Airplanes require the use of specialized, sealed doors, such as plug doors. They are commonly used for boarding. Airplanes will open their plug doors before takeoff so that passengers can enter the airplane and take their seats. Plug doors, however, don’t use a traditional locking mechanism. Here are six interesting facts about plug doors and how they work.
#1) Leverages Pressure Differential
Plug doors work by leveraging pressure differential. They are able to seal themselves by using the pressure difference between the airplane’s cabin and its exterior. Cabin pressure is higher than the pressure outside of an airplane during a high-altitude flight. As an airplane climbs, the pressure differential will increase. The airplane’s plug doors will then seal themselves.
#2) Prevents Accidental Openings
Plug doors are less likely to be opened accidentally than traditional locking doors. As previously mentioned, they leverage pressure differential. And as long as there’s a difference in pressure between the airplane’s cabin and its exterior, the airplane’s plug doors will remain sealed. Passengers and crew members won’t be able to accidentally open them until the pressure has equalized.
#3) Contains Hinges
While their design varies, many plug doors have hinges. Hinges are used to connect plug doors to the fuselage openings in which they are installed. The hinges may allow the plug doors to be opened inward, or they may allow the plug doors to be opened outward. Regardless, most plug doors contain hinges. Hinges attach the plug doors to the fuselage openings while allowing them to rotate either inward or outward.
#4) Not Used for Loading and Unloading Cargo
You typically won’t see plug doors used for loading and unloading cargo. Instead, they are used for passenger boarding. Plug doors are smaller than other, traditional locking doors. Their small size makes them a poor choice for loading and unloading cargo. Furthermore, some plug doors are designed to be opened inward. With this inward-opened design, they consume more space inside the airplane’s cargo hold.
#5) Subject to Regulation
Plug doors are subject to regulation. This is done to ensure their safety and reliability. Regulations for plug doors cover aspects such as structural integrity, usage procedures and operational limitations.
#6) Supports Emergency Evacuations
In addition to passenger boarding, plug doors may be used for emergency evacuations. In the event of an emergency, they will allow passengers and crew to quickly evacuate the airplane. Some plug doors are designed with features such as emergency slides or ramps to facilitate rapid evacuation in case of an emergency.
