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Rockwell Aero Commander (AC-500S)

Picture of Rockewll Aero Commander (AC-500S)
Picture of Rockewll Aero Commander (AC-500S)
The Rockwell Aero Commander (AC-500S) is a versatile and stable high-winged twin piston-engine aircraft that is suitable for a variety of missions. Standard configuration allows for mission equipment and two pilots. However, with the scientific packages removed, seating for five additional passengers may be installed. NOAA's two aero commanders are utilized primarily as aerial survey platforms for visual verification of aeronautical charts, high-resolution aerial photography, and snow water equivalent and soil moisture content measurements. Additionally, the aircraft has been used in biological investigations, such as algal bloom measurements and sea turtle population assessments, and post-hurricane and severe flood damage assessment photography. Picture of Rockewll Aero Commander (AC-500S)
STANDARD AIRCRAFT SPECIFICATIONS

Type: Rockwell AC-500S Aero Commander
Engines: Lycoming IO-540-E1B5 (piston)
Crew: 2 Pilots + 3 Scientists
Ceiling: 12,500 feet (without supplemental cabin oxygen) 18,000 feet (with supplemental cabin oxygen)
Rate of Climb: 1750 feet/minute
Operational Airspeeds: 90-150 knots
Electrical: Two 28 VDC 100 ampere alternators
Max. Gross Weight: 6,750 lbs.
Empty Weight: 5,341 lbs.
(5,621 lbs. including RC-8 Aerial Camera)
(5,756 lbs. including Snow System)
Useful Load: 1,409 lbs. (fuel, personnel, cargo)
(1,129 lbs. with camera installed)
(994 lbs. with Snow System installed)
Fuel Load: 958 lbs. (159 gal)
Type Fuel: 100 LL
Standard Fuel Burn: Normal Cruise Speed - 164 lbs./hr (27.3 gal/hr) Fuel Burn for specific mission configuration will be calculated during mission planning and will vary with environmental conditions.
Maximum Range and Duration: @Normal Cruise - 670 nm @Max. Endurance - 860 nm @Normal Cruise - 4 hr 30 min @Max. Endurance - 6 hr 10 min
Dimensions (external): Wing Span - 49 ft 0.6 in
Total Length - 36 ft 9.7 in
Fuselage Height - 14 ft 3.5 in
Tail Height - 14 ft 8.2 in
Forward Cabin Doors - 3 ft 10 in x 1 ft 11in
Aft Cabin Doors - 3 ft 9 in x 2 ft 4 in
Baggage Doors - 1 ft 11 in x 1 ft 7 in
Dimensions (internal): Cabin Length - 10 ft 7.5 in
Cabin Height - 4 ft 5 in
Cabin Width - 4 ft 4 in
Useable Volumes: Cabin - 177 cu ft Baggage compartment - 32 cu ft
Additional Standard Equipment
Cockpit: Weather radar, radar altimeter, GPS navigation system
Cabin: Camera ports on bottom of fuselage (approx. 1' x 1')
RC-8 aerial camera GPS data port

Picture of Rockewll Aero Commander (AC-500S)The aircraft seating arrangement can accommodate a maximum of five passengers in addition to the two flight crew members. Two single seats can be installed just behind the pilot and copilot seats and a bench seat for three people can be placed at the aft end of the cabin. Passengers have access to external viewing through any of four cabin windows, two on each side of the aircraft fuselage at eye-level. Each of the forward square-shaped cabin windows measures 16 inches wide by 16.375 inches high. The aft cabin windows, which are oblique quadrilateral in shape, measure 16.75 inches wide by 14.5 inches high at the center of the window. Partial viewing is possible through the cockpit forward windows and cockpit brow windows.

Drawing of Rockewll Aero Commander (AC-500S)
Side View

Drawing of Rockewll Aero Commander (AC-500S)
Side View

Drawing of Rockewll Aero Commander (AC-500S)
Front View

Snow Survey Platform (N51RF)

An AC-500S Aero Commander aircraft is used by the National Operational Hydrologic Remote Sensing Center (NOHRSC) to conduct aerial snow survey operations in the snow-affected regions of the United States and Canada. During the snow season (January-April), snow water equivalent measurements are gathered over a number of the 2000+ pre-surveyed flight lines using a gamma radiation detection system mounted in the cabin of the aircraft. In the fall season, the same equipment is used to measure the soil moisture before snowfall is expected, and to measure the background radiation signature of new flight lines. During survey flights, this system is flown at 500 feet above the ground at ground speeds ranging between 100 and 120 knots. Gamma radiation emitted from the earth is attenuated by soil moisture in the upper 20 cm of soil and water mass in the snow cover. Through careful analysis, differences between airborne radiation measurements made over bare ground is compared to that of snow-covered ground. The radiation differences are corrected for airmass attenuation and extraneous gamma contamination from cosmic sources. The airmass correction is calculated using the output from precision temperature, radar altimeter, and pressure sensors mounted on and within the aircraft. Output from the Snow Survey system results in a mean areal snow water equivalent value within +/- one centimeter. Data collected during snow survey missions, including observed ground and weather conditions, are used by the National Weather Service (NWS) and other agencies to forecast river levels and potential flooding events due to snowmelt water runoff. Hydroelectric power interests and other water supply managers also use the data to regulate water storage and delivery.

