Airline flight controls

Sophisticated computerized systems control virtually every aspect of a modern airplane and pilots must spend years of extensive training to master them. The safety of people on board and on the ground depends solely on pilots’ training.

 

Computers can’t solve every problem. They serve only as a tool for pilots to use and cannot substitute for pilots. Aviation history has proved that a single pilot mistake or computer malfunction can be responsible for a tragic accident.

Usually, flights run smoothly, but pilots must always be prepared for unforeseen circumstances. The following stories illustrate the importance of proper training for airline pilots.

Flying Blind

In 1996 Aeroperú Flight 603 was scheduled to fly from Jorge Chávez International Airport in Lima, Peru to Santiago, Chile. The aircraft was the safe and reliable Boeing 757—a new generation of passenger plane controlled by on-board computers.

Minutes after take-off, flight instruments began behaving randomly and pilots were puzzled. Contradictory emergency messages on altitude and air speed from the onboard computers prompted the crew to declare an emergency and request an immediate return to the airport

Without computers to guide them, pilots can choose to manually fly a plane. But this flight was at night over water, with no visual references to inform pilots of their true altitude. They were flying virtually blind.

On its return to Lima, the plane experienced multiple stalls resulting in a rapid loss of altitude, though flight instruments did not register any change. While the computer indicated an altitude of approximately 9,700 feet, the aircraft's true altitude was in fact much lower.

Once the pilots believed that they were at a safe altitude they began their descent, approaching the airport relying solely on information from ground control. But the crew still did not have the guidance they needed. Approximately 25 minutes after the emergency was declared, the airplane crashed in the water killing all 70 people on board.

Recovered wreckage revealed that the airplane’s pitot tubes—instruments attached to the external fuselage—were covered with tape. Pitot tubes measure a variety of factors such as altitude, air pressure, and speed, and send this data to the onboard computer. Tape rendered the tubes incapable of relaying correct information.

Shortly before Flight 603’s scheduled departure, the aircraft underwent maintenance service. It is standard procedure to tape pitot tubes to prevent them from being damaged or clogged during maintenance, but servicemen forgot to remove it afterward.

This unfortunate accident gave us a deadly lesson on how dependent pilots have become on the automated on-board computer systems to fly modern commercial jets—and how hopeless they have become when these systems malfunction.

So pilots should not always rely too much on automation. They need to develop a clear understanding of who is behind the controls of the airplane at all times if something does not go as planned. They also need to know that if such a problem does arise, how to identify it and not allow the situation to deteriorate.

Through flight simulation pilots are exposed to the worst possible scenarios. Simulators force pilots to deal with problematic situations without endangering lives. Should these difficult circumstances arise in an actual flight, simulators give pilots the necessary skills to handle them, and to make the right decision at the right time.

But that was not the case with the crew of China Airlines Flight 006 in 1985. It was a daily non-stop flight from Taipei to Los Angeles International Airport. Some 350 miles northwest of San Francisco one of the four engines of the Boeing 747 servicing the flight failed.

Problems with Autopilot

While the crew was working to solve the problem the autopilot (AP) was flying the plane. The autopilot (AP) is an on-board computer system designed to maintain stable flight.

Since the failed engine was on the right wing the left side had more power, causing the plane to bank to the right. The AP on this particular type of aircraft doesn’t control the rudder—a device used to steer the airplane attached to the back of the airplane tail. So the AP responded by using the ailerons—hinged controls attached to the edge of the wing—in an attempt to stabilize the plane and keep it flying straight. However, the ailerons alone weren’t enough to compensate for the turning machine.

The captain of the flight decided to disengage the AP and fly the large plane manually. But as soon as the AP was switched off the plane plunged toward the ground with tremendous force, diving 30,000 feet in only two minutes.

Luckily, the captain was able to recover the plane from this rapid dive just moments before crashing into the Pacific Ocean. The flight was diverted and landed safely at San Francisco International Airport.

How could the failure of one engine throw this flight out of control? The cockpit voice recorder revealed that in being preoccupied with the flamed-out engine and efforts to restart it, the crew forgot that the AP of this aircraft doesn’t control the rudder. With the caption’s decision to disengage the AP, there was nothing left to keep the plane flying straight.

This almost fatal incident, caused by the captain failing to control the plane, revealed how much he trusted automation. He was not able realize who was in command of the machine at that moment.

Today, pilots have to pass simulator tests for in-flight engine failure or shutdown. They have to demonstrate proficiency to cope with such circumstances, should they arise.

For an airplane to be out of fuel is such a rare event that most pilots will never face it during their professional careers. But when it happens, they will need all of their knowledge acquired during simulations to land the plane safely.

AirplaneAll Systems Gone

In the unlikely event of an all-engine failure, the plane lacks not only thrust, but also the electricity necessary to power the sophisticated instruments in the cockpit.

In the event of power loss, a small ram air turbine deploys underneath the fuselage. This is basically a small propeller that is activated through wind power, providing a limited energy supply to vital plane systems. When a plane loses its engines it can still remain airborne, and the air turbine makes it controllable.

In 2001, Flight 236 was en route from Toronto, Canada to Lisbon, Portugal when the plane ran out of fuel over the Atlantic Ocean. The skilled flight crew managed to successfully glide the powerless plane and land safely in the Azores.

Thankfully, most pilots do not have to face such harrowing circumstances. However, flight simulations give all pilots the chance to investigate and learn from a variety of scenarios. Airplane computers have made flying more predictable and dependable, but pilots must still be prepared for anything.