The CH-47D was the result of June 1976 contract for a modernized Chinook. The Army recognized that that the Chinook fleet was rapidly reaching the end of its useful life and signed a contract with Boeing to significantly improve and update the CH-47. Three airframes, CH-47A, CH-47B, and a CH-47C, were stripped down to their basic airframes and then rebuilt with improved systems to provide three CH-47D prototypes. The first CH-47D was rolled out in March of 1979 and the aircraft became operational with the 101st Airborne Division in 1984. A total of 472 CH-47A, B, and C model Chinooks were converted to CH-47D's.
Improvements included upgraded power plants, rotor transmissions, integral lubrication and cooling for the transmission systems, and fiberglass rotor blades. Other improvements included a redesigned cockpit to reduce pilot workload, redundant and improved electrical systems, modularized hydraulic systems, an advanced flight control system, and improved avionics. The Chinook has two tandem three-bladed counter-rotating fiberglass rotors. The CH-47D is powered by two Allied Signal Engines T55-L-712 3750 shp turboshaft engines and has a maximun speed of 163 mph (142 knots). The CH-47D carrys twice the load of a CH-47A and has improved performance. The CH-47D can operate at night and in nearly all weather conditions. The CH-47D is equipped with an air-to-air refueling probe. The Chinook can accommodate a wide variety of internal payloads, including vehicles, artillery pieces, 33 to 44 troops, or 24 litters plus two medical attendants. The Chinook can be equipped with two door mounting M60D 7.62mm machine guns on the M24 armament subsystem and a ramp mounting M60D using the M41 armament subsystem. The "D" model can carry up to 26,000 pounds externally. The CH-47D has three cargo hooks: a center (main) hook and two additional hooks fore and aft of the main hook.
In the Cockpit, the Pilots seat in the CH-47 is on the right, and the Copilots is on the left. The Pilot in Command generally sits in the left seat (There is more room over there). The minimum crew required to fly this helicopter is two t pilots (excluding staff aviators wherein a senior instructor pilot shall be seated in a seat in such a way that there is continuous and full access to the flight controls), and a flight engineer.
The maximum gross weight of the CH-47D is 50,000 pounds. Typical weight of the Chinook helicopter is 32,000 pounds with a full load of fuel. The typical range of the Chinook flying at 120 Knots Indicated Airspeed (KIAS), or 136 Miles Per Hour (MPH), is 300 nautical miles. A typical mission profile would include a gross weight of 45,000 pounds, fuel consumption of 2,400 pounds per hour (roughly 358 gallons), and 6,000 pounds (roughly 895 gallons) of fuel available at takeoff. Gross weight is the empty aircraft weight, plus fuel weight, plus cargo (internal or external). The duration of a typical Chinook mission is approximately 2 hours and 30 minutes.
At engine start, for a typical Chinook mission, the aircraft has approximately 1,068 gallons (6,600 pounds) of fuel on board. On the mission, the helicopter will consume approximately 940 gallons, or 6,300 pounds of fuel. At 2 bucks a gallon for jet juice, that's $1,880.00 a flight just for the fuel.
The Fatcow is a CH-47D with the Extended Range Fuel System [ERFS] II system located in the cargo bay. The configuration consists of three or four fuel tanks attached to a refueling system. The system contains 2,400 gallons of JP4/8 excluding the CH-47 internal fuel load of 1050 gals. The Fatcow can set up a 1, 2, 3, or 4 point system using HTARS. The fuel cells must be crash-worthy and self sealing up to 50 caliber hits.
The advantages of the Fat Cow (CH-47) FARE are given below.
- The CH-47 is an instant FARP. Once the CH-47 is on the ground, the system can be ready for refueling within 10 minutes.
- The system can be displaced quickly. When refueling operations are completed, the FARP is packed up, the CH-47 takes off, and the site is cleared within minutes.
- The Fat Cow is useful for special operations.
The disadvantages of the Fat Cow are given below.
- The ERFS tanks are airworthy when installed, operated, and maintained as described in TM 55-1560-307- 13&P. With this configuration, however, fuel can leak into the cabin and a catastrophic incident can occur in the event of a hard landing or an accident. When the non-crashworthy ERFS tanks are installed, the potential for fires during a crash increases.
