Radar Screens and Aircraft 'blips'
 

Hello all,

Question from a pilot to all you controllers.....

Are there any circumstances under which a controller may not see the 'blip' of an aircraft on his/her screen?

e.g. 2 aircraft cruising in the airspace of a large European nation, both at the same FL on reciprocal headings in the same airway.

Thanks very much!

SC

Yes - lots of reasons. Depends on type of radar, mainly primary or secondary, and in the latter case whether the aircraft is transponding. With primary, the strength of a target can vary substantially for no immediately obvious reason.

Also, on the display, certain targets may be filtered out routinely although the controller can always 'unfilter' a target if he/she needs to.

I believe there's also been an occasion when an incident occurred, involving a biz-jet and an a/c of composite construction. IIRC, the latter's airframe did not provide a usable primary echo, whilst its single SSR aerial was shielded (from the ground interrogator) by the attitude of the a/c at the time. As usual, the 'holes lined up'. It may not be a common occurrence, but there's more and more of them out there.

There are areas without proper radar coverage, both primary and secondary. These areas are usally below MSA.
There is also a "cone of silence" directly above the radarsite.
Aircraft on reciprocal tracks are not on the same level. If for some reason the tracks are both east- (or westbound), and both a/c are on the same level, the controller is there to ensure separation.

Are you afraid of flying? :p

Thanks for the responses so far guys...

Supraspinatus,

Yeah, I know that when on reciprocal tracks, aircraft aren't meant to be at the same level, but when you get a "Traffic, Traffic... Decend, decend" at FL350, someone has messed up!

There are also places in the UK FIR which do not have radar coverage nd are procedural enviroments at all levels

"Yeah, I know that when on reciprocal tracks, aircraft aren't meant to be at the same level, but when you get a "Traffic, Traffic... Decend, decend" at FL350, someone has messed up!"

It could also be that the other aircraft is not at the same level but is within close proximity with a high climb or decent rate! TCAS could just as easy be triggered in these circumstances

The most common reason for TCAS RA is level busts in busy sectors.

Back to your question: Are there any circumstances under which a controller may not see the 'blip' of an aircraft on his/her screen?

There are many. Is there a specific incident you are thinking of? May be easier to answer if I knew why you where asking.

sharpclassic: the obvious isn't always what it seems. If you have had an incident then don't assume anything - if the other traffic was military then you are in a completely different set of rules and regulations.......

Not assuming anything but that does answer quite a few questions such as yours. :ouch: