SPECIFICATION OF THE INVENTION

1. Title of the invention

A novel method for control of impact angle of air-to-surface laser guided weapon from fighter aircraft

2. Field of Invention

This invention relates to performing weapon aiming for air-to-surface weapon from fighter aircraft, in particular relates to a method for the control of impact angle of laser guided weapon.

3. Use of invention

The use of the invention is to enhance the effect of Laser Guided Bomb (LGB) released from fighter aircraft. This method can be used for different types of missions and to increase the mission success probability.

4. Prior art and Draw backs of prior art

To perform the weapon aiming, the impact angle on target will be defined based on the mission planned. The impact angle is selected by the pilot, taking into account the type of target (bunker, artillery position, bridge, etc), target's distance and the release height. The Conventional weapon aiming system computes and displays the ballistic range along with the minimum and maximum range of LGBs launch basket. In conventional systems, the dynamic control of the time of release of the weapon is not possible to achieve steep or shallow impact angles and the pilot has to maneuver the aircraft to achieve the required impact angle of the weapon on target.

5. Aim of the Invention

The main objective of this invention is to provide a method for computing weapon aiming solution for laser guided weapon, by inventing a mechanism for dynamic control of the impact angle by controlling the time of release of the weapon in different release conditions.
Further objective of the invention is to provide a method to feed the ballistic offset by the pilot from the cockpit control panel for controlling the impact angle. Yet further aspect of the invention is to provide the mechanism to display the LGB launch basket cues on Head Up Display (HUD) for the pilot selected impact angle.

6. Summary of the present invention

This invention presents a new method for control of the impact angle of the air-to-surface laser guided weapon. The method makes the LGB impact angle steeper or shallower based on the Ballistic offset fed by the pilot through the cockpit control panel. The real time Ballistic Range and impact point of the weapon are computed by Weapon Ballistic Trajectory Module 110. The Minimum and Maximum Ground Ranges of the laser guided weapon's launch basket is obtained from the prevailing release conditions from the LGB Ground Range Module 120. The Ballistic Offset Range Module 130 receives the Ballistic offset fed by the pilot and ballistic ground range of the weapon computed by Weapon Ballistic Trajectory Module 110 as input. Based on these inputs, the module 130, computes the Ballistic offset ground range to achieve ballistic, shallow or steep impact angle. The Ground ranges of the launch basket along with the Ballistic offset selected by pjJot (Le. Minimum, Maximum and Ballistic ground ranges) is represented as cue on HUD by Launch Cue Module 140 and Display Generation Module 150 to facilitate the pilot in carrying out the steep, shallow or ballistic impact of the LGB on target.

7. Brief Description of the Drawings

Figure 1 is a block diagram of the Weapon Aiming System with Impact angle Controller.

Figure 2 is a representation of ballistic offset for achieving the shallow, ballistic or steep impact angle on the target by LGB.

Figure 3a is a view of the Laser Guided Bomb's launch basket cue on HUD with minimum, maximum and ballistic release points to control the time of release of weapon.

Figure 3b is a view of the LGB Basket cue without offset, with positive offset and with negative offset for ballistic, shallow and steep type of impact on target respectively.

Figure 4 is a flow chart of the steps illustrating a new method for dynamically computing the Ballistic Offset Ground Range for controlling the impact angle.

8. Detailed Description of the Invention

In the present invention, the impact angle of the air-to-surface laser guided weapon is controlled by introducing the ballistic offset on ballistic range of weapon dynamically. This invention aids the pilot to achieve ballistic, steep or shallow type of impact angle on target by weapon by controlling the weapon release instance from the aircraft. This is achieved by Weapon Ballistic Trajectory Module 110, LGB Ground Range Module 120, Ballistic Offset Range Module 130, Launch Cue Module 140 and Display Generation Module 150. (Refer Figure 1) The module 110 determines the ballistic ground range of the weapon in ground axes and also computes the true air speed and flight path angle of the weapon. The minimum and maximum ground ranges of the LGB launch basket is computed by the module 120. The module 130 receives the ballistic offset fed by pilot and computes the Ballistic offset ground range. The module 140 receives Minimum ground range, Maximum ground range and Ballistic ground range with offset as input and it computes the LGB release guidance cue parameters, i.e. Minimum Release Point (MINRP), Maximum Release Point (MAXRP) and Ballistic Release Point (BRP). The module 150 receives these three guidance cue positions from module 140 and converts it as X and Y deflection voltages for displaying the guidance cues on HUD.

