... împreună cu un prieten, istoric de aviație...
...training to fly Dash - 8-300...cabina avionului...
...Dash - 8 - 300 decolând de pe pista fabricii
...cabina simulatorului de zbor
...cu instructorul de simulator și copilotul meu (training crew)
Bombardier Dash 8
The Bombardier Dash 8 (formerly the de Havilland Canada Dash 8, sometimes abbreviated as DHC-8) is a series of twin-engined, medium range, turboprop airliners. Introduced by de Havilland Canada (DHC) in 1984, they are now produced by Bombardier Aerospace. Since 1996, the aircraft have been known as the Q Series, for "quiet". Over 900 Dash 8s of all models have been built. Bombardier forecasts a total production run of 1,192 units of all Dash8/QSeries variants through the year 2016.
Design and development
In the 1970s, de Havilland Canada had invested heavily in their Dash 7 project, creating what was essentially a larger four-engine version of their Twin Otter concentrating on excellent STOL (Short Takeoff And Landing) and short-field performance, their traditional area of expertise. Using four medium-power engines with large four-bladed propellers resulted in very low noise levels which, combined with its excellent STOL characteristics, made the Dash 7 suitable for operating from small in-city airports, a market DHC felt would be compelling. However, only a handful of air carriers employed the Dash 7 as most regional airlines were more interested in operational costs than short-field performance.
In 1980, de Havilland responded by dropping the short-field performance requirement and adapting the basic Dash 7 layout to use only two, more powerful, engines. Their favoured engine supplier, Pratt & Whitney Canada, developed the new PW100 series engines for the role, more than doubling the power from their PT6. Originally designated the PT7A-2R engine, it later became the PW120. When the Dash 8 rolled out on 19 April 1983, more than 3800 hours of testing had been accumulated over two years on five PW100 series test engines. Certification of the PW120 followed in late 1983.
Distinguishing features of the Dash 8 design are the large T-tail intended to keep the tail free of prop wash during takeoff, a very high aspect ratio wing, the elongated engine nacelles also holding the rearward-folding landing gear and the pointed nose profile. First flight was on 20 June 1983, and the airliner entered service in 1984 with NorOntair. Piedmont Airlines, formerly Henson Airlines, was the first US customer for the Dash 8 in 1984.
The Dash 8 design had better cruise performance than the Dash 7, was less expensive to operate, and much less expensive to maintain due largely to having only two engines. The Dash 8 had the lowest cost per passenger mile of any regional airliner of the era. It was a little noisier than the extremely quiet Dash 7, and could not match the superb STOL performance of its earlier DHC forebears, although still able to operate from small airports with 3,000 ft (1,000 m) runways, as against 2,200 ft (670 m) required by a fully loaded Dash 7.
April 2008, Bombardier announced the Classic versions (Series 100, 200, 300) will be out of the production line, making the Series 400 the only Dash 8 still in production. 660 Dash 8 Classic were produced, the last one was delivered to Air Nelson in May 2008.
Operational history
The Dash 8 was introduced at a particularly advantageous time; most airlines were in the process of adding new aircraft to their fleet as the airline industry expanded greatly in the 1980s. The older generation of regional airliners from the 1950s and 1960s was nearing retirement, leading to high sales figures. de Havilland Canada was unable to meet the demand with sufficient production.
In 1988, Boeing bought the company in a bid to improve production at DHC's Downsview Airport plants, as well as better position themselves to compete for a new Air Canada order for large intercontinental airliners. Air Canada was a Crown corporation at the time, and both Boeing and Airbus were competing heavily via political channels for the contract. It was eventually won by Airbus, who received an order for 34 A330 and A340 aircraft in a highly controversial move. The allegations of bribery are today known as the Airbus affair. Following their failure in the competition, Boeing immediately put de Havilland Canada up for sale. The company was eventually purchased by Bombardier in 1992. The market demand for short-haul airliners was so great that Aerospatiale of France paired with Italy's Alenia to form ATR. Their once separate efforts combined to compete directly with the Dash 8. The resulting ATR 42 was even less expensive than the Dash 8, but de Havilland Canada responded with newer models to close the gap. Other companies competed with smaller or more tailored designs, like the Saab 340 and Embraer Brasilia, but by the time these were introduced the market was already reaching saturation.
All Dash 8s delivered from the second quarter of 1996 (including all Series 400s) include the Active Noise and Vibration Suppression (ANVS) system designed to reduce cabin noise and vibration levels to nearly those of jet airliners. To emphasize their quietness, Bombardier renamed the Dash 8 models as the Q Series turboprops (Q200, Q300 and Q400).
The Dash 8-100 is no longer in production, with the last Dash 8-102 built in 2005. Production of the Q200 and Q300 will cease in May 2009.
Regional jet competition
The introduction of the regional jet altered the sales picture. Although more expensive than turboprops, airlines can operate passenger services on routes not suitable for turboprops. Turboprop aircraft have lower fuel consumption and can operate from shorter runways than regional jets, but have higher engine maintenance costs, shorter ranges and lower cruising speeds.
The market for new aircraft to replace existing turboprops once again grew in the mid-1990s, and de Havilland responded with the improved "Series 400" design.
