Method for operating a landing gear system

Abstract

The present disclosure refers to a method for operating a landing gear system, preferably in a tricycle configuration, wherein main landing gear (MLG) and the nose landing gear (NLG) are operable from a retracted position where they are housed respectively inside landing gear bays, to a fully extended position where they are extended for landing the aircraft. According to the disclosure, the extension of the nose landing gear (NLG) is delayed in time with respect to the extension of the main landing gear (MLG), and the nose landing gear (NLG) is kept retracted during a major part of the time that the main landing gear doors (MLGD) are extended. In this manner, vibrations on the main landing gear doors are reduced and incidents caused by fatigue are also reduced, which in turn implies that the maintenance cost of the aircraft is greatly reduced.

Claims

1. A method for operating a landing gear system for an aircraft, the landing gear system having a main landing gear arranged at a central section of an aircraft, a nose landing gear arranged at a forward section of the aircraft, and main landing gear doors, comprising: operating the main landing gear and the nose landing gear from a retracted position where the main landing gear and the nose landing gear are housed inside respective landing gear bays, to a fully extended position where the main landing gear and the nose landing gear are deployed for landing the aircraft; operating the main landing gear doors from a retracted position to a fully extended position, and delaying, in time, at least one of the extension of the nose landing gear with respect to the extension of the main landing gear, and the retraction of the main landing gear with respect to the retraction of the nose landing gear.

2. The method according to claim 1, wherein the extension of the nose landing gear is started after the beginning of the extension of the main landing gear.

3. The method according to claim 2, wherein the extension of the nose landing gear is started once the main landing gear has reached the fully extended position.

4. The method according to claim 2, wherein the main landing gear doors are retracted after the main landing gear has reached the fully extended position, and wherein the extension of the nose landing gear is started before the beginning of that retraction of the main landing gear doors.

5. The method according to claim 2, wherein the main landing gear doors are retracted after the main landing gear has reached the fully extended position, and wherein extension of the nose landing gear is started after the beginning of the retraction of the main landing gear doors.

6. The method according to claim 2, wherein the extension of the nose landing gear is coordinated with the extension of the main landing gear doors, such that the extension of the nose landing gear is less than 50% of the fully extended position, when the main landing gear doors start a closing movement.

7. The method according to claim 2, wherein the extension of the nose landing gear is coordinated with the extension of the main landing gear doors, such that the extension of the nose landing gear is less than 10% of the fully extended position, when the main landing gear doors start a closing movement.

8. The method according to claim 1, wherein extension of the nose and main landing gear is started at the same time, but the nose landing gear is extended at a slower angular speed than the main landing gear, thereby delaying in time the extension of the nose landing gear with respect to extension of the main landing gear.

9. The method according to claim 1, wherein retraction of the nose landing gear is started while the main landing gear doors are kept in a retracted position.

10. The method according to claim 9, wherein during the retraction operation, once the nose landing gear has reached less than 10% of the fully extended position, the extension of the main landing gear doors is started.

11. The method according to claim 1, wherein the operation of the landing gears includes two modes of operation with an associated control system, wherein one mode is for normal operation with delayed operation between the nose landing gear and the main landing gear and the other mode is for abnormal operation in which all landing gear falls by gravity in case of emergency.

12. A method for operating a landing gear system for an aircraft, the landing gear system having a main landing gear arranged at a central section of an aircraft, a nose landing gear arranged at a forward section of the aircraft, and main landing gear doors, comprising: operating the main landing gear and the nose landing gear from a retracted position where the main landing gear and the nose landing gear are housed inside respective landing gear bays, to a fully extended position where the main landing gear and the nose landing gear are deployed for landing the aircraft; operating the main landing gear doors from a retracted position to a fully extended position, and delaying, in time, at least one of the extension of the nose landing gear with respect to the extension of the main landing gear, and the retraction of the main landing gear with respect to the retraction of the nose landing gear, wherein the main landing gear and the nose landing gear are arranged to form together a tricycle landing gear configuration.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) Preferred embodiments of the disclosure are henceforth described with reference to the accompanying drawings, in which:

(2) FIGS. 1A and 1B are illustrations representing the traditional time sequence for extending the nose and main landing gear and corresponding landing gear doors of an aircraft according to the prior art. In particular, FIG. 1A is a schematic representation of the traditional time sequence, where the nose landing gear is shown at the left side of the FIG. 1A in a side view, and the main landing gear is shown at the right side of FIG. 1A as a front view from the nose of the aircraft. FIG. 1B is a graph representing the angular position with respect of time, of the nose and main landing gears, and the angular position of the nose and main landing gear doors during an extension sequence according to the prior art and in correspondence with FIG. 1A;

(3) FIGS. 2A and 2B are examples of an extending time sequence according to an aspect of the present disclosure, where the angular position 0 represents the fully retracted position of the respective landing gear and landing gear doors;