The Figure 4 shows the flow diagram illustrating the operation of the weapon aiming system 100 (Refer Figure 1) for control of the impact angle of the laser guided weapon dynamically. In step 402, the Weapon Ballistic Trajectory Module 110 receives the attack mode status. In step 403, the laser guided attack mode status is checked; if not set, the laser guided attack mode will not be engaged as in step 404 and if set, the laser guided attack is engaged and follows step 405. During this mode of attack, the Minimum and Maximum Ground ranges will be computed.
Jn step 405, the Ballistic forward distance of weapon is determined by the Weapon Ballistic Trajectory Module 110. The Module 770 receives the velocities, attitude angles (viz. roll, pitch and heading), aircraft height above ground and from mean sea level from on board sensors (Inertial Navigation and Global Positioning System (INGPS), Air Data Package (ADP), Radio Altimeter (RADALT) and Laser Designator Pod (LDP)). Using the sensor data and weapons physical characteristics (area, mass, etc), the module 770 computes the weapon ballistic trajectory and its parameters (Sx, Sy & Sz) and weapon impact point on ground. In step 406, the LGB Ground Range Module 720, Maximum Ground Range (MaxSx) and Minimum Ground Range (MinSx) of the LGBs launch basket is computed from True Air Speed (TAS), Flight path Angle (y) and height above target.

In step 407, the Ballistic Offset Range Module 730 accepts the ballistic offset range fed by the pilot from the cockpit control panel as per the mission (Refer Figure 2) to achieve the required impact angle as described below.

• When ballistic offset is fed as negative, the release of weapon is not carried out at the ballistic point but at a point closer to the target and within the LGB launch basket. This makes the LGB impact angle steeper.

• When ballistic offset is fed as positive, the release of weapon is not carried out at the ballistic point but at a point further away from the target and within the LGB launch basket. This makes the LGB impact angle shallower.

• When ballistic offset is fed as zero, the release of weapon is carried out at the ballistic point. This achieves a ballistic impact angle of LGB.

The impact angle controlling is performed in step 408 by Ballistic Offset Range Module 730. Ballistic Offset Ground Range, Sx_offset is the summation of weapon ballistic forward throw (Sx) and the Ballistic offset (Dx). In step 409, the Launch Cue Module 740 represents the Ballistic Offset ground range(Sxoffset), Maximum and Minimum ground ranges (MinSx & MaxSx) of the launch basket on range to target circle. The three range markers pfaced on the circle are the Minimum Release Point (MINRP) at 1 o'clock position, Ballistic Release Point (BRP) with/without offset and Maximum Release Point (MRP) marker. The markers MAXRP and BRP are positioned with respect to MINRP i.e. by considering Minimum Ground Range as reference. The calculation of MAXRP and BRP with/without offset is as follows (Refer Figure 3a, 3b) MAXRP = (((MaxSx)-(MinSx-1250))/15000)*360 in (deg) (a) BRP = (((Sx+Dx)-(MinSx-1250))/15000)*360 in (deg) (b) In step 410, the Display Generation Module 150 displays the LGB launch basket cue on the HUD (Refer Figure 3a, 3b) by converting the MINRP, MAXRP and BRP values as X and Y deflection voltages for displaying the guidance cues on HUD.

CLAIMS

We claim

1. A novel method for control of impact angle by the weapon aiming system of fighter aircraft for achieving ballistic, steep or shallow type of impact by laser guided air-to- surface weapon from fighter aircraft. The method is characterized by Ballistic Offset
Range module and Launch Cue module.

2. Ballistic Offset Range module, as claimed in Claim 1, processes the offset fed by the pilot from the cockpit control panel and computes the ballistic offset ground range.

3. Launch Cue module, as claimed in Claim 1, generates the representation of the laser guided weapon launch basket with Maximum & Minimum Ground Range and Ballistic Offset Ground Range for display on Head Up Display to provide the visual aid to the pilot to achieve ballistic, steep or shallow type of impact on target.