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- August 19, 2002
- The Five Rudder Movements - A Pilot's
Reaction to Wake Turbulence?
- The Rudder Movements Timeline and What
- by Victor Trombettas (with Arthur Doucette)
- On November 20th, the following comments came from the NTSB's
first web-based Update on the Flight 587 Investigation:
- The FDR (Flight Data Recorder) indicates that flight 587
encountered two wake vortices generated by JAL flight 47. The
second wake encounter occurs about 8 seconds before the end of
the FDR data. For the first few seconds after the second wake
encounter, the aircraft responded to flight control inputs. Both
wake encounters averaged about 0.1 G lateral (side to side) movement.
During the last 8 seconds of FDR data, the plane experienced
three stronger lateral movements, two to the right of 0.3 and
0.4 Gs, and then one to the left of 0.3 Gs. These lateral forces
corresponded in time with rudder movements. The NTSB continues
to investigate the cause of the rudder movements. The FDR's rudder
data becomes unreliable about 2.5 seconds before the end of the
- We get some pretty specific numbers here--"The second
wake encounter occurs about 8 seconds before the end of
the FDR data", "The FDR's rudder data becomes unreliable
about 2.5 seconds before the end of the recording."
Note that the NTSB was able to pinpoint the "rudder data
becomes unreliable" point down to the half second.
That indicates a fair degree of certainty. This 8 second sequence
quickly grabbed the attention of the investigators when Tom Haueter,
the NTSB's Deputy Director of Aviation Safety, stated in November,
""Obviously, the whole time we're talking about
is the last eight seconds ... We have eight seconds we're going
to be looking at in extreme detail."
- It becomes very clear that the NTSB believed (and we assume,
continues to believe, since they have not updated, or commented
on, this data since November):
- a. the second wake encounter occurred 8 seconds before the
FDR stopped recording.
- b. Only 2.5 seconds before the FDR stopped recording, the
rudder position data in the FDR became "unreliable".
- Therefore, we only have 5.5 seconds of reliable rudder data
during those last 8 seconds of FDR recording. This is important.
Let's look at this in simpler terms. We have a 5.5 second period
which begins with a one-tenth g-force lateral movement, a.k.a.,
the 2nd wake encounter. The NTSB has never revealed what effect
this wake encounter had on the plane. Did it create a sideslip
or yaw? A roll? No clues. After this wake vortex has hit the
plane we must allow some time for the pilot to mentally process
that encounter and to decide to use the rudder. All of this,
from the wake encounter, to a pilot's decision to react, and
then to the five rudder swings, must occur in a 5.5 second period.
We'll come back to this 5.5 second period later.
- On Feb. 8th 2002, the NTSB
issued a Safety Recommendation in which they warned against
"sequential full opposite rudder inputs". In layman's
terms--"don't swing the rudder from side to side--you might
break the tail".
- Please note this text from that Safety Recommendation:
- "During (emphasis mine) and shortly
after the second (wake) encounter, the flight data recorder (FDR)
on the accident aircraft recorded several large rudder movements
(and corresponding pedal movements) to full or nearly full available
rudder deflection in one direction followed by full or nearly
full available rudder deflection in the opposite direction."
- "During the second wake encounter".
In other words, "As the second wake encounter
occurred ... the rudder was already moving.
- That requires an incredibly quick response time from
the Pilot. It is difficult to imagine this because pilots:
- a. never react with rudder as their first response to wake
- b. Usually have their feet on the floor; not on the rudder
- c. might employ ailerons before they use rudder
- d. usually let the plane fly through most turbulence and
return itself to normal attitude without trying to "control"
the plane back.
