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Strange Weather Radar  
User currently offlinesmartt1982 From United Kingdom, joined Nov 2007, 225 posts, RR: 0
Posted (3 years 11 months 1 week 2 days 1 hour ago) and read 6177 times:

I have seen this once or twice before and it has always been in clear weather. I have heard various reasons for it from UFOs to being scanned by a military aircraft. Any ideas?

Thanks

weather radar


20 replies: All unread, jump to last
 
User currently offlinetb727 From United States of America, joined Jun 2005, 1576 posts, RR: 9
Reply 1, posted (3 years 11 months 1 week 1 day 22 hours ago) and read 6089 times:

Looks to me like the radar was pointed at the ground real quick. I do it all the time.


Too lazy to work, too scared to steal!
User currently offlineBALandorLivery From UK - England, joined Jan 2005, 360 posts, RR: 1
Reply 2, posted (3 years 11 months 1 week 1 day 20 hours ago) and read 6024 times:

Signal being jammed/interfeared by NATO EWACS aircraft.

Not unusual in Europe

[Edited 2010-08-27 10:29:00]

User currently offlinedonniecs From United States of America, joined Jan 2007, 75 posts, RR: 0
Reply 3, posted (3 years 11 months 1 week 1 day 15 hours ago) and read 5897 times:

Looks like ground return, stabilization function of the radar might need adjusting. We had the problem a few times on our Honeywell systems on the Gulfstreams. The roll was set wrong for level flight causing ground return on one side. The effect was even greater in a turn to side with ground return. It's easy to adjust but the final adjustments had to be done in flight.

Quoting BALandorLivery (Reply 2):
Signal being jammed/interfeared by NATO EWACS aircraft.

Not unusual in Europe

This doesn't sound right, I flew around a lot in Europe for a few years and never heard of this. It would be a massive safety issue if they were and would probably included NOTAMS before hand, if this was to ever happen.

The closest you'd come to this is military aircraft being intercepted by other military aircraft, usually after permission was asked, which isn't even closes to jamming radar. Now flying over Switzerland you had no choice, the Swiss like to intercept us quite a bit and we had no say in the matter.



Charlie - Gulfstream flight mechanic
User currently offlinemrskyguy From United States of America, joined Aug 2008, 1214 posts, RR: 3
Reply 4, posted (3 years 11 months 1 week 1 day 13 hours ago) and read 5843 times:

Quoting BALandorLivery (Reply 2):
Not unusual in Europe

I could almost buy your first statement that it was a radar jam (though it does look like the same return I'd see when we pointed our Bendix to the ground, as tb727 pointed out) but why in blazes would the jamming of radar be considered more common in Europe?   



"The strength of the turbulence is directly proportional to the temperature of your coffee." -- Gunter's 2nd Law of Air
User currently offlineBALandorLivery From UK - England, joined Jan 2005, 360 posts, RR: 1
Reply 5, posted (3 years 11 months 1 week 22 hours ago) and read 5700 times:

I see it on average a couple of times a month flying around europe.

Amongst the pilot community the common perception is that the radar signal is being interfeared with by military aircraft.


User currently offlinedonniecs From United States of America, joined Jan 2007, 75 posts, RR: 0
Reply 6, posted (3 years 11 months 1 week 20 hours ago) and read 5664 times:

Quoting BALandorLivery (Reply 5):
I see it on average a couple of times a month flying around europe.

Amongst the pilot community the common perception is that the radar signal is being interfeared with by military aircraft.

I'm not saying your wrong but I must admit that I do have my doubts. I'm not a veteran flyer but I spent 4 years flying around Europe often times a few legs a day and never saw or heard of this. If it is radar interference then why is 95% of that radar sweep a good image, you can even make out some cells on the top edge of the DU along their track. If the AWACS was using a frequency that interfered with weather radar I'm sure that EASA would have been involved by now and this would be common knowledge and addressed since it is a massive safety issue. The above image looks like quintessential ground return from a radar that needs lateral stabilization adjustment.



Charlie - Gulfstream flight mechanic
User currently offlineBALandorLivery From UK - England, joined Jan 2005, 360 posts, RR: 1
Reply 7, posted (3 years 11 months 1 week 20 hours ago) and read 5643 times:

We need more experts here.

The thought is that the direction of the cone is the direction the 'other' aircraft is in.

I have no proof/source for info other than what is commonly thought of amonst crews.


User currently offlineeisenbach From Austria, joined Mar 2001, 110 posts, RR: 0
Reply 8, posted (3 years 11 months 1 week 18 hours ago) and read 5592 times:

As a meteorologist I just can give you an example from our "ground view". These cones appear quite often (many times a day) at our ground based weather radars - so it's nothing unusual for us. I have to ask my colleagues for the exact reason.

