With Battlefield 3's vehicle specialization mechanic, players can choose different specs to fill different roles with their vehicles. The attack helicopter is a special example because the gunner and the pilot get their own set of specializations that can make or break their effectiveness in the air. So, from one pilot to another, let's establish how to make one of the most effective helicopter set ups.
Determine your roles
First of, you need two people: pilot and the gunner. You and your friend must figure out who's doing one beforehand because your specs will be chosen depending on which seat you'll be in. The most important of the specs will be the countermeasures. The countermeasures are your last and only true defense against direct attacks and the pilot and gunner must choose their specs particularly.
For one, the pilot is recommended to carry ECM Jammers. Flares are nice, but the ECM Jammer is much more useful.
Surviving Critical Damage
The most difficult part of using the attack helicopter is surviving critical damage that disables your vehicle. Once you're on fire, everything goes to shit. If the pilot in this situation is carrying ECM jammers, the gunner should have the Fire Extinguisher equipped as a contingency. The two crew must preform a mid-air switch. This is pretty easy, despite how it may sound. All that must be done is the pilot bail and deploy his chute to reach the ground safely. The gunner, who has their fire extinguisher ready, switches into the pilot seat and uses the extinguisher to douse the engine fire. Once that's done, the helicopter is landed, fully repaired, and the crew re-assume their roles.
Staying in the Air
Real simple. Pilot makes use of ECM constantly to avoid a lock. Pilot should become evasive until the ECM reactivates. Pilots' ECM reactivates after 10 seconds. Chaff from ECM dumps for 5 seconds, leaving a 5 second window for hostiles to get a lock and fire. Pilots are recommended to dump ECM and dive below radar.
Fighting Enemy ArmorThis is the Heads Up Display from the pilot's view in an attack chopper. Notice the center of the screen features a cross-hair but also has an I shaped symbol. The cross-hair is directly foreword, but the I symbol is what you care about. That symbol shows you where your rockets will impact if fired at that moment. When you're making the approach on an enemy vehicle, you're to line up that I symbol with your target when you fire. A salvo of rockets will disable any armored vehicle. If your gunner has guided missiles, the missile will finish it off.
Attacking infantry is the Gunner's job. The pilot must provide a stable firing platform from which the gunner can eliminate ground units with ease. I bring your attention again to the Pilot's HUD. Notice at the bottom of the screen there is a rectangle with a small square inside of it. This is your Gunner's Field of View indicator. The large rectangle is the entire possible FOV of the gunner. The square is the current direction the gun is facing. By paying attention to this indicator, the pilot can help the gunner engage targets by rotating and positioning the chopper in such a way that the gunner has the most room to move the gun and follow them.
In simple terms, keep the little box in the middle of the big box.
Engaging Enemy Aircraft
Your real worry here is jets. Jets are fast and have really powerful cannons that can shred the shit out of the chopper. Luckily, it is very difficult, but very possible, for a jet to disable a chopper using only the cannon in one pass. So, as soon as the big bullets start to hit, it's time to move. The pilot must break off the engagement and get evasive. Once out of the way, locate and return fire against the belligerent jet. Use the heat-seekers to engage the jet and, at the very least, get him off of you.
Choppers are another story. It can either be very easy or very difficult. To win this, there are a few things to remember. First, do not forget you still have regular rockets. Second, guided missiles can lock on to any laser designated target, including the chopper right in front of you, should the pilot have the nose mounted Laser Designator. Third, do not fire both heat seekers at the same time. Wait for the enemy to deploy their flares first, then count to three, then fire the second.
Now then, for the combat. Face your attacker and lock on to him with your heat seekers. Should he do the same, dump ECM. If he dumps ECM, use your regular rockets until the ECM stops, then switch back to your heat seekers. All the while, you should be trying to gain altitude against the enemy chopper. If you are higher than he, your gunner can hit him while their's can not hit you. But, if he already has a clear altitude advantage, do NOT tilt backwards to keep him in your sights. That's a great way to crash. Instead, tilt forward and dive under him. Rise on the other side and engage. Lastly, keep your distance. If you get too close, you won't have enough time to deploy countermeasures and the gunner will easily bombard you with the chain gun. Keep distance and do the dance. But keep in mind that this tactic only works if you have the enemy in your sights. If the chopper sneaks up on you, you need a different tactic.
I just told you not to tilt backwards. This is kind of untrue. A friend of mine, Reatosnova, has mastered the skill of flying an attack helicopter backwards. When engaging, he flies backwards while staying under the radar. This is something to try. It allows the gunner to continue engaging the enemy chopper and prevents the enemy from using heat seekers.