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The Northrop Grumman (formerly Ryan Aeronautical) RQ-4 Global Hawk (known as Tier II+ during development) is an unmanned aerial vehicle (UAV) used by the United States Air Force as a surveillance aircraft.

In role and design, the Global Hawk is similar to the Lockheed U-2, the venerable 1950s spy plane. It is a theater commander's asset to both provide a broad overview and systematically target surveillance shortfalls. The Global Hawk air vehicle is able to provide high resolution Synthetic Aperture Radar (SAR)—that can penetrate cloud-cover and sandstorms—and Electro-Optical/Infrared (EO/IR) imagery at long range with long loiter times over target areas. It can survey as much as 40,000 square miles (100,000 square kilometers) of terrain a day.

Potential missions for the Global Hawk cover the spectrum of intelligence collection capability to support forces in worldwide peace, crisis, and wartime operations. According to the Air Force, the capabilities of the aircraft will allow more precise targeting of weapons and better protection of forces through superior surveillance capabilities.

The "R" is the Department of Defensemarker designation for reconnaissance; "Q" means unmanned aircraft system. The "4" refers to it being the fourth of a series of purpose-built unmanned aircraft systems.

The Global Hawk costs about $35 million USD (actual per-aircraft costs; with development costs also included, the per-aircraft cost rises to $123.2 million USD each).

Development

Initial development

The first seven aircraft were built under the Advanced Concept Technology Demonstration (ACTD) program, sponsored by DARPA, in order to evaluate the design and its capabilities. Due to world circumstances, the capabilities of the aircraft were in high demand, so the prototype aircraft were operated by the U.S. Air Force in theater in the War in Afghanistan.

In an unusual move, the aircraft entered initial low-rate production concurrently while still in engineering and manufacturing development. Nine production Block 10 aircraft (sometimes referred to as RQ-4A configuration) were produced, two of which were transferred to the US Navy. Two more were sent to Iraqmarker to support operations there. The final Block 10 aircraft was delivered on June 26, 2006.

In order to increase the aircraft's capabilities, the airframe was redesigned, with the nose section and wings being stretched. The changes, with the designation RQ-4 Block 20, allow the aircraft to carry up to 3,000 pounds of internal payload. These changes were introduced with the first Block 20 aircraft, the 17th Global Hawk produced, which was rolled out in a ceremony on August 25, 2006. First flight of the Block 20 from the USAF Plant 42marker in Palmdale, Californiamarker to Edwards Air Force Basemarker took place on March 1, 2007. Developmental testing of Block 20 took place in and 2008. Future Block 30 and 40 aircraft, similar in size to the Block 20, are scheduled for development from 2008 to 2010.

Cost overruns

Program development cost overruns had put the Global Hawk system at risk of cancellation. Per-unit costs in mid-2006 were 25% over baseline estimates, caused by both the need to correct design deficiencies as well as increase the system's capabilities. This caused some concerns about a possible congressional termination of the program if its national security benefits could not be justified. However, in June 2006, the Global Hawk program was restructured. Completion of an operational assessment report by the Air Force was slipped due to manufacturing and development delays from August 2005 to November 2007. The operational assessment report was released in March 2007 and production of the 54 air vehicles planned has been extended by two years to 2015.

United States Navy

The United States Navy took delivery of two of the Block 10 aircraft to be used to evaluate maritime surveillance capabilities, designated N-1. The initial example, Bureau Number 166509, was tested in a naval configuration at Edwards Air Force Base for several months, later ferrying to NAS Patuxent Rivermarker on March 28, 2006 to begin the Global Hawk Maritime Demonstration (GHMD) program. Navy squadron VX-20 was tasked with operating the GHMD system.

In the spring of 2006, the GHMD aircraft took part in a demonstration of the type's ability to conduct maritime drug interdiction surveillance, completing four flights over the Caribbeanmarker and off the coast of Floridamarker, locating and identifying numerous airborne and surface targets.

