Forces on a pallet
It sounds like there's a bit of confusion about the forces acting on a pallet during acceleration, rotation and climb.
There are two frames of reference to view it in - relative to the direction of gravity, and relative to the deck of the aircraft. It doesn't much matter which.
Accelerating the pallet to stay with the aircraft is done through the attachments. Combined with gravity there are forces due to the acceleration of the aircraft. These can increase or reduce the demands on the attachments as compared with standing parked on the ramp - in extremis, flying a parabolic vomit comet trajectory would mean the pallet had no forces through the attachments. The mix of locks, straps, and friction all have to provide these forces.
If the cargo's not to move, effective gravity (incorporating weight and acceleration of the aircraft) and the reaction forces through the attachments, which you could choose to resolve parallel and perpendicular to the deck, always balance. If there's no acceleration, then the total force through the attachments is just 1g from gravity, although the direction it points changes based on orientation of the deck to horizontal.
On initial acceleration for take off, the attachments deal with g from gravity and about 0.3g forwards - leading to a total of 1.044g on the attachments, acting 16.7 degrees forwards of the vertical. This forward component reduces as drag builds going down the runway with the same thrust.
On rotation, sharply increasing drag should reduce the acceleration perhaps even pulling back on the load, as the gravity vector also rotates backwards.
Acceleration during the climb pulls gently forwards to keep the load with the deck, while the gravity vector remains laid back. A constant speed climb means you just get a total of 1g of gravity acting backwards from vertical: loading the attachments more lightly perpendicular to the deck, but requiring a forward along-the-deck component of force from the attachments.
The total forces to accommodate, without turbulence or sharp turns, aren't much bigger than 1.1g - however, the direction shifts more, which could affect the relative burden on straps and locks.
That's from a physicist's perspective: maybe that helps, maybe it doesn't.
Last edited by awblain; 9th May 2013 at 05:21.
Reason: Error corrected - "effective gravity".