Hope I don’t get flamed for these questions, but here goes.
What is the difference between a regular MK82 and a MK82 Snakeye? I see one has a very simple tail while the Snakeye has a more complicated tail and fins.
Also, what is the difference between the short and exteneded fuse? Why would you use one over the other?
In fact, why would you use one over the other with both of these questions?
The snakeeye uses folding fins to slow the bomb down and give a more precise hit, also on low level missions it gives the plane a chance to escape the blast zone. The fuse extender is used for anti infantry type work and it may also work on the soft skinned APCs and such. All it does is explode the bomb several feet above the ground. The ultimate troop dispersal weapon. I don’t believe the fuze extender is being used anymore.
The high drag fins or the BSU-49 high drag tail assembly (which uses a “balute” air bag) are both used to allow for high speed delivery from tactical aircraft, yet provide the aircraft time to escape the blast from the detonating bomb. It actuall has nothing to do with accuracy.
The MK 82 (and most other dumb or GP bombs) can use nose fuses, tail fuses, or the FMU-113 air burst fuze. The FMU-113 is an altimeter like fuze that can be set for a given distance above the ground, and replaced the need for the extended nose fuzes.
Sorry I was trying to do that from memory. It seems like I read somewhere that the snakes could be delivered with more precision than the MK 84.
Okay, I understand that a nose fuse would denotate on impact while a tail fuse would allow the ordinance to penatrate said vehicle or structure before detonation, but how would the air burst fuze work? It would seem that if it was an altimeter type setting, the targets actual altitude above or below sea level would have to be known. This would limit the weapons usefulness to one target location. Or does the nose of the bomb contain a range finder of some type that measures distance from bomb to target?
Don [alien]
Thanks for the replies, gentlemen. i too would like to know the ansers to the futher questions asked by paraclete1 above.
The FMU-113 is a radar proximity fuse, and has it’s own little radar altimeter unit. BTW, it’s installed in the nose of the bomb.
Also, the “snakeye” kit was designated as the MK-15 tail assembly. It used four spring-loaded braking vanes to provide stability and braking for the bomb. This gave the delivering aircraft enough time to get out of the blast area. The problem is that these mechanical units were occasionally unreliable and would cause the bomb to stray considerably off target (inaccurate).
The solution was the BSU-49, also known as the AIR (Air Inflatable Retarder) tail kit. This system replaced the unreliable MK-15 and deployed a “balute” which is essentially an inflatable bag. It uses the slipstream from the bomb to inflate its air chamber. Once fully inflated, it acts as a braking parachute for the bomb. This system relies more on pure physics rather than a mechanical device, and proved to be more reliable. It is also much simpler to construct and maintain.
That’s the deal, and here’s a picture of an inert MK82 with the BSU-49 AIR kit installed and deployed.
IIRC,
The USN and USMC still use only the Snakeye variant while the USAF uses only the Ballute now.
Nose and tail fuze has nothing to do with delay. The delay is either electronic (in the case of the FMU 149 series fuse (fitted to the tail), or explosive in the case of say the M904E4 type fuze (fitted to the nose). Having the Fuze in the tail has nothing to do with the delay, and much more to do the the type of the fuze, and what you might like to attach to hte nose. FOr expamle LGB kits or ground proximity sensors.
In the mechanical fuze (M904) there is a delay element that is inserted into the fuze. it is an aluminium cartridge, about half the size of a C cell battery. There are a range of delays available, from .25 to instantaneous.
In the electronic fuze like the FMU 149, the delay is selected by rotating a little knob on the fuze. Depending on the capability of the Fuze function power supply in the aircraft, the pilot has the option of selecting different fuzing options in flight. this is acheived by supplying either +ve or -ve voltage to the fuze. Th fuze will then set itself to the preselected delays .
There are two different delays built into a fuze. There is the arming delay and the functioning delay.The diference between arming delay and funtioning delay is simple. The arming delay is the time taken from the bomb’s release from the aircraft to the time the fuze is armed. This means you are not flying around with an armed fuze in your bomb, which is not a safe situation. This delay is pretty critical for low level release, drop the bomb too low and the fuze will not have had time to arm itself. The bomb is armed in two ways - Mechanical fuzes have a brass arming wire that acts a bit like a pin in a grenade. It is attached to the aircraft pylon and runs through the fuze vane. When the arming solenoid is activated the wire will stay with the aircraft (hopefully,) as the bomb falls free the wire is pulled out of the arming vane and the vane is free to spin. If you need to jettison the bomb safe, you deselect the arming solenoid and the wire stays with the bomb. With electronic Fuzes this is all done with electrical volatage. As the bomb is released, the electrical cable between the bomb and the aircraft starts to pull tight. Just before it breaks, another shorter cable attached to a safety switch (Mk122 Safe arm defice or SAD) is pulled out, opening the circuit for the voltage to reach the fuze. This happens when the bomb is about 6 inches clear of the pylon, and deffinately on it’s way.
The functioning delay is the time between the bomb hitting the ground and the fuze functioning and causing the bomb to detonate. This controls the amount of penetration achieved.
The arming delay on mechanical fuzes is controlled by the number of turns required of the arming vane. On the electric fuzes it is again a setting on a little knob on the face of the fuze. for example, 2.4/inst means 2.4 seconds after leaving the aircraft the fuze is armed, and inst means as soon as it hits the ground it goes bang.
All this info related to how we used to operate with the A4K in RNZAF service, but is typical of other Fuze sydsems used in the MK 80 series and other weapons.
Thanks for that interesting explanation NZGunnie! I always had kind-of an idea how it worked, but now I know. Great stuff.[^]
Yes, thank you very much! I’m cutting and pasting this thread and keeping it for reference. If anyone has some additional info to add, please, by all means do so!
Thanks again.
Wait till you see what is being developed now! Makes those air burst fuzes seem “prehistoric.” There is now, or pretty soon, fuzes designed to go off after penetration, and set to read the number of levels it penetrates, and detonate at a certain floor. Pretty cool. The push right now is to reduce collateral damage as much as possible. Small diameter bombs will help with this, along with fuze development. We just built some MK82’s with FMU-113’s (airburst) yesterday. The pilots love the “fireworks” they make. BTW, the original air bursts were often refered to as daisy cutters, and used to rapidly create a LZ. Another tid bit of info…with in the “AMMO” community we spell it fuze, don’t know why, but we do.
Something else intersting regarding reducing colateral damage, the RAF used innert concrete Paveways in Iraq. A 1000lb lump of concrete travelling at 400kts is still going to ruin your day if you are a tank in a city street!