A Theoretical Investigation of Longitudinal Stability of Airplanes with Free Controls Including Effect of Friction in Control System

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The relation between the elevator hinge moment parameters and the control forces for changes in forward speed and in maneuvers is shown for several values of static stability and elevator mass balance. The stability of the short period oscillations is shown as a series of boundaries giving the limits of the stable regions in terms of the elevator hinge moment parameters. The effects of static stability, elevator moment of inertia, elevator mass unbalance, and airplane density are also considered. Dynamic instability is likely to occur if there is mass unbalance of the elevator control system combined with a small restoring ... continued below

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Greenberg, Harry & Sternfield, Leonard January 1, 1944.

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This report is part of the collection entitled: National Advisory Committee for Aeronautics Collection and one other and was provided by UNT Libraries Government Documents Department to Digital Library, a digital repository hosted by the UNT Libraries. It has been viewed 27 times . More information about this report can be viewed below.

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  • Main Title: A Theoretical Investigation of Longitudinal Stability of Airplanes with Free Controls Including Effect of Friction in Control System
  • Series Title: NACA Technical Reports

Description

The relation between the elevator hinge moment parameters and the control forces for changes in forward speed and in maneuvers is shown for several values of static stability and elevator mass balance. The stability of the short period oscillations is shown as a series of boundaries giving the limits of the stable regions in terms of the elevator hinge moment parameters. The effects of static stability, elevator moment of inertia, elevator mass unbalance, and airplane density are also considered. Dynamic instability is likely to occur if there is mass unbalance of the elevator control system combined with a small restoring tendency (high aerodynamic balance). This instability can be prevented by a rearrangement of the unbalancing weights which, however, involves an increase of the amount of weight necessary. It can also be prevented by the addition of viscous friction to the elevator control system provided the airplane center of gravity is not behind a certain critical position. For high values of the density parameter, which correspond to high altitudes of flight, the addition of moderate amounts of viscous friction may be destabilizing even when the airplane is statically stable. In this case, increasing the viscous friction makes the oscillation stable again. The condition in which viscous friction causes dynamic instability of a statically stable airplane is limited to a definite range of hinge moment parameters. It is shown that, when viscous friction causes increasing oscillations, solid friction will produce steady oscillations having an amplitude proportional to the amount of friction.

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  • Accession or Local Control No: 96N71470
  • URL: http://hdl.handle.net/2060/19960024284 External Link
  • Report No.: AD-A301267
  • Report No.: NACA-TR-791
  • Center for AeroSpace Information Number: 19960024284
  • Archival Resource Key: ark:/67531/metadc279589

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National Advisory Committee for Aeronautics Collection

The National Advisory Committee for Aeronautics (NACA) was a U.S. federal agency founded on March 3, 1915 to undertake, promote, and institutionalize aeronautical research. On October 1, 1958 the agency was dissolved, and its assets and personnel transferred to the newly created National Aeronautics and Space Administration (NASA).

Technical Report Archive and Image Library

This selection of materials from the Technical Report Archive and Image Library (TRAIL) includes hard-to-find reports published by various government agencies. The technical publications contain reports, images, and technical descriptions of research performed for U.S. government agencies. Topics range from mining, desalination, and radiation to broader physics, biology, and chemistry studies. Some reports include maps, foldouts, blueprints, and other oversize materials.

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Creation Date

  • January 1, 1944

Added to The UNT Digital Library

  • March 30, 2014, 6 p.m.

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  • July 11, 2017, 2:19 p.m.

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Greenberg, Harry & Sternfield, Leonard. A Theoretical Investigation of Longitudinal Stability of Airplanes with Free Controls Including Effect of Friction in Control System, report, January 1, 1944; (digital.library.unt.edu/ark:/67531/metadc279589/: accessed November 17, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.