The Apache Longbow helicopter is designed to conduct precision attacks in adverse weather and on battlefields obscured by smoke, automatically engage multiple targets, and provide fire-and-forget missile capability. The Apache Longbow configuration consists of a modified airframe, a fire control radar, and a new Longbow (radio frequency) Hellfire missile. The Army plans to upgrade the entire fleet of 758 Apache helicopters to the Apache Longbow configuration but outfit only 227 with the radar and a more powerful 701C engine. The remaining 531 non-radar-equipped Apache Longbows will be equipped with the less powerful 701 engine, even though they will be reconfigured to accept the radar and upgraded 701C engine. In its fiscal year 2000-2005 program plan, the Army has proposed a reduction in the number of Apaches that will be converted to the Apache Longbow configuration. The April 1994 Apache Longbow’s operational requirements document (ORD) prescribes performance capabilities required for the system’s survivability and lethality. These capabilities include meeting the vertical flight requirement, carrying the Longbow Hellfire missile, and passing target data when in line of sight and not in the line of sight. For the Apache Longbow, the Army has identified performance objectives (desired capabilities) and performance thresholds (minimum capabilities). The Army designated selected thresholds as key performance parameters. According to the Department of Defense’s (DOD) acquisition guidelines, key performance parameters are those capabilities that are so significant that failure to meet the threshold can be a cause for the program to be reassessed or terminated. The Apache Longbow ORD prescribes that, for survivability in the combat mission configuration, the system is required to achieve a VROC of at least 450 feet per minute at 4,000 feet and 95 degrees Fahrenheit while carrying 4 air-to-air missiles, 8 Hellfire missiles (4 semiactive laser Hellfire missiles and 4 Longbow Hellfire missiles), 320 rounds of 30-millimeter ammunition, and a full fuel load. VROC indicates the helicopter’s ability to climb vertically from a hover position and its ability to conduct lateral maneuvers. Both lateral and vertical acceleration provide the agility a helicopter needs to extricate itself from threatening situations. In October 1994, the Joint Requirements Oversight Council validated the ORD’s VROC requirement of 450 feet per minute as a key performance parameter. The Council also made 12 Longbow Hellfire missiles a key performance parameter, replacing the ORD’s combat mission requirement for 8 Hellfire missiles. In November 1994, the Army directed the Training and Doctrine Command’s Apache Longbow system manager and the Program Executive Officer for Aviation to update the ORD to reflect the changed requirement. The Apache Longbow ORD and contract reflect the VROC requirement but not the revised Hellfire requirement. The ORD describes non-line-of-sight communications capability as a critical system performance objective, but not a key performance parameter, of the Apache Longbow helicopter. The non-line-of-sight radio gives the radar- and non-radar-equipped Apache Longbow helicopters the ability to transfer targeting data when not in direct line of sight. Both the design and use of the fire control radar depend on the ability of the radar-equipped Apache Longbow to utilize terrain and vegetation for concealment, rise above a tree line or hill to acquire target data, return to a concealed position to transfer the target data to another Apache Longbow, and fire the Longbow Hellfire missile. The Army plans to use the ARC-220 radio to meet this requirement. The 227 radar-equipped Apache Longbows will not be able to achieve the combat mission VROC requirement of 450 feet per minute when carrying 12 missiles with a full fuel load. Thus, the system’s survivability will be adversely impacted. The contractor reports that, in the combat mission configuration, the Apache Longbow weighs 16,535 pounds after burning off 1,084 pounds of fuel. At this weight, the contractor reports that the Apache Longbow can achieve a VROC of 895 feet per minute, exceeding the required 450 feet per minute. From Army and contractor records, we identified those items that would have to be added to the helicopter to meet the ORD’s combat mission requirement. When the reported Apache Longbow weight of 16,535 pounds is increased by the fuel burn off weight of 1,084 pounds to meet the ORD’s full fuel load requirement, the helicopter’s weight is 17,619 pounds. When the contractor’s reported weight is increased by the weight associated with meeting the Hellfire missile requirement of 12 instead of 8 (430 pounds), the necessary launcher and pylon to carry them (207 pounds), and a full fuel load (1,084 pounds), we determined that the weight of the Apache Longbow would be about 18,256 pounds. According to Army engineers, an increase in weight of one pound causes a corresponding