(4) FIGS. 3A and 3B are illustrations representing the traditional time sequence for retracting the nose and main landing gear of an aircraft according to the prior art. In particular, FIG. 3A shows a schematic representation of the traditional time sequence where the nose landing gear is shown at the left of FIG. 3A in a side view, and the main landing gear is shown at the right side of FIG. 3A as a front view from the nose of the aircraft. FIG. 3B is a graph representing the angular position with respect of time, of the nose and main landing gears, and the angular position of the nose and main landing gear doors during a retraction sequence according to the prior art and in correspondence with FIG. 3A; and

(5) FIGS. 4A and 4B are examples of a retracting sequence according to an aspect of the present disclosure, where the angular position 0 represents the fully retracted position of the respective landing gear and landing gear doors.

DETAILED DESCRIPTION OF THE PRESENT DISCLOSURE

(6) An exemplary embodiment of the method for operating a landing gear (LG) system according to the disclosure, and in particular for extending or lowering the landing gear, is represented in FIGS. 2A and 2B, which is shown in comparison with the prior art extension sequence (FIGS. 1A and 1B).

(7) In the method of the disclosure, the sequence for extending the main landing gear (MLG) and the main landing gear doors (MLGD), is similar to the traditional sequence shown in FIGS. 1A and 1B. However, the extension of the nose landing gear (NLG) is delayed in time with respect to the extension of the MLG.

(8) As shown in the example in FIG. 2B, a few seconds after the pilot activates the extension sequence, the extension of the MLGD is initiated and the fully extended position of the same is reached approximately in two seconds. Once the MLGD reach their final extended position, the extension of the MLG is started and approximately in six seconds, the MLG reaches its final or fully extended position. Once the MLG is fully extended, the main landing gear bays have to be closed again, and for that the MLGD are retracted.

(9) According to the disclosure, the extension of the NLG is delayed in time with respect to the extension of the MLG, in the case of FIG. 2B, this delay is represented as the time frame ((NLG) Timing Shift). This means that the extension of the NLG in FIG. 2B is started after the beginning of the extension of the NLG of FIG. 1B, for example the extension of the NLG is started after the MLG reach their fully extended position (80 in FIG. 2B), and before or after starting the retraction of the MLGDs.

(10) This time delay ((NLG) Time Shift) with respect to the extension of the MLG is represented in FIGS. 1B and 2B in combination, and it can be adjusted, that is, it can be made shorter or longer for each particular application (aircraft type), in order to be compatible with the acceptable load levels for new aircraft designs or for retrofit solutions, taking into account the landing gear timing and the aircraft performance requirements.

(11) In a preferred embodiment, the extension of the NLG is coordinated with the extension of the MLGD, such as the extension position of the NLG is less than 50% of its fully extended position, when the MLGDs start their closing movement.

(12) In another preferred embodiment, the extension of the NLG is coordinated with the extension of the MLGD, such that the extension position of the nose landing gear is less than 10% of its fully extended position, when the MLGDs starts their closing movement.

(13) In another preferred embodiments, depending on the size or type of the aircraft, the extension of the NLG is started when the MLG has reached at least less than 50% of its fully extended position.

(14) The retraction time sequence is shown in FIGS. 4A and 4B, and follows an inverse sequence as the one described above for the extension time sequence. Nose and main landing gears (NLG,MLG) are in their extended position, and nose and main landing gear doors (NLGD,MLGD) are in their retracted position. Once retraction of the landing gear is ordered by the pilot few seconds after take-off, first the NLGD is opened and after that, the NLG is extended, while main landing gear and main landing gear doors remains in the same position.

(15) Once the NLG has reached a predetermined angular position in its retraction movement, or when the NLG has reached its fully retracted position, then extension of the MLGDs is started.

(16) Therefore, the operation of the NLG is coordinated with the operation of the MLGD, such that the NLG is kept retracted (housed within a nose landing gear bay) during a major part of the time that the MLGDs are fully extended, either for the extension and for the retraction operation, wherein the major part of the time means more than 50% of the time. For example 80% or 90% of the time. In this manner, vibrations on the main landing gear doors are reduced with yields on great reduction on maintenance costs.

(17) Preferably, the method of the disclosure is applied only during normal flight conditions (without emergency); however, during emergency procedures the traditional extension operation described with respect to FIG. 1B is applied.

(18) The method of the disclosure can be retrofitted in existing aircrafts or forward fitted in future aircraft, by modifying the control program of the landing gear actuation hydraulic system.

(19) An additional advantage of the disclosure is that the MLG can be lowered earlier in order to have the LG drags acting more time to slow down the aircraft since the vibrations on the MLGD are now reduced, which is beneficial in a normal landing approach.

(20) Other preferred embodiments of the present disclosure are described in the appended dependent claims and the multiple combinations of those claims.