When world oil prices drove up short-haul airfares in 2006, an increasing number of airlines that had bought regional jets began to reassess turboprop regional airliners, which use about 30% less fuel than regional jets. Although the market does not appear to be as robust as in the 1980s when the first Dash 8s were introduced, 2007 saw increased sales of the only two 40+ seat regional turboprops still in western production, Bombardier's Q400 and its competitor, the ATR series of 50-70 seat turboprops. The Q400 has a cruising speed close to that of most regional jets, and its mature engines and systems require less frequent maintenance, reducing its disadvantage.
The aircraft breaks even with about 1/3rd of its seats filled (or 1/4 with more closely spaced seats), making it particularly attractive on routes with varying passenger numbers where many seats will be empty on some flights. For example, Island Air in Hawaii calculated that the use of a 50-seat Regional Jet would break even at 45 passenger seats compared to the Q400's 35-36 seats (around 55% breakeven load factor). Most short-haul routes are less than 350 miles (500 km), so the time spent on taxiing, takeoff and landing virtually eliminates a competing jet's speed advantage. As the Q400's 414 mph (667 km/h) cruise speed approaches jet speeds, short-haul airlines can usually replace a regional jet with a Q400 without changing their gate-to-gate schedules.
Bombardier has singled out the Q400 for more aggressive marketing, launching a website centered around the aircraft. The aircraft is also being considered for a further stretched version (currently designated Q400X) to compete in the 90-seat market range.
Landing gear issues
On September 12, 2007, Bombardier recommended all Q400s with over 10,000 landings to be grounded for inspection of their landing gear after two non-fatal accidents within three days involving the landing gear of a Q400 series aircraft. Both incident aircraft were operated by Scandinavian Airlines, an early operator of the type. This affected about 60 aircraft, out of 140 Q400s in service. In all, eight Q400s had landing gear failures while landing during 2007: four in Denmark, one in Germany, one in Japan, one in Lithuania and one in South Korea; see section Notable incidents and accidents. Following an incident at Copenhagen Airport, October 27, 2007, Scandinavian Airlines' executive board decided to cease operation of the Q-400 model, primarily out of concern for the company's reputation. On March 10, 2008, SAS ordered 27 more aircraft from Bombardier in a compensation deal.
Series 300
DHC-8-300 Series
Stretched 3.43 m (11 ft) over the Series 100/200, a 50–56 passenger version that entered service in 1989. Its engines are PW123 or PW123B or PW123E, rated at 2,500 shp or 1,865 kW.
DHC-8-301
1989 variant powered by two PW123 engines
DHC-8-311
1990 variant powered by two PW123 engines
DHC-8-314
1992 variant powered by two PW123B engines
DHC-8-315
1995 variant powered by two PW123E engines
DHC-8-300A
Version of the DHC-8-300 with increased payload.
Q300
Version of the DHC-8-300 with the ANVS system.
The Bombardier Dash 8 (formerly the de Havilland Canada Dash 8, sometimes abbreviated as DHC-8) is a series of twin-engined, medium range, turboprop airliners. Introduced by de Havilland Canada (DHC) in 1984, they are now produced by Bombardier Aerospace. Since 1996, the aircraft have been known as the Q Series, for "quiet". Over 900 Dash 8s of all models have been built. Bombardier forecasts a total production run of 1,192 units of all Dash8/QSeries variants through the year 2016.
Design and development
In the 1970s, de Havilland Canada had invested heavily in their Dash 7 project, creating what was essentially a larger four-engine version of their Twin Otter concentrating on excellent STOL (Short Takeoff And Landing) and short-field performance, their traditional area of expertise. Using four medium-power engines with large four-bladed propellers resulted in very low noise levels which, combined with its excellent STOL characteristics, made the Dash 7 suitable for operating from small in-city airports, a market DHC felt would be compelling. However, only a handful of air carriers employed the Dash 7 as most regional airlines were more interested in operational costs than short-field performance.
In 1980, de Havilland responded by dropping the short-field performance requirement and adapting the basic Dash 7 layout to use only two, more powerful, engines. Their favoured engine supplier, Pratt & Whitney Canada, developed the new PW100 series engines for the role, more than doubling the power from their PT6. Originally designated the PT7A-2R engine, it later became the PW120. When the Dash 8 rolled out on 19 April 1983, more than 3800 hours of testing had been accumulated over two years on five PW100 series test engines. Certification of the PW120 followed in late 1983.
Distinguishing features of the Dash 8 design are the large T-tail intended to keep the tail free of prop wash during takeoff, a very high aspect ratio wing, the elongated engine nacelles also holding the rearward-folding landing gear and the pointed nose profile. First flight was on 20 June 1983, and the airliner entered service in 1984 with NorOntair. Piedmont Airlines, formerly Henson Airlines, was the first US customer for the Dash 8 in 1984.
