Commercial Flights crossing paths - Waaaaay to close for comfort

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WBI Flyer

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so... I was on a flight today - and at one point during the flight, I opened my shade to look out. It had been a gorgeous sunset at FL39, and city lights were coming into view when the clouds broke.

The pilot was making some talk about initial approach on the intercom, when I saw a plane fly directly underneath us. It came from our 11 0'clock and literally passed right underneath us. It was close. As it passed underneath us, the pilot stopped his announcement - paused for just a second, and then resumed. If you hadn't seen the plane, you would not have thought anything of it.

I can find my flight on flight aware, but I have no info for the other flight. Is there a way to see a historical map "timestamp" of ADS-B? ie. Can I look at a map over Florence, and set it to a certain time and see all of the ADS-B transmitters that were in the area at that time?
 
Let'sgoflying! said:
1000', that's not even a quarter mile.
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And it happens every day! Oh the humanity!

Minor inflight entertainment on a Denver to Dallas flight is to try to spot the opposite direction traffic. It goes by quick.
 
Reduced Vertical Separation Minimum (RVSM) is defined as the reduction of vertical space between aircraft from 2,000 to 1,000 feet at flight levels from 29,000 feet up to 41,000 feet. RVSM was implemented as a means to increase airspace capacity and access to more fuel-efficient flight levels.
 
WBI Flyer said:
It wasn't 1000'. Definitely no more than 500'.
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I've seen that twice. They look very close, i'd a said less than 1000. Neither was something real big, like a 747, which would probably make it look even closer. Neither time did I feel anything that felt like the pilot was responding to a TCAS Resolution Advisory. They could have been less than 1000 and still ok, not by a lot though. I don't know what the 'tolerance' is on the altitude computers but it's +/- something. Back in the days when separation above FL290 was 2000 and done with barometric altimeters only, the goal wasn't keeping airplanes 2000 feet apart. It was assigning altitudes 2000 feet apart to ensure that actual separation was not to much less than 1000.
 
WBI Flyer said:
It wasn't 1000'. Definitely no more than 500'.
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This highlights one of the big reasons autopilots are required to be used in RVSM airspace.

One of the things you learn when doing the RVSM training is that at those altitudes, pilots are terrible at judging separation distance and a pilot taking action based on visual perception could actually cause a collision hence an AP is required to be operational and used. No hand flying in RVSM.


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Like others have said, 1000' feet sep feels like a lot less. Break in transmission could easily have been ATC comms, as controllers will still normally provide traffic advisory calls, even if altitude separation exists. I don't know the reason why, but at higher altitudes, it often seems like less. Maybe its the contrails.......
 
Guaranteed it was 1000' normal separation done all day long, it always looks closer than it really is.
You can relax now and go back to your peanuts.
 
Big airplanes look closer than they are. I'm betting on 1000.

I got close enough to an MD-80 in the Navion one time to cause a TCAS RA. Still weren't close enough to have caused a collision (I had him in sight even if the MD-80 pilot and C90 didn't).
 
WBI Flyer said:
It had been a gorgeous sunset at FL39
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FL390. FL39 is 3,900'.

The pilot was making some talk about initial approach on the intercom, when I saw a plane fly directly underneath us. It came from our 11 0'clock and literally passed right underneath us. It was close.
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If it were any less than the standard 1000' vertical separation you would have heard the TCAS TA ("TRAFFIC, TRAFFIC"), then RA ("MAINTAIN VERTICAL SPEED"), during the pilot's announcement.

At 500', but less than 1000', the TCAS RA won't have you climb/descend if both airplanes are level, but it will give an RA which will prohibit climbing/descending toward the other airplane.
 
Happens all the time, you just happened to look out the window at the right time. Hence why ATC takes altitude deviations while under IFR so seriously. If someone isn’t exactly where they’re supposed to be bad stuff can happen.
 
WBI Flyer said:
It wasn't 1000'. Definitely no more than 500'.
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FAR 91 Appendix G covers RVSM. By the tolerances there, planes could be closer to 500 than 1000. Looks like about 740 feet could be in tolerance depending on when the aircraft were RVSM certified. Odds of two aircraft 'merging,' the low one + the tolerance and the high one - the tolerance are pretty slim. Reading on things get more involved with ASE. It's possible, not probable, but possible that planes could get pretty close to 500 feet.
 
Fearless Tower said:
This highlights one of the big reasons autopilots are required to be used in RVSM airspace.

One of the things you learn when doing the RVSM training is that at those altitudes, pilots are terrible at judging separation distance and a pilot taking action based on visual perception could actually cause a collision hence an AP is required to be operational and used. No hand flying in RVSM.


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Are redundant auto pilots required?
 
Keep an eye out next time you’re on the FMS Bridge Visual 28R at SFO, with the plane lined up on 28L, you’ll think your back in the military flying form.

I realize you mentioned at altitude, especially up in the flight levels, I’m going with 1000’ split. The PA pause may of been just to let the TCAS audible run their course.
 
The break in the announcement could have been a lot of things. Probably listening to something from ATC like “descend and maintain” or “expect visual approach.” Big planes definitely look closer than they are. The A380 traffic between California and Europe often goes over my house, somewhere in the vicinity of FL330. That’s about 6 miles AGL. They look like they’re at 8,000 MSL but that’s just because they’re so big.
 
MauleSkinner said:
No...but if the autopilot is inop, you have to tell ATC that you're not RVSM capable anymore.
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Yes but I believe ATC can waiver it only for that flight, or the remainder of it in RVSM airspace if I recall correctly. Maybe not.
 
Technically, an autopilot is not required just an "automatic altitude control system" so only altitude hold.

While ATC can approve continued operation in RVSM airspace with inoperative required equipment, my understanding is that their rules do not allow it.
 
You can also be cleared into RVSM airspace in a non-RVSM aircraft, though they won't apply RVSM vertical sep. Happens all the time out west when things aren't busy. Apples and oranges comparison, but the point being that "RVSM airspace" isn't always being used as such.
 
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