We are flooded on a daily basis with too much data and because we are in such a hurry we often don’t verify the truth of an assertion. This was brought home to me yesterday with the following exchange about damage to an aircraft (shown in the photograph below). An expert confirmed that the damage was created by a lightning strike and then made some interesting comments about aircraft and lightning.
Apparently an American Airline pilot took the photograph after the plane had suffered a lightning strike. One can see significant damage – a large hole burnt into the cockpit. The associated article goes on to say that lightning regularly strikes aircraft – the odds are that every airplane will be hit once a year. Lightning, however, has not directly caused a crash (at least in the USA) in more than 40 years. When a plane is hit, the lightning bolt merely flows along the highly conductive aluminium skin of the plane. However, 40 years ago there was a crash due to lightning: A Boeing 707, carrying 81 passengers, was struck causing the fuel vapour in a tank to ignite and explode. Systems were put in place, as a result, to prevent this from happening. In addition, all aircrafts’ electrical and electronic systems protect electrical currents from lightning damage.
But the real story and the facts....
Although the picture does represent real damage (no photoshopping here), it occurred on the ground and had nothing to do with lightning. It resulted from a cockpit fire that burned through the skin of the aircraft after external power was applied in preparation for a flight. Having looked at the pictures, one engineer - working in the area of lightning - remarked, despite the lightning assertions, that he was dubious as only an unusually powerful lightning strike could melt that much aluminium alloy. Furthermore, there should have been some distortion around the hole due to the speed of travel through the air and lightning’s electromagnetic forces. (Other photographs can be found on the link below).
So a few suggestions in your engineering work:
1. Check out anecdotal information, otherwise file it away as untested.
2. Trace and audit any data which you suspect is second hand - it may have been copied from another source and contain inaccuracies.
3. Use the ‘common sense’ test – this will quickly eliminate the faulty data or statement (as the airplane story indicates).
4. Be suspicious of any data or assumptions which appear to be ‘too clean’, predictable, smooth, spherical - nature is unfortunately unpredictable, jagged and bumpy.
5. Apply some quick calculation tests to your newly acquired data to see if it does fit
In the worse case, where the system is ‘infected’ with faulty data or assumptions, ensure you own up quickly and let everyone know so it can be rectified - this is the sign of a true professional - being honest about your mistakes.
Remember that in nature, as the venerable Mark Twain once observed with some exasperation: “Truth is more of a stranger than fiction.”
Those of you who want to view the pictures in more detail should go to:
http://www.snopes.com/photos/airplane/lightning.asp (the source of my ideas for this blog, for which I am grateful)
Yours in engineering learning