The GHMD aircraft flew in the Rim of the Pacific (RIMPAC) exercise for the first time in July, 2006. Although RIMPAC operations were in the vicinity of Hawaiimarker, the aircraft was operated from Edwards, requiring flights of approximately each way to the operations area. Four flights were performed, resulting in over 24 hours of persistent maritime surveillance coordinated with USS Abraham Lincolnmarker and USS Bonhomme Richard. As a part of the demonstration program, Global Hawk was tasked with maintenance of maritime situational awareness, contact tracking, and imagery support of various exercise operations. The imagery obtained by Global Hawk was transmitted to NAS Patuxent Rivermarker for processing before being forwarded on to the fleet operations off Hawaii, thus exercising the global nature of this aircraft's operations.

Northrop Grumman entered a version of the RQ-4B in the US Navy's Broad Area Maritime Surveillance (BAMS) UAV contract competition. On 22 April 2008 the announcement was made that the Northrop Grumman RQ-4N had won the bid, with the Navy awarding a contract worth $1.16 billion.

NASA

In December 2007, two Global Hawks were transferred from the U.S. Air Force to NASA's Dryden Flight Research Centermarker at Edwards Air Force Basemarker. Initial research activities beginning in the second quarter of 2009 will support NASA's high-altitude, long-duration Earth science missions. The two Global Hawks were the first and sixth aircraft built under the original DARPA Advanced Concept Technology Demonstration program, and were made available to NASA when the Air Force had no further need for them. Northrop Grumman is an operational partner with NASA and will use the aircraft to demonstrate new technologies and to develop new markets for the aircraft, including possible civilian uses.

NATO

NATO has announced that it expects to have a fleet of up to eight Global Hawks by the year 2012. The aircraft are to be equipped with MP-RTIP radar systems. NATO has budgeted €1 billion for the project, and a letter of intent has been signed, although contracting with Northrop Grumman has not been finalized.

Luftwaffe



The Germanmarker Luftwaffe has ordered a variant of the RQ-4B equipped with European sensors, dubbed EuroHawk. It combines a normal RQ-4B airframe with an EADS reconnaissance payload.

The aircraft is based on the Block 20/30/40 RQ-4B, but will be equipped with EADS' SIGINT package to fulfil Germany's desire to replace their aging Dassault-Breguet Atlantique electronic surveillance aircraft. That sensor package comes in the form of six wing mounted pods, a first for the Global Hawk. The EuroHawk was officially rolled out on October 8, 2009, and is slated to undergo several months of flight testing at Edwards Air Force Basemarker before flying to Germany. A first batch of 5 EuroHawks will be delivered for the Luftwaffe from 2010 on.

The costs for the initial five aircraft are approx. €430 million for the development, and €430 million for the actual procurement.

Potential operators

Australia had considered the purchase of a number of Global Hawk aircraft for maritime and land surveillance. The Global Hawk was to be assessed against the RQ-1 Mariner in trials in 2007. If selected the Global Hawk aircraft would have operated in conjunction with manned P-8A Poseidon aircraft by 10 and 11 Squadrons of the RAAF. This combination, or a similar one, would replace existing AP-3C Orion aircraft in 2018. With the current economic situation, and the delivery schedule pushed back to 2015; the Australian government had decided to cancel the order.

Canadamarker is also a potential customer, looking at the Global Hawk for maritime and land surveillance as either a replacement for its fleet of CP-140 Aurora patrol aircraft or to supplement manned patrols of remote Arctic and maritime environments. Spain has a similar requirement, and has existing contacts with Northrop Grumman.

South Koreamarker's Defense Acquisition Program Administration (DAPA) had expressed interest in acquiring at least four RQ-4B and support equipment by 2011 to increase the intelligence capabilities of the South Korean military after the return of the Wartime Operational Control from the U.S. to ROK, and has allocated approximately USD$19m for evaluation purposes. There is ongoing debate among government officials on whether to take the US offer of Global Hawks or to press on with their domestic UAV development program.

