Purpose of activating a Parallel Track?

kicktireslightfires

kicktireslightfires

Pre-takeoff checklist
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kicktireslightfires
When would one want to “activate a Parallel Track” in a flight plan? Every IR pilot I've asked says they've never used that and they have no idea.
 
Sight seeing
 
kicktireslightfires said:
When would one want to “activate a Parallel Track” in a flight plan? Every IR pilot I've asked says they've never used that and they have no idea.
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I haven’t done it yet, but my best guess is this: while flying VFR in a route over VORs and major waypoints, it keeps you away from other traffic that might be going exactly over those points.

In the days before WAAS GPS, that was unnecessary. Navigation by radio aids isn’t precise within a quarter mile, so traffic was not converging within 40’ of a VOR as it can today.
 
Offsets are used routinely in oceanic airspace. Strategic Lateral Offset Procedure (SLOP) is used in most oceanic airspace without ATC clearance or notification. Flight randomly pick a 0NM, 1NM, or 2NM right offset. When weather deviations are necessary, flights will obtain clearances to deviate up to XXNM right or left of course. The ability to enter that offset into the FMS allows you to draw the boundary of your offset limit as you pick through the weather.

I got a domestic offset clearance last week when we needed to deviate for weather along our route but ATC had to protect military airspace.

Offset clearances were common in Afghanistan ~10 years ago (USAF controlled the airspace) to route traffic around areas of military operation. We'd receive an offset of XXNM from ABCDE fix to VWXYZ fix along our cleared airway. We'd often see a swarm of TCAS targets, we assumed mostly drones, in the area that we were offsetting around.
 
Htaylor said:
https://skybrary.aero/articles/parallel-offset
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That was the most helpful. Thank you!

  • Weather avoidance. Pilots may sometimes request to avoid convective clouds (CBs) by flying a parallel offset instead of a heading change. The magnitude of the deviation may be much greater than what is normally expected in the separation or wake turbulence scenarios and may often be more than 10 or 15 nautical miles.
Phraseology
ICAO Doc 4444 PANS-ATM Chapter 12 defines the following phraseology to be used in parallel offset operations:
  • ADVISE IF ABLE TO PROCEED PARALLEL OFFSET - used by the controller to determine whether such a manoeuvre is feasible.
  • PROCEED OFFSET (distance) RIGHT/LEFT OF (route) (track) [CENTRE LINE] [AT (significant point or time)] [UNTIL (significant point or time)] - the instruction format for starting a parallel offset.
    • Example: PRE0405 proceed offset 5 miles left of track until abeam SNA VOR
  • CANCEL OFFSET (instructions to rejoin cleared flight route or other information)
    • Example: PRE0405 cancel offset, proceed direct to SNA VOR
  • REQUEST OFFSET (distance) RIGHT/LEFT OF (route) (track) [CENTRE LINE] [DUE TO WAKE TURBULENCE/TO AVOID WEATHER] - a pilot request to perform a parallel offset. Note that while this is commonly used format it is not a part of the ICAO Standard Phraseology and therefore variations do exist.
    • Example: PRE0405 request 2 miles left of track due to wake turbulence
 
Years ago, we used regularly it to let a faster airplane pass us or to pass a slower one. I have not used it in years, ATC seems to prefer vectors or altitude changes now.
 
Plano Pilot said:
Years ago, we used regularly it to let a faster airplane pass us or to pass a slower one. I have not used it in years, ATC seems to prefer vectors or altitude changes now.
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I had a friend that flew Phenom 100s and actually was requested to use an offset often, because the Phenom was too slow to make minimum speeds on some STARS, but ATC still wanted him on the arrival.

I've been offset flying GA aircraft into Class B airports before, to let the airliners continue to pass until closer to the runway. Really backs things up when best speed on the approach is 120 kts versus 140-160 of the big guys.
 
Besides oceanic airspace, it’s useful in the FLs if you’re flying right underneath another plane’s wake. You can request an offset to the left or right to get a smoother ride.
 
kicktireslightfires said:
When would one want to “activate a Parallel Track” in a flight plan? Every IR pilot I've asked says they've never used that and they have no idea.
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I did from Cozumel to Guatemala City as the airway stays off the coast for a while and I wanted to be over land. I think I asked for 4 miles west on a parallel track.
 
kicktireslightfires said:
When would one want to “activate a Parallel Track” in a flight plan? Every IR pilot I've asked says they've never used that and they have no idea.
Click to expand...
Another reason for using the parallel track is when say two or more aircraft are departing the same airport to another airport. Say going for a $100 hamburger run, or a pancake breakfast fly-in. Rather than all aircraft fly direct, some can use a parallel offset by 1 or 2 miles left or right of the direct route. That way the chances of a collision are minimized.
 
My brief time in CAP they used the offset to help in search and rescue or aerial photography as two examples.
 
I know in China they don’t like you asking to deviate X degrees L/R for weather. Instead they want you to offset X number of miles.
 
jordane93 said:
Besides oceanic airspace, it’s useful in the FLs if you’re flying right underneath another plane’s wake. You can request an offset to the left or right to get a smoother ride.
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This here. Ive had aircraft request a parallel offset to get out of a preceding aircraft's wake
 
SLOP

Strategic Laterial Offset Program

basically you fly 1 or 2 miles right of course so as to not hit an oncomming aircraft on an airway as modern avionics are dead on accurate. Old days the odds of actually hitting were minuscule. Today if there's an error and you're on the track you'll likely hit. SLOP is only done in non-radar and only after notifying ATC you're doing it.
 
Oh, and i've used laterial offset to get around weather, although that's pretty rare. But if you just need like 10 miles or so to clear weather then an offset can get the job done. Typically you fly a heading and then some fix down the road when able, but an offset can accomplish the same thing.

YMMV
 
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