- The armaments of the CH-47 provide limited protection. Therefore, advance planning is required when reconnaissance and/or attack elements are used to escort the CH-47 with Fat Cow installed.
- The aircraft should be shut down and blades secured to prevent safety hazards. The rotor wash from the CH- 47 presents a safety hazard to smaller aircraft.
- The CH-47 burns a tremendous amount of fuel; this must be planned for logistically.
- The signature of the CH-47 makes it vulnerable to detection and attack.
- Use of the Fat Cow diverts valuable aviation assets from other missions. It may be more advantageous to per- form the refuel mission with other refueling systems.
During Desert Storm "the CH-47D was often the only mode of transportation to shift large numbers of personnel, equipment, and supplies rapidly over the vast area in which US forces operated. The cargo capacity and speed provided commanders and logisticians a capability unequalled by any Army in the world." (Army Aviation in Operation Desert Storm, 1991) During the ground phase, the flanking maneuver executed by the XVIII Airborne Corps was planned with the CH-47D as the keystone. Forward Operating Base Cobra was deliberately positioned to accommodate the combat radius of a fully loaded CH-47D. Cobra was initially secured by an air assault of the 101st's 2nd Infantry Brigade. This air assault, consisting of 5000 soldiers, was accomplished by a total of 126 Blackhawks and 60 Chinooks. By the end of the first day the CH-47Ds had lifted 131,000 gallons of fuel along with pallets of combat-configured ammunition for the next day's fight. Forty separate refueling and rearming points were active in FOB Cobra in less than two hours.
During peacekeeping operations in Bosnia, a Chinook company (A company, 5th Battalion, 159th Aviation Regiment) of 16 aircraft flew 2,222 hours, carried 3,348 passengers, and transported over 3.2 million pounds of cargo over a six month period. These numbers equate to carrying 112 infantry platoons, 545 HMMWVs, or 201 M198 Howitzers. The most publicized mission was assisting the 502d Engineer Company build a float bridge across the flooded Sava River allowing the 1st Armored Division to cross into Bosnia. On 29 and 30 December 1995, Big Windy lifted bridge bays and dropped them into the Sava River so the engineers could quickly assemble the bridge. When the Sava River flood washed away the engineer's tentage and personal equipment, Big Windy quickly resupplied the engineers so they could continue their vital mission. Additionally, a key early mission in support of NATO was the recovery of Admiral Smith's aircraft. The Blackhawk had performed a precautionary landing for what was later found to be a transmission seizure. A CH-47D sling-loaded the Blackhawk back to the Intermediate Staging Base (ISB). Big Windy began redeploying to Giebelstadt on 14 June 1996. One platoon of six CH-47Ds remained in Hungary throughout 1997.
The Army announced August 9, 1999 that it had grounded the Chinook helicopter fleet following the discovery of cracked transmission gears during an aircraft overhaul. The U.S. Army Program Executive Office, Aviation at Redstone Arsenal, Ala. and the Boeing Company in Philadelphia were working with aviation units in a records search to locate all gears of the suspect type and design. Army leaders took this action as a prudent measure to ensure the safety of soldiers. No accidents or mishaps had been attributed to these gears. The Program Executive Office for Aviation, with Boeing and the Army Aviation and Missile Command were also investigating the condition of all similarly designed transmission gears. The most plausible cause of the problem was poor grinding of the gear's spherical bearing raceway during manufacture. Improper grinding is a critical flaw because it could produce surface cracks and potential gear fractures. Such cracks and fractures could cause the rotor blades to come out of phase, mesh with each other, lock the transmissions, and potentially lead to a crash.
As of 2000 the Army Guard and Reserve requirement for CH-47 aircraft was 64, with 51 on-hand. Six CH-47 aircraft are designated to be transferred to the USAR as a result of TAA 05 Force Structure actions. The USAR purchased one aircraft with National Guard and Reserve Equipment Appropriation (NGREA) funds with an anticipated delivery date in 2001. However, the USAR still required six aircraft.
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