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Takeoff and landing
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Aircraft have different ways to take off and land. Conventional airplanes accelerate along the ground until reaching a speed that is sufficient for the airplane to take off and climb at a safe speed. Some airplanes can take off at low speed, this being a short takeoff. Some aircraft such as helicopters and Harrier jump jets can take off and land vertically. Rockets also usually take off vertically, but some designs can land horizontally.

Takeoff

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Main article: Takeoff
Takeoff of the Shuttle Carrier Aircraft carrying the Space Shuttle Enterprise

Takeoff is the phase of flight in which an aircraft goes through a transition from moving along the ground (taxiing) to flying in the air, usually starting on a runway. For balloons, helicopters and some specialized fixed-wing aircraft (VTOL aircraft such as the Harrier), no runway is needed. Takeoff is the opposite of landing.

Landing

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Main article: Landing
A mute swan alighting. Note the ruffled feathers on top of the wings indicate that the swan is flying at the stalling speed. The extended and splayed feathers act as lift augmenters in the same way as an aircraft's slats and flaps.

Landing is the last part of a flight, where a flying aircraft or spacecraft (or animals) returns to the ground. When the flying object returns to water, the process is called alighting, although it is commonly called "landing" and "touchdown" as well. A normal aircraft flight would include several parts of flight including taxi, takeoff, climb, cruise, descent and landing.

Horizontal takeoff and landing

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Aircraft

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Conventional takeoff and landing (CTOL)

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Main article: CTOL

CTOL is the process whereby conventional fixed-wing aircraft (such as passenger aircraft) take off and land, involving the use of runways.

Reduced takeoff and landing (RTOL)

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RTOL aircraft require shorter runways than conventional types, typically 3,500 feet (1,100 m) to 4,500 feet (1,400 m).[1][2]

Short takeoff and landing (STOL)

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Main article: STOL
An unusual landing; a Piper J3C-65 Cub lands on a trailer as part of an airshow.

STOL is an acronym for short take-off and landing, aircraft with very short runway requirements, typically between 2,000 feet (610 m) to 3,500 feet (1,100 m).[2]

Catapult launch and arrested recovery (CATOBAR)

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Main article: CATOBAR

CATOBAR (catapult assisted takeoff but arrested recovery) is a system used for the launch and recovery of aircraft from the deck of an aircraft carrier. Under this technique, aircraft are launched using a catapult and land on the ship (the recovery phase) using arrestor wires.

Although this system is more costly than alternative methods, it provides greater flexibility in carrier operations, since it allows the vessel to support conventional aircraft. Alternate methods of launch and recovery can only use aircraft with STOVL or STOBAR capability.

Short Take Off But Arrested Recovery (STOBAR)

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Main article: STOBAR

STOBAR (Short Take Off But Arrested Recovery) is a system used for the launch and recovery of aircraft from the deck of an aircraft carrier, combining elements of both STOVL (Short Take-Off and Vertical Landing) and CATOBAR (Catapult Assisted Take-Off But Arrested Recovery).

Spacecraft (HTHL)

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Horizontal takeoff, horizontal landing (HTHL) — is the mode of operation for the first private commercial spaceplane, the two-stage-to-space Scaled Composites Tier One from the Ansari X-Prize SpaceShipOne/WhiteKnightOne combination. It is also used for the upcoming Tier 1b SpaceShipTwo/WhiteKnightTwo combination. A prominent example of its use was the North American X-15 program. In these examples the space craft are carried to altitude on a "mother ship" before launch. The failed proposals for NASA Space Shuttle replacements, Rockwell X-30 NASP used this mode of operation but were conceived as single stage to orbit.

The Lynx rocketplane was a suborbital HTHL spaceplane developed by XCOR Aerospace that was slated to begin atmospheric flight testing in late 2011.[3] However, after numerous delays, XCOR Aerospace went bankrupt in 2017 without finishing a prototype.[4]

Reaction Engines Skylon, a design descendant of the 1980s British HOTOL ("Horizontal Take-Off and Landing") design project, is an HTHL spaceplane currently in the early stages of development in the United Kingdom.[5]

Both the Lynx rocketplane and SpaceShipTwo have been proffered to NASA to carry suborbital research payloads in response to NASA's suborbital reusable launch vehicle (sRLV) solicitation under the NASA Flight Operations Program.[6]

An early example was the 1960s Northrop HL-10 atmospheric test aircraft where the HL stands for "Horizontal Lander".[7]

Vertical takeoff and landing

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Different terms are used for takeoff and landing depending on the source of thrust used. VTVL uses rockets, whereas VTOL uses air, propelled via some kind of rotor system.