decrease in VROC of 0.839 feet per minute. With an increase in weight of either 1,084 or 1,721 pounds, the Apache Longbow would be incapable of meeting the validated VROC requirement of 450 feet per minute at 4,000 feet and 95 degrees Fahrenheit. To achieve the validated VROC requirement of 450 feet per minute and carry the required 12 Hellfire missiles, aircraft weight must be reduced. Since the Apache Longbow’s 701C engine is operating at 100-percent maximum-rated power in the combat mission configuration when VROC is measured, no reserve engine power is available. In describing the Apache Longbow’s ability to meet the VROC while carrying the 12 Hellfire missiles, the Army stated, in its November 1995 acquisition program baseline, that the helicopter can only achieve the VROC requirement by reducing weight, such as ordnance and/or fuel load. According to Army officials, reduced VROC performance will decrease the helicopter’s ability to evade enemy fire, thereby decreasing survivability. Also, if the mission ordnance load is reduced to lower weight and, therefore, achieve desired VROC, lethality will be decreased because less ammunition and/or fewer missiles will be available for use against enemy targets. If the mission fuel load is reduced for the same purpose, mission range and/or loiter time will be decreased. On the basis of the Army’s planned system enhancements, the contractor expects the Apache Longbow’s weight to increase by another approximately 1,000 pounds when existing requirements, such as improved avionics equipment, the non-line-of-sight radio, and fixes for systemic problems (including a new transmission and main gear box) are added to the helicopter. Also, based on new requirements, the contractor projects that weight will increase by an additional 500 pounds for items, such as, sensor improvements, a redesigned rotor system, an advanced weapon suite, and improved crew seats. With the additional 1,500 pounds, the Army will be further challenged to find ways to meet the Apache Longbow’s VROC requirements. The Apache Longbow ORD also requires that the 531 non-radar-equipped helicopters have a VROC equal to or greater than the radar-equipped aircraft to ensure that combat effectiveness is maintained. The non-radar-equipped helicopter has a less powerful engine, and the contractor reports that this helicopter has significantly less VROC capability than the radar-equipped helicopter. To improve VROC and corresponding maneuverability on non-radar-equipped aircraft, the Army plans to upgrade the 701 engines on these aircraft to the more powerful 701C engines. According to the Army, this upgrade will cost about $1.1 million per aircraft, or about $600 million for 531 helicopters. This requirement is included in the Army’s future funding plans. The additional power provided by the 701C engines may not provide the lift capability the non-radar-equipped Apache Longbow will need for the combat mission. Removing the radar will decrease weight by about 450 pounds. However, fuel and missile load requirements for the combat mission will increase weight by about 1,721 pounds. The incremental increase of 1,271 pounds would have an adverse impact on the non-radar-equipped Apache Longbow’s already limited VROC performance. At initial operational capability in October 1998, the Apache Longbow will not be able to meet the requirement to transfer target data to other helicopters when out of line of sight, as required. The Army plans to provide this capability through the ARC-220 radio but because of funding and developmental problems, it does not know when this required capability will be available. The ORD requires that all Apache Longbow helicopters be able to transmit, receive, and coordinate battlefield information. The Apache Longbow must interface with existing and planned Army command, control, communications, and intelligence systems. The communications system must support the transfer of mission data from ground units to aircraft, aircraft to aircraft, and aircraft to ground units. This communications capability requires airborne and ground non-line-of-sight communications. As of May 1998, unresolved technical issues, including the amount and severity of electrical interference generated, have affected the radio’s development. The ARC-220 Army project manager did not know when radio delivery would begin. The Army plans to address this and other concerns with additional testing; however, the Army does not currently plan to start testing the ARC-220 radio in the Apache Longbow until fiscal year 2000. According to the ARC-220 project manager, no other radio can provide the non-line-of-sight communications capability for the Apache Longbow. Also, the Army has decided to equip only one-half, or 379, rather than all 758 helicopters with the ARC-220 radio due to changing Army funding priorities. Therefore, 50 percent of the Apache Longbow fleet will be unable to transfer or receive targeting data when out of the line of sight.