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Weather analysis for an accident of a TBM-700 near Morristown, NJ

Posted by Scott Dennstaedt 
Weather analysis for an accident of a TBM-700 near Morristown, NJ
December 21, 2011 09:27AM
Disclaimer: Please note that the analysis to follow may contain errors and omissions. It has been prepared for educational purposes only and does not reflect the view of the NWS, NTSB, FAA or any of their personnel, agents or organizations. If you would like to learn more about aviation weather, please visit [avwxworkshops.com]



At about 15Z (10 am EST) on December 20, 2011, a TBM-700 (N731CA) departed controlled flight after leaving Teterboro in northern NJ. The aircraft crashed close to I-287 near the Morristown, NJ airport (KMMU) in north-central NJ. The NTSB reported in a news conference that the wreckage covered nearly one-half of a mile with some witnesses suggesting the aircraft may have broken up in flight while in a rapid descent.

http://avwxworkshops.com/etips/images/FA-Track.gif



Here is the preliminary NTSB report associated with this accident:

NTSB Identification: ERA12FA115
14 CFR Part 91: General Aviation
Accident occurred Tuesday, December 20, 2011 in Morristown, NJ
Aircraft: SOCATA TBM 700, registration: N731CA
Injuries: 5 Fatal.

This is preliminary information, subject to change, and may contain errors. On December 20, 2011, about 1005 eastern standard time, a Socata TBM 700, N731CA, collided with terrain following an in-flight loss of aircraft control near Morristown, New Jersey. The airplane was registered to Cool Stream LLC and was operated by the pilot. Visual meteorological conditions prevailed and an instrument flight rules flight plan was filed for the flight from Teterboro, New Jersey [TEB] to Atlanta, Georgia [PDK]. The personal flight was conducted under the provisions of 14 Code of Federal Regulations Part 91. The airplane sustained substantial damage. The certificated private pilot and four passengers were fatally injured. The flight originated from TEB at 0950.

A preliminary review of recorded radar and voice communications revealed that the pilot was in communication with the Federal Aviation Administration, New York Air Route Traffic Control Center (ARTCC). While flying at 17,000 feet mean sea level (MSL) the pilot reported that he was in icing conditions. The pilot requested a climb, and the flight was subsequently cleared to flight level (FL) 200. The aircraft reached a maximum altitude of 17,900 feet and then began to descend. Radar and radio contact with N731CA was lost about 1005.

The airplane impacted a wooded median on Interstate Highway 287, about 1 mile south of Morristown. Several sections of the airplane, including the propeller assembly, came to rest in a wooded area on the east side of the northbound lanes. A post-crash fire was evident in the highway median, where the fuselage came to rest. The outboard section of the right wing and several sections of the empennage were found about 0.25 miles southwest of the fuselage, in a residential area.

The pilot held a private pilot certificate with ratings for airplane single-engine land and instrument airplane. He reported a total flight experience of 1,400 hours on his latest second-class medical certificate application, dated July 14, 2011.

The airplane was manufactured in 2005 and equipped with a Pratt and Whitney Canada PT6A-64 turbo-prop engine. The most recent annual inspection was performed on July 27, 2011. At that time, the airplane had accumulated approximately 702.0 total flight hours. The last logbook entry was recorded on November 18, 2011, at an aircraft total time of 724.6 hours.

The wreckage was recovered to a storage facility, where a detailed examination will be performed NTSB.



The pilot was climbing to a cruise altitude of 26,000 feet headed southwest to Atlanta according to FlightAware. At this point it is unknown if weather was a causal factor in this terrible accident that claimed five people and a dog. There is speculation in the press and within the pilot community that structural icing caused the plane to depart controlled flight and crash.

Structural icing is produced when an aircraft flies through visible moisture that is in liquid form (cloud or rain drops) when the static air temperature is below 0°C (technically it is the temperature of the skin of the aircraft that matters). This is referred to as supercooled liquid water. Supercooled liquid water is quite common when the outside air temperature is between 0°C to -20°C. As an aircraft enters into this environment, the supercooled liquid water will freeze onto the airframe. If not removed, the ice accretions can disrupt the aerodynamic flow over the lifting surfaces causing the wing to stall at higher indicated airspeeds. It can also cause the static port and/or pitot tube to freeze giving the pilot erratic or erroneous indications of airspeed and altitude.

