Jesus nut is a slang term for the main rotor retaining nut [1] or mast nut, which 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. More generally, Jesus nut (or Jesus pin) has been used to refer to any component that is a single point of failure which results in catastrophic consequences, and the only thing left to do is, metaphorically speaking, pray to Jesus, hence the name.
The term Jesus nut may have been coined by American soldiers in Vietnam; [2] 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. [3]
If the Jesus nut were to fail in flight, the rotor would detach from the helicopter [4] [lower-alpha 1] and the only thing left for the crew to do would be to "pray to Jesus." The nut/pin must be checked before the flight even though real 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. [5] [6] Some more recent helicopter systems do not have a Jesus nut.[ citation needed ]
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.
Another use for the term is found in rock climbing, in which it refers to the first piece of protection (some of which are also called "nuts") placed on a pitch. [7] This piece must be placed to resist an outward pull as well as a downward pull in order to avoid the possibility of a "zipper", in which the outward pull on the rope from the belayer arresting a falling climber pulls protection pieces from the bottom up. In addition, the Jesus nut prevents the possibility of a factor-two fall onto the belay anchor. [8]
In literature, the term "Jesus nut" was popularized in Chickenhawk by Robert Mason, a narrative about his experiences as a pilot in the Vietnam War. [9]
Marine M60A1 tankers used the term "Jesus Pin" in reference to a breech pin located on the 105mm main gun that needed to be removed in order to disassemble the breech block. Dropping the small pin would cause it to instantly disappear into the bowels of the tank's hull causing one or more members of the crew to cry out "Jesus" as an expletive.[ citation needed ]
The Bell UH-1 Iroquois is a utility military helicopter designed and produced by the American aerospace company Bell Helicopter. It is the first member of the prolific Huey family, as well as the first turbine-powered helicopter in service with the United States military.
An autogyro, or gyroplane, is a class of rotorcraft that uses an unpowered rotor in free autorotation to develop lift. While similar to a helicopter rotor in appearance, the autogyro's unpowered rotor disc must have air flowing upward across it to make it rotate.
Glossary of climbing terms relates to rock climbing, mountaineering, and to ice climbing.
The vortex ring state (VRS) is a dangerous aerodynamic condition that may arise in helicopter flight, when a vortex ring system engulfs the rotor, causing severe loss of lift. Often the term settling with power is used as a synonym, e.g., in Australia, the UK, and the USA, but not in Canada, which uses the latter term for a different phenomenon.
A Prusik is a friction hitch or knot used to attach a loop of cord around a rope, applied in climbing, canyoneering, mountaineering, caving, rope rescue, ziplining, and by arborists. The term Prusik is a name for both the loops of cord used to tie the hitch and the hitch itself, and the verb is "to prusik". More casually, the term is used for any friction hitch or device that can grab a rope. Due to the pronunciation, the word is often misspelled Prussik, Prussick, or Prussic.
Helicopter flight controls are used to achieve and maintain controlled aerodynamic helicopter flight. Changes to the aircraft flight control system transmit mechanically to the rotor, producing aerodynamic effects on the rotor blades that make the helicopter move in a desired way. To tilt forward and back (pitch) or sideways (roll) requires that the controls alter the angle of attack of the main rotor blades cyclically during rotation, creating differing amounts of lift at different points in the cycle. To increase or decrease overall lift requires that the controls alter the angle of attack for all blades collectively by equal amounts at the same time, resulting in ascent, descent, acceleration and deceleration.
The Lockheed AH-56 Cheyenne was an attack helicopter developed by Lockheed for the United States Army. It rose from the Army's Advanced Aerial Fire Support System (AAFSS) program to field the service's first dedicated attack helicopter. Lockheed designed the Cheyenne using a four-blade rigid-rotor system and configured the aircraft as a compound helicopter with low-mounted wings and a tail-mounted thrusting propeller driven by a General Electric T64 turboshaft engine. The Cheyenne was to have a high-speed dash capability to provide armed escort for the Army's transport helicopters, such as the Bell UH-1 Iroquois.
The Gyrodyne QH-50 DASH is a small drone helicopter built by Gyrodyne Company of America for use as a long-range anti-submarine weapon on ships that would otherwise be too small to operate a full-sized helicopter. It remained in production until 1969. Several are still used today for various land-based roles.
