N1085AMooney M20M · 1989

On September 17, 2012, about 1400 central daylight time, a Mooney M20M, N1085A, was substantially damaged when it impacted terrain in Crane Hill, Alabama. The private pilot and the passenger were fatally injured. Instrument meteorological conditions (IMC) prevailed, and the airplane was operating on an instrument flight rules flight plan from Destin-Fort Walton Beach Airport (DTS), Destin, Florida, to Sumner County Regional Airport (M33), Gallatin, Tennessee. The personal flight was conducted under the provisions of 14 Code of Federal Regulations Part 91.

According to air traffic control information provided by the Federal Aviation Administration (FAA), the airplane departed DTS at 1245, and was subsequently issued a heading of 330 degrees and a climb to 10,000 feet.

At 1247, the pilot contacted the next sector controller, who issued an advisory for weather in the airplane's flight path.

At 1253, the pilot was told to switch to Jacksonville Center and to expect vectors around a weather cell from the receiving controller.

At 1254, the pilot made contact with the next controller and reported climbing from 7,000 to 10,000 feet. The controller advised the pilot of "extreme" precipitation, and asked his intentions. The pilot stated that he was looking at "ADS-B" (Automatic Dependent Surveillance-Broadcast) weather, described what he saw, and told the controller his plans.

At 1255, the controller advised the pilot to maintain 13,000 feet, and approved deviations left or right of course, proceed direct to destination when able.

At 1300, the controller asked the pilot to state his flight conditions, which the pilot responded were cloudy and smooth, with light rain becoming heavy, and that the ride was a "little bit bouncy."

At 1303, the controller broadcast on frequency that information on convective SIGMETS was available.

At 1306, the controller instructed the pilot to contact Atlanta Center, which the pilot did.

At 1317, while the airplane was at 13,000 feet, the pilot asked if there were any reports of icing ahead, around 15,000 feet. The center controller responded that there were no reports of icing, "but quite a bit of deviation, quite a bit of clouds and precipitation in front of you." The pilot requested 15,000 feet "to see if I can see things better," which was approved by the controller.

At 1325, the pilot was told to contact the center's next sector controller, and upon doing so, that controller advised him of moderate to extreme precipitation for about the next 90 miles along the route of flight. The pilot subsequently stated that, in looking at the "a-s-d-n" [ADS-B], he needed to deviate about "three five eight degrees for several miles and probably head back north again." The controller approved 10 degrees' right and left deviation, proceed direct to M33 when able; and the pilot said that he was turning to 358 degrees.

At 1334, the controller advised the pilot of moderate to extreme precipitation at his 12 o'clock position, most off to his right, about 12 miles ahead. The pilot requested another 10 degrees' deviation to the left, and the controller approved deviations left and right, and direct to M33 when able.

At 1336, the pilot advised the controller that he was turning the airplane to 320 degrees, which the controller acknowledged.

At 1354, the controller issued the pilot a radio frequency change, to which the pilot responded, "Unable, we're battling some pretty bad (end of transmission.)"

Plotted radar data indicated that, at 1357:39, the airplane was northbound, at 15,300 feet. By 1358:11, the airplane had turned about 90 degrees to the right (east) and had descended to 14,600 feet. By 1358:20, the airplane had turned about another 90 degrees to the right (south), and descended to 14,100 feet. After making a sharp left turn, the airplane climbed to 15,500 feet by 1358:34. It then made another sharp left turn, and began to descend (northwest).

At 1359:02 the controller contacted the pilot, who responded, at 1359:06, with "mayday."

At 1359:13, the pilot stated, "may (unintelligible) eight five alpha mayday mayday." There were no further transmissions from the airplane.

Plotted radar data indicated that the airplane had descended to 13,200 feet at 1359.03, and after another right turn (north), 10,000 feet at 1359:25. By 1359:34, the airplane had descended to 7,900 feet, and by 1359:44, to 5,300 feet, for a calculated descent rate in excess of 15,000 feet per minute. There were two additional position plots leading north-northwest toward the accident site; however, there were no additional attitude readouts.

At 1401, in discussion with another controller, the handling controller stated, "he declared, he said mayday on the frequency and he won't respond to me; he got into that weather and he started losing altitude."

