SPECIFICATION OF THE INVENTION

1. Title of the invention

System and Method for level-toss bombing for air-to-surface unguided weapon from fighter aircraft

2. Field of Invention

This invention relates to toss bombing of unguided air-to-surface weapon from fighter aircraft, in particular to a system and method to provide solution/guidance for level-toss.

3. Prior art and Draw backs of prior art

Toss bombing (sometimes known as loft bombing) is a method of bombing where the attacking aircraft pulls upwards when releasing its bomb load, giving the bomb additional time of flight by starting its ballistic path with an upward vector. Toss bombing technique is generally preferred by pilot whenever he does not want to overfly the target with the aircraft at an altitude to perform for dive-bombing or level bombing.
Most of the conventional unguided air-to-surface weapon aiming system computes the toss ballistic trajectory of weapon for dive-toss in Continuously Computed Release Point (CCRP) mode of attack. Hence the conventional method does not provide an effective method to compute the toss ballistic trajectory of weapon for level-toss in CCRP attack mode.

4. Aim of the Invention

The objective of this invention is to provide a system and method to perform level-toss attack, by inventing a method to obtain the toss horizontal ballistic range by catering the increase in the height and range of aircraft during toss attack.

Further objective is the method to display toss cue with/without availability of the toss solution prior to pull up of the aircraft and to achieve or maintain the required gravity on HUD.

5. Summary of the present invention

This invention presents a system and method for computation of the toss solution, i.e. toss horizontal range for release of air-to-surface ballistic weapon to carry out level-toss. The invention computes the corresponding toss horizontal range prior to pull-up of the aircraft. The invention determines the horizontal range and height increase of level-toss bombing using the curved path of aircraft during pull with the effect of gravity. The invention also provides the mechanism to display the cues, by depicting the acceleration to be achieved for maintaining the required gravity, to perform toss bombing on Head Up Display.

The system consists of Toss Bombing Module 160 which computes the toss horizontal range from its sub modules viz, Ballistic LUT Module 161, Toss Increment Range & Height Module 162, Toss Speed & Height Module 163, Limitation Module 164, Interpolator Module 165, Toss Horizontal Range Module 166. The Toss Bombing Module 160 receives the input parameters from Inertial Navigation Module 110, Range Sensor Management and Height above Target Module 120, Wind Module 130. The Toss Cue Generator module 167 generates the representation of the toss solution availability based on the toss horizontal range for displaying on HUD to perform level-toss.

The Display Generation module 170 displays the toss cue along with other weapon aiming cues (i.e. impact point of the weapon) by obtaining the impact point co-ordinates from Impact Point Module 150 and Ballistic Trajectory Module 140 on HUD to facilitate the pilot in carrying out efficient weapon aiming during level-toss.

6. Brief Description of the Drawings

Figure 1 is a block diagram of the weapon aiming system for level-toss bombing for providing guidance and its display on HUD.

Figure 2a depicts the curved path of aircraft during pull out and weapon trajectory after toss bombing.

Figure 2b is a view of the path of bomb in level-toss bombing where AB: Aircraft level flight, A: Point where aircraft start towards target, B: Point where aircraft will pullout, C: Point where aircraft will release the weapon.

Figure 3 is a flow chart of the steps illustrating the method of determining the Ballistic Toss Range.

Figure 4 is a view of toss cue with impact point display on HUD.

7. Detailed Description of the Invention
This invention presents a method for computation of range and height increment, the ballistic toss range for level-toss bombing of air-to-surface unguided weapon during the CCRP mode of attack. This method takes the path of aircraft as curved during pull out and also uses a Look up Table for computation of toss range. This invention also displays the toss cue depicting the availability of solution for performing toss bombing when the difference between range to target and the Toss horizontal range is <400'. This invention aids the pilot to carry out the level-toss release, consists of Inertial Navigation Module 110, Range Sensor Management and Height above Target Module 120, Wind Module 130, Ballistic Trajectory Module 140, Display Generation Module 170 and Toss Bombing Module 160 with sub modules viz, Ballistic LUT Module, Toss Increment Range & Height Module 162, Toss Speed & Height Module 163, Limitation Module 164, Interpolator Module 165, Toss Horizontal Range Module 166, Toss Cue Generator Module 167.

The Figure 3 shows the flow diagram illustrating the operation of Toss Bombing module 160 of the Weapon Aiming System 700. In step 302, the Toss Increment Range and Height module 762 receives the velocities in ground axes i.e. Vx, Vy and Vz from Inertial Navigation module 770 and the gravity, g with which pilot will pull the aircraft fed by pilot from UFCP. Similarly, Toss Speed and Height module 163 receives the wind velocities Wx, Wy from Wind module 730 and height above target, Rz from Range Sensor Management and Height above Target module 720.

