Multiple instrument failure on a 777?

I didn't say it was likely!

 

If you don't have any navigation, why would your transponder work?

The only reason you would lose all of your navigation and communication would be a total electrical failure, and in that case the transponder wouldn't work as well.

Although I do agree with the cell phone thing. And most modern cellphones and iPads could even give you a moving map, if you were really desperate.

A more interesting question is what would happen with a total failure of the GPS system-- not the one in the airplane, but the satellites themselves. A lot of displays would go blank or freeze up in that case... it would get very interesting in the IFR system.

Many, many years ago, I filed a flight plan from the northwest to Santa Monica, CA. I wasn't sure about the routing, so I filed direct Avenal or someplace, direct. Our company check airman happened to be hanging around that day while I was doing this, and he asked me what I would do in the case of lost communications.

I laughed and said something about having two radios, two generators, two transponders, etc etc. Not to mention a cell phone! What are the odds of losing communication with all that?

So, we get down into LA Center's airspace, still driving along toward Avenal at FL250, and guess what? Center has a communications failure. Not us-- our equipment was fine. The ATC Center... the guys on the other end!

We had to scramble around (along with everyone else in that section of the sky) to figure out a different frequency, get in touch, tell them who and where we are and why we're calling... by the end of all this, we were still at FL250 about 50 miles out of Santa Monica! Fortunately, turboprops are good at descending.

The moral of the story is that sometimes a failure can happen regardless of how much redundancy you have on your end.

 

In addition to moving map on the iPAD you could also have ADS-B and AHRS.

Are there any battery back-up requirements on electronic flight displays in transport category airplanes? On the Aspens in my old Mooney I had 1hr+ of battery time, plus a panel mounted Garmin 496 which would revert to battery, plus Foreflight on the iPAD with GPS. Navigation in the event of an aircraft electrical failure was the least of my worries, and I also carried a ICOM transceiver (with VOR capabilities).

 

No ADS-B unless you have either a separate ADS-B receiver or internet service.

Yes, of course there are battery back ups. Generally the main displays themselves don't, but all transport category aircraft have at least a third, battery backed up, attitude indicator, and the modern thing is to have a little EFIS display with attitude and compass which is battery backed up.

They also have certification requirements for how long the main batteries have to power essential systems, etc. Some aircraft also have emergency battery back up for other things-- for example, the Learjets have an emergency battery which not only powers the standby gyro but also the gear and flap solenoids.

 

Which is why I said "could".