Friday, November 28, 2014

Automatic take-off and landing of a Boeing 737 and a Predator B

Automatic take-off and landing of a Boeing 737 and a Predator B
            The two aircraft chosen for review are the Boeing 737 (manned) and the Predator B (unmanned).  Automatic take-off and landing systems have come as an increasingly beneficial feature in many manned an unmanned aircraft.  These systems were essentially designed to allow for safe landing in areas or situations previously thought too difficult to land in; this include areas of poor visibility or in adverse weather conditions (Larson, 2012).  Therefore, although it may often be ideal to have manned take-off and landing, it sometimes may be impossible or unfavorable to do so.
            The Boeing 737 utilizes an automatic landing system termed “autoland”.  Autoland systems typically consist of several components including an instrument landing system (ILS) radio that is responsible for receiving localizer and glideslope signals to help interpret the direction from the ILS frequency transmitter on ground for the approaching aircraft (Craig, Houck, & Shomber, 2003).  The automatic landing system of a Boeing 737 involves approximately 6 major phases upon descent.  The first two consist of the automatic approach.  In this case, the ILS radio utilizes the localizer and compass to determine azimuth and measures barometric height to determine elevation (Craig et al., 2003).  The next four phases are the automatic land phases including leader cable, attitude, flare, and kicking off drift  (Craig et al., 2003). 
Briefly, the pilot will first establish an approach.  Once this is done, the pilot will follow the ILS approach path that is indicated to him/her by the localizer.  The pilot then descends down the glide path to the decision height where he/she must determine weather or not there is enough visual information for a safe landing.  Safety precautions have been made in the design so that once autoland is engaged and have received ILS signals it will automatically land without any further human intervention and can only be disengaged by disconnecting the autopilot completely (Craig et al., 2003).  There are also redundancies in the system (typically at least two or three independent autopilot systems working together) to protect against any system failures and improve safety (Craig et al., 2003).  The Predator B’s autolanding system functions differently.
The Predator B is an unmanned aircraft used for intelligence, surveillance, and reconnaissance (General Autonomics, 2013).  The Predator B can successfully complete automatic takeoff and landing capability (ATLC) landings through its use of autonomy.  This UAS can autonomously track the centerline, reduce speed as necessary and even initiate the brakes once it has reached its targeted ground speed (Kasitz, 2012).  Additionally, the Predator B unlike the Boeing 737 is also able to takeoff autonomously, utilizing similar procedures to the landing.  The Predator B’s automated takeoff and landing also have the option of being fully autonomous or assisted.  In the latter, the pilot may perform certain actions, essentially acting as a supporting pilot as the Predator’s system takes over the remaining tasks.  Conversely, a pilot may also regain full control of the UAS and completely control the take-off and landing of the Predator, which is often the case (Austin, 2010).  The availability of these various flight options of the Predator adds a layer of safety to the system.
Safety is always a primary concern in any flight operation, as such both the autoland of the Boeing 737 as well as the ATLC and controlled landing of the Predator B help improve safety.  In the case of the Boeing 737, as once the autoland is engaged it is essentially locked in place for landing in order to avoid potential accidents (i.e. accidentally changing landing details).  Redundancies are also in place to improve safety.  The Predator on the other hand has several control options from fully autonomous, to partially autonomous and even fully controlled to help improve safety. 
Although all these options have their benefits and drawbacks, this author recommends a partial automation level as the best system to install in future variants of the Boeing 737 and Predator B.  The Predator B already contains this level of automation, however having a shared level of autonomy and pilot control seems to be the safest option as it offers an additional layer of decision-making.  This serves as a kind of ‘safety net’ with the pilot and the automated system performing as a sort of ‘check and balance’ for the other.  Perhaps instead of having 3 redundant systems in the UAS as previously mentioned, the Predator could have 2 redundant systems and a third system replaced with human control as the ‘check’ on the system.  However, future research would need to be studied in order to determine the plausibility of this design.


References
Austin, R. (2010). Unmanned Aircraft Systems. West Sussex, United Kingdom: John Wiley &
Sons Ltd.
Craig, R., Houck, D., & Shomber, R. (2003, April 1). Approach navigation options.
Aeromagazine, 12-21.
General Autonomics. (2013). Predator B UAS. Retrieved from http://www.ga-
asi.com/products/aircraft/predator_b.php
Kasitz, K. (2012, September 17). Predator B Demonstrates Automatic Takeoff and Landing
Capability. Retrieved from General Autonomics: http://www.ga-asi.com/news_events/index.php?read=1&id=400
Larson, G. (2012, August 1). The first autolanding. Air & Space Magazine.


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