Mark Ayton spoke with members of Textron Aviation’s flight-test team about the design concept and production evolution of the Scorpion jet
MILITARY SCORPION
Wichita, Kansas, is the home of Textron Aviation. Its portfolio includes Beechcraft, Cessna and Hawker, all well-known brands that produce aircraft such as the twin turbo-prop King Air, Citation business jets, the Cessna 172 and the T-6 Texan II military trainer. What then, is Textron doing by designing and building a brand-new jet with a tough military name like Scorpion? In short, to meet the need for an alternative, low-cost aircraft suitable for many of the requirements of current airpower implementation, particularly in Afghanistan and Iraq.
Self-driven, self-funded
Textron analysed the military market, identified a gap in the market for a multirole tactical aircraft, self-funded the design and production of the first demonstrator aircraft, registration N531TA (Cessna model E530 c/n 721001 dubbed D1), and achieved first flight in less than two years from initial design. That’s a remarkable feat: one that’s made more remarkable considering it was all achieved using a commercial business model and without a US Department of Defense requirements document, usually the driver behind new military aircraft designs in the United States.
According to Steve Burke, one of Textron’s senior defence advisors, within the gap there is a great deal of performance white space (meaning an aircraft that has greater performance than an unmanned air vehicle and a single-engine turboprop aircraft, and greater loiter time and ISR capability than fighters like the F-16 or F/A-18) that has not been addressed by the Department of Defense. This capability gap was also identified in a defence white paper titled ‘Restoring American Power’ by Senate Armed Services Committee Chairman, Senator John McCain, who said: “At present, our forces have neither the right mix of capabilities nor sufficient capacity to do so. Our military is optimised for fighting in relatively permissive environments and too small to serve as a credible deterrent force in Asia, Europe and the Middle East, while conducting prolonged counterterrorism operations worldwide. Our military’s capabilities are also out of balance. On the lower end of the spectrum, we need greater numbers of more affordable, less advanced systems to fight terrorist enemies in permissive environments. On the higher end of the spectrum, as nation-state rivals can increasingly counter our military’s ability to project power, we need longer-range, more survivable platforms and munitions, more autonomous systems, greater cyber and space capabilities, among other new technologies. In this way, the joint force should be equipped with what is often called a high/low mix of capabilities.”
SCORPION CHARACTERISTICS
Length: 45ft 6in (13.86m)
Height: 13ft 4in (4.06m)
Wingspan: 47ft 10in (14.57m)
Wing area: 175.3ft2 (16.28m2)
Empty weight: 12,700lb (5.760kg)
Max take-off weight: 22,000lb (9,979kg)
Max internal payload: 3,000lb (1,360kg)
Max speed: 450kts (830km/h)
Service ceiling: 45,000ft (13,716m)
Ferry range: 1,600nm (2,960km)
Ferry range (with auxiliary tanks): 2,200nm (4,075km)
Engines: Two Honeywell TFE731-40 medium bypass ratio turbofan engines, each rated at 4,000lb (18kN) thrust
Not surprisingly, given its concept of development, the Scorpion jet can perform the mission set of an unmanned air vehicle or a single-engine turboprop light attack aircraft, but is also optimised for a higher set of missions across a number of domains. Textron’s design engineers have focused on giving Scorpion the ability to conduct the ISR armed reconnaissance mission.
Textron sought to create Scorpion as a basic affordable aircraft with scalability up to the mission set required by US armed services. This has been achieved by the aircraft’s payload bay, which affords space, weight, power and cooling margins that allow new mission system pallets to be easily fitted (even in the field), a modular open architecture mission system and avionics, and the ability to employ advanced weapons.
Five main criteria required:
• A tactical jet-powered aircraft with the ability to operate with NATO fighters during combat in terms of performance and interoperability.
• A payload capacity, including the nose mission bay forward of the cockpit, which has a retractable camera mount for a 15- inch (380mm) class electro-optical sensor and a radar system in the nose cone, and three payload bays in the belly of the aircraft that provide an additional 85ft (2.4m3) of available space for user-specific mission equipment.
• A modular mission system that allows new systems to be added in to the bay with plug-and-play capability.
• Nearly five hours on-station loiter time, at more than 100 nautical miles (180km) from base with a sensor payload and mission equipment capable of detecting targets and generating weapon quality coordinates for the ISR armed reconnaissance role.
• Provision for aerial refuelling and selfprotection systems. These features are not standard to save cost and therefore meet affordability, to avoid limitations on export.
Because Scorpion meets these design features it can fly 11 combat roles (the mission set) - close air support, irregular warfare support, armed reconnaissance, combat search and rescue, forward air control, direct attack, humanitarian and disaster relief, maritime security, patrol, border security and advanced jet training, with the ability to conduct some components of lead-in fighter training.
All aircraft are configured to meet the roles undertaken by the US Air National Guard during active-duty Title 10 combat deployment, and those undertaken in support of full-time National Guard-duty Title 32 missions: response to emergencies and natural disasters, homeland defence.
