The GPS signal disruption that has affected certain Collins Aerospace GPS receivers has caused flight delays and groundings, in part because some of the affected aircraft do not list GPS on their minimum equipment lists (MEL) or some aircraft require two working GPS receivers to dispatch.
Collins Aerospace confirmed to AIN details of a notice that it sent to customers, which identifies the affected units and aircraft. According to the letter, the affected GPS receivers are the GPS-4000S (P/N 822-2189-100) and GLU-2100 (P/N 822-2532-100). Business jets equipped with the GPS-4000S that are affected include the Bombardier Challenger 300 and 350, 604 and 650, Global 5000 Vision and 6000, Embraer Legacy 450 and 500, Gulfstream G150 and G280, Citation CJ3, and Hawker 800XP. “Other models with the GPS-4000S P/N 822-2189-100 will also be impacted,” Collins said in the letter. Some of the transports reportedly affected include Bombardier CRJs, Boeing 737-900s, and MD11s.
Collins described the problem as follows: “The root cause is a software design error that misinterprets GPS time updates. A ‘leap second’ event occurs once every 2.5 years within the U.S. Government GPS satellite almanac update. Our GPS-4000S (P/N 822-2189-100) and GLU-2100 (P/N 822-2532-100) software's timing calculations have reacted to this leap second by not tracking satellites upon power-up and subsequently failing. A regularly scheduled almanac update with this ‘leap second’ was distributed by the U.S. government on 0:00GMT Sunday, June 9, 2019, and the failures began to occur after this event.”
Collins is recommending that operators contact their aircraft manufacturer “to obtain an MEL or MEL extension if possible. If you have not powered up your units, leave them off until after June 16, 2019, 00:15Z. The next scheduled update by the U.S. Government to the GPS constellation is set for Sunday (June 16) at 00:00Z. We do not believe this update will include time information which triggers this error, however we are testing for impact of this almanac update.”
Gulfstream told AIN that it issued a Maintenance and Operations letter to all G150, G200, and G280 operators, “although not all of the aircraft in those fleets are affected.” Gulfstream does include GPS on its MELs, so those operators can fly using VOR/DME navigation.
Textron Aviation said it is closely monitoring the situation and is recommending the Collins advice not to power up the GPS-4000s or disconnect it from its antenna “to reduce the likelihood of adverse effects to the receiver until more information is available.”
Bombardier issued an advisory letter, telling customers “We are working closely with Collins Aerospace to determine root cause and corrective actions.” The company pointed out that the GPS outage could affect some cabin systems, including entertainment systems and airborne connectivity (satcom and air-to-ground). Bombardier advised operators to “pull the GPS circuit breakers prior to powering up the aircraft to prevent this condition and do not reset until a solution is made available. This may help to return GPS capability sooner when the solution will be available.”
For operators of affected Bombardier aircraft, the company strongly recommends calling Bombardier's Customer Response Center for assistance.