Frangibility

Last updated

A material is said to be frangible if through deformation it tends to break up into fragments, rather than deforming elastically and retaining its cohesion as a single object. Common crackers are examples of frangible materials, while fresh bread, which deforms plastically, is not frangible.

Contents

A structure is frangible if it breaks, distorts, or yields on impact so as to present a minimum hazard. A frangible structure is usually designed to be frangible and to be of minimum mass.

A plaque marking the frangible section of a London pavement, designed to be broken to release smoke in the case of an underground fire. Smoke Outlet.jpg
A plaque marking the frangible section of a London pavement, designed to be broken to release smoke in the case of an underground fire.

Light poles

A frangible light pole base is designed to break away when a vehicle strikes it. This lessens the risk of injury to occupants of the vehicle. [1]

Airport structures

Following a serious incident where an aircraft hit a donut lighting structure at San Francisco International airport, [2] the FAA instigated frangible design rules for such structures. [3] A frangible object was defined as "an object of low mass, designed to break, distort or yield on impact, so as to present the minimum hazard to aircraft". This characteristic is seemingly contradictory to the operational requirements for stiffness and rigidity imposed on this type of equipment.

In order to develop international regulation for the frangibility of equipment or installations at airports, required for air navigation purposes (e.g., approach lighting towers, meteorological equipment, radio navigational aids) and their support structures, [4] ICAO initiated the "Frangible Aids Study Group" in 1981, with the task to define design requirements, design guidelines and test procedures. This work has resulted in part 6 of the Aerodrome Design Manual, dedicated to frangibility. [5]

An overview of the activities carried out to achieve these results is given in "Frangibility of Approach Lighting Structures at Airports". [6] The missing reference (17) in this article is in "Impact simulation of a frangible approach light structure by an aircraft wing section". [7] With the evolution of numerical methods suitable for impact analysis, a Chapter 6 was added to the Aerodrome Design Manual part 6, dedicated to "numerical simulation methods for evaluating frangibility". It states that numerical methods can be used to evaluate the frangibility of structures, but that the analytical models should still be verified through a series of representative field tests.

Of all equipment or installations at airports required for air navigation purposes, ICAO has not yet formulated frangibility criteria for the tower structure supporting the ILS glide path antenna, "considering its unique nature", basically: its size. A first publication on this subject is given in "Frangible design of instrument landing system/glide slope towers". [8]

Bullets

A sequence of photos showing a frangible bullet fracturing when subjected to high velocity strain waves Frangible bullet stress test.jpg
A sequence of photos showing a frangible bullet fracturing when subjected to high velocity strain waves

A frangible bullet is one that is designed to disintegrate into tiny particles upon impact to minimize their penetration for reasons of range safety, to limit environmental impact, or to limit the danger behind the intended target. Examples are the Glaser Safety Slug and the breaching round.

Frangible bullets will disintegrate upon contact with a surface harder than the bullet itself. Frangible bullets are often used by shooters engaging in close quarter combat training to avoid ricochets; targets are placed on steel backing plates that serve to completely fragment the bullet. Frangible bullets are typically made of non-toxic metals, and are frequently used on "green" ranges and outdoor ranges where lead abatement is a concern. [9] [10]

Glass

Tempered glass is said to be frangible when it fractures and breaks into many small pieces. [11]

Other

Some security tapes and labels are intentionally weak or have brittle components. The intent is to deter tampering by making it almost impossible to remove intact. [12]

See also

Related Research Articles

<span class="mw-page-title-main">Airport</span> Facility with a runway for aircraft

An airport is an aerodrome with extended facilities, mostly for commercial air transport. Airports usually consist of a landing area, which comprises an aerially accessible open space including at least one operationally active surface such as a runway for a plane to take off and to land or a helipad, and often includes adjacent utility buildings such as control towers, hangars and terminals, to maintain and monitor aircraft. Larger airports may have airport aprons, taxiway bridges, air traffic control centres, passenger facilities such as restaurants and lounges, and emergency services. In some countries, the US in particular, airports also typically have one or more fixed-base operators, serving general aviation.

<span class="mw-page-title-main">Runway</span> Area of surface used by aircraft to takeoff from and land on

According to the International Civil Aviation Organization (ICAO), a runway is a "defined rectangular area on a land aerodrome prepared for the landing and takeoff of aircraft". Runways may be a human-made surface or a natural surface. Runways, taxiways and ramps, are sometimes referred to as "tarmac", though very few runways are built using tarmac. Takeoff and landing areas defined on the surface of water for seaplanes are generally referred to as waterways. Runway lengths are now commonly given in meters worldwide, except in North America where feet are commonly used.

<span class="mw-page-title-main">Instrument landing system</span> Ground-based visual aid for landing

In aviation, the instrument landing system (ILS) is a precision radio navigation system that provides short-range guidance to aircraft to allow them to approach a runway at night or in bad weather. In its original form, it allows an aircraft to approach until it is 200 feet (61 m) over the ground, within a 12 mile (800 m) of the runway. At that point the runway should be visible to the pilot; if it is not, they perform a missed approach. Bringing the aircraft this close to the runway dramatically increases the range of weather conditions in which a safe landing can be made. Other versions of the system, or "categories", have further reduced the minimum altitudes, runway visual ranges (RVRs), and transmitter and monitoring configurations designed depending on the normal expected weather patterns and airport safety requirements.

