Hot and high
Encyclopedia
In aviation
, hot and high is a condition of low air density due to high ambient temperature and high airport elevation
. Air density decreases with increasing temperature and altitude. Lower air density reduces the amount of lift
generated by the wing
s or the rotors
of an aircraft
, which may hamper an aircraft's performance and hence its ability to operate safely. The reduced density also harms the performance of the aircraft's engine
, compounding the effect. Aviators gauge air density by calculating the density altitude
.
Alternately, runway lengths may be increased to make up for reduced aircraft performance.
Auxiliary jets and rockets have rarely been used on civil aircraft due to the risk of aircraft damage and loss of control if something were to go wrong during their use. Boeing produced a JATO-powered version of its popular Boeing 727
primarily for "hot and high" operations out of Mexico City Airport (MMMX
) and La Paz, Bolivia. The boosters were located adjacent to the main landing gear at the wing root on each side of the aircraft.
s offered variants optimized for hot and high operations. Such aircraft generally offered the largest wings and/or the most powerful engines in the model lineup coupled with a small fuselage
to reduce weight. Some such aircraft include:
The marketing failure of these airplanes demonstrated that airline
s were generally unwilling to accept reduced efficiency at cruise and smaller ultimate load-carrying capacity in return for a slight performance gain at particular airports. Rather than accepting these drawbacks, it was easier for airlines to demand the construction of longer runways, operate with smaller loads as conditions dictated, or simply drop the unprofitable destinations.
Furthermore, as the second generation of jet airliners began to appear in the 1970s, some aircraft were designed to eliminate the need for a special "hot and high" variant- for instance, the Airbus A300
can perform a 15/0 takeoff, where the leading edge slats are adjusted to 15 degrees and the flaps kept retracted. This takeoff technique is only used at hot and high airports, for it enables a higher climb limit weight and improves second segment climb performance.
Most jetliner manufacturers have dropped the "hot and high" variants from their model lineups.
, where a fixed-wing aircraft
is too fast (hot) and too high above the glidepath: since the only way to increase the rate of descent is to increase speed, and the aircraft is already too fast, it is unlikely that the approach can be salvaged.
Aviation
Aviation is the design, development, production, operation, and use of aircraft, especially heavier-than-air aircraft. Aviation is derived from avis, the Latin word for bird.-History:...
, hot and high is a condition of low air density due to high ambient temperature and high airport elevation
Elevation
The elevation of a geographic location is its height above a fixed reference point, most commonly a reference geoid, a mathematical model of the Earth's sea level as an equipotential gravitational surface ....
. Air density decreases with increasing temperature and altitude. Lower air density reduces the amount of lift
Lift (force)
A fluid flowing past the surface of a body exerts a surface force on it. Lift is the component of this force that is perpendicular to the oncoming flow direction. It contrasts with the drag force, which is the component of the surface force parallel to the flow direction...
generated by the wing
Wing
A wing is an appendage with a surface that produces lift for flight or propulsion through the atmosphere, or through another gaseous or liquid fluid...
s or the rotors
Helicopter rotor
A helicopter main rotor or rotor system is a type of fan that is used to generate both the aerodynamic lift force that supports the weight of the helicopter, and thrust which counteracts aerodynamic drag in forward flight...
of an aircraft
Aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...
, which may hamper an aircraft's performance and hence its ability to operate safely. The reduced density also harms the performance of the aircraft's engine
Aircraft engine
An aircraft engine is the component of the propulsion system for an aircraft that generates mechanical power. Aircraft engines are almost always either lightweight piston engines or gas turbines...
, compounding the effect. Aviators gauge air density by calculating the density altitude
Density altitude
Density altitude is the altitude in the International Standard Atmosphere at which the air density would be equal to the actual air density at the place of observation, or, in other words, the height when measured in terms of the density of the air rather than the distance from the ground...
.
Negative effects of hot and high conditions
- Airplanes require a longer takeoff run, potentially exceeding the amount of available runway.
- Low air density hampers an aircraft's ability to climb. In some cases, an aircraft may be unable to climb rapidly enough to clear terrain surrounding a mountain airport.
