Variable load feel

Claim 2

A mechanism to generate control surface feedback forces for an aircraft control system including: primary spring means adapted to be connected to the control system to apply forces thereto which resist movements away from a predetermined position thereof, said primary spring means including means to vary the effective spring rate thereof in correspondence to a first input; secondary spring means including means to vary the effective spring rate thereof in correspondence to a second input and means to vary the preload thereof in correspondence to the second input; and force sensitive means to connect said secondary spring means in series with said primary spring means whenever the force applied by said primary spring means to the control system exceeds the preload of said secondary spring means.

Claim 3

The mechanism defined in claim 1 wherein said primary spring means include: a spring; lever means to operatively connect said spring to the control system; and means to vary the angle between said lever means and said spring to vary the effective spring rate thereof in correspondence to the first input.

Claim 4

The mechanism defined in claim 1 wherein said secondary spring means include: a spring; lever means to operatively connect one end of said spring to said force sensitive means; means to vary the angle between said force sensitive means and said spring to vary the effective spring rate of said spring in correspondence to the second input; and means connected to move the other end of said spring with respect to said one end to vary the preload in said spring in correspondence to said second input.

Claim 5

The mechanism defined in claim 1 wherein a portion of the second input is a function of the first input, said secondary spring means including: means responsive to the first input to vary the effective spring rate thereof in correspondenCe to the first input; and means responsive to the first input to vary the preload thereof in correspondence to the first input.

Claim 6

The mechanism defined in claim 1 wherein the control surface is the elevator control surface, the first input is dynamic pressure and the second input is horizontal stabilizer position which includes elevator effectiveness information, said secondary spring means including: means responsive to the dynamic pressure input to vary the effective spring rate thereof in correspondence to the dynamic pressure; and means responsive to the dynamic pressure input to vary the preload thereof in correspondence to the dynamic pressure, whereby said secondary spring means modify the effect of variations in the effective spring rate of said primary spring means made in response to changes in dynamic pressure.

Claim 7

The mechanism defined in claim 1 wherein said secondary spring means include: a spring; lever means to operatively connect said spring to said force sensitive means; and means to vary the leverage between said force sensitive means and said spring to vary the effective spring rate of said spring.

Claim 8

The mechanism defined in claim 1 including: an actuator responsive to electrical inputs representative of the first input, said actuator having a mechanism output connected to vary the effective spring rate of said primary spring means in correspondence to the first input, said actuator including irreversible means which maintain said mechanical output fixed if said actuator ceases to function.

Claim 9

The mechanism defined in claim 1 wherein said primary spring means include: a first spring having one-half the desired spring rate; a second spring having one-half the desired spring rate; and means to vary the effective spring rates of said first and second springs in correspondence to the first input.

Claim 10

The mechanism defined in claim 1 wherein said secondary spring means include: a first spring having one-half the desired spring rate; a second spring having one-half the desired spring rate; means to vary the effective spring rates of said first and second springs in correspondence to the second input and inversely in relation to the first input; and means to establish and vary the preload of said first and second springs in correspondence to the second input and inversely in relation to the first input.

Claim 11

The mechanism defined in claim 1 wherein the control system can be moved to positive and negative positions from the predetermined position, said mechanism including: output means for connecting said primary spring means to the control system, said output means including means which apply the feedback force generated by said mechanism to resist motion of said control system to both positive and negative positions.

Claim 12

Means for generating artificial feel for the control system of an aircraft including: first means for applying one of a first family of force gradients to the control system; means connected to said first means responsive to inputs representative of the airspeed of the aircraft to control which gradient of the first family is applied to said control system; second means for controllably applying one of a second family of force gradients to the control system; and means connected to said second means responsive to inputs representative of the elevator effectiveness of the aircraft to control which gradient of said second family is applied to said control system and to control the amount of force required to be applied to the control system by said first means before said second family of gradients is applied thereto, whereby said first family of gradients is sufficiently steep to assure stability of the aricraft and said second family of gradients assure that a predetermined force will be applied in opposition to movement of the control system to a position sufficient to cause a predetermined acceleration of the aircraft.

Claim 13

Means for generating artificial feel for the control system of an aircraft including: first means for applying one of a first family of force gradients to the control system; means connected to said first means responsive to inputs representative of the airspeed of the aircraft to control which gradient of the first family is applied to said control system; second means for controllably applying one of a second family of force gradients to the control system; and means connected to said second means responsive to inputs representative of the elevator effectiveness of the aircraft to control which gradient of said second family is applied to said control system and to control the amount of force required to be applied to the control system by said first means before said second family of gradients is applied thereto, whereby said first family of gradients is sufficiently steep to assure stability of the aricraft and said second family of gradients assure that a predetermined force will be applied in opposition to movement of the control system to a position sufficient to cause a predetermined acceleration of the aircraft.