Plane Answers: A closer look at technology in the Northwest overflight

According to the NTSB, the co-pilot was more familiar with the new bidding system, called preferential bidding, which involves choosing the types of trips and the day and time of departures in a general sense instead of simply picking a month of flying from the company constructed bid sheet.



Preferential bidding takes some time to get used to, and the pilots who figure it out early are likely to enjoy an advantage for a few months over those who don't. The co-pilot was simply trying to get the captain up to speed, and this apparently was enough of a distraction to cause the crew to lose contact with ATC for well over an hour.

Missed signs

Media reports have suggested that the pilots missed repeated calls from the company and that 'bells and chimes' were sounded as the company and ATC desperately tried to contact the flight.

Those descriptions aren't entirely accurate. When the company tried to contact the pilots via ACARS there wasn't actually a chime associated with the message. There was simply a 1/4 inch tall notice on one of the forward displays on the instrument panel that a message has been received. There was no AOL style "You've got mail!" chime. Some airplanes also print any message automatically on a small and rather quiet printer.

Losing contact with air traffic control is something that can happen to any pilot. A missed radio call is followed up by another call or two before the center switches to the 121.5 emergency frequency that pilots monitor on a second radio. If both attempts fail, ATC will then call another aircraft of the same airline to have them relay a message through ACARS for the airplane to re-establish contact on whatever frequency is in use.

If no contact is made, the chatter on the radio suddenly stops, so instead of hearing bells, chimes and calls, the Northwest pilots likely heard nothing at all. Similar to parents of toddlers, pilots should recognize this ominous silence as a possible problem.

They could have received a VHF SELCAL, a tone loud enough to make you jump out of your seat if activated by ATC. However, I suspect it wasn't used in this case, since it was a similar flight attendant call that eventually led to the discovery of the gross error.

On a related side note, a small number of the airplanes I fly do have a chime sound that activates when an ACARS message is sent. But that chime is identical to the flight attendant chime, the route uplink chime, the winds uplink chime, the HF SELCAL Chime, etc... In the future, ATC instructions sent via CPDLC will even use this same chime. It becomes easier to disregard or miss those particular chimes when they're constantly being used to announce other unimportant or nuisance notices.

The Boeing engineer in charge of designing this system explained to me years ago that humans were unable to differentiate the meaning of more than five different sounds, so they elected to keep those chimes the same and rely on an added cue such as a light or message that tells the pilots what the chime represents.

Will it happen again?

Congress is already talking about measures to restrict laptops in the cockpit. These rules were already in place, and may serve only to remove the official uses of a computer, requiring pilots who currently use a Class I EFB to go back to carrying nearly twenty pounds of books in their kitbags again; a move that still won't prevent some pilot from pulling out a laptop to check their schedule.

I'll leave you with a look at the Class II EFB that Virgin America uses on their flights. Eliminating these tools would be a step backward for the industry.







Do you have a question about something related to the pointy end of an airplane? Ask Kent and maybe he'll use it for the next Plane Answers. Check out his other blog, Cockpit Chronicles and travel along with him at work.