Here an example from the actual weather radar network in Austria:

Weather Radar Austria, UBIMET (ubimet.com)


Down in the middle of the picture you see a streak of weaker precipitation. The reason for this radial error is, that this particular radar is situated near a mountain top south of the station. So you "see" the shadow of the mountain.

At the second picture (sorry, I couldn't upload it, because of size restrictions here at this site) you finally see the same pattern as shown at the weather radar on the plane:

http://photos.eisenbach.at/upload/Radar2.PNG

These streaks are also pointing away in radial direction from the weather radars. I don't know the cause, but these errors last normally not longer than for 1 to 10 scans. I only know that the radar is sensitive to the atmospheric layering and the radar beam can bend quiet much vertically, dependent on the temperatures in different heights.

Sorry that's all I know for the moment.



Do228, Saab340, Twin-Otter, C212, Fokker50, AN24, ATR42, ATR72, Dash8-400Q, MD90, MD83, EMB120, A300, A343, B721, B743,.
User currently offlinefrancoflier From France, joined Oct 2001, 3739 posts, RR: 11
Reply 9, posted (3 years 11 months 1 week 6 hours ago) and read 5423 times:

I have seen those kind of returns quite a few times flying over Germany, but they also happen when flying near other major cities. They always seem to originate from the downtown area of a major city (Munich in this case).

I have always theorized that the building layout of some cities produced very good radar wave reflectors (large flat surfaces perpendicular to each other and to the ground, forming hollow pyramid shapes, like omnidirectional trihedral reflectors or 'corner reflectors'. Though why it happens in certain cities more than others, I don't know. And it wouldn't explain that exact shape of return.

Then again It might also be some kind of electromagnetic interference from a city based source. Maybe a strong transmitter that emits similar wavelenghts. Ground based doppler weather radar?

It happens when scanning over downtown FRA, amongst others.



Looks like I picked the wrong week to quit posting...
User currently offlineflybaurlax From United States of America, joined Oct 2008, 638 posts, RR: 0
Reply 10, posted (3 years 11 months 6 days 20 hours ago) and read 5305 times:

Once on a flight from LAX-SEA we had a blob following us on the wx radar. We figured there was something stuck on the actual dish or within the nosecone. It wasn't the display as it would disappear when the Capt turned the radar off. We came to the conclusion that something was obstructing the radar.


Boilerup! Go Purdue!
User currently offlinefr8mech From United States of America, joined Sep 2005, 5360 posts, RR: 14
Reply 11, posted (3 years 11 months 6 days 20 hours ago) and read 5284 times:

In the old days (pre-color and terrain matching) this was called spoking.

Sometimes a fault, sometimes just an anomalous event.

That's what it looks like too me.



When seconds count...the police are minutes away.
User currently offlinedonniecs From United States of America, joined Jan 2007, 75 posts, RR: 0
Reply 12, posted (3 years 11 months 6 days 10 hours ago) and read 5176 times:

Quoting fr8mech (Reply 11):
In the old days (pre-color and terrain matching) this was called spoking.

Sometimes a fault, sometimes just an anomalous event.

I also forgot the obvious (as I did once while troubleshooting), that it can come from moisture that made its was into a delaminated area in the radome. We racked our brains for a week once trying to figure out why an aircraft was getting an almost identical image to the above, finally swapped out the radome and the problem was solved.



Charlie - Gulfstream flight mechanic
User currently offlineYWG From Canada, joined Feb 2001, 1146 posts, RR: 2
Reply 13, posted (3 years 11 months 5 days 14 hours ago) and read 4978 times:

Quoting donniecs (Reply 6):
The above image looks like quintessential ground return from a radar that needs lateral stabilization adjustment.

I agree. Looks like she's painting ground. Not sure what model this radar is but.....
If you roll while the radar has a fairly downward angle scan, it will paint the ground just as it appears to be doing in this picture. I'm not that familiar with advanced auto stabilized radars but I'm just saying it does happen on some radar i've dealt with.



Contact Winnipeg center now on 134.4, good day.
User currently offlinefr8mech From United States of America, joined Sep 2005, 5360 posts, RR: 14
Reply 14, posted (3 years 11 months 5 days 12 hours ago) and read 4942 times:

Looking at it further, and not knowing the ins-and-outs of the newer Wx-RADAR systems:

I don't think it's painting terrain, because terrain isn't annunciated on the EHSI. I see that the system is in WX-T mode, which, if I recall correctly, is turbulance mode. Or am I missing something?

This code be ground clutter, but it doesn't look like any ground clutter I've seen.