New Zealandmarker's Defence Force is keeping a "watching brief" over Global Hawk, which has the range to conduct surveillance in the Southern Ocean around Antarctica, and in the Pacific Islands. At the moment the acquisition process has moved no further than an expression of interest. Also being looked at are the IAI Heron and a natively-developed hand-thrown drone, the "Kahu".

Design

The RQ-4 is powered by an Allison Rolls-Royce AE3007H turbofan engine with 7,050 lbf (3,200 kgf / 31.4 kN) thrust, and carries a payload of 2,000 pounds (900 kilograms). The fuselage is mostly of conventional aluminum airframe construction, while the wings are made of carbon composite.

The Global Hawk is the first UAV to be certified by the FAA to file its own flight plans and use civilian air corridors in the United Statesmarker with no advance notice. This potentially paves the way for a revolution in unmanned flight, including that of remotely piloted cargo or passenger airliners.

Integrated system

The Global Hawk UAV system comprises an air vehicle segment consisting of air vehicles with sensor payloads, avionics, and data links; a ground segment consisting of a Launch and Recovery Element (LRE), and a Mission Control Element (MCE) with embedded ground communications equipment; a support element; and trained personnel.

The Integrated Sensor Suite (ISS) is provided by Raytheon and consists of a synthetic aperture radar (SAR), electro-optical (EO), and infrared (IR) sensors. Either the EO or the IR sensors can operate simultaneously with the SAR. Each of the sensors provides wide area search imagery and a high-resolution spot mode. The SAR has a ground moving target indicator (GMTI) mode, which can provide a text message providing the moving target's position and velocity. Both SAR and EO/IR imagery are processed onboard the aircraft and transmitted to the MCE as individual frames. The MCE can mosaic these frames into images prior to further dissemination.

Navigation is via inertial navigation with integrated Global Positioning System updates. Global Hawk is intended to operate autonomously and "untethered" using a satellite data link (either Ku or UHF) for sending sensor data from the aircraft to the MCE. The common data link can also be used for direct down link of imagery when the UAV is operating within line-of-sight of users with compatible ground stations.

The ground segment consists of a Mission Control Element (MCE) and Launch and Recovery Element (LRE), provided by Raytheon. The MCE is used for mission planning, command and control, and image processing and dissemination; an LRE for controlling launch and recovery; and associated ground support equipment. (The LRE provides precision differential global positioning system corrections for navigational accuracy during takeoff and landings, while precision coded GPS supplemented with an inertial navigation system is used during mission execution.) By having separable elements in the ground segment, the MCE and the LRE can operate in geographically separate locations, and the MCE can be deployed with the supported command's primary exploitation site. Both ground segments are contained in military shelters with external antennas for line-of-sight and satellite communications with the air vehicles.

Sensor packages

The Global Hawk carries the "Hughes Integrated Surveillance & Reconnaissance (HISAR)" sensor system. HISAR is a lower-cost derivative of the ASARS-2 package that Hughes developed for the Lockheed U-2. HISAR is also fitted in the US Army's RC-7B Airborne Reconnaissance Low Multifunction (ARLM) manned surveillance aircraft, and is being sold on the international market. HISAR integrates a SAR-MTI system, along with an optical and an infrared imager. All three sensors are controlled and their outputs filtered by a common processor. The digital sensor data can be transmitted at up to 50 Mbit/s to a ground station in real time, either directly or through a communications satellite link.

The SAR-MTI system operates in the X-band and provides a number of operational modes:
  • The wide-area MTI mode can detect moving targets within a radius of 62 miles (100 kilometers).
  • The combined SAR-MTI strip mode provides 20 foot (6 meter) resolution over a swath 23 miles (37 kilometers) wide at ranges from 12.4 to 68 miles (20 to 110 kilometers).
  • The SAR spot mode can provide 6 foot (1.8 meter) resolution over 3.8 square miles (10 square kilometers), as well as provide a sea-surveillance function.


