Aircraft nose landing gear

Abstract: An aircraft nose landing gear installation that utilizes a single piece pin (100) inserted through the gear fittings and into the two piece, fail safe support structure without requiring mechanical retention on the outside of the wheel well.

Description: Field of the Invention The present invention relates to a nose gear installation and more particularly to a means for securing an aircraft nose landing gear assembly into the nose wheel well support structure of an aircraft. Specifically, the invention relates to an aircraft nose landing gear system as defined in the pre-characterizing part of claim 1. Background Information Prior Art Literature Prior art documents relating to aircraft landing gears do not include many details of the way in which the landing gear is pivotally mounted to the aircraft. For instance, EP-A-0 597 688 discloses a trolley for transporting and positioning a landing gear prior to installation on an aircraft. This document shows that a landing gear is positioned in the wheel well such as to align the fittings or bearings on the landing gear with corresponding bearings in the wheel well structure, after which a trunnion pin or pintle pin is inserted into the bearings. It is summarily stated that the bearings are then secured, without any indication of how this is achieved. US-A-5,337,976 schematically shows a landing gear pivotally mounted to an aircraft structure by means of a pin received in an opening in the structure. There is no indication of any bearing or fitting, nor of the way in which the pin is secured. Prior Nose Gear Systems As can be seen in Fig. 1, in prior commercial transport aircraft, specifically the Boeing 737-300/400/500 type aircraft, a nose landing gear system having the features of the pre-characterizing part of claim 1 is used. The nose landing gear 12 generally consists of a shock strut assembly 10 and drag brace members 20. The shock strut carries the wheels (not shown) and steering mechanism (not shown) and pivots about trunnion pins 30. Bushings 40 located in the side walls of the nose wheel well receive and support the trunnion pins 30. The drag brace members 20 are used to unfold the landing gear and lock it in place when brace members 20 also brace the landing gear against forward and aft loads. The drag brace members 20 are secured to the nose wheel well support structure in a way substantially the same as the way in which the shock strut assembly 10 is secured to support structure. Problems of the Prior Nose Gear Systems The previous way of securing the nose landing gear assembly 12 to the nose wheel well structure is as shown in Fig. 2. The old method employs joints at each of the landing gear support fittings 45 having a spherically mounted self lubricating bearing 50, a cylindrical steel pin 60, and a corresponding cylindrical bushing 70 in the landing gear assembly 12. Also at each joint location, a retaining nut, lock wire and washers (not shown in Fig. 2) are secured to the steel pin on the outboard (pressurized) side of the nose wheel well structure. It is very difficult for a production worker or mechanic to access the outboard side of the nose wheel well at each of the joint locations and install retaining nuts, washers and lockwires. Consequently, the initial installation and subsequent removal and replacement of nose landing gear assemblies is a difficult and time consuming operation requiring considerable skill and effort. Accordingly, there is a need for an improved nose landing gear trunnion pin joint for installation of landing gear assemblies into the nose wheel well that does not require outboard retaining nuts, washers, or lockwires. Such a landing gear assembly would be designed so that a mechanic could install, remove or replace the nose landing assembly without accessing the outboard side of the nose wheel well. Nose landing gear trunnion pin arrangements used in other Boeing aircraft also generally rely on outboard side installed retaining nuts and the like as described above. The Boeing 777 series aircraft, however, use trunnion pins that install only from the inboard side. However, the landing gear support fittings in the nose wheel well of the Boeing 777 are single piece fittings designed to a safe life requirement. The Boeing 737 aircraft disclosed above use two-sided fittings that are designed to a fail safety requirement. These two-sided fittings require an inboard bushing and an outboard bushing and so, because an unrestrained outboard bushing could migrate outboard, trunnion pins were supplied with outboard retaining nuts. Summary of the Invention The present invention has for its object to provide a landing gear trunnion pin joint solving the aforementioned trunnion pin joint problem and to provide for simplified manufacture, installation and removal of the nose gear. In accordance with the present invention, this object is attained by an aircraft nose landing gear system as defined in claim 1. Preferred embodiments of the aircraft nose landing gear system of the invention form the subject matter of dependent claims 2 to 7. Brief Description of the Drawings Fig. 1 is illustrative of a general aircraft nose gear assembly; Fig. 2 is illustrative of the prior method of securing the nose landing gear assembly to the nose wheel well structure; Fig. 3 is illustrative of the eight elements compromising the present trunnion pin joint; Fig. 4 is illustrative in more detail of the relationship of the elements shown in Fig. 3, including the manner in which the retaining clip functions to prevent outward migration of the outboard bushing; and Fig. 5 is a view of the trunnion pin joint from the outside of the nose wheel well. Description of a Preferred Embodiment Turning now to Figs. 3 and 4, it can be seen that the trunnion pin joint 90 according to the present system includes eight basic elements: a trunnion pin 100, a landing gear fitting 110, an inboard nose wheel well fitting 130, a nose wheel well web 135, an outboard nose wheel well fitting 140, an inboard bushing 132 and an outboard bushing 142 and an outboard bushing retention clip 150. Trunnion pin 100 is secured to landing gear fitting 110 by a retention bolt 120 which passes through cylindrical bores in the landing gear fitting (not shown) and corresponding bores in the trunnion pin (not shown). Inboard nose wheel well fitting 130 and outboard nose wheel well fitting 140 are mounted on opposite sides of nose wheel well web 135. As can be seen in the same way, outboard bushing 142 is fitted into an opposite cylindrical bore in outboard nose wheel well fitting 140. Both outboard bushing 142 and inboard bushing 132 concentrically receive trunnion pin 100. Nose wheel well web 135 has an opening adapted to clear trunnion pin 100. As landing gear fitting 110 is fitted up against inboard nose wheel well fitting 130 it is sometimes necessary to add shims 115. Further, both inboard and outboard bushings 132 and 142 have lubrication channels 148 formed in their inside surfaces to allow continuous lubrication of the trunnion pin and bushing surfaces. Lubricant is replenished to these channels through a lubrication fitting 146. Both inboard and outboard bushings 132 and 142 have outer flanges 133 and 149 respectively. Retaining clip 150 clamps down on an outer flange 149 of outboard bushing 142 and prevents it from migrating outboard and away from the trunnion pin joint. Figure 5 is a view of the trunnion pin joint 90 from the outside of the nose wheel well and it shows that retaining clip 150 is secured to outboard nose wheel well fitting 140 by retaining clip bolt 152. Reference numerals utilized in identifying component structure in the aforementioned detailed description: Figs. 1 and 2 landing gear 12 shock strut assembly 10 drag brace members 20 trunnion pins 30 bushings 40 landing gear support fittings 45 self-lubricating bearing 50 cylindrical steel pin 60 cylindrical bushing 70 Figs. 3, 4 and 5 trunnion pin joint 90 trunnion pin 100 landing geaar fitting 110 shims 115 retention bolt 120 inboard outboard nose wheel well fitting 130/140 inboard bushing 132 inboard bushing outer flange 133 wheel well web 135 outboard bushing 142 lubrification fitting 146 lubrification channels 148 outboard bushing outer flange 149 retaining clip 150 retaining clip bolt 152 While a preferred embodiment of the invention has been illustrated and described, variations will be apparent to those skilled in the art Accordingly, the invention is not to be limited to the specific embodiment illustrated and described, and the true scope of the invention is to be determined by reference to the following claims.

