Automatic takeoff and landing systems are currently
installed on a wide range of UAS and manned aircraft. However, there are still
a number of aircraft that can be flown manually by a pilot or operator during
these critical phases of flight. Choose one manned aircraft and one UAS that
have an automated takeoff and landing system. Describe in detail the
capabilities and limitations of its automated system and the effect that it has
on safe operations. Give a recommendation for the automation level you think
would be best to install in future variants of your chosen system. Here are
some questions that you can ask and answer to give you a starting point in your
analysis:
Automatic Takeoff and
Landing Systems
Embry-Riddle Aeronautical University
ASCI 638 Human Factors in Unmanned Aerospace
Systems
April 30, 2017
The
proliferation of automated systems has steadily increased in the aerospace
industry since shortly after the Wright brothers first flight in 1903. This
automation can be traced back to an autopilot and automatic stabilization
device for which the Wright brothers were awarded patents in 1913 (Orlady and
Orlady, 1999, pp. 223-224). As aircraft technologies advanced and flight ranges
increased, autopilots gained importance as a tool to reduce pilot fatigue due
to long periods of manual piloting.
Most current
autoland systems rely on ground-based instrument landing systems (ILS)
available at select runways. These legacy systems utilize localizer and
glideslope transmitters located at the end of each runway (Croft, 2015). In
accordance with Advisory Circular (AC) 120-28D (FAA, 1999) a safeguard of
autoland systems for Category III operations must be in place “The means for
crew intervention must be provided, however, in the unlikely event the pilot
detects or strongly suspects inadequate system performance (e.g., the pilot
determines that an automatic landing cannot be accomplished within the
touchdown zone)” (p. 5). These systems are slowly being replaced by the ground
based augmentation system (GBAS) which utilizes ground positioning satellite
system (GPS) signals (FAA, 2016). This is an important advancement as part of
the Next Generation Air Transportation (NextGen) system. This system is already
being used in several airports and enables higher traffic and advanced
procedures that ILS cannot perform.
Autoland
systems are not limited to airliners or the need for GBAS. According to Horne
(2015), Diamond Aircraft has successfully demonstrated an autoland system. The
system will be available on Diamond Aircraft’s model DA42 four-seat twin engine
aircraft. The system is designed primarily as a backup or emergency system that
can be manually or automatically engaged for instance, in the case of pilot
incapacitation. In such cases, the aircraft can detect when it is approaching
its destination and if there are no pilot control inputs, the system
automatically engages.
The
DA42’s system performs an autonomous approach and landing at the nearest
airport. This is accomplished using GPS navigation and radar altimeter data.
The system actuates autothrottles, extends flaps, and extends landing gear
automatically for landing. The company is also working on incorporating an
autobrake function (Horne, 2015).
The
RQ-4 Global Hawk is an unmanned aircraft that utilizes both an automated
takeoff and landing system (Loegering, & Harris, 2002). As part of the
preflight, a mission plan is loaded into the aircraft that “includes the taxi,
takeoff, flight, landing, rollout and final taxi navigation waypoints that
define Global Hawk’s entire flight plan” (Loegering, & Harris, 2002, p. 2).
This enables an autonomous flight from taxi to parking.
Unlike
most other unmanned aircraft systems (UAS) and manned aircraft that use
joysticks or yokes along with rudder pedals for control inputs, the Global Hawk
crew uses a computer mouse to click on control commands. Aircraft operation commands
include “taxi, stop taxi, takeoff, takeoff abort and land abort” (Loegering,
& Harris, 2002, p. 2). During the mission, if the crew must alter flight
plans, it is done via override commands including “altitude, airspeed and
heading are available as are commands for mission suspend and ‘waypoint go-to’s’
for re-flying or skipping portions of a mission” (Loegering, & Harris, 2002,
p. 2). Because of these limited control inputs, accurate mission planning is
critical.
Through
the use of differential GPS and dual radio altimeter sensors, the Global Hawk
is capable of autonomous landings without the use of ILS or GBAS systems (Loegering,
& Harris, 2002). The landing approach is automatically initiated when the
aircraft reaches a waypoint known as the initial approach fix approximately 11
miles from the runway, at an altitude of 5,260 feet above ground level (AGL).
After reaching this waypoint, the aircraft switches from barometric to inertial
altitude measurements with a glideslope of 4.5°. The aircraft then proceeds to
the final approach fix waypoint 5 miles from the runway at an altitude of 2,390
feet AGL. Once the aircraft reaches 100 feet AGL, all control inputs are
ignored and the aircraft is committed to landing. At this point, the aircraft
uses an altitude rate of 2 feet per second while performing the landing flare.
Once the aircraft comes to a complete stop, the crew can regain control for
taxi or allow autonomous taxi off of the runway to the pre-planned mission
endpoint (Loegering, & Harris, 2002, p. 3).
The
aircraft does have a manual option of abort for takeoffs and go around for
landings. Most of the systems in the Global Hawk are double or triple redundant
providing added safeguards in the case of an automatic system’s malfunction.
Because these systems rely heavily on the pre-programmed mission plan and
merely require the click of a mouse, crews require little training in their
operation. Unfortunately, there is nothing the crew can do during final
approach once the aircraft penetrates 100 feet AGL. This is likely a safety
feature that takes into account control latency between the ground control
station (GCS) and the aircraft. Despite this, the Global Hawk has proven itself
capable of autonomous takeoffs and landings.
In
conclusion, the level of autonomy used by the Global Hawk is well suited for
the restricted airspace and high cruising altitudes for which it typically
operates. Also, the automated landing system is effective considering the
latency involved when the GCS is located beyond line-of-sight. However, this
level of autonomy is likely too high for other UAS that must share airspace with
other aircraft and are likely to require more frequent control inputs from crew
members.
References
Croft, J. (2015, April 27). FAA targets 2018 for GPS-based autoland
capability. Aviation Week. Retrieved
from http://aviationweek.com
Horne, T. A. (2015, September 22). Diamond debuts autoland system. Aircraft Owners and Pilots Association. Retrieved
from https://www.aopa.org
Loegering, G., & Harris, S. (2002). Landing dispersion results- Global Hawk auto-land system. Paper
presented at the First Unmanned Aerospace Vehicles, Systems, Technologies, and
Operations Conference and Workshop, Portsmouth, VA. doi:10.2514/6.2002-3457
Orlady, H., & Orlady, L. (1999). Human
factors in multi-crew flight operations. Burlington, VT: Ashgate Publishing
Company.
U.S. Department of Transportation, Federal Aviation Administration (1999).
Criteria for approval of category iii
weather minima for takeoff, landing, and rollout (Ac 102-28D). Retrieved
from https://www.faa.gov/documentlibrary/media/advisory_circular/ac120-28d.pdf
U.S. Department of Transportation, Federal Aviation Administration (2016,
June 30). Ground based augmentation
system (GBAS) concept of operations (GAST-D). Retrieved from http://laas.tc.faa.gov/documents/GBAS_PLA_2015_04.01.00_GBAS_CONOPS.pdf
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