"Ghost Targets" on TCAS!?
Thread Starter
Joined: Apr 2007
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From: Germany
"Ghost Targets" on TCAS!?
My event last Thursday: Maintaining 3000', 200 KIAS on a radar vector for a PAR Approach into Wittmund Airbase (ETNT), 10 NM South of the airfield on downwind leg.
Suddenly one Target popped up on TCAS display in my seven o' clock position, 1200' lower than me. TRAFFIC-TRAFFIC was announced. The one target thereafter split into two, then into four targets, CLIMB-CLIMB was issued. Reaching 4000' in the TCAS climb gave CLEAR OF CONFLICT and targets were gone. Never had visual contact to anybody.
Asking ATC what was going on, they said, they had no traffic that close, only two VFR targets, but far enough away.
Later on the ground I talked to a guy who regulary flies out of Wittmund. He said that they built a large wind-power-plant park south of the airfield and that this park already had distracted GCA and airborne radars.
I never heard of distracted TCAS-computers. Did anybody else hear anything similar to that?
Thanks for your inputs!!
Suddenly one Target popped up on TCAS display in my seven o' clock position, 1200' lower than me. TRAFFIC-TRAFFIC was announced. The one target thereafter split into two, then into four targets, CLIMB-CLIMB was issued. Reaching 4000' in the TCAS climb gave CLEAR OF CONFLICT and targets were gone. Never had visual contact to anybody.
Asking ATC what was going on, they said, they had no traffic that close, only two VFR targets, but far enough away.
Later on the ground I talked to a guy who regulary flies out of Wittmund. He said that they built a large wind-power-plant park south of the airfield and that this park already had distracted GCA and airborne radars.
I never heard of distracted TCAS-computers. Did anybody else hear anything similar to that?
Thanks for your inputs!!
Joined: Sep 2002
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From: La Belle Province
Can't conceive how a wind turbine could confuse TCAS, especially if you were getting altitude signals. As I understand it, TCAS derives altitude data cooperatively, from the target's transponder. It's not a radar in the traditional, military sense. So you shouldn't be getting false returns off the turbine blades (or anything else, for that matter).
The only thing that even vaguely works is that the blades are somehow reflecting valid TCAS responses from other traffic, so that you get a valid altitude but an invalid direction. Sounds a bit unlikely though.
The only thing that even vaguely works is that the blades are somehow reflecting valid TCAS responses from other traffic, so that you get a valid altitude but an invalid direction. Sounds a bit unlikely though.
Thread Starter
Joined: Apr 2007
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From: Germany
Yes, you are right about the TCAS technique. It uses only mode S data and not any primary radar.
The only explanation I have so far is the same as you have, that signals were somehow reflected by the rotating blades of the wind power plants. But I never heard about it.
The military guys said to me, that the power plant had already masked a light-type completely, so maybe there could also be some disturbences with the TCAS signals, but I don't know.
The only explanation I have so far is the same as you have, that signals were somehow reflected by the rotating blades of the wind power plants. But I never heard about it.
The military guys said to me, that the power plant had already masked a light-type completely, so maybe there could also be some disturbences with the TCAS signals, but I don't know.
Joined: Dec 2006
Aviation Qualifications: CPL
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From: Hamburg
Recently a taxiing Lufthansa crew reported a TCAS target at the position of the follow-me car in Hamburg. They asked if the car was equipped with XPDR. The tower controller even checked via phone but then reported it was not.
Joined: May 2004
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From: UK
Had a mysterious TCAS return on departure from BCN the other night, indicating 2000 below us and climbing. The return then made several rapid movements from left to right and then sodded off south bound. ATC reported no traffic below us.
I'm telling ya - they are out there..........
(and they clearly have mode S)
I'm telling ya - they are out there..........
(and they clearly have mode S)
Fleet Manager
Joined: Apr 2001
Aviation Qualifications: ATPL
Posts: 7,448
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From: various places .....
If the bandit is showing more or less stationary above a maintenance outfit, it is entirely likely that the boys are running some checks on the ground and putting out spurious height data ... common and well known problem in Oz.
Joined: Mar 2000
Aviation Qualifications: ATP+Mil
Posts: 1,428
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From: Long ago and far away ......
When the RAF VC10s were fitted with TCAS I seem to recall one of them giving RAs against itself! A problem with the wiring looms or something ..... they are rather old.
Joined: Jun 2001
Posts: 4,777
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From: Blighty
Quote: Recently a taxiing Lufthansa crew reported a TCAS target at the position of the follow-me car in Hamburg. They asked if the car was equipped with XPDR. The tower controller even checked via phone but then reported it was not.
Some airports use a new Airfield Surface Movement Indicator system that uses Mode S rather than primary radar. Some vehicles at these airports have a special Mode S transponder fitted to keep the system updated. So the answer could be yes.
Ghost returns are common from some missile systems. Pilots flying up the East coast of China may be familiar with a TCAS diamond with no height readout just to the East if Xiamen. This is a Patriot missile battery which Taiwan has positioned on Kinmen Island. The Patriot system has an IFF interrogater which some systems display as a No Mode Charlie TCAS contact, whic is why the Chinese won't let you do a weather deviation to the East on thay airway.
Some airports use a new Airfield Surface Movement Indicator system that uses Mode S rather than primary radar. Some vehicles at these airports have a special Mode S transponder fitted to keep the system updated. So the answer could be yes.
Ghost returns are common from some missile systems. Pilots flying up the East coast of China may be familiar with a TCAS diamond with no height readout just to the East if Xiamen. This is a Patriot missile battery which Taiwan has positioned on Kinmen Island. The Patriot system has an IFF interrogater which some systems display as a No Mode Charlie TCAS contact, whic is why the Chinese won't let you do a weather deviation to the East on thay airway.
