Wire-free arming system for an aircraft-delivered bomb

A system for wire-free arming of a bomb releasably carried by an aircraft mb rack includes an emitter circuit mounted on the bomb rack, and an electrical power generator circuit, a detector circuit, and an arming circuit mounted on the bomb. The emitter circuit on the bomb rack is activated when the aircraft pilot releases the bomb. The emitter circuit emits a predetermined transmission of electromagnetic energy, such as an infrared pulse train or a pulsed magnetic field, in the direction of the bomb through the airspace between the aircraft bomb rack and bomb. The electrical power generator circuit on the bomb is activated by release of the bomb for generating electrical power as the released bomb separates from the aircraft bomb rack and producing an output power signal after release of the bomb from the bomb rack. The detector circuit on the bomb is responsive to the output power signal from the generator circuit and to detection of the emitted transmission from the emitter circuit for producing an arming signal. The arming circuit is responsive to the output power signal from the generator circuit and to the arming signal from the detector circuit for producing arming of the bomb.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention generally relates to aircraft-delivered ordnance and, 
more particularly, is concerned with a system for wire-free arming of an 
aircraft-delivered bomb. 
2. Description of the Prior Art 
The arming of aircraft-delivered ordnance, or bombs, has remained 
essentially unchanged since its inception in World War II. Basically, 
arming occurs when an arming wire attached between the aircraft bomb rack 
and the bomb, pulls a pin from a fuze which will then allow the fuze to 
arm. The arming wire may also at the same time or separately actuate a 
mechanism that fires a thermal battery or a mechanism that allows ordnance 
fins to be deployed. Multiple arming wires may be used to perform the 
various arming tasks necessary for some present day weapons. Thus, the 
arming process may be quite complicated. 
Typically, the arming wire is attached to the aircraft at the bomb rack. 
There are several termination points that can be used depending on the 
actuation force and purpose. One point that can be used is an attachment 
lug (referred to as a positive arming lug) that will result in the arming 
wire, or lanyard, always being pulled when the bomb drops away from the 
rack. Another attachment point is the arming solenoid which allows the 
pilot to select whether or not the arming wire will be pulled when the 
bomb drops. 
On a typical bomb rack there are three attachment points that can be used 
for positive arming of the arming wire whereby the wire will always get 
pulled. Additionally, there are two arming solenoids, located fore and 
aft, which can be independently selected to release or hold the arming 
wire. More than one arming wire can be attached to the positive arming 
lugs but only one wire is terminated by the arming solenoid. 
The above-described present method of arming aircraft-delivered ordnance by 
use of an arming wire connecting the bomb to the aircraft bomb rack has 
several deficiencies in terms of both reliability and safety. One 
deficiency is that the arming wire may not be installed correctly so that 
when the weapon is released, the arming wire does not pull the pin from 
the fuze. As ordnance becomes more complicated to arm, this deficiency 
becomes more critical. In several current weapons, for instance, there are 
three separate arming wires that arm the rocket motor, thermal battery, 
and tail fuze. 
Another deficiency is that material defects in the arming wire or in the 
ordnance interface to the arming wire may cause the wire to fail before 
arming occurs. Still another deficiency is that bird strikes or other 
foreign object collisions may cause arming unintentionally or may break 
the arming wire, preventing arming from occurring. 
A further deficiency is that ordnance may become armed unintentionally. One 
instance where this can happen is when the bomb release lugs do not 
completely release the bomb on ejection. Typically when a bomb "hangs up", 
one lug releases properly but the other lug does not. When this happens, 
the movement of the bomb itself causes the arming wire to be pulled and 
thus arm itself. Another instance where unintentional arming of the bomb 
by the arming wire can occur is when the bomb is accidentally dropped at 
zero airspeed, such as on an aircraft carrier deck. Still another instance 
is a midair collision between aircraft which results in pulling of the 
arming wire and unintentional arming of the bomb. A further instance is an 
ordnance jettison situation where the pilot desires to drop the bomb 
without arming it. The arming solenoid does not always release the arming 
wire. Thus, bombs that are intended to be dropped unarmed are actually 
armed. As should be readily apparent, these occurrences of unintentional 
arming are of significant concern to pilots. 
Arming wires also are relatively inflexible in communicating arming 
information to the fuze. Conventional methods of communicating information 
to the fuze use the two arming wire solenoids on the bomb rack. One 
solenoid is used to arm or not arm the fuze. The other solenoid is used to 
open or not open retard fins when used or for tail fuze arming or other 
uses depending on the bomb involved. In any case, however, there are only 
two conditions that can be communicated: the arm/no arm condition and a 
second optional condition. 