Aircraft (VTOL)

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Main article: VTOL

Vertical Take-Off and Landing (VTOL) aircraft includes fixed-wing aircraft that can hover, take off and land vertically as well as helicopters and other aircraft with powered rotors, such as tiltrotors.[8][9][10][11] The terminology for spacecraft and rockets is VTVL (vertical takeoff with vertical landing).[12] Some VTOL aircraft can operate in other modes as well, such as CTOL (conventional take-off and landing), STOL (short take-off and landing), and/or STOVL (short take-off and vertical landing). Others, such as some helicopters, can only operate by VTOL, due to the aircraft lacking landing gear that can handle horizontal motion. VTOL is a subset of V/STOL (vertical and/or short take-off and landing).

Besides the ubiquitous helicopter, there are currently two types of VTOL aircraft in military service: craft using a tiltrotor, such as the Bell Boeing V-22 Osprey, and aircraft using directed jet thrust such as the Harrier family. In the civilian sector currently only helicopters are in general use (some other types of commercial VTOL aircraft have been proposed and are under development as of 2017).

Rocket (VTVL)

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Main article: VTVL

Vertical takeoff, vertical landing (VTVL) is a form of takeoff and landing for rockets. Multiple VTVL craft have flown. The most widely known and commercially successful VTVL rocket is SpaceX's Falcon 9 first stage.

VTVL technologies were developed substantially with small rockets after 2000, in part due to incentive prize competitions like the Lunar Lander Challenge. Successful small VTVL rockets were developed by Masten Space Systems, Armadillo Aerospace, and others.

Vertical takeoff and horizontal landing

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Aircraft (VTOHL)

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In aviation the term VTOHL ("Vertical Take-Off and Horizontal Landing") as well as several VTOHL aviation-specific subtypes: VTOCL, VTOSL, VTOBAR exist.

Zero-length launch system

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Main article: Zero-length launch

The zero-length launch system or zero-length take-off system (ZLL, ZLTO, ZEL, ZELL) was a system whereby jet fighters and attack aircraft were intended to be placed upon rockets attached to mobile launch platforms. Most zero-length launch experiments took place in the 1950s, during the Cold War.

Spacecraft (VTHL)

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Vertical takeoff, horizontal landing (VTHL) is the mode of operation for all current and formerly operational orbital spaceplanes, such as the Boeing X-37, the NASA Space Shuttle, the 1988 Soviet Buran space shuttle, and the PRC Reusable experimental spacecraft/Shenlong. For launch vehicles an advantage of VTHL over HTHL is that the wing can be smaller, since it only has to carry the landing weight of the vehicle, rather than the takeoff weight.[13]

There have been several VTHL proposals that never flew, including the circa-1960 USAF Boeing X-20 Dyna-Soar project, NASA Space Shuttle proposed replacements, Lockheed Martin X-33, and VentureStar. The 1990s NASA concept spaceplane, the HL-20 Personnel Launch System (HL stands for "Horizontal Lander"), was VTHL, as was a circa-2003 derivative of the HL-20, the Orbital Space Plane concept.

As of March 2011, two VTHL commercial spaceplanes were in various stages of proposal/development, both successors to the HL-20 design. The Sierra Nevada Corporation Dream Chaser follows the outer mold line of the earlier HL-20. The circa-2011 proposed Orbital Sciences Corporation Prometheus was a blended lifting body spaceplane that followed the outer mold line of the circa-2003 Orbital Space Plane, itself a derivative of the HL-20; however, Prometheus did not receive any NASA contracts and Orbital has announced they will not pursue further development.[14]

German Aerospace Center studied reusable VTHL Liquid Fly-back Boosters from 1999. Design was intended to replace Ariane 5 solid rocket boosters.[15] The U.S. government-funded, US$250,000,000, Reusable Booster System program, initiated by the USAF in 2010,[16] had specified a high-level requirement that the design be VTHL,[17] but the funding was discontinued after 2012.[18]

In 2017 DARPA selected a VTHL design for XS-1.

