Archive for December 18th, 2007

Can Lightning Bring Down A Plane?

Lightning is a scary-miraculous phenomenon we admire, we would like to know more about, we take photos of, but we are afraid of it, too. Physicists have been studying this phenomenon intensively for hundreds of years and still we do not know everything about it.

There are controversial opinions if planes are safe in lightning or not.

Pro (it is harmless)

Some say that a plane – just like a car is a Faraday cage, therefore it cannot be harmed by the external electric shock. But what is a faradya cage? According to the definition of Wikipedia a Faraday cage or Faraday shield is an enclosure formed by conducting material, or by a mesh of such material. Such an enclosure blocks out external static electrical fields. Faraday cages are named after physicist Michael Faraday, who built one in 1836. An external static electrical field will cause the electrical charges within the conducting material to redistribute themselves so as to cancel the field’s effects in the cage’s interior. This effect is used, for example, to protect electronic equipment from lightning strikes and other electrostatic discharges.

Apparently by the laws of physics planes could not be hurt by lightning. So why is it that still airospace control keeps all planes away from areas hit by heavy rainstorm and thunderbolt?

It is not just lightning that can affect a plane in a heavy strom. Lightning itself indicates huge energy, therefore it has dynamical effects as well. So besides tough turbulence caused by strong wind in stormy circumstances, lightning can also shake the plane heavily by hitting it. We took a look at the background of different accidents and it turned out that one of the main causes when a plane crashed following lightning was turbulance that smashed the planes to the ground.

Contra (it is harmful)

Some other physicists say that even though it is a Faraday cage, it is not perfect, because there are antennas for external communication like navigation, radio, etc. These antennas behave as holes on the shield and although lightening still cannot harm any passengers or interior of the aircraft, but the antennas lead this high voltage electricity into the electronic equipment of the aircraft, thus they can harm navigation, computer or electric wiring.

Among the accidents we could see a plane that cought fire following a lightning stroke in and it ignited flammable fuel vapours around the engine, which seems to be another risk factor.

Also some say that a metal object in the middle of a strom even attracts lightning, so planes are at special risk.

Result

LightningAfter all these I prefer saying it is better to avoid stormy weather, but it is not necessarily lethal flying among thunderbolt and lightning, so once you travel and experience that, you do not have to panic. On the other hand the new generation of aircrafts will be made of carbon fibre plastic that does not conduct electricity as metal does, so it will be even less dangerous. Finally we collected some accidents caused by lightning as a critical factor. They all talk for themselves, it is worth to read them through.

Highlights from Aviation Safety Netwrok’s statistics

Dornier 228-202 – Dec, 2003

Kato Air flight 603 departed Røst at 08:23 for a domestic flight to Bodø. A severe thunderstorm was passing over the Bodø area with severe winds gusting up to 40-55 knots as the flight approached the destination. At 08:52 the pilot reported that they had been hit by lightning. Apparently, rudder control was impossible due to damage caused by the lightning strike. Using engine power and elevator trim, the crew attempted to land at 08:58. This had to be aborted, so the plane circled for another attempt. On the second attempt to land, the airplane smashed onto runway 25, causing the undercarriage to collapse. The airplane sustained severe damage to the underside of the fuselage and the center part of the main fuselage was buckled. Luckily everybody survived the accident.

Merlin IV – Oct, 2001

The Spanish accident investigation commission CIAIAC concluded that the Merlin IV that crashed in the Mediterranean in October 2001 killing 10, was probably caused by a lightning strike. The aircraft was on route from Barcelona, Spain to Oran, Algeria, when it encountered a powerful electrical storm with associated rain and turbulence. The lightning strike probably caused the failure of the electrical system after which the airplane lost control.

Lockheed L-1011 Tristar 1 – Aug, 1985

Reason of crash: the flight crew’s decision to initiate and continue the approach into a cumulonimbus cloud which they observed to contain visible lightning; the lack of specific guidelines, procedures and training for avoiding and escaping from low-level windshear; and the lack of definitive, real-time windshear hazard information. This resulted in the aircraft’s encounter at low altitude with a microburst-induced, severe windshear from a rapidly developing thunderstorm located on the final approach course. 134 were killed on board and 1 on the ground. You can read the conversation of the pilots recovered from the blac box here.

Boeing 707-121 – Dec, 1963

Pan American Flight 214 departed San Juan, Puerto Rico at 16:10 EST for a flight to Philadelphia with an intermediate stop at Baltimore. The aircraft, named ‘Clipper Tradewind’ arrived at Baltimore at 19:35 and took off again after refueling at 20:24. After contacting Philadelphia Approach Control the crew elected to wait in a holding pattern along with 5 other aircraft because of extreme winds at Philadelphia. Flight 214 entered a holding pattern west of the New Castle VOR on the 270 radial.
At 20:58 Clipper Tradewind suffered a lightning strike. This caused the initial ignition of flammable fuel vapours inside the left reserve fuel tank. This triggered explosions in the centre and right reserve fuel tanks as well. Fuel spilled and caught fire; the complete left wingtip separated as a result. The aircraft was then seen to crash in flames. A ‘Mayday’ call was received by Philadelphia Approach as the plane was descending out of control.

Handley Page Hastings – March, 1960

The Hastings departed RAF Katunayake at 17:34 for a flight over the Indian Ocean to RAF Gan in the Maldives. Weather near Gan was poor with heavy rain and thunderstorm. The first approach was abandoned and the pilot decided to hold for 20 minutes, hoping the storm would pass. During the second approach a lightning flash blinded the pilots, during which the aircraft descended to a height just above the sea. The aircraft then hit the sea and crashed. Investigations found that the pilot missed some actions to avoid the accident.

By Szafi
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