In view of the many above-described deficiencies arising from currently 
used arming wires, there is a long-felt need for an alternative approach 
to arming of aircraft-delivered bombs which will eliminate or avoid these 
deficiencies. 
SUMMARY OF THE INVENTION 
The present invention avoids the aforementioned deficiencies and thereby 
satisfies the long-felt need by providing a system for arming of an 
aircraft-delivered bomb which is wire-free and eliminates the need for any 
connection between the aircraft and the bomb. In contrast to prior art use 
of arming wire, the wire-free arming system of the present invention 
includes an emitter circuit on the aircraft for producing a predetermined 
transmission of electromagnetic energy, such as a specially coded pulse 
train, in the direction of the bomb across airspace between the aircraft 
and bomb, and detector and arming circuits on the bomb for detecting the 
transmission and for producing the arming of the bomb. 
The present invention provides many advantages and features not available 
nor obtainable by using the prior arming wiring method. First, arming of 
the bomb can be accomplished when the bomb is away from the aircraft, thus 
minimizing the danger to the pilot. This would also allow use by aircraft 
with internally carried weapons. Second, a more flexible arming operation 
is provided because different arming pulse trains can be transmitted to 
each bomb for communicating different modes of operation to the bomb fuze. 
Third, bomb loading procedures are much simplified because arming wires do 
not need to be connected. Thus, there is no chance that arming wires would 
be connected incorrectly or that material defects in the arming wires 
would be responsible for misarming a bomb. Fourth, there is no possibility 
that foreign objects would accidentally arm the bomb in flight as well as 
accidental arming due to bomb hangup on the bomb rack or accidental arming 
onboard an aircraft carrier if the bomb is dropped at zero airspeed. 
Accordingly, the present invention is directed to a system for wire-free 
arming of a bomb releasably carried by an aircraft. The arming system 
basically includes an emitter circuit mounted on the aircraft, and a 
detector circuit and arming circuit mounted on the bomb. The emitter 
circuit on the aircraft is activated, when the aircraft pilot releases the 
bomb, for emitting a predetermined transmission of electromagnetic energy, 
such as an infrared pulse train or a pulsed or static magnetic field, in 
the direction of the bomb through airspace between the aircraft and bomb. 
The detector circuit on the bomb is responsive to detection of the emitted 
transmission from the emitter circuit for producing an arming signal. The 
arming circuit is responsive to the arming signal from the detector 
circuit for producing arming of the bomb. 
The arming system also preferably includes an electrical power generator 
circuit mounted on the bomb. The power generator circuit on the bomb is 
activated by release of the bomb for generating electrical power, as the 
released bomb separates from the aircraft, and producing an output power 
signal. The detector circuit on the bomb produces the arming signal in 
response to the output power signal from the generator circuit in addition 
to detection of the emitted transmission from the emitter circuit. The 
arming circuit produces arming of the bomb in response to the output power 
signal from the generator circuit in addition to the arming signal from 
the detector circuit. 
These and other features and advantages of the present invention will 
become apparent to those skilled in the art upon a reading of the 
following detailed description when taken in conjunction with the drawings 
wherein there is shown and described an illustrative embodiment of the 
invention.

DETAILED DESCRIPTION OF THE INVENTION 
Referring now to the drawings, and particularly to FIGS. 1-3, there is 
schematically shown a bomb rack 10 of an aircraft and a bomb 12 releasably 
carried by the bomb rack 10 which jointly incorporate a wire-free arming 
system in accordance with the present invention, being identified overall 
by the numeral 14. The bomb 12 is releasably carried from the bomb rack 10 
by fore and aft spaced bomb lugs 16 and sway braces 17 on the rack 10. 
Also, the bomb rack 10 has fore and aft arming solenoids 18 thereon. 
Wire-Free Arming System - In General 
In its basic components, the wire-free arming system 14 includes an emitter 
circuit 20 mounted on the bomb rack 10 and, specifically, coupled in 
parallel to the aft one of the arming solenoids 18, and a detector circuit 
22 and an arming circuit 24 mounted on the bomb 12. In addition, 
preferably, the arming system 14 includes an electrical power generator 
circuit 26 mounted on the bomb 12 for powering the detector circuit 22 and 
the arming circuit 24. 
The emitter circuit 20 of the portion of the arming system 14 on the bomb 
rack 10 is activated when the aircraft pilot releases the bomb 12 by 
moving a master arming switch in the cockpit to the arm position. Upon 
being activated, the emitter circuit 20 emits a predetermined transmission 
of electromagnetic energy in the direction of the bomb 12 through airspace 
between the bomb rack 10 and bomb 12. 