The Dash 8 design had better cruise performance than the Dash 7, was less expensive to operate, and much less expensive to maintain due largely to having only two engines. The Dash 8 had the lowest cost per passenger mile of any regional airliner of the era. It was a little noisier than the extremely quiet Dash 7, and could not match the superb STOL performance of its earlier DHC forebears, although still able to operate from small airports with 3,000 ft (1,000 m) runways, as against 2,200 ft (670 m) required by a fully loaded Dash 7.
April 2008, Bombardier announced the Classic versions (Series 100, 200, 300) will be out of the production line, making the Series 400 the only Dash 8 still in production. 660 Dash 8 Classic were produced, the last one was delivered to Air Nelson in May 2008.
Operational history
The Dash 8 was introduced at a particularly advantageous time; most airlines were in the process of adding new aircraft to their fleet as the airline industry expanded greatly in the 1980s. The older generation of regional airliners from the 1950s and 1960s was nearing retirement, leading to high sales figures. de Havilland Canada was unable to meet the demand with sufficient production.
In 1988, Boeing bought the company in a bid to improve production at DHC's Downsview Airport plants, as well as better position themselves to compete for a new Air Canada order for large intercontinental airliners. Air Canada was a Crown corporation at the time, and both Boeing and Airbus were competing heavily via political channels for the contract. It was eventually won by Airbus, who received an order for 34 A330 and A340 aircraft in a highly controversial move. The allegations of bribery are today known as the Airbus affair. Following their failure in the competition, Boeing immediately put de Havilland Canada up for sale. The company was eventually purchased by Bombardier in 1992. The market demand for short-haul airliners was so great that Aerospatiale of France paired with Italy's Alenia to form ATR. Their once separate efforts combined to compete directly with the Dash 8. The resulting ATR 42 was even less expensive than the Dash 8, but de Havilland Canada responded with newer models to close the gap. Other companies competed with smaller or more tailored designs, like the Saab 340 and Embraer Brasilia, but by the time these were introduced the market was already reaching saturation.
All Dash 8s delivered from the second quarter of 1996 (including all Series 400s) include the Active Noise and Vibration Suppression (ANVS) system designed to reduce cabin noise and vibration levels to nearly those of jet airliners. To emphasize their quietness, Bombardier renamed the Dash 8 models as the Q Series turboprops (Q200, Q300 and Q400).
The Dash 8-100 is no longer in production, with the last Dash 8-102 built in 2005. Production of the Q200 and Q300 will cease in May 2009.
Regional jet competition
The introduction of the regional jet altered the sales picture. Although more expensive than turboprops, airlines can operate passenger services on routes not suitable for turboprops. Turboprop aircraft have lower fuel consumption and can operate from shorter runways than regional jets, but have higher engine maintenance costs, shorter ranges and lower cruising speeds.
The market for new aircraft to replace existing turboprops once again grew in the mid-1990s, and de Havilland responded with the improved "Series 400" design.
When world oil prices drove up short-haul airfares in 2006, an increasing number of airlines that had bought regional jets began to reassess turboprop regional airliners, which use about 30% less fuel than regional jets. Although the market does not appear to be as robust as in the 1980s when the first Dash 8s were introduced, 2007 saw increased sales of the only two 40+ seat regional turboprops still in western production, Bombardier's Q400 and its competitor, the ATR series of 50-70 seat turboprops. The Q400 has a cruising speed close to that of most regional jets, and its mature engines and systems require less frequent maintenance, reducing its disadvantage.
The aircraft breaks even with about 1/3rd of its seats filled (or 1/4 with more closely spaced seats), making it particularly attractive on routes with varying passenger numbers where many seats will be empty on some flights. For example, Island Air in Hawaii calculated that the use of a 50-seat Regional Jet would break even at 45 passenger seats compared to the Q400's 35-36 seats (around 55% breakeven load factor). Most short-haul routes are less than 350 miles (500 km), so the time spent on taxiing, takeoff and landing virtually eliminates a competing jet's speed advantage. As the Q400's 414 mph (667 km/h) cruise speed approaches jet speeds, short-haul airlines can usually replace a regional jet with a Q400 without changing their gate-to-gate schedules.
Bombardier has singled out the Q400 for more aggressive marketing, launching a website centered around the aircraft. The aircraft is also being considered for a further stretched version (currently designated Q400X) to compete in the 90-seat market range.
Landing gear issues
On September 12, 2007, Bombardier recommended all Q400s with over 10,000 landings to be grounded for inspection of their landing gear after two non-fatal accidents within three days involving the landing gear of a Q400 series aircraft. Both incident aircraft were operated by Scandinavian Airlines, an early operator of the type. This affected about 60 aircraft, out of 140 Q400s in service. In all, eight Q400s had landing gear failures while landing during 2007: four in Denmark, one in Germany, one in Japan, one in Lithuania and one in South Korea; see section Notable incidents and accidents. Following an incident at Copenhagen Airport, October 27, 2007, Scandinavian Airlines' executive board decided to cease operation of the Q-400 model, primarily out of concern for the company's reputation. On March 10, 2008, SAS ordered 27 more aircraft from Bombardier in a compensation deal.
Series 300
DHC-8-300 Series
Stretched 3.43 m (11 ft) over the Series 100/200, a 50–56 passenger version that entered service in 1989. Its engines are PW123 or PW123B or PW123E, rated at 2,500 shp or 1,865 kW.
