TH-57 Sea Ranger
The TH-57 is the sole platform for primary helicopter flight training for student aviators (USN, USMC, USCG) and foreign military pilots. The TH-57 aircraft is the military version of the commercial Model 206 Jet Ranger helicopter manufactured by Bell Helicopter Textron, Inc. The JetRanger was initially designed to compete in a U.S. Army light observation helicopter competition. Bell lost that competition but the 206 was commercially successful. The primary mission of TH-57 is to train student naval aviators in the fundamentals of helicopter flight for their transition to operational fleet aircraft in the U. S. Navy, U. S. Marine Corps, and selected international armed forces. Although primarily used for training, these aircraft are also used for photo, chase, and utility missions. The aircraft is powered by one Allison Gas Turbine 250-C20J turboshaft engine downrated to 317 shaft horsepower.
The TH-57 is a land-based, skid-configured utility type helicopter designed to land and take off from reasonably level terrain. A Rolls-Royce 250-C20J turboshaft engine powers the main rotor, which is used for lift and thrust, and the tail rotor, which is used to counteract torque and provide yaw control. The maximum takeoff gross weight is 3200 pounds. The maximum forward airspeed at sea level on a standard day is 130 kts, maximum sideward airspeed is 25kts, and maximum rearward airspeed is 15 kts.
The forward/cabin section is primarily constructed of aluminumhoneycomb covered with either fiberglass or aluminum skin. This type construction providesan excellent weight-to-strength ratio and also helps soundproof the cabin area.
The skid type landing gear consists of two aluminum alloy curved cross tubes, two aluminum skid tubes, and a formed steel tail skid. The two curved cross tubes are mounted to the bottom of the forward section by four strap assemblies. The skid tubes have a forward portion curved upward for sliding landings, tow rings for ground towing, and replaceable skid shoes to absorb the wear caused by normal ground contact. Provisions are made for mounting ground handling wheels on the skid tube just forward of the aft cross tube. Also considered part of the landing gear is the formed steel tail skid. This skid is mounted to the base of the vertical fin and protects the tail rotor from ground contact due to a tail lowlanding. Furthermore, the tail skid is curved upward to prevent it from embedding in the ground during rearward flight. The tail skid is stressed for loads of 200 pounds downward or 400 pounds upward.
The cowling section streamlines airflow and consists of theforward, induction, engine, and aft fairings. The forward fairing is made of aluminumhoneycomb with a fiberglass skin. This fairing reduces sound and vibrations, but primarilystreamlines the airflow around the flight controls and transmission. The induction fairing ismade of fiberglass to provide weight savings and allow formed compound curves to channel airto the engine. The engine cowling is made of heavy alloyed aluminum and permits access tothe engine and engine parts. Finally, we have the aft fairing, which is made of aluminumhoneycomb with a fiberglass skin. The aft fairing streamlines the airflow around the engine oiltank and cooler.
The tail boom is mounted to the rear of the forward section, via amounting pad and four bolts. With the exception of the first ten inches, the tail boom is a very strong and lightweight full monocoque structure of aluminum alloy. The main purpose of the tail boom is to provide an extended support to mount the tail rotor. Other functions include supporting the horizontal stabilizer, vertical fin section, tail rotor drive shaft, and 90º gearbox. The horizontal stabilizer is mounted approximately at the midpoint of the tail boom and it is made with a negative camber. This negative camber creates a download on the tail boom, which enables the aircraft to fly atnear level attitude during cruise flight.
The vertical fin is a semimonocoque construction made of aluminum honeycomband aluminum skin that provides directional stability and reduced tail rotor loads at cruise airspeed. This is accomplished by mounting the fin with a 5.5º offset from the longitudinalaxis. This offset creates a horizontal lift component that assists in countering torque. (The greater the airspeed, the greater the lift).
The cargo hook consists of a frame and hook assembly with electrical and manualrelease. The cargo hook assembly has a structural weight capacity of 1500 pounds and canbe mounted on the new B and C models only. The frame attaches to three mounting points under the aircraft. These mounting points arefirmly attached to the main structural frame of the aircraft. The entire assembly is mounted so that weight lifted by the cargo hook is lifted in line with the main rotor mast. This minimizes changes in the aircraft center of gravity caused by picking up an external load. The cargo hook is structurally limited to 1500 pounds; but, that is not necessarily the maximum weight the helicopter can lift, it may be much less. Extreme caution and planning must be exercised any time an external cargo lift is planned, due to aircraft limitations.
