The Dornier Do.31, which was developed in the 1960s in Germany by Dornier engineers, is a truly unique aircraft. This is the world's only vertical take-off and landing transport aircraft. It was developed by order of the German military department as a tactical jet transport aircraft. The project, unfortunately, never went beyond the experimental aircraft stage; a total of three Dornier Do.31 prototypes were produced. One of the prototypes built is today an important exhibit at the aviation museum in Munich.
In 1960, the German company Dornier, under conditions of strict secrecy, commissioned by the German Ministry of Defense, began designing a new tactical military transport aircraft with vertical take-off and landing. The aircraft was to receive the designation Do.31; its feature was a combined power plant of lift-propulsion and lifting engines.
The design of the new aircraft was carried out not only by Dornier engineers, but also by representatives of other German aviation companies: Weser, Focke-Wulf and Hamburger Flyugzeugbau, which in 1963 were merged into a single aviation company, designated WFV. At the same time, the Do.31 military transport aircraft project itself was part of the German program to create vertically take-off transport aircraft. This program took into account and revised NATO tactical and technical requirements for military transport VTOL aircraft.
In 1963, with the support of the German and British Ministries of Defense, an agreement was signed for a period of two years on the participation in the project of the British company Hawker Siddley, which had extensive experience in designing the Harrier vertical take-off and landing aircraft. It is noteworthy that after the expiration of the contract it was not renewed, so in 1965 the Hawker Siddley company returned to developing its own projects. At the same time, the Germans tried to attract US companies to work on the design and production of the Do.31 aircraft. The Germans have achieved some success in this area; they managed to sign an agreement on joint research with NASA.
In order to determine the optimal design of the transport aircraft being developed, the Dornier company compared three types of vertically taking off aircraft: a helicopter, an aircraft with rotary propellers, and an aircraft with lift-and-propulsion turbofan engines. As an initial task, the designers used following parameters: transportation of three tons of cargo over a distance of up to 500 km and subsequent return to the base. The studies have demonstrated that a vertically taking off tactical military transport aircraft equipped with lift-and-propulsion turbofan engines has a number of important advantages compared to the other two types of aircraft under consideration. Therefore, Dornier focused on working on the selected project and began calculations aimed at choosing the optimal layout of the power plant.
The design of the first Do.31 prototype was preceded by quite serious testing of the models, which were carried out not only in Germany in Göttingen and Stuttgart, but also in the USA, where they were carried out by NASA specialists. The first models of the military transport aircraft did not have nacelles with lifting turbojet engines, since it was planned that the aircraft’s power plant would consist of only two lift-and-propulsion turbofan engines from Bristol with a thrust of 16,000 kgf in afterburner. In 1963, in the USA, at the NASA Langley Research Center, tests of aircraft models and individual elements its designs in wind tunnels. Later, the flying model was tested in free flight.
As a result of research carried out in two countries, the final version of the future Do.31 aircraft was formed; it was supposed to receive a combined power plant of lift-propulsion and lifting engines. To study the controllability and stability of an aircraft with a combined power plant in hovering mode, the Dornier company built an experimental flying testbed with a cruciform truss structure. The overall dimensions of the stand were the same as those of the future Do.31, but the total weight was significantly less - only 2800 kg. By the end of 1965, this stand had gone through a long test path, in total it completed 247 flights. These flights made it possible to build a full-fledged vertical take-off and landing military transport aircraft.
At the next stage, an experimental aircraft, designated Do.31E, was created specifically for testing the design, testing piloting techniques and checking the reliability of the new device’s systems. The German Ministry of Defense ordered three similar machines for construction, with two experimental aircraft intended for flight tests, and the third for static tests.
Tactical military transport aircraft Dornier Do 31 was made according to a normal aerodynamic design. It was a high-wing aircraft, equipped with propulsion and lifting engines. The original concept featured two Bristol Pegasus turbofan engines in each of the two inner engine nacelles and four Rolls-Royce RB162 lift engines, which were located in the two outer engine nacelles at the wing tips. Subsequently, it was planned to install more powerful and advanced RB153 engines on the aircraft.
The fuselage of the semi-monocoque aircraft was all-metal and had a circular cross-section with a diameter of 3.2 meters. In the forward part of the fuselage there was a cockpit designed for two pilots. Behind it was a cargo compartment, which had a volume of 50 m 3 and overall dimensions of 9.2 × 2.75 × 2.2 meters. The cargo compartment could easily accommodate 36 paratroopers with equipment on reclining seats or 24 wounded on stretchers. There was a cargo hatch in the tail of the aircraft; there was a loading ramp.
The aircraft's landing gear was retractable, tricycle, and each rack had twin wheels. The main supports were retracted back into the nacelles of the lifting propulsion engines. The nose support of the landing gear was controlled and self-orienting; it also retracted back.
Construction of the first experimental aircraft was completed in November 1965, it received the designation Do.31E1. The plane first took off on February 10, 1967, performing a normal takeoff and landing, since lifting turbojet engines were not installed on the plane at that time. The second experimental machine Do.31E2 was used for various ground tests, and the third experimental transport aircraft Do.31E3 received full set engines. The third aircraft made its first vertical take-off flight on July 14, 1967.. The same aircraft made a complete transition from vertical takeoff to horizontal flight followed by vertical landing, this happened on December 16 and 21, 1967.
