How Do Aircraft Doors Work?

Passing through an aircraft door represents the start or end of one’s time onboard an aircraft. It can signify the optimism of beginning a new trip, or the excitement of having arrived somewhere new, or welcomingly familiar. To avoid rapid depressurization, it is paramount that these structures cannot be breached inflight. But how exactly do they work?

Air France, Airbus A380, For Sale
Larger aircraft such as the A380 have several doors in order to facilitate prompt boarding and disembarking. Photo: Vincenzo Pace | Simple Flying

How do they work?

According to Ask The Pilot, aircraft doors are held in place physically by “a series of electrical and/or mechanical latches.” This is one way in which they are kept secure despite the strong forces that aircraft encounter inflight. It also minimizes the risk of accidental opening. How aircraft doors open can differ, but the first movement is always one of inward motion.

After this, some will swing to the side, whereas others retract towards or even into the aircraft’s ceiling. However, it is important to note that this only tends to be the case on passenger aircraft. After all, inward-opening cargo doors would reduce the available space for a freight aircraft’s goods. Last month, a DHL Boeing 757’s cargo door opened inflight in Germany, although, thankfully, the aircraft was able to land safely and without injuries to its crew,

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DHL Air Boeing 757 Cargo Plane At Thessaloniki Airport
The nature of a cargo aircraft’s work makes it more advantageous for it to have outward-opening doors. Photo: Getty Images

Why can’t they be opened inflight?

We have established the mechanical means by which aircraft doors are kept shut, but there is another aspect to consider. What is stopping a dangerous individual from opening the door inflight and potentially endangering the lives of the aircraft’s occupants by forcing a rapid decompression? Thankfully, the nature of physics renders this task impossible.

As well as being held in place by its latches, the door is effectively sealed by the pressure difference between the plane’s cabin and the air outside it. The high pressure of the cabin forces the wedge-shaped, plug-like door into its socket. This prevents it from being released until the aircraft is on the ground, where there is not such a pressure difference.

Plug Door Diagram
A diagram demonstrating the phenomena that hold an aircraft’s plug door in place inflight. The grey area represents the aircraft’s highly-pressurized cabin. Image: Acdx via Wikimedia Commons

Stories of accidental opening on the ground

Aircraft doors are designed to be used on the ground, where they are not subjected to the pressure difference found at altitude. Most of the time, flight attendants seamlessly operate these structures. This allows for the prompt dispatch of the plane at one end, and an equally prompt disembarking process at the other.

However, such doors do sometimes find themselves unintentionally open. Sometimes, this seems to happen by itself, as was reportedly the case with a Pakistan International Airlines ATR 42 while landing in Sukkur last year. However, other versions of the story claimed that a passenger had accidentally opened it from the inside.

Aer Lingus Regional ATR72 Dublin
ATR’s turboprop aircraft differ in only having a passenger door at the rear of the aircraft. This structure also includes the plane’s steps. Photo: Jake Hardiman – Simple Flying

Such incidents are rare, but not completely infrequent. Indeed, a similar situation befell another PIA aircraft in 2019. This incident occurred due to a passenger on the 777 mistaking the door for a bathroom while on the ground in Manchester. Because of the accidental emergency slide deployment that followed, the flight ended up being delayed for seven hours.

Did you know how aircraft doors worked? Have you ever witnessed an event in which an unauthorized attend has been made to open one? Let us know your thoughts and experiences in the comments.