- Helicopters may be forced to operate in the shaded portion of the height-velocity diagramHeight-velocity diagramThe Height-Velocity diagram or H/V curve is a graph charting the safe/unsafe flight profiles relevant to a specific helicopter. As operation outside the safe area of the chart can be fatal in the event of a power or transmission failure it is sometimes referred to as the dead man's curve or Coffin...
in order to become airborne at all. This creates the potential for an uncontrollable descent in the event of an engine failure. - Some aircraft, particularly light general aviationGeneral aviationGeneral aviation is one of the two categories of civil aviation. It refers to all flights other than military and scheduled airline and regular cargo flights, both private and commercial. General aviation flights range from gliders and powered parachutes to large, non-scheduled cargo jet flights...
airplanes and older helicopters, have service ceilingService ceilingWith respect to aircraft, a ceiling is the maximum density altitude an aircraft can reach under a set of conditions.The word ceiling can also refer to the height of the lowest obscuring cloud layer above the ground.-Service ceiling:...
s so low that they may stallStall (flight)In fluid dynamics, a stall is a reduction in the lift coefficient generated by a foil as angle of attack increases. This occurs when the critical angle of attack of the foil is exceeded...
simply trying to maintain level flight. In some cases, aircraft have landed at high-altitude airports by taking advantage of cold temperatures only to become stranded as temperatures warmed and air density decreased.
Improving hot and high performance
Some ways to increase aircraft performance in hot and high conditions include:- Reduce aircraft weight. Weight can be reduced by carrying only enough fuel to reach the destination rather than filling the tanks completely. In some cases, unnecessary equipment can be removed from the aircraft. However, in many cases, the only practical way to adequately reduce aircraft weight is to depart with a smaller passenger, cargo, or weapons load. Consequently, hot and high conditions at the originating airport may prevent a commercial aircraft from operating with a load large enough to be profitable, or may constrain the firepower that a combat aircraft can bring to bear when conducting a long-range airstrikeAirstrikeAn air strike is an attack on a specific objective by military aircraft during an offensive mission. Air strikes are commonly delivered from aircraft such as fighters, bombers, ground attack aircraft, attack helicopters, and others...
. - Increase engine power. More powerful engines can improve an airplane's acceleration and reduce its takeoff run. However, more powerful engines are generally larger and heavier and use more fuel during cruise, increasing the fuel load needed to reach the same destination. The added weight of the fuel and engines may negate the potential performance gain, and the added cost of the extra fuel may constrain the profitability of a commercial aircraft.
- Increase the size of the wings. However, larger wings weigh more and increase dragDrag (physics)In fluid dynamics, drag refers to forces which act on a solid object in the direction of the relative fluid flow velocity...
, making the aircraft slower and increasing fuel consumption during cruise. - Add high-lift deviceHigh-lift deviceIn aircraft design, high-lift devices are moving surfaces or stationary components intended to increase lift during certain flight conditions. They include common devices such as flaps and slats, as well as less common features such as leading edge extensions and blown flaps.-Purpose:Aircraft...
s to the wings. However, these devices typically add weight and mechanical complexity, increasing manufacturing and maintenance costs. Furthermore, some high-lift devices increase drag during cruise. - Utilize assisted take offAssisted take offAssisted take off is any system for helping aircraft into the air . The reason it might be needed is due to the aircraft's weight exceeding the normal maximum take off weight, insufficient power, or the available runway length may be insufficient, or a combination of all three factors...
devices, such as rockets, to increase lift and acceleration. - Inject distilled waterDistilled waterDistilled water is water that has many of its impurities removed through distillation. Distillation involves boiling the water and then condensing the steam into a clean container.-History:...
during takeoff in the engine (compressor or combustor). Evaporating water reduces the temperature, so more fuel can be added, increasing power.
Alternately, runway lengths may be increased to make up for reduced aircraft performance.
Jet or rocket assisted take off
Auxiliary rockets and/or jet engines can help a fully loaded aircraft to take off within the length of the runway. The rockets are usually one-time units that are jettisoned after takeoff. This practice was common in the 1950s and 60s, when the lower levels of thrust from military turbojets was inadequate for takeoff from shorter runways or with very heavy payloads. It is now seldom used.Auxiliary jets and rockets have rarely been used on civil aircraft due to the risk of aircraft damage and loss of control if something were to go wrong during their use. Boeing produced a JATO-powered version of its popular Boeing 727
Boeing 727
The Boeing 727 is a mid-size, narrow-body, three-engine, T-tailed commercial jet airliner, manufactured by Boeing. The Boeing 727 first flew in 1963, and for over a decade more were built per year than any other jet airliner. When production ended in 1984 a total of 1,832 aircraft had been produced...
primarily for "hot and high" operations out of Mexico City Airport (MMMX
Mexico City International Airport
Benito Juárez International Airport , in Venustiano Carranza, one of the sixteen boroughs into which Mexico's Federal District is divided, is a commercial airport that serves Mexico City, the capital of Mexico...
) and La Paz, Bolivia. The boosters were located adjacent to the main landing gear at the wing root on each side of the aircraft.