The electrical power generator circuit 26 of the portion of the arming 
system 14 on the bomb is activated by release of the bomb 12 for 
generating electrical power as the released bomb 12 separates from the 
aircraft bomb rack 10. The generation of electrical power by the power 
generator circuit 26, after release of the bomb 12, produces an output 
power signal for powering the detector circuit 22 and arming circuit 24. 
Preferably, the power generator circuit 26 employs a ram air generator 28 
which fits into a fuze well 30 in the bomb 12 that is open at the upper 
side of the bomb 12 and spaced midway between the bomb lugs 16. The 
generator 28 produces power by extending into and extracting energy from 
the air stream flow about the bomb 12 as it drops away from the bomb rack 
10. The generator 28 does not produce electrical power while the bomb is 
on the aircraft bomb rack 10 since the generator 28 is prevented from 
extending into the air stream due to mechanical interference at 32 with 
the bomb rack 10. Thus, preferably, the bomb 12 does not contain any 
stored energy that can power the arming circuit 24 prior to release of the 
bomb. 
The detector circuit 22 of the portion of the arming system 14 on the bomb 
12 is responsive to the output power signal from the power generator 
circuit 26 and to detection of the emitted transmission from the emitter 
circuit 20 for producing an arming signal. Even though emission of the 
predetermined transmission of electromagnetic energy by the emitter 
circuit 20 might occur before release of the bomb 12 from the bomb rack 
10, actual acquisition of the predetermined transmission is always delayed 
for a certain minimum period of time, for example 350 ms (milliseconds), 
after the bomb 12 has been ejected from the rack 10. This delay occurs 
because the generator 28 does not produce power while the bomb 12 is on 
the rack 10, as explained above. As will also become clear below, after 
the detector circuit 22 acquires the transmission and produces the arming 
signal, there is further delay of time before the arming circuit 24 
actually arms the bomb 12. This further time delay is attributable to the 
time required for charging particular components of the arming circuit 24 
which, in turn, are fired to arm the bomb 12. The acquisition and charging 
time delays allow the separation between the aircraft bomb rack 10 and the 
bomb 12 to increase, thus, increasing the safety aspects of the arming 
system 14. 
The arming circuit 24 of the portion of the arming system 14 on the bomb 12 
is responsive to the output power signal from the power generator circuit 
26 and to the arming signal from the detector circuit 22 for producing 
arming of the bomb 12. The arming circuit 24 will only arm the bomb 12 
when a specific transmission, such as an infrared light emitting diode 
(LED) pulse train, is emitted by the emitter circuit 20. However, by 
having the detector and arming circuits 22, 24 on the bomb 12 recognize 
different pulse train patterns, various operating conditions and commands 
can be communicated to the bomb 12 for carrying out different functions, 
such as retard/nonretard, fuze arm/safe, contact/timed burst, etc. Also, 
specific bombs can be armed while other bombs remain unarmed. 
Emitter Circuit of the Arming System 
The emitter circuit 20 of the wire-free arming system 14 which is attached 
to the bomb rack 10 is illustrated in a block diagram in FIG. 2 and in a 
detailed electrical schematic diagram in FIG. 4. The emitter circuit 20 
preferably emits a 1.4 ms IR pulse every 45.9 ms when 28 volts DC (VDC) is 
applied to its inputs. The emitter circuit 20 is connected in parallel 
with the aft arming solenoid 18. When the solenoid 18 is energized with 28 
VDC (armed mode), the infrared LED emitter circuit 20 emits this IR pulse 
train to the bomb 12 indicating that the bomb is to be armed. 
Referring to FIG. 2, the emitter circuit 20 which employs infrared 
electromagnetic energy includes a power conditioner section 34, a pulse 
generation and shaping section 36, and a power amplifier-LED section 38. 
As seen in FIG. 4, the power conditioner section 34 includes a diode 
bridge rectifier 40 and a 9 VDC voltage regulator (uA78MG) 42. The section 
34 protects the emitter circuit 20 from reverse transients present when 
the aft arming solenoid 18 is turned off, and allows the emitter circuit 
20 to be installed (connected) to the solenoid 18 without regard to 
electrical polarity. The section 34 also converts the 28 VDC to 9 VDC. 
The pulse generation and shaping section 36 of the emitter circuit 20 
includes a remote control integrated circuit (SN76881) 44 that can output 
up to thirty-two different pulse patterns, each amplitude modulated, on a 
91 KHz carrier. One of the pulse patterns outputted by the section 36 is 
the 1.4 ms pulse every 45.9 ms which is the predetermined IR pulse 
transmission. Amplitude modulation is used in order to increase the range 
and detection reliability of the signal. 