It is the third copy of the Dornier Do 31 experimental aircraft that is currently in the Munich Aviation Museum. In 1968, this aircraft was first presented to the general public, this happened as part of the international aviation exhibition that took place in Hannover. At the exhibition, the new transporter attracted the attention of representatives of British and American companies who were interested in the possibilities of not only military, but also its civilian use. The American space agency also showed interest in the aircraft; NASA provided financial assistance for flight testing and research into optimal landing trajectories for vertical takeoff and landing aircraft.
The following year, the experimental Do.31E3 aircraft was shown at the Paris Aerospace Show, where the aircraft also enjoyed success, attracting the attention of spectators and specialists. On May 27, 1969, the plane flew from Munich to Paris. As part of this flight, three world records were set for aircraft with vertical take-off and landing: flight speed - 512.962 km/h, altitude - 9100 meters and range - 681 km. By the middle of that year, 200 flights had already been carried out on the Do.31E VTOL aircraft. During these flights, test pilots carried out 110 vertical takeoffs followed by a transition to horizontal flight.
In April 1970, the Do.31E3 experimental aircraft made its last flight, funding for this program was stopped, and the program itself was canceled. This happened despite the successful and, most importantly, accident-free flight testing of the new aircraft. At that time, the total cost of Germany's expenses for the program to create a new military transport aircraft exceeded 200 million marks (since 1962).
One of the technical reasons for the curtailment of the promising program could be called the relatively low maximum speed of the aircraft, its payload capacity and flight range, especially in comparison with traditional transport aircraft. The Do.31's flight speed was reduced, among other things, due to the high aerodynamic drag of its lift engine nacelles. Another reason for the curtailment of work was the growing disappointment at that time in military, political and design circles with the very concept of aircraft with vertical take-off and landing.
Despite this, the Dornier company, based on the experimental Do.31E aircraft, developed projects for improved military transport VTOL aircraft with a greater payload capacity - Do.31-25. It was planned to increase the number of lifting engines in the nacelles, first to 10, and then to 12. In addition, Dornier engineers designed the Do.131B vertical take-off and landing aircraft, which had 14 lifting turbojet engines at once.
A separate project for the civil aircraft Do.231 was also developed, which was supposed to receive two lift-and-propulsion turbofan engines from Rolls Royce with a thrust of 10,850 kgf each and another 12 lifting turbofan engines of the same company with a thrust of 5,935 kgf each, of which eight engines were located four in gondolas and four, two each, in the nose and tail of the aircraft fuselage. Estimated weight This model of aircraft with vertical take-off and landing reached 59 tons with a payload of up to 10 tons. It was planned that the Do.231 would be able to carry up to 100 passengers at a maximum speed of 900 km/h over a distance of 1000 kilometers.
However, these projects were never implemented. At the same time, the experimental Dornier Do 31 was (and remains at present) the only vertical take-off and landing jet military transport aircraft in the world built.
Flight characteristics of Dornier Do.31:
Dimensions:
– length – 20.88 m,
– height – 8.53 m,
- wingspan - 18.06 m,
- wing area - 57 m 2.
Empty weight – 22,453 kg.
Normal take-off weight is 27,442 kg.
Power plant: 8 Rolls Royce RB162-4D lift turbojet engines, takeoff thrust - 8x1996 kgf; 2 lift-propulsion turbofan engines Rolls Royce Pegasus BE.53/2, thrust 2x7031 kgf.
Maximum speed – 730 km/h.
Cruising speed – 650 km/h.
Practical range – 1800 km.
Service ceiling – 10,515 m.
Capacity - up to 36 soldiers with equipment or 24 wounded on stretchers.
Crew – 2 people.
Information sources:
— www.airwar.ru/enc/xplane/do31.html
— igor113.livejournal.com/134992.html
— www.arms-expo.ru/articles/129/67970
One of the Pentagon's most expensive "toys" - the F-35B fighter-bomber - this week took part in joint US-Japanese exercises aimed at cooling the DPRK's nuclear missile fervor.
Despite the wave of criticism, the need to resume production of cars of this class has recently become increasingly talked about in Russia. In particular, Deputy Defense Minister Yuri Borisov recently announced plans to build vertical take-off and landing aircraft (VTOL).
Read about why Russia needs such an aircraft and whether the aviation industry has enough strength to create it in the RIA Novosti material.
The most popular domestic combat aircraft with vertical take-off and landing was the Yak-38, which was put into service in August 1977. The aircraft has earned a controversial reputation among aviators - out of 231 aircraft built, 49 crashed in accidents and aviation incidents.
The main operator of the aircraft was the Navy - the Yak-38 was based on the aircraft-carrying cruisers of Project 1143 "Kyiv", "Minsk", "Novorossiysk" and "Baku".
As veterans of carrier-based aviation recall, the high accident rate forced the command to sharply reduce the number of training flights, and the flight time of Yak-38 pilots was a symbolic figure for those times - no more than 40 hours per year.
As a result, there was not a single first-class pilot in the naval aviation regiments; only a few had second-class flight qualifications.
Its combat characteristics were also questionable - due to the lack of an on-board radar station, it could only conditionally conduct air battles.
Using the Yak-38 as a pure attack aircraft seemed ineffective, since the combat radius during vertical takeoff was only 195 kilometers, and even less in hot climates.
Supersonic multi-role vertical take-off and landing fighter-interceptor Yak-141
To replace " difficult child“A more advanced vehicle, the Yak-141, was supposed to arrive, but after the collapse of the USSR, interest in it disappeared.
As seen, domestic experience the creation and operation of VTOL aircraft cannot be called successful. Why has the topic of vertical take-off and landing aircraft become relevant again?