<span class="mw-page-title-main">Heliport</span> Airport designed for helicopter use

A heliport, sometimes termed a vertiport, is a small airport suitable for use by helicopters and various types of vertical lift aircraft. Designated heliports typically contain one or more touchdown and liftoff areas and may also have limited facilities such as fuel or hangars. In some larger towns and cities, customs facilities may also be available.

Aviation is the design, development, production, operation, and use of aircraft, especially heavier-than-air aircraft. Articles related to aviation include:

<span class="mw-page-title-main">Aerodrome</span> Location from which aircraft flight operations take place

An aerodrome or airdrome is a location from which aircraft flight operations take place, regardless of whether they involve air cargo, passengers, or neither, and regardless of whether it is for public or private use. Aerodromes include small general aviation airfields, large commercial airports, and military air bases.

The visual approach slope indicator (VASI) is a system of lights on the side of an airport runway threshold that provides visual descent guidance information during final approach. These lights may be visible from up to 8 kilometres (5.0 mi) during the day and up to 32 kilometres (20 mi) or more at night.

<span class="mw-page-title-main">Precision approach path indicator</span> Visual aid in aviation

A precision approach path indicator (PAPI) is a system of lights on the side of an airport runway threshold that provides visual descent guidance information during final approach. It is generally located on the left-hand side of the runway approximately 300 meters beyond the landing threshold of the runway.

<span class="mw-page-title-main">Airports Authority of India</span> Statutory body under Ministry of civil aviation, Govt. of India

The Airports Authority of India, or AAI, is a Statutory body under the ownership of the Ministry of Civil Aviation, Government of India. It is responsible for creating, upgrading, maintaining, and managing civil aviation infrastructure in India. It provides Communication Navigation Surveillance/Air Traffic Management (CNS/ATM) services over the Indian airspace and adjoining oceanic areas. AAI currently manages a total of 137 airports, including 34 international airports, 10 Customs Airports, 81 domestic airports, and 23 Civil enclaves at Defence airfields. AAI also has ground installations at all airports and 25 other locations to ensure the safety of aircraft operations. AAI covers all major air routes over the Indian landmass via 29 Radar installations at 11 locations along with 700 VOR/DVOR installations co-located with Distance Measuring Equipment (DME). 52 runways are provided with Instrument landing system (ILS) installations with Night Landing Facilities at most of these airports and an Automatic Message Switching System at 15 Airports.

<span class="mw-page-title-main">Airport apron</span> Area at an airport used by aircraft for parking, loading, fueling, and maintenance

The airport apron, apron, flight line, ramp, or tarmac is the area of an airport where aircraft are parked, unloaded or loaded, refueled, boarded, or maintained. Although the use of the apron is covered by regulations, such as lighting on vehicles, it is typically more accessible to users than the runway or taxiway. However, the apron is not usually open to the general public, and a permit may be required to gain access. An apron's designated areas for aircraft parking are called aircraft stands.

<span class="mw-page-title-main">Frangible bullet</span> Bullets designed to reduce ricochet risk

Frangible bullets are intended to disintegrate into tiny particles upon target impact to minimize their penetration of other objects. Small particles are slowed more rapidly by air resistance, and are less likely to cause injury or damage to persons and objects distant from the point of bullet impact.

<span class="mw-page-title-main">Airport crash tender</span> Emergency vehicle specialised in aircraft firefighting operations

An airport crash tender is a specialised fire engine designed for use in aircraft firefighting at aerodromes, airports, and military air bases.

Aviation obstruction lighting is used to enhance the visibility of structures or fixed obstacles which may conflict with the safe navigation of aircraft. Obstruction lighting is commonly installed on towers, buildings, and even fences located in areas where aircraft may be operating at low altitudes. In certain areas, some aviation regulators mandate the installation, operation, color, and/or status notification of obstruction lighting. For maximum visibility and collision-avoidance, these lighting systems commonly employ one or more high-intensity strobe or LED devices which can be seen by pilots from many miles away from the obstruction.

Rotating beacon may refer to:

<span class="mw-page-title-main">Lubin-Obora Airport</span> Airport in Lubin, Poland

<span class="mw-page-title-main">Final approach</span> Final stage in an aircrafts approach to landing

In aeronautics, the final approach is the last leg in an aircraft's approach to landing, when the aircraft is lined up with the runway and descending for landing. In aviation radio terminology, it is often shortened to "final".

<span class="mw-page-title-main">Cabo San Lucas International Airport</span> Airport in Cabo San Lucas

Cabo San Lucas International Airport is a small international airfield located 4.5 miles (7.2 km) northwest of Cabo San Lucas in Baja California Sur, Mexico.