DHC-8-301
1989 variant powered by two PW123 engines
DHC-8-311
1990 variant powered by two PW123 engines
DHC-8-314
1992 variant powered by two PW123B engines
DHC-8-315
1995 variant powered by two PW123E engines
DHC-8-300A
Version of the DHC-8-300 with increased payload.
Q300
Version of the DHC-8-300 with the ANVS system.
*****************************
...TORONTO văzut din CN TOWER...
...CN Tower
...localizare CN Tower
...restaurantul rotitor
...și o parte dintre noi (piloți Dash-8-300 ai Companiei DAC AIR), ... servind prânzul în Restaurantul Rotitor
CN Tower
The CN Tower, located in downtown Toronto, Ontario, Canada, is a communications and tourist tower standing 553.33 metres (1,815.39 ft) tall. It surpassed the height of the Ostankino Tower while still under construction in 1975, becoming the tallest free-standing structure on land in the world. On September 12, 2007, after holding the record for 31 years, the CN Tower was surpassed in height by the still-under-construction Burj Dubai. It remains the tallest free-standing structure in the Americas and the signature icon of Toronto's skyline, attracting more than two million international visitors annually.
CN originally referred to Canadian National, the railway company that built the tower. Following the railway's decision to divest non-core freight railway assets, prior to the company's privatization in 1995 it transferred the tower to the Canada Lands Company, a federal Crown corporation responsible for real estate development. Since local residents wished to retain the name CN Tower, the abbreviation is now said to expand to Canada's National Tower rather than the original Canadian National Tower; however, neither of these are commonly used.
In 1995, the CN Tower was declared one of the modern Seven Wonders of the World by the American Society of Civil Engineers. It also belongs to the World Federation of Great Towers.
History
The concept of the CN Tower originated from a 1968 Canadian National Railway desire to build a large TV and radio communication platform to serve the Toronto area, as well as demonstrate the strength of Canadian industry and CN in particular. These plans evolved over the next few years, and the project became official in 1972. The tower would have been part of Metro Centre (see CityPlace), a large development south of Front Street on the Railway Lands, a large railway switching yard that was being made redundant by newer yards outside the city. Key project team members were NCK Engineering as structural engineer; John Andrews Architects; Webb, Zerafa, Menkes, Housden Architects; Foundation Building Construction; and Canron (Eastern Structural Division).
At the time, Toronto was a boom town, and the late 1960s and early 1970s had seen the construction of numerous large skyscrapers in the downtown core. This made broadcasting into the downtown area very difficult due to reflections off the buildings. The only solution would be to raise the antennas above the buildings, demanding a tower over 300 metres (984 ft) tall. Additionally, at the time, most data communications took place over point-to-point microwave links, whose dish antenna covered the roofs of large buildings. As each new skyscraper was added to the downtown, former line-of-sight links were no longer possible. CN intended to rent "hub" space for microwave links, visible from almost any building in the Toronto area. The CN Tower can be seen from at least as far away as Gamble Road in Richmond Hill, Ontario, approximately 30 kilometres (19 mi) to the north, and from several points on the south shore of Lake Ontario, 48 kilometres (30 mi) to the south.
The original plan for the tower envisioned a tripod consisting of three independent cylindrical "pillars" linked at various heights by structural bridges. Had it been built, this design would have been considerably shorter, with the metal antenna located roughly where the concrete section between the main level and the Sky Pod lies today. As the design effort continued, it evolved into the current design with a single continuous hexagonal core to the Sky Pod, with three support legs blended into the hexagon below the main level, forming a large Y-shape structure at the ground level.
The idea for the main level in its current form evolved around this time, but the Sky Pod was not part of the plans until some time later. One engineer in particular felt that visitors would feel the higher observation deck would be worth paying extra for, and the costs in terms of construction were not prohibitive. It was also some time around this point that it was realized that the tower could become the world's tallest structure, and plans were changed to incorporate subtle modifications throughout the structure to this end.
Construction
Construction on the CN Tower began on February 6, 1973 with massive excavations at the tower base for the foundation. By the time the foundation was complete, 56,000 tonnes (61,729 short tons) of dirt and shale were removed to a depth of 15 metres (49.2 ft) in the centre, and a base incorporating 7,000 cubic metres (9,156 cu yd) of concrete with 450 tonnes (496 short tons) of rebar and 36 tonnes (40 short tons) of steel cable had been built to a thickness of 6.7 metres (22 ft). This portion of the construction was fairly rapid, with only four months needed between the start and the foundation being ready for construction on top.
To build the main support pillar, a hydraulically-raised slipform was built at the base. This was a fairly impressive engineering feat on its own, consisting of a large metal platform that raised itself on jacks at about 6 metres (19.7 ft) per day as the concrete below set. Concrete was poured continuously by a team of 1,532 people until February 22, 1974, during which it had already become the tallest structure in Canada, surpassing the recently built Inco Superstack, which was built using similar methods. In total, the tower contains 40,500 cubic metres (52,972 cu yd) of concrete, all of which was mixed on-site in order to ensure batch consistency. Through the pour, the vertical accuracy of the tower was maintained by comparing the slip form's location to massive plumb-bobs hanging from it, observed by small telescopes from the ground. Over the height of the tower, it varies from true vertical accuracy by only 29 millimetres (1.1 in).
