Urban Aeronautics AirMule

Background

After the 2006 Lebanon War, the IDF realized that it needed a special vehicle that could fly unmanned behind enemy lines in order to rescue its wounded. While the helicopter is the best evacuation vehicle, it requires an area clear of trees or electricity columns in order to land without obstructing the rotor. Chances of it safely leaving a fire-heavy zone are small as it attracts all sorts of weapons fire. The advantages of a ducted fan propelled unmanned air vehicle are that it could offer the same capabilities as helicopters, but without the serious operating limitations. It could navigate in and out of creeks, city streets, next to big buildings, compact alleyways and refugee camp warrens, while the shielded rotor blades make the AirMule tougher than a regular helicopter. Being unmanned, the AirMule could enter situations too risky for regular helicopters. It could deliver supplies or cargo, evacuate up to two casualties from the battlefield and transferring them to a field deployed hospital for medical treatment. Some missions may require to be conducted up to hundreds of kilometers from forward operating bases (FOB) and medical care facilities with the only medical support available on scene being unit medics or fellow soldiers. The war reports have shown that moving an individual only a few hundred yards can take an hour or more.

As of 2012 and into 2014, according to NATO STO TR-HFM-184 report, the AirMule remains the only available design that meets NATO and IDF requirement for an unmanned MEDEVAC and CASEVAC vehicle.

Urban Aeronautics Ltd. has patented its design as Fancraft. The Fancraft technologies are supported by 37 registered (granted) patents and 12 additional are in the process.

Tactical Robotics Ltd. (TRL), as a subsidiary of Urban Aeronautics Ltd. has an exclusive license for use predominantly in the unmanned military and homeland security markets. TRL has taken the lead in the development of the AirMule. Metro Skyways Ltd. (MSL), as a subsidiary of Urban Aeronautics Ltd. has an exclusive license for use predominantly in the manned civil Air-Taxi as well as Air-Rescue and MedEvac markets. MSL has taken the lead in the development of the X-Hawk.

Development

In 2004, the X-Hawk LE concept was published by Urban Aeronautics.

In June 2008, a scaled-down technology demonstrator Panda flew for the first time. It was built to demonstrate its new flight control system and to attract partners.

Elbit Systems, Israel Aerospace Industries and Urban Aeronautics joined in the X-Hawk project headed by the non-profit Aerospace Medicine Research Center (Fisher institute for air and space strategic studies).

The initial idea for the UAS were civilian in nature, but after the publication of plans to equip the US marines with UAVs capable of transporting humans, it was decided to concentrate on the military arena. In 2008, Urban Aeronautics released its initial concept art. On January 7, 2009, a cargo variant that will be able to fly at speeds of 200 to 463 km/h (250 kn) began wind tunnel testing. In 2009, the Mule model was shown at the Israeli pavilionat at the 48th Paris Air Show. Its maiden flight was scheduled for April 2009, but was postponed. In June 2009, the UAV was shipped to a flight-testing facility located in central Israel where its Turbomeca Arriel 1D1 engine performed a series of ground tests for hover testing.

Phase 1: hover control system

Around January 12, 2010, the renamed AirMule had its (tethered) maiden flight and achieved only an altitude of 2 feet. In 30 tethered tests of 1 min duration, it completed the first phase of testing and it demonstrated the fly-by-wire control system’s ability to stabilize the vehicle in all three axes using inertial measurements augmented by GPS and two laser altimeters. The next phase of flight testing planned for March was moved back. On April 21, 2010, it achieved sustained tethered automatic hovering flight at an altitude of up to 9.8 ft (3m), which paved the way for the first untethered flight later that year. After 40 test hovers and 10 hours of flight time, the AirMule underwent systems upgrades. By October 5, 2010, the AirMule's skid were replaced by a wheeled landing gear to facilitate ground manoeuvring and to enable short take-off (STOL) and vertical landing operations (VTOL). First considerations were given to countermeasures.

Phase 2: free hovering and low-speed flight manoeuvres

Flight testing resumed until January 2011 when the AirMule underwent systems and structural upgrades which were completed by May 9, 2011. It was fitted with an expanded suite of sensors, and a new energy-absorbing wheeled landing gear. The aerodynamics if the lower fuselage was improved for better control responses in gusty wind conditions. On June 30, 2011, it was revealed that a variant the AirMule will be equipped with a remotely operated robotic arm to undertake tasks that pose a danger to humans. This was in response to requests by operators of power line maintenance, and by agencies responsible for the safety of nuclear reactors. By August 2011, the AirMule had accumulated approximately 40 flying hours. The Defense Ministry is financing half the operational technologies. In September, 2011, the IDF had identified an operational requirement for an unmanned VTOL platform that will be used to perform resupply and medical evacuation tasks from the front line. The IDF started to allocate a budget for the requirement in the long term acquisition plan. The defence ministry will participate in the funding. Around October 31, 2011, construction on a second AirMule prototype has started. It will receive a double redundant hydraulic system and stealth features.

Phase 3: full flight envelope testing

On April 23, 2012, it was revealed that a Controp D-Stamp stabilized electro-optical airborne sensor was installed on the first prototype.

On January 21, 2013, it was revealed that the first prototype will receive new propeller blades for the new six-bladed rotors. These will replace the four-bladed rotors that have been used since the beginning of 2010. The change will increase payload capacity by approximately 200 kg (440 lb). The blades comply with the loads specified for the US Federal Aviation Administration's FAR 35 standard for propellers. The first test flight was scheduled for mid-February. On February 26, 2013, plans for a high-speed AirMule version was revealed to be the previously tested cargo variant. It will be used for tactical resupply missions.

