The following is my original analysis and opinion. Feel free to repost anywhere you feel appropriate, as long as you attribute it to Daniel Baisley and include it in it's entirety, unedited, including my opinion statement at the end.
The accident aircraft starts a decent from 1000 feet at 00:32 UTC per flightradar24 data. It appears to descend at approximately 500 FPM with no apparent change in vertical speed prior to the last recorded data point. The recorded direction of travel changes by a few degrees starting at the top of descent.
http://www.flightradar24.com/data/airplanes/n622bt/#7e426b3
The JFK weather surrounding the time of the accident was:
METAR KJFK 042351Z 10003KT 10SM CLR 14/11 A3035 RMK AO2 SLP278
METAR KJFK 050051Z 08004KT 10SM CLR 14/12 A3035
So, clear weather, high pressure, calm winds, and the high temp / DP spread means fog was not likely to form. This sounds like a nice night to fly to me.
The Top-Of-Descent point is directly underneath the Parkway Visual 13 approach approach to JFK. The Canarsie VOR/GPS approach overflies this same path.
http://www.airnav.com/depart?http://155.178.201.160/d-tpp/1511/00610PARKWAY_VIS13LR.PDF
Theory: A wake turbulence encounter with an aircraft on the Parkway Visual runway 13 approach caused this accident.
Looking at the approach plates for both approaches, aircraft on that approach would have typically been at 2000-3000 MSL as they flew over the TOD point.
How fast does wake turbulence sink? A quick google search will tell you 500-300 FPM. A more critical reading indicates that it actually sinks at an initial rate of 500-300 FPM for the first 30 seconds the slows down, eventually settling approximately 1000 feet lower than the altitude where it was generated. So it seems 2000 feet of vertical separation would have provided adequate margin, and 1000 feet would be cutting it close, but lets run with this. I was unable to find any experimental data or mathematical model for wake turbulence sink rate after 30 seconds. Lets SWAG an average sink rate of 200FPM for the wake turbulence. I may have access to better analysis or research at work, but I would not be able to share it publicly because of proprietary data restrictions.
Point of curiosity - I'd assume that most airline pilots fly the parkway visual these days by loading the GPS 13 approach and following the magenta line, at least in modern FMS equipped aircraft. I wonder what impact this has had on wake turbulence over time - does it increase the strength of the wake vortex to have multiple aircraft overflying precisely the same ground track? Does it change the rate at which it sinks? Do the vortices tend to sink to 1000' below the approach path and "stack up", creating a semi-permanent vortex field along the route of a busy approach corridor? Pretty much ALL our data on wake vortex behavior comes from the NASA Dryden flight tests in the 1970's. It would be interesting to repeat the Dryden wake vortex experiments with modern aircraft and equipment to study this. Shall I file for a grant, or would this be is a waste of government funding to accommodate a special interest group? Perhaps you would prefer to pay for another mid-east war instead? Food for thought.
https://www.youtube.com/watch?v=t8zLBLYNWLo
Anyway, an aircraft passing over the TOD at 2000'-3000' on the parkway visual at approximately 00:22-00:27 UTC could have caused a wake turbulence encounter at 1000' at 0:32 UTC. It's around 4 minutes-ish at turbine approach speeds from the the TOD point to arrival at JFK on the parkway approach, so we are looking for a 00:26-00:31 arrival at JFK on runway 13 plus or minus a few minutes to account for all the wild arse guesses we took regarding the altitude and speed of the assumed conflicting aircraft.
There are three aircraft which met this criteria on that day: Jetblue 936 (A320) arrived 00:34, Cathay 840 (B77W) arrived 00:30, Jetblue 852 (A321) arrived 00:27. Looking at their flight data on flightradar24, including exact altitude and time when overflying the TOD point, and assuming a 200 FPM average sink rate for a wake vortex, Cathay 840's (B777) wake turbulence would have sunk to 1000 MSL at the TOD point at approximately 00:30. Not far off from the start of the accident aircraft's descent at 00:31. The prior aircraft would have hit about 5 minutes earlier, the next one is 5 minutes later, and both are the much smaller Jetblue A320 series aircraft.
http://www.flightradar24.com/data/airplanes/b-kpk/#7e27f69
My prediction of the probable cause: a wake turbulence encounter with Cathay Pacific flight 840, a Boeing 777-300ER which passed over the accident aircraft's top of descent point at 2300 MSL at 7:24 PM. Assuming a 200 FPM sink rate this puts the wake turbulence at the location of the top of descent at approximately 00:30. Data indicates that the accident aircraft began it's final descent at 00:31 Additional examination of the wreckage is required to determine if the departure from controlled flight was caused by structural failure, limited control authority to overcome the rotation of the vortex, inadequate power to escape a sustained downdraft, a combination of the above, or other unidentified factors.
