One for the ATC chaps amongst us

leaskovski · 6 May 2014 at 13:04

So as I was unpacking the motor last night (about 7.30pm) I saw two passenger jets fly above. One heading the usual approach way to land at Heathrow, and the other going completely against it.

I thought they were a little close to each other... I would guess within a mile of each other (probably not though). It made me wonder, what is classed as a near miss or defines how close planes should get to each other in the air?

Ive had a look on Flightradar24 but can't see the other plane going to other way. Any ATC guys on here that can look it up to see if there was a 'risk'? The area in question is just south of Wokingham.

Tuppy_Glossop · 6 May 2014 at 13:08

It is hard to really say how far apart they are when observing from below. They have vertical and horizontal separation, either of which can be hard to estimate (depending on your relative position).

Given it is in the UK they will have had TCAS II running which, if both crews obey the TCAS instructions, will prevent them crashing into each other.

It also depends on how you define 'risk'.

Stringy · 6 May 2014 at 13:09

Probably a trick of perspective, one plane likely bigger than the other with 1000ft or more separating them, making it look to you like they were far closer to eachother than you thought.

For example, a small 737 1000ft underneath an A380 will probably look similar in size, and make them seem closer to being co-level.

And I can tell you that normally aircraft will need 1000ft vertical separation and then lateral separation varies depending on the wake turbulence that they cause (generally dependent on size) but I'm sure a proper ATC geek will be able to reel off the specifics depending on classes of airspace and the like.

leaskovski · 6 May 2014 at 13:12

Should I be able to spot them both on Flightradar though?

Stringy · 6 May 2014 at 13:15

leaskovski said:
Should I be able to spot them both on Flightradar though?

Not necessarily, do some reading into how Flightradar works, it's not a 100% infallible system with every aircraft on it 100% of the time.

Malt_Vinegar · 6 May 2014 at 16:24

There are always aircraft that do not have the correct transponder type, so will not show on the system.
There is a twin engined mid-sized passenger type jet that is always flying low around Guildford and the surrounding area, and I can never find it on any flightradar.

I would love to know if someone could shed any light on what it is doing, it's up most days and I spot it a number of times in a day in the same rough area.