The sterile cockpit

June 1, 2000

A sterile cockpit has nothing to do with the cleanliness of the physical environment. It has everything to do with a pure mental environment. As pilots, we pride ourselves on the ability to multitask. Doing several things at once, though, may mean that something important falls through the cracks.

Obviously, distractions lead to accidents. It happens every day in nonaeronautical pursuits. A contemporary example is the use of handheld cellular telephones while driving. The tedium of driving makes it seem like the perfect time to get something else done — to multitask. Many recent studies indicate a strong correlation between using cell phones and the increased probability of a crash because of distraction.

There are similarities in aviation. The concept of the sterile cockpit has been around for decades and got its start in the airline community. Intuitively, most people know when they're busy and distractions are noticeable. We can improve our safety record significantly by reducing distraction.

One accident that forced the issue of sterile cockpits onto center stage occurred nearly 12 years ago. A Boeing 727 was planning a departure out of Dallas. The flight was delayed for about 20 minutes from the time it left the ramp until cleared for takeoff. During at least part of this time, the crew discussed a variety of nonoperational topics among themselves and a flight attendant.

The crew reported that the takeoff roll appeared to be normal, with no warning lights or unusual engine instrument indications. The captain stated that the rotation was initially normal but said the aircraft then began to "roll violently." The Boeing struck the ILS localizer antenna approximately 1,000 feet from the end of the runway and came to rest about 3,200 feet from the end of the runway. In the subsequent fire, the aircraft was destroyed and 14 occupants died because of smoke inhalation and burns.

The NTSB determined that the wing flaps and slats were not properly configured for takeoff. The required flap setting was 15 degrees, but the investigation showed that no flaps or slats were extended. On many light aircraft, failing to set the flaps will decrease the performance — but is not usually a "killer" item. In large aircraft like the 727, it is critical. The numbers are revealing. According to the NTSB, "At normal takeoff speeds, at a body angle of 10 degrees with 15 degrees of flap, the accident airplane would have 53,106 pounds of lift available in excess of the weight of the airplane. With the flaps up (zero degrees of flap), the airplane would weigh 984 pounds more than the lift produced."

There was another factor in this accident. The Boeing 727 is equipped with a takeoff warning system to advise the crew when the aircraft is improperly configured for takeoff. The system is activated when thrust lever No. 3 is advanced beyond a certain point. A takeoff warning horn will sound when outboard trailing edge flaps are set at less than five degrees. There was no evidence on the cockpit voice recorder that the warning horn sounded, and in the post-crash inspection the system worked intermittently.

The NTSB determined that the probable cause was the captain's and first officer's inadequate cockpit discipline, which resulted in an attempt to take off without flaps and slats properly configured, and the failure of the take-off configuration warning system. According to the NTSB report, contributing factors were the airline's slow implementation of improved operating procedures regarding crew checking and lack of aggressive action by the FAA to correct known procedural deficiencies.

FAR 121.542 prohibits cockpit activities not related to safe flight operation during critical phases of flight. As identified in the FAR, they include: all ground operations involving taxi, takeoff, and landing, and all other flight operations below 10,000 feet except cruise flight. Activities such as eating, nonessential conversation between crewmembers or other personnel, and reading the newspaper are forbidden.

In our single-pilot cockpits there is plenty to keep us occupied. When the work load is light it may be perfectly fine to have a casual conversation. Takeoff and landing are obviously busy times but as we have seen from the above, distraction even during taxi can lead to major problems. There is much emphasis on ground operations these days. Runway incursions occur when pilots are not paying attention. Failure to follow ATC instructions is the number-one cause of runway incursions for GA pilots. In most cases, the pilot was distracted. It might even have been for a good operational reason, such as setting up the GPS or configuring the aircraft. In some cases, nonpertinent conversation caused just enough mental wandering to miss a hold-short line.

After the Dallas accident, NASA psychologists revealed some interesting human factor observations of flight crews in simulators. From the NTSB report: "Highly effective crews tended to have much more task-oriented communication, and there was an information acknowledgement sequence." Translating from techno-speak, I believe this means that the effective crews remained focused and used a standard demand-response system, even to the point of using specific words.

Since we do not usually have cockpit doors to retreat behind in small aircraft, the pilot in command has to exercise some discipline. Passengers and even other pilots, despite good intentions, can be significant distractors. In our exuberance to fly, the discipline is sometimes forgotten. This doesn't mean you have to be "the great stone face" throughout the flight. It does mean getting the priorities straight.

Pilots, sometimes acting as flight attendants and tour guides, will self-distract. The predeparture briefing that includes seat belt and exit procedures should also include the ground rules for talking during busy times. You may have time to give a brief explanation of what you're doing while you're doing it. This is helpful for new passengers, but don't get too detailed when you're busy. If there is more curiosity than time will allow, explain that you'll get back to them. We do that socially and professionally on many occasions.

On a recent ILS down to minimums, my passenger commented on a variety of topics while I was busy with minor details such as intercepting the localizer, slowing down the airplane, and putting the wheels down. A quick reminder that silence was golden at that moment allowed us to complete the approach uneventfully.

However, there will be times when a passenger will ask a very useful question like, "Is that airplane over there supposed to be that close?" or "Does this little ol' red light mean anything?" Those can be "operationally pertinent" and should not be ignored. To paraphrase Ecclesiastes, there is a time to speak and a time to be silent. Keep the cockpit sterile and your thoughts pure.


See also the index of "Safety Pilot" articles, organized by subject. Bruce Landsberg is executive director of the AOPA Air Safety Foundation.