Black Box

[firefly]

Is this the heaviest device in a plane?

[bhvma]

The heaviest device in an airplane by far are the engines. The black box is a shock- and fire-resistant multi-track tape recording device with many tracks, each with a constant readout of conditions on the aircraft, in addition to the cockpit voice, such as engine conditions, flight-control surface settings, guage settings, navigation info, etc..

[firefly]

But the black box is a heavy piece of machinery, in order to remain intact into the crash.

[rekstout]

Heavy does not necessarily equate to strong - cast iron is far denser than titanium but titanium is - mechanically - far stronger. The "black box" isn't much larger than a PC tower case and so wouldn't actually weigh much compared to other aircraft components such as engines, tyres, structural components etc.

[firefly]

Sorry I have no idea what a 'PC tower case' is. I would think the tyres on a plane would actually be the lightest pieces.

[rekstout]

PC as in personal computer a little bigger than an old-fashioned Video Cassette Recorder

747 Tyres weigh about a tonne apiece and there are ten of them per aircraft - remember they take the impact of 300+ tonnes of aicraft hitting the ground at about 150mph on landing.

[rja211077]

people are clearly confusing 'heavy' and 'dense'

[firefly]

Ok then, is the black box the most dense device in a plane?

[rekstout]

Not likely - it is merely one of the best protected - it is made of stronger materials which it is economically, technologically or mechanically unviable to make the rest of the aircraft out of.

The densest parts of an aircraft are probably in the landing gear struts which would be made of a high grade steel.

The survivability of flight data recorders and cockpit voice recorders is produced by provididng a housing which will cushion frim impact forces and protect from fire and water. The best way to cushion something is not to put it in a rigid box as the force of impact will transfer straight to the contents, providing crumple zones which absorb the energy, thereby transmitting less of the force of impact to the contents - that is why modern cars will crumple under impact - it reduces the G forces by providing a greater period of time for the object to decelerate.

If you have ever seen the state of a recovered black box you will note that it looks pretty smashed up - the absorb the forces of impact in order to protect the contents

[rekstout]

I apologise for the immense number of typos in my last post