Hi,

Re. Zaon MRX.

On the 23/2/08 and again on 26/2/08 the MRX displayed traffic at various ranges and altitudes that did not exist, the unit never displayed a "NEW" display at any stage. The nearest ground based radar is over 300nm away although there is a doppler wx radar station within 40nm. The area is under an airway route so TCAS interorgation is possible but flights on this route are typically at not less than 30 minute intervals.



The false display lasted for 2 of the 3 hours of the airwork sortie. On other flights prior, in between, and today the unit has been totally silent.

How is this possible?

If this is not possible what would be the expected time _frame_ for a warranty claim ex Australia?(unit purchased through a local dealer).

Also during start up the unit will display "GHT MODE" what is this mode? If it represents ground mode should it not read GND MODE as per ICAO designator or does GHT actually stand for something different.

Also I can't seem to access all the threads and responses on your web forum. Is there a problem or am I missing something?

Regards
Mick

Sorry I should also add, transponder on or off made no difference.

Regards
Mick

Mick:

Thank you for your inquiry. The most puzzling thing to me is how to know that the traffic didn't exist. In order for an MRX or XRX to display traffic, the incoming signal must have a valid altitude code (Mode C) that can be decoded, and several hits must be attained in this manner. To my knowledge, the only device that can create a valid altitude code is another transponder. I believe when you talked with Daniel, that there was another aircraft in the area with TCAS that was also reporting traffic, but nobody could figure out where this was coming from. Is this true?

There are a few things I'd like to find out: what range and altitude was MRX reporting when it was displaying traffic? Did it change over time?

The "GHT" mode is the last part of the scrolling message. When you turn the unit on, it scrolls "PRESS UP FOR FLIGHT MODE" after the version number and battery level. If you press up, the unit will watch for traffic both above and below. If you don't it assumes you're on the ground (as indicated by the "G" on the traffic page) until you've climbed 200 feet, then it switches to flight mode.

You should have access to all threads on the forum. I've looked but can't find any that are broken. Is there a specific thread I can check for you?

I have heard of stationary beacons, possibly for the purpose of repeating ATC information, in remote areas that may also cause this effect. I am contacting the CAA to explore this. It would be very helpful if you could identify the area you were flying where you were getting the alerts in question.

I can see there is no traffic, this should not be puzzling, particularly if you have flown at less than 500' AGL over flat featureless terrain. With 23 years and 10,000 hours of low level flight I think I can be considered a sound judge on this one. Visibility over 50nm.

Location north and east of Ceduna South Australia, 0 to 50nm radius.

Returns cover all ranges from 0.8 to 5.0nm and target appears at or around ground level regardless of our altitude, which is typicaly 400' AGL. The false return lasts for 80% of the 3 hour flight. During the 50 hours conducted over the last 4 weeks the MRX has yet to display our transponder code when the transponder is on which is about 20% of the time. Nearest ATC radar 300nm.

I heard an inbound SAAB 340 trying to make contact with mystery (no radio transmissions) low level traffic 10nm east of Ceduna when questioned he thought it might be a false return. Other crews haven't experienced this.

Local wx radar 6 Ghz

ADS-B receive only and on edge of its range.

Accessibility of the forum:

PCAS MRX shows 20 topics and 12 responses, I can only find 15 topics and 6 responses.
Question posted by pylet has no response shown but is over a month old.

Regards
Mick

Since posting the previous comments on false indications I am now able to add new information on the matter.

Having completed our aerial work operations in the area where I was receiving near continual false alerts, we have now shifted to the top of central Australia.

On departure from Alice Springs climbing through 4000' (2000' AGL) in central Australia and a non radar environment I received an indication for several minutes of traffic 2nm and according to the MRX flying at 2000' BELOW ground level. Does this indicate a fault?

Whilst enroute at 9000' between Tennant Creek and Borroloola in the Northern Territory, the MRX displayed in response to TCAS I pressume, my squawk code of 2000 as 0200. Is this normal or an indication of a fault?

On arrival at Borroloola and on the ground the MRX displayed an Alert display of traffic in very close proximity and flying at ground level. TCAS may be prevelant in the area but ATC radar 400 nm away. Is this normal or indication of a fault?

Could you please respond to these questions so I know whether my unit is faulty and should be returned, or they are normal design limitations of the MRX.

Regards
Mick