Some aircraft are equipped with certified ice protection systems that can shed most of the ice accretions. The TBM-700 is certified into known icing conditions. However, like many aircraft it is not certified into an environment with supercooled large drops (SLD). A description of SLD can be found in this FREE e-Tip.

However, moderate structural ice was being reported by many pilots throughout the NY area during most of the morning. This included at least two urgent pilot reports (PIREPs) of moderate to severe ice as shown below. Severe icing is typically reported when the ice accretion is overwhelming the ice protection system (IPS).

MMU UUA /OV MMU/TM 1308/FL140/TP MD83/TA 04/IC MOD-SEV RIME 140-165
SMQ UUA /OV BWZ250030/TM 1542/FL140/TP MULTIPLE/IC MOD-SEV RIME/RM ABE FL140-175

The first report was two hours prior to the accident over MMU at 1308Z. This was from an MD80 at 14,000 feet which reported moderate to severe icing between 14,000 ft and 16,500 feet. Based on the final NTSB report, "One of the flight crewmembers reported that the icing was the worst he had seen in 38 years of flying experience and that he had never seen ice accumulate so quickly." The report has a temperature aloft (TA) of +4°C at 14,000 feet. This temperature is inconsistent with other pilot reports in the area, and is inconsistent with the sounding analysis posted below which indicated a temperature at 14,000 feet of approximately -11°C.

LATER NOTE: I was informed by an MD80 pilot that pilot may have erroneously reported the total air temperature (TAT) and not the temperature aloft (TA) or static air temperature (SAT). Evidently, the TAT is much more prominent on the MD80 instrument panel. If true, this would be nearly a 15°C rise which is still inconsistent with NASA calculations. According to NASA, kinetic heating causes the TAT to be warmer than the SAT. For example, if the SAT is -2°C, an aircraft traveling at 250 knots would observe a TAT of approximately +5°C.

An interview with the captain of a Bombardier CRJ aircraft that was operating close to the accident aircraft reported that the wing anti-ice system could not “keep up” with the accumulation. He estimated 2.5 inches of ice on the protected areas of the wing, and 4 inches accumulation on some unprotected areas in a time span of about five minutes. He described “golf ball-sized” accumulation on the windshield wiper.

The second report was further west of MMU and was likely called in by the NY center (ZNY) controller given that the aircraft type (TP) indicates "multiple" implying multiple aircraft reporting moderate to severe ice. This was about 30 minutes after the accident, but certainly consistent with the other pilot reports in the area in and around MMU.

The entire NYC area was covered in a couple dozen moderate reports of icing as shown in the list below. These reports are from 12Z through 16Z within 200 miles of the accident site near Morristown, NJ. Notice the abundance of moderate icing reports from large turbojet aircraft. Most of these are between 12,000 feet and 19,000 feet with a fair number of moderate reports at 17,000 feet. This weather event wasn't suffering from the lack of PIREPs. If this doesn't get your attention, I don't know what will.

