Most airplane failures trigger a chain of defenses designed to keep the flight safe. Checklists, intensive training and decades of experience are supported by multiple redundancies and a robust design.
“It’s the closest that all of us passengers will ever want to get to an air disaster”, confessed, quoted by , a passenger on Qantas flight QF1889 after the plane suddenly dropped to around 6100 meters on September 22, in Australia.
The crew of the Embraer 190 received a pressurization warning, followed procedures and landed normally — but, in the cabin, this rapid descent seemed anything but normal.
The truth is that technical problems in flight like this are part of it. Pilots train extensively for them. Checklists contain detailed instructions on how to deal with each problem. Aircraft are built with layers of redundancy, and warning systems alert pilots to problems. It is because of these safety systems that the vast majority of flights that face technical issues land with a safe arrival and not with tragic headlines.
Eis 4 failures that seem scarywhich we can hear about (and even experience), and how they are resolved in the air.
1. Air conditioning and pressurization problems
What is it?
At cruising altitudes (typically around 11,000 meters), aircraft cabins are maintained at a comfortable “cabin altitude” of around 2,450 meters using air from the engines, which is cooled through the air conditioning system.
This artificial air pressure allows us to survive while the atmosphere outside the plane is highly hostile to human life, with temperatures around -55°C and no breathable air. However, if the system behaves anomalously or if the cabin altitude begins to rise for any reason, crews treat it as a potential pressurization problem and immediately begin preventive procedures.
What can you feel/see?
A quick and controlled descent (it may seem dramatic), clicking in the ears and, sometimes, oxygen masks (these usually fall automatically only if the cabin altitude exceeds approximately 4270 meters). As with flight QF1889, a rapid descent without deploying the masks is the most common outcome.
What do pilots do?
As soon as they notice a cabin pressurization problem, pilots put on their own oxygen masks, declare an emergency and follow the emergency descent checklist, bringing the plane as quickly as possible to about 3050 meters. This is normally followed by a diversion landing or a return to the origin airport.
2. The most feared: engine failures
What is it?
Twin-engine commercial airplanes are certified to fly safely with just one engine. Still, engine failures are treated seriously and practiced thoroughly in flight simulators at least once a year.
Double faults, however, are exceptionally rare. In 2009, for example, it was a once-in-a-generation bird strike event that caused both engines to stop. The plane landed safely in the Hudson River, in New York, without any fatalities.
What can you feel/see?
A loud bang, vibration, sparks coming from the engine, a burning smell or a sudden silence. This may result in an immediate return and reception by emergency services.
What do pilots do?
After being alerted by the warning system, pilots identify the affected engine and follow the checklist. The list typically requires them to shut down the problematic engine, descend to an appropriate altitude and divert the flight if they are cruising, or return to the home airport if it is after takeoff.
Even when an engine failure damages other systems, crews are trained to manage cascades of warnings.
3. Hydraulic and flight control problems
What is it?
An airplane’s multiple flight controls move thanks to hydraulic or electrical systems. If one of these systems misbehaves (for example, if the left wing aileron, used to turn the plane, does not move), redundancy keeps the plane controllable because the right wing aileron will continue to function.
Crews use specific checklists and adjust speeds, distances and landing configurations to ensure a safe return to the ground.
What can you feel/see?
A longer wait while the crew analyzes the problem, a return to the home airport or a quicker landing than normal.
What do pilots do?
After the problem is detected by the warning system, pilots go through the checklist, decide the landing configuration, request the longest suitable runway and request the presence of emergency services as a precaution.
All of these resources are available because lessons learned from extreme events have been incorporated into modern aircraft design and training programs.
4. “Drama” in the landing gear and braking system
What is it?
Commercial planes have retractable landing gear that stays inside a compartment for most of the flight. These are the wheels that come out of the belly of the plane before landing. Brakes are integrated into the tires, whose function is to reduce the aircraft’s speed after it touches the ground, just like a car.
With so many moving parts, sometimes the landing gear does not extend or retract correctly, or the braking system loses some effectiveness, for example due to the loss of a hydraulic system.
What can you feel/see?
A pre-emptive return, preparation of the cabin for a possible forced landing, or “impact position” instructions given by the cabin crew immediately before landing may occur.
Although scary, these are preventative measures in case something doesn’t go as planned. Earlier this year, a Qantas flight returned to Brisbane (Australia) after experiencing a problem with the landing gear; passengers were instructed to keep their “heads down” while the plane landed safely.
What do pilots do?
They follow long checklists and eventually contact maintenance engineers to diagnose the problem. There are also redundant systems for lowering the landing gear and applying the brakes.
In extreme cases, they may be forced to land on the longest runway available (in case of brake problems) or to land on their belly (if the landing gear cannot even be lowered).
Overview
Most in-flight failures trigger a chain of defenses designed to keep the flight safe. Checklists, intensive training and decades of experience are supported by multiple redundancies and a robust design.
These flights usually end like the aforementioned QF1889: safely on the ground, but, in fact, with passengers a little shaken.
A dramatic descent or an urgent landing does not mean disaster. They usually mean that the safety system (aircraft + crew + checklist + training + redundancy) is doing exactly what it is supposed to do.
