It's never exactly like what you practiced
I worked the after takeoff/climb checklist as the captain flew the published departure procedure, which initially follows the valley west out of San Jose until climbing over the surrounding mountains and then northward toward the United States.
The next checklist in the sequence is for the 18,000-foot transition. Among other checks, it calls for ensuring that crew oxygen masks are plugged in. They were.
A few moments later a yellow light appeared on the annunciator panel. The amber-colored annunciator was easy to see in the darkened cockpit. It read "CABIN ALT 8500 FT," and it meant just what it said--the cabin altitude had reached, and probably surpassed, 8,500 feet. This was highly unusual, because the pressurization system typically kept the cabin altitude well below 8,500 feet. Even at the airplane's maximum operating altitude of 51,000 feet (we've never taken it that high), the cabin altitude is supposed to be 8,000. It should never reach 8,500 feet. Also, I had checked the pressurization controller on the climbout to verify that the cabin was indeed pressurizing.
Before we had a chance to even think about the source of the problem, an extremely loud, high-pitched warning horn began to sound. A few moments later, emergency oxygen masks dropped from the headliner in the passenger cabin, meaning that the cabin altitude had reached approximately 13,500 feet. At the same time, a loud whooshing sound was heard from the rear of the cabin, and the temperature in the cabin and cockpit began to rise--both indications that the emergency pressurization system was kicking in, dumping unconditioned engine bleed air in the cabin and cockpit to prevent the cabin altitude from rising above 13,500 feet.
The captain and I donned our oxygen masks, and I glanced back to make sure our passengers were doing the same. They were--and they sported major deer-in-the-headlights looks.
We attempted to figure out what had occurred--why the cabin was depressurizing. The captain leveled the airplane at about 20,000 feet, and then turned west toward the open Pacific. He didn't want to descend immediately because of the mountainous terrain below.
I set 7700, the emergency squawk code, in the transponder and, using the boom microphone on my headphones, asked Central American Control for a descent and return to San Jose. Once we knew we were being tracked on air traffic control radar, the captain began descending and following the controller's vectors back to Juan Santamaria. We landed without further incident.
In four decades of flying, that was the first time I've had to make an immediate emergency return to the airport. I've experienced serious problems before, including an alternator failure just as I started in on an instrument approach in low clouds at night, but none that had me declaring an emergency.
Even though our emergency did not involve an explosive depressurization, it was dark and pretty chaotic in the cockpit. That warning tone was disorienting, and we fumbled for some critical items--a flashlight, a small red button that silences the cabin altitude warning horn, and the toggle switch to change from headset mic to oxygen mask mic.
Putting the oxygen masks on proved to be difficult enough. Both of us were wearing headsets and reading glasses, and we took them off to put on our masks. Then I had trouble putting my glasses back on over the mask webbing. When I practiced it later, I found it much easier to leave my glasses on when donning the mask.
What I learned from that episode was that the real thing is never quite like the simulated emergencies that are part and parcel of the training you get when earning a type rating in a turbojet (or any airplane with a maximum gross weight of more than 12,500 pounds). Sure, we practiced cabin depressurization emergencies in the simulator, but we knew they were coming. Also, they always occurred at a high cruise altitude (or so the instructor briefed us prior to the event), so that the sudden depressurization was combined with an emergency descent. It was all scripted, especially in comparison with an actual cabin depressurization.
The take-home lesson from our emergency was that, no matter how much you've trained for it, you're never quite prepared for a real emergency. You're bound to make mistakes when responding to an unanticipated problem, but it's also highly likely that you'll do the major things that are required to avoid even bigger problems, and that you'll land safely.
Just how you respond depends on the emergency and the airplane, but a few things never change. First, no matter what has occurred, you must remember to fly the airplane. As strange as it sounds, it's deceptively easy to become so distracted by the noise, confusion, lights, and instrument indications that may accompany an in-flight emergency that you truly forget to fly the airplane. If you do nothing else in an emergency other than fly the airplane, you'll probably be fine. If you do everything exactly right except fly the airplane, the opposite result is guaranteed.
Second on the list of things to do in an emergency is to consult the aircraft checklist. If yours doesn't cover emergency procedures, make sure the pilot's operating handbook (POH) or aircraft flight manual (AFM) is handy and reach for it first. You may think you know what to do if the flaps won't extend on downwind, but for modern aircraft, the checklist/AFM/POH really does know.
Few emergencies require an immediate response, but in the case of an engine failure or fire in a piston-powered airplane, you should have the initial response procedures memorized. If the engine has suddenly gone silent, you have neither the time nor the attention to devote to leafing through a checklist or manual to find out what to do.
Carry a couple of flashlights, make sure the batteries are fresh, and stow the flashlights where they can be reached quickly and easily.
Practice responding to emergencies with a knowledgeable instructor. Though scripted, practice sessions are invaluable in acquainting you with response procedures. If the real thing ever does occur, you'll be way ahead in knowing what resources to call upon and where, and how to work your way through the event safely.
And, finally, don't forget to fly the airplane.
Mark Twombly is a writer and editor who has been flying since 1968. He is a commercial pilot with instrument and multiengine ratings and co-owner of a Piper Aztec.