Further information regarding the snow survey program can be obtained by accessing the National Operational Hydrologic Remote Sensing Center, Office of Hydrology website at http://www.nohrsc.nws.gov.

Aircraft Modifications to N51RF:

  • Customized tail cone with downward looking remote video camera
  • Precision temperature probe mounted on the top of the fuselage
  • Trimble 3000 GPS with output port
  • Radar altimeter with analog output

Snow Survey Platform (N51RF)

Gamma data is collected through the use of a sensor package consisting of 4 downward and 1 upward facing sodium-iodide (NaI) crystals. Gamma radiation entering the crystals is converted into light energy within the crystals. This light energy is then converted to electrical energy in a photomultiplier tube and analyzed digitally by a spectrum analyzer. Energy along this spectrum is counted for the potassium photopeak between 1.36 and 1.56 MeV, the thallium photopeak at 2.41 to 2.81 MeV, and for the entire spectrum (gross counts) between 0.41 and 3.0 MeV. These counts are then fed into the Airborne Gamma Data Acquisition Software (AGDAS) to determine snow-water equivalent or soil-moisture values.

The sensor package currently in use is the RSX-5 detector package from Radiation Solutions, Inc. in Toronto, Ontario, CAN. The system can be monitored through the use of RadAssist, which gives the status of the gamma spectrum, as well as GPS and tuning data.

Besides being affected by water in the snowpack and in the upper 20 cm of soil, gamma radiation attenuation is also affected by the air mass between the sensor and the ground. For this reason, the detector requires a radar altitude (radalt) input to determine actual distance from the ground, along with a manual temperature input, and an automated pressure input to determine the air density between the sensor and the ground.

Also used by the data acquisition system is the background data file (BG.dat), which is updated each year and contains background data for every flight line, as well as updated soil moisture values for lines that were flown for soil moisture prior to that snow season.

Multi-Purpose Survey Platform (N47RF)

Aero Commander N47RF is configured to conduct a variety of remote sensing missions. The aircraft has been modified with an 18-inch diameter, belly-mounted camera hatch. This hatch has a hydraulic door which can be opened and closed in flight. When closed, the door seals tightly to protect any instrumentation mounted in the hatch, and to provide a quieter cabin environment. When open, the door swings out approximately 160 degrees to provide an unobstructed view of the earth below. Using different mounts, a variety of sensors can be installed above the “hole” to provide remote sensing data. Additionally, the relatively large diameter of the opening can, in some cases, allow for the simultaneous mounting of several complimentary sensors. The aircraft cabin has a 28v DC scientific power drop and a standard equipment rack to house data collection computers, video monitors, GPS systems, or any other electronic support equipment.

This aircraft was acquired in 1982 to conduct visual and photographic surveys of aeronautical charts. In 2000, the FAA assumed responsibility for these surveys. However, the photographic component of this mission is still performed by N47RF. This mission involves the aerial photography of air traffic obstructions such as towers, stacks, and buildings. Two pilots perform the mission with one flying the aircraft and the other operating the RC-8 aerial camera system. The RC-8 is capable of taking a series of high-resolution 9-inch x 9-inch photographs with a pre-selected overlap. These photo series are then used to extract height and location information for each obstruction. In addition to obstruction photography, the RC-8 can and has been used for post-disaster photography to document the damage caused by hurricanes, floods, fires, etc.

Besides the RC-8 camera system, the aircraft has also been flown with numerous other sensor systems including hyperspectral imagers, infrared.video cameras, and digital still cameras. These systems have been utilized to detect red tides, measure the health of kelp forests and coral reefs, and to study the effects of wind and current on the oceans surface.

When not employing remote sensors, the aircraft is an outstanding visual survey platform as well. With the high-wing design pilots are afforded very good visibility. In addition, forward, rearward, and downward visibility is improved by two bubble windows installed in the forward cabin area. The enhanced visibility, as well as the Aero Commander's ability to fly low at slow airspeeds while remaining highly maneuverable, makes this aircraft a capable tool for survey or patrol duty. Past projects include Right Whales surveys off the New England coast, Turtle Surveys off the Mid-Atlantic coast, and fish surveys along the Gulf Coast.

Click here for the Digital Snow Survey Movie

 

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