ELM UA /OV ULW/TM 1157/FL160/TP DH8D/TA M11/IC MOD MX 160
LNS UA /OV LRP045015/TM 1159/FL160/TP SF34/TA M09/IC MOD RIME
ABE UA /OV FJC150010/TM 1200/FL120/TP CRJ7/SK OVC/WX IMC/TB LGT-MOD/IC LGT RIME
PTW UA /OV PTW32010/TM 1205/FL170/TP E170/SK OVC/WX IMC/IC MOD MX/RM ICING 140-170
HPN UA /OV HPN/TM 1210/FL170/TP A320/TA M09/IC MOD RIME
JFK UA /OV JFK156020/TM 1214/FL130/TP A320/IC LGT RIME/RM FL130BFL180
HTO UA /OV HTO240050/TM 1216/FL140/TP MU2/TA M17/IC MOD RIME/RM FL140-180
MJX UA /OV CYN090010/TM 1218/FL140/TP E190/IC LGT RIME/RM JFK FL140-170
MJX UA /OV CYN090020/TM 1219/FL160/TP E190/IC MOD RIME/RM JFK FL120-160
TTN UA /OV RBV180020/TM 1220/FL140/TP E190/TA M13/IC LGT RIME/RM JFK
SMQ UA /OV SBJ030/TM 1220/FL140/TP A320/TA M14/IC LGT-MOD CLR 140, MOD RIME 150-175/RM EWR
JFK UA /OV JFK140040/TM 1222/FL140/TP E170/TA M10/IC MOD RIME
BUF UA /OV DNY220010/TM 1226/FL190/TP B737/TA M18/IC MOD RIME
POU UA /OV PWL270012/TM 1242/FL180/TP E170/TA M16/IC LGT RIME
IPT UA /OV LRP065010/TM 1246/FL160/TP A320/TA 07/IC MOD MX 140-160
FWN UA /OV SAX090020/TM 1248/FL150/TP E170/TA M01/IC LGT-MOD MX
JFK UA /OV JFK156020/TM 1255/FL130/TP A320/TB LGT/IC LGT RIME/RM 130BFL180
BDR UA /OV BDR/TM 1255/FL180/TP B737/TA M18/IC LGT-MOD RIME
HPN UA /OV LGA360015/TM 1301/FL140/TP A320/TA M14/IC LGT RIME 140-170
PHL UA /OV OOD/TM 1302/FL130/TP 717/TA M10/IC LGT RIME 130-160
MMU UUA /OV MMU/TM 1308/FL140/TP MD83/TA 04/IC MOD-SEV RIME 140-165
HTO UA /OV HTO/TM 1309/FL185/TP B737/TA M18/IC MOD MX 185-135/RM /TA M18 TO M10
SMQ UA /OV MMU270010/TM 1310/FL135/TP E190/SK OVCUNKN-TOP155/TA M12/IC MOD RIME 135-155
SNC UA /OV MAD/TM 1313/FL170/TP LJ31/TA M10/IC LGT RIME
HPN UA /OV HPN315015/TM 1315/FLUNKN/TP A319/TA 04/TB LGT CHOP 150-160/IC LGT RIME 150-160
AVP UA /OV AVP090005/TM 1334/FL050/TP C208/TA M06/IC LGT MX
LGA UA /OV JFK360010/TM 1336/FL130/TP B752/TA M08/IC LGT RIME 130-150
BDR UA /OV BDR180010/TM 1337/FL170/TP B737/TA M10/IC LGT RIME 170-150
IJD UA /OV ORW270010/TM 1339/FL190/TP E190/TA M18/IC MOD RIME
FWN UA /OV SAX/TM 1353/FL170/TP CRJ9/TA M14/IC MOD RIME
SMQ UA /OV BWZ/TM 1356/FL130/TP S340/SK OVC/WX IMC/IC MOD MX
SEG UA /OV MIP/TM 1357/FL050/TP C208/TA M05/IC LGT RIME
JFK UA /OV JFK180040/TM 1402/FL180/TP C56/TA M10/IC MOD RIME
FWN UA /OV 4N1315005/TM 1410/FL035/TP C172/SK SCT030/WX FV07SM/TA M01/RM SMTH
RDG UA /OV ETX070010/TM 1413/FL140/TP E190/TA M14/IC MOD RIME 140-160/RM ABE
ITH UA /OV ELM090020/TM 1422/FL037/TP BE99/SK OVC030-TOP040/TA M02/IC TRACE-LGT RIME
JFK UA /OV DPK205027/TM 1422/FL170/TP E190/TA M14/IC MOD CLR
ISP UA /OV DPK090010/TM 1427/FL133/TP E190/SK OVC133-TOPUNKN/TA M14/IC MOD MX 133-180
12N UA /OV BWZ090005/TM 1430/FL135/TP CRJ2/TA M12/IC MOD RIME 135-170
PNE UA /OV RBV240010/TM 1440/FL150/TP A319/TA M09/IC LGT RIME
RDG UA /OV ETX/TM 1458/FL140/TP DH8D/TA M8/IC MOD MX/RM MOD MX ICING 140 ETX225010
RDG UA /OV ETX/TM 1502/FL120/TP DH8D/TA M07/IC MOD MX
JFK UA /OV JFK225010 /TM 1510 /FL120 /TP A320 /TA M07 /IC MOD RIME
OXC UA /OV BDR360025/TM 1511/FLUNKN/TP B737/TA UNKN/IC MOD MX 185-200
APG UA /OV BWI045040/TM 1535/FL110/TP DH8D/TA M02/IC LGT RIME/RM DURD 110-060/TA01 AT 070/RIDE IMPROVES DURD NEG IC 090/ TWO CLD LYRS 090 AND 070
SMQ UUA /OV BWZ250030/TM 1542/FL140/TP MULTIPLE/IC MOD-SEV RIME/RM ABE FL140-175
RDG UA /OV ETX/TM 1542/FL120/TP SF34/TA M05/IC LGT-MOD MX
ABE UA /OV FJC270015/TM 1547/FL130/TP MD82/TA M08/IC LGT RIME

