Go Back  PPRuNe Forums > Flight Deck Forums > Tech Log
Reload this Page >

How harmful is Wx radar?

Tech Log The very best in practical technical discussion on the web

How harmful is Wx radar?

Old 24th Jul 2019, 01:07
  #41 (permalink)  
 
Join Date: Sep 2007
Location: New York
Posts: 224
Likes: 0
Received 0 Likes on 0 Posts
PWS regularly triggers on the taxi out in Denver.... Honewell RDR 400. Its not kidding either....its on as soon as we move off the ramp...
neilki is offline  
Old 24th Jul 2019, 04:45
  #42 (permalink)  

Only half a speed-brake
 
Join Date: Apr 2003
Location: Commuting not home
Age: 46
Posts: 4,303
Received 3 Likes on 3 Posts
Another idea to consider: Are today's radars equipped with a safety guard against inadvertent operation on the ground in close presence of liveware? Or any health warning in the manuals? There is one on McD's coffee..
FlightDetent is offline  
Old 24th Jul 2019, 05:33
  #43 (permalink)  
 
Join Date: Jul 2006
Location: Somewhere over the rainbow
Posts: 944
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by FlightDetent
Another idea to consider: Are today's radars equipped with a safety guard against inadvertent operation on the ground in close presence of liveware? Or any health warning in the manuals? There is one on McD's coffee..
Exactly. No safety guard or warning in case you forgot the radar after engine shutdown. As they know it’s not hazardous. If weather radar was dangerous, they would had have installed those safety features.
pineteam is offline  
Old 24th Jul 2019, 06:05
  #44 (permalink)  
 
Join Date: Jun 2007
Location: Wanderlust
Posts: 3,396
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by pineteam
Exactly. No safety guard or warning in case you forgot the radar after engine shutdown. As they know it’s not hazardous. If weather radar was dangerous, they would had have installed those safety features.
The older generation radars weren't safe but still there were no safeguards. Only there was caution to the operator not to use it.
vilas is offline  
Old 24th Jul 2019, 07:47
  #45 (permalink)  
 
Join Date: Jul 2006
Location: Somewhere over the rainbow
Posts: 944
Likes: 0
Received 0 Likes on 0 Posts
True that master!
pineteam is offline  
Old 24th Jul 2019, 10:44
  #46 (permalink)  
 
Join Date: Nov 1999
Location: UK
Posts: 2,471
Received 84 Likes on 49 Posts
RADAR is an acronym: RAdio Detection And Ranging.

Some folk are nervous about (modern) weather RADAR - I have had pilots turn to me and say “ shall we turn the RADAR off to save our gonads?” People get freaked out by the terms ‘RADAR’ and ‘radiation’ and ‘beam’, possibly imagining something from their early comic reading and ‘death rays’ etc. All of this is bogus. Modern weather radar is low power, and the “radiation” is non ionising and is actually the same as visible light but at a lower frequency.

So think of a weather radar as simply a car headlight on high beam shining out in a series of short flashes, and a very very sensitive receiver looks for any reflections to that light during the gaps between the flashes.

Modern weather radar is low power: 100-150W has been quoted. The frequency used is around 10GHz, or 10,000,000,000 cycles per second, which is the resonant frequency of the water molecule, since water is what we want to detect.

Power of a transmitter reduces according to the inverse square law, so the power drops at 1 divided by distance squared, (sorry, I don’t know how to write equation format on this forum). So at a distance of 2 meters, the power received is 1/(2x2) = 1/4. So if the transmit power is 100 Watts, then at 2m it has already reduced to 25W. The equivalent car high-beam power has reduced to a car brake light power at 2m away from the aerial.

If you put your hand at the radar antenna, it might feel warm, similar as it would feel doing the same thing on your car with the lights on full beam. The only thing is that since the radar frequency resonates water molecules, unlike the car headlight, the weather radar could cause more heating in anything containing water, e.g. humans.

But, as I say, only about 100 Watts, so as long as you don’t put your eyes any closer than a couple of meters to the radar antenna, you should be safe.*

The problem with metalwork is that if part of the metalwork happens to be the same physical dimensions as the radar frequency wavelength then sparking might occur, which could be hazardous if fuel fumes are present. This is also why cellphones are prohibited at petrol stations - there is, (a very low risk that), sparking caused by cellphone transmissions could ignite petrol fumes.

Back in the cockpit, those pilots who worry about the weather radar affecting their gonads are behind the radar antenna, which is simply a reflector - like a mirror, so probably no radar waves reach us at all.

Since the radio output of a radar is focussed into a “beam” some say it magnifies the power. It doesn’t. The power remains the same, but the energy is focussed in one direction compared with an omnidirectional antenna. And the “beam” is not pencil like as in a l@ser beam; it is relatively wide, about 30cm diameter, and remember the reduction of power with distance. The safety exposure limit for skin is 10mW per sq centimetre.

* I am much more careful about not looking into a microwave oven - 750 W only 10cm away from your eyes is much much more dangerous. I stay well back, and don’t rely on the microwave oven RF shielding to protect me.

Last edited by Uplinker; 24th Jul 2019 at 13:46.
Uplinker is online now  

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 On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.