The power amplifier-LED section 38 of the emitter circuit 20 includes a 
transistor amplifier (2N2907) 46 that discharges a capacitor 48 through 
two infrared emitting LEDs 50. The capacitor 48 charges in time for the 
next pulse. Each current pulse through the LEDs 50 is approximately 1.0 
amp. The spectral distribution of the light emitted by the LEDs 50 is from 
875 nm (nanometers) to 1021 nm. The spectral peak of the LEDs 50 is at 960 
nm. This emitter circuit 20 can transmit arming information over distances 
greater than forty feet. Optimal operational utility can be enhanced 
through the proper selection of wavelength. 
Detector Circuit of the Arming System 
The detector circuit 22 of the wire-free arming system 14 which is attached 
to the bomb 12 is depicted in a block diagram in FIG. 3 and in a detailed 
electrical schematic diagram in FIG. 5. The detector circuit 22 is 
positioned on the bomb 12 to receive and detect IR pulses in the 
predetermined transmission from the infrared LED emitter circuit 20 on the 
bomb rack 10. As seen in FIG. 5, the detector circuit 22 includes a 
photodiode (PH302) 52 sensitive to 940 nm wavelength infrared light, a 
preamplifier section (NEC PC1373H) 54, and signal conditioning section 56. 
Both the photodiode 52 and preamplifier section 54 of the detector circuit 
22 are mounted together in a shielded box, as represented by the dashed 
rectangle 58 in FIG. 5, positioned on the surface of the bomb 12. 
Shielding is necessary because the preamplifier section 54 is very 
sensitive to noise from the photodiode 52. The photodiode 52 is sensitive 
to light from 700 nm to 1100 nm. It has an integral infrared filter on its 
surface so that only light within this range is detected. Its radiant 
sensitive area is 9 square mm. The preamplifier section 54 employs a 
single integrated circuit optimized for infrared remote control 
applications. It consists of a photodiode input amplifier with bias level 
feedback in order to keep the output of the amplifier from being saturated 
in bright light, a pulse limiter and level shifter, a peak detector to 
detect the incoming 91 KHz amplitude modulated signal, and a waveform 
shaper to reduce noise on the detected signal. The preamplifier 54 
operates on power supplies from 6 to 14 volts. 
The signal conditioning section 56 of the detector circuit 22 passes the 
detected waveform through a Schmitt trigger gate (74C14) 60 with 
hysteresis in order to further reduce noise on the signal. There is also a 
pull-up resistor 62 placed on the input to the Schmitt trigger gate 60 so 
that when the IR detector circuit 22 is disconnected, its arming signal 
output to the arming section 24 is deasserted (held low). Referring to 
FIG. 6 as well as FIG. 5, an ARM command (the predetermined pulse train 
transmission) transmitted by the infrared LED emitter circuit 20 results 
in a positive-going 1.4 ms pulse with a period of 45.9 ms at the output of 
the Schmitt trigger gate 60 which is the output of the detector circuit 
22. On the other hand, a SAFE command transmitted by the emitter circuit 
20 results in a static low level at the output of the Schmitt trigger gate 
60 and, thus, of the detector circuit 22. If the IR pulse detector circuit 
22 is accidentally disconnected from the arming system 14, no arming 
commands will reach the arming circuit 24 and it will thus automatically 
safe the bomb 12. 
Arming Circuit of the Arming System 
The arming circuit 24 of the wire-free arming system 14 which is contained 
within the the bomb 12 is shown in a block diagram in FIG. 3 and in a 
detailed electrical schematic diagram in FIGS. 7 and 8. The arming circuit 
24 is composed of four sections, the microcontroller section 64 and status 
section 66 of FIGS. 3 and 7 and the charge pump section 68 and squib 
firing section 70 of FIGS. 3 and 8. 
The arming process is controlled by the microcontroller section 64 that 
receives data input from the ram air generator 28 of the power generator 
circuit 26 (air speed determination) and arming information (arming 
signal) from the IR pulse detector circuit 22. The microcontroller section 
64 derives its power from the generator 28 of the power generator circuit 
26 as will be described later. The generator 28 also provides power to 
charge the squib capacitors 72 of the charge pump section 68. 