This graphic below plots all of the icing PIREPs between 12Z and 14Z. The orange symbols are reports of moderate icing. Many are focused right around NYC.

http://avwxworkshops.com/etips/images/Charted-Icing-PIREPs.gif




At 0845Z, the Aviation Weather Center issued AIRMET Zulu (below) for moderate ice between the freezing level and 14,000 feet. The bounds of the AIRMET included the accident site and this AIRMET was valid through 15Z.

000
WAUS41 KKCI 200845
WA1Z
BOSZ WA 200845
AIRMET ZULU UPDT 1 FOR ICE AND FRZLVL VALID UNTIL 201500
.
AIRMET ICE...NY NJ PA OH LE WV MD DC DE VA AND CSTL WTRS
FROM DXO TO 30S HNK TO 60ESE HTO TO 140ESE ACK TO 200SE ACK TO
160SE SIE TO 20W RIC TO 50W CSN TO HNN TO CVG TO FWA TO DXO
MOD ICE BTN FRZLVL AND 140. FRZLVL 030-090. CONDS CONTG BYD 15Z
THRU 21Z.
.
FRZLVL...RANGING FROM SFC-120 ACRS AREA
SFC ALG 20NE DXO-40WNW ERI-20SSE SLT-30WNW SAX-100SSW YSJ
040 ALG 20S FWA-30ENE EMI-100S ACK-160ESE ACK
080 ALG 20N CVG-180ESE SIE
....


http://avwxworkshops.com/etips/images/0845Z-AIRMET.gif


Here is the freezing level forecast as derived from the AIRMET text above...

http://avwxworkshops.com/etips/images/0845Z-Freezing-Level.gif



This AIRMET was subsequently amended by the Aviation Weather Center at 1158Z to include moderate ice from the surface to FL180. The amendment was likely prompted by the copious pilot reports that were streaming in. In either case, a briefing through Lockheed Martin Flight Services or DUATS after 12Z would have included the amended AIRMET containing the new higher altitude icing limit. However, the northern edge of the AIRMET was moved further south with this amendment. That put the flight path just on the northern edge of the boundary of this amended AIRMET.

000
WAUS41 KKCI 201158 AAA
WA1Z
BOSZ WA 201158 AMD
AIRMET ZULU UPDT 2 FOR ICE AND FRZLVL VALID UNTIL 201500
.
AIRMET ICE...NY NJ PA OH LE WV MD DC DE VA AND CSTL WTRS...UPDT
FROM DXO TO 40SSE HNK TO 70SSW ACK TO 130ESE ACK TO 200SE ACK TO
180SE SIE TO 20W RIC TO 50W CSN TO HNN TO CVG TO FWA TO DXO
MOD ICE BTN FRZLVL AND FL180. FRZLVL 030-090. CONDS CONTG BYD 15Z
THRU 21Z.
.
FRZLVL...RANGING FROM SFC-120 ACRS AREA
SFC ALG 20NE DXO-40WNW ERI-20SSE SLT-30WNW SAX-100SSW YSJ
040 ALG 20S FWA-30ENE EMI-100S ACK-160ESE ACK
080 ALG 20N CVG-180ESE SIE
....


