error CS0136: A local variable named `hit' cannot be declared in this scope because it would give a different meaning to `hit', which is already used in a `parent' scope to denote something else

well… never seen this before… trying to do damage to other ships with Raycast

snippet:

	if (dist < 500 && IsBlueTeamFighter == true) {
			MachineGuns.SetActive (true);

			RaycastHit hit = new RaycastHit ();
			if (Physics.Raycast (transform.position, fwd, 500))
			if (Hit.collider.tag == "Red_Team_fighter") {
				if(FireRate < 0.01){ // damage from mach guns limited by firea rate
					Hit.transform.gameObject.GetComponent(HealthDamage).IsHit = true;
					Hit.transform.gameObject.GetComponent(HealthDamage).damage = 1;
					Instantiate(BulletHit, hit.point, Quaternion.identity);
				}
			}

 			

		if (dist < 500 && IsBlueTeamFighter == false) {
			MachineGuns.SetActive (true);

			RaycastHit hit = new RaycastHit ();
			if (Physics.Raycast (transform.position, fwd, 500))
			if (Hit.collider.tag == "Blue_Team_fighter") {
				if(FireRate < 0.01){ // damage from mach guns limited by firea rate
					Hit.transform.gameObject.GetComponent(HealthDamage).IsHit = true;
					Hit.transform.gameObject.GetComponent(HealthDamage).damage = 1;
					Instantiate(BulletHit, hit.point, Quaternion.identity);

				}
			}

		}
		}

full script

using UnityEngine;
using System.Collections;

public class AIFighter : MonoBehaviour {

	private int index;

	public float rotationSpeed = 12f;
	private float MaxAttackingDistance = 300;
	private float MaxLockonDistance = 2000;
	private float dist;
	private float blueFighterHP = 25;
	public float FireRate = 0.03f;

	public bool IsBlueTeamFighter;
	public bool rotating;
	public bool Attacking = true;
	public bool LowFule;
	public bool retreating;
	public bool Refuling;

	public GameObject target;
	public GameObject[] Targets;
	public GameObject MachineGuns;
	public GameObject BulletHit;
	public RaycastHit Hit;


	public float FighterFule = 10000;


	public void Start (){

		if (IsBlueTeamFighter == true) {
			Targets = GameObject.FindGameObjectsWithTag ("RedTeam_Fighter");
			index = Random.Range (0, Targets.Length);
			target = Targets [index];

			if (target = null) {
				Targets = GameObject.FindGameObjectsWithTag ("RedTeam_Fighter");
				index = Random.Range (0, Targets.Length);
				target = Targets [index];
			}

		}
		else
		{

			if (IsBlueTeamFighter == false) {
				Targets = GameObject.FindGameObjectsWithTag ("BlueTeam_Fighter");
				index = Random.Range (0, Targets.Length);
				target = Targets [index];


				if (target = null) {
					Targets = GameObject.FindGameObjectsWithTag ("BlueTeam_Fighter");
					index = Random.Range (0, Targets.Length);
					target = Targets [index];
				}

			}

		}
	}
	// END START___________________________________________________________________________________________________________
	//______________________________________________________________________________________________________________



	void LateUpdate () {

		//______________________________________________________________________________________________________________

		// Move Forward
		FireRate -= 0.01f;
		if(FireRate <0.01f){ FireRate = 0.3f;}

		FighterFule -= 1 * Time.deltaTime;

		//______________________________________________________________________________________________________________


		//______________________________________________________________________________________________________________
		if (dist > MaxLockonDistance) {
			target = null;
			Attacking = false;
			rotating = false; 
		}
		//______________________________________________________________________________________________________________

		//______________________________________________________________________________________________________________
		if(retreating == true){
			transform.rotation = Quaternion.Slerp (target.transform.rotation, Quaternion.LookRotation (target.transform.position - transform.position), Time.deltaTime * rotationSpeed);
		}

		if (Refuling == true) {
			retreating = false;
			FighterFule += 100 * Time.deltaTime;
			if(FighterFule == 10000){
				Refuling = false;
				Attacking = true;

