Jane's International Defense Review
August 2002
Pg. 52

U.S. Army Approach Decision Point On Future Of Comanche And Apache

By Bill Sweetman

A crucial decision is imminent for the future of the U.S. Army's attack helicopter force. The U.S. Army, Sikorsky and Boeing are completing plans for a total overhaul of the development program for the RAH-66 Comanche attack and reconnaissance helicopter. It calls for doubling the engineering and manufacturing development (EMD) budget envisaged two years ago when the current EMD contract was issued. Today, even program officials concede that the current EMD program - which was, itself, the fifth restructuring of a project that started in 1983 - would probably have been a technical failure.

The restructuring has been approved by the army but, in late June, awaited the verdict of both the Joint Requirements Oversight Committee, which will assess how well the Comanche meets cross-service needs, and the Defense Acquisition Board, which will measure the importance and cost of the Comanche against other major projects. Underlying the decision process is the recognized need for 'transformational' change in the way the US Army deploys and fights. There is no real doubt that the Comanche will be canceled if the senior Pentagon leadership rejects the restructured program.

This will have an enormous impact because the army's entire armed helicopter plan is based on the Comanche. The army plans to buy more than 1,200 of the new helicopters, and has cut back planned purchases of its current attack helicopter - the Boeing AH-64D Apache Longbow - to fund the new aircraft.

Comanche program history

The RAH-66 Comanche started as the LHX (Light Helicopter Experimental) project in 1983, with the goal of developing scout-attack and utility variants to replace the AH-1 Cobra, UH-1 Huey, OH-58 Kiowa and other aircraft. The program was narrowed down to a scout-attack helicopter in 1987, and the Sikorsky-Boeing team was selected to perform a demonstration/validation program in April 1991. The first of two YRAH-66 Comanche demonstrators made its first flight in January 1996, but the start of EMD was repeatedly delayed, for both technical and budgetary reasons; primarily, the U.S. Army regarded the AH-64D as a higher priority and could not fund both programs in parallel.

By the time the EMD contract was finally awarded, in June 2000, the army was facing problems with an aging fleet of helicopters. For this and other reasons, the army and its contractors signed an EMD contract with a short, demanding schedule, which skipped over some test stages that are normally considered crucial. The Pentagon's Directorate of Operational Test & Evaluation (DOT&E) and Congress' General Accounting Office (GAO) were highly critical of the EMD plans in separate reports issued in early 2001. "It is highly unlikely that the service can deliver the expected system performance within the current budget and schedule," the DOT&E commented. The GAO pointed to excessive risk with the Comanche's offensive avionics and its mission equipment package (MEP), and to unresolved issues with weight, and observed that the army planned to launch low-rate initial production (LRIP) just six months before the design would be frozen.

While the GAO earned a reputation for cautious and critical reports (some would call them nitpicking), it would appear that Congressional investigators were accurate in their assessment of the Comanche project. Deputy Program Director Mike Blake, who joined the program in early 2001, remarks that he and other incoming program managers recognized that there were a number of risk areas in the project. In particular, the original program did not include a full-scale systems integration laboratory (SIL), a test facility which includes sensors, processors and displays. "Software went straight to flight test," remarks Blake. "It was a huge risk." The plan also called for "10 major software drops" in a seven-year period - allowing little or no time to test, analyze and fix problems before the next revision of the software was issued to the flight-test aircraft.

In June 2001, Blake notes, the Comanche program managers "looked at the program and decided that we had a real executability issue." The industrial team members assembled a 'graybeard panel' of independent experts: one assessment was that the MEP development plan was "an all-red condition" - that is, every element embodied a high risk of failure - and that the overall chance of MEP success under the June 2000 contract was 23%. The Comanche team has now reorganized. In 1999, it formed a joint program office at the army's aviation headquarters in Huntsville, Alabama, supervising individual contractor offices in Stratford, Connecticut (Sikorsky) and Philadelphia (Boeing). Late last year, the Huntsville and Philadelphia offices were closed and a single program office was opened at Stratford. On the government side, the Comanche program is being closely monitored by the new Assistant Secretary of the Army for Acquisition, Logistics and Technology, Claude Bolton - a 30-year US Air Force (USAF) veteran who played important management roles in the F-22, B-2, Advanced Cruise Missile and other stealth projects. "We have a window of opportunity - that's this year," Bolton said in a recent interview with Bloomberg News. "Either we are on track at the end of the year or we are looking for something else to do: I could terminate the program."