In August 1974, construction of the main level commenced. Using 45 hydraulic jacks attached to cables strung from a temporary steel crown anchored to the top of the tower, twelve giant steel and wooden bracket forms were slowly raised, ultimately taking about a week to crawl up to their final position. These forms were used to create the brackets that support the main level, as well as a base for the construction of the main level itself. The Sky Pod was built of concrete poured into a wooden frame attached to rebar at the lower level deck, and then reinforced with a large steel compression band around the outside.
The antenna was originally to be raised by crane as well, but during construction the Sikorsky S-64 Skycrane helicopter became available when the United States Army sold off theirs to civilian operators. The helicopter, named "Olga", was first used to remove the crane, and then flew the antenna up in 36 sections. The flights of the antenna pieces were a minor tourist attraction of their own, and the schedule was printed in the local newspapers. Use of the helicopter saved months of construction time, with this phase taking only three and a half weeks instead of the planned six months. The tower was topped off on April 2, 1975 after 26 months of construction, officially capturing the height record from Moscow's Ostankino Tower, and bringing the total mass to 118,000 tonnes (130,073 tons).
Two years into the construction, plans for Metro Centre were scrapped, leaving the tower isolated on the Railway Lands in what was then a largely abandoned light-industrial space. This caused serious problems for tourists to access the tower. Ned Baldwin, project architect with John Andrews, wrote at the time that "All of the logic which dictated the design of the lower accommodation has been upset," and that "Under such ludicrous circumstances Canadian National would hardly have chosen this location to build."
Opening
The CN Tower opened to the public on June 26, 1976, although the official opening date was October 1. The construction costs of approximately CDN$63 million ($330 million in 2005) were repaid in fifteen years. Canadian National Railway sold the tower prior to taking the company public in 1995, when they decided to divest themselves of all operations not directly related to their core freight shipping businesses.
As the area around the tower was developed, particularly with the introduction of the Metro Toronto Convention Centre and Rogers Centre (known as the SkyDome before 2005), the former railway "wasteland" disappeared and the tower became the centre of a newly developing entertainment area. Access was greatly improved with the construction of the SkyWalk in 1989, which connected the tower and SkyDome to the nearby railway and subway station, Union Station. By the mid-1990s, it was the centre of a thriving tourist district. The entire area continues to be an area of intense building, notably a boom in condominium construction in the 2000s.
From 1997 to January 2004, TrizecHahn Corporation managed the building and instituted several expansion projects including a $26 million entertainment expansion and revitalization that included the addition of two new elevators (to a total of six) and the relocation of the staircase from the north side leg to inside the core of the building, a conversion that also added nine stairs to the climb.
Structure
The CN Tower consists of several substructures. The main portion of the tower is a hollow concrete hexagonal pillar containing the six elevators, stairwells, and power and plumbing connections. On top of this is a 102 metres (334.6 ft) metal broadcast antenna, carrying TV and radio signals. There are two visitor areas: the main deck level (formerly known as SkyPod) located at 346 metres (1,135 ft), and the higher Sky Pod (formerly known as "Space Deck) at 446.5 metres (1,465 ft), just below the metal antenna. The hexagonal shape can be seen between the two areas; however, below the main deck, three large supporting legs give the tower the appearance of a large tripod.
The main level is seven stories, some of which are open to the public. Below the public areas — at 338 metres (1,108.9 ft) — is a large white donut-shaped radome containing the structure's microwave receivers. The glass floor and outdoor observation deck are at 342 metres (1,122.0 ft). The glass floor has an area of 24 square metres (258 sq ft) and can withstand a pressure of 4,100 kilopascals (595 psi). The floor's thermal glass units are 64 millimetres (2.5 in) thick, consisting of a pane of 25-millimetre (1.0 in) laminated glass, 25 millimetres (1.0 in) airspace and a pane of 13-millimetre (0.5 in) laminated glass. Some people experience acrophobia when standing on the glass floor and looking down at the ground 342 metres (1,122.0 ft) below. In 2008, one elevator was upgraded to add a glass floor panel, believed to have the highest vertical rise of any elevator equipped with this feature. The Horizons Cafe and the lookout level are at 346 metres (1,135.2 ft). The 360 Restaurant, a revolving restaurant that completes a full rotation once every 72 minutes, is at 351 metres (1,151.6 ft). When the tower first opened, it also featured a disco named Sparkles, billed as the highest disco and dance floor in the world.
The Sky Pod is the second highest public observation deck in the world, surpassed only by the Shanghai World Financial Center. On a clear day, it is possible to see 100 to 120 kilometres (62–75 mi) away, to the city of Rochester across Lake Ontario in the United States, the mist rising from Niagara Falls, or the shores of Lake Simcoe.[citation needed]
A metal staircase reaches the main deck level after 1,776 steps, and the Sky Pod 100 metres above after 2,579 steps; it is the tallest metal staircase on Earth. These stairs are intended for emergency use only and are not open to the public, except for three times per year for charity stair-climb events. The average climber takes approximately 30 minutes to climb to the base of the radome, but the fastest climb on record is 7 minutes and 52 seconds in 1989 by Brendan Keenoy, an Ontario Provincial Police Officer. In 2002, Canadian Olympian and Paralympic champion Jeff Adams climbed the stairs of the tower in a specially designed wheelchair.
