Seriph,
Nope I'm not snctimonious (see can't even spell it) or self righteous, I don't know if anything I have said helps but I hope it does. I do know of a lot of sanctimonious arrogant 'professional' pilots that go around with there head up their own a***s rather than try to learn from others. They spend their whole days bitching about problems without ever trying to make anything better.
I have learn't a lot from the contributions of other people on these forums and if just one snippet prevents anything like this from happening in the future, I for one will be greatful.
What would you have done put the blinds up and prayed to the big sky principle. Sounds like the sort of preaching that went on in the dark ages.
Holy s**t, I just bit..... oh well feel better now,
Ghost
Mr DA,
The closure issue is interesting but effectively all that happens is the exact collision point moves. I once tried intercepting a Sea King doing 80 kts IAS with a ground speed of about 20, it was a a horrible nightmare only to be discussed in the bar. Against slow speed targets, any avoiding action by you ensures a wider miss distance.
Putting the boot on the other foot, lets say you are in a turbo prop and configured whilst trying to avoid a fast jet that is not on your centreline but still on a collision. A turn towards the intruder that points your nose behind him uses his speed and geometry to create the miss. You have to turn more than he would to get the same miss distance because most of the closure rate is being generated by his platform. However, if you both turn it can get mighty confusing hence the right hand traffic rule. The key is to do it early and decisively so everyone knows what is happening and more importantly share your information with the controllers.
As to turning to avoid a collision to provide a 'belts and braces' miss once all else has failed; it depends on when you do it. If you have TCAS or visual SA of the approaching threat and can clearly see how to avoid him then taking that action early, even before a TA cannot be a bad thing. If he is stationary in the windscreen and the TCAS shows him at your altitude even a slight turn at range helps immeasurably.
Getting to worst case scenarios, even a 10° turn that generates a line of sight rate will produce an acceptable miss distance if actioned when you get the TA. On a head to head at the TA (40 secs to impact) assuming both aircraft at 0.8 mach you have 16 miles per minute of closure.
So if you actioned the turn at the TA and had it completed with 30 secs to go ( 8 nm) you would miss the other aircraft by about 4,000 feet laterally using the 1 in 10 rule.
If you wait to start a turn until you get an RA at about 25 secs and again took 10 secs to recognise and complete the turn you you would get a miss of around 2,000 feet laterally but at some cost of vertical performance.
Warning To do something this late, you have to be certain that you are carrying out the right action. For that to be the case you must have sound SA.
If you really do have the SA though, do something early! Don't wait for an RA to make your move. Avoid the TCAS conflict completely if you can by firstly talking to ATC and secondly maneuvring. By the time you have got to an RA you are in an emergency situation and want to have the entire kinematic performance of the aircraft available to you in the vertical plane.
My companies SOPs say try to acquire the aircraft visually if you get a TA but do not attempt to maneuvre based on a TA alone.
Well if I got the TA, spotted the traffic, assessed the geometry as a collision that would result in a subsequent RA and could turn to avoid it, I would. (But you don't have much time and again you have to be sure and decisive.)
However once I got to the RA, I would follow the TCAS commands religiously in case of coordinated avoidance. Some trainers will say take the time to disconnect the AP and turn off the FDs in the time between the TA and RA, boll**ks get your head out and try to sort the problem out.
Quality decisions are normally made in good time, the TCAS conflict scenario is something that can be avoided by timely avoiding action at range. Like most of us I listen to traffic climbing and descending and try to tie it into TCAS returns around my aircraft. If we do have the SA it is essential we give that to the men who can fix it in good time - ATC.
If used correctly with the display range and altitude coverage set correctly and if we regularly scan it there shouldn't be too many surprises. Almost always the intruder will have been in the TCAS display system for some time before generating a TA. In the future I know that I will be taking as much interest in the TCAS approaching waypoints as I do now when I get into terminal airspace.
Ghost
