Dropping bombs on ground doesn't destroy your own aircraft?

[Guest deleted@50488]

So, yesterday I tried one of the packed missions, was on an Fw190 A5 mission to destroy a convoy, ready for departure with my mates all around, bomb fuses were ON, and inadvertedly I hit the "B" key, and the first, thgen the all bombs felt down on the ground just bellow my aircraft. There was somne smoke, but no explosions, and ceretainbly not any damage to my aircraft ???

Edited February 3, 2020 by jcomm-il2

[[APAF]VR_Spartan85]

What was the bomb timer set to?  
I think if it’s default/contact the bomb needs a certain fall time to activate.  So dropping it too low or on the ground will not spool the timer...

delayed bombs however I think will detonate if dropped in given situation.

[Guest deleted@50488]

Good point!  Will try it differently then and report back...

[RedKestrel]

5 hours ago, [APAF]spartan85 said:

What was the bomb timer set to?  
I think if it’s default/contact the bomb needs a certain fall time to activate.  So dropping it too low or on the ground will not spool the timer...

delayed bombs however I think will detonate if dropped in given situation.

I think too that some of the bombs with a shorter or even instant fuse time still need a certain amount of drop time before they will activate.

[busdriver]

9 hours ago, [APAF]spartan85 said:

What was the bomb timer set to?  
I think if it’s default/contact the bomb needs a certain fall time to activate.  So dropping it too low or on the ground will not spool the timer...

delayed bombs however I think will detonate if dropped in given situation.

 

You’re on the right track, except all bomb fuses require a minimum TOF (time of fall)   in order to arm. Think of it this way, if there is sufficient TOF to allow a fuse timer to count to 5 seconds, there certainty was time to count to 1 second or 0 (contact).

 

A bomb falling off while sitting on the ground is scary, it might explode with a defective fuse, but generally it should NOT explode. 1GCCFPs dropping German munitions stand a much greater chance of becoming “frag morts” (shot down by their own bomb) because this minimum TOF is not modeled correctly. [edit: I'm not criticizing the chances of becoming a frag mort, which is a very real threat. I actually love that threat. It's that dropping from extremely low altitude should IMO result in a dud.] By the same token allied 1GCCFPs will have short timer delay fuses realistically dud (not detonate) but longer timers unrealistically function when dropping from a low altitude. The point being if it won’t function with a contact setting due to insufficient TOF, then it should not function with a 5 second delay when dropped from the same height.

 

So to the OP, what you experienced is realistic. You blowing up would be unrealistic.

Edited February 3, 2020 by busdriver

[Zeev]

There is a bug when rearming your plane and if you have bombs there is a chance it will explode on spawn (tried with p51)

So no, your plane will no explode in any condition on the runway.

Edited February 3, 2020 by Zeev

[1PL-Husar-1Esk]

I don't know about ww2 bombs but ww1 bombs do not explode when dropped from plane on the ground - but they should.

[wombatBritishBulldogs]

14 minutes ago, 1PL-Husar-1Esk said:

I don't know about ww2 bombs but ww1 bombs do not explode when dropped from plane on the ground - but they should.

 Depends how far they fall ! would they have time take up a nose down position 

[Avimimus]

There is a bit of an issue where WWI bombs (and bombs dropped by the U-2VS) require at least 3-5 seconds delay to reliably detonate. I suspect this has to do with how fuses are modeled and the low altitude/speed (e.g. 150m/150kph) that the aircraft is flying at.

 

It is worth noting that such a problem doesn't exist for the PTAB bombs.

[1PL-Husar-1Esk]

From Sopwith Chronicles 

 

Ten bombers reach the target escorted by five two-seat “Strutters” who fight off four enemy aircraft one of which is shot down. One of the bombers also claims a victory.  In N5121 Fl Sub Lt Stevens thinks he has released his four 65lb bombs but one still hangs out of the rear left hand bomb door jamming it partially open.  After landing Stevens gets out and attempts to free the bomb.  Remarking to a mechanic that “it will need a crowbar to shift it”, he restarts the engine and taxis towards the hangar but the vibration is enough to loosen the bomb, which strikes the hard frosted soil and explodes with a blinding flash.   Stevens is seriously injured with bomb splinters in his left leg and burns to his face, two mechanics are killed and an officer and three other mechanics are seriously wounded some of them apparently by bullets.

[69th_chuter]

In the Pacific A-20 and B-25 strafers would usually install fuses on their bombs with the fuse shaft (with the little propeller doodad on it) considerably wound in to make sure they would arm before hitting the ground, so US bomb fuses could be adjusted as needed in the field for the mission.

