by Bill Richards

A three-engine wide-body air carrier aircraft climbing to flight level 410 experienced a compressor stall and had to shut down an engine just prior to level off. The flight crew "...advised center [that they were] descending, [had] shut down an engine, and need[ed] 24,000 feet."

The controller cleared the stricken aircraft for a descent to flight level 370, but the flight crew "...advised twice we had to get down [to yet a lower altitude]." Due to traffic at flight level 350, the controller was unable to approve their request, and so stated. The flight crew kept repeating their request for lower (altitude) and the controller kept repeating that he was "unable."

Controller's Dilemma

It is well publicized that air carrier aircraft will fly very well with one and, in some cases, two engines shut down. What is not made clear is that this is not true at higher altitudes such as thirty-seven thousand feet, thus it is possible that the controller did not realize the urgency of the need for a lower altitude. It is, however, more likely that the controller fully understood the seriousness of the flight crew's situation, but the controller's hands were tied.

An air traffic controller's primary function is to maintain certain minimum separation standards between aircraft. The controller was undoubtedly trying to provide the requested descent clearance as quickly as possible, but until he could clear traffic from below the troubled aircraft, the flight could not be issued a clearance to descend. An air traffic controller cannot issue a clearance that will result in a loss of standard separation, but can and will provide assistance in the form of traffic point-outs and/or recommendations intended to increase separation between conflicting traffic.

Meanwhile, the flight crew had lost control of their airplane. Minus the power of the failed engine, they were descending and there was nothing they could do to prevent it. This was certainly an emergency situation, yet the crew never declared an emergency. The controller was finally able to vector the traffic out of the way and to clear the stricken aircraft for a continued descent, but by this time the aircraft had already descended slightly below flight level 370.

Emergency

I won't speculate why the flight crew didn't declare an emergency; however, they may have neglected to properly assess the effect of their descent on other traffic in the vicinity and thus ATC's potential difficulty in maintaining traffic separation. Given the declaration of an emergency, the controller could have pointed out conflicting traffic to all involved, and provided traffic advisories even though a loss of standard separation might result from the flight crew's actions.

A Different Twist

In another incident, a trans-Atlantic wide-body aircraft was forced to descend and reverse course after shutting down an engine. The flight crew advised the Center controller of the nature of their problem, requested a lower altitude, and stated they wanted to return to their departure airport. They made their situation, intentions, and altitude capability very clear. They also declared an emergency, but for some reason, Center did not acknowledge their declaration of an emergency. The crew began the "Contingency Procedure," announcing their intentions in the blind to all other traffic. Center was "...a bit slow at re-clearing us back towards [the departure airport] thereafter."

Upon changing to the next Center sector an hour later, the flight crew discovered that Center was treating the whole thing as a routine change of destination and that "no emergency existed in the ATC view." In this case, no apparent conflicts arose. It can only be assumed that had Center understood that an emergency had been declared, their service would have been much more prompt. As with all ATC/aircraft communications, if a flight crew is not sure that a transmission or request has been properly understood, they should repeat their message and make sure that they receive a proper acknowledgment. In this instance, the fact that the flight was over water and using high frequency (HF) radio surely added to the breakdown in communications. Nonetheless, the flight crew must share the responsibility for accuracy in the information exchange.

The Pilot's Toolbox

There seems to be great reluctance among pilots to declare an emergency. It is not uncommon for reporters to the ASRS to indicate that they believe that declaration of an emergency will bring the wrath of the FAA down upon them and cause them innumerable hours of tedious paperwork. FAR 91.3(c) states that "Each pilot-in-command who deviates from a rule under paragraph (b) of this section shall, upon the request of the Administrator, send a written report of that deviation to the Administrator." In most cases, the Report of Irregularity that the Captain has already written for his company supervisors should provide all the information the FAA might need, and no further paperwork would be required.

When determining if an emergency condition exists, flight crews need to consider the implications of their potential inability to conform to ATC instructions. Emergencies should not be frivolously declared, of course, but declaring an emergency is something in the pilot's "toolbox" that can be put to use if it is needed. Don't overlook it.