On February 25, 2014, it was announced that Green Hills Software real-time operating system (RTOS) had been chosen by Urban Aeronautics.

Design

The design, Fancraft, was inspired by the Piasecki VZ-8 Airgeep's revolutionary design with two tandem ducted fans. However, that's where the similarities end. Forward thrust is primarily provided by two ducted fans thrusters located at the sides of the aft section. The lift fan and thrusters are powered by a single turboshaft turbine through three proprietary gearboxes and shafts. The early prototype was powered by a Turbomeca Arriel 1D1 which was later replaced a Turbomeca Arriel 2. Originally the prototype lift fans had four-blade rotors, but the final fans have six-blade rotors with staggered-rotors for a speed variant.

The fuselage is constructed from carbon (fiber)-composite. Two 770 liters air-conditioned cells on its sides are designed to receive stretchers and casualties. The cells will also have devices for transfusions during flight. Initial interior cabin noise was measured in hover at 95 decibels without any incorporated acoustic treatment or liners. An additional 1,100 liters are available in an optional belly mounted compartment. The fuselage forms an airfoil and generates over 50% of lift at high speed (US Patent # 7,806,362B2). An aerodynamic bulge between the ducted fans keeps the airflow attached to it, hence generating lift, while diverting the airflow into the aft fan for increased thrust.

For military purposes the AirMule can be equipped with flare and chaff countermeasures. Since the second prototype, the AirMule has improved stealth. The fuselage structure and design of the engine’s exhaust pipe reduce its noise, heat, and radar signatures, including an appropriate flight profile. Early tests without stealth measured 87 decibels during hover at a distance of 125 feet. The Trophy system was considered for inclusion.

Flight stability, forward speed and safety

For increasing or decreasing overall lift, the angle of attack for all blades is collectively altered by equal amounts at the same time resulting in ascents, descents. The Fancraft technology on the AirMule employs a Vane Control System (VCS)(US Patents #6,464,166 and 6,817,570) consisting of 200 vanes at the inlet and outlet ducts that can be deflected simultaneously (top and bottom) or differentially to generate side force or a rolling movement. Front and rear ducts are deflected differentially for yaw. The VCS generates six degrees of freedom independent of one another. The VCS is powered by a dual redundant hydraulic system which will allow for uninterrupted rotor pitch control in the event of a failure to one of the pressure supply lines. The VCS is engaged in excess of 100 per second. The early VCS was generating more than 2.0 radians/sec² of roll acceleration for roll and yaw control. It was planned to double roll acceleration with planned improvements, enabling precise hovering in gusty wind conditions with wind speeds of up to 50 kn (92.5 km/h).

A set of louvers at the front of the forward duct and rear of the aft duct that open during forward flight to allow the incoming flow to move through the duct and thereby greatly reduce drag to enable forward speeds of 100–120 knots in contrast to a top speed of typically 40 knots in a conventional ducted-fan design (US Patent # 7,806,362B2).

Due to the absence of a rotor, hence autorotation, Fancraft will be equipped with a ballistically deployed parachute to be used in cases of catastrophic engine failure.

Sensors and radars

The AirMule is equipped with GPS for translational position and velocity readings, two laser altimeters to indicate the vehicle’s height above ground which will be augmented by a doppler radar altimeter for dusty conditions.

A Controp D-Stamp stabilized electro-optical sensor provides as part of the auto-land system will enable the aircraft to guide itself to land over any high contrast marker (flare, flag, a red cloth) in a combat zone. If a landing site cannot be highlighted by placing a physical marker, a laser spot from an airborne designator could be used.

Avionics

The flight-control system is a four-channel redundant fly-by-wire system that relies almost entirely on inertial measurements augmented by GPS signals.

The AirMule uses the Integrity real-time operating system (RTOS) and Multi integrated development environment (IDE) for custom programming.

Ground control, telemetry and navigation

Sensors and other subsystems use three datalinks providing 460 channels of real-time telemetry.

The retrieved and transferred data will be stored at a ground control unit (GCU), which will be equipped with an air data computer for displaying its position. The GCU will monitor telemetry data supplied by the UAV using uplink and downlink communication devices. Pilots will use a fly-by-wire flight control system, as well as an automatic stabilization feature to help control the aircraft and maintain level flight. The AirMule can land safely despite communication errors in the GCS.

Certification

FAA certification has been a prime consideration in every aspect of Fancraft. Fancraft is being designed in compliance with the FAA's FAR Part 27 and Part 29 (depending on weight) certification standards. They also comply with the special 'Powered Lift’ certification standard that was developed for Tilt-Rotor aircraft.

Scenario

A single AirMule is capable of ferrying 500 kilograms (1102 lbs.) of useful cargo per each 50-kilometer (31 statute miles) radius sortie, thereby delivering approximately 6,000 kilograms (13227 lbs.) over 24 hours. A 10–12 AirMule "Mobile Supply Unit" can deliver supplies, day after day, to sustain 3,000 combatants, while at the same time ferrying back their wounded and casualties.

Equipped with remotely controlled manipulator arms it can be used for inspections, maintenance operations or repairs, flying above dangerous zones such as nuclear reactors and areas contaminated by chemical plant leaks. Examples could include replacing damaged insulators on power lines, pumping heavy water into pools covering uranium rods inside damaged nuclear reactors, fixing leaking pipes or repairing areas under bridges or marine structures that have suffered corrosion damage, and agricultural spraying.

Variants

Partners

Urban Aeronautics is in contact with the United States Army and the militaries of other nations, including India and Italy, for possible sale of the "AirMule”.

Specifications

Data from

General characteristics

Performance