The TH-57 engine is an internal combustion gas turbine engine featuring a “free” power turbine. The engine consists of a combination axial-centrifugal compressor, a single “can”-type combustor, a turbine assembly which incorporates a two-stage power turbine and exhaust collector, and an accessory gearbox which incorporates a gas producer gear train and a power turbine gear train. Rolls-Royce 250-C20J engine is a 420 SHP engine. 317 SHP is usable iftorque limits are maintained (100% TQ) due to power train limitations.
Helicopter Training Squadron EIGHT (HT-8), the Navy's oldest helicopter training squadron, is based aboard Naval Air Station Whiting Field, Milton, Florida. The TH-57 Sea Ranger provide advanced (IFR) training to several hundred aviation students a year at Whiting Field at Milton, Florida. In January 1986, the TH-57B model replaced the TH-57A, an aircraft flown by the squadron for seventeen years. HT-8 utilized both B and C models of the Bell TH-57 Sea Ranger.
TH-57 aircraft was procured as a commercial derivative aircraft certified under FAA Type Certificate. Throughout its' life, the aircraft has been commercially supported using COTS/NDI components and a combination of Navy and FAA processes, procedures and certifications to support airworthiness. Aircraft modification efforts are "turnkey" projects (non-recurring engineering, procurement, installation, test and certification) implemented as part of competitively awarded maintenance contracts.
The USN TH-57 fleet in the year 2000 consisted of 119 total aircraft which operated in two (2) separate configurations, the TH-57B and TH-57C. The Chief of Naval Air Training operates a total of 117 TH-57 A/C ( 45 TH-57B and 72 TH-57C). The CNATRA TH-57B/C aircraft provide Primary/Instrument Helicopter pilot training for Student Naval Aviators (SNAs) at NAS Whiting Field, FL. Two TH-57C A/C are operated by the Rotary Wing Aircraft Test Directorate at NAS Patuxent River, MD. These two aircraft support various test projects at the Naval Air Warfare Center. All Navy TH-57 A/C are commercially maintained and supported under a NAVAIRSYSCOM Contractor Logistics Support (CLS) Contract, N00019- 99-D-1625. Raytheon Aerospace Services (RAS) of Madison, MS was the incumbent contractor and commenced full performance in October 2000.
To remain a viable and effective training platform that meets the training requirements of a digital helicopter fleet, the TH-57 cockpit is in need of modernization. The TH-57 must keep pace with the T-6 primary trainer (digital cockpit) and the rapidly changing fleet helicopter pilot training requirements, i.e., integrated digital avionics equipment and skills, and night vision (NVIS) operations. Due to current TH-57 cockpit limitations, digital cockpit skills and NVIS training are performed in higher cost fleet replacement squadron (FRS) aircraft. Integral to the cockpit modernization effort, the TH-57 also requires energy attenuating seats to protect aircrews in the event of hard landings, and a torque and temperature exceedence warning system that will dramatically decrease transmission over-torques and engine over-temperatures that are frequently encountered in the training environment.
CNATRA will be replacing the TH-57B/C training aircraft and simulators with a “glass” cockpit TH-57D aircraft and simulators. On 30 March 2007 NAVAIR formally announced contract award to L3 Communications for the upgrade of 128 TH-57B and TH-57C helos to the TH-57D common standard. The upgrade include: Common digital cockpits centered around 2 MFD's; Full NVG integration; Collective shaker for TOT and Torque limit warning; Airbags for cockpit and cabin; and SIMULA energy absorbing/stroking crew seats. Conversion of airframes was set to begin in 2008.
This modernization effort capitalizes on technology improvements by increasing aircrew survivability and situational awareness while providing a fleet representative digital cockpit configuration. Obsolescence upgrades are to replace avionics purchased in 1981 through 1985, when the TH-57B and TH-57C aircraft were originally purchased.
The TH-57D Sea Ranger will replace the TH- 57B/C as Naval Aviation’s single rotary-wing and tilt-rotor aircraft training platform. Future upgrades will include a digital cockpit and passenger protection to enhance training and safety to match more closely the capabilities of Navy and Marine Corps fleet helicopter and tilt-rotor platforms.
As of 2011 the total number of TH-57 aircraft was 126.
|Join the GlobalSecurity.org mailing list|