“Such a machine is vital not only To the Navy, but also to the Air Force,” military expert, captain of the first rank Konstantin Sivkov told RIA Novosti.
the main problem modern aviation is that a jet fighter needs a good runway, and there are very few such airfields; destroying them with a first strike is quite simple.
During a period of threat, vertical take-off aircraft can be dispersed at least forest glades. Such a system for using combat aircraft will have exceptional combat stability.”
However, not everyone sees the feasibility of using VTOL aircraft in the land version as justified. One of the main problems is that during vertical takeoff the aircraft consumes a lot of fuel, which greatly limits its combat radius.
Russia is a large country, therefore, to achieve air supremacy, fighter aircraft must have “long arms.”
“The fulfillment of combat missions of fighter aircraft in conditions of partially destroyed airfield infrastructure can be achieved through a short take-off of conventional aircraft from a section of the runway less than 500 meters long,” says Oleg Panteleev, executive director of the Airport agency.
Another question is that Russia has plans to build an aircraft carrier fleet, so the use of vertically taking off aircraft will be the most rational. These may not necessarily be aircraft carriers, they may also be aircraft-carrying cruisers with the lowest cost parameters.”
F-35 fighter
By the way, the F-35B today is a purely naval aircraft, its main customer is the US Marine Corps (the aircraft will be based on landing ships). British F-35Bs will form the basis of the air wing of the newest aircraft carrier Queen Elizabeth, which was recently commissioned.
At the same time, according to Konstantin Sivkov, Russian design bureaus do not have to wait for new aircraft carriers to begin work on creating a Russian analogue of the F-35B.
“Vertical take-off and landing aircraft can be based not only on aircraft carriers. For example, a tanker is equipped with a ramp and becomes a kind of aircraft carrier, in Soviet time we had such projects.
In addition, VTOL aircraft can be used from warships capable of receiving helicopters, for example from frigates,” our interlocutor said.
Meanwhile, it is obvious that the creation of a Russian vertical take-off aircraft will require impressive resources and funds. The cost of developing the F-35B and its horizontal take-off cousins, according to various estimates, has already reached $1.3 billion, and several countries participated in the creation of the vehicle.
According to experts, to produce a vehicle comparable in performance to the F-35B, a number of serious problems will need to be solved: miniaturization of avionics, creation of a new generation of on-board systems and design of an airframe with special characteristics.
The Russian aviation industry has the potential for this, especially since many systems can be unified with the fifth-generation Su-57 aircraft. At the same time, one of the most labor-intensive components can be the car engine.
“The engine developer for the Yak-38 has ceased to exist. If any documentation on the rotary nozzle, including the afterburner, is probably still preserved, then people with practical experience in creating such components and assemblies will most likely no longer be found.
Here we have probably lost competencies,” says Oleg Panteleev. “In general, I believe that the aviation industry will be able to give a worthy response in the form of a capable VTOL project if the customer, represented by the Ministry of Defense, makes a decision on the aircraft-carrying fleet and its aviation component.”
UDC "Priboy"
Russia will be able to begin building aircraft carriers in the foreseeable future. According to the Ministry of Defense, the keel of the Project 23000 Storm heavy aircraft carrier is expected to be laid down in 2025–2030.
By this time, the Russian Navy intends to receive two new universal landing ships “Priboy”, capable of carrying aircraft with vertical take-off and landing.
Vadim Saranov
Vertical take-off and landing aircraft, flying in cruising (horizontal) flight modes like conventional aircraft, are capable of hovering in the air, like helicopters, and also taking off and landing vertically. To ensure vertical takeoff and landing modes on such an aircraft, it is necessary to have a special power plant that ensures the creation lift exceeding the weight of the aircraft.
The launch vertical thrust-to-weight ratio (the ratio of the lift generated by the engines to the weight of the aircraft) of modern VTOL aircraft is in the range of 1.05-1.45.
Depending on how the lifting force is created in the VTOL modes and the traction force in the marching (cruising) modes, a classification of VTOL aircraft can be made (Fig. 7.69).
Single power plant
(SU) contains one or more lifting propulsion engines
, which in GDP modes create vertical thrust, and in normal modes - propulsion thrust. The thrust is generated either by a propeller or by a jet of gases from a jet engine. Changing the direction of the thrust vector of lift-propulsion engines can be structurally ensured either by turning the entire engine in the desired direction, for example, relative to the wing or together with the wing on which they are attached, or by changing the direction of the jet (and thrust vector) of the jet engine.
Schematic diagram one of the possible devices that provide a change in the direction of the thrust vector P with a sliding visor 1 , illustrated in Fig. 7.70.
Composite SU includes two groups of engines: one of them is for creating vertical thrust in GDP modes ( lifting motors
), the other - to create cruising thrust ( propulsion engines
).
Combined SU also consists of two groups of engines: lifting and accelerating
And lifting and sustaining
, which (to a greater or lesser extent) participate in the creation of both vertical and propulsion thrust.
The choice of the type of power plant significantly affects the ability to solve specific problems that arise when designing a VTOL aircraft, and actually determines its concept, aerodynamic and structural-power configuration.
Engines 1
(Fig. 7.71) create a lifting force ( P=G/2
), balancing the force of gravity G
airplane. In operating modes close to the screen 2
(runway surface) engine jets 3
create complex currents around the aircraft caused by the interaction of gas jets reflected from the screen 4
with air currents 5
, flowing into the engine air intakes. The shape and intensity of these currents are
modes of hovering near the screen, the interaction of these currents with the free flow in the modes of GDP and transitional regimes
(from vertical to horizontal movement) depend on the power, number and location of engines (i.e., on the layout of the VTOL), which significantly affects the aerodynamic and torque characteristics of the VTOL, i.e., determines its layout.
