Definition
A unit of electrical capacity equal to the amount of charge delivered when a current of one ampere flows for one hour. In aviation, it is used to rate the storage capacity of an aircraft battery — for example, a 35 amp-hour battery can theoretically supply 35 amps for 1 hour, 1 amp for 35 hours, or any equivalent combination.
Plain English
A measurement of how much electricity a battery can hold and deliver over time. The bigger the number, the longer the battery can run things before it goes flat.
Context Anchor
Seen in aircraft battery descriptions and electrical system discussions, especially when estimating how long a battery may support electrical equipment.
Derivation
Combines 'ampere' (the unit of electrical current, named after French physicist André-Marie Ampère) with 'hour' (a unit of time). The pairing reflects that battery capacity isn't just about how much current it can push, but for how long it can keep pushing.
Why Pilots Care
Battery amp-hour rating determines how many engine starts are possible and how long essential electrical systems can operate if the alternator fails.
Analogy
Think of it like the size of a fuel tank — but for electricity. A bigger amp-hour rating is a bigger tank. How long it lasts depends on how fast you're 'burning' it.
Grounding Statement
A 10 amp-hour battery could, in simple terms, supply 1 amp for about 10 hours or 10 amps for about 1 hour, though real battery performance can be less than that.
Intuition Check
Amp hour does not mean the battery is delivering that many amps right now. It is a capacity rating: electrical flow multiplied by time.
Example Sentence 1
The aircraft's 35 amp-hour battery should power the essential bus for roughly 30 minutes after an alternator failure, depending on what equipment remains switched on.
Example Sentence 2
Preflight checks include verifying the amp-hour capacity matches the aircraft's expected electrical load.