			}
		}
		//______________________________________________________________________________________________________________


		//______________________________________________________________________________________________________________
		if (Attacking == true) {
			// Rotate to look at Target;
			transform.rotation = Quaternion.Slerp (target.transform.rotation, Quaternion.LookRotation (target.transform.position - transform.position), Time.deltaTime * rotationSpeed);
		}
		//______________________________________________________________________________________________________________



		//______________________________________________________________________________________________________________
		// get the distance to target
		dist = Vector3.Distance (target.transform.position, transform.position);
		Vector3 fwd = transform.TransformDirection(Vector3.forward); //the direction the fighter is facing
		//______________________________________________________________________________________________________________




		//______________________________________________________________________________________________________________

		if (dist < 500 && IsBlueTeamFighter == true) {
			MachineGuns.SetActive (true);

			RaycastHit hit = new RaycastHit ();
			if (Physics.Raycast (transform.position, fwd, 500))
			if (Hit.collider.tag == "Red_Team_fighter") {
				if(FireRate < 0.01){ // damage from mach guns limited by firea rate
					Hit.transform.gameObject.GetComponent(HealthDamage).IsHit = true;
					Hit.transform.gameObject.GetComponent(HealthDamage).damage = 1;
					Instantiate(BulletHit, hit.point, Quaternion.identity);
				}
			}

 			

		if (dist < 500 && IsBlueTeamFighter == false) {
			MachineGuns.SetActive (true);

			RaycastHit hit = new RaycastHit ();
			if (Physics.Raycast (transform.position, fwd, 500))
			if (Hit.collider.tag == "Blue_Team_fighter") {
				if(FireRate < 0.01){ // damage from mach guns limited by firea rate
					Hit.transform.gameObject.GetComponent(HealthDamage).IsHit = true;
					Hit.transform.gameObject.GetComponent(HealthDamage).damage = 1;
					Instantiate(BulletHit, hit.point, Quaternion.identity);

				}
			}

		}
		}

		//______________________________________________________________________________________________________________





		//______________________________________________________________________________________________________________

		if(dist > 500) {
			MachineGuns.SetActive (false);

		}
		//______________________________________________________________________________________________________________
			
	
		//______________________________________________________________________________________________________________

		if (dist > MaxAttackingDistance) {
			Attacking = true;
			rotating = false;

			//Re-Aquire Target
		} else {
			Attacking = false;
			rotating = true;
		}
		//______________________________________________________________________________________________________________



		//____Avoid when close___________________________________________________________________________________________
		if (rotating == true) {

			// AVOID OTHER FIGHTER ?

		}
		//______________________________________________________________________________________________________________

		//___Fule_______________________________________________________________________________________________

		if (FighterFule < 3000 && IsBlueTeamFighter == true) {
			Targets = GameObject.FindGameObjectsWithTag ("BlueTeam_CarrierDock");
			index = Random.Range (0, Targets.Length);
			target = Targets [index];
			if (dist > 6000) { target = null;  }
			retreating = true;
				
		}

			if (FighterFule < 3000 && IsBlueTeamFighter == true) {
				Targets = GameObject.FindGameObjectsWithTag ("BlueTeam_CarrierDock");
				index = Random.Range (0, Targets.Length);
				target = Targets [index];
			if (dist > 6000) { target = null;  }
			retreating = true;
		}
		//______________________________________________________________________________________________________________







	}  // END LATEUPDATE____________________________________________________________________________________________
	//______________________________________________________________________________________________________________


}

the H in hit is capitalized in multiple spots. you want it lowercase, youll also want to retrieve the hit information from your raycast.

 RaycastHit hit;

if (Physics.Raycast (transform.position, fwd, out hit, 500))