Horizontal takeoff and vertical landing

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Few airplanes can operate with conventional takeoff and vertical landing (and its subtypes STOVL, CATOVL) as the F-35B.

Horizontal takeoff and vertical landing (HTVL) in spaceflight has not been used, but has been proposed for some systems that use a two-stage to orbit launch system with a plane based first stage, and a capsule return vehicle. One of the few HTVL concept vehicles is the 1960s concept spacecraft Hyperion SSTO, designed by Philip Bono.[19]

Multi-mode configurations

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Vehicles use more than one mode also exist.

Vertical/Short takeoff landing (V/STOL)

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Main article: V/STOL

Vertical and/or short take-off and landing (V/STOL) aircraft that are able to take off or land vertically or on short runways. Vertical takeoff and landing (VTOL) includes craft that do not require runways at all. Generally, a V/STOL aircraft needs to be able to hover; helicopters are not typically considered under the V/STOL classification.

A rolling takeoff, sometimes with a ramp (ski-jump), reduces the amount of thrust required to lift an aircraft from the ground (compared with vertical takeoff), and hence increases the payload and range that can be achieved for a given thrust. For instance, the Harrier is incapable of taking off vertically with a full weapons and fuel load. Hence V/STOL aircraft generally use a runway if it is available. I.e. Short Take-Off and Vertical Landing (STOVL) or Conventional Take-off and Landing (CTOL) operation is preferred to VTOL operation.

V/STOL was developed to allow fast jets to be operated from clearings in forests, from very short runways, and from small aircraft carriers that would previously only have been able to carry helicopters.

The main advantage of V/STOL aircraft is closer basing to the enemy, which reduces response time and tanker support requirements. In the case of the Falklands War, it also permitted high performance fighter air cover and ground attack without a large aircraft carrier equipped with a catapult.

The latest V/STOL aircraft is the F-35B, which entered service in 2015.[20]

See also

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References

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Revisions and contributorsEdit on WikipediaRead on Wikipedia

Takeoff and landing

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from Grokipedia
Takeoff and landing are the essential transition phases in operations, during which an accelerates from a stationary position on the to achieve liftoff into sustained flight, and subsequently decelerates from airborne conditions to a controlled and rollout on the surface. These phases demand a precise balance of the four fundamental forces—lift, weight, , and drag—to ensure safe execution, with takeoff involving increased to generate sufficient lift exceeding weight, and landing relying on reduced and increased drag to manage descent and braking. Governed by (FAA) standards, both processes are influenced by factors such as aircraft weight, , wind conditions, surface, and configuration settings like flaps, which can significantly alter required distances and speeds. In takeoff, the procedure typically unfolds in three main segments: the ground roll, where the aircraft accelerates to rotation speed (often 1.2 times the stall speed) using full throttle while maintaining directional control via rudder and brakes; rotation, involving a gentle pitch-up to increase the angle of attack and initiate liftoff; and the initial climb, establishing a positive rate of ascent to clear obstacles, such as the FAA-mandated 50-foot height, before retracting flaps and gear. Performance metrics, including ground roll distance, scale with the square of aircraft weight and inversely with air density, meaning higher weights or hot/high-altitude conditions can double or more the required runway length, while headwinds shorten it and tailwinds extend it proportionally. Specialized takeoffs, such as short-field or soft-field variants, adapt these principles by using full flaps for maximum lift coefficient or maintaining a nose-high attitude to minimize ground drag on unprepared surfaces. Landing mirrors takeoff in complexity but emphasizes deceleration and precision, comprising the approach (establishing a stabilized glide path at 1.3 times speed with flaps extended), (rounding out to reduce rate and achieve a gentle ), and rollout (braking and reverse thrust to stop within the available ). Like takeoff, landing distances increase quadratically with weight and are affected by environmental factors, but configurations such as full flaps can double the maximum to enable steeper approaches and lower speeds, while ground effect—reduced induced drag within one wingspan of the surface—cushions the final descent but complicates go-arounds if is insufficient. landings require techniques like crabbing or wing-low sideslip to counteract drift, with demonstrated limits up to 0.2 times speed, and protocols mandate go-arounds for unstabilized approaches if not stabilized by 1,000 feet above elevation in (IMC) or by 500 feet above elevation in (VMC). These phases account for a disproportionate share of incidents, with over 20% of accidents occurring during takeoff and departure, underscoring the need for pilot training, adherence to aircraft-specific performance charts in the Pilot's Operating Handbook (POH), and consideration of variables like runway contamination, which can lead to hydroplaning at speeds above 8.6 times the of tire pressure in pounds per . Advances in , such as high-lift devices and reversers, have improved margins, but operational limits remain tied to requirements ensuring clearance and stopping capability under varied conditions.