[busdriver]

4 hours ago, chuter said:

In the Pacific A-20 and B-25 strafers would usually install fuses on their bombs with the fuse shaft (with the little propeller doodad on it) considerably wound in to make sure they would arm before hitting the ground, so US bomb fuses could be adjusted as needed in the field for the mission.

 

Just emphasize and hopefully not confuse. Those "little propeller doodads" also called arming vanes require a minimum TOF in order to meet the "fuse arm" requirements. What's the minimum TOF for a WWII fuse? I can not answer that. It could be an extremely short amount of time. However, with a really short TOF requirement the guy dropping at low altitude runs the very real risk of becoming a "frag mort." That is why you see pictures of SWP A-20s and B-25s making extremely low altitude deliveries dropping bombs with parachutes (para-frags). The idea is to give the bomber sufficient time to fly beyond the frag pattern of the bomb.

 

Think of the airplane as trying to outrun the explosion. How far away is sufficient? Back of the envelope numbers, a 500 pound General Purpose bomb has a nominal blast radius of 2000 feet (610 meters). A bomber flying 240 mph (385 km/h) will travel that distance in about 6 seconds. The blast fragments travel out to 2000 feet faster but not instantaneously, so if the fuse only needs 1 second TOF the delay timer would need to be a nominal 5 seconds. An instantaneous detonation could be problematic for the bomber crew.

 

The solution to not becoming a "frag mort" from a mate's bombs can be solved by one or a combination of three variables.

1) You can drop from an altitude so that you don't descend into the frag envelope.

2) You can drop with sufficient lateral offset from your mate's bombs.

3) You can drop with sufficient time delay on the bomb fuses (if in formation down low) or with sufficient time delay to allow the frag pattern to settle to earth.

[Feathered_IV]

5 hours ago, chuter said:

In the Pacific A-20 and B-25 strafers would usually install fuses on their bombs with the fuse shaft (with the little propeller doodad on it) considerably wound in to make sure they would arm before hitting the ground, so US bomb fuses could be adjusted as needed in the field for the mission.

 

Terrifying thought.  I’m always over tightening things.  

[69th_chuter]

On 2/3/2020 at 6:23 PM, busdriver said:

 

Just emphasize and hopefully not confuse. Those "little propeller doodads" also called arming vanes require a minimum TOF in order to meet the "fuse arm" requirements. What's the minimum TOF for a WWII fuse? I can not answer that. It could be an extremely short amount of time. However, with a really short TOF requirement the guy dropping at low altitude runs the very real risk of becoming a "frag mort." That is why you see pictures of SWP A-20s and B-25s making extremely low altitude deliveries dropping bombs with parachutes (para-frags). The idea is to give the bomber sufficient time to fly beyond the frag pattern of the bomb.

 

Think of the airplane as trying to outrun the explosion. How far away is sufficient? Back of the envelope numbers, a 500 pound General Purpose bomb has a nominal blast radius of 2000 feet (610 meters). A bomber flying 240 mph (385 km/h) will travel that distance in about 6 seconds. The blast fragments travel out to 2000 feet faster but not instantaneously, so if the fuse only needs 1 second TOF the delay timer would need to be a nominal 5 seconds. An instantaneous detonation could be problematic for the bomber crew.

 

The solution to not becoming a "frag mort" from a mate's bombs can be solved by one or a combination of three variables.

1) You can drop from an altitude so that you don't descend into the frag envelope.

2) You can drop with sufficient lateral offset from your mate's bombs.

3) You can drop with sufficient time delay on the bomb fuses (if in formation down low) or with sufficient time delay to allow the frag pattern to settle to earth.

And ... that's not the only potential problem with low altitude bombing ... here's an interesting video:

https://worldwarwings.com/allied-plane-breaks-apart-testing-new-bomb-heartwrenching/?a=mk&var=bounce back-ww2&utm_campaign=bounce back&utm_source=facebook&utm_medium=social&utm_term=embed-ww2-mk&utm_content=footage

[jokerBR]

On 2/3/2020 at 4:52 AM, [APAF]spartan85 said:

What was the bomb timer set to?  
I think if it’s default/contact the bomb needs a certain fall time to activate.  So dropping it too low or on the ground will not spool the timer...

delayed bombs however I think will detonate if dropped in given situation.

To put it simply, I've experienced this as well. When dropping from low alt or landed, with 0 delay they doesn't go off. Just set to 3+ seconds and you're good to go, except: 
- using large blast radius bombs and doing low level drops

- low level drop and having friendlies following at your 6

When doing 1 ton or above, I like to set 15 seconds delay.