Specialized aircraft
Several manufacturers of early jet airlinerJet airliner
A jet airliner is an airliner that is powered by jet engines. This term is sometimes contracted to jetliner or jet.In contrast to today's relatively fuel-efficient, turbofan-powered air travel, first generation jet airliner travel was noisy and fuel inefficient...
s offered variants optimized for hot and high operations. Such aircraft generally offered the largest wings and/or the most powerful engines in the model lineup coupled with a small fuselage
Fuselage
The fuselage is an aircraft's main body section that holds crew and passengers or cargo. In single-engine aircraft it will usually contain an engine, although in some amphibious aircraft the single engine is mounted on a pylon attached to the fuselage which in turn is used as a floating hull...
to reduce weight. Some such aircraft include:
- The BAC One-Eleven 475BAC One-ElevenThe British Aircraft Corporation One-Eleven, also known as the BAC-111, BAC-1-11 or BAC 1-11, was a British short-range jet airliner of the 1960s and 1970s...
combined the short body of the series 400 with the more powerful engines and improved wings of the series 500. Also featured stronger landing gear for rough field operations. - The Boeing 707-220Boeing 707The Boeing 707 is a four-engine narrow-body commercial passenger jet airliner developed by Boeing in the early 1950s. Its name is most commonly pronounced as "Seven Oh Seven". The first airline to operate the 707 was Pan American World Airways, inaugurating the type's first commercial flight on...
, which was a 707-120 airframe fitted with more powerful Pratt & Whitney JT4APratt & Whitney JT4A|-See also:-External links:*...
engines, civilian versions of the military J75. The 707-220 had extremely high fuel consumption, and only 5 were built, all for Braniff International AirwaysBraniff International AirwaysBraniff International Airways was an American airline that operated from 1928 until 1982, primarily in the midwestern and southwestern U.S., South America, Panama, and in its later years also Asia and Europe...
. The 707-220 was rendered redundant by the release of the turbofanTurbofanThe turbofan is a type of airbreathing jet engine that is widely used for aircraft propulsion. A turbofan combines two types of engines, the turbo portion which is a conventional gas turbine engine, and the fan, a propeller-like ducted fan...
-powered 707-120B, which had even greater power along with much lower fuel consumption. - The Convair 880Convair 880The Convair 880 was a narrow-body jet airliner produced by the Convair division of General Dynamics. It was designed to compete with the Boeing 707 and Douglas DC-8 by being smaller and faster, a niche that failed to create demand...
. Although Convair only offered one configuration of this aircraft, it had more power and a smaller fuselage than its competitors from Boeing and Douglas. Convair essentially wagered the success of the entire 880 model line on the appeal of an aircraft optimized for hot and high operations. The wager failed; only 65 880s were sold and Convair's nascent airliner business soon collapsed. - The Lockheed L-1011-200Lockheed L-1011The Lockheed L-1011 TriStar, commonly referred to as the L-1011 or TriStar, is a medium-to-long range, widebody passenger trijet airliner. It was the third widebody airliner to enter commercial operations, following the Boeing 747 and the McDonnell Douglas DC-10. Between 1968 and 1984, Lockheed...
, which was otherwise an L-1011-100 with more powerful RB.211-524B engines. - The McDonnell Douglas DC-9-20McDonnell Douglas DC-9The McDonnell Douglas DC-9 is a twin-engine, single-aisle jet airliner. It was first manufactured in 1965 with its maiden flight later that year. The DC-9 was designed for frequent, short flights. The final DC-9 was delivered in October 1982.The DC-9 was followed in subsequent modified forms by...
, which combined the smaller fuselage of the DC-9-10 with the larger wings and more powerful engines of the DC-9-30, and was significantly outsold by both. - The McDonnell Douglas DC-10-15McDonnell Douglas DC-10The McDonnell Douglas DC-10 is a three-engine widebody jet airliner manufactured by McDonnell Douglas. The DC-10 has range for medium- to long-haul flights, capable of carrying a maximum 380 passengers. Its most distinguishing feature is the two turbofan engines mounted on underwing pylons and a...
, which combined the fuselage of the DC-10-10 with the larger engines of the DC-10-30. These were specifically designed for and sold to AeromexicoAeroméxicoAirways of Mexico, SA de CV , operating as Aeroméxico, is the flag carrier airline of Mexico based in Colonia Cuauhtémoc, Cuauhtémoc, Mexico City. It operates scheduled domestic and international services to North America, South America, Central America and the Caribbean, Europe, and Asia...
and MexicanaMexicana de AviaciónFounded in 1921, Compañía Mexicana de Aviación, S.A. de C.V. was Mexico's oldest airline, before ceasing operations on August 28, 2010. The group's closure was announced by the company's recently installed management team a short time after the group filed for Concurso Mercantil and US Chapter 15...