Fundamental Concepts

Takeoff Process

Takeoff in refers to the phase during which an transitions from a stationary position on the ground to sustained flight in the air, primarily achieved through engine thrust that overcomes aerodynamic drag and the gravitational force acting on the . This process requires the generation of sufficient aerodynamic lift to support the 's weight, marking the foundational transition to airborne operations for . The takeoff process unfolds in several key phases: the ground roll, where the aircraft accelerates along the from standstill to speed using maximum available ; , in which the pilot raises the nose to increase the angle of attack and initiate liftoff; initial climb, where the aircraft ascends while accelerating to a safe climb speed; and continued acceleration to reach the best speed (V_Y). During the ground roll, friction from tires and must be minimized, while propels the aircraft forward until builds enough for lift to exceed weight. At the core of takeoff physics is the lift equation, which quantifies the generated by the s: L=12ρv2SCLL = \frac{1}{2} \rho v^2 S C_L where LL is lift, ρ\rho is air density, vv is , SS is area, and CLC_L is the influenced by and flap settings. Successful takeoff demands a sufficient to accelerate the against drag and provide the excess power needed for climb, typically requiring to exceed the sum of drag and the horizontal component of during the roll. Runway length requirements are calculated based on , available , and environmental conditions, often using performance charts that account for acceleration distance to reach liftoff speed plus a margin. Several factors critically influence the takeoff process, including weight, which directly increases the required lift and extends the ground roll; flap settings, which enhance CLC_L to reduce the speed needed for liftoff; wind conditions, where headwinds shorten the roll by lowering groundspeed for a given ; and altitude, which decreases air (ρ\rho) and thus reduces performance and lift efficiency, necessitating longer runways at high elevations. The historical foundation of powered takeoff was established on December 17, 1903, when Orville Wright achieved the first sustained, controlled flight of a heavier-than-air craft at , covering 120 feet in 12 seconds after a brief ground roll. This event demonstrated the practical integration of , lift, and control for overcoming and drag in manned flight.

Landing Process

Landing is the controlled phase of flight during which an aerial vehicle reduces its altitude and forward speed to make contact with a landing surface and subsequently stop. This process requires precise management of aerodynamic forces to ensure a safe touchdown and deceleration, distinguishing it from the acceleration and ascent of takeoff. The landing process unfolds in distinct phases: the approach, where the aircraft aligns with the runway centerline and maintains a stabilized descent at approximately 500-800 feet per minute; the flare, involving a gradual pitch-up to increase the angle of attack and arrest the descent rate just above the surface; touchdown, the moment of initial wheel contact ideally at or near stall speed; rollout, the ground phase following contact; and final deceleration to a stop. During rollout, deceleration is accomplished through aerodynamic drag from the aircraft's configuration, wheel brakes applied progressively to avoid skidding, spoilers that disrupt lift and augment drag, and reverse thrust on turbine-powered aircraft to redirect engine exhaust forward. Key physics underpin these phases, particularly aerodynamic drag for deceleration, described by the equation
D=12ρv2SCdD = \frac{1}{2} \rho v^2 S C_d
where DD is drag force, ρ\rho is air density, vv is airspeed, SS is reference area (typically wing area), and CdC_d is the drag coefficient, which increases with extended flaps and gear. In the flare, pilots manage the angle of attack to generate sufficient lift for a soft touchdown without exceeding the critical angle that induces a stall. Near the surface, ground effect enhances lift by reducing induced drag through suppressed wingtip vortices, potentially causing the aircraft to float and requiring adjusted pitch control to avoid a prolonged or hard landing. Various environmental and operational factors affect landing safety and performance, including crosswinds necessitating and inputs to counter drift, reduced visibility demanding reliance on instruments or visual cues for alignment, runway surface conditions like wet or contaminated pavement that diminish braking , and aircraft configuration changes such as extension, which boosts parasite drag but must occur early to stabilize the approach. Safety considerations emphasize metrics like distance required, calculated to include approach to 50 feet above threshold, , and rollout under actual weight, wind, and conditions, often factored by 1.67 for dry runways in to provide a margin. procedures mitigate risks from unstabilized approaches, involving immediate full , pitch adjustment for a positive climb rate, and gradual flap retraction.

