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DeHavilland Twin Otter (DHC-6)

Twin Otter Flying Over Beach

The DeHavilland Twin Otter (DHC-6) is a highly maneuverable, versatile aircraft which can be flown slowly (80-160 knots/150-300 km/hr) and in tight circles. The Twin Otter is a high-winged, unpressurized, twin-engine turboprop aircraft equipped with color weather radar, radar altimeter, dual GPS/Loran-C navigation systems with scientific data drops, and camera ports in the nose and belly areas. A standard flight crew consists of two NOAA pilots. In support of NOAA or NOAA-related missions, this platform has conducted low-level slow speed aerial surveys of marine mammals, aerial video surveys of coastal erosion, various remote sensing missions, atmospheric air chemistry sampling, and atmospheric eddy flux and concentration gradient assessments.


Type: Engines De Havilland DHC-6 Twin Otter, Series 300
United Aircraft of Canada Limited PT6A-27
Crew: 2 Pilots + 6 Scientists
Ceiling: 12,500 feet (without supplemental cabin oxygen)
25,000 feet(with supplemental cabin oxygen)
Rate of Climb: 1600 feet/minute
Operational Airspeeds: 80-160 knots
Electrical Two 28 VDC 250 ampere starter-generators
Scientific Power: 3 KVA of 115 VAC, 60 Hz and 70 A of 28 VDC
Max. Gross Weight: 12,500 lbs.
Empty Weight: 8,100 lbs.
Useful Load: 4,400 lbs. (fuel, personnel, cargo)
Fuel Load: 2,500 lbs. with additional 1,000 lbs. in optional cabin auxiliary tank (Note: installation of auxiliary tank reduces useful load)
Type Fuel: Jet
Standard Fuel Burn: Normal Cruise Speed - 580 lbs./hr
Fuel Burn for specific mission configuration will be calculated during mission planning and will vary with environmental conditions. Maximum Range and Duration Vary with power setting and fuel tank configuration.
Dimensions (external): Wing Span - 65 ft.
Total Length - 52 ft
Fuselage Height - 9 ft 1 in
Tail Height - 19 ft 6 in
Cabin Doors (removable) - 50 in x 56 in
Baggage Doors (rear) - 35.7 in x 25.7 in
(nose - see diagram)
Dimensions (internal): (Cabin Length - 18 ft 5 in
Cabin Height - 59 in
Cabin Width - 52.5 in (floor) 63.2 in (ceiling)
Useable Volumes Cabin - 384 cu ft
Nose Baggage - 38 cu ft
Aft Baggage - 88 cu ft
Additional Standard Equipment (Cockpit): Weather radar, radar altimeter, dual GPS/Loran-C navigation system, HF radio
Additional Standard Equipment (Cabin): Camera and instrumentation ports GPS data link to cockpit GPS units
Dye marker drop tube

Drawing of DeHavilland Twin Otter
Front View

Drawing of DeHavilland Twin Otter
Left Side View

Twin Otter Mission Profile Information

Auxiliary Fuel Tank Installed
Configuration Airspeed Endurance Range
Normal Cruise 130 kts 6.0 hrs 780 nm
Survey Speed 110 kts 7.0 hrs 785 nm

Auxiliary Fuel Tank Removed
Configuration Airspeed Endurance Range
Normal Cruise 130 kts 4.5 hrs 560 nm
Survey Speed 110 kts 5.0 hrs 565 nm

Note: According to FAA and NOAA AOC regulations, the aircraft must land with 30 minutes fuel reserve in VFR/day conditions, 45 minutes in VFR/night conditions, and 1 hour in IFR conditions. Additionally, endurance is relative to desired airspeed and will be reduced if flight plans include profiles (climbs/descents). Other factors influencing endurance and range include but are not limited to weather, winds aloft, and altitude. Although the auxiliary fuel tank has a maximum capacity of 150 gallons of jet fuel, the ability to carry this quantity if affected by weight limitations.

  • Auxiliary fuel tank is removable.
  • Dye marker drop tube is removable.
  • Instrumentation hatch can be removed for continuous access to belly instrumentation and camera ports.
  • Various camera mounts are available from the NOAA AOC for nose and belly camera ports.

NOAA Air Resources Laboratory

"Mobile Flux Platform"

The NOAA Air Resources Laboratory (ARL) developed modifications to the Twin Otter in order to measure eddy fluxes and concentration gradients through the atmospheric mixed layer. Rates of exchange of several atmospheric properties throughout the lower atmosphere and between the atmosphere and the surface can now be investigated. In addition to the advanced pressure-port system that provides absolute velocity data, the unique nose cone al so accommodates infrared H2O/CO2 analyzers and net radiation sensors. When the Mobile Flux System is fully deployed, the fast response temperature, water vapor, and carbon dioxide sensors in conjunction with the global positioning system, provide routine data on vertical eddy fluxes of temperature, water, and carbon dioxide can be extracted. Other implementations includes air temperature, dew point, pressure, three dimensional winds, and radiation state-variable instruments. The platform can also acquire air chemistry data, such as NO, NOx, Noy, SO2, O3, CO, and reactive hydrocarbons, using a flow-through air inlet system with instruments situated in equipment racks. The acquisition system is computer-based with four display monitors mounted throughout the aircraft allowing in-flight interactions by scientific users.

