The MH-47D Chinook Adverse Weather Cockpit (AWC) is a twin engine, tandem rotor, heavy assault helicopter that has been specifically modified for long range flights. The CH-47D Chinook has been specially modified to perform the special operations mission and has been tested in combat. It is equipped with weather avoidance/search radar; aerial refueling (A/R) probe for in flight refueling; Personnel Locator System (PLS) for finding downed aircrews; Forward Looking Infrared (FLIR); secure voice communications; Fast Rope Insertion Extraction System (FRIES) for insertion of personnel/equipment and extraction of personnel; defensive armament system consisting of 2 M134 machine-guns and one M60D machine-gun; and internal rescue hoist with a 600 pound capacity.
The MH-47D provides long-range penetration, medium assault helicopter support to special operations forces. Depending on the version, it can be ferried 1,100 to 2,000 nautical miles unrefueled. The internal cabin is 9.14 meters long, 2.29 meters wide and 1.98 meters high. While it can carry 2 jeeps or a soft-top HMMWV, the HMMWV doors do not have enough clearance to open. The standard crew seating is 33, which can be increased to 44 with extra seats.
The ability to configure the MH-47D with refueling equipment provides a task force commander increased mission flexibility by providing a highly mobile forward area fuel source. This method delivers fuel to other aviation assets. The so-called "Fat Cow" configuration allows each MH-47D to set up a dual Forward Area Refueling Point (FARP) within 10 minutes of arrival at the refueling location. The system has great versatility, allowing the MH-47D not only the ability to refuel other aircraft, but also if the situation dictated, to refuel itself. In this role up to 2 aircraft up to 60 meters away could be fueled, at 454 liters per minute.
Refueling, however, is inherently dangerous and requires extensive planning and safety precautions. Operational considerations dictate a need for site security to accompany each Fat Cow sortie. With the Forward Area Refueling Equipment (FARE) set up inside the MH-47D, combined with the support personnel required to conduct the refuel operation, limited space was available for security force personnel. Fat Cow mission elements should have enough security to defend against anticipated threat. Infantry can be used as site security during Fat Cow missions, but limit the amount of available fuel for the mission. Inadequate security will degrade the refuel mission of its ability to protect itself long enough to move. In addition, many sites are unusable for MH-47D Fat Cow operations. Sites may be rejected due to excessive slope, uneven terrain, or simply that no open area exists as indicated by the map reconnaissance.
The first MH-47D was initially one of the highly modified CH-47Ds possed by the 160th Aviation Regiment, which had been fitted with a CMS 80 cockpit, a fully coupled flight-control system, a weather radar system and a digital intercom system similar to that used on the B-1B bomber. Between 1984 and 1987, 11 more of the CH-47Ds became MH-47Ds, receiving modifications such as FLIR, M134 "Miniguns," and an aerial refueling probe. The in-flight refueling capability gave the MH-47D unlimited range.
In 1988, the 160th Aviation Regiment began efforts to develop a common cockpit-software architecture for the MH-47D and the MH-60L. In 1989, the architecture was achieved, and it was added to the MH-47Ds, along with an integrated global positioning system and 3 800-gallon internal Robertson auxiliary fuel tanks.
During Operation Just Cause in 1989-1990, special operations MH-47s conducted H-hour assaults to support other elements that were air-landing special operations forces to disrupt enemy responses and seize key facilities. During Operation Desert Storm in 1991, MH-47s conducted infiltration and exfiltration of special operations forces and combat search and rescue of downed pilots.
In the 12 years since 1989, the MH-47Ds received numerous modifications, including CMS 80 cockpit upgrades, embedded global positioning system/inertial navigation units, advanced aircraft-survivability equipment, new engines, and rescue hoists. The MH-47D aircraft remained in service as of 2000, mainly in the Fat Cow role setting up FARPs for other helicopters. The 11 MH-47Ds remained in service due, in part, to MH-47E acquisition cut-backs. Dramatic reductions in MH-47D operations and maintenance costs and improvements in performance were achieved by upgrading the T55 series engines with the incorporation of a full authority digital electronic control (FADEC) into the engine's existing hydromechanical unit. The Engine Air Particle Separator (EAPS) system installed on the engine inlets did a good job of keeping the engines clean and reduced damage due to foreign object ingestion. However, the EAPS prevented the crew from conducting a proper pre-flight of the engine inlet area.
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