Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Aeronautical vehicle
Reexamination Certificate
1999-02-16
2001-03-06
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Aeronautical vehicle
C701S210000, C244S017130, C244S183000
Reexamination Certificate
active
06198991
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a low-noise level landing apparatus and system for helicopters, which is intended to reduce noise generated during landing approach.
Noise generated from a helicopter during landing approach is mostly caused by the rotation of a main rotor. In particular, BVI (blade vortex interaction) noise is an impulsive noise which is caused by a sudden change of the blade air load during the interaction between the blade and previously shed blade tip vortex. The BVI noise, if generated, is louder than any other noise sources.
FIG. 8
is a graph showing an example of a BVI noise generating area with respect to the airspeed and descending speed of a helicopter. In this example, it is understood that the BVI noise is generated when the airspeed is in the range of 40 to 120 kt (knots) and the descending speed is in the range of 300 to 1,200 ft (feet)/minute, and that the BVI noise is loudest when the descending angle is in the range of 4° to 6°.
For this reason, in order to minimize the BVI noise, it is desired that a helicopter should take a curved flight route by continuously changing the descending angle from the start of landing in order to avoid the BVI noise generating area.
However, it is very difficult for the pilot to bear the noise generating conditions shown in
FIG. 8
in mind, to select a low-noise level flight route with the aid of instruments while manually controlling the helicopter. In particular, safety is the top priority during landing, and noise reduction is apt to be of secondary importance.
As an example of prior art, Japanese Patent No. 2,736,045 (Japanese Patent Application No. Hei 8-63558) has been disclosed, wherein a flight route is selected on the basis of a BVI noise generating area database obtained by previous analyses, flight tests and the like. However, the BVI noise generating area is subjected to the effects of meteorological conditions, in particular, the effect of wind, whereby low-noise level landing approach may not be accomplished in some cases.
FIG. 9
is a graph showing how the BVI noise generating area is changed. A flight route P
1
is selected on the basis of the BVI noise generating area database. When meteorological conditions are no wind and the same as those under which the BVI noise generating area database is obtained, this route becomes a low-noise level landing route.
However, if the shape and position of the BVI noise generating area are changed by the effect of wind, the flight route P
1
enters the BVI noise generating area, and is no longer a low-noise level route. As a matter of fact, a flight route P
2
have been modified in accordance with the change of the area becomes a low-noise level landing route.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a low-noise level landing apparatus and system for helicopters, capable of more properly selecting a flight route in which noise during landing approach can be reduced, in response to changes in meteorological conditions without imposing any additional burden on the pilot.
The present invention provides a low-noise level landing apparatus for helicopters, provided on a helicopter, comprising:
data receiving means for receiving noise data measured on a ground by data communication;
helicopter position calculating means for calculating a position of the helicopter;
landing route setting means for setting a landing route;
air data measuring means for measuring an airspeed and a descending speed;
rotor rotational speed measuring means for measuring a rotor rotational speed;
helicopter weight measuring means for measuring a weight of the helicopter;
noise generating area database means for storing noise levels with respect to parameters of descending speed, airspeed, descending angle, rotor rotational speed and helicopter weight; and
flight route calculating means for determining a low-noise level flight route by setting a plurality of flight routes on the basis of the helicopter position and landing point and by referring to the noise generating area database with regard to those data from each measuring means,
wherein the flight route calculating means modifies a preselected flight route on the basis of the noise data from the data receiving means and reselects an optimal flight route.
According to the invention, since noise levels with respect to parameters of descending speed, airspeed, descending angle, rotor rotational speed and helicopter weight have been stored, any change in noise level at a landing point in accordance with changes in flight conditions can be followed accurately. In addition, since the measuring means is provided for each parameter, the noise level at the landing point during flight can be grasped properly. The descending angle can be calculated from the descending speed and the airspeed. The descending speed can also be calculated as a change ratio of the position of the helicopter with time.
Furthermore, the low-noise level flight route can be selected by setting a plurality of flight routes on the basis of the helicopter position and landing point and by referring to the noise generating area database. Moreover, even if the current flight conditions are different from the conditions at the creation time of the database, the selection can be accomplished flexibly by judging the noise measured on the ground whether the selected flight route is optimal or not, and by modifying the flight route automatically or manually so that the flight route becomes the optimal flight route. Flight conditions to be considered are, for example, meteorological conditions such as wind direction, wind speed and amount of rainfall, as well as helicopter conditions for each model of helicopter such as engine characteristics, rotor characteristics and aerodynamic characteristics. Furthermore, the flight conditions can also include differences in local noise regulation around the heliport.
It is also possible to determine maneuvering conditions such as airspeed, descending angle and rotor rotational speed, in response to the optimal flight route. The maneuvering conditions thus determined may be indicated on instruments to assist pilot manual control, or may be used for automatic flight control by a computer or the like. In this way, noise reduction can be attained properly while reducing a burden on the pilot.
Furthermore, in the invention it is preferable that the helicopter position measuring means is composed of a differential GPS, and the data receiving means receives the noise data and differential GPS correction data.
According to the invention, by using the DGPS (Differential Global Positioning System) as the helicopter position measuring means, it is possible to obtain a measurement accuracy ten times higher than that of an ordinary GPS. The DGPS corrects natural errors by using a stationary GPS receiver, and eliminates the errors by transmitting data for correcting the errors to a mobile GPS receiver. Since the position of the helicopter is required to be obtained with high accuracy to assist pilot manual control and to accomplish automatic flight control, the application of DGPS seems to be promising for helicopters. When using the DGPS, a data communication apparatus for obtaining the correction data transmitted from the ground is required to be installed on the helicopter. In the case of the present invention, however, the noise data measured on the ground can be transmitted to the helicopter by using this kind of data communication without providing any special apparatus.
Furthermore, in the invention it is preferable that the low-noise level landing apparatus comprises noise level indicating means for indicating noise levels obtained by discriminating noise data on the basis of a plurality of threshold values, wherein the threshold values are variable in accordance with an altitude of the helicopter or a distance to the landing point.
According to the invention, when the pilot maneuvers the helicopter to carry out landing, the noise data measured on the ground is in
Kondo Natsuki
Nishimura Hiroki
Yamakawa Eiichi
Advanced Technology Institute of Commuter-Helicopter, Ltd.
Cuchlinski Jr. William A.
Donnelly Arthur D.
Wenderoth , Lind & Ponack, L.L.P.
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