In step 303, a Ballistic Look up Table of all the weapons which is intended to perform level-toss is created and stored in the volatile memory by Ballistic LUT module 767. Here the ballistic ranges along the ground axes for different unguided weapons are stored for flight path angle 30°, height above target from 3000' to 15000' in steps of 1000' and True air speed from 400 knots to 550 knots in steps of 50knots. The Look up Table can be varying for different aircrafts.

In step 304, the Decrement and HjnCrement are computed for level toss by module 762.
The Figure 2a and 2b shows the aircraft curved path and the bomb trajectory. At point
A, the aircraft flight is level and approaches towards the target, at point B the aircraft pulls up with the required g and at point C the weapon is released by the aircraft. The
Figure 2b also depicts the trigonometric computed range of the curved portion which is
2RSiny, where y = 30°, is the Flight Path Angle at which toss release is carried out. The
range and the height above target will increase because of level-toss mode of attack
and is given as follows:

Dincrement = 2 * R * SJn(y) * COS(y)

Hincrement = 2 * R * sin(y) * sin(y) r - — &
R = Radius of the curve path circle (Refer Figure 2b)

The Toss Speed and Height module 763 computes the Height above the Target, Rz' where the weapon is released step 305 as
Rz' = Rz + Hjncrement (b)
and also determines the True Air Speed, VTAS.

The Limitation module 764 limits the Rz' and VTAS to the lower and upper limits when the height (Rz') and speed (VTAS) limits are exceeded as per the Ballistic Look Up Table height and speed ranges. The operation is carried out in steps 307-314 and the pilot has to ensure that level-toss is carried out within these range of speed and height. The limit range can differ for different aircrafts.

The Interpolator module 765 performs the operations as in step 376 and 377. Here the corresponding weapon ballistic range, Sx_bomb stored in the Ballistic Look up Table as LUT_Sx is extracted for 30° flight path angle (y), true air speed (VTAS) and release height above target (Rz'). If the VTAS and Rz' is not matching with the stored speed and height indexes, then weapon ballistic range Sx_bomb is interpolated from stored LUT_Sx.

In step 378, the Toss Horizontal Range module 766, computes the toss horizontal range along the aircraft as

Sx_tOSS = Sx_b0mb + Dincrement (c)
which is the combined effect of increased distance due to level toss and the forward throw of the bomb in pull up condition.

The toss cue symbol is displayed on HUD to pilot with a dot in the centre of the circle when the weapon's toss horizontal range, Sx_toss is 400' behind the target providing the information, that the toss solution is available with the system 100 and level-toss attack can be carried out. This aids the pilot to initiate to pull up the aircraft to perform level-toss bombing. Refer Figure 4. In step 319, the computation of toss solution availability and position i.e. Azimuth (Az_toss) and Elevation (EI_toss) of toss cue symbol is computed in Toss Cue Generator module 167. The position of toss cue symbol is computed using the present aircraft acceleration wrt the pilot fed 'g' aiding the pilot to achieve or maintain the required acceleration.

The toss cue symbology is generated in the form of X and Y deflection by the Display Generation module 170 for display on HUD. The ballistic trajectory of the weapon for the prevailing release conditions is computed by Ballistic Trajectory module 140 and the impact point of the weapon, Az_ip and Elip is computed by the Impact Point module 150. Impact point symbol viz, Bomb Fall Line, Target circle, aiming marker is generated by the module 170 in addition to toss cue symbol for display on HUD to carry out effective level-toss bombing.

CLAIMS

We claim

1. A system and method for generation of real time horizontal toss range and guidance to perform level-toss by weapon aiming system. The system and method is characterised by Toss Bombing module comprising of Ballistic LUT module, Toss Increment Range & Height module, Toss Speed & Height module, Limitation module, Interpolator module, Toss Horizontal Range module, Toss Cue Generator module.

2. Toss Bombing module, as claimed in Claim 1, processes and generates the toss horizontal range

3. Ballistic LUT module, as claimed in Claim 2, stores ballistic range for different weapons in various release envelop of flight path angle, height above target and True Air Speed.

4. Toss Increment Range & Height module, as claimed in Claim 2, computes the height and horizontal range increments from the curved path of the aircraft.

5. Toss Speed & Height module, as claimed in Claim 2, computes the height above target from the height increment and Speed of the weapon at the point of release.

6. Limitation module, as claimed in Claim 2, limits the height and speed of the weapon according the Ballistic look up table height and speed ranges.

7. Interpolator module, as claimed in Claim 2, interpolates the ballistics range of the weapon from the Ballistic look up table according to the release conditions of height and speed.

8. Toss Horizontal Range module, as claimed in Claim 2, computes the toss horizontal range of the weapon along the aircraft.

9. Toss Cue Generator module, as claimed in Claim 2, generates a cue representation by a circle with dot based on the toss horizontal range for display on Head Up Display.