Horizontal Takeoff and Landing Configurations

Conventional and Reduced Variants

Conventional takeoff and landing () refers to the standard horizontal takeoff and landing operations of that utilize the full length of a prepared surface for acceleration and deceleration. In , accelerate along the to achieve the necessary lift for rotation and liftoff, typically requiring paved or hardened surfaces to support the high speeds and weights involved. Reduced takeoff and landing (RTOL) variants build on principles but incorporate design features, such as low and advanced high-lift devices, to shorten required distances compared to conventional aircraft. For example, historical RTOL concepts have demonstrated field length reductions of around 25% in specific cases through optimized . Operational techniques like reduced settings, limiting to 75-95% of maximum, are sometimes used in conjunction but result in longer ground rolls due to slower acceleration; they are applied primarily to reduce engine wear under favorable conditions (e.g., low temperatures, long s) where full exceeds safety margins. Key design elements for CTOL and RTOL include , which is the aircraft's weight divided by its wing area and directly influences stall speeds and required takeoff velocities—higher demands longer runways for sufficient lift generation. High-lift devices such as leading-edge slats and trailing-edge flaps are deployed to increase the wing's camber and effective area, boosting the maximum by 50-100% during takeoff and landing phases. Engine placement, often under the wings or at the rear fuselage, is optimized to provide a thrust line that assists in pitch rotation without excessive tail strikes, ensuring smooth transition to climb. These configurations are widely applied in commercial airliners like the , which typically requires about 2,000 meters of dry for takeoff at maximum weight under standard conditions. Military transports, such as the , also employ and RTOL for tactical operations, using runways of 900-1,500 meters depending on load and configuration to deliver troops and cargo to forward bases. Takeoff field length in these systems integrates factors like mass and ambient through performance models that scale distance quadratically with weight—doubling mass can quadruple the required length due to increased and lift needs—and inversely with air , where higher temperatures reduce density and extend distances by 10-20% per 10°C rise above standard. These effects are quantified in standards, ensuring safe margins for varying environmental conditions.

Short Takeoff and Landing Systems

Short takeoff and landing () systems refer to configurations engineered for takeoffs and landings on runways under 300 meters, often on unprepared or rough such as grass, gravel, or , enabling operations in remote locations where conventional cannot function effectively. These capabilities are achieved through specialized aerodynamic designs that prioritize low-speed lift generation and minimal ground roll, distinguishing STOL from standard horizontal takeoff and landing methods that require longer, prepared surfaces. Key technologies in STOL systems include , which uses air blowing over the wing surface to delay airflow separation and enhance lift at low speeds; high-aspect-ratio wings, which improve lift-to-drag ratios for better low-speed performance; and vectored thrust systems that direct engine exhaust to augment lift during critical phases. These enhancements allow STOL aircraft to operate with reduced stall speeds and higher angles of attack compared to conventional designs. Representative examples include the DHC-6 Twin Otter, a twin-engine capable of a ground roll takeoff of approximately 310 meters under standard conditions, and modern bush planes like the CubCrafters Carbon Cub, which exemplify ongoing advancements in lightweight designs for backcountry access. Performance features such as leading-edge slats reduce stall speed by increasing the critical angle of attack, enabling safer operations near stall; for instance, slats can extend the stall angle beyond 15 degrees, while post-takeoff climb rates in aircraft often exceed 2,000 feet per minute. STOL systems have supported military operations in Arctic and remote environments since the 1940s, with early examples like the Fieseler Fi 156 Storch providing reconnaissance and liaison roles on snow-covered fields during World War II. These aircraft facilitated troop insertions and supply missions in harsh terrains, influencing later designs for cold-weather logistics and forward basing.

