How many times has this occurred to you? You and the lobby destroy all the enemies in the map, and you have time left on the clock, but the game still only registers as an A rank when it should be an S. Who can explain why this happens sometimes? Even when I host an 8-player lobby with all good players, we clear everything: first section, mission update, and third section, we'd have over 30 seconds left yet the game still thinks we only got A rank. Why does this happen?
Which map you caught this bug? It frequently happened in normal Moscow way back when the latter was just released but it was fixed later. Other than that, I only had it once in Avalon about a month ago, as far as I can remember.
Based on my experience the main reason for a mission to end up in an A rank is not clearing a large number of optional enemies (e.g. weapons on ships, accompanying fighters) in Mission Update. This is particularly true with the enemy fleet in Pipeline, stealth destroyers in Tokyo, and BM carriers in Avalon. I don't know whether this is the case for you, but when it happens to me, this is usually the reason.
Hm... Now that you said it, I believe we had this discussion before. It's not a bug but an unfortunate circumstance that happens when your room fails to score enough by the time the last enemy is downed. The number of nontargets you need to destroy during EM depends on how many of them are left pre-EM. Usually, if you manage to destroy everything during 1st phase, you just need to focus on handling the EM targets and leave the nontargets alone.
This discussion has definitely come up before. Then too there was never an answer as to why. There is no formula in regards to the mission update part - I think the assumption of having to down yellow targets at this part of the mission is based on an overly finite assessment of how points are tallied and the hope that the spattering of yellow targets here can offset failure to best part one of the mission. Seeing as how part one doesn't end until you've destroyed everything or you hit that 3 minute timer, it's impossible to finish part one early and then still have to rely on yellow targets in the mission update. And missing a few shoudln't have much of an impact. As for part two of the mission, with the exception of Excalibur, and Pipeline when the SR-71 shows up, no mission in the game as far as I know lets you get an S without wiping out all of the targets on the map.
As for what is happening in this particular case, I've realized that particularly with pipeline, and on occassion with a couple other maps, the game will take a bit of time to spawn all of its targets if you wipe them out too quickly or wipe out a bunch all at once. They usually take some time in manifesting a few additional air targets. Aerospace has the longest period I think. I've seen it happen where you'll fly around for almost ten seconds looking at the radar for new targets and then assume nothing's doing, only for something to suddenly pop up out of nowhere. I think it is an error in how quickly the system generates the new targets, and therefore is likely to be worse if you're in a fairly good room but still cutting it a tad close on time (30--secs or less).
I agree its like Qbicle said, because pipeline spoiling the A rank happens with the ships EM (killikg the red targets quickly) .. So it dependes on what EM comes. Avalon is the one weird to me due than the EM with a lot of red targets use to spoil S rank.. thats really strange.
In the other hand, Tokyo hard its one of the missions I've seen awarding S rank with some fighters still flying around.
The Blackbird in Pipeline is like a bonus or some king of little easter egg, that gives good points but its never obligatory to kill to get S rank.