When the microcontroller section 64 receives a valid arming signal from the 
detector circuit 22, after bomb separation, it activates the charge pump 
section 68 to charge the squib capacitors 72 and then discharges them 
through the squib firing section 70 into a squib 74. A mode switch 76 
(having modes: test=off, high, open, and normal=on, low, closed) allows 
circuitry to be tested for proper operation and the output of a test LED 
status bar graph 78 of the status section 66 shows arming progress and 
results as the microcontroller section 64 completes each arming task. 
Referring to FIG. 7, the microcontroller section 64 uses a 8-bit single 
chip microcontroller 80 (Hitachi HD63701XOP CMOS UV-EPROM). The 
microcontroller 80 includes a read only memory (ROM), random access memory 
(RAM), and input and output lines. It has programmable timers with timing 
and pulse relationship circuitry. The microcontroller 80 operates at 4.0 
MHz supplied by a crystal 82 and starts executing instructions 
approximately 30 ms after power is applied to it. The microcontroller 80 
requires that the reset line be held low for at least 20 ms after power is 
applied to the controller. The internal timer clock rate is equal to the 
system clock frequency (4.0 MHz) divided by four. Thus, the timer period 
is 1 microsecond. 
The mode switch 76 connected to one input line is read by the 
microcontroller 80 to determine whether the mode of the arming circuit 24 
is test mode or normal operation mode. In test mode, the microcontroller 
80 turns on sequentially each LED 84 of the LED status bar graph 78 of the 
status section 66, activates the charge pump section 68, and then 
discharges the squib capacitors 72 through a squib 74 in the squib firing 
section 70. This mode verifies that the arming system 14 is in operating 
condition. 
The LED status bar graph 78 of the status section 66 consists of seven LEDs 
84 connected to an output port of the microcontroller 80. The LEDs 84 are 
used for debug/test purposes. The meaning of each LED 84A-G when turned on 
(lighted) is as follows. The Arming Signal Active LED 84A is turned on 
when an arming signal is being received; whereas when the arming signal is 
not being received, the LED 84A is turned off. The Ram Air Generator Power 
Up LED 84B is turned on when the output RAG UP (H) of the power generator 
circuit 26 exceeds a preset voltage. The Arming Signal Acquired LED 84C is 
turned on when the microcontroller 80 has determined that it has received 
a valid arming signal IR ARM (H) from the aircraft. The Charge Pump 
Started LED 84D is turned on when the microcontroller 80 has activated the 
charge pump section 68 of the arming circuit 24. The Squib Fired LED 84E 
is turned on when the squib capacitors 72 are discharged into the squib 
74. This LED is used to provide visual indication of firing the squib 74. 
The Bomb Disarmed LED 84F is turned on if the microcontroller 80 does not 
receive a valid arming signal within a preset time, in this case, 15 
seconds. After this LED is turned on, the microcontroller 80 duds the bomb 
12. The 5 Volt DC On LED 84G is on whenever 5 volts is present on the 
power bus. 
The microcontroller 80 is configured so that the output compare register of 
timer one (a 16 bit timer) is connected to the clock input of timer two 
(an 8 bit timer). This allows the period of very long pulses to be 
measured. 
The IR pulse detector circuit 22 inputs the signal IR ARM (H) to the 
microcontroller 80 which is the arming signal. The detector circuit 22 is 
connected to the timer-one clock input of the microcontroller 80 so that 
infrared pulse intervals can be measured. This connection is necessary 
because the arming signal is a pulse width variable signal. 
The power generator circuit 26 not only provides the 5 VDC power supply to 
the arming circuit 24, it also inputs the signal RAG UP (H) to the 
microcontroller 80 that is asserted (high) when the output of the ram air 
generator 28 employed by the power generator circuit 26 exceeds a preset 
voltage. The meaning of this signal will be explained later. 
The microcontroller section 64 of the arming circuit 24 drives two output 
signals from an output port: a charge pump activation drive signal C PUMP 
(H) and a squib fire command signal FIRE (H). The charge pump activation 
drive signal is pulsed to the charge pump section 68 by the 
microcontroller section 64 at approximately 1 KHz for three seconds to 
provide the pumping action necessary to pump the squib capacitors 72 up to 
18 volts. The second output signal, the squib fire command signal FIRE 
(H), is controlled by the software. It is asserted (high) in order to fire 
the squib 74 in the squib firing section 70. Specifically, the squib 
firing signal is used to discharge the squib capacitors 72 into the squib 
74 so that the arming process can be completed. 
Referring to FIGS. 3 and 8, there is seen the charge pump section 68 and 
squib firing section 70 of the arming circuit 24 respectively in block 
diagrams and detailed electrical circuit diagrams. The charge pump section 
68, the squib capacitors 72 and the squib firing section 70 are serially 
connected to one another in that order. The charge pump section 68 and 
squib firing section 70 are each connected to output ports of the 
microcontroller section 64 as mentioned above. 
