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Gulfstream Jet Prop Commander (AC690A)
The Gulfstream Jet Prop Commander 1000 (AC-695A) is a stable
high-wing, pressurized, twin-engine turboprop aircraft that is suitable
for a variety of missions. Standard configuration allows for mission
equipment, two pilots and one observer. However, the aircraft can be
configured for two scientists/observers and mission equipment in the
cabin. NOAAs AC-695A Jet Prop Commander is typically utilized by the
National Weather Service (NWS) National Operational Hydrologic Remote
Sensing Center (NOHRSC).
The AC-695A jet prop 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 (Oct May), 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. 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 trace
elements of potassium, uranium and thorium radioisotopes in the upper 20 cm
of soil is attenuated by soil moisture 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. Airmass correction is accomplished
using output from precision 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 cm. Information collected
during snow survey missions, along with photographic data, is used by the
National Weather Service (NWS), River Forecasting Centers (RFCs) and other
agencies to forecast river levels, water flow, and potential flooding events
due to snowmelt water runoff.
STANDARD AIRCRAFT SPECIFICATIONS
Type: |
Jet Prop Commander AC-695A |
Engines: |
Garrett TPE-331-10 (turboprop) 800 HP/each |
Crew: |
2 Pilots and 1 Observer (as needed) |
Ceiling: |
35,000 feet (pressurized) |
Rate of Climb: |
2,800 feet/minute |
Operational Airspeeds: |
120-250 knots |
Electrical: |
Two 30 volt 300 ampere starter-generators, Two 24 volt lead acid batteries |
Scientific Power: |
115V AC, 60 Hz |
Max. Gross Weight: |
11,250 lbs Empty Weight: 7,300 lbs |
Useful Load: |
3,950 lbs (fuel, personnel, cargo) Fuel Load 3,175 lbs |
Type Fuel: |
Jet A
Standard Fuel Burn |
Maximum Cruise Speed: |
600 lbs/hr Normal Cruise Speed – 500 lbs/hr
Fuel Burn varies with mission configuration and environmental conditions. |
Range: |
(max. cruise) - 1750 nm Range (normal cruise) - 1950 nm |
Duration: |
(max. cruise) - 5 hr Duration (normal cruise) - 6 hr |
Max Cruise Range: |
(w/reserves) - 1500 nm |
Normal Cruise Range: |
(w/reserves) – 1700 nm |
Dimensions Wing Span: |
52 ft Total Length – 43 ft |
External |
Fuselage Height: |
5 ft 7 in Tail Height – 14 ft 11.5 in |
Cabin Doors: |
47 in x 26 in |
Baggage Doors: |
31.25 in x 19.75 in |
Internal |
Cabin Length: |
17 ft 5 in |
Cabin Height: |
4 ft 9 in |
Cabin Width: |
4 ft 2 in |
Useable Volumes Cabin: |
278 cu ft |
Baggage Compartment: |
46 cu ft |
Additional Standard Equipment
Cockpit |
Meggitt Magic (Meggitt Advanced Generation Integrated Cockpit) System with all digital Primary Flight Display, Navigation Display, Engine Display Unit,
and Air Data Attitude Heading Reference System; Terrain Awareness and Warning System (TAWS), Traffic Alert/Collision Avoidance System (TCAS), Radar, real-time weather data capable Bendix/King 850 Multi-Function Display and a 7-inch VGA compatible mission monitor wired to the cabin mission panel. |
Cabin |
Mission panel for A/C power, RS232 outputs for pressure altitude and radar altimeter, keyboard/mouse and monitor connections to cockpit display.
Aircraft is equipped with lavatory. |
Airborne Snow Measurements Help Forecast Flooding and Water Supply
Snow is a significant element in the United States. The devastating
snowmelt flood of 1997 on the Minnesota River and Red
River of the North caused damage in excess of $4.0 billion
and constituted the most expensive natural disaster,
on a per capita basis, in U.S. history. The economic
impact of snow on the farming, hydroelectric power,
and recreation industries alone as been estimated to
be $18.9 billion annually. Clearly, snow is a critical
component in the nations infrastructure.
Consequently, the National Operational Hydrologic Remote Sensing Center
(NOHRSC) in the U.S. National Weather Service (NWS)
and the Aircraft Operations Center (AOC) in the Office
of Marine and Aviation Operations (OMAO) of the National
Oceanic and Atmospheric Administration (NOAA) has maintained
an Airborne Gamma Radiation Snow Survey Program across
the country for over 20 years. Snow survey aircraft
are used to make near real-time, reliable, airborne
snow water equivalent measurements across the country
during the winter. The airborne snow water equivalent
data are used by the NWS Hydrologic Services Program
when issuing spring snow melt flood outlooks, water
supply outlooks, and river and flood forecasts for the
nation.
NOAA Corps Officers and pilots based at AOC use the survey
aircraft to make measurements of natural terrestrial
gamma radiation emitted from the potassium, thorium,
and uranium radioisotopes in the upper 20 cm of soil.
A network of 2170 operational flight lines has been
established covering portions of 31 states (including
Alaska) and 8 Canadian provinces. A one-time background
measurement of natural terrestrial radiation, with no
snow, is used to calibrate each flight line that is
typically 15-20 km long and 300 m wide. Water mass in
the snowpack attenuates, or blocks, the terrestrial
radiation. Consequently, it is possible to make a subsequent
airborne radiation measurement over a calibrated flight
line, with a snowpack, and infer the snow water equivalent
on the ground with a root mean square error of 0.81
cm in agricultural environments, 2.31 cm in forested
environments, and 3.50 cm in montane environments.
The NOHRSC uses a piston-powered, twin-engine, cabin-class,
Aero Commander (AC500S) in the Upper Midwest and in
the East and a turboprop, twin-engine, cabin-class Jet Prop
Commander (AC695A) in the West and in Alaska to make
simultaneous airborne snow water equivalent measurements
across the country almost continuously from early January
through mid-April. During heavy snow years in the West,
airborne data collection can extend into May and early
June to assess the high elevation snowpack remaining
in the alpine and above the established ground-based
snow water equivalent measurements systems where the
snowpack has melted out. During operational airborne
snow surveys, the radiation data are processed in the
aircraft in real-time and the snow water equivalent
estimates are telemetered up to three times daily from
each aircraft to the NOHRSC office in Minneapolis. Immediately
upon receipt at the NOHRSC, the data are automatically
processed and formatted, sent to the NWS satellite broadcast
network, and received by each of the NWS field offices
in less than 5 minutes of transmission from each survey
aircraft.
More information about NOAA aircraft can be found at NOAA's Aircraft Operations Center.
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