Exposure to gas jets from engines causes airfield surface erosion
, the degree of which depends on the type of engines creating the lift force and on their location. Particles from the surface of the airfield, washed out by gas jets, together with high-temperature upward currents, affect the VTOL structure and, entering the air intakes of the engines, reduce their reliability, service life and traction characteristics. In order to reduce the influence of jets on the surface of the airfield and on the aircraft, the VTOL operating technique is often used. short takeoff and landing mode
(UVP), when the take-off and running distances are only a few tens of meters. This also makes it possible to increase the weight efficiency of the VTOL aircraft due to significantly lower fuel consumption during takeoff and landing modes.
One of the main problems arising in the development of VTOL aircraft is to ensure their balancing, stability and controllability in VTOL modes and transition modes, when the translational speed is zero or is not large enough for the effective operation of aerodynamic surfaces that create balancing and control forces and moments.
Balancing, stability and controllability of VTOL aircraft in these modes is ensured either mismatch (modulation) engine thrust, i.e. by increasing or decreasing the thrust of one engine compared to another, or by jet rudder systems, or a combination of these methods.
Mismatch ΔP
thrust (Fig. 7.72) of main engines 3
leads to a yaw moment ΔM y, mismatch ΔP 1
first group of lifting engines 1
leads to a roll moment ΔM x. Thrust mismatch ΔP 1
And ΔP 2
first and second groups of lifting engines 2
leads to a pitching moment ΔM z
.
Jet control system
VTOL (Fig. 7.73) includes several jet nozzles located at the maximum possible distance from the center of mass of the aircraft ( 1, 5, 6
), to which using pipelines 4
summed up compressed air from the lifting engine compressor 3
. Nozzle design 1
allows you to regulate air flow and, therefore, draft. Nozzle design 5
And 6
allows you to change not only the magnitude, but also the direction of the thrust force to the opposite (reverse the nozzle thrust).
When balanced in pitch (relative to the axis Z
) airplane (sum of nozzle thrust moments 1
, lifting 2
and lifting propulsion engine 3
relative to the center of mass is zero) increase in the nozzle thrust force 1
will cause a pitching moment, a decrease will cause a diving moment.
Shown in Fig. 7.73 direction of jets from nozzles 5 And 6 causes the aircraft to roll onto the left wing and turn left.
The pilot controls the operating mode of engines and jet rudders to change the forces and moments acting on the aircraft in the GDP modes and transient modes using the same control levers as on a conventional aircraft, i.e., simultaneously with the creation of control jet forces, the aerodynamic steering wheels are also deflected accordingly surfaces (elevator, ailerons and rudder), which, however, do not create control forces at low (pre-evolutionary) forward speeds of the aircraft. As the forward motion speed increases, the forces on the steering surfaces also increase and, with the help of automation, are gradually switched off from the operation of the jet control system.
It should be noted here that at low (pre-evolutionary) speeds a VTOL aircraft does not have its own stability, since the aerodynamic forces capable of returning it to its original position under random external influences are small. Therefore, the stability of the VTOL aircraft in these modes (stabilizing it and maintaining the balancing state) is ensured by the automatic means included in the control system, which, reacting to the angular movements of the aircraft during disturbances, without pilot intervention using jet rudders, return the aircraft to its original balancing position.
We have listed here only some of the problems of shaping the appearance of a VTOL aircraft, the solution of which already at the early stages of design requires the interaction of designers of various specializations.
To date, more than 50 types of vertical (short) take-off and landing aircraft have been designed, built and tested around the world. Most of the designs for these aircraft were based on military requirements.
The first domestic combat VTOL aircraft was created at the Design Bureau named after. A.S. Yakovlev (see section 20.2).
The advantages of VTOL aircraft that we mentioned at the beginning of Section 7.4 will undoubtedly lead to the creation of VTOL aircraft that can compete with conventional aircraft for the transport of passengers and cargo over short and medium distances.
Hydroaviation
Work on creating aircraft capable of taking off from and landing on water began almost simultaneously with work on creating land-based aircraft.
March 28, 1910 first flight seaplane
(from hydro...(Greek hydor- water) and an airplane) of his own design was made by the Frenchman A. Fabre.
Historically, officers of the Russian Navy stood at the origins of domestic aeronautics and aviation. They were the first in the world to develop naval aviation tactics, carried out an aerial bombardment of an enemy ship, created an aircraft carrier project, and were the first to fly in the skies of the Arctic.
The geographical and strategic features of the theaters of military operations of that time, the long maritime borders on the Baltic and Black Seas, the lack of specially equipped airfields for the operation of land aircraft and at the same time the abundance of large rivers, lakes, and free sea spaces determined the need to create naval aircraft manufacturing in our country.
The development of hydroaviation began with the installation of land aircraft on floats. First float planes
(Fig. 7.74) had two main floats 1
and additional 2
(auxiliary) float in the tail or bow.
Depending on how the aircraft is based and operated from the surface water areas
(from lat. aqua- water) - hydrodromes
, it is possible to classify seaplanes (Fig. 7.75).
Float circuits
are currently used for light aircraft, although already in 1914 the four-engine heavy aircraft "Ilya Muromets" made its first flight (see Fig. 19.1), placed on floats along three-float circuit
with a tail float, in 1929, during a flight on the route Moscow - New York of the Land of Soviets aircraft (see Fig. 19.7) 7950 km - from Khabarovsk to Seattle the plane flew over water, and on this section the land landing gear was replaced by a float two-float circuit
.
