Is there any way to take out helicopters and tanks while on foot using the Assault class?
Whenever a tank or a helicopter comes blazing by in Battlefield 3 and I'm on foot using the Assault class, I find myself completely overwhelmed. The moment I step out of cover I'm destroyed by their mighty weapons, unable to resist in the slightest. As a result, I find myself pinned down, completely useless to the team. This doesn't really help me improve and doesn't help my team win so I'm beginning to wonder if there's anything I can do to help in this situation. I can throw a grenade, but even when it manages to connect it only seems to do a small amount of damage.
Does the Assault class have any other weapons or tools that can be used to help take out helis or tanks? If not, how should I react as this class to enemies inside these vehicles instead?
Best Bets
According to the official Prima game guide (Engaging Vehicles, p. 16), your best option is the M320 grenade launcher, which you'll unlock very early. And that's not at all an ideal option since you won't be doing nearly as much damage as a rocket, mine, or tank would do. My feeling is that it's like throwing rocks at a rhino. Sure, eventually you'll do damage, but long before you do enough damage it'll figure out where you are. Bad scene. And as for helicopters, good luck getting them to stay still long enough for a grenade launcher takedown.
Note that if a chopper or heavily armored vehicle is very badly damaged (spewing smoke), it might be worth a grenade launcher or even a grenade attack in the hope of shaving off those last few hit points. But don't expect miracles.
Small Arms Fire
Small arms fire won't damage heavily armored vehicles. You can damage some light vehicles with small arms fire, but don't count on fast results.
As a better strategy you can damage people in the least-armored vehicles, buggies and jeeps. If you pull it off, as a bonus you get an intact vehicle to jack.
M320 Example
As an example of probably the best case scenario, grenade launcher vs. lightly armored vehicle: Earlier tonight I disabled a couple of APCs with four grenade launcher rounds each.
Though I can't complain about the result, in one case the APC had no gunner and the driver didn't jump out, drive away, or hop in the gunner's seat. In the other case the gunner... uh... had suboptimal situational awareness. And that's just disabling, not outright destroying; an engineer could have repaired them.
Against slightly more skilled opponents, or on a fully populated server, I doubt I would have have survived either attempt. To pump out four grenades takes a good 10-15 seconds including reload time.
What you can do
So as a rule, leave it to engineers with their rockets and mines, support with their C4, and people in vehicles.
Perhaps the most useful thing you can do as light infantry is to spot enemy vehicles. Just because you're not blowing it up yourself doesn't mean you're "completely useless". Spotting is actually very valuable, and it's disappointing how infrequently most players do that.
As assault you need to run away, or come back with an engineer (rpg) or support (c4) teammate to take on the tank.
Your options are:
ALWAYS spot the tank, no matter what, using your spot key. This way others can see it on the mini-map and hopefully run over to engage it with tank-appropriate weapons
toss a grenade at it. Won't do a ton of damage but every bit helps (think 5-10% max).
if you have the m320 grenade launcher equipped, you can ping it with grenades. The standard HE grenades will only do about 10% damage per hit.
In my testing, you'd have to hit the tank with 4-5 40mm grenades AND a hand grenade to get it down to 50% aka disabled state. So if you have no other options, go for it, but have no illusions that if it's assault vs. tank, you will lose.
Just because the tank is there doesn't mean you have to take it on. Discretion is often the better part of valor!
To summarize, the short answer is: No, you cannot effectively engage helicopters or tanks as Assault.
The best you can do is assist by taking out any engineers that attempt to repair the vehicle. If an engineer or another vehicle is already engaging the tank, you can do marginal contributions by hitting it with M320 rounds, with an emphasis on marginal. You have to give up med packs to do even that though, which is something you rarely want to do in good servers with squad-based teamplay.
Basically as Assault you get the best weapons in the game (see symthic for comparison. It's easy to underestimate how much better they are than engineer weapons.) plus the ability to heal and the crucial ability to revive teammates. In exchange for all that, you're utterly dependent on your teammates to handle any vehicles that show up. That's the deal.