The T-47 Airspeeder is the New Republic's combat speeder. Available in eras 1-3, it costs about 250 credits. They are quite useful for recon and destroying enemy ground targets/turrets (except for the AA turret and AT-AA). They excel at both defensive and offensive operations. Each company receives 3 speeders. They require the light vehicle factory to be built.
The T-47 is very fast, only behind the IR's Speeder Bike. Since an Airspeeder can fly in the air, enemy units will have a hard time to target it. They cannot be easily destroyed by air strikes or orbital bombardments because it can fly out of the targeted area.
Its main weapon is a twin medium repeating blaster, which is effective against armored targets like the AT-ST, 2-M Tank and the AT-AT. These blasters do very little against infantry (But, in large numbers, it can kill any infantry unit). However, they do exceed at killing Dark Jedi/Sith because they are unable to attack air targets. The damage, made by these blasters, is reduced when faced against buildings (Due to the thicker armor used).
The T-47 also carries a harpoon and towcable, for cutting down moving AT-ATs, but they're rarely used because the speeder is vulnerable when doing so (Plus, in large numbers, they can take down AT-ATs faster with their blasters than with their towcables).
At eras 3-5, there is an upgraded version of the T-47 called the V-Wing. They have much heavier armor and have the 'Increase Firepower' ability but they're a little slower (Plus, the harpoon and towcables have been removed). They both require lots of micromanagement to be effective.
Use them, during your attack, as a scout (If Corran Horn is not available) and then call down an air strike or orbital bombardment to weaken the enemy defences. Use the infantry to capture a reinforcement point and call your tanks down to deal with the AA Turrets or AT-AAs. Once the anti-air defences are eliminated, call in a large swarm of Airspeeders (Or V-Wings) to hunt down the remaining enemy units and buildings.
When you're on the defensive, use a large swarm of them and head straight to the starting point. Once there, destroy all the enemy forces before they even leave their transports. Remember to destroy the AA turrets before they are completed and take out the AT-AAs before they leave their transports (Although the A.I never builds them to invade a planet for some reason).
When dealing with T-47 Airspeeders, use anti-air units like the AT-AA, the Kirov tank, the anti-air turret or gunships like the IDT and the LAAT.
The EotH have a rival, to the T-47, called the Airstraeker. It has a better main weapon than the Airspeeder but is much more expensive (Plus, they come in two per company and may lose to it due to their smaller numbers).