[[APAF]VR_Spartan85]

Wasn’t there something outrageous like a 12 hour timer they used in London raids to make people think the bomb was a dud...

[Lusekofte]

I was hunting up in mountains and found a lott of artillery shells from april 1940 scattered around, some of them had timers set for a couple of hours. The specialist said it was for taking out people sure the bombardment was over

[1PL-Husar-1Esk]

40 minutes ago, LuseKofte said:

I was hunting up in mountains and found a lott of artillery shells from april 1940 scattered around, some of them had timers set for a couple of hours. The specialist said it was for taking out people sure the bombardment was over

I heard that Germans do it on purpose to kill people because  buildings where already destroyed. Bad bad .

[Yogiflight]

It was done by the british as well.

[RedKestrel]

23 minutes ago, Yogiflight said:

It was done by the british as well.

Yes, in the area bombing campaign, a certain number of bombs dropped would have delayed timers so that they would detonate long after the bombing was completed. This was meant to disrupt firefighting and emergency response and maximize destruction and casualties. Pretty horrific.

[MikhaVT]

The fuses and timers used on WWII munitions were pretty neat. People often forget that rather complex things can be achieved without the need for modern electronics (or even electronics at all!). For anyone further interested in this topic, i'd suggest reading up on the tech involved in WWII torpedoes. The kind from submarines were able to do things like: arm after a running distance, turn onto a bearing after being fired, adjust their depth to what it was set at, detonate in proximity to ships (or in the case of the US ones, detonate sometimes if changing course after arming ?.) The cost of such munitions are comparable to modern guided weapons if one accounts for inflation. 

[JtD]

This is a chart for German fuses. The Germans, as opposed to all other nations, mainly used electric fuses. They were activated by a switch in a cockpit when the bombers approached the target. Until then, the bombs were safe. The switch had two voltage settings, 150V and 240V. 150V were for horizontal bombings, with longer arming times, 240V were for dive bombing, with shorter arming times. Additionally, it could be selected if you wanted the fuse to work without delay, or with delay. Specifics were depending on the fuse. If you look at fuse 28A, you can see if you select 150V without delay, it would need 1.6 to 2.8s to arm and then detonate instantly, if you selected 150V with delay, it would need 2.1 to 3.3s to arm and then detonate after 0.15s. Interestingly, this fuse has a fallback, if the arming time is too short, it activates a third option. After 0.7 to 1.3s it would already be armed, an detonate with a 14s delay. So if you selected 150V with mV setting, and it dropped more than 1.3s but less than 2.1, it would definitely go off with 14s delay. After that, there's an increasing chance the mV setting has armed, until at 3.3s there's a 100% chance it goes off with just 0.15s delay.

 

These Vz option was intended for low level attacks, so that there'd be a short time for arming, but a long time for the aircraft to get away from the blast (including squadmates). However, with the particular fuse, standard arming times were so short, that using it was forbidden for low level bombing. No delay explosions could occur after a drop of only 5m (1.0s in the 240V oV setting). Other fuses had more options, including a setting where only long delays were possible.

 

Neat stuff, it gave the German pilots a lot more options than their Allied counterparts, it was more reliable and safer to operate. Also not really more complex, yet more flexible, reducing logistic requirements. Unless of course you were only using three types of bombs in a single type of attack anyway, in that case the flexibility would be wasted.

 

 

Other types of fuses/arming devices were built around clockworks, vanes, aerodynamic forces or safety wires attached to the aircraft pulling pins out of the bomb. Chemical fuses (long time fuses) also existed and it's mostly these which make WW2 duds dangerous even today. Broken mechanical stuff is likely to stay broken, but with chemicals you never know.

Edited February 6, 2020 by JtD

[unreasonable]

Extremely good article on unexploded bombs in Germany, covering chemically fuzed bombs in particular, here:

 

 https://www.smithsonianmag.com/history/seventy-years-world-war-two-thousands-tons-unexploded-bombs-germany-180957680/

[Finkeren]

Aside from fuses settings, it is important to keep in mind, that bombs and explosive munitions in general were (and are) made to not go off, unless triggered by the right type of fuse. A bomb accidentally falling to the ground might be scary as hell, but something has to go very very wrong in order for it to be set off. 

 

If this was not the case, and bombs could go off simply by being bumped or having their shells damaged, then big bomber formations with planes flying close to one another ladden with tons of explosives would have been completely inviable. All it would take is for one bomber to take a hit in the bomb bay to destroy half the formation. 

Edited February 7, 2020 by Finkeren