Jesus nut
Slang term for the main rotor-retaining nut of some helicopters
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Interest in “Jesus nut” spiked on Wikipedia on 2026-02-25.
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Key Takeaways
- The main rotor retaining nut or mast nut, often colloquially referred to as the Jesus nut, holds the main rotor to the mast of some helicopters.
- A failure of this nut is likely to result in a crash.
- Origin of name The term Jesus nut may have been coined by American soldiers in Vietnam; the Vietnam War was the first war to feature large numbers of soldiers riding in helicopters.
- If the main rotor retaining nut were to fail in flight, the rotor would detach from the helicopter, hence the idea that all that would then be left for the crew to do would be to "pray to Jesus.
- For example, in 2000, the mast nut of a Bell 206B was removed to be repainted and was not restored and checked prior to a test flight.
The main rotor retaining nut or mast nut, often colloquially referred to as the Jesus nut, holds the main rotor to the mast of some helicopters. The related slang term Jesus pin refers to the lock pin used to secure the retaining nut. A failure of this nut is likely to result in a crash. More generally, Jesus nut (or Jesus pin) is used to refer to any component that is a single point of failure and whose breakdown would result in catastrophic consequences, the suggestion being that in such case the only thing left to do would be to "pray to Jesus“.
Origin of name
The term Jesus nut may have been coined by American soldiers in Vietnam; the Vietnam War was the first war to feature large numbers of soldiers riding in helicopters. The term may also have originated with the PBY Catalina, which had two Jesus bolts holding the wing onto the fuselage.
If the main rotor retaining nut were to fail in flight, the rotor would detach from the helicopter, hence the idea that all that would then be left for the crew to do would be to "pray to Jesus." The nut/pin must be checked before the flight, even though real-world examples of the Jesus nut/pin failing are rare. For example, in 2000, the mast nut of a Bell 206B was removed to be repainted and was not restored and checked prior to a test flight. The helicopter crashed within ten minutes of takeoff, killing the two occupants.
Other contexts
More recently, the term has been more generically applied throughout engineering to include any single component whose failure would cause catastrophic failure of the entire system.
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