Page 12 - Volume 10 Number 8

PILOT KA SPEAK
Balancing
Your Backups
[Author’s Note: This two-part series will discuss a variety of navigation system failures and abnormalities, with ideas for training and handling them. While this installment will deal primarily with management of GPS abnormalities, the next installment will focus on the utilization of other navigation systems in GPS failure situations.]
It was a blustery spring afternoon in Wisconsin. I was scheduled to fly from Milwaukee’s Mitchell International Airport (MKE) to Central Wisconsin Regional (CWA) in a Beech 1900D Airliner. Most King Air pilots will recognize the 1900 as the “big brother” of the King Air 350 and the Beech 99. That day, I flew as a line check airman with a brand-new first officer who was conducting his first leg of Initial Operating Experience (IOE). The weather was gloomy with overcast skies, rain and stiff winds from the south-southwest. At the time, CWA had ILS approaches to runways 35 and 8, but no precision approaches to runways 17 or 26. So, while ceilings were low, a non-precision approach would be the order of the day and we expected we’d be doing the LOC BC 26 upon arrival, in spite of the stiff crosswind that would present.
Upon checking in with Minneapolis Center, we were asked which approach we preferred at CWA. We responded that we were planning on the LOC BC 26, but that we’d need to get a little closer to pick up the ATIS and hear which approach was being advertised. When that happened, we were surprised to learn that the localizer utilized for both the ILS 8 and the BC 26 had become inoperative and that the airport was now using the VOR/DME-A approach instead (via the DME Arc and Circle to Land 17). Swell!
Of course, we had the proper equipment onboard to execute the DME Arc entry, the VOR/DME approach itself, and to fly the circling maneuver for landing on Runway 17. We were also technically “proficient” in such
10 • KING AIR MAGAZINE
AUGUST 2016
by Matthew McDaniel
PART 1
procedures as proclaimed by our airline’s documentation stating we’d passed our most recent Proficiency Checks (PCs), which always included non-precision approach and circling procedures. But in normal operations, even back then (in the 1990s), we flew a real VOR approach very rarely, a circling approach even less frequently, and a DME Arc procedure almost never (including during simulator training events). After a thorough approach briefing, I flew the procedure and landed without incident or fanfare. Suffice it to say, the new first officer got more lessons than he’d probably bargained for that day. Not the least of those lessons was understanding the importance of having navigational backups and the skills to utilize them. The 1900s we flew were not equipped with autopilots, but they did have digital flight directors that proved invaluable in such operational circumstances. We made good use of them and other resources when our anticipated navaids for approach to landing became unavailable.
In today’s IFR environment, GPS has become our primary source for enroute navigation, and even terminal navigation for operators lucky enough to have approach certified GPS equipment. WAAS-enabled GPS equipment has added an additional level of GPS capabilities, as well. These awesome navigational tools have made the lives of pilots exponentially easier, but they have not eliminated the need for backup equipment and procedures. Plus, they have complicated matters by introducing multiple GPS failure/downgrade situations that pilots often do not fully comprehend. Plenty of scenarios still exist that would force pilots to disregard their primary navigation systems and, instead, utilize their backup systems for enroute navigation, terminal navigation or both. After all, GPS signals can be degraded or fail for a variety of reasons.
RAIM
Receiver Autonomous Integrity Monitoring (RAIM) is the best predictor of adequate GPS signal strength for