Here is the location of the amended AIRMET issued at 1158Z.

http://avwxworkshops.com/etips/images/1158Z-AMD-AIRMET.gif




At 1445Z the Aviation Weather Center issued the next round of AIRMETs that included this one (below) for moderate ice between the freezing level and FL200.

000
WAUS41 KKCI 201445
WA1Z
BOSZ WA 201445
AIRMET ZULU UPDT 3 FOR ICE AND FRZLVL VALID UNTIL 202100
.
AIRMET ICE...MA RI CT NY NJ PA OH LE WV MD DC DE VA AND CSTL WTRS
FROM DXO TO 150ESE ACK TO 200SE ACK TO 160SE SIE TO 40WSW SBY TO
HNN TO CVG TO FWA TO DXO
MOD ICE BTN FRZLVL AND FL200. FRZLVL 020-080. CONDS CONTG BYD 21Z
THRU 03Z.
.
OTLK VALID 2100-0300Z...ICE MA RI CT NY NJ PA OH LE WV MD DC DE
VA NC SC GA AND CSTL WTRS
BOUNDED BY ERI-150ESE ACK-200SE ACK-210SSE HTO-100ESE SIE-20WSW
SIE-CSN-20SSW IRQ-LGC-GQO-HMV-HNN-CVG-FWA-40SW DXO-20SE DXO-ERI
MOD ICE BTN FRZLVL AND FL200. FRZLVL 020-120. CONDS CONTG THRU
03Z.
.
FRZLVL...RANGING FROM SFC-110 ACRS AREA
SFC ALG 70WSW YYZ-HNK-40W BOS-70ESE ENE-140SSE BGR
040 ALG 20S FWA-30N ROD-50SSE ETX-120SSE ACK-180SE ACK
080 ALG CVG-20NNE HNN-210SSE HTO
....


http://avwxworkshops.com/etips/images/1445Z-AIRMET.gif




Many serious icing scenarios are located near frontal systems. This surface analysis loop from 00Z to 15Z shows a cold front pushing to the southeast as the occluded low pressure center in Quebec moves off to the northeast.

http://avwxworkshops.com/etips/images/00Z-15Z-SA-Loop.gif




Consequently, by 15Z the cold front begins to slow its forward progress and begins to settle just north of the Mason-Dixon line. A ridge of high pressure is present to the north over Quebec, Canada.

http://avwxworkshops.com/etips/images/15Z-Dec20-Surface-Analysis.gif




There were plenty of clouds oriented west to east along the north side of the slowing cold front as can be seen in this visible satellite image at 1445Z.

http://avwxworkshops.com/etips/images/1445Z-Visible-Satellite.jpg




The moisture in this area was rather deep and oriented in a thin band along the northern side of the cold front. Green solid contours are relative humidity based on the scale shown on the bottom right. The charts in this three-image loop are 850 mb (5,000 ft), 700 mb (10,000 ft) and 500 mb (18,000 ft). The nearest upper-level trough was located in the Midwest.

http://avwxworkshops.com/etips/images/RUC-Upper-Air-Analysis.gif




All of the NEXRAD sites in the area (DIX, OKX and BHM) were all in clear air mode. The highest elevation angle in this mode is 4.5 degrees and the 0.5° base reflectivity image is only updated every 10 minutes. Based on this NEXRAD image below from the Philadelphia radar (DIX) valid at 1504Z, most of the precipitation was located in southern NJ, Delaware and Maryland just south or along the cold front. A little light precipitation was also falling in east-central NJ.

http://avwxworkshops.com/etips/images/1504Z-DIX-Radar.gif


However, the Binghamton radar (BHM) below does show some very light precipitation (less than 10 dBZ) in the airspace between TEB and MMU. Precipitation can certainly increase the risk of icing, specifically large drop icing.

http://avwxworkshops.com/etips/images/1510Z-BHM-Radar.gif




Given the precipitation in the area. it's very interesting that Teterboro (TEB ) and Caldwell (CDW) were both reporting clear skies at 1451Z and 1453Z, respectively. Morristown (MMU) was reporting overcast at 20,000 ft at 1445Z. Caldwell is a towered airport that sits between TEB and MMU. Most likely the AWOS-3 at MMU was reporting clear below 12,000 ft and the human observer augmented the report to include the high overcast deck (that may have been an educated guess as to the height of this layer and it may have been lower). It could also be that the AWOS report for TEB and ASOS report for CDW reported clear below 12,000 feet and the observation was not augmented to include the higher cloud deck.

