gophish11

As I understand it (correct me if I'm wrong), "standard" radar spacing for aircraft en route is approximately 2 miles laterally, 5 miles behind and 1,000 ft. vertically. Does anyone know if there are international standards for this, and whether it applies during VFR flight?

The reason I ask is that I had the sighting of a lifetime just moments ago aboard QR719 over Iran en-route from DOH-SEA. A Mahan Air A340-600 operating as W563 from IKA-DXB passed in the other direction, with the aircraft for a split second occupying nearly the entire width of my window view from 10A. I am in a rear-facing seat so maintained visual for probably just under 1 second.

Our 777-300 was maintaining exactly 30,000 ft. at a heading of approximately 350, and the 340 was still climbing out of Tehran, passing just below us to the port side. We were absolutely less than a half mile laterally, and aircraft had climbed through our altitude and up to 32,000 by the time I located it on flightradar24 at a heading of 175. I'm guessing it crossed through our cruise at 30k within 5 seconds. Yes, the 340 is a very large aircraft and distances can be difficult to gauge, but I'd give the distance about "5 gates' worth" if parked at most terminals. I'd give the distance at around 1,500 feet laterally and maybe 800 below us. As our headings (in the opposite direction) were not quite parallel, and since W563 was still climbing, it seems this left an incredibly slim window for evasive maneuvering. A little more lift for the A340 or 2-3 degrees to the left for our 777 would have seen us uncomfortably close.

I know folks post about "near misses" all the time, and I'm absolutely not calling this a near miss, because it wasn't. However, in the roughly 1.5M miles I've flown, this pass was incomparably closer than I've ever seen at cruise, which is why I ask about spacing standards out of my own curiosity.

Interestingly, this particular aircraft (EP-MMQ) was the one that Iran abruptly diverted to Kish last December, so Tehran could prevent the wife and daughter of Iranian footballer Ali Daei from leaving the country, due to his support for anti-government rallies.

LarryJ

It depends on the airspace; the ATC capabilities, and the minimum aircraft requirements of that airspace.

In a RADAR environment, it is typically 1,000' vertical and either 3nm or 5nm horizontal.

It is very difficult to judge the distance to another aircraft visually. I based that on several decades of watching aircraft fly by and comparing what I see visually to the distance shows on our TCAS display.

RandomNobody

Here's what 1000 feet on the same track looks like:


2000 Feet for the same-direction traffic above, 1000 feet for the opposite direction split-down-the-middle aircraft. It "looks" a lot closer than it really is.

Edit: And it's 1000 feet in "Flight Level" altimeter (29.92 inches of mercury at ISA). It could be more, it could be less. It depends on the local isobar and temperature.

LarryJ

That video clip also shows how accurate GPS is. All three airplanes were centered exactly on the track. In the pre-GPS days, there would have been lateral separation due to the lack of precision in the navigation sources.

RandomNobody

Which is why SLOP is a thing.

Palal

Look at around 06:36 UTC (assuming I got the date right)
https://www.flightradar24.com/data/f...qr719#30b93dff
https://www.flightradar24.com/data/f.../w563#30b960ad

LarryJ

Strategic Lateral Offset Procedure.

In oceanic (Class II) airspace, pilots randomly choose and offset 0.0 to 2.0nm to the right of course.

gophish11

It was actually the day after (June 16). While it's difficult to pinpoint the exact second we passed, it was between 6:55 and 6:56 (I'd guess about 6:55:45) UTC. The data for W563 shows they were slowly climbing through 29,100 at the time, and we were level at 30,000. Using Google Maps, it appears we were laterally separated by around 2,900 ft. laterally in nearly parallel (but opposite) headings. So I was about right on estimating our vertical separation but we were nearly twice as far horizontally than I'd estimated.

Still, this does verify that we were indeed less than 1,000 ft. vertical and significantly less than 1nm laterally separated. So definitely less than "conventional" radar separation and less than you'd want during IFR, but it was during VFR flight in perfectly stable air, so probably acceptable given the conditions. Absolutely a close pass and outstanding (although very brief) sighting of a Mahan Air A340 in flight. Very cool.

RandomNobody

You're conflating flight rules Instrument/Visual Flight Rules with flight conditions Instrument/Visual Meteorological Conditions. Flight rules....are the the rules you fly by. Who controls you, what procedures you fly, what ATC is responsible for, etc. Meteorological Conditions are whether you can stay upright and navigate just by looking out the window (to oversimplify).

Scheduled airline flights are pretty much IFR all the time. You can fly IFR in VMC, and you can legally fly VFR in IMC (think "moonless night over the desert").

LarryJ

FL300 and FL291 is not a loss of separation, particularly when you're looking at data from a 3rd party. There is some allowable error in altitude reporting and even the (required) autopilot altitude hold is not perfect. Even if they are indicating FL300 and FL291 on the controller's scope, that meets separation requirements.

DSM Flyer

One morning a few years ago I was flying westbound at cruising altitude on either an A319 or A320 when we banked fairly sharply to the left. Not quite alarmingly but more sharply than a normal maneuver at cruising altitude, and enough to make me glance out my window to the right. Below and to the right a CRJ went screaming past eastbound, close enough that I could read American Eagle and the tail number. I wish I had made a note of the tail number so I could've gone back and looked it up.