When seconds count...the police are minutes away.
User currently offlineGLEN From Switzerland, joined Jun 2005, 221 posts, RR: 2
Reply 15, posted (3 years 11 months 5 days 1 hour ago) and read 4828 times:

Quoting YWG (Reply 13):
If you roll while the radar has a fairly downward angle scan, it will paint the ground just as it appears to be doing in this picture.

Definitely not. Ground clutter would not paint such a sharp cone with its tip right at the aircraft. It is circular around the aircraft like here:






When you bank the a/c, the ground clutter would just be more pronounced on the side you are rolling into.

I've seen these cones like in the thread start several times and when, they appear just a few seconds and then disappear again.
Like mentioned before, I've been told this is interference with another strong radar - but I can't say for sure, if this is the correct answer. At least it seems reasonable...

Quoting fr8mech (Reply 14):
I don't think it's painting terrain, because terrain isn't annunciated on the EHSI. I see that the system is in WX-T mode

Even in WX-T mode the radar will show ground clutter like in the picture above.



"The horizon of many people is a circle with zero radius which they call their point of view." - Albert Einstein
User currently offlinefr8mech From United States of America, joined Sep 2005, 5360 posts, RR: 14
Reply 16, posted (3 years 11 months 5 days ago) and read 4801 times:

Quoting GLEN (Reply 15):
Even in WX-T mode the radar will show ground clutter like in the picture above.

I understand that it will paint ground clutter, but will it overlay the terrain data? I'll be near an MD11 sim tomorrow and see if I can get a look.



When seconds count...the police are minutes away.
User currently offlineGLEN From Switzerland, joined Jun 2005, 221 posts, RR: 2
Reply 17, posted (3 years 11 months 5 days ago) and read 4792 times:

Quoting fr8mech (Reply 16):
I understand that it will paint ground clutter, but will it overlay the terrain data?

Ah sorry, I did not understand you talking about terrain from the EGPWS. So you are right, it is in WX-T mode and therefore does not display terrain data. On the planes I know you can't overlay terrain data an WX-data - this would be too easy to get confused...



"The horizon of many people is a circle with zero radius which they call their point of view." - Albert Einstein
User currently offlinefr8mech From United States of America, joined Sep 2005, 5360 posts, RR: 14
Reply 18, posted (3 years 11 months 4 days 23 hours ago) and read 4763 times:

Quoting GLEN (Reply 17):
Ah sorry, I did not understand you talking about terrain from the EGPWS. So you are right, it is in WX-T mode and therefore does not display terrain data. On the planes I know you can't overlay terrain data an WX-data - this would be too easy to get confused...

That's what I was thinking. So, this isn't a terrain paint. It really doesn't look like ground clutter. I can't speak to jamming, but I would expect a screen full of hash and not such a directed beam.

I'm thinking a fault. Spoking?



When seconds count...the police are minutes away.
User currently offlineAAR90 From United States of America, joined Jan 2000, 3466 posts, RR: 47
Reply 19, posted (3 years 11 months 4 days 22 hours ago) and read 4762 times:

Quoting BALandorLivery (Reply 5):
Amongst the pilot community the common perception is that the radar signal is being interfeared with by military aircraft.

Close, but not accurate. Tactical & strategic radar use a different frequency band because the "target of interest" is other aircraft, not weather.

Quoting GLEN (Reply 15):
Like mentioned before, I've been told this is interference with another strong radar - but I can't say for sure, if this is the correct answer.

The "interference" is being caused by another airborne WX radar that is using the same (or VERY CLOSE to the same) frequency [and other characteristics]. If your radar is in "listen" mode at that particular instant in time AND is pointed in the right direction at that particular instant in time, it will see (and display) ALL the energy of the transmitting radar it receives. It gets "spooked" (or "jammed") into believing all that energy is a "return" echo.

Considering the number of WX radars in use and the limited number of "optimal" frequencies (and other design parameters) to "see" weather that are available, it is actually surprising we don't see this more often than we do. I see it at least a half-dozen times a month during the summer --thunderstorm season in USA.

Quoting BALandorLivery (Reply 7):
We need more experts here.

Does an ex-Hawkeye driver (Instructor, Natops Officer, ASO, and PacFlt Evaluator) suffice?



*NO CARRIER* -- A Naval Aviator's worst nightmare!
User currently offlineGLEN From Switzerland, joined Jun 2005, 221 posts, RR: 2
Reply 20, posted (3 years 11 months 4 days 22 hours ago) and read 4750 times:

Quoting AAR90 (Reply 19):

Tks a lot for the info.



"The horizon of many people is a circle with zero radius which they call their point of view." - Albert Einstein
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