A witness stated that at the time of the accident, it was raining "like crazy," but with no thunder. He heard an engine noise; it "sounded like he had power, then [he] heard a 'thud.'" When the witness arrived at the accident site, the airplane's cabin was on fire.

The pilot, age 61, held a private pilot certificate with airplane single engine land and instrument airplane ratings. The pilot's logbook was not recovered; however, on his latest FAA third class medical application, dated November 1, 2010, he indicated 1,000 hours of flight time and 50 hours in make and model.

During the most recent as well as previous examinations, the pilot failed color vision testing, specifically noted in 1998 as being unable to distinguish between red and green. On July 14, 1998, the pilot was issued a Statement of Demonstrated Ability (SODA) for defective color vision after passing a signal light test.

During the latest examination, no other significant concerns were reported by the airman and no other significant issues were identified by the aviation medical examiner. The pilot did not report taking any medications.

The airplane was manufactured in 1989 and was powered by a Lycoming TIO-540 series engine. The latest annual inspection was completed on April 4, 2012, at 1,590 total hours.

Weather, recorded at Walker County Airport-Bevill Field (JFX), Jasper, Alabama, 11 nautical miles to the west-southwest of the accident site, at 1355, included wind from 170 degrees true at 3 knots, visibility 8 statute miles, rain, a few clouds at 2,500 feet above ground level (agl), no temperature or dew point listed, an altimeter setting of 29.82 inches Hg, and distant lightning east and southwest.

- Flight Briefs -

According to transcripts, at 1009, the pilot contacted a Lockheed Martin FAA-contracted flight service station for a weather briefing. During the briefing, the briefer advised of a line of thunderstorms and another area of rain with lower IMC, and an additional line of thunderstorms tracking toward the pilot's destination. The briefer also noted a convective SIGMET with small clusters of convection moving north, and from the Alabama-Tennessee border to the destination was a large area of embedded convective activity that didn't look like was going to dissipate anytime soon.

The briefer then provided some suggested routing, but noted that because the flight wasn't leaving for an hour, the temperature would get warmer, and the convective area would expand in coverage and intensity.

The pilot then asked about icing because the airplane would be at 13,000 feet and it was not approved for known icing. The briefer advised that there was an AIRMET out for icing between 13,000 and 25,000 feet, but did not indicate the area covered.

At 1225, the pilot contacted Lockheed Martin again, and with a different briefer, filed a flight plan to depart DTS at 1245, direct to M33, at 13,000 feet. Expected flight time was 2 hours and onboard fuel was 3 hours.

The briefer subsequently asked the pilot if he wanted him to go over "any adverse weather conditions or anything at all," and the pilot brought up the terminal forecast for 2 hours later at Nashville. The briefer provided the latest information he had, for 1300, which included rain showers and thunderstorms in the vicinity, ceiling 500 feet broken, and cumulonimbus clouds. The briefer also noted an area of thunderstorms "moving toward your route of flight," and IFR conditions from northern Alabama to the destination.

- ADS-B and FIS-B -

According to the FAA Aeronautical Information Manual (AIM), ADS-B is "a surveillance system in which an aircraft or vehicle to be detected is fitted with cooperative equipment in the form of a data link transmitter." FIS-B (Flight Information Service – Broadcast) is a "ground broadcast service provided through ADS-B… [that] provides pilots and flight crews of properly equipped aircraft with a cockpit display of certain aviation weather and aeronautical information."

The all-encompassing term "ADS-B" is often used when referring to the FIS-B (weather reporting) portion of ADS-B.

- Weather Study Findings -

According to an NTSB Weather Study for this accident, there was a low-pressure center at the central-Louisiana coast, with a stationary front extending north and then north-eastward into extreme northern Alabama. Another low-pressure center was noted in extreme northern Alabama, north of the accident location.

A North American Mesoscale (NAM) model sounding for the accident location at 1300 indicated that the lowest 1,000 feet of the atmosphere was unstable, with the rest of the atmosphere below about 14,000 being conditionally unstable. The NAM model sounding identified the freezing level as about 13,300 feet.

Calculations made by the RAwindsonde OBservation Program (RAOB) did not identify any levels of significant turbulence, however it did note the potential for light (and some moderate) rime icing between 14,000 and 25,000 feet.

