Minimum Radar Vector Altitude protection?

[Weary]

Simple question;

A transponding aircraft is subject to an approach control service and is generating a mode C return on the radar display. IF, for whatever reason, he descends below the minimum assignable radar vector altitude for his position, will there be any bells, lights, whistles or whatever generated by the radar hardware/software independent of any ATC intervention?

Thanks in advance.

Weary

[Chilli Monster]

No, not in the UK (though a mode 'C' driven system is in use in some parts of the USA - google "MSAW" for more info). ATCO monitoring mode 'C' is the order of the day.

[Weary]

Thanks Chilli

In a previous life (years ago.....) as an ATCO overseas, I recall having a conversation with someone from Thomson CSF about what was possible with radar technology as it moved increasingly toward computer interpreted and generated display hardware. This feature was mentioned as being possible - I was wondering if it had been realised anywhere.

Regards.

[Blockla]

MSAW is active in Australian TMAs. But the CLAM alert (system monitoring of Cleared vs Actual Level) is always the first to be activated. Generally the MSAW goes off in error, or during the final approach phase (eg descending on the ILS) which makes it more or less useless. Various types of approach clearances or categories or flight or suppression areas also filter its effectiveness.

[PeltonLevel]

But if controllers can't be a***d to enter information such as cleared levels into the computer systems, there's nothing to compare the Mode C to!

[Spitoon]

From my limited experience every MSAW implementation has a high rate of false alerts and thus has limited value as a safety net. Route/Clearance adherence tools are workable in many en-route environments where flight data is maintained and transferred electronically as a matter of routine but are less practical in most approach environments - probably for the reason suggested by PeltonLevel as much as anything else.

[GetTheFlick]

Weary,

My favorite sector in Atlanta Center was the WILKES sector in western North Carolina (NW of KCLT.) It was really nothing more than an Approach Control in airspace that wasn't busy enough to justify having it's own Approach Control. It was 80 x 100 miles at 10,000 feet and below.

Anyway, at the Centers in the States we have MSAW -- Minimum Safe Altitude Warning. It is based on the MIA --- Minimum Instrument Altitude (which is slightly different than the Minimum Vectoring Altitudes used by Approach Controls.) If the aircraft descended below the MIA the datablock would blink on the scope. I think it was quite effective.

The alert could be surpressed and the parameters were locally adapted. Atlanta Center got its hand slapped when it was discovered that it had the MSAW suppressed within 50 miles of the destination. I think they changed it to suppress the alert within 10 miles of the destination airport.

Nuisance alerts could be a problem. An aircraft shooting practice approaches at an airport other than its destination could make you nuts. ;) Between that and the Conflict Alert on VFR traffic, I've seen a half dozen data blocks flashing all at once. But all in all, I think it was a desirable feature.

Don Brown

[Skyjuggler]

Hi Weary,
I feel your question has already been answered at length but here's my 2 cents:
At my station (Thales operated), the MSAW function is turned off, due to the large number of incorrect alarms. There are many situations here when an acft may decent below minimum radar terrain such as visual approaches. We tend to hold quite a bit of stock in the CLAMs (Clearance Limit Adherance Monitor). A lot less invasive (just a yellow block around the lable) and pretty effective, providing of course you keep your lables up to date...

No sirens or whistles, it just draws the ATCO's attention to it, we can then assess and react accordingly.

[Weary]

A late thanks chaps, for all the replies, but thanks nonetheless!