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Modified August 17, 2002
 
Originally Posted August 6, 2002
 
 
Flight Paths and Wake Probabilities
 
On November 14, 2001, two days after the crash with only the Cockpit Voice Recorder (CVR) to work with, the NTSB focused on the two airframe rattles and a comment by the Captain about wake turbulence. This map was produced by the NTSB, using the Radar Tracks of both JAL 47 and AAL 587. The NTSB commented on that day that the flight paths and events on board Flight 587 were "consistent" with wake turbulence encounters.
 
 
The NTSB did not release all 20 radar hits for flight 587; only the 7 points in red above (which are hard to read on the map above). The 7 radar points for AAL 587 as released by the NTSB are here. The NTSB maintains the 7th hit is "erroneous". The transponder sent the wrong altitude, as I've reported before, and this was not the only erroneous radar hit. The 18 radar hits for AAL 587 (as released by PASSUR) are here, along with JAL 47's first 41 radar hits.
 
I added a few more radar hits to the NTSB map (seen below) to better illustrate where JAL 47 most likely released the vortices that might have encountered AAL 587 (based on wind direction and speed readings taken earlier that morning at altitude ... also available below), I indicate the approximate distances between the two flight paths at the vortex release points and the encounter points, and along with the time separation between the two paths, it is easy to calculate what wind speed is needed to create the encounter, and how far the vortices traveled given the most likely wind conditions that were present that morning.
 
As you can see from the map below, the approximate lateral distances the vortices from JAL 47 traveled are indicated by the sky-blue-colored lines.
 
The first lateral movement being a result of a wake encounter is improbable; the second lateral movement being caused by wake is highly unlikely for three reasons.
 
Reason 1: The vortices only made it about half way to AAL 587 when Flight 587 had experienced its second lateral movement.
 
When the NTSB advised me that the plane never ascended much above 2400 feet, it rendered the second wake encounter practically impossible because the planes were now separated by at least 1000 feet, possibly up to 1400 feet if the winds at altitude at JFK were not from 330 degrees but 270. This vertical separation creates two huge challenges to the wake turbulence theory:
 
Reason 2: According to FAA documents, wake vortices typically dissipate as they fall. By the time the vortices have fallen 900 feet they have dissipated to the point where they level off, or stop falling. Therefore, the FAA has stated it is safe to fly 1,000 feet or more below the plane ahead. And that's where Flight 587 was at according to the NTSB--at least 1,000 feet below JAL 47.
 
Reason 3. Vortices fall at a rate of 300 to 480 feet per minute, or 5 to 8 feet per second. At the time of the second alleged wake encounter, the planes were approximately 99 seconds apart. In that time, and if I'm generous to the wake theory and grant that the vortices fell at maximum rate for the first minute (unlikely), and then traveled at average descent speed for the next 39 seconds (also an unlikely descent rate; it was probably slower), the maximum distance the vortices would have fallen would be 734 feet. Still above AAL 587 by at least 266 feet and possibly as much as 666 feet.
 
But given these issues with this theory, the NTSB still feels comfortable referring to both wake encounters as fact. However, we have been shown no data to support this theory. The NASA wake study which was commissioned for the NTSB will explore what effect the wake had on Flight 587; but the study will not be addressing whether the encounters were likely or not.
 
What if the NTSB has information that proves beyond a reasonable doubt that the second lateral movement was caused by wake turbulence? It is irrelevant. According to the timing of events on board Flight 587, the crew was battling something before the second one-tenth g-force lateral movement. Something fierce. Something that cannot be attributed to a routine encounter with wake vortices. "Something" that took the lives of the crew and all those on board.
 
 
Weather Data
 
The following weather observations for the morning of November 12, 2001 come from National Weather Service Reports and archived data from the National Climatic Data Center.
 
Readings from Brookhaven Airport (OKX) in Shirley, NY are also included for comparison purposes since the closest winds aloft readings to JFK airport are taken at Brookhaven.
 
