Marine Corps mulling over options for heavy lift helos.

The U.S. Marine Corps CH-53E Super Stallion is among a handful of military helicopters available today that can move and re-supply forces high in the mountains of Afghanistan. Like the lighter Army Chinook, the three-engine, seven-blade 53E never was designed as an air-assault platform, but its payload and range have made it an asset in the Central Asian conflict.

The CH-53E is flying 20 percent more than a year ago, officials said. This has accelerated the need for a service life extension program (SLEP). A Marine Corps/Navy ream currently is formulating a CH-53E SLEP operational requirements document. Depending on the outcome of the ORD, the services may decide to procure new aircraft or begin the SLEP program as early as fiscal 2004. The remanufactured or new-production helicopters would enter the fleet in 2012.

Sikorsky Aircraft delivered 180 CH-53Es to the Marines between 1981 and 1999. The service now has about 165 aircraft in active and reserve squadrons. While the helicopters average 13 years old, the earliest Super Stallions are passing 20 years in service. One was retired early this year.

The current cost of operating the CH-53E is about $10,000 per flight hour. The Marines expect that a new or remanufactured helicopter would be less costly. Meanwhile, the heavy lift requirements of the Marine air-ground task force have grown. The CH-53E was designed to lug howitzers, light armored vehicles, or 16 tons of external cargo from assault ships to the beach over a 50 nautical-mile radius at sea level. But the new Marine Corps doctrine sets a 200 nautical-mile radius. Afghan landing zones at 10,000 feet elevations show that nor all wars are fought under sea-level standard-day conditions.

The CH-53E SLEP (at various times called the CH-53Xor CH-53 modernization) could cur the operations and support costs of the CH-53E by about 25 percent, Marine officials estimated.

Main transmission beams, bulkheads, and vertical pylon components give the existing CH-53E airframe a design life of about 6,000 flight hours. Replacing those items to restore airframe life and increase gross weight effectively would build a new helicopter. The ultimate number of CH-53Es in the SLEP--whether they are remanufactured or new production--is still to be determined.

Should a SLEP contract begin design work in 2004, the first remanufactured CH-53E could fly by 2009. To avert an inventory shortfall before SLEP deliveries build up, improvements may come in stages. The first stage would give the CH-53E structural life improvements, an integrated cockpit and an improved cargo handling system. The second would permit a gross weight increase with more powerful engines and a new main rotor system.

To sustain Marine squadrons, the SLEP could be preceded by new aircraft--equipped with T64-GE-19 engines, a glass cockpit, and a health-and-usage monitoring system.

The design of a new or rebuilt Super Stallion will be determined by trade studies. Several improvements already were requested by former Deputy Commandant for Marine Corps Aviation Lt. Gen. Fred McCorkle. These include a new center fuselage, transition section and tail-boom with structural enhancements that could increase gross weight from 73,500 to 78,500 pounds. The CH-53E never was hardened ballistically for air assaults in "hot" landing zones. A new structure could incorporate armor protection around engines, flight controls and other critical areas.

Performance at High Altitudes

The Marines want their heavy-lift helicopter to haul a 28,000 pound Eight Armored Vehicle over a 100 to 200 nautical-mile radius, taking off at 3,000 feet on a 91.5 degrees F day. Under those conditions, today's CH-53E carries only 7,600 pounds over 200 nautical miles.

High-and-hot performance of the Super Stallion is limited by available engine power. With three General Electric T64-GE-416/416A turboshafts, the 13,000 shaft-horsepower main gearbox of the CH-53E receives only 9,700 shaft-horsepower at 3,000/91.5. While the CH-53E SLEP will probably retain the present transmission with minor reliability/maintainability improvements, it will introduce new engines probably chosen by a competition.

Today's T64-GE-416 engine is rated 4,380 shaft-horsepower at sea level on a standard day and around 3,200 shaft-horsepower high-and-hot. To provide mote power at low cost, GE plans to grow the -419 version of the engine now flying on Navy MH-53E minesweeping helicopters. With hot section components from GE'S modern commercial engines, the T64 growth engine would generate 5,370 shaft-horsepower at sea level on a standard day and 4,728 shaft-horsepower at high density altitudes. If requited, the T64 could be modernized with a full authority digital engine control (FADEC).

Rolls Royce proposes adapting the 6,200 shaft-horsepower AE1107C engine of the Marine MV-22 to the CH-53E SLEP. The engine provides around 5,700 shaft-horsepower high-and-hot, and would give Marine composite squadrons aboard amphibious assault ships a single large turbo-shaft to maintain for two types of aircraft. The AE1107 already has a FADEC and shares its core with the AE2100 turboprop now on Marine KC-130J tankers.

Pratt and Whitney plans to offer a turbo-shaft derivative of its new PW150 turboprop now flying on regional airliners. The 7,000 shaft-horsepower sea -evel engine would fill the CH-53E transmission under high-and-hot conditions.

