Category : General
By Ofonime Essien
Six minutes before touchdown, Eastern Air Lines Flight 212, a McDonnell Douglas DC9 with 78 passengers and four crew members on board, was descending toward runway 36 at Charlotte, North Carolina, U.S.A. Because patchy dense fog hid the runway from view, a very high frequency omnidirectional radio range (VOR) distance measuring equipment (DME) non-precision instrument approach was being flown. During the approach, the flight crew discussed politics, used cars and the nation’s economic uncertainty.
Related: Crash of the Century
Two minutes prior to touchdown, the conversation switched to trying to identify a local amusement park that the aircraft had just passed. Shortly after receiving landing clearance, the captain remarked to his first officer, “Yeah, we’re all ready. All we got to do is find the airport”. Three seconds later the aircraft impacted terrain 3.3 miles (5.3 kilometers) short of the runway. Seventy two people were killed in the 1974 accident.
Fourteen years later, in 1988, the flight crew of Delta Air Lines Flight 1141, a Boeing 727, spent 17 minutes chatting with a flight attendant in the cockpit while taxing for departure at the Dallas-Fort Worth (Texas, U.S.) International Airport. During the two minutes between the flight attendant’s departure from the cockpit and the initiation of take-off roll, the flight crew started the Nr. 3 engine and conducted the before-take-off checklist. In their haste to prepare for departure, the crew apparently failed to set the flaps for take-off, an omission that was not identified during the crew’s checklist recital. Seven seconds after take-off rotation, the aircraft’s stall warning system activated. Seconds later the aircraft plunged to the ground. There were 15 fatalities and 26 serious injuries.
The U.S. National Transportation Safety Board (NTSB) determined that poor cockpit discipline played a role in each of these accidents. In its investigation of the DC 9 accident at Charlotte, the NTSB stated that the crew’s non-pertinent conversations “were distractive and reflected a casual mood and lax cockpit atmosphere which continued throughout the remainder of the approach and which contributed to the accident”. In the Dallas-Fort Worth accident, the NTSB said that “had the captain exercised his responsibility and asked the flight attendant to leave the cockpit or, as a minimum, stopped the non-pertinent conversations, the 25-minute taxi time could have been used more constructively and the flap position discrepancy might have been discovered”.
Sterile cockpit simply means limiting conversation to matters pertaining to the flight during critical phases of flight. This means sticking to running checklists, performing takeoff, approach and landing briefings, clarification of taxi and takeoff clearances etc.
The cockpit of an aircraft during taxi-out or approach is neither the time nor the place for non-flight related conversations. Numerous accidents and serious incidents have occurred when flight crews diverted their attention from the tasks at hand and engaged in activities unrelated to flying.
The departure (taxi, takeoff, departure) and arrival (approach, landing, taxi) periods are critical phases of flight that involve high workload for flight crew. Distracting the flight crew with non safety related issues during these periods, can lead to the omission of important tasks such as obtaining clearances to cross active runways, the correct read back of altitude restrictions and the correct completion of checklist actions.
Why do we maintain a sterile cockpit during critical phases of flight? Very simply, there’s a lot of “stuff” going on. If we maintain a sterile cockpit we minimize the chances of “missing” important items – taxi clearances, checklist items etc. These omissions can and do lead to accidents. Can a single pilot violate the sterile cockpit rule? Absolutely! If you find yourself thinking about things not related to the flight (football matches, politics etc.) during a critical phase of flight, you are not maintaining a sterile cockpit.
In the airline and corporate aviation world, aircrews are usually mandated with maintaining a sterile cockpit below 10,000 feet MSL. Critical Phase of Flight starts with the pre-flight checklist and ends with completion of the cruise checklist on the departure leg of a flight. It also begins with the In-Range checklist and ends after completion of the engine shutdown/secure checklist on the arrival leg of a flight. For local practice area flights where we are constantly on the lookout for traffic, one could easily argue that all phases of the flight are “critical.”
A historical analysis of aircraft accidents has revealed that most occur during the takeoff and landing phases of flight. While these two phases of flight represent only 4% of journey time, they correspond to 70% of all aircraft accidents (Flight Safety Digest, 1994).
Situations That Warrant Sterile Cockpit Interruptions
- Fire, burning odor or smoke in cabin;
- Medical emergency;
- Unusual noise or vibration;
- Auxiliary power unit (APU) torching;
- Fuel or other fluid leakages;
- Exit door unable to be armed/ disarmed;
- Extreme temperature change;
- Evidence of de-icing problems;
- Suspicious, unclaimed bag or package;
- Cart stowage problem; and,
- Any other condition that seems abnormal or that a flight attendant believes the flight crew should know about.
Situations That Do Not Warrant Sterile Cockpit Interruptions
- Non safety-related logbook items;
- Meal references;
- Gate information;
- Misconnected baggage;
- Catering problems;
- Passenger accommodations such as wheelchairs; and,
- Rude passengers.
This list, along with appropriate regulatory requirements, provides a starting point for guidelines, which can be modified to suit the needs of each operator.
Sterile Cockpit Procedures
The sterile cockpit concept recognizes that flight operations other than routine cruise flight are intrinsically more hazardous and require the undivided and vigilant attention of all crew-members. The Pilot in Command (PIC) is responsible to ensure that non-essential conversations, activities, and otherwise distracting actions do not occur during critical portions of flight. Critical portions of flight are taxi, takeoff, climb, descent, landing, and operations in high-density traffic areas or heavy ATC periods.
a. The PIC will ensure that all crew-members and passengers are aware of this requirement by conducting a crew and passenger briefing prior to boarding the aircraft or prior to engine start. The “Sterile Cockpit” brief can be as simple as a general statement by the PIC indicating that an announcement will be made when the flight is in a critical phase of flight, or possibly, a detailed briefing of the various phases of flight that are considered busiest and critical for the crew-members to avoid distractions.
b. The PIC will include in the “Sterile Cockpit” brief a statement that safety of flight items are always appropriate to be brought to the immediate attention of the PIC. Safety concerns would be such items as potentially conflicting traffic, potential mechanical problems with the aircraft, i.e., electrical smoke or smoke of an unknown origin, leaking fuel, etc.
c. Instructors will conduct training in this procedure as part of any initial or recurring flight training. Check pilots will ensure that all pilots, as part of their mission pilot and normal proficiency flight checks, complete a “Sterile Cockpit” briefing.
NON-COMPLIANCE LEADS TO ACCIDENTS AND SERIOUS INCIDENTS
Although the sterile cockpit has enhanced aviation safety, it is difficult to estimate the number of accidents and serious incidents that it has prevented. Where non-compliance has led to accidents and incidents, the unfortunate results are obvious. Delta Flight 1141 is one such example.
The FAA noted: “Extraneous conversation in the cockpit during critical phases of flight causes crew distraction in small as well as large aircraft”. The accident and incident records send a clear message: aviation safety can be enhanced by using sterile cockpit procedures.