The increase in the size and mass of seaplanes and, as a consequence, the increase in the size of the floats made it possible to accommodate crew and equipment in them, which led to the creation of seaplanes of the type "flying boat" single-boat
schemes and two-boat scheme
- catamaran
(from Tamil kattumaram, literally - tied logs).
Integrated circuit
most appropriate for heavy multi-purpose ocean-going seaplanes. A partially submerged wing makes it possible to reduce the size of the boat and increase the aerohydrodynamic perfection of the seaplane.
amphibious aircraft
(from Greek amphibios- leading a dual lifestyle) is adapted for taking off from land and water and landing on them.
Thus, technical solutions, ensuring the basing and operation of the aircraft from the water surface, actually determine the appearance (aerodynamic design) of the seaplane.
The complexity and number of problems that designers must solve when creating a seaplane increase significantly, since in addition to the high aerodynamic and takeoff and landing characteristics of a conventional aircraft, the seaworthiness specified in the specifications must also be ensured.
The seaworthiness of a seaplane can be assessed using the methods of the scientific discipline "Fluid mechanics", which studies the movement and equilibrium of fluids, as well as the interaction between fluids and solids completely or partially immersed in liquid.
Seaworthiness (seaworthiness)
a seaplane is characterized by the possibility of its operation in water areas with certain hydrometeorological conditions - wind speed and direction, direction, speed of movement, shape, height and length of water waves.
The seaworthiness of a seaplane is assessed by the maximum roughness of the water area, at which it is possible safe operation.
Just as the International Standard Atmosphere (ISA) is used to evaluate the flight characteristics of an aircraft (see Section 3.2.2), a certain scale ( mathematical model), establishing a connection between the verbal description of excitement, wave height and score (from 0 to IX) - degree of excitement
.
In accordance with this scale, for example, weak waves (wave height up to 0.25 m) are assessed as I, significant waves (wave height 0.75-1.25 m) are assessed as III, strong waves (wave height 2.0- 3.5 m) is rated V, exceptional waves (wave height 11 m) are rated IX.
Seaworthiness ( seaworthiness) seaplane include such seaplane characteristics as buoyancy
,
stability
,
controllability
,
unsinkability
and so on.
These qualities are determined by the shape and size of the underwater displacement part
(boat or float) of a seaplane, the distribution of seaplane masses along the length and height.
In the future, when considering the seaworthiness of a seaplane, if without special reservation they can be equally attributed to a boat and a float, we will use the term “boat”. Buoyancy- the ability of a seaplane to float in a given position relative to the water surface.
A seaplane, like any other floating body, such as a ship, is kept afloat by Archimedean force
P = Wρ in g = G,
Seaplane gravity G applied at the aircraft's center of mass (c.m.), maintaining force (Archimedean force, the force of the displaced fluid acting on the seaplane boat) R is applied at the center of mass of the volume of water displaced by the boat, or, in naval terminology (which is widely used by seaplane designers), in center of magnitude (c.v.).
Obviously, to ensure the balance of the aircraft afloat (Fig. 7.76) forces G And P must lie on the straight line connecting the center. and c.v., in the vertical longitudinal plane of symmetry of the seaplane - the center plane of the boat (DP). It is also obvious that the main plane of the boat (OP) is a horizontal plane passing through the lower point of the boat surface perpendicular to the center plane, and, accordingly, the lower horizontal horizontal plane of the boat (LSG), the horizontal horizontal plane of the aircraft (GHS) and the deck 1 - the upper surface of the boat is generally not parallel to the plane of the water surface and the line of contact of the water surface with the hull of the seaplane boat W O L O.
Line of contact of calm water surface with the hull of a seaplane boat W O L O at full take-off weight and engines turned off - load waterline
(from Dutch water- water and lijn- line). Load water line (GWL) when sailing in fresh water does not coincide with GVL when swimming in sea water, since the density of fresh river or lake water ρ in=1000 kg/m 3, density sea water ρ in= 1025 kg/m3.
Respectively, draftT
(the distance from the GVL to the very bottom of the boat, characterizing the immersion of the boat below the water level) with the same take-off weight of the seaplane in fresh water will be greater than in sea water.
The bow and stern draft values are determined by landing
seaplane boats relative to the water surface - trim
boats (from lat. differens (differentis)- difference) - its inclination in the longitudinal plane, which is measured by the trim angle φ 0
or the difference between the drafts of the stern and bow. If the difference is zero, the boat is said to be "sitting on an even keel"; if the stern draft is greater than the bow draft, the boat “sits with trim to the stern” (as shown in Fig. 7.76), if it is less, the boat “sits with trim to the bow.”
Stability
(analogous to the term “stability” in marine terminology) when sailing - the ability of a seaplane, deflected from an equilibrium position by external disturbing forces, to return to its original position after the cessation of the disturbing forces.
Obviously, when swimming a body partially or completely (completely) immersed in water, there are no other forces to return it to the equilibrium position except gravity G
and equal strength of support R
. Consequently, only the relative position of these forces will determine the stability or instability of a floating body, as illustrated in Fig. 7.77.
If the center of mass of the body is located below the center of magnitude (Fig. 7.77,a), when deviating from the equilibrium position, a stabilizing moment occurs ΔМ = Gl
, returning the body to its original position stable equilibrium.
If the center of mass of the body is located above the center of magnitude (Fig. 7.77, c), when deviating from the equilibrium position, a destabilizing moment occurs ΔМ = Gl
, and the body cannot independently return to its original position unstable equilibrium
.
If the position of the center of mass of the body coincides with the position of the center of magnitude (Fig. 7.77, b), the body is in indifferent equilibrium.
