Aeronautics and astronautics – Aircraft structure – Airfoil construction
Patent
1983-09-29
1987-05-26
Blix, Trygve M.
Aeronautics and astronautics
Aircraft structure
Airfoil construction
244 87, B64C 318
Patent
active
046679057
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
The invention relates to a horizontal and vertical stabilizer for use as a part of an empennage.
2. Background Art
One type of conventional vertical or horizontal stabilizer for large aircraft is comprised of three spars and many ribs and stringers. The primary bending loads are carried by stressed skins, and stringers inside thereof, in an after torque box, spaced fore and aft between a front spar and a rear spar. The ribs, extending fore and aft, stabilize the skin and stringers to prevent buckling and provide load paths for concentrated transverse loads such as horizontal stabilizer pivot and elevator hinges.
This structure is fail-safe, designed for a two bay crack; that is, it stops cracks along the skins in the fore and aft direction between three stringers, which typically comprise a distance of about ten inches. The foregoing type of stabilizer has the disadvantages of being relatively heavy because of the substantial number of stringers required and of the inefficiency of buckling skin between stringers.
A minimum weight design for horizontal and vertical stabilizer structures has been obtained with the use of honeycomb sandwich construction in which the skin is 100% non-buckling. One type of sandwich is made of aluminum inner and outer skins and an aluminun honeycomb core and another type has been made with graphite epoxy skins and a non-metal core. These honeycomb sandwiches are used to eliminate the stringers and some of the ribs. However, where the stringers are eliminated, the structural arrangement requires the addition of two intermediate spars, between the front and rear spars, solely for fail-safe design to act as crack stoppers in the outer stabilizer skins. In this arrangement the length of the crack size is somewhat greater than in the conventional stabilizer using stringers, as referred to above. However, the two additional intermediate spars have been found to take away much of the weight savings provided by the honeycomb structure used between the ribs and spars.
A search of the patent literature illustrates other airfoil support structures. For example, U.S. Pat. No. 1,809,913 discloses an airplane wing employing a plurality of spars arranged in a fan-like shape in conjunction with ribs arranged at varying distances from each other. These spars are positioned at varying distances from each other along the transverse axis of the airfoil and the ribs are positioned at varying distances along the longitudinal axis of the airfoil. The outer ends of the spars are secured to the leading and trailing edges, the tip, and the ribs of the airfoil, whereas the inner ends of the spars are secured to the root portion of the fan. This construction allows the spars to be grouped in proximity within the zone of center pressure travel, and permits the trailing edge, weakened by the cut out portion for the aileron to be suitably supported and strengthened by the spars shown at 12b.
The arrangement allows the ribs 13a, adjacent the path of the lateral center pressure travel, to be grouped in proximity to each other thus adding strengthening qualities to the airfoil along the lateral position of the resultant lift load. A grouping of the ribs may be employed close to the root portion 11 as shown by the ribs 13b so that the wing may be adequately supported from the fuselage.
French Pat. No. 962,428 shows spars fanning outwardly and trailing rearwardly so that some of the spars terminate in the outboard end of an airfoil and other of the spars tend to terminate adjacent the trailing edge of the airfoil. The ribs extend across the airfoil and are slightly varied in spacing and the spaces slightly increase outboardly.
U.S. Pat. No. 3,436,038, shows spars, FIG. 5, extending from a support point A. Some of the spars extend forwardly to a leading edge 60 and other of the spars extend outboardly to an end rib. The spacing of the ribs is varied, decreasing outboardly.
The following patents disclose various airfoil structures: U.S. Pat. No. 2,410,056, U.S. Pat. No. 2,593,714, U.S
REFERENCES:
patent: 1809913 (1931-06-01), Semmes
patent: 1835532 (1931-12-01), Semmes
patent: 2031662 (1936-02-01), Mercier
patent: 2410056 (1946-10-01), Fresco
patent: 2593714 (1952-04-01), Robinson
patent: 2997262 (1961-08-01), Kirk et al.
patent: 2998947 (1961-09-01), Griffith
patent: 3109614 (1963-11-01), Steidl
patent: 3436038 (1969-04-01), Parsons et al.
patent: 3910531 (1975-10-01), Leomand
Hamm Robert A.
Soudak Uri
Blix Trygve M.
Corl Rodney
Heberer Eugene O.
The Boeing Company
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