<span class="mw-page-title-main">Alitalia Flight 404</span> 1990 aviation accident

Alitalia Flight 404 (AZ404/AZA404) was an international passenger flight scheduled to fly from Linate Airport in Milan, Italy, to Zürich Airport in Zürich, Switzerland, which crashed on 14 November 1990. The Douglas DC-9-32, operated by Alitalia, crashed into the woodlands of Weiach as it approached Zurich Airport, killing all 46 people on board.

The General Civil Aviation Authority (GCAA) is the civil aviation authority of the United Arab Emirates (UAE). Its head office is in Al Rawdah, Abu Dhabi.

Pokhara International Airport is an international airport in Pokhara, Gandaki Province, Nepal. It is located 3 km (1.9 mi) east of the old domestic airport, which it will gradually replace. The airport is Nepal's third international airport and officially began operations on 1 January 2023, with STOL-operations to Jomsom still being operated from the old airport. The airport is expected to handle up to one million passengers per year.

References

  1. Wright, Aldridge. "A Lesson in Safety". Federal Highway Administration. Archived from the original on 9 February 2019. Retrieved 6 February 2019. State Project Engineer ... was adamant that changing the old design features for ones having the newer designs was a waste of the taxpayers' money. The features were only a few months old and the probability of any one of them getting hit was very small. One day a friend of his left the roadway and hit a light pole with a rigid design. His friend was killed in the accident. After learning of the tragedy, the Project Engineer had a change of heart. He reasoned that a frangible base costing a few hundred dollars would have saved his friend's life.
  2. "NTSB Aircraft Accident Report, NTSB-AAR-72-17, 1972, Pan American World Airways, Inc., Boeing 747, N747PA, Flight 845" (PDF). 24 May 1972. Retrieved 6 February 2019. Two passengers, ..., were seriously injured by parts of the Approach Light System structure which penetrated the passenger compartment
  3. Rogers, E.T.; Ross, J.A.; Snyder, K.M. (30 August 1979). Development and test of low-impact resistant towers (PDF) (Report). FAA-AF-79-1. Retrieved 6 February 2019. A break-away fiberglass mast for use in low impact resistant (LIR) structures to support airport approach lighting systems has been developed. This design will withstand 100 mph winds (including gusts) without ice and 75 mph winds (including gusts) with a 1/2 inch radial ice load. Yet, when struck by a light airplane wing, it breaks into pieces without catastrophic damage to the wing. It was observed that impact energy needed to break the mast was in the order of 679 foot-pounds and that peak forces were in the order of 5,656 lbs.
  4. International Standards and Recommended Practices, Annex 14 (Vol. 1, section 9.9.4) to the Convention on International Civil Aviation
  5. ICAO, Aerodrome Design Manual, Part 6 - Frangibility, First Edition - 2006
  6. J.F.M. Wiggenraad, D.G. Zimcik, "Frangibility of Approach Lighting Structures at Airports", International Airport Review, Vol.5, No. 1 2001
  7. J.F.M. Wiggenraad, A. de Boer, R.H.W.M. Frijns, "Impact simulation of a frangible approach light structure by an aircraft wing section", 3rd International KRASH users' Seminar, January 8–10, 2001, Arizona State University, (also available as NLR TP 2000-618)
  8. M.H. van Houten, H. Gottschalk, C. Rooks, R. Miller, P. Tölke, "Frangible design of instrument landing system/glide slope towers", International Crashworthiness Conference, ICRASH2010, Leesburg, VA, USA, Sept. 22-24, 2010
  9. Tony L. Jones. "FRANGIBLE AND NONTOXIC AMMUNITION". Police and Security News. Archived from the original on 2009-03-18.
  10. "Frangible Ammunition". GlobalSecurity.org .
  11. Estes, Adam Clark (16 March 2019). "The Pyrex Glass Controversy That Just Won't Die". gizmodo.com. Retrieved 25 March 2019. [Dr. John C. Mauro] went on to note how soda-lime glass is tempered to improve its strength. However, that tempering process also makes the interior of glass more stressed. "So when it fractures, it breaks in a catastrophic fashion (i.e., breaking in many small pieces; so-called 'frangibility')," Mauro said. "This is in contrast to an untempered borosilicate glass, which would break into much larger pieces compared to a tempered soda-lime."
  12. Johnston, Roger G. (October 10, 1999). "Tamper-Indicating Seals for Nuclear Disarmament and Hazardous Waste Management" (PDF). Science & Global Security. Taylor and Francis. 9 (2): 93–112. doi:10.1080/08929880108426490. S2CID   55005135 . Retrieved June 6, 2019. Passive seals take a variety of forms. They can be frangible foils or films; plastic wraps; pressure-sensitive adhesive labels; "locking" bolts, crimped wires/cables, or other (theoretically) irreversible mechanical assemblies; tamper-evident packaging and security containers or enclosures that give evidence of being opened; fiber optic bundles that show changes in light transmission when cut; and other devices or materials that display irreversible damage or changes when manipulated.