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The Hurricane Hunters visit the BVI

In April 2016 the BVI received a visit from the “Hurricane Hunters” the C130J, the newest generation of the C-130 Hercules aircraft belonging to the 53rd Weather Reconnaissance Squadron. The aircraft is capable of operating from rough, dirt strips and is the prime transport for air dropping troops and equipment into hostile areas.

The 53rd Weather Reconnaissance Squadron uses the WC-130J to penetrate tropical storms. These aircraft are not reinforced in any way. The only differences between a WC-130J and a C-130J is the addition of two external fuel tanks (giving them longer range), a radiometer pod on the left wing and the two additional crew pallets in the cargo bay with weather instruments.

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The C-130 operates throughout the U.S. Air Force, serving with Air Mobility Command (stateside based), Air Force Special Operations Command, theater commands, Air National Guard and the Air Force Reserve Command, fulfilling a wide range of operational missions in both peace and war situations. Basic and specialized versions of the aircraft airframe perform a diverse number of roles, including airlift support, Antarctic ice resupply, aeromedical missions, weather reconnaissance, aerial spray missions, fire-fighting duties for the U.S. Forest Service and natural disaster relief missions.

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Using its aft loading ramp and door the C-130 can accommodate a wide variety of oversized cargo, including everything from utility helicopters and six-wheeled armored vehicles to standard palletized cargo and military personnel. In an aerial delivery role, it can airdrop loads up to 42,000 pounds or use its high-flotation landing gear to land and deliver cargo on rough, dirt strips.

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The flexible design of the Hercules enables it to be configured for many different missions, allowing for one aircraft to perform the role of many. Much of the special mission equipment added to the Hercules is removable, allowing the aircraft to revert back to its cargo delivery role if desired. Additionally, the C-130 can be rapidly reconfigured for the various types of cargo such as palletized equipment, floor-loaded material, airdrop platforms, container delivery system bundles, vehicles and personnel or aeromedical evacuation.

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The Airborne Vertical Atmospheric Profiling System (AVAPS) Pallet:

The Airborne Vertical Atmospheric Profiling System (AVAPS) marks a tremendous advance in hurricane reconnaissance data collection aboard the Air Force Reserve’s fleet of WC-130J aircraft. AVAPS is a self-contained atmospheric profiling system, installed in two standard 19-inch racks, that records current atmospheric conditions vertically below the WC-130J aircraft from a deployed dropsonde that transmits data back to the arcraft as it falls to the surface. AVAPS consists of expendable GPS dropsondes, a Dropsonde Telemetry Chassis, high power computer, and a color monitor.

The GPS Dropsonde:
The GPS Sonde is a lightweight instrument package that is launched from the WC-130J aircraft. As it descends from aircraft altitude (5,000 – 38,000 feet) to the surface, at about 2500 feet per minute, it measures and transmits current pressure, temperature, humidity, wind speed and direction, and GPS position information to AVAPS hardware in the aircraft twice each second.

The Sonde also receives GPS navigation signals from at least four GPS satellites, and measures the Doppler shift of each signal. Up to four sondes can be deployed simultaneously. AVAPS receives this data, processes it, then displays the time from launch, raw weather data, number of GPS satellites being tracked, and geopotential altitude for each Sonde deployed.

The raw and processed data are also written to the computer’s internal hard drive. After the drop has ended, the data files can be printed and data can be analyzed by the ASPEN program.

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The ARWO Pallet:

The ARWO pallet consists of a computer system that processes all the atmospheric data it collects from the airplane’s sensors, a radio and satellite control for communication purposes (only data capable), and interphone control and flight deck representations.

The Weatherbird Software:

The Weatherbird computer software enables the ARWO operator to monitor atmospheric conditions, both numerically and graphically, near the WC-130J and transmit this data to monitoring stations on the ground. Atmospheric and aircraft flight data are sampled six times per second at flight level and formulated into ten-second averaged data sets by a signal conditioner. The software then uses the ten-second data to compute numerous higher level meteorological parameters, such as pressure, altitude, temperature, and dew point, all of which can be displayed and stored. The ten-second data is averaged into 30 second averages which is then formulated into data messages, called High Density Observations (HDOBs) each containing 10-minutes worth of information. The HDOBS are automatically sent to the National Hurricane Center (NHC) via satellite communications where they are fed directly into the NHC computers and are instantly available to hurricane forecasters as analysis and forecasting tools.

Finally, the software serves as a storage and transmission facility for data messages. Vertical sounding messages (DROPs) are produced by AVAPS (see below for more information), while horizontal observations (RECCO) and Vortex Data Messages (VDMs) are produced by the Weatherbird software. RECCO messages contain both sensed and subjective data collected by the ARWO at flight level, while VDMs are hurricane eye reports of location and intensity. All messages can be retrieved, edited, and restored by the ARWO and finally sent to the customer via the satellite communication system. Plain language “administrative” messages can also be sent via SATCOM enabling direct and fast communication between the mission ARWO and forecasters at the National Hurricane Center.

The Communication Navigation Identification Unit (CNIU):

Aircraft position and flight level wind information is provided by the CNIU. The main CNIU component is a GPS navigation unit which can pinpoint a position accurately to within one mile after an average 10-hour hurricane reconnaissance mission. This position and wind data is also stored by each controller and is included in the HDOBS messages.

The mission Aerial Reconnaissance Weather Officer (ARWO) can manipulate the stored data in a variety of ways. It can be displayed in various digital formats or graphically depicted in time series or position plots. The speed and flexibility with which data can be viewed aid the ARWO’s analysis and decisions, dramatically improving his ability to maintain control of the mission in the rapidly changing environment of a hurricane.

The Satellite Communication System (SATCOM):

The SATCOM consists of an onboard transceiver and antenna, plus a reciprocating station located on the ground. There are currently two operational ground stations; one at the National Hurricane Center and the other at Keesler AFB, MS. Messages passed are automatically displayed on the respective receiving station’s computer monitor. An acknowledgment of receipt of a message is automatic and is instantaneously relayed to the sending station by the receiving station. This enhances the book keeping process by the ARWO on the aircraft and ensures that none of the critical hurricane reconnaissance data is lost in space.