A coaxial-rotor aircraft is an aircraft whose rotors are mounted one above the other on concentric shafts, with the same axis of rotation, but turning in opposite directions (contra-rotating).
In rock climbing, an anchor can be any device or method for attaching a climber, a rope, or a load above or onto a climbing surface—typically rock, ice, steep dirt, or a building—either permanently or temporarily. The intention of an anchor is case-specific but is usually for fall protection, primarily fall arrest and fall restraint. Climbing anchors are also used for hoisting, holding static loads, or redirecting a rope.
Low-g condition is a phase of aerodynamic flight where the airframe is temporarily unloaded. The pilot—and the airframe—feel temporarily "weightless" because the aircraft is in free-fall or decelerating vertically at the top of a climb. It may also occur during an excessively rapid entry into autorotation. This can have a disastrous effect on the aircraft, particularly in the case of helicopters, some of which need the rotor to constantly be under a non-zero amount of load.
On a helicopter, the main rotor or rotor system is the combination of several rotary wings with a control system, that generates the aerodynamic lift force that supports the weight of the helicopter, and the thrust that counteracts aerodynamic drag in forward flight. Each main rotor is mounted on a vertical mast over the top of the helicopter, as opposed to a helicopter tail rotor, which connects through a combination of drive shaft(s) and gearboxes along the tail boom. The blade pitch is typically controlled by the pilot using the helicopter flight controls. Helicopters are one example of rotary-wing aircraft (rotorcraft). The name is derived from the Greek words helix, helik-, meaning spiral; and pteron meaning wing.
A rotorcraft or rotary-wing aircraft is a heavier-than-air aircraft with rotary wings or rotor blades, which generate lift by rotating around a vertical mast. Several rotor blades mounted on a single mast are referred to as a rotor. The International Civil Aviation Organization (ICAO) defines a rotorcraft as "supported in flight by the reactions of the air on one or more rotors".
A helicopter is a type of rotorcraft in which lift and thrust are supplied by horizontally spinning rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forward, backward and laterally. These attributes allow helicopters to be used in congested or isolated areas where fixed-wing aircraft and many forms of short take-off and landing (STOL) or short take-off and vertical landing (STOVL) aircraft cannot perform without a runway.
The center of gravity (CG) of an aircraft is the point over which the aircraft would balance. Its position is calculated after supporting the aircraft on at least two sets of weighing scales or load cells and noting the weight shown on each set of scales or load cells. The center of gravity affects the stability of the aircraft. To ensure the aircraft is safe to fly, the center of gravity must fall within specified limits established by the aircraft manufacturer.
A belay device is a mechanical piece of climbing equipment used to control a rope during belaying. It is designed to improve belay safety for the climber by allowing the belayer to manage their duties with minimal physical effort. With the right belay device, a small, weak climber can easily arrest the fall of a much heavier partner. Belay devices act as a friction brake, so that when a climber falls with any slack in the rope, the fall is brought to a stop.
The Fairey FB-1 Gyrodyne is an experimental British rotorcraft that used single lifting rotor and a tractor propeller mounted on the tip of the starboard stub wing to provide both propulsion and anti-torque reaction.
The Revolution Mini-500 is a 1990s American single-seat light helicopter, designed and built by Revolution Helicopter Corporation as a kit for homebuilding.
The KAI KUH-1 Surion is a twin-engine, transport utility helicopter developed primarily by Korea Aerospace Industries (KAI), Agency for Defense Development (ADD) and Korea Aerospace Research Institute (KARI) jointly with Eurocopter. In 2006, the research and development phase of the Korea Helicopter Project - Korea Utility Helicopter (KHP-KUH), costing around ₩1.3 trillion, was launched by the Agency for Defense Development in 2006. In 2012, full-scale production of the Surion commenced; KAI has been designated as the principal manufacturer of the type.
A single point of failure (SPOF) is a part of a system that, if it fails, will stop the entire system from working. SPOFs are undesirable in any system with a goal of high availability or reliability, be it a business practice, software application, or other industrial system.
Jesus nut The geared rotor retaining nut securing a helicopter blade system to the drive shaft. Aka 'Jesus pin.' One has faith the nut/pin will stay on and not crash, screaming, 'Oh, Jesus!'
The main rotor retention nut is a flight-critical component that secures the main rotor hub and blade assemblies to the static mast.
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