To date, Textron has built three productionstandard model 530 Scorpions (P1 N530TX c/n 530-0001, P2 N532TX c/n 530-0002, and P3 N534TX c/n 530-0003) and have amassed more than 1,400 hours during demo and flight test activities.
Scorpion
Discussing the aircraft’s design, Steve Burke said: “Scorpion has a full carbon composite skin, carbon composite wing and features the ability to perform field repairs, change the wing and extend service life beyond its baseline 20,000 hours.”
Burke told AIR International: “The operator can perform field-based curing to repair battlefield damage. Its composite construction, combined with the flexibility of its structure, allows conformal antennas and arrays to be fitted to provide more flexibility to the aircraft’s modular avionics and mission systems.”
Scorpion’s mission system is called Widow, produced by L3 Technology ForceX. According to Textron, Widow enables rapid development of mission plug-ins called ForceX sensor controlled modules, software that allows Textron to quickly add new applications such as surveillance and information equipment into the aircraft’s core mission system and at low cost.
By October, Textron had flown one of its production standard Scorpion aircraft fitted with a Wescam MX-25 electro-optical and infrared sensor, a sensor that enables scene recognition, feature extraction and object detection. The Wichita-based company is also hoping to add a stand-off target recognition capability once the physics, optics and software is tested.
In baseline configuration, the Widow system architecture is designed for export. Textron is already working with various Air National Guards that run state partnership programmes with other countries. The company’s intent is to sell Scorpion fully interoperable with US and western air arms.
The architecture also allows rapid development and prototyping of different types of technology for quick integration and flight testing, and the ability to make adjustments quickly. The system’s aim is to make the process for adding new functions easy for customers.
A new function simply plugs in and plays without impeding the design assurance level of the Garmin 3000 digital integrated flight deck. Garmin has integrated what it terms the glass touchscreen controller as the primary point of data entry for the G3000 system featuring icon touch keys that enable access to the aircraft’s systems and sensors with a few keystrokes or page sequences. Future enhancements and applications can be accommodated without physical alteration of the mechanical controls. The G3000 features 14.1-inch (355mm) diagonal WXGA high-resolution multifunction displays that boast split-screen functionality.
Scorpion features heated leading edges of the wing, horizontal tails, engine inlets, and the windshield: a big benefit when operating in the types of adverse weather generally encountered by military aircraft when flying at medium and low altitudes while conducting surveillance as part of the wider ISR role.
Textron optimised the Scorpion for what the company refers to as persistent data collection, which can be maintained for nearly five hours when fuel is carried in auxiliary tanks; if the aerial refuelling capability is eventually integrated, then time on station extends further. The long loiter time was a major driver for the Scorpion’s high aspect ratio wing design with a 47ft 10in (14.58m) wingspan.
Powered by two Honeywell TFE731 medium bypass ratio turbofan engines, each rated at 4,000lb (18kN) thrust, when operating in an orbit at 150 to 200kts (275 to 370km/h) the aircraft’s combined fuel burn rate is 1,000lb (450kg) per hour.
Both engines are enclosed in air load (not structural) fairings for aerodynamic effect and can be removed and changed quickly using standard ground support equipment.
Honeywell’s TFE731 engines are quiet, too, as noted by members of the Kansas Air National Guard, who were unable to hear the aircraft in an orbit at 9,000ft (2,740m) at a 2 nautical mile (3.6km) slant range during a demonstration at the Smoky Hill range. Similarly, joint terminal attack controllers located on the range near Holloman Air Force Base during the US Air Force’s light attack experiment in August were reportedly surprised when the aircraft remained inaudible to them at close range.
Scorpion’s tandem, about centreline, cockpits provide good visibility, a big advantage in the ISR role and an important part of the aircraft’s design brief. Each cockpit, forward and aft, is configured both as a pilot and a co-pilot/mission operator station, which enables Scorpion to be flown from either cockpit for most of its assigned roles. The aft cockpit has additional controls to increase weapon system operator capability.
During the early design phase, Textron engineers evaluated a centreline vertical tail configuration, but because the aircraft is required to sustain 6g, flying at high angles-of-attack might have induced some tail blanking. In order to maintain directional control, rudder authority at high degrees of angle-of-attack and accounting for the 34-inch (860mm) wide payload bay also positioned about the centreline, the design team opted for an outward canted configuration to ensure the vertical tails stay in the free air stream. Secondly, Scorpion is not equipped with digital fly-by-wire controls, so the vertical tails function with the conventional elevators on trimmable horizontal stabilisers and ailerons powered by a 3,000psi, dual redundant manual backup mode flight control system. The company opted for a hydraulic-powered system to achieve the required capability, but also affordability; by comparison, digital flyby- wire systems are expensive to develop, buy and to service. Textron’s hydraulicpowered system is cheaper on all three counts and according to Steve Burke, “can be repaired anywhere”.
The Scorpion has yet to accumulate thousands of hours of flight time, so the aircraft’s current mission capability rate is based on the flight operations flown by Textron’s four-aircraft fleet. That’s now. Nobody knows what the future mission capability rate will be, though Textron has sought very high assurance on mean time between failure and mean time between repair estimates for all components used on the Scorpion. Steve Burke said: “We incorporated components and architecture commonly used in Textron’s fleet of business jets and other types. Many of the components used to build Scorpion, had previously been used in other product lines.”
