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Curiously, the design community does not use this first principals analysis to do the
design. Probably the analysis is not complete enough for actual design.
Abramson, H. Norman, An Introduction to the Dynamics of Airplanes, Dover
Publications, New York, 1971. pp. 134-139. This is the book that led me to the Flügge
reference. Some other references are also cited.
von Mises, Richard, Theory of Flight, Dover Publications, New York, 1959, pp. 483-488.
This is another, slightly different, basic analysis of the landing impact problem.
C.8 Historical (pre 1970) and Miscellaneous
Liming, R. A., “Analytic Definition of a Retractable Landing Gear Axis of Rotation,”
Journal of the Aeronautical Sciences, January 1947, pp. 19-23.
McBrearty, J. F., “A Critical Study of Aircraft Landing Gears,” Journal of the
Aeronautical Sciences, 16th IAS Annual Meeting, Proceedings, May 1948, pp. 263-280.
McBrearty, J. F. and Hill, D. C., “Landing Gear Strength Envelopes,” Journal of the
Aeronautical Sciences, IAS Los Angeles Meeting, Proceedings, May 1948, pp. 229-234.
Russell, A.G., “Some Factors Affecting Large Transport Aeroplanes with Turboprop
Engines,” Journal of Aeronautical Sciences, Vol. 17, No. 2, Feb. 1950, pp. 67-122.
Carter, K.S., “The Landing Gear of the Lockheed SST,” SAE Paper 650224, 1965.
150
Stanton, G., “New Design for Commercial Aircraft Wheels and Brakes,” AIAA Paper 67-
104, June 1967.
Ridha, R. A., “Minimum Weight Design of Aircraft Landing Gear Reinforcement Rings,”
AIAA Paper 68-328, March 1968.
Collins, R. L. and Black, R. J., “Tire Parameters for Landing Gear Shimmy Studies,”
AIAA Paper 68-311, April 1968.
Firebaugh, J. M., “Estimation of Taxi Load Exceedances Using Power Spectral
Methods,” Journal of Aircraft, Vol. 5 No. 5, September 1968, pp. 507-509.
46
Chapter 6 Kinematics
6.1. Introduction
Kinematics is the term applied to the design and analysis of those parts used to retract
and extend the gear [2]. Particular attention is given to the determination of the geometry of
the deployed and retracted positions of the landing gear, as well as the swept volume taken
up during deployment/retraction. The objective is to develop a simple
deployment/retraction scheme that takes up the least amount of stowage volume, while at
the same time avoiding interference between the landing gear and surrounding structures.
The simplicity requirement arises primarily from economic considerations. As shown
from operational experience, complexity, in the forms of increased part-count and
maintenance down-time, drives up the overall cost faster than weight [5]. However,
interference problems may lead to a more complex system to retract and store the gear
within the allocated stowage volume.
Based on the analysis as outlined in this chapter, algorithms were developed to
establish the alignment of the pivot axis which permits the deployment/retraction of the
landing gear to be accomplished in the most effective manner, as well as to determine the
retracted position of the assemblies such that stowage boundary violations and structure
interference can be identified.
6.2. Retraction Scheme
For safety reasons, a forward-retracting scheme is preferable for the fuselage-mounted
assemblies. In a complete hydraulic failure situation, with the manual release of uplocks,
the gravity and air drag would be utilized to deploy and down-lock the assembly and thus
avoid a wheels-up landing [2]. As for wing-mounted assemblies, current practice calls for
an inboard-retraction scheme which stows the assembly in the space directly behind the
rear wing-spar. The bogie undercarriage may have an extra degree of freedom available in
that the truck assembly can rotate about the bogie pivot point, thus requiring a minimum of
space when retracted. As will be illustrated in the following section, deployed/retracted
47
position of the landing gear, as well as possible interference between the landing gear and
surrounding structures, can easily be identified using the mathematical kinematic analysis.
6.3. Mathematical Kinematic Analysis
A mathematical kinematic analysis, which is more effective and accurate than the
graphical technique, was selected to determine the axis of rotation that will, in one
articulation, move the landing gear assembly from a given deployed position to a given
retracted position. As shown in Fig. 6.1, a new coordinate system, termed the kinematic
reference frame here, is defined such that the origin is located at the respective landing gear
attachment locations with the axes aligned with the aircraft reference frame. The aircraft
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