My engineering analysis of possible contributing factors and recommended mitigation: Investigation should be done as to the effect of multiple aircraft overflying the exact same path in calm wind conditions to determine if recent advances in high precision navigation technology have changed the intensity or sink rate of wake turbulence in actual operations. Statistical analysis should be done to determine if gust factors which were developed decades ago and are used for sizing flight critical components are still relevant in today's environment. Finally, I am not sure whether ASTM consensus-standard LSA aircraft (contrary to another poster's assertion, the accident aircraft was NOT a homebuilt or experimental aircraft) are designed to the same gust factors as FAR Part 23 certified aircraft. Both the requirement, and the process used to show compliance should be reviewed to ascertain whether they were adequate to ensure a robust design, sized for the intended use.
Here is an interesting NTSB report regarding a Grumman Tiger which encountered wake turbulence from an Airbus A300B4-600 (slightly smaller than a 777) and subsequently experienced structural failure of a flight control component. The vertical separation was way less than this accident. The pilot said the flight control in his left hand felt "like the handle of a sledge hammer when you strike a steel pipe." The outboard wing section of the Grumman was bent up at a 5? angle. The aileron counterbalance weights snapped off at their welded attachment to the steel torque tube, fell to the ground, and penetrated through the roof of the an apartment below. The aircraft landed safely with no injuries to passenger or crew. It was repaired and is still flying in the LA area today. Grumman designed and tested the Tiger far in excess of FAR 23 requirements.
http://www.ntsb.gov/_layouts/ntsb.aviation/brief2.aspx?ev_id=20001212X20121&ntsbno=LAX00LA035&akey=1
I have to say I am greatly disappointed by the rush of pilots on this forum to jump to a conclusion which assigns blame to the pilot without doing any original research to validate media reports or to understand normal local operations in this airspace. This particular route of flight is flown probably a dozen times an hour by VFR traffic in the area. 1000 feet Sandy Hook to Breezy Point, then 400 feet along the shoreline under the class B shelf. You normally talk to JFK tower. In fact the area under the class B shelf USED to be class D airspace and REQUIRED talking to the tower. It appears that there is no longer a requirement to do so? That seems like a short-sighted decision which was driven by controller workload and likely a lack of funding. Anyway, a hundred flights a day have been doing this for many decades. WAY longer than my 40 years anyway alive, anyway. This is the first accident I have heard of along this route to be caused by a wake turbulence encounter. I have flown this route hundred of times myself. I have flow it on CAVU days, at night, on hazy days, under a ceiling, and in precipitation with adequate visibility. I do avoid hazy nights because that is a ticket to a short life and is a silly thing. I wonder if I will ever be permitted to fly this beautiful (and expedient!) route again. The irrational posts by other pilots on this thread with zero local knowledge inspired me to post a video of a very typical use of this VFR corridor.
https://youtu.be/0Ak0_mszWeE
Further, you all saw the quote "Divers were in the water all night searching for debris. Their efforts were hampered by poor visibility" and assumed that meant poor flight visibility. The pictures below this quote directly contradict your conclusion, they show a flight visibility which I would estimate to be ~10 miles. I validated this by checking the historical METARs for JFK at the time. A rational conclusion would be that a diver's ability to search the water would be limited by
underwater visibility, not flight visibility. You used a one sentence quote from the
NEW YORK DAMN DAILY NEWS to indict a deceased fellow pilot without bothering to validate media reports and witness quotes with a third party. No offense, but your critical reading, reasoning skills, and ethics all suck and you should make an effort to further develop all of the above. You should be ashamed of yourselves for projecting your own lack of knowledge on a dead fellow pilot. Not everyone is as uninformed as you. Ban me, unfriend me, or kick me in the jimmy at Oshkosh this year if you think it will make your hurt feelings any better.