- The NTSB's Feb. 8th Safety Recommendation implies that Flight
587 hit the second wake vortex, and as it hit, during
the encounter, the Pilot exercised zero patience and decided,
contrary to his training, to abandon restraint and went straight
for the rudder. We are not given any attitude information on
587. What happened to 587 that caused the Pilot to react with
the rudder? We assume Flight 587 was in normal climb attitude
just before the second wake vortex hit. Flight 587 had encountered
the first alleged wake vortex 20 seconds earlier (the first 0.1g
lateral movement), but that was an insignificant encounter because
Marion Blakey stated last November that the "attitude of
the plane was unchanged" after that encounter. What made
the 2nd alleged wake encounter so unique as to solicit almost
superhuman response times from the First Officer? There was nothing
unique about that 2nd wake vortex as it was, in most likelihood,
at least 8 football fields
away and much higher and never reached Flight 587. If there
was no 2nd wake encounter, why did the rudder start moving at
all?? There have been leaks to the press over the last several
weeks that Investigators are becoming increasingly convinced
the First Officer was responsible for the rudder movements. If
that is true, he was using the rudder for the same reason he
had called for max power a second earlier ... because they were
in recovery mode even before the 2nd alleged wake encounter.
The crew had declared loss of control when only 2 of the 5 rudder
movements had completed, when they were still 4.5 seconds from
the "rudder data unreliable" point, the point the NTSB
believes the rudder and/or tail broke free. Since the crew felt
it necessary to institute a recovery procedure before the alleged
2nd wake encounter ... the simple question arises ... why? What
put the crew into a situation where they were worried about the
safety of the plane if, according to the NTSB, the plane's attitude
is fine and they haven't yet hit the 2nd wake vortex? The two
periods of airframe rattles (the second period of rattles precede
the 2nd wake encounter by 5 seconds), have to loom as very large
leads in this case. The condition of the rudder also looms as
a large lead--why was it ripped
apart so badly and discovered in the Bay at least 600 feet
from the vertical stabilizer in multiple pieces? Why did so many
people see explosive flashes, raging fires, heavy smoke, before
the tail came off? It appears that many people are content in
assigning the rattles to wake turbulence.
- More interesting information from the NTSB's Safety Recommendation:
- "within about 7 seconds, the rudder traveled
11° right for 0.5 second, 10.5° left for 0.3 second,
between 11° and 10.5° right for about 2 seconds, 10°
left for about 1 second, and, finally, 9.5° right before
the data became unreliable."
- Earlier I showed how the NTSB had identified a 5.5 second
period which began with the 2nd 0.1g lateral acceleration, was
followed by rudder movements (we discovered in the February Safety
Recommendation that it was five rudder movements), and
ended with the rudder data in the FDR becoming unreliable. But
in February, the NTSB stated, "within about 7 seconds,
the rudder ..." made it's five movements. Seven seconds?
We only have 5.5 seconds with which to work with. Not seven.
How does a 5.5 second period, which had a fixed start
and end point (the second 0.1g lateral movement as the start
point and the loss of "reliable rudder data" as the
end point), become an almost 7 second period? The data released
by the NTSB on February 8th points to only one answer ... the
rudder was moving before the alleged 2nd wake encounter.
The implications of this are significant. The NTSB has not stated
this as a matter of fact. What they stated in November was that
the rudder moved after the wake encounter. In February,
they said the rudder moved during the wake encounter.
The data, however, indicates the rudder was moving before
the wake encounter.
- Based on information from the Feb. 8th Safety Recommendation,
and an estimate of the maximum maneuverability speed of the rudder
at 39 degrees per second, it appears the rudder started the first
of the five rudder movements and ended the fifth one in a total
6.21 seconds (this calculation is consistent with the NTSB's
stating the rudder moved five times "within ... 7 seconds").
- The Rudder Movements Timeline
- I'm also including in the rudder timeline any other data
available to us including FAA ATC (Air Traffic Control) tape
- At 9:15:58 AM, the First Officer calls for "max power"
approximately a quarter second before the rudder movements begin.
This, as a standalone item, is significant. Why do we have the
pilot instituting an "escape" maneuver when the 2nd
wake encounter hasn't hit yet?
