weird weather radar indication on an A320 (picture attached)

[GIVMI55W]

Hi,

we had an unusual indication on the ND (weather radar). The captain said this is how it looks when a fighter jet is directing its radar beam towards us. Is that true? Do fighter jets even have a weather radar? If it wasn't a fighter jet, what causes this indication?

Thanks :)

[compressor stall]

FCTM-AS-WXR-analysis of weather radar.

The image is almost identical to yours, look up the answer to get familiar with the books (or iPad).

[First.officer]

Think Airbus refer to that anomaly on Wx Radar as 'spoking' or 'alien radar'...and define it as interference from an external high power radio frequency that operates at a frequency next to that of the weather radar itself.

FCTM has a reference; FCTM SI-070-ANALYSIS OF WEATHER RADAR DATA

:ok:

[First.officer]

compressor_stall beat me too it lol....

[Dufo]

Weird things happen around ETxx (military airfields). Must be some interference.

[compressor stall]

Yes, snap. But at least he has the old and the new FCTM references!

[wiggy]

Something at an unknown distance along the azimuth of the "spoke" on the screen is pushing out RF energy and your weather radar is displaying it, now it might just be another weather radar though as I understand the designers have methods of reducing the chances of that happening, otherwise you'd see them all the time.......OTOH your captain could be correct, it could indeed be something higher powered such as a fighter's radar (they do have them, but not a weather radar, it is used for interception and other purposes) a ground based radar, perhaps military, or perhaps it is the result of a jamming exercise, again for the military.

For some of us who had a another line of work before our civvie flying days those spokes bring back memories (and cold sweats) of time of groping around in the clag and darkness in an attempt to trying to find whatever it was that was producing the phenomenon.

[misd-agin]

High powered military radar. We get those near military bases.

[750XL]

Friend of mine had similar on a 737NG the other day, said it was radar jamming?

[wiggy]

" said it was radar jamming?"

As I mentioned earlier that's one of several possible options; some forms of jamming, especially basic "area" noise jamming does produce "spokes" on radar displays and the military do ( or certainly used to do) jamming exercises at times for training purposes but probably/hopefully not on a frequency and/or not with enough energy to significantly interfere with the commercial weather radars in the adjacent airspace..

[Capn Bloggs]

AP2's not holding the altitude very well!

[Metro man]

I was told that spoking indicated the radar was likely to fail in the near future, i.e. an indication of a problem.

[Uplinker]

I don't think so. The 'spoke' is a transmission from a fixed point, e.g. another radar dish. To be seen on our airborne weather radars, the source of the 'spoke' transmission would have to be on the same frequency, i.e. about 10GHz. I don't know what frequencies military primary (i.e, non weather) radars use.

The power would not have to be very high though: The weather returns we see on our own radar are reflections from rain drops from our transmissions of about 100-200 watts of transmitted power, so a tiny tiny signal level coming back.

[G0ULI]

Classic radar interference from another transmission source on the same frequency.

[noflynomore]

How do we explain multiple spokes - I've seen six or seven at a atime arrayed symmetrically across the screen.
(Over central Scotland iirc)

[wiggy]

Seen it once or twice on commercial weather radars, on older radars on jamming exercises it was due to RF Energy getting into the sidelobes.

[tubby linton]

Used to see this a lot inbound to Cuba. An ex fast jet colleague reckoned we were being painted by the local air defence using a high flying Airbus for practice.

[physicus]

It's radio frequency interference (RFI) - you most likely got painted by a military system using you for target practice. It's unlikely to be another WXR as the pulses are uniquely encoded so as to avoid that exact problem.

[Superpilot]

And the other day our Rhine friends had this in their sector right in the middle of several storm cells. We were getting rubbish returns from nearby cells. My theory is they can saturate or use up a wx radar's capability to report real threats. Needs to be resolved.

[D-OCHO]

What a BS. It is a problem with your radar. Try moving the tilt up and down fast you will get the same but multiple spoke patterns.
If it happens next time move the tilt up and down slowly and hope it removes the spoke.

[giggitygiggity]

AP2's not holding the altitude very well!

I know this is off topic but it looks like it's doing a pretty good job to me. 20ft is insignificant, the FMA shows it's in ALT CRZ which means it's in the soft cruise mode so the altitude can drift a little to avoid unnecessary trust and pitch changes to make the ride more comfortable.