KTEB 201451Z 34008KT 10SM CLR 07/M02 A3017
KCDW 201453Z VRB04KT 10SM CLR 06/M01 A3018 RMK AO2 SLP225 T00561011 51025
KMMU 201445Z 36008G13KT 10SM OVC200 06/M02 A3017 =

Newwark, NJ (south of the route) and NYC (east of MMU/TEB ) were reporting a broken ceiling of 12,000 feet.

KEWR 201451Z 35012G19KT 10SM FEW040 BKN120 07/M02 A3017
KNYC 201551Z AUTO 36005KT 10SM BKN120 07/M01 A3019 RMK AO2 SLP216 T00671011



Cloud top temperatures throughout northern NJ were rather warm with temperatures around -15°C to -20°C according to this IR satellite image valid at 1445Z. Cloud top temperatures this warm (in a relative sense) indicate that supercooled liquid water is likely to be present in the clouds below. It is possible in some locations (especially in northern NJ) that tops might have been a bit higher and that may have been due to a slightly thin layer above.

http://avwxworkshops.com/etips/images/1445Z-IR-Satellite.jpg




Given these cloud top temperatures and this RUC sounding for Newark, NJ (KEWR) valid at 15Z, a temperature between -15°C and -20°C places the tops between 18,000 ft and 19,000 ft. A top around 18,000 feet is also consistent with this sounding analysis.

http://avwxworkshops.com/etips/images/15Z-EWR-Sounding.gif




The satellite derived product shown below is one way to locate the icing threat in a cloud deck. This image from 1515Z shows the cloud phase based on the legend at the right. The baby blue color in PA and the northern half of NJ is showing clouds that are likely dominated by supercooled liquid water.

http://avwxworkshops.com/etips/images/Cloud-Phase-1515Z.gif




The Current Icing Product (CIP) can also be of help to determine the top of the icing layer. The loop below shows the icing severity analysis from 9,000 ft to FL230 valid at 15Z. Icing severity is presented in shades of blue starting out with trace (light cyan) to heavy (dark blue). Notice in this loop that all of the potential for icing disappears at about FL230. But in the immediate area to the west of TEB, the icing tops out around FL190 or 19,000 feet. At 17,000 feet where most of the moderate icing reports were located, CIP identified mostly moderate ice with a few pixels here and there of heavy ice. But it is also interesting to see that a couple of pixels just over the crash site to contain no ice at 13,000 ft and 15,000 ft. This may be due, in part, to the CLR reports at TEB and CDW.

http://avwxworkshops.com/etips/images/CIP-Loop-15Z.gif




Based on the CIP analysis shown below valid at 15Z, supercooled LARGE drop (SLD) icing was not an immediate threat either. This image is a "smear" of the icing severity analysis plus SLD over the altitudes from 14,000 through 18,000 feet. What this means is that the maximum intensity from 14,000 to 18,000 feet is shown. The purple colors are areas of SLD. While there was a risk of heavy icing to the west of the accident site in extreme eastern Pennsylvania, there wasn't SLD analyzed anywhere near the accident site in northern New Jersey. Of course SLD cannot be ruled out just because of the CIP analysis.

http://avwxworkshops.com/etips/images/15Z-CIP-SLD-Smear-14K-18K.gif




We don't know what weather data the pilot used to make his decision to fly through this weather. There were obviously many pilot reports available that clearly demonstrated the risk of moderate or greater structural icing in a layer from 14,000 ft through 19,000 ft. The Current Icing Product shown earlier was valid at 15Z or after the pilot was airborne. On the other hand, the chart below is the icing severity analysis valid at 14Z; this chart should have been available before the pilot departed TEB (it would have been posted on ADDS at 1415Z). Like the 15Z CIP, this shows mostly moderate ice with some heavy icing (dark blue) just to the west of TEB.

