Page 16 - Dec 19 TNT

Autoland is part of Piper’s newly announced Halo system that bundles safety equipment including autothrottle, electronic stability and underspeed protection, emergency descent mode, level mode, SurfaceWatch and SafeTaxi. At present, autothrottle is only functional for Autoland, but the company plans
to offer a fully functional autothrottle by year-end. The M600SLS – the nomenclature stands for safety, luxury and service – also incorporates an updated interior and Piper’s Ultimate Care Program, covering scheduled maintenance and hourly/calendar-based inspections for 5 years.
fuel on board, runway length, air- space, real-time weather, terrain, controlled vs uncontrolled airports. It then ranks the choices and selects the most suitable one for landing.
It does all that in .8 of a sec- ond or less.
Garmin leaned on its flight test pilots to vet the cascade of decisions and criteria weighting that leads it to the best airport and runway selec- tion. They knew they had it right when the pilots looked at Autoland’s decision and said, “Yeah, that’s the decision I would make.”
According to Eric Tran, senior soft- ware engineer who led the design of the routing algorithm, explained that ultimately the individual air- craft manufacturer determines the weighting system, as each airframe has different capabilities and toler- ances for weather conditions or run- way lengths. For example, a more capable aircraft might be willing to fly through green precipitation returns to reach the most suitable runway, while a light aircraft might fly around them or land somewhere else. The system is also smart enough to realize that if it is currently flying in a precipitation area that is higher than the base tolerance, such as a yel- low return, it relaxes that tolerance (since it’s already in it) and continues on, but continues to navigate around yellow or red returns ahead.
Preferred runway length for Au- toland is something that is driven by the manufacturers of different aircraft platforms. For the M600SLS, Piper stipulated that 5,000 feet was the ideal minimum runway length, with 4,500 being acceptable if given no other choice. Garmin analysis showed that about 75 percent of U.S. airports equipped with GPS LPV or LNAV/VNAV approaches also have runways that are at least 4,500 feet long.
How Autoland Chooses
After the passenger pushes the Au- toland button, the system evaluates all airports around it and determines its route and ultimate destination. It looks to avoid selecting Class B an- chor airports, which typically have
busy, congested airspace, unless that is the only suitable choice available. It uses all the available weather sources on board, including SiriusXM, FIS-B and/or Iridium datalink weather (but not onboard radar), to help it decide which is most suitable route and landing site. It also considers run- way length required, fuel on board, terrain and obstacles, and the avail- ability of a GPS approach with lateral and vertical guidance.
Further, if the aircraft is outside a 20-minute radius of its landing point, it will calculate a forecast based on what it already knows about the weather. For example, if a cell is mov- ing in and forecasted to be on top of the airport, it is capable of predict- ing that and either choosing a new destination or entering a hold until the cell clears. Throughout Autoland sequence, it will continue to evaluate the weather to reaffirm its runway choice or change based on chang- ing conditions. However, once the aircraft is at the final approach fix, it’s locked in and will continue to a landing. For baro setting, it uses the GPS estimate, and as it gets closer it will use a setting that matches land- ing pressure altitude, which would be particularly critical in a mountainous area or a location with obstacles. For the M600SLS, the de-ice system is activated and remains on when it de- tects an OAT below 5 degrees Celsius. It also flies the holding pattern and approach slightly above book speeds because of the unknowns, such as potential airframe ice or wind shear. It does not utilize the onboard radar because of the manipulation of the beam required relative to aircraft altitude and attitude to get the best picture of precipitation ahead.
Likewise, if the system determines the aircraft is too high to begin the approach sequence, it will enter a standard hold to lose altitude and then execute the approach.
During the approach phase, it flies the glidepath using GPS just like the autopilot normally would. On very short final, it blends radar altimeter inputs to decide when to deviate from the glidepath go into vertical speed mode. Garmin tested it in a variety
14 • TWIN & TURBINE / December 2019