Why is the flight path from Taipei to Tianjin not a straight line?

Question

The flight path from Taipei, Taiwan, to Tianjin, China, does not go directly to Tianjin in a straight line.

Instead, it heads directly north, then banks left (west) before heading north again.

(Actual flight CCA188, source: FlightAware)

Possible route: PIANO L3 VIOLA R596 OKATO W13 PINOT B221 OKTUG W506 HGH W554 DOGVI A470 PIX A593 VYK VYK9A/16R (used by virtual crews on simulation networks, source: VATAware.)

Does anyone know why this is?

Possible duplicate of Why do pilots use airways instead of just "flying direct" every time? — Simon, Nov 03 '15 at 06:59
@Simon In this case it's a bit more specific for a given route, same as with the Germanwings route. — SentryRaven, Nov 03 '15 at 07:04
@mins The routing via PIANO would most likely not take that turn. This is probably the DRAKE routing to SULEM. Also: vataware for routes? I wouldn't use them as a source, I know how these routes are created by some pilots :D — SentryRaven, Nov 03 '15 at 07:09
I posted the same question in Travel and got the following explanation:
http://travel.stackexchange.com/questions/58217/why-is-the-flight-path-from-taipei-to-tianjin-not-a-straight-line

Basically, the Chinese government operates very narrow airways that commercial flights have to use. Also, thanks for adding in the picture of the route whoever did that. — thatsagoal, Nov 03 '15 at 07:12
@mins I take that back. I didn't notice that VIOLA intersects with both departure routings, DRAKE and PIANO. — SentryRaven, Nov 03 '15 at 07:12
@SentryRaven: Thanks anyway. What would you use to find an actual route in this area? — mins, Nov 03 '15 at 07:22
@mins Not really many options. But the simulations folks sometimes use auto-generated routes that are not valid, so vataware is not a #1 source on my list unless I can pass that route from there through CFMU for Europe, e.g.. — SentryRaven, Nov 03 '15 at 07:23
@thatsagoal: Welcome to Aviation.SE. When your post is edited, and you are not satisfied with the update, then you can revert to the previous versions using the button edited .... See Help Center for full description. Hope to see many questions and answers from you! — mins, Nov 03 '15 at 07:30

score 6 · Accepted Answer · answered Nov 03 '15 at 07:02

This will be due to routing and the airways available. Looking at the Enroute Chart for the Taipei FIR, you will notice that there is no direct route northbound, but all routes have a north-east direction to remain clear of restricted area RCR8 (GND - FL370).

^{(Source: http://eaip.caa.gov.tw)}

The flight most likely, as I cannot find the flightplan, departed RCTP - Taipei via the DRAKE1A or DRAKE1B SID, leading to SULEM. Thereafter it continued westbound on the respective airways within China to then join another airway north.

This is consistent with the flightprofile tracked on flightware for EVA730 from RCTP to ZBTJ.

^{(Source: www.flightaware.com)}

Why is the flight path from Taipei to Tianjin not a straight line?

1 Answers1