Claims: An aircraft nose landing gear system comprising: a nose wheel well structure including a nose wheel well web (135) on each side of the nose wheel well, and a landing gear assembly pivotally mounted in each nose wheel well web (135) by means of at least one trunnion pin joint (90), said trunnion pin joint (90) including a trunnion pin (100), a landing gear fitting (110), at least one nose wheel well fitting (130,140) mounted to the nose wheel well web (135), an inboard bushing (132) and an outboard bushing (142) arranged in said at least one nose wheel well fitting (130,140), and retention means for retaining the outboard bushing (142), characterized in that said retention means include a retaining clip (150). The aircraft nose landing gear system as claimed in claim 1, characterized in that said outboard bushing (142) includes an outer flange (149) and said retaining clip (150) is arranged to clamp down on said outer flange (149). The aircraft nose landing gear system as claimed in claim 1 or 2, characterized in that said retaining clip (150) is secured to said at least one nose wheel well fitting (130,140) by a retaining clip bolt (152). The aircraft nose landing gear system as claimed in any of the preceding claims, characterized by an inboard nose wheel well fitting (130) and an outboard nose wheel well fitting (140) mounted on opposite sides of each nose wheel well web (135), said inboard and outboard bushings (132,142) being symmetrically mounted in said inboard and outboard nose wheel well fittings (130,140), respectively. The aircraft nose landing gear system as claimed in any of the preceding claims, characterized in that said trunnion pin (100) is secured to said landing gear fitting (110) by a retention bolt (120) passing through bores in the landing gear fitting (110) and trunnion pin (100). The aircraft nose landing gear system as claimed in any one of the preceding claims, characterized in that said landing gear assembly includes a shock strut assembly and drag brace members, both said shock strut assembly and said drag brace members being shorter than a space between said nose wheel well webs (135), both said shock strut assembly and said drag brace members having two fittings (110), one at each end thereof, and both said shock strut assembly and said drag brace members being mounted to each nose wheel well web (135) by said trunnion pin (100) passing through one of said shock strut or drag brace fittings (110) and through the corresponding inboard and outboard bushings (132,142), respectively. The aircraft nose landing gear system as claimed in claim 6, characterized by shims (115) closing a gap between said landing gear fittings (110) and said inboard bushings (132).

Inventors: DEPENBUSCH ROGER A, DONG ANNETTE K, SQUIRES THOMAS J, DEPENBUSCH, ROGER A., DONG, ANNETTE K., SQUIRES, THOMAS J.
Applicants: BOEING CO, THE BOEING COMPANY
Application year: 1998
Main classification: B64C25
IPC codes: B64C25