The Straight Dope

Go Back   Straight Dope Message Board > Main > General Questions

Reply
 
Thread Tools Display Modes
  #1  
Old 12-16-2002, 04:56 PM
Gaudere Gaudere is offline
Moderator
Moderator
 
Join Date: Jul 1999
Posts: 6,111
What happens to a helicopter when lightning strikes it?

Does it crash? Are the people inside fried? What about when lightning hits an airplane? How common is being struck by lightning if you are high in the air during a storm in a large metal object?
Reply With Quote
Advertisements  
  #2  
Old 12-16-2002, 05:10 PM
Richard Pearse Richard Pearse is online now
Member
 
Join Date: Aug 2001
Location: Kiwi in Adelaide
Posts: 8,115
We were struck by lightening recently (in a fixed wing aircraft). By that experience I can say that some of the electrics get temporarily fried, turning them off and then back on fixed the problem; and you get lots of little scorch marks over the aircraft. Other than that, no big deal. It is not very common to get struck by lightening, mainly because flying through thunderstorms is best avoided due the extremely turbulent conditions inside them, and hail and icing etc.
Reply With Quote
  #3  
Old 12-16-2002, 05:14 PM
Richard Pearse Richard Pearse is online now
Member
 
Join Date: Aug 2001
Location: Kiwi in Adelaide
Posts: 8,115
Lightning even.

YMMV of course, some cases may be a lot worse than ours. There's no reason for people to be fried though.
Reply With Quote
  #4  
Old 12-16-2002, 05:19 PM
sailor sailor is offline
Guest
 
Join Date: Mar 2000
My boat was hit by lightning and no electronics survived. Not even things which were not connected to anything. Everything fried. I am glad I was not onboard at the time.
Reply With Quote
  #5  
Old 12-16-2002, 06:21 PM
Broomstick Broomstick is offline
Charter Member
 
Join Date: Mar 2001
Location: NW Indiana
Posts: 19,037
I wouldn't say aicraft (of any sort) get hit by lightening is common, but it does happen. Things like passenger jets undergo extensive testing that not only includes (dead) chickens lobbed at the windshield by cannon but also testing of resistance to damage from lightning.

Small airplanes intended to fly extensively in "instrument meterological conditions" also undergo some similar tests, although not as extensive.

(Instrumentation to help detect lightning dangers at a distance and avoid it is also available to pilots, although not all small planes have this installed.)

In general, while the electrics may suffer, the occupants generally survive unscathed, although perhaps shook up from the flash of light, possible accompanying >BANG!<, and blinking/failing instrument panels lights and such. Or maybe it won't affect the electricals at all.

The BIG electrical danger in aircraft comes form the possibility of a difference in static charges between the aircraft and the fuel truck leading to a spark around gas fumes. Which is why, when refueling, a grounding wire is strung between the truck and the aircraft, to even out any differences in charge.
Reply With Quote
  #6  
Old 12-16-2002, 06:27 PM
happyheathen happyheathen is offline
BANNED
 
Join Date: Nov 2001
Posts: 2,394
All of the above are assuming the aircraft is metallic, or otherwise conductive (being on a wooden/fiberglass boat during a lightning strike is not advised).

In the case of a composite plane (without the new, rare, expanded metal groundplane), the answer I got when I asked about the result of a strike was "You're toast". This was the guy selling the kit.
Reply With Quote
  #7  
Old 12-16-2002, 06:31 PM
kanicbird kanicbird is offline
Guest
 
Join Date: May 1999
sorry to hear that sailor. The difference is that your boat provides a path directly to ground (I assume salt water) so had a great potential difference. An aircraft offers no such difference in potentail and results in (usually) little dammage.

Glad you survived it.
Reply With Quote
  #8  
Old 12-16-2002, 09:00 PM
bbeaty bbeaty is offline
Guest
 
Join Date: Aug 1999
When lightning hits aircraft, it doesn't "strike" the aircraft, instead it starts out on the aircraft and leaps outwards.

You'd think that a lightning bolt would have a hard time finding a tiny plane in those cubic miles of atmosphere. But since the airplane strikes the thunderstorm instead of vice versa, lightning on planes is much more common than you'd think.

Analogy: Stress a piece of glass by stretching it, but not so hard that it breaks. If you press the tip of a nail into the stressed sheet of glass, cracks will start at the nail tip and race outwards. The glass is like the space around a charged thunderstorm, the stresses in the glass are like the intense voltage-field in the air, and the airplane supplies the "defect" which concentrates the forces in one spot and starts the "cracks."

Once a crack has started in glass, the concentrated stresses at the tip of the crack will keep it getting longer. And once a lightning bolt has started in the e-field near a charged cloud, the concentrated e-field at the tip of the bolt keep it going.
Reply With Quote
  #9  
Old 12-16-2002, 09:17 PM
Race Bannon Race Bannon is offline
Guest
 
Join Date: Oct 2000
I'm no electricity expert, but I do know that in military helicopters, care is taken to design for lightning strikes. Composite materials (especially blades) are designed to be conductive, even if material is added just for that purpose. Bonding straps are provided between components. Testing is even conducted on things like blades and such to see if there are any problems.
Reply With Quote
  #10  
Old 12-16-2002, 11:27 PM
Bob55 Bob55 is offline
Guest
 
Join Date: Sep 2002
Ever seen those guys that dangle outside helicoptors to fix huge electrical wires way out in the wilderness? They touch it with a stick first and the electricity goes thru the stick, through the holder, and into the helicoptor, creating an equilibrium state. I'd guess being hit by a lightning bolt in the air is similar. Also, since the electricity has no where to go, there's no reason it would want to hit the helicoptor, lightning bolts like to find charges from the ground to release their energy to.
Reply With Quote
Reply



Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 09:27 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.

Send questions for Cecil Adams to: cecil@chicagoreader.com

Send comments about this website to: webmaster@straightdope.com

Terms of Use / Privacy Policy

Advertise on the Straight Dope!
(Your direct line to thousands of the smartest, hippest people on the planet, plus a few total dipsticks.)

Publishers - interested in subscribing to the Straight Dope?
Write to: sdsubscriptions@chicagoreader.com.

Copyright 2013 Sun-Times Media, LLC.