The Airplane Weight-and-Balance Program


Your task is to write a program than can compute the weight and balance for a Cessna-150.

Things to know about weight and balance in airplanes.

Every load in the airplane has a weight and an arm. The weight describes how much it weighs, and the arm describes if the load pushes the plane nose-heavy or tail-heavy. The product of the weight and the arm is called the moment. For example, if I weigh 170 lbs and sit 39 inches behind the propellor, them my weight is 170 lbs, my arm is 39 inches, and my moment is 6,630 lbs-inches.

Every plane has a weight limit. If the plane weighs more than it should, it will not be able to climb very well and will land too fast.  If the plane weights lots more than it should, the wings will fall off during manuvering. The most my plane can weigh is 1,600 lbs.

Every plane has center of gravity limits. These describe how nose/tail heavy the plane can be and remain safe. On my plane, the center of gravity must remain between 31.3 and 37.4 inches behind the propellor or I will be in danger.

The Center of Gravity of a plane is just the sum of the moments divided by the sum of the weights.

The plane uses 6 gallons per hour. The plane flies 100 mph. Each gallon weighs 6 pounds. The tanks can only hold 21 gallons max.

Here is a sample weight and balance problem.

Item
 Weight
 Arm
 Moment
Empty Plane
 1067.9 lbs
 32.94 inches
 35,176 lb-inches
Me
 170 lbs
 39.0 inches
 6,630 lb-inches
Lori
 105 lbs
 39.0 inches
 4,095 lb-inches
Fuel
 132 lbs
 39.5 inches
 5,214 lb-inches
Luggage
 100 lbs
 64 inches
 6,400 lb-inches
TOTAL
 1,574 lbs
57,515 lb-inches
Center of Gravity = 57,515 / 1,574 = 36.54 inches


Your task is to write a web page using javascript that computes the weight and balance for a given flight.

Item
 Points
Can compute the weight and center-of-gravity for a C-150
 10,000,000
Alerts the user if the plane is over-weight
 10,000,000
Alerts the user if the plane is out of balance
 10,000,000
Complains about stupid entries (negative weight, people who weigh more than 300 lbs)
 10,000,000
Turned in after Wed Nov 13th
 -10,000,000
Turned in after Fri Oct 15th
 -10,000,000