Carrier-Based Systems

Carrier-based systems enable fixed-wing aircraft operations from the decks of naval vessels, primarily through specialized launch and recovery methods adapted to the constrained and dynamic environment of an aircraft carrier. These systems, developed to project air power at sea, rely on mechanical assistance for takeoff and rapid deceleration during landing to compensate for the short deck length, typically around 300 meters. The two primary configurations are CATOBAR (Catapult-Assisted Take-Off But Arrested Recovery) and STOBAR (Short Take-Off But Arrested Recovery), each tailored to specific naval requirements and aircraft capabilities. CATOBAR employs steam-powered or electromagnetic catapults to accelerate from stationary to takeoff speed over a brief distance, followed by arrested recovery where a tailhook engages wires to halt the rapidly. Steam catapults, using high-pressure from the ship's boilers, propel the via a shuttle connected to the nose gear, achieving end speeds sufficient for heavy loads. Modern electromagnetic systems, like the (EMALS), offer precise control and reduced maintenance. Arrested recovery involves four to five wires stretched across the deck, tensioned by hydraulic engines to decelerate the from over 200 km/h to a stop in about 100 meters by absorbing the 's . As of 2025, the U.S. Navy's Ford-class carriers use the Advanced (AAG), which employs rotary water twisters for more consistent and efficient energy absorption compared to traditional hydraulic systems. STOBAR, prevalent in non-U.S. navies, combines a short takeoff aided by a bow-mounted ski-jump ramp with arrested recovery using similar hook-and-wire mechanisms. The ski-jump, angled at 12-14 degrees, converts horizontal deck speed into vertical lift, allowing lighter payloads without catapults. This system limits compared to but simplifies carrier design and reduces mechanical complexity. Arrested landings in STOBAR function identically to , ensuring compatibility with conventional tailhook-equipped aircraft. Aircraft designed for carrier operations incorporate key adaptations, including reinforced to withstand high sink rates of up to 6.5 m/s and forces exceeding 3g, tailhooks for wire engagement, and folding wings to optimize storage in the ship's and on deck. The features strengthened struts and energy-absorbing mechanisms to handle impacts far exceeding land-based requirements, while tailhooks deploy from the to snag wires at precise angles. Folding wings, often pivoting at mid-span, reduce the aircraft's footprint by up to 50%, enabling carriers to accommodate dozens of . Representative examples include the U.S. Navy's F/A-18 Hornet, which uses for launches reaching approximately 250 km/h via , supporting full combat loads from carriers like the class. In contrast, India's MiG-29K operates under on the , utilizing the ski-jump for short takeoffs and arrested recovery for landings, with the carrier's 14-degree ramp enabling operations in the region. Carrier operations face significant challenges from deck motion due to sea states, which can pitch and roll the ship up to 10 degrees, complicating approach and wire engagement. Wind-over-deck conditions, influenced by ship speed (typically 20-30 knots) and natural winds, are optimized by steaming into the relative wind to boost effective airspeed by 10-20 knots, but turbulence from the island superstructure adds shear risks. Historical evolution traces to the 1910s, when biplanes like Eugene Ely's Curtiss pusher achieved the first shipboard takeoff from USS Birmingham in 1910 and landing on USS Pennsylvania in 1911, using rudimentary platforms and nets before modern catapults and wires emerged in the 1920s.

