Health values won't work?

I had a friend help me create a script for a flying thing, however, we can't seem to get the health to work, and the thing keeps changing locations of stuff on the plane, We have adjusted the values of our scripts and tried several different methods, studio doesn't really show any errors. I also wanted to get feedback as to how well we did on this script, it took a while to make and I wanted to see if there was anything I should do differently.\

wait(1)

local v = script.Parent
local seat = v.DriverSeat
local engine = v.Engine
local pos = engine.Pos
local rot = engine.Rot
local Parts = 0
local start = 0

local destroyed = false

local max_health = 5000
local armor = v.Armor
armor.Value = max_health

local bar = script.Parent.ArmorBar
local fires = 0

function Weld()
 local rep = game.Lighting:findFirstChild(script.Parent.Name)
 local e = engine:GetChildren()
 for i=1,#e do
  if e[i].className == "Weld" then
   e[i]:destroy()
  end
 end
 e = v:GetChildren()
 for i=1,#e do
  if e[i]:IsA("BasePart") and e[i]~=engine then
   local w = Instance.new("Weld",engine)
   w.Name = "Weld"..e[i].Name
   w.Part0 = engine
   w.Part1 = e[i]
   w.C0 = rep:findFirstChild("Engine").CFrame:inverse()
   w.C1 = rep:findFirstChild(e[i].Name).CFrame:inverse()
  end
 end
 engine.Anchored = false
 engine.CFrame = engine.CFrame + Vector3.new(0,0.1,0)
 engine.Anchored = true
 engine.CFrame = engine.CFrame - Vector3.new(0,0.1,0)
 for i=1,#e do
  if e[i]:IsA("BasePart") then
   e[i].Anchored = false
  end
 end
end

seat.ChildAdded:connect(function(w)
 if w.className == "Weld" and w.Name == "SeatWeld" then
  wait()
local  t = w.Part1
  if t~=nil and t.Parent~=nil then
 local  char = t.Parent
 local  pilot = game.Players:GetPlayerFromCharacter(char)
   if pilot ~= nil then
   local ctrl = script.Control:clone()
    ctrl.Vehicle.Value = v
    ctrl.Disabled = false
    ctrl.Parent = pilot.PlayerGui
   end
  end
 end
end)

Weld()

function Explode()
 pcall(function()
 local e = v.Engine:GetChildren()
 for i=1,#e do
  e[i]:destroy()
 end
 local e = v:GetChildren()
 local center = v.Part10.CFrame.p
 for i=1,#e do
  if e[i]:IsA("BasePart") then
   e[i].Velocity = e[i].Velocity + (e[i].CFrame.p-center).unit * math.random(30,80)
  end
 end
 local boom = Instance.new("Explosion",workspace)
 boom.Position = center
 boom.BlastPressure = 10
 boom.BlastRadius=20
 end)
 delay(7.5,function()
  local e=v:GetChildren()
  for i=1,#e do
   if e[i]:IsA("BasePart") then
    e[i]:destroy()
    wait()
   end
  end
  v:destroy()
 end)
end

function ImpactDamage(hit, self)
 if hit ~=nil then
  if hit.Parent~=nil and hit.Parent:findFirstChild("Humanoid") ~=nil and destroyed then
   hit.Parent.Humanoid.Health = hit.Parent.Humanoid.Health - ((self.Velocity.magnitude)*10*(100+self:GetMass()/100))/1000
  elseif hit.Parent ~= v and hit.CanCollide and not destroyed and hit.Parent:findFirstChild("Humanoid")==nil then
   --print(self.Velocity.magnitude,(self:GetMass()+20))
   armor.Value = armor.Value - ((self.Velocity.magnitude)*10*(100+self:GetMass()/100))/500
  end
 end
end
e = v:GetChildren()
for i=1,#e do
 if e[i]:IsA("BasePart") then
  e[i].Touched:connect(function(hit) ImpactDamage(hit,e[i]) end)
 end
end

function UpdateBar()
 if armor.Value < 0 then
  if not destroyed then
   destroyed = true
   Explode()
  end
  armor.Value = 0
 end
 if armor.Value < max_health /2 and fires < math.floor(15*(.5-armor.Value/max_health)) then
  local a = math.random(1,12)
  if a < math.random(2,4) then
   local f = Instance.new("Fire",v:GetChildren()[math.random(1,#v:GetChildren())])
   f.Heat = 40*(.5-armor.Value/max_health)
   f.Size = f.Heat
   fires = fires + 1
  end
 end
 bar.Mesh.Scale = Vector3.new(armor.Value/max_health,1,1)
 bar.Mesh.Offset = Vector3.new((1-armor.Value/max_health)*bar.Size.X/2,0,0)
end

Many have been asking where and what the exact issue is, I don't really know where it is except that the first issue is with the health bar at the top, the health bar is actually not a humanoid, it is a brick that shrinks when the plane gets hit and when the bar hits a certain level the plain sets on fire, and when the health bar is gone the plane explodes, the other issue is with the wielding, somehow it keeps wielding random plane parts to the health bar.