The visible and infrared imagers share the same gimballed sensor package, and use common optics, providing a telescopic close-up capability. It can be optionally fitted with an auxiliary SIGINT package. To improve survivability, the Global Hawk is fitted with a Raytheon developed AN/ALR-89 self-protection suite consisting of the AN/AVR-3 Laser Warning System, AN/APR-49 Radar Warning Receiver and a jamming system. An ALE-50 towed decoy also aids in the Global Hawk's deception of enemy air defenses.

In July, 2006, the Air Force began testing segments of the improved Global Hawk Block 30 upgrades in the Benefield Anechoic Facility at Edwards AFBmarker. This version incorporates an extremely sensitive SIGINT processor known as the Advanced Signals Intelligence Payload.

In September 2006, testing began on a new specialty radar system, the Multi-Platform Radar Technology Insertion Program, or MP-RTIP, onboard the Scaled Composites Proteus. Once validated, one Global Hawk will be modified to carry this radar set, and the other, larger variant (known as the Wide-Area Surveillance or WAS sensor) will be installed on the Air Force E-10 MC2A testbed or E-8 Joint STARS aircraft.

Operational history

Air Force Global Hawk flight test evaluations are performed by the 452nd Flight Test Squadron at Edwards AFBmarker. Operational USAF aircraft are flown by the 9th Reconnaissance Wing, 12th Reconnaissance Squadron at Beale Air Force Basemarker. While testing the first two production aircraft, a delay in take off required a late night call to file a flight plan. When FAA received the call to fill in fields on his computer for SOBs (souls on board), his reply was, 'the computer can't take 0'.

Global Hawk ATCD prototypes have been used in the War in Afghanistan and in the Iraq War. While their data-collection capabilities have been praised, the aircraft did suffer a high number of accidents, with two of the aircraft, more than one quarter of the aircraft used in the wars, being lost. According to Australian press reports, the crashes were due to "technical failures or poor maintenance", with a failure rate per hour flown over 100 times higher than the F-16 fighters flown in the same wars. The manufacturer stated that it was unfair to compare the failure rates of a mature design to that of a prototype plane, and pointed to a lack of trained maintenance staff and spare parts.

Records

On March 21, 2001, aircraft number 982003, the third ACTD aircraft produced, set an official world endurance record for UAVs, at 30 hours, 24 minutes and 1 second, flying from Edwards. During the same flight, it set an absolute altitude record of , which was later broken by the NASA Helios Prototype (although the absolute record was broken, the Global Hawk's record still stands in its FAI class category).

On April 24, 2001 a Global Hawk flew non-stop from Edwards in the US to RAAF Base Edinburghmarker in Australia, making history by being the first pilotless aircraft to cross the Pacific Oceanmarker. The flight took 22 hours, and set a world record for absolute distance flown by a UAV, .

Incidents

In March 1999, a Global Hawk inadvertently responded to a termination signal emanating from Nellis Air Force Base after the aircraft lost the Edwards AFB signal.

On December 30, 2001 a Global Hawk crashed in Afghanistan.

On July 10, 2002 a Global Hawk crashed in Pakistanmarker due to an apparent engine failure.

Variants

RQ-4A
Initial production version for the USAF, 59 built.
RQ-4B
Improved version with increased payload, wingspan increased to 130.9 ft (39.8m) and length increased to 47.7 ft (14.5m), due to the increased size and payload the range is reduced to 8,700 nm
RQ-4N
For USN Broad Area Maritime Surveillance role.


Miniature variant

Scaled Compositesmarker and Northrop Grumman are also offering a 50% proportional shrink of the RQ-4A, currently known as the Model 396, as part of the USAF Hunter-Killer program.

Operators



Specifications (RQ-4A)

See also

References

This article contains material that originally came from the web article Unmanned Aerial Vehicles by Greg Goebel, which exists in the Public Domain.

External links




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