Vertical Takeoff and Landing Configurations

Aircraft Applications

Vertical takeoff and landing (VTOL) aircraft are designed to achieve full vertical lift without requiring a forward run, enabling operations in confined spaces such as urban environments or remote sites where traditional runways are unavailable. These aircraft generate the necessary through powered rotors, vectored jet engines, or embedded fans, allowing them to hover, ascend vertically, and transition to forward flight. This capability is particularly suited for applications like rapid troop insertion or in inaccessible areas, as well as emerging civilian uses in . VTOL aircraft encompass several distinct types, each addressing the challenges of vertical lift differently. Tail-sitter configurations, such as the Ryan X-13 Vertijet, position the entire fuselage vertically for takeoff and landing, using a jet engine for propulsion and relying on control surfaces or reaction jets for stability in hover before transitioning to horizontal flight by tilting the aircraft forward. Convertible designs, exemplified by tiltrotor systems like the Bell Boeing V-22 Osprey, feature rotating nacelles that shift proprotors from vertical to horizontal orientation, combining helicopter-like vertical performance with fixed-wing speed and range for missions requiring both hover and long-distance cruise. Lift-fan systems, as implemented in the Lockheed Martin F-35B Lightning II, employ a shaft-driven, counter-rotating fan mounted forward in the fuselage to provide supplemental vertical thrust, augmented by the main engine's vectored nozzle, enabling short takeoff and vertical landing (STOVL) operations from amphibious assault ships or austere bases. The historical development of operational VTOL aircraft began in the mid-20th century, with the emerging in the 1950s as the first successful VTOL fighter. Developed under the UK's P.1127 program, the Harrier utilized the engine with four vectored nozzles to direct thrust for vertical operations, achieving its in 1967 and entering RAF service in 1969 as a ground-attack platform capable of operating from improvised forward bases without runways. This jet-lift innovation paved the way for subsequent designs, influencing modern and fan-assisted systems used in confined-area combat and transport roles. Aerodynamic considerations in VTOL aircraft center on optimizing hover , smooth transition to forward flight, and managing —the ratio of to or area—which directly impacts power requirements and stability. In hover, lower enhances by distributing over a larger area, reducing induced power needs and enabling longer loiter times, as seen in -based systems where (a measure of hover performance) improves with reduced loading. Transition to forward flight involves careful control of pitch, , and to avoid stalls or excessive drag, with designs like the V-22 achieving this by progressively tilting while maintaining positive lift. High in jet-lift VTOLs, such as the Harrier, allows compact designs but demands precise nozzle management to counteract hot gas reingestion and ensure stable conversion. Key challenges in VTOL aircraft operations include diminished performance at hot/high altitudes and elevated fuel consumption during hover. At high elevations or in hot conditions, thinner air reduces engine mass flow and output, limiting capacity and hover duration; for instance, the F-35B's lift fan and vectored engine experience significant degradation in such environments, necessitating adjusted takeoff procedures. Hover phases are particularly fuel-intensive, with jet-lift systems consuming 3-4 times more per unit than conventional helicopters due to inefficient and high , which can restrict mission radius unless supplemented by forward flight efficiency. These issues drive ongoing advancements in propulsion integration for urban and expeditionary applications. As of November 2025, progress in electric VTOL (eVTOL) for includes beginning power-on testing of its first FAA-conforming aircraft in the final phase of type certification, alongside FAA plans for public trials of advanced air mobility operations.

Rocket and Spacecraft Applications

Vertical takeoff and vertical landing () for s and involves a vertical ascent powered by engines to achieve access, followed by a controlled vertical descent using retro-propulsion to enable precise, reusable touchdowns on or other surfaces. This configuration relies on high-thrust chemical propulsion systems, such as and or engines, to counteract gravitational and aerodynamic forces during both phases. Unlike VTOL, operates in near-vacuum conditions and high hypersonic speeds, necessitating robust thermal protection and precise guidance for reentry and landing. Core technologies facilitating VTVL include grid fins for aerodynamic steering, retro-propulsion for deceleration, and deployable landing legs for impact absorption. Grid fins, consisting of lattice-like structures made from high-temperature materials like , deploy post-separation to generate control moments by modulating drag and lift during atmospheric reentry, allowing trajectory corrections without continuous engine firing. Retro-propulsion entails reigniting main engines to fire against the descent velocity, reducing speed from hypersonic to near-zero for a . Landing legs, often pneumatically or hydraulically actuated, extend prior to to distribute loads and protect the vehicle's structure, enabling rapid refurbishment for reuse. The physics of centers on delta-v budgets for landing maneuvers and for attitude control. The delta-v requirement for the landing burn typically totals around 2000 m/s for orbital-class first stages, encompassing deceleration from terminal reentry to hover, with atmospheric drag assisting but engine burns providing the final precision. This value scales with vehicle mass and atmospheric , often reverse-engineered from operational profiles like those of reusable boosters. , achieved by gimbaling the engine nozzle, directs the vector to produce steering torques; mathematically, the thrust component in the body frame can be expressed as T⃗=T(sin⁡δxsin⁡δycos⁡δxcos⁡δy),\vec{T} = T \begin{pmatrix} \sin \delta_x \\ \sin \delta_y \\ \cos \delta_x \cos \delta_y \end{pmatrix},
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