Bifold stair system for aircraft
A stairway for aircraft is disclosed which includes first and second stair halves, one which nests in the other. The first half is hinged to the doorway and the second half is hinged to the first half. A mechanical resistance system uses different devices to allow for the airstair to be damped when switching between modes. A retracting arrangement is also disclosed.
1. A stairway for an aircraft, comprising:
a first portion of the stairway having a stair side with a first plurality of steps, wherein a first end of the first portion is hingeably pinned to one end of a doorway frame on the aircraft;
a second portion of the stairway having a stair side with a second plurality of steps, wherein a first end of the second portion is hingeably connected to a second end of the first portion;
a plurality of mechanical resistance mechanisms incorporated to decelerate relative motion between both (i) the first portion relative to the doorway frame, and (ii) the first portion relative to the second portion, comprising:
a primary damper which is attached at one end to a location on the aircraft above the stairway and attached at another end to an upper location on the first portion of the stairway, the primary damper biasing the stairway towards a stowed configuration; and
one or more secondary dampers disposed on a backside of the first portion to damp during deployment and in stowing of the stairway, wherein the one or more secondary dampers bias the stairway towards the stowed configuration to provide resistance against a rotation of the second portion relative to the first portion of the stairway; and
wherein, in the stowed configuration:
the second portion of the stairway and the plurality of mechanical resistance mechanisms are housed entirely within a fuselage of the aircraft; and
a side of the first portion of the stairway which does not include the steps has an angled wall surface that fits a contour of a fuselage wall.
2. The stairway of claim 1 , wherein in the stowed configuration, the first portion and the second portion are configured to comprise a nested configuration wherein the first plurality of steps fit together with the second plurality of steps.
3. The stairway of claim 2 , wherein the first plurality of steps and the second plurality of steps nearly abut in the stowed configuration.
4. The stairway of claim 3 , wherein in the nested configuration, the first plurality of steps and the second plurality of steps are concealed from all view.
5. The stairway of claim 3 , wherein when in the stowed configuration, the first and second portions are substantially parallel.
6. The stairway of claim 1 , wherein the side of the first portion which does not include the steps and a side of the second portion which does not include the steps are exposed when the stairway is stowed.
7. The stairway of claim 1 , comprising a retracting mechanism wherein the retracting mechanism is operatively connected to the second portion of the stairway, and the retracting mechanism is configured to allow a user to deploy or stow the stairway.
8. The stairway of claim 7 , wherein the retracting mechanism includes an actuating knob which is operatively connected to a reel by a wire, and when the knob is pulled the reel is released which pulls the second portion atop the first portion.
9. The stairway of claim 8 , wherein the reel is a clock spring system.
10. The stairway of claim 7 , comprising:
a front cable and an aft cable, both attached to the aircraft above the stairway, and connected to opposite sides laterally of the first portion proximate a hinge that connects the first portion to the second portion.
11. The stairway of claim 1 , wherein the primary damper, and each of the one or more secondary dampers, are a spring strut, a gas strut, or a hydraulic damper.
12. The stairway of claim 1 , wherein the first portion is hingeably connected to the second portion by a hinge system, the hinge system including a biasing arrangement which biases the second portion to rotate upwards and over the first portion when the stairway is deployed.
13. The stairway of claim 12 , wherein the biasing arrangement includes at least one torsion spring mounted about the hinge system and is configured to create the bias of the second portion to rotate upwards and over the first portion when the stairway is deployed.
14. The stairway of claim 1 , comprising a user actuatable retracting mechanism wherein the user actuatable retracting mechanism is operatively connected between the aircraft and the second portion of the stairway, and the retracting mechanism is configured to allow a user to deploy or stow the stairway.
15. The stairway of claim 1 , wherein the plurality of mechanical resistance mechanisms includes a first damping arrangement between the doorway frame and the first portion, and a second damping arrangement between the second portion and the first portion.
16. The stairway of claim 1 , further comprising:
a plurality of bumpers, mounted on at least one of the stair side of the first portion or the stair side of the second portion, wherein the plurality of bumpers are configured to reduce impact forces between the first portion and the second portion during a closing operation.
17. The stairway of claim 16 , wherein each of the plurality of bumpers further comprise:
a lever portion;
a base portion; and
an internal gap located between the lever portion and the base portion, wherein compression of the lever portion gradually reduces the internal gap and increases a resistance force provided by the plurality of bumpers.
18. The stairway of claim 3 , further comprising a magnetic securing system mounted to the first portion of the stairway and the second portion of the stairway, which secures the first portion and the second portion together while in the stowed configuration.
19. The stairway of claim 18 , wherein a connection strength of the magnetic securing system is configured to prevent accidental disengagements between the first portion and the second portion, without disrupting user's ability to deploy the stairway manually.
20. An aircraft stair arrangement for a doorway of an aircraft, the arrangement comprising:
a first portion of a stair pinned and hinged at a proximate end to one end of a doorframe in the doorway;
a second portion of the stair hinged to a distal end of the first portion of the stair;
a step side of the first portion being nestable into a step side of the second portion when the second portion is rotated onto the first portion; and
a mechanical resistance system incorporated to damp a deployment of the first and second portions from the doorway, comprising:
a primary damper which is attached at one end to a location on the aircraft located above the first portion and attached at another end to an upper location on the first portion, the primary damper biasing the first portion towards a stowed configuration; and
one or more secondary dampers disposed on a backside of the first portion to damp during deployment and in stowing of the first and second portions, wherein the one or more secondary dampers bias the second portion towards the stowed configuration to provide resistance against a rotation of the second portion relative to the first portion; and
wherein, in the stowed configuration:
the second portion and the mechanical resistance system are housed entirely within a fuselage of the aircraft; and
a side of the first portion which does not include steps has an angled wall surface that fits a contour of a fuselage wall.