Definition
The exchanges of energy that occur in flight as the airplane converts one form of energy into another, or as energy is added by the engine and removed by drag. The pilot manages these exchanges using pitch and power: pitch trades altitude (potential energy) for airspeed (kinetic energy) or vice versa, while power adds energy to the system and drag continuously removes it.
Plain English
An energy transaction is any time the airplane swaps one kind of energy for another, or gains or loses energy overall. Climbing trades speed for height. Descending trades height for speed. Adding throttle puts more energy in. Drag is always taking some out.
Context Anchor
Seen in the Airplane Flying Handbook discussion of managing an airplane’s energy state, especially when comparing climbs, descents, turns, and speed changes.
Derivation
A 'transaction' comes from Latin 'transigere,' meaning to drive through or carry across. In banking, it means money moving between accounts. Here, the same idea applies to energy: it is being moved between the airplane's altitude account and its airspeed account, with the engine making deposits and drag making withdrawals.
Why Pilots Care
Recognizing these exchanges lets a pilot keep the airplane at a safe speed and altitude without losing control or wasting fuel.
Analogy
Think of altitude and airspeed as two bank accounts. The pilot can transfer between them with pitch, and the engine can deposit into either by adding power. Drag is a small, constant withdrawal that never stops.
Grounding Statement
If you raise the nose without adding enough power, the airplane may gain altitude by giving up speed.
Intuition Check
Do not read “transactions” as paperwork, money, or a radio exchange. Here it means exchanges of airplane energy: speed, altitude, power added, and energy lost to air resistance.
Example Sentence 1
Pulling the nose up without adding power is an energy transaction that trades airspeed for altitude.
Example Sentence 2
Adding power creates an energy transaction that turns chemical energy into both kinetic and potential energy during a climb.