After the microcontroller 80 has determined that the bomb 12 shall be 
armed, it initializes its hardware so that a 50% duty cycle 1 KHz square 
wave is outputted to the charge pump section 68 for 3.0 seconds. This 
signal C PUMP (H) provides the oscillation necessary for the charge pump 
section 68 to move charge across a diode/capacitor ladder 86 therein to 
higher voltage. The charge pump section 68 also includes a group of 
Schmitt trigger gates (74C14) 88 connected in parallel which amplify the 
signal C PUMP (H) and a transistor (2N2222) 90 which amplifies the signal 
again. Thus, with each oscillation cycle a packet of charge is moved 
across the diode/capacitor ladder 86 in much the same way that a water 
pump moves water from one pressure to a higher pressure. 
As charge exits the charge pump section 68, it gets deposited into the two 
330 microfarad squib capacitors 72. In about 3 seconds, the voltage on the 
squib capacitors 72 will reach about 18 volts. This is the voltage that 
will ensure that the squib 74 of the squib firing section 70 will be 
fired. A dud discharge resistor 92 is provided in order to discharge the 
squib capacitors 72 if the bomb duds. It has a 4 hour time constant. Thus, 
the squib capacitors 72 will be 99% discharged in 20 hours. 
The firing signal FIRE (H) received by the squib firing section 70 of the 
arming circuit 24 is asserted (activated) by the microcontroller 80 after 
the squib capacitors 72 have been charged by the charge pump section 68. 
The squib firing section 70 includes a group of Schmitt trigger gates 
(74C14) 94 connected in parallel which amplify the firing signal and a 
transistor (2N2222) 96 which amplifies the signal again. The transistor 96 
discharges the squib capacitors 72 through the squib 74 to electrical 
ground. 
Power Generator Circuit of the Arming System 
The power generator circuit 26 of the wire-free arming system 14 which is 
contained in the bomb 12 is depicted in a block diagram in FIG. 3 and in a 
detailed electrical schematic diagram in FIG. 9. The power generator 
circuit 26 provides +9 VDC and +5 VDC to respectively operate the detector 
circuit 22 and arming circuit 24. The circuit 26 also provides information 
on bomb velocity to the microcontroller 80. 
Referring to FIG. 9, the power generator circuit 26 includes the ram air 
generator (FZU-48B) 28, a power conditioning section 98, and a speed 
determination section 100. As described earlier, the ram air generator 28 
is a generator/turbine subassembly that hinges out of the fuze well 30 of 
the bomb 12 into the airstream. An interlock power switch 102 is provided 
to prevent power from being applied to the output leads until the 
generator/turbine is fully extended. Preferably, the ram air generator 28 
is spring loaded so that it will open when the bomb 12 is ejected from the 
bomb rack 10. An interlock pin (not shown) keeps the generator 28 from 
extending during storage and loading. The generator 28 is held closed by 
mechanical interference at 32 with the bomb rack 10 when the bomb 12 is 
loaded on the bomb rack 10 and the interlock pin is removed. The ram air 
generator 28 has a very short (5 minute total run time) lifetime. 
The output of the ram air generator 28 is a half wave rectified sinusoidal 
AC signal. Since the generator 28 has six poles, there will be three 
cycles of output per revolution. Thus, by measuring frequency of power 
output, the rotational speed can be determined. Then, by calibrating 
rotational speed of the turbine with air speed, the bomb s velocity can be 
determined. 
The power produced by the ram air generator 28 is conditioned by the power 
conditioning section 98 before being used by the detector circuit 22 and 
arming circuit 24. The power conditioning section 98 of the power 
generator circuit 26 includes a diode rectifier bridge (1N645.times.4) 104 
connected to the ram air generator 28 and 5 and 9 VDC voltage regulators 
106, 107 connected in parallel with the diode rectifier bridge 104 via the 
switch 102. The rectifier bridge 104 full wave rectifies power from the 
generator 28 and supplies it to the parallel voltage regulators 106, 107 
and the speed determination section 100. Thus, any positive or negative 
voltage transients that occur from the generator 28 will be converted to 
positive transients and filtered. The rectifier bridge 104 also allows the 
ram air generator 28 to be connected to the power supply section without 
regard to polarity. 
