Friday, July 11, 2014

"Who's flying this thing?"

Automatic Takeoff and Landing Systems

     Most modern passenger and cargo aircraft and some GA aircraft are equipped with automatic landing systems and some form of automatic take-off assistance to the pilot. Current popular aircraft like the Boeing 777 and its newest sister aircraft, the 787, are equipped with state-of-the-art automatic landing systems normally used by its pilots and are highly recommended for use during adverse weather or low-visibility situations (Boeing Commercial Airplanes, 2014). While some of the most popular unmanned aerospace systems currently in use, like the Predator and Global Hawk UAS, are capable of automated taxi, takeoff and landing, others have unique launch and recovery procedures. One such UAS is the US Army RQ-7B Shadow 200 Tactical UAS.
   
     The Shadow 200 Tactical UAS is the US Army’s premier tactical UAS used by maneuver units engaged in wartime conflict. One of the most favored assets in the field the Shadow 200 has been in use since the start of the war on terror and currently remains in use. The Shadow 200 TUAS is a small, lightweight, rapidly deployable, short-range airborne reconnaissance system designed to give the battlefield commander a day/night, multisensory collection system. The TUAS features improved connectivity to joint forces that provides needed, Near Real Time (NRT) battle information not easily obtainable from standoff airborne sensor systems, ground collection systems, or scouts. The Air Vehicle (AV) mission is to support the local commander’s Reconnaissance, Surveillance, and Target Acquisition (RSTA) plan and provide the commander with NRT intelligence data in support of missions throughout the range of military operations (SHADOW 200 Tactical Unmanned Aircraft System, 2013).
   
     Shadow 200 crew members and operators undergo weeks of specialized training for their job. Because of the system’s proprietary launch and landing procedures the crew trains to respond to launch and landing emergency procedures unique to the Shadow 200 system. The Shadow 200 TUAS does not have manual alternatives to the automatic launch and landing system, the UAS pilot is not able to launch and land the AV in a conventional manner similar to manned aircraft or other UAS.

     Auto Launch System

     Rapid setup and teardown times ensure that the Shadow 200 TUAS keeps pace with brigade movements. To facilitate rapid ground force movement, AV control may be passed to other control stations or Launch/Recovery (L/R) stations while the AV is airborne. This allows the commander to conduct a series of tactical movements while still receiving continuous target coverage. The system utilizes a hydraulic launcher subsystem to facilitate launching of the AV to its operating speed in an expeditious manner, in keeping with the system’s tactical rapid deployment concept (SHADOW 200 Tactical Unmanned Aircraft System, 2013).

     The Shadow 200 TUAS LAU accomplishes AV launch by using stored energy from a nitrogen accumulator powering a hydraulic launch cylinder. The launch cylinder applies acceleration forces to the AV by a shuttle assembly, guided during launch by a guide rail, and inclined approximately 10° (8.5° deg for the High Power Launcher "HPLAU") relative to the ground. During launch, the AV, mounted on the LAU shuttle, accelerates up the guide rail pulled by a steel cable run through a series of pulleys at a 5 to 1 ratio from the rod end of the hydraulic launch cylinder. When the shuttle is in the pre-launch position, a positive latching shuttle release mechanism holds it in place. Upon receiving the launch signal, the shuttle release mechanism releases the shuttle, and the shuttle and AV accelerate up the guide rail. Acceleration forces hold the AV in the shuttle until near the end of the launch stroke, where the shuttle engages the shuttle-arresting strap (the High Power Launcher (HPLAU) uses two arresting straps), freeing the AV for launch. At that point, forward motion sends the AV airborne at a predetermined airspeed. Deactivating the Launcher with the Launcher Hand Control Unit (LHCU) causes automatic venting of residual launch pressure to the Launcher hydraulic reservoir, which renders the system safe at launch stroke completion. Following each launch completion, the shuttle is returned to the pre-launch position and latched into the shuttle release mechanism (SHADOW 200 Tactical Unmanned Aircraft System, 2013).

     The Shadow 200 AV can only be launched using the launcher; no other methods of launch exist for the system. In the event of an emergency requiring an aborted launch the following actions are performed by the crew: The crew chief (CC) announces “stand by” to hold the crew on present conditions, then releases the launch switch from Launch to Hold; if AV fails to launch after two tries the CC announces “launch fail” to the crew and alert every one of the emergency and then closes the switch cover to prevent accidental launch; the crew then stops launcher pressurization and begins depressurization procedures, performs complete shutdown procedures to investigate the cause of the failed launch.

Auto Landing System

     Shadow 200 uses the Tactical Automatic Landing System (TALS). The TALS provides automatic landing guidance and control for the AV. The TALS is divided into two subsystems: the Airborne Subsystem (AS) and the Track Subsystem (TS). The AS is contained within the AV and consists of an AS Transponder and AS Antenna. The TS remains on the ground and consists of a Track Control Unit (TCU), an Interrogator unit, an Antenna/Radome and a Pedestal unit. The TCU contains software that flies the AV during automatic recovery. The TALS subsystems provide precise position information required for automatic AV recovery. The subsystems provide near all-weather, day and night, position-sensing capability. The AS provides a unique point of reference on the AV, enabling the TS to detect and precisely track the AV. The TS measures the AV position relative to the Touch Down Point (TDP). The TS is capable of tracking an AV (with an AS) at a maximum distance of approximately 2.4 miles (3.9 km), 2.1 nautical miles (nmi) in worse case environmental conditions (i.e., rain) (SHADOW 200 Tactical Unmanned Aircraft System, 2013).

     In the event of TALS failures which can be a TALS abort below decision point or a TALS recovery failure (e.g. loss link, failure to acquire, etc.) the Shadow 200 is equipped with a POP300 chute recovery system. When TALS failure occurs and no remedial action regains its use to safely land the AV the crew performs emergency recovery procedures which includes flying the AV to a designated rendezvous point, cutting the engine power, and deploying the recovery chute to bring the AV back to ground in the safest way possible, preserving the AV and its payload for future use.  

Reference 

Boeing Commercial Airplanes. (2014, July 10). Retrieved from Boeing: http://www.boeing.com/boeing/commercial/787family/index.page?

SHADOW 200 Tactical Unmanned Aircraft System. (2013). Washington, D.C.: US Army.

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