. Only seven were built. - The Vickers VC10Vickers VC10The Vickers VC10 is a long-range British airliner designed and built by Vickers-Armstrongs Ltd, and first flown in 1962. The airliner was designed to operate on long-distance routes with a high subsonic speed and also be capable of hot and high operations from African airports...
, which was designed to meet BOACBritish Overseas Airways CorporationThe British Overseas Airways Corporation was the British state airline from 1939 until 1946 and the long-haul British state airline from 1946 to 1974. The company started life with a merger between Imperial Airways Ltd. and British Airways Ltd...
requirements for a large airliner that could operate from short runways in the tropicsTropicsThe tropics is a region of the Earth surrounding the Equator. It is limited in latitude by the Tropic of Cancer in the northern hemisphere at approximately N and the Tropic of Capricorn in the southern hemisphere at S; these latitudes correspond to the axial tilt of the Earth...
. The plane's resulting high fuel consumption compared to the contemporary Boeing 707 prompted all other major airlines to dismiss the VC10, which would prove financially calamitous for its manufacturer, Vickers-Armstrongs.
The marketing failure of these airplanes demonstrated that airline
Airline
An airline provides air transport services for traveling passengers and freight. Airlines lease or own their aircraft with which to supply these services and may form partnerships or alliances with other airlines for mutual benefit...
s were generally unwilling to accept reduced efficiency at cruise and smaller ultimate load-carrying capacity in return for a slight performance gain at particular airports. Rather than accepting these drawbacks, it was easier for airlines to demand the construction of longer runways, operate with smaller loads as conditions dictated, or simply drop the unprofitable destinations.
Furthermore, as the second generation of jet airliners began to appear in the 1970s, some aircraft were designed to eliminate the need for a special "hot and high" variant- for instance, the Airbus A300
Airbus A300
The Airbus A300 is a short- to medium-range widebody jet airliner. Launched in 1972 as the world's first twin-engined widebody, it was the first product of Airbus Industrie, a consortium of European aerospace companies, wholly owned today by EADS...
can perform a 15/0 takeoff, where the leading edge slats are adjusted to 15 degrees and the flaps kept retracted. This takeoff technique is only used at hot and high airports, for it enables a higher climb limit weight and improves second segment climb performance.
Most jetliner manufacturers have dropped the "hot and high" variants from their model lineups.
Other uses
Less formally, hot and high can also describe a botched landing approachFinal approach (aviation)
A final approach is the last leg in an aircraft's approach to landing. In aviation radio terminology, it is often shortened to "final".In a standard airport landing pattern, which is usually used under visual meteorological conditions , aircraft turn from base leg to final within one to two miles...
, where a fixed-wing aircraft
Aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...
is too fast (hot) and too high above the glidepath: since the only way to increase the rate of descent is to increase speed, and the aircraft is already too fast, it is unlikely that the approach can be salvaged.
Hot and high airports
Notable examples of hot and high airports include:- Addis AbabaAddis AbabaAddis Ababa is the capital city of Ethiopia...
- Bole Airport - BrasíliaBrasíliaBrasília is the capital city of Brazil. The name is commonly spelled Brasilia in English. The city and its District are located in the Central-West region of the country, along a plateau known as Planalto Central. It has a population of about 2,557,000 as of the 2008 IBGE estimate, making it the...
- Brasília Airport - BogotáBogotáBogotá, Distrito Capital , from 1991 to 2000 called Santa Fé de Bogotá, is the capital, and largest city, of Colombia. It is also designated by the national constitution as the capital of the department of Cundinamarca, even though the city of Bogotá now comprises an independent Capital district...
- El Dorado AirportEl Dorado International AirportEl Dorado International Airport is an international airport located in Bogotá, Colombia. It is the largest Latin America airport in terms of cargo movements with 593,946 tons and the third in terms of passenger traffic, only behind São Paulo-Guarulhos International Airport and Mexico City's... - Denver - Denver International AirportDenver International AirportDenver International Airport , often referred to as DIA, is an airport in Denver, Colorado. By land size, at , it is the largest international airport in the United States, and the third largest international airport in the world after King Fahd International Airport and Montréal-Mirabel...
, especially from late spring to early autumn - Edwards Air Force BaseEdwards Air Force BaseEdwards Air Force Base is a United States Air Force base located on the border of Kern County, Los Angeles County, and San Bernardino County, California, in the Antelope Valley. It is southwest of the central business district of North Edwards, California and due east of Rosamond.It is named in...