EMD proposal

The revamped management team was due to submit a new EMD proposal on 15 July. The fundamental change is that the start of LRIP slips from 2005 to 2007. The money saved by delaying LRIP is moved into EMD - an additional US$3.4 billion, on top of the original US$3.2 billion budget. The new program acknowledges the fact that the initial operational capability (IOC) criteria in the original EMD contract were unusual, to say the least: the army planned to declare IOC in late 2006, but the first-unit-equipped date was two years later, at the end of 2008. The IOC unit "was not meant to go to combat," says Blake. Under the revised plan, the Comanche is due to reach initial training capability (ITC) in 2006, and the first combat unit will be equipped in September 2009. The army and the contractors plan to recoup much of the additional time and money spent on EMD by increasing the full production rate, reached after 2012, from 60 to 96 aircraft per month. This is expected to save most of the added EMD funding. If the army stays within the current total planned cost for the Comanche program, it will be 126 aircraft short of its 1,207-aircraft goal, but it will have the option of adding more funds at the end of the program to buy the rest of the aircraft. The additional EMD money and time will be used for work that was deferred to the LRIP stage under the previous program. Roughly half the funds, according to Blake, will be used to support development of the MEP. A complete SIL or 'hot-bench' will be constructed, and the software release schedule will become more realistic. MEP software will also include 'Level 4' control for unmanned aerial vehicles (UAVs), allowing the Comanche crew to take direct control of the navigation and sensors of a UAV. The EMD increase will also pay for engineering and test efforts that address the Comanche's vertical rate of climb (VROC) problems, including weight reductions and propulsion and aerodynamic improvements.

The new EMD program will use fewer aircraft (nine versus 13) because the longer schedule allows each aircraft to fly more test hours before IOC. The first EMD aircraft will be completed in late 2004 and should make its first flight in March 2005. The EMD aircraft conform to the ITC configuration. The airframe and propulsion system should meet the definitive Comanche standard, with the uprated Rolls-Royce/Honeywell T800-LHT-802 engine and complete low-observable (LO) treatments. However, the ITC aircraft will carry no weapons except the General Dynamics/Giat turreted gun system. Operational requirements

The EMD aircraft will be followed by 198 LRIP aircraft in the Block 1 configuration, which will be delivered over five years from July 2008. The Block 1 "meets 90% of the operational requirements document," says Blake. It will carry Hellfire missiles, a fire-control radar and satellite communications (satcom) equipment.

Full-rate production deliveries are due to start in August 2013 with the Block 2 configuration. This will include the External Fuel and Armament Management System, carrying extra weapons and fuel-weight improvements; and further software enhancements. It should also carry an air-to-air missile (AAM), provided the current army-versus-Congress dispute over the Thales SMS Starstreak has been resolved by 2013. However, Blake notes, the new 'spiral' development program means that Block 2 is not yet completely defined, and need not be defined until much later in the decade, so that the details of Block 2 can reflect emerging technology, changing user requirements, and lessons from building and testing the ITC and Block 1 configurations. Comanche supporters continue to argue that the helicopter is unique, mainly because of its combination of stealth and integrated avionics. More than any other helicopter, Comanche has been designed for LO from the outset. The difference between a fixed-wing stealth aircraft and an LO helicopter stems from differences in the environment and the threat, and consequently in the importance of different signatures. While radar is dominant for a fixed-wing aircraft, noise will often be the first indicator of an approaching helicopter, and low-altitude threats use infrared (IR) tracking and homing more than radar. A helicopter uses terrain to mask itself from ground-based radar, and airborne radars have to contend with strong ground clutter.