 Time (Local)  Airport  Direction (True)  Knots
       
       
       
       
       
       
       
       
       
651 AM OKX 250 3
 
(Bold Text Indicates U.S. Read Comments)

NOTIFICATION REPORT (AVIATION)
NATIONAL WEATHER SERVICE NEW YORK NY
1027 AM EST MON NOV 12 2001

TO......FORENSIC SERVICES MANAGER (W/OM113)
NATIONAL WEATHER SERVICE
NOAA MESSAGE CENTER
SILVER SPRING MD 20910

INFO....EASTERN REGION (ATTN: W/ER1X2)

ALPHA...AMERICAN AIRLINES AIRBUS FLIGHT #587

BRAVO...CRASH LOCATION: BEACH 129TH AND NEWPORT AVE IN ROCKAWAY
CRASH TIME: 1417Z
NUMBER ON BOARD: ESTIMATED 255

CHARLIE...AIRCRAFT TOOK OFF FROM JFK AIRPORT FOR SANTO DOMINGO AND CRASHED 2
MINUTES LATER SOUTH OF JFK AIRPORT IN THE ROCKAWAYS.

DELTA...METAR KJFK 121351Z 31011KT 10SM FEW043 06/M06 A3044 RMK AO2

The line above indicates: JFK surface winds at 8:51 AM (23 minutes before Flight 587 lifted off) were from 310 degrees (true) at 11 knots

SLP308 T00561056
METAR KJFK 121425Z 27008KT 10SM FEW048 06/M06 A3044 RMK AO2
FU PLUME S

Two lines above we see "METAR KJFK 121425Z 27008KT". This indicates: JFK surface winds at 9:25 AM, 9 minutes after the crash, were from 270 degrees (true) at 8 knots

Editor's Note: JFK surface winds at 9:15:09 AM, when Flight 587 was airborne and only 30 seconds from its first alleged wake encounter, were from 287 degrees (true) at 8 knots. Source: FAA Local Control Transcript

ECHO...KJFK 121130Z 121212 31011KT P6SM SKC
BECMG 1315 32013G18KT SCT040

Previous two lines are forecasts issued at 6:30 AM for 7 AM on the 12th of November until 7 AM the next day. The forecast was for 310 degrees (true) at 11 knots becoming 320 degrees between 8 am and 10 am from 320 degrees (true) at 13 knots gusting to 18.

FM2100 31011KT P6SM SCT250
BECMG 0103 32006KT
FM0800 VRB03KT 32006KT

FOXTROT...UPPER LEVEL WINDS FROM 12Z KOKX SOUNDING
1099 FT...315/16KT
1945 FT...325/18KT
2779 FT...334/19KT
3579 FT...342/19KT
4468 FT...346/24KT


 
Editor's Notes
All wind directions above and below are in True heading (not Magnetic).
 
Winds aloft at JFK
 
The forecast for JFK surface winds at 7 AM was 310 degrees at 11 knots, which is the same wind direction and speed observed at JFK at 8:51 AM indicating the forecast was a good one.
 
At 7 AM, Brookhaven balloon soundings of winds aloft (the closest balloon soundings to JFK), showed a plus 15 degree variation at 1900 feet, compared with the JFK surface winds forecast for 7 AM. The soundings also showed, approximately, a plus 20 degree variation at 2400 feet.
 
At 8:51 AM, the JFK surface winds had dropped 27% from 11 knots to 8 knots but the wind direction was still from 310 degrees.
 
When Flight 587 was airborne at 9:15 AM, the JFK surface winds were still at 8 knots and wind direction now had a minus 23 degrees variation to 287 degrees from the 310 degrees that was recorded 24 minutes earlier at 8:51 AM.
 
In the FOXTROT section above ... we have the results of the Brookhaven Upper Level Winds Soundings. To those numbers I applied the 27% velocity drop and minus 23 degree direction variation to come up with these estimates for winds aloft at JFK at 9:15 AM:
U.S. Read's Estimates for Winds Aloft At 9:15 AM
1900 FT - 302 degrees / 14 knots
2400 FT - 306 degrees / 14 knots
3000 FT - 313 degrees / 14 knots
3600 FT - 319 degrees / 14 knots
 
A Meteorologist who lost a family member on Flight 587 remembers the weather conditions well for that day. "I remember that morning well and the air was very stable. I think that the wind at 2000 to 3000 feet could well be the same as on the ground or slightly higher. I think it is a fair assumption that the winds aloft would be similar at Brookhaven and JFK."
 
Analysts at the National Weather Service office near Brookhaven, NY remembered weather patterns (including winds aloft) around the entire region (extending beyond JFK) were similar.

 


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