Falling ice danger
A freezing rain storm on March 2, 2007 resulted in a layer of ice several centimetres thick forming on the side of the tower and other downtown buildings. The sun thawed the ice, and winds of up to 90 kilometres per hour (56 mph) blew some of it away from the structure. There were fears that cars and windows of nearby buildings would be smashed by large chunks of ice. In response, police closed some streets surrounding the tower. During morning rush hour on March 5, police expanded the area of closed streets to include the Gardiner Expressway 310 metres (1,017 ft) away from the tower, as increased winds blew the ice farther away, as far north as King Street, 490 metres (1,608 ft) away, where a taxicab window was shattered.
On March 6, the Gardiner Expressway was reopened after winds died down. It was the first time such an event had posed a threat to public safety.
Safety features
In August 2000, a fire broke out at the Ostankino Tower in Moscow, killing several people and causing extensive damage. The fire was blamed on poor maintenance and outdated equipment. The failure of the fire-suppression systems and the lack of proper equipment for firefighters allowed the fire to destroy most of the interior and spark fears the tower might even collapse.
The Ostankino Tower was completed only 9 years before the CN Tower and is only 13 metres shorter. The two towers also hold the same prodigious level of national pride in their respective countries. The parallels between the towers led to some concern that the CN Tower could be at risk of a similar tragedy. However, Canadian officials subsequently stated that it is "highly unlikely" that a similar disaster could occur at the CN Tower as it has important safeguards that were not present in the Ostankino Tower. Specifically, officials cited:
the fireproof building materials used in the tower's construction,
frequent and stringent safety inspections,
an extensive sprinkler system,
a 24-hour emergency monitoring operation,
two 15,000-imperial gallon water reservoirs at the top, which are automatically replenished,
a fire hose at the base of the structure capable of sending 600 imperial gallons a minute to any location in the tower,
a ban on gas appliances anywhere in the tower,
an elevator that can be used during a fire as it runs up the outside of the building and can be powered by three emergency generators at the base of the structure (unlike the elevator at the Ostankino tower, which seriously malfunctioned).
Officials also noted that the CN Tower has an excellent safety record and that there has never been an accidental fire in the tower since it was opened in 1976. Moreover, other tall structures built between 1967–1976, such as the Sears Tower, the World Trade Center (excluding the terrorist attacks), the Aon Center and John Hancock Center also have excellent safety records, which suggests that the Ostankino Tower was a rare safety failure and the likelihood of similar events occurring at other tall structures is extremely low.
The CN Tower, located in downtown Toronto, Ontario, Canada, is a communications and tourist tower standing 553.33 metres (1,815.39 ft) tall. It surpassed the height of the Ostankino Tower while still under construction in 1975, becoming the tallest free-standing structure on land in the world. On September 12, 2007, after holding the record for 31 years, the CN Tower was surpassed in height by the still-under-construction Burj Dubai. It remains the tallest free-standing structure in the Americas and the signature icon of Toronto's skyline, attracting more than two million international visitors annually.
CN originally referred to Canadian National, the railway company that built the tower. Following the railway's decision to divest non-core freight railway assets, prior to the company's privatization in 1995 it transferred the tower to the Canada Lands Company, a federal Crown corporation responsible for real estate development. Since local residents wished to retain the name CN Tower, the abbreviation is now said to expand to Canada's National Tower rather than the original Canadian National Tower; however, neither of these are commonly used.
In 1995, the CN Tower was declared one of the modern Seven Wonders of the World by the American Society of Civil Engineers. It also belongs to the World Federation of Great Towers.
History
The concept of the CN Tower originated from a 1968 Canadian National Railway desire to build a large TV and radio communication platform to serve the Toronto area, as well as demonstrate the strength of Canadian industry and CN in particular. These plans evolved over the next few years, and the project became official in 1972. The tower would have been part of Metro Centre (see CityPlace), a large development south of Front Street on the Railway Lands, a large railway switching yard that was being made redundant by newer yards outside the city. Key project team members were NCK Engineering as structural engineer; John Andrews Architects; Webb, Zerafa, Menkes, Housden Architects; Foundation Building Construction; and Canron (Eastern Structural Division).
At the time, Toronto was a boom town, and the late 1960s and early 1970s had seen the construction of numerous large skyscrapers in the downtown core. This made broadcasting into the downtown area very difficult due to reflections off the buildings. The only solution would be to raise the antennas above the buildings, demanding a tower over 300 metres (984 ft) tall. Additionally, at the time, most data communications took place over point-to-point microwave links, whose dish antenna covered the roofs of large buildings. As each new skyscraper was added to the downtown, former line-of-sight links were no longer possible. CN intended to rent "hub" space for microwave links, visible from almost any building in the Toronto area. The CN Tower can be seen from at least as far away as Gamble Road in Richmond Hill, Ontario, approximately 30 kilometres (19 mi) to the north, and from several points on the south shore of Lake Ontario, 48 kilometres (30 mi) to the south.