The speed determination section 100 of the power generator circuit 26 
includes a conversion portion 108 that converts a variable DC pulsing 
signal to digital pulses that represent bomb speed, and a threshold 
portion 110 that outputs an asserted level signal RAG UP (H) when the ram 
air generator output reaches a predetermined threshold. The conversion 
portion 108 is used by the microcontroller section 64 to determine the 
speed of the bomb 12 while the threshold portion 110 provides a simple 
level that specifies when a specified voltage (i.e., bomb velocity) is 
reached. 
The conversion portion 108 of the speed determination section 100 (the use 
of which is optional) includes capacitors to subtract the DC component of 
the ram air generator output, a comparator (LM324) 112, and a noise 
filter, rectifier, and clipper that prevents inputs to the comparator 112 
from going above 3 volts. The resultant pulsed waveform, with a frequency 
equal to the ram air generator speed, is compared by the comparator 112 to 
a level set by a potentiometer. The comparing is performed to minimize the 
effects of noise and the variable output of the ram air generator 28 on 
the output signal. The output SPEED (L) of the comparator 112 is fed to 
the microcontroller 80. 
The threshold portion 110 of the speed determination section 100 includes a 
comparator (LM324) 114 and a rectifying diode, capacitor, bleed resistor 
and clipper. The threshold portion 110 converts the pulsing DC voltage 
into a level that can be compared by the comparator 114. The rectifying 
diode allows the capacitor to be charged on the positive voltage cycle and 
not be discharged except through the bleed off resistor. The zener diode 
or clipper prevents the input to the comparator 114 from exceeding three 
volts. The threshold level is set by the potentiometer at one of the 
inputs of the comparator 114. Noise on the output of the comparator 114 is 
removed by using a Schmitt trigger gate. The signal RAG UP (H) then passes 
to the microcontroller section 64. 
Software of the Arming System 
FIG. 10 illustrates a flow chart of the program installed in the 
microcontroller section 64 of the arming circuit 24. The purpose of the 
program is to control the microcontroller 80 so that it correctly arms a 
bomb 12 only when conditions warrant the arming to occur. It should be 
mentioned here that the use of a microcontroller in actual practice of the 
invention is not necessary. A dedicated logic circuit with the program 
embedded therein could be used instead. 
The program depicted by the flow chart is designed for test purposes and 
would be similar but not identical to the program that would be used in 
production. The program contains codes for the LED status bar graph of the 
arming circuit status section 66 and for debugging and test. As designed, 
with the mode switch 76 in NORMAL mode, the program will arm the bomb 12 
if it receives a valid arming signal from the infrared emitter circuit 20 
on the bomb rack 10. 
The letters A to J in the blocks of the flow chart in FIG. 10 represent the 
following activities or decisions of the program: A-Initialized DDR, stack 
pointer, registers, disable interrupts; B - Is unit in test mode?; C - 
Start time-out timer ticking; D - Time-out expired?; E - Dud bomb, turn 
dud LED on; F - Ram air generator up yet?; G Turn status LED on; 
H-Infrared pulse width right?; I - Run charge pump for 3 seconds; and J - 
Fire Squib. 
When the bomb 12 is dropped, as explained earlier there is at first no 
energy stored on board to power the bomb arming circuit 24. As the bomb 12 
leaves the bomb rack 10, the ram air generator 28 opens and starts to 
produce power. The microcontroller 80 waits for the power generator 
circuit threshold portion 110 to indicate that the ram air generator 28 
has started to output voltage above the threshold set by the potentiometer 
therein. This threshold must be crossed within 15 seconds from power on or 
else the microcontroller 80 will dud the bomb 12. 
Once the ram air generator 28 starts producing power above the threshold, 
the microcontroller 80 looks for a valid arming signal being received by 
the detector circuit 22 from the emitter circuit 20. A valid arming signal 
is a 1.4 ms pulse occurring every 45.9 ms. If a valid arming signal is 
received within 3 seconds of the ram air generator 28 producing power 
(generator output crossing the threshold), the microcontroller 80 
activates the charge pump section 68 for 3 seconds and then discharges the 
squib capacitors 72 through the squib 74. If the microcontroller 80 does 
not receive a valid arming signal within 3 seconds of ram air generator 
power up, then the bomb 12 is dudded. 
If the mode switch 76 is placed in TEST mode, the microcontroller 80 
sequentially turns on each LED status bar graph LED 84A-G, activates the 
charge pump section 68 for 3 seconds, and then discharges the squib 
capacitors 72 into the squib 74. The first LED status bar graph LED 84A, 
ARMING SIGNAL ACTIVE, is used for arming signal debug. It is turned on by 
the microcontroller 80 whenever an arming signal is being received and off 
when the arming signal is not being received. This on/off process occurs 
in real time. Thus, it is useful in order to determine infrared emitter 
field of view, etc. 
