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What’s New: A NASA report of an airliner Captain who refused to believe he could safely fly the ocean without GPS. He also refused to believe his receiver was being jammed and insisted it had failed.
Why It’s Important: The human element is often overlooked when we talk about systems, but it is always so crucial. – The only reason we have systems is to serve people!
What Else to Know:
- It is difficult for people to deviate from their normal patterns of behavior.
- It can also be difficult for people to overcome their pre-conceived ideas, even when others provide information to the contrary.
- Extreme examples: Pilots have crashed airplanes because they believed a faulty instrument reading. They have also crashed airplanes because they refused to believe an instrument reading. – The human element can make or break an emergency.
Part 121 – GPS Navigation
From a Dispatcher’s report: I received a SATCOM call from the Captain, who informed me they were having issues with the left GPS, and it wasn’t functioning properly. The aircraft kept going into DME DME Mode, and his Actual Navigation Performance (ANP) value was going up and was currently at 15 miles. [I] explained to them that the area they were in was a known GPS Jamming area (Bulgaria/Romania/Serbia). The Captain did not believe this was the case and continued his explanation…why he thought it wasn’t jamming and it was, indeed, the GPS unit going out, even though I told him that this same flight a week ago had GPS jamming happen in the same area. I got aircraft [Technicians] involved, and they stated they couldn’t find anything wrong with the GPS. After hearing this, the Captain still wasn’t convinced that it was GPS jamming and kept insisting it was a faulty GPS unit. He then proceeded to say he couldn’t [fly] the Atlantic crossing with an ANP value of 15 and one GPS unit down. I assured him he could, as I was reading from the circle of entry chart. I told him all that is needed since he was on a random route was VHF, VOR, DME, ADF, and Mode C. He didn’t believe me and instructed me to do my research and get back to him before he started the crossing, which was over 2 hours away. He was adamant that if I couldn’t provide him with sufficient information on why he can still do the crossing, he was going to divert.… At this point my relief stepped in, and I briefed him on the situation. He said he would research it.
The crew refused to listen to Dispatch and did not believe Dispatch that they were in a known area for GPS jamming. Train crews to know the signs of GPS jamming and the areas where it happens frequently.
