Saturday, July 14, 2012

TOO LOW! TERRAIN!


No, Pete, it wasn't a water quantity circuit breaker, wise guy, but you're on the trail.

We were descending through flight level 200 when the GPWS (Ground Proximity Warning System) burst forth with its blaring admonition: TOO LOW! TERRAIN!

The flight manual is clear about this warning. When you get it you will execute the CFIT escape maneuver. It doesn't say check altitude (we did). It doesn't say look out the window to see if there are rocks about to rise up and smite you (we did). It doesn't say discuss whether this could be a false warning. (We didn't, but our facial expressions to each other effectively communicated that idea).

Oh yes, CFIT=Controlled Flight into Terrain, a highly imprudent maneuver.

The escape maneuver? A harrowing max power 20 degree deck angle climb.

So, what goes through my mind as this dire harbinger of our impending gloom pounds our eardrums? TOO LOW! TERRAIN! How can anything go through your mind when you are being shouted at except for the shouts? And, ironically, that's the whole point of designing the GPWS to shout.

I knew our altitude was 20,000 feet. I knew the mountains we were over were less than 10,000 feet, and even if I was wrong about our geographical location, I knew there were no mountains in the Lower 48 states that are over 14,500 feet. Of course I could have been wrong about which continent I was over, and that may have happened once or twice in my career. But one thing was certain, I was not going to execute the escape maneuver and scare the hell out of 185 people as well as put the engines through a torturous spool-up. I deviated from the flight manual. Broke a prime rule. Knew it. I nodded to Chris to just continue our descent. TOO LOW! TERRAIN!

As the powerful shouts from our speakers pounded our ears I threw off my belts and got out of the seat. I saw Chris speaking into the microphone. He was shouting to NORCAL Approach Control. “SAY AGAIN, PLEASE!” He couldn't understand their transmissions. I knew the flight attendants sitting on their jumpseats right behind the cockpit could hear the GPWS warnings; knew they were probably expecting to meet the maker at any moment. I knew even the passengers in first class could hear it. TOO LOW! TERRAIN!

The warnings were eating at our concentration and causing us to miss radio calls. Even NORCAL and every other aircraft on the frequency could hear the GPWS when Chris keyed the mic. A lot of people perhaps thought they were hearing an aircraft about to crash. TOO LOW! TERRAIN!

I groped for the correct circuit breaker. There are a gazillion of them on that overhead panel. I crouched behind the pilot seats and swept my eyes across the vast field of the tiny little knobs that looked like long lines of tiny toy soldiers standing in formation, with some itsy bitsy lettering below each one identifying it. I spotted the radio altimeter breakers. YES! Those must be it! I pulled them, knowing very well I had broken my second prime rule: Thou shalt not pull any circuit breakers unless directed to do so by thy maintenance facility. I pulled them. It didn't work. TOO LOW! TERRAIN!

I glanced out the windshield. There was SFO off in the distance. I heard Chris shout into his mic, “FIELD AND BRIDGE IN SIGHT!” Now I felt like Slim Pickens in that unforgettable scene in Dr. Strangelove where the B-52 copilot yells, “TARGET IN SIGHT. WHERE THE HELL IS MAJOR KONG?” Kong is standing atop a hydrogen bomb fiddling with electrical circuits. “I'll git these bumb bay doors open if it hair-lips everybody on Bear Creek.” TOO LOW! TERRAIN!

I kept searching. Chris shouted back at me. “WE'VE GOT TO CONFIGURE!” He was right. It was time to stop chasing errant circuit breakers, get ready to land and endure the deafening warnings. Then I spotted it—the GPWS circuit breaker. I pulled it. TOO LOW! TERR

Blessed silence. I clammored back into my seat. Chris made a perfect landing, we taxied in and shut down, and tried to calm the nervous people near the cockpit who had braced for their violent demise.

That night I spent much time on my laptop filling out incident reports, including my decision to declare “Captain's Emergency Authority” (CEA) for not executing the escape maneuver and pulling the circuit breakers without permission.

The company must self-report these types of deviations to the FAA . The Feds will review it. CEA will afford me immunity unless they think it was blatantly unwarranted. No news will be good news.

While I wait for the “no news” I'll craft the next Decision Height post to tell you about what happened the very next day. It was deja vu (all over again). But worse.

(Stay tuned, Fatquiver.)

And watch how coolly Major Kong handles these things:


He didn't file his reports.

8 comments:

Cedarglen said...

Hello Alan. I doubt that you will hear anything from FAA about you excercise of CEA, or even do any Carpet Dance time with your supervising pilots. I'll look forward to the next post, but what I really want to know is, What was the root cause of that errant "TOO LOW, TERRAIN!" warning. One must know thy systems, I'm sure that you have learned the cause and I hope that y ou do not leave your many readers begging for too long. Best wishes, -C.

Alan Cockrell said...

We had that plane a day or two later and the log history showed that they ran some tests and could not duplicate the problem.

Cedarglen said...

Ouch!

whick said...

Hehe..i'll bet it smelled bad in first class!..whew..Whick

Anonymous said...

And friend of mine was flying a 767 in cruise crossing the Atlantic when the GPWS went off. The cause was another aircraft passing below triggering the radar altimeter.

Justin Bachman said...

Captain-
Curious if you had Channel 9 open with any tower discussion on this shouting so some curious people up front may have heard they were not about to plow into Northern Calif at 450 knots? I must say, as a passenger I really enjoy having 9 available (and I hope the majority of your colleagues do as well.)

Best,
JB

Anonymous said...

Captain-
Curious if you fellows had Ch. 9 open with any tower discussion about said aircraft shouting... folks up front at least would have learned they were not about to plow into a Northern CA mountain at 450 knots.

As a passenger, I must tell you I really enjoy having Ch. 9. It's a wonderful differentiating factor for the company and great for us aviation geeks in back.

--JB

Alan Cockrell said...

JB, yes ch. 9 was on because a first class passenger had requested it. We considered turning it off after the warnings started but decided to leave it on for the reason you suggested. If things get scary we are always ready to turn it off.