About 75 percent of the CH-53E SLEP lift improvement will come from the new engines and 25 percent from an advanced main rotor. Sikorsky has suggested an advanced rotor system. New all-composite rotor blades scaled up from those on the S-92 medium lift helicopter would eliminate the titanium spar of the present CH-53E blade, and its maintenance-intensive pressurized blade inspection method, said company officials. A new titanium main rotor head with elastomeric center bearing element could supplant the oil-lubricated rotor-head now on the CH-53E, cutting the number of parts in half.

The CH-53E main rotor hub is the single biggest maintenance cost driver. Others include the main gearbox, rotor blades and swash plate.

The cockpit of today's CH-53E is a high-workload collection of analog gauges made more crowded in recent years by the display for a Raytheon AAQ-16 forward looking infrared (FLIR) sensor. Night-vision goggles, FLIR and various navigation systems already give the 53E a measure of night/adverse weather capability. However, the CH-53E SLEP promises a darabus-integrated avionics suite with multifunction displays to manage aircraft systems and modern communications and navigation avionics. A glass cockpit could help shrink the current instrument panel and improve visibility.

Common avionics is a feature found in other Marine aircraft today. The MV-22 has a Boeing-integrated glass cockpit with Honeywell displays. The modernized AH-1Z attack helicopter and UH-1Y utility helicopter share a common avionics suite integrated by Northrop-Grumman. The new KC-130J ranker has a glass cockpit integrated by Lockheed Martin. Whatever the source and integrator, a new glass cockpit with digital connectivity should give CH-53E crews better situational awareness, officials said. The Marines expect an open SLEP avionics architecture to accommodate future joint-service radios and the so-called TADIL-J datalink.

A CH-53E SLEP, additionally, could, for the first time, provide the Super Stallion with infrared suppressors and an integrated aircraft survivability suite. Improvements are also expected in the internal and external cargo handling systems.

Separately from the Marine Corps CH-53E program, the Navy has yet to decide the future of its MH-53E Sea Dragon minesweepers. Should the Navy elect to continue to perform the airborne mine countermeasures mission with dedicated aircraft, the big Sea Dragons could take advantage of the engine and dynamic improvements used on the Marine heavy lifters.

RELATED ARTICLE: Upgraded chinook: More cargo at higher altitudes

The U.S. Army's CH-47 cargo helicopter has been a useful air mobility asset for U.S. Special Operations Forces and conventional Army units. But the fleet is aging saddling the Army with growing maintenance and operation costs.

For that reason, the Army initiated the CH-47F Improved Cargo Helicopter (ICH) upgrade program, which will add about 20 years to the life of older Chinooks. Although the program is expected to generate savings in operations and maintenance costs, it has been under close scrutiny at the Pentagon, as a result of significant cost overruns (National Defense, June 2002, pg. 14). But the upgrade work will continue, as planned, because other alternatives were deemed too costly.

The office of the defense secretary recently estimated that the CH-47F unit cost will be about $22 million. The Chinook is now expected to remain in the Army inventory until at least 2033, 71 years after the CH-47 first entered service.

Plans call for 300 of the 433 CH-47Ds in the Army inventory to become CH-47Fs. Within that total will be 36 MH-47G Special Operations Aircraft reclaimed from today's MH-47D and -47E fleet, or from standard CH-47Ds. The ultimate number of Chinooks rebuilt for the Army could grow awaiting a Joint Combined Lift replacement around 2025.

The first low-rate initial production CH-47F is scheduled for delivery in 2004.

In May, Boeing delivered the first remanufactured CH-47F Chinook to the U.S. Army. The aircraft, serial number 8002, is one of two prototypes manufactured for the modernization program. Both helicopters began flight and system validation testing in 2001. Aircraft 8002 was scheduled to begin test flights at Fort Rucker, Ala., in late May.

Boeing estimates it takes about a year to turn a D-model Chinook into a CH-47F. The company's Philadelphia plant can upgrade at least four aircraft per month. Current remanufacture plans ramp up from seven improved Chinooks in fiscal 2003 to 27 in fiscal 2009, and conclude with 29 aircraft in 2016.

The Army estimates that this upgrade will cut Chinook operating costs per flight hour from $2,526 for the CH-47D to $1,895 for the CH-47F. Additionally, the CH-47F will haul the Army's heaviest loads at high-density altitudes and share information with other platforms.

Boeing modernized U. S. Army CH-47A's, -B's, and C's to CH-47Ds from 1982 to 1994. When the aircraft reach the end of their 20-year operational life span, structures crack and avionics and other subsystems fail more frequently. Brittle wiring and corroding connectors also cause problems.