It should be noted that the position of the center of the quantity depends significantly on the shape of the immersed part of the body and the angle of its deviation from the initial equilibrium position.
Seaplane stability
(as well as the stability of the vessel) is usually determined by the relative position of the center of mass and metacenter
- the center of curvature of the line along which the center of magnitude of the displacement body shifts when it is thrown out of balance.
Metacenter - from Greek. meta- between, after, through - component difficult words, meaning intermediateness, following something, transition to something else, change of state, transformation and lat. - centrum focal point, center.
A distinction is made between transverse and longitudinal stability of a seaplane (when the plane is tilted in the transverse and longitudinal planes, respectively).
Lateral stability.
Let's consider the case of transverse inclination - the deviation of the boat's center plane (DP) from the vertical, for example, under the influence of a gust of wind.
The seaplane (Fig. 7.78, a) is afloat in a state of equilibrium, gravity G
and maintaining power R
equal, lie in the diametrical plane, size A
determines the elevation of the center of mass above the center of magnitude.
From the side component of a gust of wind V V(Fig. 7.78, b) a heeling moment will occur M kr in, depending on the speed pressure, the area and span of the windward (facing the direction from which the wind is blowing) wing console, and the area of the lateral projection of the seaplane. Under the influence of this moment, the plane will tilt at a certain small (we will assume - infinitesimal) angle γ
and the new position of the boat will determine the new load waterline W 1 L 1, the plane of which is inclined at an angle γ
from the original waterline W O L O.
The shape of the underwater (displacement) part of the boat will change: the volume limited in each cross section of the boat by a figure 1
, will come out from under the water, and an equal volume limited in each cross section of the boat by the figure 2
, will go under water. Thus, the magnitude of the supporting force will not change (P = Wρ in g = G)
WITH O exactly WITH 1
. Dot M O intersection of two adjacent lines of action of Archimedean forces at an infinitesimal angle γ
between them is initial metacenter
.
Metacentric radius ρ 0
determines the initial curvature of the line of displacement of the center of the boat's size during a roll.
A measure of the lateral stability of a seaplane is the value metacentric height h o = ρ o - a:
- If h O> 0 - the boat is stable;
- If h
O= 0 - indifferent equilibrium;
- If h O < 0 - лодка неостойчива.
In the considered example h O< 0. Нетрудно видеть, что перпендикулярные к поверхности воды и равные силы R
And G
will be paired with the shoulder l
, and the moment of this couple M cr G = Gl
coincides in direction with the disturbing moment M kr in and increases the roll angle. Thus, the seaplane shown in Fig. 7.78, b, under the influence of external disturbances does not return to its original position, i.e., does not have lateral stability.
Obviously, to ensure lateral stability, the center of mass must be below the lowest position of the metacenter.
Most modern seaplanes are made according to the classical aerodynamic design with a fuselage - a boat, which is given the appropriate shape for taking off from water and landing on water, a high-mounted wing with engines installed on it or on the boat for maximum distance from the water surface in order to exclude when moving on water flooding the wing with water and getting it into the engines and onto the propellers of aircraft with a propeller-driven power plant, therefore in most cases the center of mass of the aircraft is higher than the metacenter (as in Fig. 7.78, b) and a single-boat seaplane is transversely unstable.
Problems of lateral stability of a single-float or single-boat seaplane can be solved by using underwing floats (Fig. 7.79).
Underwing float
1
installed on a pylon 2
as close to the end of the wing as possible 3
.Supporting (supporting)
underwing floats do not touch the water when the seaplane is moving on flat water 4
and ensure a stable position of the seaplane with roll angles of 2-3° when parked, load-bearing underwing floats
partially submerged in water and provide parking without heeling.
The displacement of the float is selected in such a way that under the influence of wind at a certain speed V V seaplane on the edge of a wave 5
, corresponding to the maximum roughness of the water area specified in the design specifications, tilted at a certain angle γ
. In this case, the restoring moment of the float, determined by the supporting force of the float R P and distance b P from the center plane of the float to the center plane of the boat, M n = R P b P, must parry (balance) heeling moments M kr in from the wind and M cr G from an unstable boat.
Longitudinal stability
is determined by the same conditions as the transverse one. If, under the influence of any external disturbance, the seaplane (Fig. 7.80) receives a longitudinal inclination from the initial position determined by the waterline W O L O, for example increasing by angle Δφ
trim to the bow, this will determine the new load waterline W 1 L 1.
Boat volume 1
will come out from under the water, and an equal volume 2
will go under water, while the value of the supporting force will not change (R = Wρ in g = G)
, however, the center of the quantity will shift from its original position From 0 exactly C 1. Dot M O * intersection of two adjacent lines of action of supporting forces at an infinitesimal angle Δφ
between them will determine the position initial longitudinal metacenter
.
A measure of the longitudinal stability of a seaplane - longitudinal metacentric height
H
o = R o - a.
It is easier to ensure longitudinal stability of a seaplane than transverse stability, in the sense that a boat that is highly developed in length almost always has natural longitudinal stability ( H O > 0).
Note that the diving moment from the engine thrust, the line of action of which usually passes above the center of mass of the aircraft, deepens bow boat, reduces the angle of initial trim, i.e. forces the boat to take some trim on the bow, which will determine the new cargo waterline
, which is called "persistent"
.
Hydrostatic forces
(supporting forces) that ensure the buoyancy and stability of the boat at rest, naturally, to a greater or lesser extent manifest themselves in the process of moving through the water.
