Visible radar beams ?

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Airframes

Benevolens Magister
63,027
12,576
Aug 24, 2008
Cheshire, UK
Not sure if this should be here, or in the 'Technical' section, but here goes.

Today, I noticed something that I've seen before, in certain atmospheric / meterlogical conditions.
An aircraft at around 20,000 to 30,000 feet, in this case travelling north west, with some high-level haze ( possibly at the same altitude or below the aircraft), lightly contrailing, in an otherwise clear blue sky, full daylight.
Temperature at ground level at the time was around 14 degrees C, with ground level being around 1000 feet ASL at my location.
Reaching in front of the aircraft, immediately from its nose, for a distance of maybe a mile or two (guesstimate, given scale of view), there was a feint, but visible and distinctive band, rather like a shadow, which was slightly darker than surroundings. This 'band' was maybe the width of the aircraft fuselage, or slightly less, and angled out at no more than maybe 10 or 15 degrees from the centerline of the band, so a maximum spread of around 20 to 30 degrees at the extremity of the visible band.
To visualise this, think of the narrow beam of a weak flashlight, shining through a thin veil of smoke.
As mentioned, I have seen this before, a few times, and have often wondered whether it's related to weather conditions (like a rainbow, for example), or the effects of the radar onboard the aircraft concerned.
Anyone have any experience of this, or an explanation ?
 
Can I have some of what you're smoking Terry?

Seriously, I've never heard of such a thing though the closest I can think of is the effect of having a halo around an aircraft's shadow. That's something I've seen many of times from the air but never from the ground.
 
Terry, the only thing that I can think of is the compressional condensation caused by the aircraft "plowing" through the air. The only problem is that it occurs around and after the wings


Or the wing tip compressional vorticies seen in jets

 
Thanks for the response chaps.
This, when I've seen it, is nothing like condensation, or any other form of moisture or air disturbance.. Although obviously not, it has the appearance of an almost solid 'beam', in front of the aircraft, like a pale grey beam of light, even though that would not be possible.
I have absolutely no idea how this can occur, unless, perhaps, it is the effect of the angle of the light, possibly on moisture molecules, somehow "illuminated" by the radar beam ?
At the time seen today, the aircraft, as already stated, was heading approximately north west, and the sun was in the west, time being around 15.00 hrs in north west UK.
 
No - aircraft heading roughly north west, more NNW,, with the sun in the west, so more or less at it's port side. So no, not a shadow of the aircraft.
 
I heard it said, but I have no idea if it's true that the old DEW system radar systems in the north could give birds that strayed too close, too long, to the radar dishes would fall out of the air, and die. Semi cooked.

What about the fighter pilots here, was there any precautions took with the radars transmitting when on the ground with ground personnel in front of the dish ?
 
tyrodtom said:
would fall out of the air, and die. Semi cooked.
Click to expand...
Microwave energy will cook living tissue as well as dead issue. Most home use microwaves are between 1kW -2kW and door interlocks prevent them from running with the door open or unlatched. I recall an incident in 1977 or so when two waitresses claimed that a commercial "RADAR" range had given then deep tissue burns of their hands when they removed food from the oven.
I also recall a "story" about a MIG-25 Foxbat. It had a vacuum-tube directional RADAR rated at 600kW. When turned on it could almost instantly kill rabbits 500 steps from the aircraft if one wandered into the beam . The RADAR's power unit produced so much heat that it had its own alcohol cooling unit...MiG-25 bases were very happy places
Raytheon engineer Percy Spencer "invented" the "RADAR" range about 1946 or so. While working in a lab where magnetrons were being worked on/tested he felt a chocolate bar in his pocket melt. To test his "cooking" theory he brought a bag of popcorn near a functioning magnetron. The popcorn exploded.
The next day he tried an egg which exploded as well
 
In the 1960-70s Air Weather Service deployed the AN/TPQ-11 ultra-high frequency K-Band (0.86 cm) radar with two fixed dishes aimed vertically designed to display and record cross-sections of clouds directly above the airfield at select locations. Besides tipsy airman tossing beer cans into the reflectors frying the diode banks and magnetrons birds perching on the rims and then falling into them doomed it to early hanger queen status.
 
May be an artefact of the particular type of polarizing coating applied to the glazing. Your best bet would be to pitch the question to one of the photography forums to see if any can offer an optical explanation for the phenomena.
 
Well, I was trained in Professional, audio-visual and graphics photography, working in the industry for many years with a major manufacturer, and I can't see a viable connection.
It was as if moisture in the air was creating a well defined beam, rather like a beam of light, but a pale grey in appearance, similar to a shadow on a cloud when looking down - but this was looking up !
 
I am certain there was a reader's letter about this phenomenon in Flight magazine which I saw in the late 1950's. It was followed up by a small very grainy image taken from ground level of a B 47 at altitude with what appeared to be a visible beam projecting ahead from the nose. I recall that the original letter was captioned Death Ray? or some such attention grabbing description. At the time B 47's were a common sight over the UK and I was lucky enough to see the so called ray myself on one rare occasion over Devon.

The explanation published in Flight was quite simple. What appeared as a ray ahead of the aircraft was in fact the shadow of its own vapour or condensation trail being cast by the sun on a lower haze level. If the alignment was perfect and the observer was in the right position the phenomenon appeared.

I wish I could be more specific about the date. All I can say is that I started taking up Flight weekly from about 1956 to about 1965. I have not searched the Flight Global archive on line. Does it still exist? If you are so inclined and assuming it includes readers' letters you might start by searching for Death Ray.
 
Thanks for that, and it makes sense.
However, when I saw this, and on those few previous occasions, the aircraft concerned was a four-engine airliner ( 747 for example, and one which might have been a KC-135)) contrailing from each engine pod.
In this latest sighting, the sun was at approximately 90 degrees to the port side of the aircraft, and getting low in the sky to the west (maybe 30 to 40 degrees as viewed from ground level), so didn't appear to be above the aircraft at that altitude, but perhaps level with it.
Bit strange to cast a shadow, from four trails, in front of the aircraft at those angles.
 
Maybe the sun reflected off the fuselage and onto lower water vapour ahead of the aircraft. In that case it wouldn't be a shadow but a shine reflected off water droplets.
 
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