Lightning, static, ammunition and refueling discussion

A little bit off topic slightly, but is there any real risk from lightning setting off small arms ammunition? And by small arms I include aircraft cannon shells.

canberra wrote:

A little bit off topic slightly, but is there any real risk from lightning setting off small arms ammunition? And by small arms I include aircraft cannon shells.

I wouldn't think the risk was significant, although an ensuing fire would do the trick! :shock:

Re the above I agree. Again OT but lightning was responsible for the loss of a very large number of barrage balloons during WWII. It was thus a very serious risk for the ground crew manning the winches. Some interesting documents in TNA on the subject - 174 were lost in July 1940 alone, and calibration equipment was then added to some balloons proving that currents of between 1,000 and 50,000 amps were measured in the balloon cable when struck. Scary stuff. :shock:

Graham

Of course the balloons had a very nice earth lead in the cable!!!

That's a very good point re barrage balloons. Presumably at this time they were still filled with highly flammable gas too?

canberra wrote:

A little bit off topic slightly, but is there any real risk from lightning setting off small arms ammunition? And by small arms I include aircraft cannon shells.

30mm ADEN gun ammunition has electrically initiated primers; they are not struck by a firing pin as percussion caps are.

The post war electrical standards for explosive storage buildings generally require it to be 'Intrinsically safe' that is all cabling and lighting enclosed within steel conduits to prevent any spark or flame from intruding into the storage or work space.

The most important change was the introduction of 'bonding' whereby a copper strap would be run around the interior of the building and connected to the external earth. This allowed workbenches with tops covered in conducting material to be connected to the bonding thus permitting the discharge of static electricity during handling. It the case of 30mm this might included inspection of unboxed ammo (normally supplied in 30 round belts) to ensure that individual rounds were correctly positioned or 'tipped' for target practice.

Adopting a standard electrical installation also permitted a change of use of the building subject to safety distance regulations and other conditions.

Arcade wrote:

That's a very good point re barrage balloons. Presumably at this time they were still filled with highly flammable gas too?

Yes; hydrogen gas was used since it was cheaper and more easily manufactured that inert gases such as helium. So flaming barrage balloons were not uncommon.

canberra wrote:

Of course the balloons had a very nice earth lead in the cable!!!

I think that it was SOP to pull the balloon down in the event of a thunderstorm. But what about the brave lad/lady on the winch!

I suppose in a way its much like todays RAF where refuelling doesnt take place when the met offcie issues lightning risk 2, and if reuelling is needed during that time if the aircrafte can be put in a hangar refuelling is done there.

PETERTHEEATER wrote:

Arcade wrote:

That's a very good point re barrage balloons. Presumably at this time they were still filled with highly flammable gas too?

Yes; hydrogen gas was used since it was cheaper and more easily manufactured that inert gases such as helium. So flaming barrage balloons were not uncommon.

I went to a hot-air balloon festival in Bristol a few years ago and got involved with inflating some gas balloons at the event. All used hydrogen as at that time helium was around ten times more expensive, (and you need more as it isn't as 'light'). What do you do at the end of your flight - let the contents escape into the air - over a grands worth. Clearly a rich man's hobby.

Scary thing for me was that the balloon envelopes weren't sealed at the bottom they were open, to allow for expansion.

Graham