TAs from helicopters on LHR Approach
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TAs from helicopters on LHR Approach
I frequently get TCAS TAs on the approach to LHR from Helis operating down the Thames. Is there any reason why they only squawk mode A? If they squawked mode C then TCAS would ignore them, and save a big distraction at a critical phase of the flight.
Whose control are they under, and is mode A only a regulation?
Whose control are they under, and is mode A only a regulation?
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Often being responsible for provison of services along parts of H10, H5, H2 and H9 I would echo HD's comments; certainly the majority use Mode C.
What are the criteria for the issue of a TCAS TA? I ask this because I am not wholly sure of the tolerances and capabilities of TCAS.
What are the criteria for the issue of a TCAS TA? I ask this because I am not wholly sure of the tolerances and capabilities of TCAS.
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WP SATCO - If you fly near an aircraft with only mode 'A' active, because the aircraft detects the posibility of a collision it will give an TA. It will never give an RA in this circumstance. Turn on mode 'C', the TCAS computer will see that the vertical separation is OK - no warning.
Edit to say - TA when the aircraft is 40 seconds from point of closest approach, RA at 25 seconds.
Edit to say - TA when the aircraft is 40 seconds from point of closest approach, RA at 25 seconds.
Last edited by Cough; 30th Aug 2002 at 22:30.
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Most of the commercial helicopters do squawk mode C in the London Control Zone. I would suspect that some of the private helicopters only have mode A, however I am aware of a reluctance by private pilots, (both fixed and rotary wing), to squawk mode C for some strange reason. Perhaps it is because their altitude compliance is not very accurate and they don't want ATC to notice!
There is actually no legal requirement to carry a transponder in order to fly in the London Control Zone.
There is actually no legal requirement to carry a transponder in order to fly in the London Control Zone.
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Everbody is right from my experience - you do get a lot of TA's from choppers but they are normally squalking alts, its the other end with white waltham that has ta's with no alts...
Is a pain though, stops you watching the action at Twickers when on shortish final
Is a pain though, stops you watching the action at Twickers when on shortish final
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That's nothing - try SFB - on final to 09L in a Big Bus, ATC advise of helicopter traffic to the right of approach and below. We get to 2 mile final and the Sheriff's helicopter is off our right wingtip, less than a mile away at our level :o
We guessed he had a gun, so we didn't say too much !
We guessed he had a gun, so we didn't say too much !
