miles ahead, Boeing theorized.
What NTSB investigators didn't know was
that Boeing's simulator had been programmed so that the ailerons
could neutralize a rudder deflection at speeds much lower than
the US Airways jet had been flying. The crossover-speed threshold
was much more forgiving.
NTSB investigators didn't completely buy Boeing's theory of
pilot error, but they were stymied by a lack of physical evidence
pinpointing a rudder malfunction. So the safety board agreed
to conduct $1 million worth of wake-vortex flight testing.
Boeing lobbied to hold the tests in Seattle with Boeing pilots
in charge, but the NTSB insisted the tests be conducted at the
FAA's flight center in New Jersey. The tests proved what many
experts thought all along: Wake-vortex encounters are inconsequential
for big jets.
But the experiment did yield a surprise for the NTSB: The 737's
ailerons actually had negligible ability to counter a sudden
rudder deflection when flying at or below the speed the US Airways
jet had been flying.
Within a few weeks of that revelation, US Airways ordered its
737 pilots to speed up during landing approaches and takeoffs.
The airline wanted the pilots to maintain the ability to counter
a rogue rudder deflection as long as possible.
Other airlines soon ordered their 737
pilots to take off and land at higher speeds.
In the summer of 1997, Boeing conducted new flight tests that
gave the company a "better understanding" of how quickly
the airplane would twist into a dive given an acute rudder deflection
at low speeds, Denton said. The flight-simulator program was
updated the following year based on fresh calculations from
those tests, he said.
In a sworn deposition taken last April for the Chicago lawsuit,
US Airways chief pilot James Gibbs testified that Boeing had
insisted until late 1995 that there was no crossover-speed danger
associated with the 737. Gibbs testified that awareness of the
crossover speed was "absolutely" critical to flying
"Not knowing about the phenomenon would put the crew in
a position where they had an uncontrollable aircraft, and they
wouldn't know why," Gibbs testified.
"It is much more important for a pilot to be able to promptly
apply the correct recovery techniques to an upset, no matter
what the cause, than to try and ascertain whether an airplane
is above or below some imprecise crossover speed."
Flying slightly faster on takeoffs and landing "is not
a panacea," Denton said, adding that pilots need to understand
how an airplane behaves and be proficient at unusual recovery
techniques. With Boeing's help, many airlines began instituting
such training after the Pittsburgh crash.
Nolan, the plaintiff attorney, contends putting the onus on
pilots to recover from a rogue rudder deflection violates a
federal law requiring commercial aircraft to be designed so
that it does not require extraordinary pilot skills to deal
with a flight-control malfunction.
Meanwhile, the NTSB says the 737 rudder remains dangerous and
that several improvements Boeing has made do not eliminate the
possibility of potentially catastrophic valve jams. Boeing and
the FAA are studying an NTSB recommendation, issued last March,
calling for the 737 rudder to be redesigned so that it is no
longer controlled by a single valve.
"Good design removes the defect," Nolan said. "It
doesn't put people in emergency situations and say, 'If the
pilots react perfectly, everything will be OK.' "