Very important characteristic seaplane, which determines its seaworthiness is the ability to overcome water resistance and develop the required speed through the water with minimal power consumption.
Hydrodynamic force
The resistance of water to the movement of the boat in sailing mode is determined friction of water in the boundary layer(friction resistance) and distribution of hydrodynamic pressure of water flow on the boat (shape resistance associated with the formation of vortex currents - it is sometimes called whirlpool resistance) and depends on the speed of movement (velocity pressure ρ in V 2/2
), shape and condition of the boat's surface.
It is appropriate to recall here that the density of water ρ in about 800 times more dense than air at sea level!
To this resistance is added wave drag, which, in contrast to wave drag associated with irreversible energy losses in the shock wave during flight at supercritical speeds (see Section 5.5), occurs when a body moves near the free surface of the liquid (the interface between water and air) .
Characteristic impedance
- part of the hydrodynamic resistance, characterizing the energy consumption for the formation of waves.
Wave resistance in water (heavy liquid) occurs when a submerged or semi-submerged body (float, boat) moves near the free surface of the liquid (i.e., the boundary of water and air). A moving body exerts additional pressure on the free surface of the liquid, which, under the influence own strength gravity will tend to return to its original position and will enter an oscillatory (wave) motion. The bow and stern of the boat form interacting wave systems that have a significant impact on drag.
In swimming mode, the resultant of the hydrodynamic resistance forces is almost horizontal.
The shape of the displacement part of the seaplane (as well as the shape of the vessel) must ensure the ability to move through water with minimal resistance and, as a consequence, with minimal costs power ( speed of the vessel
, according to marine terminology).
When designing seaplanes (as well as ships), the results of tests by dynamic towing ("dragging") are used to select shapes and evaluate hydrodynamic characteristics similar models in experimental pools ( hydraulic channels
) or in open waters.
However, unlike a ship, the complex of seaworthiness characteristics of a seaplane is much broader, the main one being the ability to make safe takeoffs and landings on a rough surface with a certain wave height, while the speed of seaplanes on water is many times higher than the speed of sea vessels.
Due to the special shape of the bottom of the seaplane boat, hydrodynamic forces arise that lift the bow and cause a significant overall ascent of the boat.
Consequently, the movement of a seaplane, unlike a ship, occurs at a variable displacement and trim angle of the boat (in fact, the angle of the water flow on the bottom, similar to the angle of attack of the wing). At water speeds close to the take-off speed, the displacement is practically zero - the seaplane is in planing mode (from the French. glisser- slide) - sliding on the surface of the water. Feature planing mode
lies in the fact that the resultant of the forces of hydrodynamic resistance of water has such a large vertical component ( hydrodynamic
maintaining force
), that the boat for the most part of its displacement volume comes out of the water and glides along its surface. Therefore, the contours (outlines outer surface) seaplane boats (Fig. 7.81) differ significantly from the contours of the vessel.
The main difference is that the bottom (the bottom surface of the boat, which is the main supporting surface when the seaplane moves through the water) has one or more Redanov (French) redan- ledge), the first of which, as a rule, is located near the center of mass of the seaplane, and the second in the aft part. Redans straight in plan (Fig. 7.81, A) create significantly more resistance in flight than pointed (arrow-shaped, ogive) redans (Fig. 7.81, b), the hydrodynamic resistance and splash formation of which are significantly less. Over time, the width of the second level gradually decreased, interspace part of the bottom began to converge at one point (Fig. 7.81, V) at the stern of the boat.
In the process of development of hydroaviation, the shape of the cross-section of the boat also changed (Fig. 7.82). Boats with a flat bottom (Fig. 7.82, A) and with longitudinal steps (Fig. 7.82, b), weakly keeled (i.e. with a slight inclination of sections of the bottom from the central keel line to the sides - Fig. 7.82, V) and with a concave bottom (Fig. 7.82, G) gradually gave way keel boats
with a flat keeled bottom (Fig. 7.82, d) or with a more complex (in particular, curved) deadrise profile (Fig. 7.82, e).
It should be noted here that seaplanes do not have shock absorbers (see Section 7.3) that can absorb and dissipate the energy of impacts when landing on water. Since water is an almost incompressible liquid, the force of the impact on the water is comparable to the force of the impact on the ground. Main purpose deadrise
- replace the shock absorber and
gradual immersion of the wedge (keel) surface into water during landing to soften the landing blow, as well as the impact of water on the bottom of the boat when moving on a rough water surface.
The characteristic contours of a modern seaplane boat are shown in Fig. 7.83. The boat has a transverse and longitudinal deadrise on the bottom.
Transverse deadrise
boat (or the angle formed by the keel and chines) is selected based on the conditions for ensuring acceptable overloads during takeoff and landing conditions and ensuring dynamic directional stability.
Angle of transverse deadrise of the bow of the boat starting from the first step β р n gradually increases towards the bow of the boat (in front view A-A- superimposed sections along the bow of the boat) in such a way that a breakwater is formed in the bow of the boat, “breaking up” the oncoming wave and reducing wave and splash formation.
Cheekbone
(the line of intersection of the bottom and side of the boat) prevents water from sticking to the sides. To create acceptable wave and splash formation, a bend is used nasal cheekbones, i.e. profiling the bottom of the bow of the boat along complex curved surfaces.
Bottom of the interred part of the boat (rear view) B-B- superimposed sections along the stern of the boat) usually flat-keeled - angle value β r m constantly. The transverse deadrise angles at the step are usually on the order of 15-30°.
