Posts Tagged ‘ground proximity warning system’

Practice your crashes

Thursday, November 1st, 2012

I was recently watching a Discovery Channel special about a group of scientists and pilots who decided to crash a Boeing 727 in the Mexican desert in order to better understand what affects survivability versus fatalities in a real-world crash. (Click here for video clips from “Curiosity: Inside a Plane Crash.”—Ed.)

If you get an opportunity to see the show, you should. It made me think of a couple things. First, you can get a 727 for a relatively paltry sum (they paid $425,000 for theirs). Second, it makes me wonder how many people are familiar with the crash landing procedures in their airplanes–specifically jets.

During the experiment, cameras were installed in the cockpit in order to film the crash from that point of view. During the last part of the descent, a female voice can be heard saying, “Falling….falling.” It’s clearly a voice that is tied into either a radar altimeter or a ground proximity warning system (GPWS, pronounced “JIP-WIZ”), and it is this voice that got me pondering thought number two.

Modern aircraft have all kinds of bells and whistles that start making noises under specific circumstances. In this case, it was because the 727 was forced, via remote control, into a descent that was nearly three times the norm, like what might happen if a crew fell asleep. On the CRJ that I flew for Comair, there were a number of warnings that came on at low altitude if certain conditions were not met. They included general terrain or obstacle warnings, gear problems, flap settings, descent rate warnings, and wind-shear warnings.

All of these could be cancelled if the crew—especially the first officer (FO)—knew how. The overrides were primarily intended to help a crew cancel a nuisance message that shouldn’t otherwise be on. The volume level of the warnings is not adjustable. They have one setting: rock-concert-loud. (You know, that whole sleeping-pilot thing.) Unfortunately, any other communication is virtually impossible, so there are switch-lights that can be pushed to cancel the audible warnings. Unfortunately again, the switch is nuclear: It kills everything.

But in an impending crash, that’s good. Most airlines don’t practice full-blown crashes in the sim. However, because I have a morbid sense of humor and a never-ending curiosity, I did it several times. Scenarios that might drive the use of such a checklist could include a total failure of the gear system, loss of fuel, loss of engine power and/or total electric power (think: lightning strike), even an inflight collision with another plane or some of the geese that Sullenburger missed. The crash-landing checklist is several pages long, and I wanted to be familiar enough with it that I could get to the nuts-and-bolts of it quickly if I needed it.

Getting rid of extraneous noise is a major part of minimizing workload when trying to crash-land with a minimal rate of damage and a maximum chance of survival.
If you ever get a chance to do a total crash scenario in a sim, you should, especially with the gear up and in various flap configurations. The airplane does not fly the same, and the speed and control response will vary from what you are used to. Besides, in a worse-case scenario, you want to at least be able to say, “I’ve done this before.” In a safe environment, of course!—Chip Wright