Modified business aircraft can often satisfy military needs
From AEW to command and control, civil sector OEMs provide COTS solutions for government roles.
Based on Hawker Beechcraft's King Air 350/350ER, the MC12W Liberty was procured to fulfill the ISR role for the USAF.
Before the Jayhawk, the US Air Force bought another COTS light business jet—the Learjet 35A—for the operational support transport role as the C21. Commonly providing high speed transport for Air Force commanders, key federal officials, members of Congress and time-sensitive cargo, more than 70 C21s were delivered between early 1984 and the following year.
Since then, the Learjet 30 series has fulfilled several notable COTS roles, including electronic warfare, target towing and antisubmarine warfare.
The flexibility of the Learjet's design and its subsequent success as a COTS aircraft is unsurprising, as it traces much of its roots to a Swiss-designed fighter, the prototype FFA P16.
Another derivative of the original Learjet design—the Bombardier Learjet 60—has found a niche with FAA, which operates 6 of the type for flight checking navigational facilities.
Very few purpose-built military aircraft can match the unrefueled distances offered by today's large COTS long-range business jets.
Just as FAA has found the Learjet 60 ideal for the flight check/inspection role, the agency also makes use of larger Bombardier types, notably the Challenger and Global Express. FAA operates 5 Challenger 601-3Rs and 1 Challenger 604, all based at OKC (Oklahoma City OK). In addition, FAA operates a Global Express as part of its diverse ACY (Atlantic City NJ)-based research and development fleet.
More recently, other Bombardier Global Express aircraft are sporting subdued military colors and large fairings that house complex battlefield and ground surveillance radar systems. These are the Royal Air Force's 5 Sentinel R1s, which serve in the airborne stand-off radar (ASTOR) role for the United Kingdom's Ministry of Defence.
In 1999, only 3 years after the first flight of the Global Express, Raytheon Systems was awarded a contract for the development of ASTOR, and selected the Global as the COTS platform for the Raytheon ASARS-2 side-looking airborne radar—an upgraded version of the radar carried by the Lockheed U2R high-altitude reconnaissance aircraft.
ASARS-2 is interoperable with that system. First flight of the Sentinel took place in May 2004. Modifications to the COTS Global Express include a large canoe-shaped radome under the forward fuselage, which houses the radar antenna, a radome on the upper portion of the fuselage for the satcom antenna, and a bullet-shaped fairing on the vertical stabilizer.
Delta fins are added to the aft lower portions of the fuselage to offset any aerodynamic lateral instability created by the large radar fairings. Defensively, the Sentinel is equipped with the Defensive Aids Group integrated electronic warfare system from BAE Systems, which includes a defensive radar, missile warning system, and chaff and flare dispensers, among other countermeasures.
Savannah GA-based Gulfstream also has a longstanding relationship with various government agencies, foreign and domestic, in providing head-of-state and support aircraft. One example is NASA's use of Gulfstream products from the original turboprop Grumman G159 Gulfstream through the Gulfstream II and III as the product line evolved.
NASA's affiliation with Gulfstream led to the creation of the Shuttle Training Aircraft (STA), a heavily modified GII featuring the controls, avionics and HUD from the Space Shuttle for the left seat, as well as high drag devices on the airframe, and modified flaps to help simulate the steep approach angles and brick-like glide characteristics of the Shuttle.
Two more recent COTS uses of Gulfstream aircraft warrant particular attention—the airborne multi-intelligence laboratory (AML) and the conformal AEW aircraft (CAEW).
The AML, certified in 2009 by Lockheed Martin, is a GIII modified to act as a test bed for a multitude of sensors that encompass the idea of command, control, communications, computers and ISR—or C4ISR as it is known in defense circles.
This is merely an acronym that describes the larger, military notion of command and control. The Gulfstream III AML is a test aircraft and is not slated for production, but it is being used as a platform for future development of an array of sensors and information-processing capabilities.
Unlike the AML, the CAEW is not a test aircraft but a COTS aircraft, in service with both the Israel Air Force (since 2008) and Singapore Air Force (since 2009). Based on the G550 airframe, the CAEW has such large protuberances in the form of antennas and radar fairings as to make it barely recognizable as a G550.
No longer as easy on the eyes as a typical Gulfstream, the CAEW has eyes of its own in the form of an Elta EL/W2085 AEW phased array radar, which provides 360° coverage through 4 large fairings.
The protuberances—including a bulbous nose radome, a large tail-mounted radome and 2 large lateral fairings just aft of the cockpit on either side of the aircraft—make up most of the external modifications. Other systems and external antennae reflect additional C4ISR-type capabilities.
As the theory goes, adherence to the true off-the-shelf nature of COTS is followed by success because proven airframe and engine designs do not often fail arbitrarily. Preserve the original COTS design, bolt on various radars, hard points, weaponry, countermeasures and paint it green or gray, and generally it will work quite well in a military role.
Yet alter the airframe or engine for arbitrary reasons, and trouble will ensue. Sadly, this has been the experience with a few COTS helicopter programs. Well-designed helicopters like Eurocopter's AS365 Dauphin and EC145 have fallen victim to the nuances of the military or government procurement engine—a process that often causes an otherwise excellent helicopter to underperform in the role for which it was procured.
When Eurocopter's AS365 joined the US Coast Guard as the HH65, the procurement contract demanded that a certain percentage of the value of the aircraft be derived from US manufacture.
This requirement led to a re-engineering of the HH65 to accept a different engine than called for by Eurocopter, and the US Coast Guard's AS365s were equipped with the Lycoming LTS101-750B2 instead of the Turbomeca Arriels that powered the COTS AS365.
Problems with the LTS101 led to inflight engine failures—not a good trait in a search-and-rescue helicopter. In 2004, a program to re-equip the fleet with different engines was begun, and the Lycoming powerplants were replaced with—ironically—Turbomeca Arriels.