Definition
A flight condition in which the airplane is losing total mechanical energy faster than the powerplant can replace it, resulting in a simultaneous loss of airspeed and altitude that the pilot cannot arrest with pitch alone. Total energy is the sum of kinetic energy (airspeed) and potential energy (altitude); when both are decreasing together and thrust is insufficient to reverse the trend, the airplane is operating at a negative energy rate.
Plain English
The airplane is bleeding off speed and height at the same time, and the engine is not making enough power to stop it. Trading altitude for speed or speed for altitude no longer works because there isn't enough of either to give up.
Context Anchor
Seen in energy management discussions, especially during approach, go-around decisions, low-altitude maneuvering, and recovery from an increasing sink rate or decreasing airspeed.
Derivation
Energy rate' refers to how fast an airplane's total energy (speed plus altitude) is changing. 'Negative' means the rate is going the wrong way -- energy is leaving the airplane faster than it is being replaced. The phrase comes from energy-management theory, where pilots are taught to think of speed and altitude as a shared bank account rather than two separate things.
Why Pilots Care
Failure to recognize and correct negative energy rates can produce an unrecoverable sink or stall in the landing phase.
Analogy
It is like spending money from a small bank account faster than you can replace it. If the balance is low and the spending continues, you may run out before you can correct the problem.
Grounding Statement
Picture a base-to-final turn where the airplane is descending, the airspeed is decaying, and the throttle is already well forward -- both pieces of the energy account are draining at once.
Intuition Check
Negative does not mean the airplane has “bad energy” or no energy at all. Here, negative means the airplane’s useful speed-and-height state is decreasing over time.
Example Sentence 1
On final approach with full flaps and a high sink rate, the instructor pointed out that the airplane was in a negative energy rate and only an immediate power application would arrest the descent.
Example Sentence 2
A late flap extension without thrust increase can quickly produce negative energy rates on approach.