The original plan for the tower envisioned a tripod consisting of three independent cylindrical "pillars" linked at various heights by structural bridges. Had it been built, this design would have been considerably shorter, with the metal antenna located roughly where the concrete section between the main level and the Sky Pod lies today. As the design effort continued, it evolved into the current design with a single continuous hexagonal core to the Sky Pod, with three support legs blended into the hexagon below the main level, forming a large Y-shape structure at the ground level.
The idea for the main level in its current form evolved around this time, but the Sky Pod was not part of the plans until some time later. One engineer in particular felt that visitors would feel the higher observation deck would be worth paying extra for, and the costs in terms of construction were not prohibitive. It was also some time around this point that it was realized that the tower could become the world's tallest structure, and plans were changed to incorporate subtle modifications throughout the structure to this end.
Construction
Construction on the CN Tower began on February 6, 1973 with massive excavations at the tower base for the foundation. By the time the foundation was complete, 56,000 tonnes (61,729 short tons) of dirt and shale were removed to a depth of 15 metres (49.2 ft) in the centre, and a base incorporating 7,000 cubic metres (9,156 cu yd) of concrete with 450 tonnes (496 short tons) of rebar and 36 tonnes (40 short tons) of steel cable had been built to a thickness of 6.7 metres (22 ft). This portion of the construction was fairly rapid, with only four months needed between the start and the foundation being ready for construction on top.
To build the main support pillar, a hydraulically-raised slipform was built at the base. This was a fairly impressive engineering feat on its own, consisting of a large metal platform that raised itself on jacks at about 6 metres (19.7 ft) per day as the concrete below set. Concrete was poured continuously by a team of 1,532 people until February 22, 1974, during which it had already become the tallest structure in Canada, surpassing the recently built Inco Superstack, which was built using similar methods. In total, the tower contains 40,500 cubic metres (52,972 cu yd) of concrete, all of which was mixed on-site in order to ensure batch consistency. Through the pour, the vertical accuracy of the tower was maintained by comparing the slip form's location to massive plumb-bobs hanging from it, observed by small telescopes from the ground. Over the height of the tower, it varies from true vertical accuracy by only 29 millimetres (1.1 in).
In August 1974, construction of the main level commenced. Using 45 hydraulic jacks attached to cables strung from a temporary steel crown anchored to the top of the tower, twelve giant steel and wooden bracket forms were slowly raised, ultimately taking about a week to crawl up to their final position. These forms were used to create the brackets that support the main level, as well as a base for the construction of the main level itself. The Sky Pod was built of concrete poured into a wooden frame attached to rebar at the lower level deck, and then reinforced with a large steel compression band around the outside.
The antenna was originally to be raised by crane as well, but during construction the Sikorsky S-64 Skycrane helicopter became available when the United States Army sold off theirs to civilian operators. The helicopter, named "Olga", was first used to remove the crane, and then flew the antenna up in 36 sections. The flights of the antenna pieces were a minor tourist attraction of their own, and the schedule was printed in the local newspapers. Use of the helicopter saved months of construction time, with this phase taking only three and a half weeks instead of the planned six months. The tower was topped off on April 2, 1975 after 26 months of construction, officially capturing the height record from Moscow's Ostankino Tower, and bringing the total mass to 118,000 tonnes (130,073 tons).
Two years into the construction, plans for Metro Centre were scrapped, leaving the tower isolated on the Railway Lands in what was then a largely abandoned light-industrial space. This caused serious problems for tourists to access the tower. Ned Baldwin, project architect with John Andrews, wrote at the time that "All of the logic which dictated the design of the lower accommodation has been upset," and that "Under such ludicrous circumstances Canadian National would hardly have chosen this location to build."
Opening
The CN Tower opened to the public on June 26, 1976, although the official opening date was October 1. The construction costs of approximately CDN$63 million ($330 million in 2005) were repaid in fifteen years. Canadian National Railway sold the tower prior to taking the company public in 1995, when they decided to divest themselves of all operations not directly related to their core freight shipping businesses.
As the area around the tower was developed, particularly with the introduction of the Metro Toronto Convention Centre and Rogers Centre (known as the SkyDome before 2005), the former railway "wasteland" disappeared and the tower became the centre of a newly developing entertainment area. Access was greatly improved with the construction of the SkyWalk in 1989, which connected the tower and SkyDome to the nearby railway and subway station, Union Station. By the mid-1990s, it was the centre of a thriving tourist district. The entire area continues to be an area of intense building, notably a boom in condominium construction in the 2000s.
From 1997 to January 2004, TrizecHahn Corporation managed the building and instituted several expansion projects including a $26 million entertainment expansion and revitalization that included the addition of two new elevators (to a total of six) and the relocation of the staircase from the north side leg to inside the core of the building, a conversion that also added nine stairs to the climb.
