On 1 December 2021, an aerial bomb went off during ground work at Munich railway station. According to the German newspaper 'Bild', the explosive was hit during ground drilling work. Four workers were hit, one of whom was seriously injured.

Events in a row

Several unfortunate incidents involving aerial bombs are listed below. This is only an indication of the various mishaps and fortunately they do not equal the many thousands of successful clearances.


06-04-2004: aeroplane bomb, fishing boat 'Maarten Jacob', 3 casualties, bomb fished up 100 km west of IJmuiden.

06-12-2006: Airplane bomb, A3 Aschaffenburg motorway, 1 dead, road works.

1 June 2010: aerial bomb, Güttingen, 3 dead, early detonation during dismantling.

28-08-2012: aeroplane bomb, Munich, extensive damage, dismantling bomb.

24-06-2019: plane bomb, Reuver, Limburg, spontaneous smoking fire bomb

25-06-2019: Aerial bomb, Limburg an der Lahn, damage spontaneous detonation.

14-10-20: Aerial bomb, Port of Szczecin Poland, premature detonation during dismantling.

28-02-2021: Plane bomb, British city of Exeter, major damage 'controlled' destruction goes wrong.

01-12-2021: aeroplane bombing Munich station, 4 injured, work on station.

This shows that finding and or destroying aerial bombs (official term: 'throw-away' munitions) is very risky. In the Netherlands, the accidents have been minimal, but the incidents nevertheless make it clear how dangerous this form of ammunition is. It also makes clear why various ammunition detection companies have been established in the Netherlands, all of which are bound by strict conditions and laws.

Old rust

A frequently heard cry is: "...what is the point of these expensive examinations? It's all old rust, isn't it? It's been there for so long... Those bombs and grenades are so rusty: they don't do anything any more! These remarks are not justified.

An ammunition technician and EODD (Explosive Ordnance Disposal) worker knows that although the outside of an item of ammunition is usually rotten, the contents are still in working order. But how in this case can an aerial bomb still spontaneously detonate?

Different causes

The causes of detonation are various. Explosives can crystallise in the soil over the years. This can make the explosive charge very sensitive to touch.

Another example is what may have happened in Munich. An ammunition article can also be detonated by human actions. These include being hit by an auger or pile or being opened by a non-professional.

Thirdly, there are different types of detonators called ''tubes'' in the ammunition world. An example is a mechanical time tube. This tube has a firing system that can be compared to an egg timer. The time tube is preset before it is fired together with the ammunition item. The time tube is set by means of a rotating mechanism to a time just like an egg timer.

The danger of this tube is that it is not clear what time the detonator is set to and why it did not go off during WWII. For example, the timing mechanism can be blocked when the article of ammunition is dropped, causing the timing mechanism to jam. It can start up again when the ammunition article is moved.

Finally, a chemical long-time detonator may have been used in the case of ejection ammunition. This will be discussed in more detail in the next section.

Why a chemical long-time detonator on a bomb?

It is known that the Allies used a mixture of different types of bombs during their bombing raids. In other words, the bomb bay of an aeroplane contained different types of bombs with different types of detonators.

For example, brisant bombs could first be thrown down from the bomb bay. The shock waves of these huge detonations were able to shatter houses and other structures. Foundations collapsed, roof tiles flew off the roofs and this made the houses a suitable target for the next load of incendiary ammunition: fire bombs. These could easily set fire to the 'cracked' structures with protruding timber from the attics and flapping curtains.

With the brisant bombs, different tubes could also be used. A ''shock tube'', for example, was detonated when dropped on the ground. The damage done by the brisantbomb on, for example, a runway had to be repaired quickly to make the airfield operational again. The Allies were aware of this, so the chemical long-tube could be used in this kind of bombing. This tube made sure that the repair of the runway had to be postponed because of spontaneous detonations. This meant that the enemy had to wait longer for repairs in order to be sure that all bombs had exploded.

How does it work?

This section discusses the British chemical time-tube tail gun No.37.

As soon as the bomb was dropped, a safety wire pulled out of the 'gun' (the British called the bomb detonators a pistol). This allowed an impeller to rotate freely through the (falling) wind, causing a screw to move downwards in the mechanism. The screw would have hit a glass capsule in the mechanism and finally broken it. This capsule contained an acid, in the form of acetone. The acetone leaked down onto a zinc cover plate and ate through it. The same thing happened to a celluloid plate. This celluloid (also used for guitar pickups) dissolved by the acetone. However, it was this celluloid sheet which gave the free passage to a pre-stressed firing pin and firing pin spring. As soon as the celluloid was completely dissolved, the firing pin, under heavy spring pressure, struck a percussion cap and the bomb was finally detonated.

A bomb detonator could not be removed just like that. Anti-dismantling bullets ensured that the mechanism still worked as soon as someone tried to dismantle the bomb. This made this chemical long-tube extremely dangerous and unpredictable.

Very dangerous and unstable

It is now known that between ten and fifteen per cent of ammunition that is shot, dropped or otherwise used does not work. These are called duds. This includes aerial bombs with a chemically long time tube.

A dropped bomb with a chemical long-tube that lies waiting in a damp field for more than 75 years after use can become extremely unstable. The previously described celluloid plate of the pre-stressed firing pin spring can be affected by this. In this way, for example, a bomb can spontaneously explode, as it did on 25 June 2019 in the cornfield of the German town of Limburg an der Lahn. Fortunately, there were no casualties, but the surrounding population was surprised.

A story like the one above is just one of many examples of why things can go wrong with "old and rusty" ammunition. Yes, the ammunition still works and often the older it gets, the more dangerous and unstable it becomes. All the more reason for an organisation or company to call in a party such as Explosive Clearance Group B.V., because prevention is always better than cure.