US3744928A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Rotor overload protection
Assignee: RTX Corp
•
Filing: 1971-10-07
•
Granted: 1973-07-10
•
Expires: 1991-10-07
Abstract
Abstract Overloading of rotor blades in a vertical lift aircraft such as a helicopter is avoided by limiting blade pitch to a value below that at which permissible loading will obtain. Strain in the blade pitch rods is monitored and used, together with the rate of change thereof as a pitch limit control signal to limit the effect of pilot control on the actual pitch of the rotor blades. In one embodiment, the strain in the rotor pitch push rods is compared against a lower threshold load value, and an excess causes the rate of change of the strain to be utilized as one input to the pitch limiting control signal; the load is also compared to an upper threshold, and an excess causes the actual load to be used as a second input to the pitch limit control signal. The pitch limit control signal in one embodiment is applied directly to the collective pitch outer loop (or major control loop), but is further modified when applied to the longitudinal cyclic pitch outer control loop. The further modification multiplies the limiting signal with air speed and pitch rate to prevent unwanted longitudinal pitch input at low air speeds, particularly as a result of excess commands in collective pitch.
Inventors
- 👤 K Hansen
- 👤 J Mckeown
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 15:35
CPC Classifications
B; B64; B64C; B64C27/00; B64C27/006
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
190 words
Rotor blade load limit control apparatus for a vertical lift aircraft having collective pitch control and longitudinal cyclic pitch control, comprising: load signal means for developing a load signal proportional to the load on at least one blade of the rotor of said aircraft; first means responsive to said load signal means for providing a first signal proportional to the rate of change of load on the blade of said rotor related to said load signal means in response to said load signal being of a magnitude in excess of a lower threshold magnitude; second means responsive to said load signal means for providing a second signal proportional to said load signal in response to said load signal having a magnitude in excess of an upper threshold magnitude; sum means responsive to said first and second means for providing a limit signal as the sum of said first and second signals; and control means responsive to said sum means for altering the operation of said collective pitch control and said longitudinal cyclic pitch control in a manner to reduce the loading on said blades in proportion to said limit signal.
Claim 2
Dependent Claim
190 words
Rotor blade load limit control apparatus for a vertical lift aircraft having collective pitch control and longitudinal cyclic pitch control, comprising: load signal means for developing a load signal proportional to the load on at least one blade of the rotor of said aircraft; first means responsive to said load signal means for providing a first signal proportional to the rate of change of load on the blade of said rotor related to said load signal means in response to said load signal being of a magnitude in excess of a lower threshold magnitude; second means responsive to said load signal means for providing a second signal proportional to said load signal in response to said load signal having a magnitude in excess of an upper threshold magnitude; sum means responsive to said first and second means for providing a limit signal as the sum of said first and second signals; and control means responsive to said sum means for altering the operation of said collective pitch control and said longitudinal cyclic pitch control in a manner to reduce the loading on said blades in proportion to said limit signal.
Claim 3
Dependent Claim
178 words
Rotor blade load limit control apparatus for a vertical lift aircraft having collective pitch control and longitudinal cyclic pitch control, comprising: limit signal means developing a raw limit signal in response to the load on at least one blade of the rotor of said aircraft; speed means for generating a signal proportional to the speed of the aircraft; pitch means for generating a signal proportional to the rate of change of pitch of the aircraft; product means responsive to said limit signal means, said speed means and said pitch means to generate a longitudinal cyclic pitch limit signal as the product of said speed signal, said pitch rate signal and said raw limit signal; and control means responsive to said sum means and said product means for altering the operation of said collective pitch control in response to said raw limit signal and for altering the operation of said longitudinal cyclic pitch control in response to said longitudinal cyclic pitch limit signal, in a manner to reduce the loading on said blades in proportion to said limit signals.
Claim 4
Dependent Claim
178 words
Rotor blade load limit control apparatus for a vertical lift aircraft having collective pitch control and longitudinal cyclic pitch control, comprising: limit signal means developing a raw limit signal in response to the load on at least one blade of the rotor of said aircraft; speed means for generating a signal proportional to the speed of the aircraft; pitch means for generating a signal proportional to the rate of change of pitch of the aircraft; product means responsive to said limit signal means, said speed means and said pitch means to generate a longitudinal cyclic pitch limit signal as the product of said speed signal, said pitch rate signal and said raw limit signal; and control means responsive to said sum means and said product means for altering the operation of said collective pitch control in response to said raw limit signal and for altering the operation of said longitudinal cyclic pitch control in response to said longitudinal cyclic pitch limit signal, in a manner to reduce the loading on said blades in proportion to said limit signals.
Claim 5
Dependent Claim
282 words
Rotor blade load limit control apparatus for a vertical lift aircraft having collective pitch control and longitudinal cyclic pitch control, comprising: load signal means developing a signal proportional to the load on at least one blade of the rotor of said aircraft; first means responsive to said load signal means for providing a first signal proportional to the rate of change of load on the blade of said rotor related to said load signal means in response to said load signal being of a magnitude in excess of a lower threshold magnitude; second means responsive to said load signal means for providing a second signal proportional to said load signal in response to said load signal having a magnitude in excess of an upper threshold magnitude; sum means responsive to said first and second means for providing a raw limit signal as the sum of said first and second signals; speed means for generating a Signal proportional to the speed of the aircraft; pitch means for generating a signal proportional to the rate of change of pitch of the aircraft; product means responsive to said sum means, said speed means and said pitch means to generate a longitudinal cyclic pitch limit signal as the product of said speed signal, said pitch rate signal and said raw limit signal; and control means responsive to said sum means and said product means for altering the operation of said collective pitch control in response to said raw limit signal and for altering the operation of said longitudinal cyclic pitch control in response to said longitudinal cyclic pitch limit signal, in a manner to reduce the loading on said blades in proportion to said limit signals.
Claim 6
Dependent Claim
282 words
Rotor blade load limit control apparatus for a vertical lift aircraft having collective pitch control and longitudinal cyclic pitch control, comprising: load signal means developing a signal proportional to the load on at least one blade of the rotor of said aircraft; first means responsive to said load signal means for providing a first signal proportional to the rate of change of load on the blade of said rotor related to said load signal means in response to said load signal being of a magnitude in excess of a lower threshold magnitude; second means responsive to said load signal means for providing a second signal proportional to said load signal in response to said load signal having a magnitude in excess of an upper threshold magnitude; sum means responsive to said first and second means for providing a raw limit signal as the sum of said first and second signals; speed means for generating a Signal proportional to the speed of the aircraft; pitch means for generating a signal proportional to the rate of change of pitch of the aircraft; product means responsive to said sum means, said speed means and said pitch means to generate a longitudinal cyclic pitch limit signal as the product of said speed signal, said pitch rate signal and said raw limit signal; and control means responsive to said sum means and said product means for altering the operation of said collective pitch control in response to said raw limit signal and for altering the operation of said longitudinal cyclic pitch control in response to said longitudinal cyclic pitch limit signal, in a manner to reduce the loading on said blades in proportion to said limit signals.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-07-09 | 1977-01-08 | 1977-07-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-07-09 | 1981-01-08 | 1981-07-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-07-09 | 1985-01-08 | 1985-07-10 | $7700.00 | Window Closed / Lapsed |