The Twin Otter provides a stable platform for low level research flights. Instrumentation is calibrated for data acquisition at airspeeds between 100-110 knots. With all of the atmospheric flux and air chemistry equipment on board the aircraft, room for the installation of the internal fuel tank is unavailable. Therefore, the maximum endurance is approximately 4.3 hours.

Further "Mobile Flux Platform" information can be found by visiting the NOAA ARL website at

Drawing of DeHavilland Twin Otter

Drawing of DeHavilland Twin Otter
Cabin Views


Fisheries Survey Platform

The Twin Otter is a safe, stable platform for offshore low level marine animal surveys. In the past, the NOAA Twin Otters have been utilized to assess populations of many species of pinnipeds, cetaceans, fish, and sea turtles. The aircraft is routinely flown at 90-110 knots during survey flights and is highly maneuverable enabling smooth execution of steep turns. HF radios allow for communications when the aircraft is a long distance from the shoreline. While most animal surveys are flown during the day and under visual flight rule conditions (VFR), the aircraft is equipped for flight into instrument meteorological conditions (dual VOR, dual ADF, dual GPS, DME, color weather radar) and icing conditions (pitot heat, prop deice, wing and horizontal stabilizer deicing boots, engine intake deflectors).

An internal fuel tank located in the middle right side of the cabin carries a maximum of 150 gallons of additional fuel (depending on payload) allowing for maximum range and endurance. With a maximum fuel load, only four observers can accompany the aircraft on a mission flight.

When the large convex Plexiglas bubble windows are installed on both sides of the forward end of the cabin, the scientific observer has complete forward, lateral, rear, and downward visibility. Observers can easily view both sides of the transect line, which is a requirement of the line transect survey method. The aft-most side window is removable to facilitate photography. Additionally, a nose camera port and a belly camera port is available for video or still photographic missions. Two smaller ports forward of the belly camera port can be used to mount downward looking instrumentation, such as infrared sensors or light meters. A global positioning system (GPS) data drop is located next to the workstation situated aft of the internal fuel tank. With a suitable laptop computer and software package, time, date, latitude, longitude, speed, heading information and GPS signal strength can be downloaded from the aircraft GPS.

Further information can be obtained from accessing the following websites:,, and

Airborne Oceanographic LIDAR Project

NOAA/NASA Joint Study

NASA Airborne Oceanographic Lidar III mounted over the belly camera port. View through cargo doors on left side of a NOAA Twin Otter.
Picture of the inside of DeHavilland Twin Otter

The NOAA Coastal Services Center and NASA’s Wallops Flight Facility mount an Airborne Oceanographic Lidar III (AOL III) in the Twin Otter. Surveys are conducted along the coast at 500 - 2200 feet above ground. The AOL Fluorosensor package acquires measurements of fluorescence from certain oceanic pigments, which include chlorophyll, and phycoerythrin from marine phytoplankton and chromophoric dissolved organic matter. The AOL package operates two lasers: one laser stimulates fluorescence from chlorophyll and phycoerythrin pigments in phytoplankton while the other laser stimulates fluorescence from specific organic carbon molecules. For each laser pulse, the laser-induced fluorescence spectrum (370 nm to 740 nm spectral band) is collected. Additionally, the fluorosensor collects passive (solar-induced) ocean color radiance data and sea surface temperature. Historically, AOL mission data has had marine and terrestrial applications that include hydrography, oil film thickness measurement, overland terrain mapping, phytoplankton pigment measurement, sea ice thickness estimation, and algorithm development for satellite ocean color sensors.

NASA Airborne Oceanographic Lidar III mounted over the belly camera port. View through cargo doors on left side of a NOAA Twin Otter.

Further information can be obtained from accessing the NOAA Coastal Services Center website at or the NASA Wallops Flight Facility website at

Airborne LIDAR Assessment of Coast Erosion

NOAA/NASA Joint Study

The NOAA Coastal Services Center and NASA’s Wallops Flight Facility mount an Airborne Topographic Mapper (ATM-II). The ATM-II, a scanning LIDAR altimeter, measures topography to an accuracy of ten to twenty centimeters by combining measurements from the laser altimeter (mounted over the belly camera port) and GPS receivers. High resolution topographic maps can be developed using these measurements. Surveys are conducted along the coast at altitudes between 1800 and 2200 feet above ground.

Data from initial and follow-up surveys will be used by NOAA and NASA scientists to assess the effects of major storms and long term erosion patterns. Coastal features, stable areas, and areas vulnerable to flooding, storm surge, etc. can be depicted on color-coded maps. The data obtained from ATM survey flights can be used to detect temporal changes, cliff retreat or erosion, and barrier island washover.

Further information can be obtained from accessing the NOAA Coastal Services Center website or the NASA Wallops Flight Facility website .


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