A vertical radar cross section that began at 1359 showed the airplane in level flight in "moderate" reflectivity (with reflectivity defined as "the sum of all backscattering cross-sections," and which could be liquid or frozen precipitation), before it entered a heavier level of "moderate" reflectivity. The airplane reversed course and began a descent into "moderate to heavy" reflectivity, before briefly climbing, then rapidly descending to the ground.

The Study also compared the ground-based National Oceanic and Atmospheric Administration (NOAA) radar imagery depicted at specific times surrounding the time of the accident, with the expected FIS-B depictions displayed in the cockpit. Although the NOAA data also served as the original source for the FIS-B depictions, the FIS-B depictions were time-delayed by further processing, which then resulted in "significant differences in depiction of hazardous reflectivity values" between actual conditions and what was seen in the cockpit.

In the FIS-B product, the airplane was depicted as being clear of moderate or greater reflectivity values as it made turns to the northeast, east, then southeast. However, the radar imagery surrounding those times indicated that the airplane would have been "in very close proximity to heavy values of reflectivity."

The airplane was manufactured in 1989 and was powered by a Lycoming TIO-540 series engine. The latest annual inspection was completed on April 4, 2012, at 1,590 total hours.

The airplane first impacted rolling pastureland in the vicinity of 33 degrees, 58.58 minutes north latitude, 087 degrees, 07.04 west longitude, at an elevation of about 560 feet.

A ground imprint of the airplane's tail commenced about 5 feet beyond an undamaged 5-foot fence post. The ground imprint was consistent with the airplane having impacted the ground flat and upright, with the landing gear up. Airplane fragments were located along an approximately 225-foot debris path, heading about 010 degrees magnetic, with the cabin area and still-attached engine located near the end of the debris path. Although vegetation was pushed over in many spots along the debris path, there was a lack of ground scaring between the first ground impact and where the cabin came to rest.

Both wings and the tail section were separated from the airplane and were not burned, and there were no soot streaks on any fuselage components to indicate an in-flight fire. The aft portion of the main fuselage behind the passenger seats was unburned and crushed downward. The roof and sidewalls of the cabin area were missing, with the rest of the cabin charred forward of the supplemental oxygen bottle that was located just behind the aft cabin bulkhead. The oxygen bottle, mounted horizontally with the cap pointed forward, was also charred in the cap area.

All flight control surfaces were accounted for at the accident scene; however, due to the extensive fracturing of the airplane and subsequent fire, flight control continuity could not be confirmed.

One propeller blade was found separated from the hub at the initial impact point, and the hub, with the two remaining propeller blades, was found separated from the engine about 75 feet beyond the first blade. One propeller blade exhibited extensive curling and bending, the other two blades exhibited torsional bending, and all blades had leading edge burnishing and chordwise scratching.

The engine could not be examined due to extensive fire and impact damage; however, the starter ring exhibited rotational fracturing.

No recording devices were found in the wreckage.

An NTSB Safety Alert, "In-Cockpit NEXRAD Mosaic Imagery" states that the actual age of NEXRAD data, such as that utilized in ADS-B FIS-B, "can differ significantly from the age indicated by in-cockpit displays, and in extreme cases, by up to 15 to 20 minutes."

It further notes, "Even small time differences between the age indicator [on the cockpit display] and actual conditions can be important for safety of flight, especially when considering fast-moving weather hazards, quickly developing weather scenarios, and/or fast moving aircraft….The in-cockpit NEXRAD display depicts where the weather was, not where it is."

AIM states:

"FIS aviation weather products (e.g. graphical ground-based radar precipitation depictions) are not appropriate for tactical avoidance of severe weather such as negotiating a path through a weather hazard area. FIS supports strategic weather decision making such as route selection to avoid a weather hazard area in its entirety. The misuse of information beyond its applicability may place the pilot and aircraft in jeopardy."

An autopsy was conducted on the pilot at the Alabama Department of Forensic Sciences, Huntsville, Alabama. Cause of death was listed as "blunt force injuries."

Toxicological testing was subsequently performed at the FAA Civil Aeronautical Medical Institute. Results included bupropion, citalopram and N-Desmethylcitalopram detected in muscle and kidney.

According to the National Institute of Health online reference, bupropion and citalopram are antidepressants. Additional online research revealed that Desmethylcitalopram is an active metabolite of citalopram.