In Afghanistan, Chinooks provided the power and range to haul worthwhile payloads at mountain elevations beyond the reach of Army Black Hawks. Army lift requirements have nevertheless outgrown the CH-47D. The 0-Model Chinook was required to carry 15,000 pounds over 30 nautical miles, taking off at 4,000 feet on a 95-degree F day. The Army's Ml 98 howitzer with its crew and equipment weighs around 16,000 pounds, too heavy for today's Chinook to lift under high-and-hot conditions.

Plans for a CH-47 follow-on or CH-47(FO) with four-bladed rotors, new engines and fully integrated avionics emerged soon after Desert Storm, but proved too expensive for the Army budgets. Today's CH-47F recapitalization is therefore not as ambitious as the CH-47D modernization. D-model remanufacture stripped every aircraft to bare structure for totally new wiring and plumbing and replaced transmissions, rotor blades and engines.

Much of the wear and tear on helicopters comes from vibration. By de-tuning the airframe with stiffer structures, the CH-47F remanufacture reduces both vibration and the weight of vibration suppression systems. Since most of the stiffening is up front, the CH-47F replaces the forward third of the fuselage with an entirely new cockpit section. The lower vibration levels demonstrated in EMD promise to reduce O&S costs and improve the reliability of avionics and controls, said Boeing officials.

The rest of the aircraft structure is inspected for cracks and corrosion and repaired as necessary. While CH-47F remanufacture rewires the Chinook, it retains existing fluid lines. The aft rotor pylon of the CH-47F makes teardown and assembly easier, for rapid deployment

Stiffer Structure

Original plans called for the CH-47F to use existing transmissions without changes. The Army has since agreed to overhaul the gearboxes as part of remanufacture. While the 7,500 shaft-horse power transmission of the Chinook is adequate to meet current Army lift requirements, the helicopter needs more high-and-hot engine power, program officials said.

Separate from the recapitalization, the Army is upgrading the Honeywell (formerly Lycoming) 3,750 shaft-horsepower T55-L-71 2 turbo-shafts of the Chinook to 4,867 shaft-horsepower T55-GA-714A standards. The higher sea-level power margins of the improved engine will give the CH-47F enough high-and-hot power to carry a 16,000 pound howitzer with crew 100 nautical miles, three times farther than Army requirements. Despite the added power, gross weight of the CH-47F remains 50,000 pounds for now, equal to that of the CH-47D. Special Operations Chinooks and current export aircraft are about 54,000 pounds.

Up front the CH-47F introduces a glass cockpit that is less sophisticated than those found in some export Chinooks or the one planned for the new UH-60M Black Hawk Boeing integrated the Chinook crew station around Rockwell Collins hardware and software on a MIL-STD 1553B databus.

Each pilot has a control display unit (CDU) in the center console to host the entire system and give crew members access to communications and navigation functions. The CH-47F has dual GPS/INS navigators to drive the digital map and provide vertical speed information.

An improved data modem gives the CH-47F access to orders and situation reports from joint air and ground units via a choice of radios. The communications package includes an ARC-164 UHF AM set with Have Quick II frequency hopping dual ARC-201D VHF FM Sincgars radios, an ARC-186 VHF AM/FM radio and ARC-220 HF radio for over-the-horizon communications.

The CH-47F uses the same aircraft survivability suite available in the CH-47Ds and international Chinooks. The ICH will have provision for a second M130 flare/chaff dispenser, and the databus can accommodate SIRFC and SIIRCM--the Suite of Integrated Radio Frequency Countermeasures and Suite of Integrated Infrared Countermeasures.

Digital electronics in a reduced vibration environment promise higher avionics reliability and lower O&S costs. However, to control costs and moderate the integration challenge, the CH-47F retains the existing electromechanical instruments to display engine parameters. The new cockpit is not as integrated as the Honeywell Avionics Control Management System in Dutch CH-47Ds and International CH-47SDs. It has, for example, a stand-alone radar warning receiver display. Despite its new databus, it has no provision for a forward-looking infrared (FLIR) night vision sensor.

The 160th Special Operations Aviation Regiment already has more capable avionics with the Lockheed Martin Integrated Avionics System in its MH-47Es, and the Rockwell Collins Adverse Weather Cockpit System on its MH-47Ds. The CH-47F remanufacturing line gives the Special Operations Command an opportunity to standardize the aircraft flown by the 160th SOAR.

Notional plans call for six of the seven Lot 1 CH-47Fs to be upgraded to MH-47Gs, with enlarged fuel sponsons, air refueling probes, multi-mode radars, and new common avionics including color multi-function displays. The Rockwell Collins avionics architecture system is meant to standardize MH-47, MH-60, and A/MH-6 avionics software. Boeing will integrate the new avionics suite into the MH-47G cockpit

The CH-47F retains the analog flight control computer of the CH-47D, but a more advanced and supportable digital computer is in the works for Block 2F-model Chinooks.