What is airstair door? and what is the role of it?

Question

Going over the door system of an aircraft I faced the following issue: the airstair door is an integral part of a cargo door and should be closed and latched when cargo door is open.

Answer 1

airstairs are mainly used on the crj and erj they use them just in case the jetbridge cant go that low to get the pax on and off.

Answer 2

The Airstair Door is a passenger stairway that is built into a aircraft door.

They are often, though not always, on the inside of a clamshell-style door. The stairs can be raised or lowered while the aircraft is on the ground, allowing passengers and ground personnel to board or depart the aircraft without the need for a mobile staircase or a jetway.

And since you mentioned Cargo Doors.... Sometimes, a manufacturer will combine the Cargo & Airstair Doors. Generally, the Cargo Door is top-hinged and held open with gas springs. When extended, the Cargo Door allows fork lifts or other loading equipment to operate around the aircraft without interference.

The Airstair is a door-within-a-door, and operates normally when the cargo door is closed. Passengers board the aircraft  using the Airstair Door.

Answer 3

Airstairs can mean different things.  In a smaller business class jet, it can be the stairs used to enter the main cabin area, while on a 727 type airframe it is actually the drop down stairwell in the tail of the airplane that maintainers usually use.

Answer 4

It is a door where the airstair is housed. Modern aircrafts design have built airstair that are in the left side of the airplane having in mind quick turn-around of aircrafts (for another flight), while cargo loading, potable water servicing and lavatory servicing is going on passenger can be boarded. All this servicing points are located at the right side of the aircraft. We could even board passenger (with pilots permission) and aside from the airstair another mobile  passenger steps is placed for safety purposes if fuel is still going on.