N4467D

HISTORY OF FLIGHT

On July 8, 2009, at 1452 eastern daylight time, a Cessna 421C, N4467D, was destroyed after it impacted the waters of the Gulf of Mexico, about 25 nautical miles northwest of Port Richey, Florida. The instrument-rated commercial pilot and 4 passengers were fatally injured. Instrument meteorological conditions prevailed in the area of the accident and an instrument flight rules (IFR) flight plan had been filed for the flight, which departed Collin County Regional Airport (TKI), McKinney, Texas destined for Tampa International Airport (TPA), Tampa Florida. The corporate flight was conducted under 14 Code of Federal Regulations Part 91.

According to voice data provided by the Federal Aviation Administration (FAA), The pilot of indicated that he had reviewed the weather conditions when he called the Houston Automated Flight Service Station to file his IFR flight plan prior to departure. At that time the pilot indicated he was aware of the thunderstorm activity over the Gulf of Mexico and Florida, and that he was anticipating deviating around the weather as necessary.

According to radar and voice data provided by the FAA, just prior to the accident, the pilot had been in communication with the Jacksonville Air Route Traffic Control Center (ARTCC). During the flight the pilot requested and had been provided both weather information along his route of flight and "ride reports" from other aircraft.

At 1446:34, the pilot reported to ARTCC that he was encountering turbulence and requested directions to get out of the turbulence. The pilot was then advised by the controller that if he continued straight ahead for about two minutes, he should be clear of the weather.

At 1446:56 the pilot advised ARTCC that he was experiencing a two thousand foot per minute descent rate. At 1447:02 the controller then asked him if he would like to turn around and go back in the opposite direction, to which the pilot responded that he would.

At 1847:07, the pilot was cleared to reverse course. Sixteen seconds later, the pilot declared an emergency, and advised that the airplane was "upside down". There were no further transmissions from the pilot, and radar contact was lost with the airplane when it descended below the radar coverage area.

PERSONNEL INFORMATION

According to FAA records, the pilot held a commercial pilot certificate with airplane single engine land, airplane multi-engine land, and instrument airplane ratings. His most recent FAA second-class medical certificate was issued on April 23, 2009. He reported 1,940 total hours of flight experience on that date.

AIRCRAFT INFORMATION

According to FAA and maintenance records, the airplane was manufactured in 1979. It was a two engine, pressurized, 7 seat airplane of conventional construction. It was approved for day and night IFR operations and was equipped with weather radar, a Stormscope weather mapping sensor, and an XM satellite receiver which enabled the pilot to receive the XM weather data stream.

It had been modified from its original configuration by RAM Aircraft LP and was equipped with winglets, spoilers, and vortex generators. It was powered by two Continental GTSIO-520-L engines, each producing 375 horsepower. It could cruise at 228 knots, had a range of 1,487 nautical miles, and could operate at altitudes up to 30,000 feet msl.

The airplane's most recent annual inspection was completed on August 18, 2008. The last maintenance action was performed on the airplane on July 6, 2009. At the time of the last maintenance action, the airplane had accrued 4,325.6 total hours of operation.

METEOROLOGICAL INFORMATION

According to the National Weather Service at the time of the accident, an area of IFR conditions existed over southern Georgia into northern Florida generally north of the accident airplane's route of flight. Associated with these conditions was a large area of reduced visibility in moderate to heavy rain. Surrounding that area was an area of marginal visual flight rules (MVFR) conditions over portions of Georgia and northern Florida, and two other areas across central Florida over the eastern and western portions of the state associated with thunderstorms and rain showers.

The National Center for Atmospheric Research (NCAR) Regional Radar Mosaic Chart which was valid for the time of the accident also depicted a band of "intense to extreme" intensity echoes which extended across the Alabama and Florida panhandle into southern Georgia, and was associated with strong to potentially severe thunderstorms. A second east-to-west band of echoes associated with thunderstorms and rain showers also extended from the east to west coast of central Florida into the Gulf of Mexico. This band was characterized as a broken area of strong to intense cells along the southern portion with an extensive area of stratiform precipitation of light to moderate intensity echoes extending northward.