- HarareHarareHarare before 1982 known as Salisbury) is the largest city and capital of Zimbabwe. It has an estimated population of 1,600,000, with 2,800,000 in its metropolitan area . Administratively, Harare is an independent city equivalent to a province. It is Zimbabwe's largest city and its...
- Harare Airport - JohannesburgJohannesburgJohannesburg also known as Jozi, Jo'burg or Egoli, is the largest city in South Africa, by population. Johannesburg is the provincial capital of Gauteng, the wealthiest province in South Africa, having the largest economy of any metropolitan region in Sub-Saharan Africa...
– OR Tambo International Airport - KabulKabulKabul , spelt Caubul in some classic literatures, is the capital and largest city of Afghanistan. It is also the capital of the Kabul Province, located in the eastern section of Afghanistan...
- Kabul Airport - La PazLa PazNuestra Señora de La Paz is the administrative capital of Bolivia, as well as the departmental capital of the La Paz Department, and the second largest city in the country after Santa Cruz de la Sierra...
- El Alto International AirportEl Alto International AirportEl Alto International Airport is an international airport located south west of La Paz, La Paz Department, Bolivia.The airport is located in the city of El Alto and has served since the first half of the 20th century, but was modernized in the late 1960s, when its runway was lengthened and a new...
(not generally a "hot" airport, as average high temperatures are never more than 15 °C (59 °F) throughout the year, but one of the world's highest commercial airports at 13325 feet (4,061.5 m)) - Las VegasLas Vegas metropolitan areaThe Las Vegas Valley is the heart of the Las Vegas-Paradise, NV MSA also known as the Las Vegas–Paradise–Henderson MSA which includes all of Clark County, Nevada, and is a metropolitan area in the southern part of the U.S. state of Nevada. The Valley is defined by the Las Vegas Valley landform, a ...
- McCarran International AirportMcCarran International AirportMcCarran International Airport is the principal commercial airport serving Las Vegas and Clark County, Nevada, United States. The airport is located five miles south of the central business district of Las Vegas, in the unincorporated area of Paradise in Clark County. It covers an area of and... - MadridMadridMadrid is the capital and largest city of Spain. The population of the city is roughly 3.3 million and the entire population of the Madrid metropolitan area is calculated to be 6.271 million. It is the third largest city in the European Union, after London and Berlin, and its metropolitan...
– Madrid-Barajas International Airport - Mexico CityMexico CityMexico City is the Federal District , capital of Mexico and seat of the federal powers of the Mexican Union. It is a federal entity within Mexico which is not part of any one of the 31 Mexican states but belongs to the federation as a whole...
– Mexico City International AirportMexico City International AirportBenito Juárez International Airport , in Venustiano Carranza, one of the sixteen boroughs into which Mexico's Federal District is divided, is a commercial airport that serves Mexico City, the capital of Mexico... - PhoenixPhoenix, ArizonaPhoenix is the capital, and largest city, of the U.S. state of Arizona, as well as the sixth most populated city in the United States. Phoenix is home to 1,445,632 people according to the official 2010 U.S. Census Bureau data...
- Phoenix Sky Harbor International AirportPhoenix Sky Harbor International AirportPhoenix Sky Harbor International Airport is a joint civil-military public airport located southeast of the central business district of the city of Phoenix, in Maricopa County, Arizona, United States...
(altitude of 1135 feet (345.9 m) is not extreme, but the area's hot desert climate gives it "hot and high" characteristics for most of the year) - QuitoQuitoSan Francisco de Quito, most often called Quito , is the capital city of Ecuador in northwestern South America. It is located in north-central Ecuador in the Guayllabamba river basin, on the eastern slopes of Pichincha, an active stratovolcano in the Andes mountains...
- Mariscal Sucre Airport - Salt Lake City - Salt Lake City International AirportSalt Lake City International AirportSalt Lake City International Airport is a major public airport in Utah. A joint civil-military facility, it is located in western Salt Lake City, approximately four miles from the central business district...
, especially from late spring to early autumn - YerevanYerevanYerevan is the capital and largest city of Armenia and one of the world's oldest continuously-inhabited cities. Situated along the Hrazdan River, Yerevan is the administrative, cultural, and industrial center of the country...
- Zvartnots International AirportZvartnots International AirportZvartnots International Airport is located near Zvartnots, west of Yerevan, the capital city of Armenia. The airport was built in 1961. It is now the busiest airport in Armenia and the Caucasus. The draftsmen of the airport included architects M. Khachikyan, A. Tarkhanyan, J. Sheqhlyan, L....