Aerodynamic surface load sensing

• US 4,115,755 A
• Filed: 06/11/1976
• Issued: 09/19/1978
• Est. Priority Date: 06/11/1976
• Status: Expired due to Term

• Current Assignee: United Technologies Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: United Technologies Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Cotton, Lou S.
• Primary Examiner(s): Caldwell, Sr., John W.
• Assistant Examiner(s): Groody, James J.
• Application Number:
  US05/695,501
• Time in Patent Office: 830 Days
• Field of Search: 340/27 R, 340/27 AT, 340/27 SS, 340/407, 244/17.11, 244/17.13, 244/191, 235/150.2, 73/178 H, 73/65, 364/426, 364/424
• US Class Current: 340/946
• CPC Class Codes: G05D 1/0066 for limitation of acceleration or stress

Abstract

The factors (including collective pitch, weight, altitude density, rotor speed and airspeed) which determine the extent to which the rotor of a helicopter may be loaded, are fed into a look-up table, and the permissible acceleration normal to the rotor is compared against actual acceleration normal to the rotor, an alarm signal resulting whenever the actual exceeds the permissive; the alarm signal may be utilized to shake the collective stick so as to simulate pre-overload vibration as a warning to the pilot.

Claims

1. In a helicopter, navigation apparatus comprising:

speed means providing a signal indicative of the airspeed of the helicopter;

means responsive to the output of said speed means for providing a design collective pitch signal indicative of a predetermined collective pitch stick position associated with the particular speed indicated by the output signal of said speed means as a function of the nominal weight of the helicopter, said design collective pitch signal continuously varying with airspeed in a manner according to a predetermined function;

collective pitch stick position sensing means for providing an actual collective pitch signal indicative of the actual position of the collective pitch control stick;

comparison means responsive to both of said collective pitch signals to provide an output weight signal indicative of a relationship of the actual weight of the helicopter to said nominal weight;

barometric altimeter sensing means for providing an altimeter signal indicative of the altitude of the aircraft;

differentiator means responsive to said altimeter signal to provide a hold signal indicating vertical maneuvering of the aircraft, said comparison means being responsive to said hold signal to continuously provide the last weight signal prior to the appearance of said hold signal until said hold signal disappears;

temperature sensing means for providing a signal indicative of the temperature of the atmosphere surrounding the aircraft;

density correction means responsive to said altimeter signal and to said temperature signal for providing a signal indicative of the density of the atmosphere surrounding said aircraft;

rotor speed sensing means for providing a signal indicative of rotor speed; and

means responsive to said collective pitch signal, said weight signal, said airspeed signal, said density signal, and said rotor speed signal for providing a signal in response thereto which is indicative of the aircraft acceleration corresponding to permissible loading of the aircraft within the structural envelope thereof.

2. Apparatus according to claim 1 further comprising:

means including an accelerometer for providing a signal indicative of the actual acceleration in the helicopter; and

means responsive to said permitted acceleration signal and said actual acceleration signal for providing an alarm signal whenever the actual acceleration exceeds the permitted acceleration.

3. Apparatus according to claim 2 further comprising:

means responsive to said alarm signal for shaking the collective pitch stick of the helicopter.

4. Helicopter navigation apparatus comprising:

means including an accelerometer for providing a signal indicative of the acceleration of the aircraft;

a plurality of condition means respectively providing signals indicative of density of the helicopter ambient atmosphere and collective pitch, weight, airspeed, and rotor speed of the helicopter;

means responsive to said condition means for providing a signal indicative of a permitted vertical acceleration corresponding, for all of the conditions represented by said signals, to a rotor load within the structural envelope of said helicopter; and

means for comparing said permitted acceleration signal with said actual acceleration signal to generate a signal indicative of whether or not the actual acceleration exceeds the value thereof related to proper loading of the aircraft within the structural envelope.