Expert: James Bell - 8/16/2006

Question
Hi, I'm thinking of cross training to the loadmaster field and just want to know, what can I expect in the techschools including water and land survival and do I get train on jumping out of the aircraft? lastly can you give me an example of calculating CG? Your help will be most appreciated.

Answer
Greetings Tyrone -

You will attend two technical schools ... basic loadmaster school and TTU for your specific aircraft.  In the basic school you will ONLY learn weight and balance and a few loading skills.  I'll get into weight and balance in a bit.

In your second school you will learn the specifics of your aircraft, be it C-5, C-17 or C-130.  This will include the uniqe weight and balance characteristics and cargo upload/download along with load planning.

Survival school will consist of classroom study, a week in the field to include escape and evasion, and some time in a simulated POW camp.  Certain aspects of the course are classified, so you will have to experience that on your own.  Water survival is roughly three days after basic survival and is done at the base swimming pool.

If you are assigned to an airdrop aircraft, even though you will wear a parachute for safety, your survival school will be non-parachute, and you won't receive any formal training for the parachute.  Only pilots on aircraft with ejection seats are sent to parachute survival school.  Only PJ's and those on jump status will be given formal jump training.  Remember, your job is to stay with the aircraft.

WEIGHT AND BALANCE -- CG (Center of Gravity)

This will be the bulk of your entire first school, and you will learn the tricks to mastering this subject.  But, here it is in a nutshell ...

Realize I took this course when I was 20 ... and that was back in 1980.  But the math used on the aircraft hasn't changed since planes first started flying.

Here is the basic formula that will guide ALL your weight and balance lessons (referred to as the WAM formula): W*A=M.  W is weight.  A is arm (a specified distance).  M is moment.  Weight, times a distance, will generate a moment.  Think of it as similar to foot pounds of torque.

Quick example -

You have a board resting on a pivot point.  On one end you place a 10 pound weight, 30 inches from the balance point.  How far would you need to place a 5 pound weight on the other side to balance the beam?

10 pounds * 30 inches = 300 moments.  So you need to have a 5 pound weight generate 300 moments on the other side.  300 / 5 = 60.  So, a 5 pound weight placed 60 inches from the balance point will equal the force generated by a 10 pound weight placed 30 inches in the opposite direction.

Airplanes aren't balanced from a central point, but from what's call an RDL (reference datum line).  This is a point in front of the aircraft from which all distances are measured.  These distances are often referred to as stations.  Station 500 would be 500 inches from the reference datum line.  The RDL for each aircraft is specific to that airplane.  It is designed to start from an imaginary point in front of the nose so that all stations are positive numbers.

Every airplane out there -- military or civilian -- has three coordinates to specify a point on the aircraft: Station, waterline and buttline.  Think of them as the X, Y, and Z axis of the airplane.  Stations identify locations from nose to tail.  Waterline goes from the ground up to the tail.  Buttline refers to the distance left or right of the centerline of the aircraft.  For weight and balance purposes, you are only interested in station measurements.

Here is an example of how you would find the CG of a vehicle, although an aircraft would be done in the same manner: You have a two axle vehicle that weighs 5000 pounds.  The front axle weighs 3000 pounds and the rear axle weighs 2000 pounds.  The wheelbase of the vehicle is 100 inches, and the RDL is 25 inches in front of the front axle.  Where is the center of gravity (CG) of the vehicle?

Moments for the front axle -
25 * 3000 = 75000

Moments for the rear axle -
Distance from RDL to rear axle = 25 + 100 = 125
125 * 2000 = 250000

Total moments = 325000

Now you run the WAM formula in reverse.  You need to find out the arm for the CG.  You know the moments and weight, now find the arm ... 325000 / 5000 = 65

The center of gravity of the vehicle is 65 inches from the RDL, or 40 inches behind the front wheel, and 60 inches in front of the rear wheel.

General informaton about cargo aircraft.  A basic C-5 weighs 350,000 lbs.  A C-130 weighs 150,000 lbs.  A KC-10 weighs 250,000 lbs.  Because weights that huge over such long distances generate HUGE moments, we use what's called SIMPLIFIED moments.  The C-5 simplified its moments by 100,000.  This means you simply lop off the last five digits of the moments.

A 2500 pound pallet at station 1428 generates 3570000 moments, or 35.7 simplified moments.

And the lesson can go on and on.  But, I've given you an idea of what you are getting into.  Believe me, it gets easy with a little practice and it will be second nature to you in just a few short months of training.  I haven't done serious loadmaster work since 1987, yet I still remembered all of this to pass on to you.

You are in for a wonderful experience and I don't think you will regret retraining at all.  Being an enlisted aircrew member is one of the most coveted jobs in the Air Force.  You will see more of the world in a single year than most see in an entire 20 year non-flying career.

If you have any more questions, don't hesitate to write back.

Good luck,
James Bell