Structure
The CN Tower consists of several substructures. The main portion of the tower is a hollow concrete hexagonal pillar containing the six elevators, stairwells, and power and plumbing connections. On top of this is a 102 metres (334.6 ft) metal broadcast antenna, carrying TV and radio signals. There are two visitor areas: the main deck level (formerly known as SkyPod) located at 346 metres (1,135 ft), and the higher Sky Pod (formerly known as "Space Deck) at 446.5 metres (1,465 ft), just below the metal antenna. The hexagonal shape can be seen between the two areas; however, below the main deck, three large supporting legs give the tower the appearance of a large tripod.
The main level is seven stories, some of which are open to the public. Below the public areas — at 338 metres (1,108.9 ft) — is a large white donut-shaped radome containing the structure's microwave receivers. The glass floor and outdoor observation deck are at 342 metres (1,122.0 ft). The glass floor has an area of 24 square metres (258 sq ft) and can withstand a pressure of 4,100 kilopascals (595 psi). The floor's thermal glass units are 64 millimetres (2.5 in) thick, consisting of a pane of 25-millimetre (1.0 in) laminated glass, 25 millimetres (1.0 in) airspace and a pane of 13-millimetre (0.5 in) laminated glass. Some people experience acrophobia when standing on the glass floor and looking down at the ground 342 metres (1,122.0 ft) below. In 2008, one elevator was upgraded to add a glass floor panel, believed to have the highest vertical rise of any elevator equipped with this feature. The Horizons Cafe and the lookout level are at 346 metres (1,135.2 ft). The 360 Restaurant, a revolving restaurant that completes a full rotation once every 72 minutes, is at 351 metres (1,151.6 ft). When the tower first opened, it also featured a disco named Sparkles, billed as the highest disco and dance floor in the world.
The Sky Pod is the second highest public observation deck in the world, surpassed only by the Shanghai World Financial Center. On a clear day, it is possible to see 100 to 120 kilometres (62–75 mi) away, to the city of Rochester across Lake Ontario in the United States, the mist rising from Niagara Falls, or the shores of Lake Simcoe.[citation needed]
A metal staircase reaches the main deck level after 1,776 steps, and the Sky Pod 100 metres above after 2,579 steps; it is the tallest metal staircase on Earth. These stairs are intended for emergency use only and are not open to the public, except for three times per year for charity stair-climb events. The average climber takes approximately 30 minutes to climb to the base of the radome, but the fastest climb on record is 7 minutes and 52 seconds in 1989 by Brendan Keenoy, an Ontario Provincial Police Officer. In 2002, Canadian Olympian and Paralympic champion Jeff Adams climbed the stairs of the tower in a specially designed wheelchair.
Falling ice danger
A freezing rain storm on March 2, 2007 resulted in a layer of ice several centimetres thick forming on the side of the tower and other downtown buildings. The sun thawed the ice, and winds of up to 90 kilometres per hour (56 mph) blew some of it away from the structure. There were fears that cars and windows of nearby buildings would be smashed by large chunks of ice. In response, police closed some streets surrounding the tower. During morning rush hour on March 5, police expanded the area of closed streets to include the Gardiner Expressway 310 metres (1,017 ft) away from the tower, as increased winds blew the ice farther away, as far north as King Street, 490 metres (1,608 ft) away, where a taxicab window was shattered.
On March 6, the Gardiner Expressway was reopened after winds died down. It was the first time such an event had posed a threat to public safety.
Safety features
In August 2000, a fire broke out at the Ostankino Tower in Moscow, killing several people and causing extensive damage. The fire was blamed on poor maintenance and outdated equipment. The failure of the fire-suppression systems and the lack of proper equipment for firefighters allowed the fire to destroy most of the interior and spark fears the tower might even collapse.
The Ostankino Tower was completed only 9 years before the CN Tower and is only 13 metres shorter. The two towers also hold the same prodigious level of national pride in their respective countries. The parallels between the towers led to some concern that the CN Tower could be at risk of a similar tragedy. However, Canadian officials subsequently stated that it is "highly unlikely" that a similar disaster could occur at the CN Tower as it has important safeguards that were not present in the Ostankino Tower. Specifically, officials cited:
the fireproof building materials used in the tower's construction,
frequent and stringent safety inspections,
an extensive sprinkler system,
a 24-hour emergency monitoring operation,
two 15,000-imperial gallon water reservoirs at the top, which are automatically replenished,
a fire hose at the base of the structure capable of sending 600 imperial gallons a minute to any location in the tower,
a ban on gas appliances anywhere in the tower,
an elevator that can be used during a fire as it runs up the outside of the building and can be powered by three emergency generators at the base of the structure (unlike the elevator at the Ostankino tower, which seriously malfunctioned).
Officials also noted that the CN Tower has an excellent safety record and that there has never been an accidental fire in the tower since it was opened in 1976. Moreover, other tall structures built between 1967–1976, such as the Sears Tower, the World Trade Center (excluding the terrorist attacks), the Aon Center and John Hancock Center also have excellent safety records, which suggests that the Ostankino Tower was a rare safety failure and the likelihood of similar events occurring at other tall structures is extremely low.
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