Definition
A phase in aircraft development in which a prototype or experimental aircraft is built and flown to demonstrate that the chosen design, or the underlying design concept, actually works as intended. The aim is to confirm that the aircraft can perform safely and meet its intended purpose before moving on to certification testing or production.
Plain English
Building and flying an early version of an aircraft to show that the design idea really works in the air, not just on paper.
Context Anchor
Seen in aircraft development, modification approval, certification, and test-flight discussions.
Derivation
Prove' here carries its older engineering sense of 'to test' or 'to demonstrate by trial' (from Latin 'probare', meaning to test or examine), the same sense used in 'proving ground.' It does not mean 'prove' in the mathematical sense of absolute certainty.
Why Pilots Care
Aircraft in this phase are typically experimental and may not yet meet the safety and performance standards of certified aircraft. Pilots flying or working around them need to recognize that the design is still being tested.
Intuition Check
"Prove" does not mean simply believing the design is good or explaining why it should work. Here it means demonstrating it with evidence, such as testing, inspection, calculation, or operation.
Example Sentence 1
The first prototype was built primarily to prove the design concept, not to set performance records.
Example Sentence 2
Static load tests were performed to prove the design concept for the modified fuselage structure.