For several weeks now (perhaps a few months?), the routing provided by simBrief for alternate airports has been bothering me.
When you select multiple alternates, it seems the route to all alternates is based on the route to the primary/actual alternate (even when the other alternates are in a different direction from the destination, which is where it’s most problematic).
For example, KSEA to CYYZ with 4 altermates (excluding CYTR) moments ago:
Looking at the route overhead, surely this cannot be on purpose?
I’m also curious about why the alternate routings seem to include a SID when available; real-world OFP examples found at e.g. Downloads - PilotsEYE.tvPilotsEYE.tv never seem to have them.
It also seems counter-intuitive to me: even if one decides to divert to an alternate after an aborted landing at the destination, the applicable procedure would be a missed approach rather than a SID, not to mention, the formal decision to divert would likely occur after said missed approach is completed anyway, rather than before/during? If the aircraft is, say, in a published hold for a missed approach procedure when they get cleared for the diversion, surely the chances that ATC would then place them on a SID are almost zero?
Problem is ATC facilities rarely if ever provide a routing to an alternate in a preferred IFR routes list, so lacking that, what do you do? Here in the lower 48 in the US, DCT works probably 95% of the time, but it’s based on the operator’s fuel rules imposed by their regulator.
Depending on the fuel rules in use, for example US OpSpecs B343, it states that a “realistic routing must be used” from the destination to the destination alternate, so great circle direct isnt going to work. So, if I were going to PHNL and use the crosstown alternate of PHJR under B343, a realistic routing might be PHNL DCT CKH DCT SIMSN DCT PHJR. If going into KORD and using KMKE, a realistic routing might be DCT OBK DCT, just to make a regulator happy.
EASA requires a routing in the OFP from the destination to the alternate, even for US airlines operating to or within the EU as we hold what is called a European Third Country Authorization. At my airline, if we are using a crosstown alternate (EGKK for EGSS for example), we have a route built in FPS that makes the SAFA ramp inspectors happy. If I am using EDDF for LFPG, we’ll use whatever is passing muster for IFPS that day.
I agree, but the purpose is to make a regulator happy. I also get it from a crew perspective, to give them a more accurate fuel value instead of great circle direct when using LIMC for LFPG.
I’m sorry, how does that address the issue? Have you looked at the routes from CYYZ to CYYB, CYHM and KBUF on a map, and still come to the conclusion that they correspond to a “realistic routing”?
And also, it used to work; simBrief would compute plausible routings for all alternates individually in the past. The issue is that now, it computes a plausible/realistic routing to the main alternate, and then uses the exact same routing (or a variant thereof) for all alternates, even when said alternates are in the complete opposite direction from said routing…
Sorry for my abrupt reply earlier, BTW; it’s just the fact that you wrote a somewhat long and elaborate answer makes the fact that it probably somewhat missed the point I was trying to make so much more frustrating than if you had been laconic
→ plausible and sensible routing for this particular airport pair
second alternate:
PANC TED J115 AKN CYXY
-> from the initial destination, fly 252 nm away from the
alternate (i.e. in the wrong/opposite direction), then
simply double back and fly a 666 nm direct leg
direct: 435nm, overhead: 110.7% (482 nm!!!)
Hi Tim, thanks for the report! This was indeed a bug and should now be fixed. Can you confirm if it’s working for you now?
Basically, I think like @dougsnow said, the alternate routings are more of a regulatory requirement than anything. Real-world the flight will almost always be cleared on a different route.
SimBrief includes the SIDs because many flight planning systems I’ve seen also do this. I agree it might not make much sense, but in this case SimBrief is just copying the other systems in the interest of “realism”.
Looking at the real-world OFPs in your example, many of them do include the SID in the alternate routings. Certainly all of the LH OFPs do. Others might not depending on the flight planning software used and/or possibly airline policy.
Appears to be fixed indeed. It has been going on for a while (at least several weeks, I think, perhaps some months?); I always felt like reporting it but thought “surely someone will notice it soon anyway” so it kept going down on my TO-DO list