The reported weather at Hernando County Airport (BKV), Brooksville, Florida approximately 47 miles east-north-east of the debris fields, at 1453, one minute after the accident, included: wind, 340 at 9 knots, visibility 1and 3/4 miles in light thunderstorms and rain showers mist, few clouds at 200 feet, broken clouds at 2,600 feet, overcast at 3,400 temperature 24 degrees C, dew point 23 degrees C, altimeter setting of 29.98 inches of mercury, and lightning in the distance, all quadrants.

Four minutes later, the reported weather at BKV, included: wind calm, visibility 1/2 mile in heavy thunderstorms and rain showers, fog, few clouds at 200 feet, scattered clouds at 1,000 feet, overcast at 2,400 feet, temperature 24 degrees C, dewpoint 23 degrees C, altimeter setting of 29.98 inches of mercury, and lightning in the distance, all quadrants

WRECKAGE AND IMPACT INFORMATION

Search and rescue operations were undertaken by the United States Coast Guard (USCG), St. Petersburg Sector, utilizing surface vessels and aircraft. A 2-mile-long by 100-yard-wide debris field was located on the surface of the water at approximately 2000 on the day of the accident.

On July 9, 2009, a second larger debris field was also discovered floating on the surface of the water approximately 4 miles northeast of the first debris field. At 1555, The Safety Board was advised by the USCG that no survivors had been found and that search and rescue operations had been suspended.

Follow on searches by a contractor utilizing side scan sonar were conducted and multiple targets were detected. The search was suspended however, before the targets could be examined by divers, and the wreckage was never recovered.

TESTS AND RESEARCH

The debris fields were located near one of the stronger cells on the southern side of the band of echoes which had been depicted on the NCAR Regional Radar Mosaic Chart.

At the time of the accident, The National Oceanic and Atmospheric Administration (NOAA) operated 159 high-resolution Doppler weather radar sites as part of the next generation radar network (NEXRAD). According to NOAA, these NEXRAD sites were equipped with Weather Surveillance Radar-1988, Doppler (WSR-88D) weather surveillance radar units which emit pulses of energy into the atmosphere at regular intervals. When this energy encounters something (a raindrop, a snowflake, a mountain, etc.), some of the energy is scattered back to the radar dish.

The amount of energy, which was received at the radar dish, was measured in units (decibels) of Z (dBZ). It is a meteorological measure of equivalent reflectivity (Z) of a radar signal reflected off a remote object. The higher the dBZ value the larger the object i.e. large raindrops and hail produce high dBZ values. In general, dBZ values greater than 15 indicate areas where precipitation is reaching the ground. On the other hand, dBZ values less than 15 usually are an indication of very light precipitation which in most cases is evaporating in the atmosphere before it reaches the ground.

The closest WSR-88D was located approximately 43 miles southeast of the debris fields. A review of WSR-88D radar data and satellite imagery by a Safety Board meteorologist revealed that the airplane had been operating through an area of echoes of 20 to 30 dBZ consistent with those associated with moderate rain. Approximately 4 minutes prior to the accident, the airplane then entered an area of echoes of 35 to 40 dBZ associated with heavy rain in convective activity. The airplane next deviated to the south and then southwestward into the stronger and more intense portion of the echoes with reflectivities of 50 dBZ or "extreme" intensity.

Onboard Lightning Detector

The airplane was equipped with an onboard lightning detector which could calculate the direction and severity of lightning by using radio direction-finding techniques together with an analysis of the characteristic frequencies that were emitted by the lightning. Distance was estimated by using signal frequency and attenuation.

Since lightening detectors use attenuation, they sometimes mistakenly indicate a weak lightning strike nearby as a strong one further away, or vice-versa.

Tests of lightning detectors by the National Aeronautics and Space Administration (NASA) also indicated that even with precipitation intensity levels of three and occasionally four (heavy to very heavy) being indicated on radar, a lightning detection system may not activate and that a clear display only indicates the absence of electrical discharges.

Onboard Weather Radar

According to the FAA, The primary use of onboard weather radar is to aid the pilot in avoiding thunderstorms and associated turbulence. The proficient operator manages antenna tilt control to achieve best knowledge of storm height, size, and relative direction of movement.

Airborne weather radar is for avoiding severe weather, not for penetrating it. Whether to fly into an area of radar echoes depends on echo-intensity, spacing between the echoes, aircraft c...