Electrical equipment in hazardous areas

In electrical engineering, hazardous locations (sometimes abbreviated to HazLoc, pronounced Haz·Lōk) are defined as places where fire or explosion hazards may exist due to flammable gases, flammable liquid–produced vapors, combustible liquid–produced vapors, combustible dusts, or ignitible fibers/flyings present in the air in quantities sufficient to produce explosive or ignitible mixtures. Electrical equipment that must be installed in such classified locations should be specially designed and tested to ensure it does not initiate an explosion, due to arcing contacts or high surface temperature of equipment.

The introduction of electrical apparatus for signaling or lighting in coal mines was accompanied by electrically-initiated explosions of flammable gas and dust. Technical standards were developed to identify the features of electrical apparatus that would prevent electrical initiation of explosions due to energy or thermal effects. Several physical methods of protection are used. The apparatus may be designed to prevent entry of flammable gas or dust into the interior. The apparatus may be strong enough to contain and cool any combustion gases produced internally. Or, electrical devices may be designed so that they cannot produce a energy from a spark strong enough or temperatures high enough to ignite a specified hazardous gas.

Raytheon T-1 Jayhawk

The Raytheon T-1 Jayhawk is a twin-engined jet aircraft used by the United States Air Force for advanced pilot training. T-1A students go on to fly airlift and tanker aircraft. The T-400 is a similar version for the Japan Air Self-Defense Force.

Design and development

The T-1A Jayhawk is a medium-range, twin-engine jet trainer used in the advanced phase of Air Force [[Joint Specialized Undergraduate Pilot Training]] for students selected to fly strategic/tactical airlift or tanker aircraft. It is used also for training Air Force Combat Systems Officers in high and low level flight procedures during the advanced phase of training. It also augmented or served in lieu of the T-39 Sabreliner in the Intermediate phase of USN/USMC Student Naval Flight Officer (SNFO) training until the joint Air Force-Navy/Marine Corps training pipeline split in 2010 and now remains solely in operation with the U.S. Air Force, leaving the Navy with the Sabreliner pending its eventual replacement. The T-1 Jayhawk shares the same letter and number as the now retired T-1 SeaStar under the 1962 United States Tri-Service aircraft designation system.

McDonnell Douglas T-45 Goshawk

The McDonnell Douglas (now Boeing) T-45 Goshawk is a highly modified version of the BAE Hawk land-based training jet aircraft. Manufactured by McDonnell Douglas (now Boeing) and British Aerospace (now BAE Systems), the T-45 is used by the United States Navy as an aircraft carrier-capable trainer.

Design and development

The T-45 Goshawk is a fully carrier-capable version of the British Aerospace Hawk Mk.60. It was developed as a jet flight trainer for the United States Navy (USN) and United States Marine Corps (USMC).

The Goshawk's origins began in the mid-1970s, when the US Navy began looking for a single aircraft replacement for both its T-2 and TA-4 jet trainers. The US Navy started the VTXTS advanced trainer program in 1978. British Aerospace (BAe) and McDonnell Douglas (MDC) proposed a version of the Hawk and were awarded the T-45 contract in 1981.

The Hawk had not been designed for carrier operations and numerous modifications were required to make it suitable for use on carriers. These included improvements to the low-speed handling characteristics and a reduction in the approach speed. It was found that the aircraft was apt to stall at the low approach speed required. Modifications were designed by BAe in England; most notably a simple slat system was devised, operated by an actuator and linkage mechanism to fit into the small space available. Strakes were also added on the fuselage to improve airflow. The re-design allowed the T-45 to become carrier capable. Other changes were strengthened airframe, more robust and wider landing gear with catapult tow bar attachment and an arresting hook. It features a two-wheel nose landing gear.

4 AM

4 AM is a point in time of the 12-hour clock which corresponds to 0400 in the 24-hour clock. 4 AM or 4am may also refer to:

Books

Music

Songs

See also

3AM (Matchbox Twenty song)

"3 A.M." (written "3 am" on the album and "3 AM" on the single) is the third single and the third track from Matchbox Twenty's debut album, Yourself or Someone Like You. It topped the Canadian RPM record charts in early 1998.

Background and content

This song was written by Rob Thomas, Jay Stanley, John Leslie Goff and Brian Yale while performing together in the early 1990s band Tabitha's Secret. The lyrics are inspired by Thomas as an adolescent having to live with a mother fighting to survive cancer.

Music video

The video (directed by Gavin Bowden) features the band sitting on sides of a street next to some telephone booths. A supermarket is also shown. The video switches from color video images to black-and-white images. During the introduction and the third verse of the song, Thomas walks in the middle of the street with some construction signs and lights. During the third verse, a car stops with a bare-chested man and a woman inside. The man walks out, revealing a catheter in his chest, and is handed three cigarettes by Thomas. Finally, during the last two choruses, the band is shown playing their instruments ending with an image of Thomas standing next to the telephone booths.

9 A.M.

9 A.M. may refer to:

See also