System and method for optimizing horizontal tail loads

Patent metadata

Field	Value
Publication number	US-2016122000-A1
Application number	US-201414278868-A
Country	US
Kind code	A1
Filing date	May 15, 2014
Priority date	May 15, 2014
Publication date	May 5, 2016
Grant date	—

Abstract

A method of controlling an elevator of an aircraft may include identifying a current stabilizer angle of incidence of a stabilizer of the aircraft. The stabilizer may include an elevator pivotably coupled to the stabilizer. The method may further include comparing the current stabilizer angle of incidence with a threshold stabilizer angle of incidence, and selecting an elevator position limit that is more restrictive if the current stabilizer angle of incidence is greater than or equal to the threshold stabilizer angle of incidence. The method may additionally include moving the elevator to a commanded elevator position that is no greater than the elevator position limit.

First claim

1 . A method of controlling an elevator of an aircraft, comprising:
identifying a current stabilizer angle of incidence of an aircraft, the aircraft including a stabilizer and an elevator pivotably coupled to the stabilizer; comparing the current stabilizer angle of incidence with a threshold stabilizer angle of incidence; and selecting an elevator position limit that is more restrictive if the current stabilizer angle of incidence is greater than or equal to the threshold stabilizer angle of incidence.

2 . The method of claim 1 , wherein the selecting of the elevator position limit includes:
selecting an elevator position limit from a first table of a first pair of lookup tables if the current stabilizer angle of incidence is greater than or equal to the threshold stabilizer angle of incidence; and selecting the elevator position limit from a second table of the first pair of lookup tables if the current stabilizer angle of incidence is below the threshold stabilizer angle of incidence.

3 . The method of claim 2 , wherein the elevator position limit is an upper elevator position limit associated with a given airspeed and Mach number, and wherein the selecting of an elevator position limit further includes:
selecting a lower elevator position limit from a second pair of lookup tables, the lower elevator position limit associated with the given airspeed and Mach number and having a magnitude different from a magnitude of the upper elevator position limit.

4 . The method of claim 2 , wherein the elevator position limit is an upper elevator position limit associated with a given airspeed and Mach number, and wherein the selecting of the elevator position limit further includes:
selecting a lower elevator position limit from a second pair of lookup tables, the lower elevator position limit associated with the given airspeed and Mach number; and wherein a magnitude of the lower elevator position limit is greater than a magnitude of the upper elevator position limit if the current stabilizer angle of incidence is negative, and the magnitude of the lower elevator position is less than a magnitude of the upper elevator position limit if the current stabilizer angle of incidence is positive.

5 . The method of claim 2 , further comprising:
generating a plurality of lookup tables including a first pair of lookup tables comprising values for an upper elevator position limit and a second pair of lookup tables comprising values for a lower elevator position limit; and wherein the selecting of the elevator position limit includes selecting a value for the upper elevator position limit from one of the first pair of lookup tables if the current stabilizer angle of incidence is greater than or equal to the threshold stabilizer angle of incidence, and selecting a value for the upper elevator position limit from another one of the first pair of lookup tables if the current stabilizer angle of incidence is below the threshold stabilizer angle of incidence.

6 . The method of claim 3 , wherein the selecting of the elevator position limit further includes:
selecting a value for the lower elevator position limit from one of the second pair of lookup tables if the current stabilizer angle of incidence is greater than or equal to the threshold stabilizer angle of incidence; and selecting a value for the lower elevator position limit from another one of the second pair of lookup tables if the current stabilizer angle of incidence is below the threshold stabilizer angle of incidence.

7 . The method of claim 1 , wherein the threshold stabilizer angle of incidence corresponds to a value below which speed brakes of the aircraft are retracted.

8 . The method of claim 1 , further comprising:
computing the elevator position limit as a function of at least one of Mach number, airspeed, dynamic pressure, and altitude, and based on a threshold stabilizer angle of incidence.

9 . The method of claim 1 , wherein the elevator position limit is a first elevator position limit, the method further comprising:
selecting a second elevator position limit that is less restrictive than the first elevator position limit in response to a determination of a hydraulic system failure.

10 . A system for controlling an elevator of an aircraft, comprising:
a flight control processor configured to receive a stabilizer signal representative of a current stabilizer angle of incidence of a stabilizer having an elevator pivotably coupled to the stabilizer and select an elevator position limit based on the stabilizer signal, wherein the selected elevator position limit is more restrictive if the current stabilizer angle of incidence is equal to or above a threshold stabilizer angle of incidence, and less restrictive if the current stabilizer angle of incidence is below the threshold stabilizer angle of incidence; and an elevator actuator configured to move the elevator to an elevator position that is no greater than the elevator position limit.

11 . The system of claim 10 , wherein the threshold stabilizer angle of incidence corresponds to a value below which speed brakes of the aircraft are retracted.

12 . The system of claim 10 , wherein the flight control processor is further configured to select, for a given Mach number and airspeed, an upper elevator position limit and a lower elevator position limit having a magnitude different from a magnitude of the upper elevator position limit.

13 . The system of claim 10 , wherein for a given Mach number, airspeed, and current stabilizer angle of incidence, the flight control processor is further configured to select another elevator position limit which is less restrictive than the selected elevator position limit responsive to an indication of a hydraulic system failure.

14 . A method of controlling an elevator of a horizontal tail of an aircraft, comprising:
selecting a factor for increasing or decreasing a predetermined horizontal tail load alleviation (HTLA) authority limit for an elevator based on at least one aircraft parameter, the HTLA authority limit decreasing with an increase in Mach number and/or airspeed; computing an elevator position limit as a product of the HTLA authority limit and the factor; and moving the elevator to a commanded elevator position that is no greater than the elevator position limit.

15 . The method of claim 14 , wherein the aircraft parameter is a current stabilizer angle of incidence of a stabilizer of the horizontal tail, the step of selecting a factor for the HTLA authority limit comprises:
selecting a reduction factor based on the current stabilizer angle of incidence.

16 . The method of claim 15 , wherein the step of selecting the reduction factor includes:
decreasing the reduction factor with an increase in the current stabilizer angle of incidence.

17 . The method of claim 14 , wherein the step of selecting a factor for the HTLA authority limit comprises:
calculating a predicted tail load on the horizontal tail with the elevator at a given HTLA authority limit; determining whether the predicted tail load exceeds a load-carrying capability of the horizontal tail; and selecting a reduction factor for the HTLA authority limit based on the Mach number and/or airspeed of the aircraft if the predicted tail load exceeds the load-carrying capability.

18 . The method of claim 17 , wherein the step of selecting the reduction factor for the HTLA authority limit comprises:
selecting a reduction factor based on Mach, airspeed, and current stabilizer angle of incidence.

1

Assignees

• Boeing Co

Inventors

• Mahmulyin Vedad

Classifications

• B64C13/506

  overriding of personal controls; with automatic return to inoperative position · CPC title

• B64C9/00

  Adjustable control surfaces or members, e.g. rudders (trimming stabilising surfaces B64C5/10) · CPC title

• B64C5/02

  Tailplanes · CPC title

• B64C13/505

  having duplication or stand-by provisions · CPC title

• B64C13/16 Primary

  actuated automatically, e.g. responsive to gust detectors · CPC title