Alternatives 
An advantageous feature of the present invention is that the arming circuit 
24 provides a standardized arming architecture such that arming devices 
other than infrared may be connected to the microcontroller 80 without 
changing the fundamental design of the arming circuit 24. For example, as 
shown in FIGS. 11 and 12, an emitter circuit 116 and detector circuit 118 
employing a Hall effect magnetic field is used in place of the infrared 
emitter and detecter circuits 20, 22. The same standardized arming 
architecture of the arming circuit 24 and the same power generator circuit 
26 is employed with the Hall effect emitter and detector circuits 116, 
118. 
More particularly, the Hall effect emitter circuit 116 which is attached to 
the bomb rack 10 includes a diode bridge rectifier 120 and an 
electromagnet 122. The electromagnet 122 is attached via a tether 124 to 
the bomb rack 10. The electromagnet 122 is connected in parallel with the 
rectifier 120 which, in turn, is connected in parallel with the aft arming 
solenoid 18, and produces a magnetic field whenever the arming solenoid is 
energized. The rectifier 120 guarantees that current will always flow 
through the electromagnet 122 in the same direction, thus always creating 
the magnetic field in the same direction. Since the Hall effect detector 
circuit 118 will only detect a magnetic field flowing from the south pole 
of a magnet, the bomb will only arm if the magnetic field is flowing in 
the proper direction. The electromagnet 122 has a coil resistance of 68 
ohms and operates on 28 VDC; thus, it has the same characteristics as 
arming solenoid 18 on the bomb rack 10. When energized, the electromagnet 
122 produces a magnetic field in excess of 300 gauss over the face of its 
poles. This field intensity is more than adequate to trigger the Hall 
effect detector circuit 118 rated at 90 gauss. 
The Hall effect detector circuit 118 is mounted externally on the bomb 12 
close to the aft bomb lug 16 and sway brace 17 but beneath the aft arming 
solenoid 18. It is mounted so that the magnetic flux created by the 
electromagnet 122 passes through the detector circuit 118. The 
electromagnet 122 is located so that its poles are within one inch of the 
Hall effect detector circuit 118. As stated above, the Hall effect 
detector circuit 118 requires a magnetic flux density of at least 90 gauss 
in order to output an asserted signal. 
The Hall effect detector circuit 118 thus senses the presence or absence of 
the magnetic field produced by the electromagnet 122 and appropriately 
arms or duds the bomb 12. The same arming circuit 24 on the bomb 12 is 
powered using the same ram air generator 28, as in the arming system using 
infrared electromagnetic energy. Also, the same type of program is used by 
both the infrared and Hall effect arming alternatives. 
When the bomb 12 is dropped, the electromagnet 122 travels down with the 
bomb for about six feet or for 500 ms and then is pulled away from the 
bomb 12. During this time, the generator 28 begins producing power and the 
microcontroller 80 starts executing its program. The program first checks 
to see if the bomb velocity is within limits (bomb velocity is determined 
by generator output frequency) and it then checks to see if the Hall 
effect detector circuit 118 is detecting the presence of a magnetic field. 
If the detector circuit 118 detects a magnetic field, then the 
microcontroller 80 charges the squib capacitors 72 for 3 seconds and then 
discharges them into the squib 74. This charging time allows the 
separation between the aircraft and the bomb to increase. When the squib 
74 is fired, the bomb 12 becomes armed. By pulsing the magnetic field and 
having the microcontroller recognize these pulses, various other 
conditions and commands can be transmitted to the bomb, the same as in the 
case of the IR pulse train. 
The use of the Hall effect circuits 116, 118 has several advantages. The 
Hall effect device is very small, simple, rugged, and low cost. It is 
currently used in automotive ignition systems where it is subjected to 
high and low temperatures, high EMI fields, and water and dirt 
environments. It will detect arming signals reliably under these 
constraints. Its low cost and flat form factor allow it to be flexibly 
configured to the bomb. Arming information can be transmitted to it 
easily. The Hall effect device is also virtually immune to 
countermeasures, detection of arming from ground observers, and accidental 
arming (if pulsed magnetic fields are used). It also allows the same 
advantages as the IR device described earlier because of the elimination 
of the arming wire. 
It is thought that the present invention and many of its attendant 
advantages will be understood from the foregoing description and it will 
be apparent that various changes may be made in the form, construction and 
arrangement of the parts thereof without departing from the spirit and 
scope of the invention or sacrificing all of its material advantages, the 
forms hereinbefore described being merely a preferred or exemplary 
embodiment thereof.