Acoustic stealth has two elements: the reduction of total noise level and the elimination of distinctive sound patterns. The Comanche has a five-blade rotor, increasing the frequency of blade-to-blade noises. Drooped, swept blade tips have been evaluated to reduce noise. The directional control fan in the tail has eight blades with shrouded tips, eliminating interaction between the wakes of the main and the tail rotor.

The Boeing 360 demonstrator of the late 1980s - which was used to evaluate some LO technologies in support of the Boeing-Sikorsky LHX proposal - exploited its high-speed rotor design to reduce noise. A high-speed rotor needs to have a low stalling speed at the root (so that the retreating blade can produce lift), and this means that it is theoretically possible to fly with reduced rotor rpm at moderate speeds (in the region of 170km/h), further reducing noise. It is not known whether this 'sneak mode' is used on the RAH-66: Blake says he is "not well versed" on any such technique. Comanche incorporates an elaborate IR suppression system. Exhaust gases are piped to linear nozzle arrays, pointed downwards, located in vertical ejector ducts on each side of the tailboom. The high-speed exhaust creates a pressure drop in the duct, drawing ambient-temperature downwash from the rotors through the duct inlets in the upper surface of the tailboom. The result is a very small difference between the exhaust and the ambient air temperature.

Radar cross-section (RCS) is reduced by tilting all the airframe surfaces away from the vertical - including the tail, which has an asymmetric cant angle - and by incorporating a retractable landing gear and internal weapons. The Comanche carries missiles on weapon-carrying doors in the side of the fuselage, and the turreted gun rotates through 180º to stow in a fairing beneath the nose. Flush air inlets, a convoluted inlet particle separator and the exhaust system conceal the engines from radar. "One of the biggest challenges" in the program, according to Blake, has been the development of shrouds for the rotor head, which conceal the complex machinery of the head from radar without hampering access for maintenance. The first Comanche prototype flew with a number of rotorhead designs, comprising root cuffs and pyramidical fairings around the mast, but a definitive design was selected late last year and has not been flight-tested.

'Stealthy' blades

The main rotor and FanTail blades of the production aircraft will also be shaped and treated to reduce RCS. At one point in the long development program, there was a possibility that Comanches would use untreated blades in peacetime and be fitted with low-RCS blades for combat operations, but it is now the intention to fit all aircraft with 'stealthy' blades. The Hexcel company provides 'special-process honeycomb' materials for the Comanche program, possibly for use in the rotor blades.

The design of a stealthy helicopter is described as "at least a thousand times more time-consuming" than a fixed-wing aircraft, "because the rotating blades, both the main rotor and the tail rotor, must be modeled in thousands of positions,"according to one Sikorsky statement. Sikorsky has developed in-house codes to perform RCS predictions for the Comanche, and installed an SGI Origin 2000 computer server in February 2000 to support this work. The computer has 128 processors and two terabytes of storage. Sikorsky now claims that "our level of efficiency and productivity in stealth calculations is unequalled in the airframe industry."

A full-scale RCS model built by MicroCraft has been tested at Boeing's outdoor RCS range at Boardman, Oregon. (Located in the northern part of the state, 270km east of Portland, the Boardman range has been a well-kept secret for some years. It uses a rail-mounted mobile shelter over the main model pylon, similar to the well-regarded McDonnell Douglas range at Grey Butte, California.) Both partial and full-scale tests have been carried out.

Airframe advances

The EMD Comanche airframe will be "80%" different from the prototypes, according to Blake. One reason is that the helicopter's weight increased during development, partly because of the incorporation of extra equipment such as the radar, to the point where its ability to meet the army's 500ft/min VROC requirement wasin doubt. The EMD aircraft has a larger-diameter rotor than the prototypes, together with greater power. The first Comanche prototype flew with the 843kW T800-LHT-801 engine in June 2001, with 17% more power than the original T800-LHT-800, and the baseline engine for the production engine is the 895kW T800-LHT-802. The new engine is expected to deliver the extra power without prejudice to its 6,000h design life. The other visible change to the design during prototype flying, the adoption of an H-shaped tail to reduce vibration, will be reflected in the EMD design.