- 1st rudder movement starts at 9:15:58.29 AM (about
a quarter second after the "max power" call), moves
11 degrees to the right (from neutral) in .28 seconds, and arrives
at 11 degrees right at 9:15:58.57 and stays there for .50 seconds
- The alleged 2nd wake encounter occurs at 9:15:59. In other
words, the first rudder movement begins .71 seconds before the
2nd wake encounter, and is already at 11 degrees right at the
time of the 2nd 0.1g lateral acceleration. Any chance this lateral
acceleration was caused by, or corresponded to, this first rudder
- Also, at 9:15:59, there is the first of several interference-riddled
and garbled transmissions on both the Local Control and Departure
Control Air Traffic Frequencies.
- 2nd rudder movement starts at 9:15:59.07, moves 21.5
degrees to the left (from right) in .55 seconds, and arrives
at 10.5 degrees left at 9:15:59.62 and stays there for .30 seconds
- As the 3rd rudder movement is about to start, the "losing
control" comments begin on the CVR (Cockpit Voice Recorder)
and the losing-control-sequence noises also have begun on the
FAA tapes even though the tail does not separate from the plane,
according to official sources, until 4.5 seconds later.
- Also, the transponder sends an erroneous altitude figure
at 9:16:00 of 3,019 feet to the JFK radar. According to Ted Lopatkiewicz
of the NTSB, the plane is at approximately 2400 feet.
- Something vicious is already at play here with the pilots
already having gone to max power, the rudder moving wildly (either
in recovery mode by the Pilot or system induced or both), the
transponder is malfunctioning, and the radios are sending poor
quality, interference-riddled transmissions, yet the FDR is still
recording reliable rudder data.
- 3rd rudder movement starts at 9:15:59.92, moves 21.25
degrees to the right (from left) in .54 seconds, and arrives
at 10.75 degrees right at 9:16:00.47 and stays there for 2.00
seconds until 9:16:02.47.
- The garbled phrase, "Losing Control" is discerned
on the Departure Control tape at 9:16:02. The word "Control"
is clearly discernible. Loss of control is being declared
less than 2 seconds after the call for max power.
- 4th rudder movement starts at 9:16:02.47, moves 20.75
degrees to the left (from right) in .53 seconds, and arrives
at 10 degrees left at 9:16:03 and stays there for 1.00 second
- 5th rudder movement starts at 9:16:04, moves 19.5
degrees to the right (from left) in .50 seconds, and arrives
at 9.5 degrees right at 9:16:04.5 and the rudder position
data in the FDR now becomes "unreliable".
- This analysis raises serious questions about the sequence
of events on board Flight 587. If the rudder movements were pilot
induced, was he responding to wake turbulence? It is very difficult
to see this as a realistic scenario given the analysis above.
It cannot be considered a response if it came before,
or "during", the trigger event (the wake turbulence).
What was the attitude of the plane before and after the alleged
2nd wake encounter? Would it not have been appropriate for the
NTSB to release attitude information along with the Feb. 8th
Safety Recommendation? If you're going to warn pilots to not
use the rudder in certain situations or upsets, wouldn't it be
helpful to pilots to provide them with a complete case study
and reveal as much as was then known about 587's flight profile?
- The NTSB states the information this analysis is based on
is "preliminary". Therefore, no conclusions can be
drawn by anyone using this data. However, Investigators appear
to have behaved in a manner contradictory with that belief since
Safety Recommendations have been issued as a result of analyzing
this preliminary data. And, Investigators have leaked
information to the St. Petersburg Times, and the LA Times, implying
there is increasing evidence the pilot was responsible for the
rudder movements and, therefore, the pilot is indirectly responsible
for the crash. If such actions can be taken by parties to the
Investigation using preliminary data, then is it unprofessional
for parties outside the official investigation to analyze that
same data and come up with their own conclusions? The real issue
is ... why do we have such a paltry amount of information 10
months after America's second worst aviation disaster? We're
not asking for declaration of cause. Just as much factual information
as possible. Hopefully, October will change all that. See illustrations
- Rudder Movements Timeline Picture 1 (see Picture 2 below)
- Rudder Movements Timeline Picture 2 (includes critical
CVR events, transponder problem, and Waveforms of FAA Air Traffic
Control Tape Noises)
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