Weapons detachment
In mid-July Textron deployed two production standard Scorpion jets, three test pilots and a team of flight engineers to Naval Air Station Patuxent River, Maryland. The detachment was staged to test safe separation or firing of four different air-to-ground weapons; 500lb (227kg) GBU-12 laser-guided bombs, 500lb BDU-50 practice bombs, 2.75-inch rockets, and 0.50 calibre rounds fired from HMP-400 guns on either wing.
A significant amount of integration work had to be completed before the aircraft left Wichita for the east coast. The Textron team had to build the weapon pylons, interface each weapon type with the aircraft, establish an envelope within which the weapons could be flown, generate the appropriate electrical power required and install the necessary avionics to control each weapon type, including switches in the cockpit.
Textron’s senior defence and special mission aircraft test pilot, Dan Hinson said: “The goal was to return to Wichita having expended each of the weapon types, thereby clearing an envelope, albeit limited, to employ the munitions for the light attack experiment held at Holloman. We had a twoweek schedule to complete all of the weapon separation and firing events for the four types of weapon in five release scenarios, meaning the game plan over the two weeks was aggressive.
“We evaluated separation of the BDU-50 and GBU-12, but for the gun and rockets, like all guns and rockets, hot gas ingestion is of concern so that was also evaluated. Each event was slightly different, and each was an end-to-end test of our weapons control mechanisms.”
Textron’s team started the Pax River tests at a very high-level of readiness after undertaking the company’s own test processes at Wichita and working through those issued by Air Test and Evaluation Squadron 23 (VX-23) ‘Salty Dogs’, the team’s host squadron at Pax.
All of the test event undertaken at Pax were on par with the processes and procedures used by VX-23. He explained: “We had five test events to complete, simultaneous firing of rockets from each side, firing the guns on each side, firing the guns simultaneously from each side, and dropping both types of bomb as they had not been undertaken with the productionstandard aircraft before.”
The Textron team pre-positioned both aircraft at Richmond International Airport, Virginia, and made the short hop to Pax River on the Monday morning; arriving at the Maryland test base on time. Hinson said: “We spent Tuesday going through the review process with the Naval Air Systems Command team, flew the first event on Wednesday, flying for five consecutive test days, each with a different weapon type. We started by firing rockets, one from the left, one from the right, then two together simultaneously. Then we fired two off the left side in rapid sequence, so four test events in the one mission.
“Next, was a single firing of the gun from the left and then the right side, and continued taking shots to prove the gun system and that hot gases from the gun were not being ingested and causing engine problems. There were none.
“Then, we dropped GBU-12s, dropping one weapon from one side with nothing else loaded on that wing, then a GBU-12 from a pylon on the other wing next to a gun pod. We achieved two test points under the same conditions. Then we dropped BDU-50s, by repeating the profile used with the GBU-12. The final event was a simultaneous firing of guns, one carried under each wing.”
Textron used LAU-131A/A launchers (the type capable of accommodating the APKWS guided-rocket) to launch unguided rockets - and in doing so - saved the cost of guidance systems.
Commenting on how the aircraft feels when bombs come off the pylons, Dan Hinson said: “You get a degree or two of roll but it’s easily countered thanks to the powerful ailerons. It’s a very stable platform and flies very well throughout the regime.”
Everything was conducted safely and successfully. Hinson noted: “We scheduled five, executed five and returned to Wichita four days early. That takes extremely good preparation, people who know what they are doing and a whole lot of luck.”
Data captured from the weapons testing was submitted to Air Force Materiel Command’s air worthiness authority to gain a military flight release so US Air Force test pilots could release bombs and fire rockets and guns from Scorpion during the light attack experiment.
Prospects
For the role of aircrew training Textron is upbeat about the Scorpion’s credentials. The company is working on a cockpit emulation application that will enable the multifunction display to be surrendered to a mission system application from another cockpit system such as the F-35 Lightning II.
AIR International understands that ongoing work being undertaken by Textron with the Scorpion is based on a request from the Department of the Navy to devise ways of increasing the readiness level of its earlymodel F/A-18E and F/A-18F Super Hornets. The US Navy is interested in exploring the possibility of using the non-carrier capable Scorpion to emulate the Super Hornet’s cockpit, head-up and helmet displays, and its HOTAS (hands on throttle and stick) to allow junior pilots to experience the thinking required to operate the Super Hornet’s mission systems. The objective is to enhance overall readiness of the Super Hornet force, but without its cost and maintenance burden.
Elsewhere, Air Combat Command’s boss General James Holmes is also pursuing ways in which to improve the readiness of his units. No surprise that Textron believes the Scorpion can be used as a companion trainer to other types, once again by emulating different cockpits. According to Steve Burke: “The idea is to fly an F-16 or F-35 pilot in a Scorpion to acquire tactical trigger time while supporting JTAC training, which costs much less than flying and F-16 or an F-35.”