Because of the changes between the prototype and EMD designs, the prototypes are of limited use to the EMD program. The first aircraft, which was used for envelope expansion and concluded its testing with the H-tail and aerodynamically representative rotor-mounted radome, made its last flight in January 2002 after 318 flights and 387h. The second Comanche returned to the flight-test program in late May, with prototype mission computer cluster and new cockpit displays. By September, it is expected to be performing an initial flight demonstration of the Night-Vision Pilotage System, and it will fly some 15 hours per month through October. The other element of the electro-optical sensor system(EOSS), the Electro-Optical Target Acquisition and Designation Sensor, has undergone preliminary tests on a Black Hawk helicopter. The EOSS, developed by Lockheed Martin, uses similar technology to the improved optronics being developed for the Apache. Other aspects of the Comanche MEP, however, are new. Harris is providing many key components of the MEP, and is replacing the military-unique components originally planned for the Comanche with commercial-type technology. The MEP is linked together by two optical networks. The High-Speed Data Bus, running at 80Mb/sec, links the main avionics subsystems. Point-to-point Image Data Distribution Networks, running at 1Gb/sec, link the sensors to the processors and feed image data to the cockpit displays. Harris is also providing memory storage devices, based on commercial PCMCIA memory cards and using MPEG compression codes to store video imagery. Also from Harris are the flat-panel displays, based on ruggedized commercial glass, and the digital map system. Northrop Grumman provides the mission computer cluster for the Comanche, along with the target acquisition system software (TASS). Hosted on the mission computer, TASS includes an automated target tracker and will eventually include aided target detection and classification as well as a target threat manager. Northrop Grumman also produces the fire-control radar, in a joint venture with Lockheed Martin. The radar is based on the Apache Longbow's APG-78, but features an active electronically scanned array (AESA): a brassboard AESA was demonstrated at Baltimore and Yuma in early 2000. All Comanches will be able to carry radar, but it is expected that only one third of the aircraft in the field will use the system in service, using datalinks to transfer targeting data to other Comanches in the formation.

Rockwell Collins' Kaiser Electronics division is developing the Helmet Integrated Display Sighting System (HIDSS), which has been in EMD since passing its preliminary design review in late 2000. The HIDSS is a two-piece system that attaches to a standard aviator helmet; the optical and tracking systems make up an Aircraft Retained Unit which remains with the aircraft at all times. The binocular display covers a 35x52º field of view, and the imagery is generated by small commercial-type 1,280x1,024-pixel AMLCDs produced by Kopin, with a Kaiser backlight.

ITT Avionics is the integrating subcontractor for the Comanche's self-defense suite. It will be based on the ITT/BAE Systems ALQ-211(V)3 radar warning receiver, a variant of the AN/ALQ-211 Suite of Integrated RF Countermeasures (SIRFC) under development for the Apache. Additionally, Goodrich is providing a laser warning system and BAE Systems is providing a point chemical detector. The first suite is due to be delivered in the second quarter of 2003.

The Comanche's communications, navigation and identification suite is one area where design work is being augmented with new funding. The army intends to equip the Comanche with a satcom datalink to provide a real-time non-line-of-sight to other aircraft and commanders. The Comanche program is working with the Joint Strike Fighter office to produce a low-cost, LO-compatible satcom antenna, which will be located above the tail, but is ready to develop a Comanche-specific satcom antenna if it is needed.

Revolutionary vehicle

The Comanche's combination of speed, stealth and advanced avionics makes it a potentially revolutionary vehicle. However, it is also early in its development. Two prototypes have flown less than 500h between them. No weapons have been fired and only a small part of the MEP has been flown on the Comanche. This is one reason why Boeing is lobbying Congress and the army to take actions that will maintain its ability to produce and support the army's in-service attack helicopter, the veteran AH-64 Apache.

Apache deliveries