http://avwxworkshops.com/etips/images/CIP-14Z-15K.gif




CIP is an analysis of the icing environment that is always valid in the recent past. However, the Forecast Icing Product or FIP will provide an icing forecast out to 12 hours. FIP is issued every hour and produces a forecast for 1, 2, 3, 6, 9 and 12 hours. The 3-hr forecast for FIP valid at 15Z would have been available to the pilot prior to departure. Shown below is the icing probability forecast in percent for 13,000 ft through 17,000 ft. The higher probabilities are shown in the "warmer" colors such as red, orange and yellow with lower probabilities shown using "cooler" colors such as blue and green. Clearly this forecast shows a fairly high probability of icing on a climb through this layer. Please note that this is a calibrated probability and takes into account uncertainty due to forecast length as discussed more thoroughly in this FREE e-Tip.

http://avwxworkshops.com/etips/images/FIP-Loop-13K-17K.gif




Of course, this says nothing about the icing intensity. Below is the FIP icing severity forecast valid at 15Z using the same altitudes as above. This clearly shows the potential for moderate icing with some patches of heavy icing in northern NJ at 13,000 ft and 15,000 ft.

http://avwxworkshops.com/etips/images/FIP-Severity-Loop-13K-17K.gif




It is difficult to say what might have occurred. Did the ice protection system fail in some way during the climb through a layer of moderate to potential heavy ice? Was the aircraft loaded in such a way that it made recovery difficult? Did the aircraft just find some really nasty icing during the climb? If so, why was this a particularly nasty icing scenario? Icing is one of those adverse weather elements that's hard to predict. It can go from being very benign to very dangerous in just 15 to 20 minutes within the same airspace.

Often it is tempting to look at thermodynamic charts such as the Skew-T log (p) diagram for answers. As mentioned above, these will give a good indication of the location of the tops when used in conjunction with the infrared satellite image. The RUC sounding analysis below is valid at 15Z and right near the accident site. And below that is the sounding from the North American Mesoscale (NAM) model. These two models are run at different times so there are differences to be expected. Can't say for sure which is "more correct" than the other. The red line is the environmental temperature and the green line is the dewpoint temperature. Don't worry about the other lines.

The RUC model (first diagram) seems to have handled the moisture better above 18,000 feet given the temperature-dewpoint spread here. We verified that with the IR satellite image. Whereas, the NAM carries moist conditions up to the tropopause which doesn't seem correct given the IR satellite tops presented above. Does this invalidate the NAM? Not necessarily. The interesting feature on the NAM is the temperature inversion located about 600 mb which is roughly 14,000 feet. This feature does not appear as pronounced on the RUC. Nevertheless, both soundings do suggest stable conditions below the cloud base.

Why is this important? A temperature inversion near/below the cloud base will often keep the clouds above quite clean. Cleaner clouds often result in fewer, but larger drops. Larger drops will tend to penetrate the boundary layer of the wing's surface well behind the protected part of the aircraft. This is why supercooled large drop (SLD) icing is so insidious. Of course, we don't know if SLD was present in these clouds. But if stable conditions existed as suggested by these soundings, it may explain why this layer was getting so many PIREPs of moderate ice.

http://avwxworkshops.com/etips/images/15Z-RUC-Accident-Site.png

http://avwxworkshops.com/etips/images/15Z-NAM-Accident-Site.png




If you have any further questions or comments about this weather analysis, please feel free to contact me.

Scott Dennstaedt
CFI & former NWS meteorologist
Administrator of AvWxWorkshops.com
Most pilots are weatherwise, but some are otherwise™



Edited 76 time(s). Last edit at 08/14/2013 11:08AM by Scott Dennstaedt.
Re: Weather analysis for an accident of a TBM-700 near Morristown, NJ
February 19, 2013 12:39PM
The factual report for this accident can be read here as well as the probable cause here. Also, the meteorological report can be found here.

Scott Dennstaedt
CFI & former NWS meteorologist
Administrator of AvWxWorkshops.com
Most pilots are weatherwise, but some are otherwise™



Edited 2 time(s). Last edit at 08/14/2013 11:42AM by Scott Dennstaedt.