Longitudinal deadrise
boats γ l = γ n + γ m determined by the longitudinal deadrise angle of the bow γ n and the angle of longitudinal deadrise of the interred part γ m.
Length, shape and longitudinal deadrise of the bow ( γ n @ 0¸3°), affecting longitudinal stability and the angle of initial trim, are selected so as to prevent the bow from burying and flooding the deck with water at high speeds.
Longitudinal deadrise of the interred part ( γ m @ 6¸9°) is selected so as to ensure stable planing, landing on land at the maximum permissible angle of attack and landing on the water (for an amphibious aircraft) according to existing slips
(English) slip, lit. - sliding) - sloping coastal platforms extending into the water for the amphibian to descend onto the water and go ashore.
If the longitudinal deadrise of the inter-raft part is sufficient, lift-off during take-off from water can occur “with an explosion” (increasing the angle of attack) at the maximum permissible lift coefficient.
Taking off from the water during takeoff is complicated by the fact that in addition to the forces of water resistance to the movement of the boat, discussed above, adhesion (suction) forces act between the bottom of the boat and the water, especially in the rear of the boat.
Purpose of the redan- destroy the suction effect of water (suction) during take-off, thereby reducing water resistance, allowing the boat to “come unstuck”
Recently, Deputy Defense Minister Yuri Borisov announced that a new type of aircraft could be created for Russian aircraft carriers: short take-off and landing or full vertical take-off. On the one hand, there is no need to invent anything special: the corresponding machine - the Yak-141 - was created back in last years The USSR has proven itself well. But how much does the Russian fleet need such an aircraft now?
Airplane Yak-141. Photo: WikiMedia Commons
An airplane that can take off and land without a run has long been a dream of aviators: it does not require long runways, but a small area, like for a helicopter, is enough. This is especially important for military aviation, because airfields in combat situations are often destroyed by enemy attacks. For naval aviation, having long runways is all the more problematic, since their size is limited by the length of the ship's deck.
Meanwhile, the rearmament of the Russian armed forces also includes the construction of new aircraft-carrying cruisers. In connection with this, the military began to think: shouldn’t such ships be equipped with vertical take-off and landing aircraft?
It is worth noting that the Russian defense industry will not have to reinvent the wheel: it has accumulated colossal experience in in this direction. Suffice it to say that the famous An-28 passenger plane needed only 40 meters of runway to take off!
Vertical take-off combat vehicles in service with the Air Force Soviet Union there were also, for example, the Yak-38 attack aircraft; however, in tropical seas during long voyages of Soviet ships, its engines began to malfunction. However, a more modern development of the Yakovlev Design Bureau - the Yak-141 aircraft, intensive testing of which began in the late 80s, set as many as 12 world records for aircraft of its class! Alas, this unique aircraft did not survive the collapse of the USSR, and the program was carefully curtailed. However, incompletely: in the mid-90s, as part of the concluded contract, the American company Lockheed successfully applied the developments of the Yakovlevites to create the fifth-generation fighter-bomber F-35, among many of whose features (such as invisibility technology for locators) was the possibility of vertical take-off .
But foreign technology without its authors did not bring the Americans success comparable to the Yak-141: the vaunted super-fighter, as part of a test organized in the United States itself, lost a training battle to the almost antediluvian (originally from the 70s of the 20th century) F-16. True, the new Phantom did set at least one “record”: in terms of the high cost of its development program, which has already exceeded one and a half trillion dollars. So even President Trump, known for his respectful attitude towards the rearmament of the army, wondered whether the game was worth the candle. And the governments of Germany and France wisely chose not to purchase an expensive toy overseas, making do with their own reliable and proven fourth-generation aircraft, albeit without the possibility of vertical take-off. I think, first of all, because the last function in most cases is not so critically important.
Can the enemy bomb airfields? Also, the Soviet division commander Pokryshkin, during the battles in Germany, used a solid German autobahn as a runway for his air division. In addition, modern technology makes it possible to lay (and even more so repair) such roads in a matter of hours.
Is the deck of an aircraft carrier too short? But these ships entered wide application even before the Second World War, when there were no traces of any vertical take-off aircraft. Other tricks were used to take off and land conventional fighters and bombers.
Now vertical machines make up a rather small share of the existing aircraft fleet of aircraft-carrying cruisers. Including the Americans, where there seems to be no shortage of “verticals”. And all because the “miracle machines” themselves have shortcomings (and very significant ones).
The main one: the need to significantly reduce take-off weight so that the plane can lift off the deck vertically. In connection with this, for example, the only truly widely used model, the British Sea Harrier fighter, had a flight radius of a measly 135 kilometers. However, its speed, only slightly exceeding the speed of sound, was also not impressive.
Both the historical Yak-141 and the ultra-modern F-35 can reach a maximum speed of just under two thousand kilometers per hour, while a conventional carrier-based fighter Russian Navy Su-33 - 2300 kilometers. In addition, the range of the latter is many times greater than that of its “vertical” colleagues.
Finally, a vertical take-off and landing aircraft is much more difficult to pilot precisely because of the change in flight modes. Suffice it to say that one of the two prototypes of the Yak-141 crashed during testing precisely for this reason, despite the fact that at its helm was an experienced test pilot, and not an ordinary pilot.
The uncertainty in the words of the Deputy Minister of Defense “we are discussing the creation of an aircraft with short take-off and landing, possibly vertical take-off and landing” is quite understandable. On the one hand, the revival of the unique developments of the Yakovlev Design Bureau will not be a particular problem, except, of course, for the amount required for this. It is clear that it will be difficult to allocate additional billions of dollars for the Russian military budget. But most importantly, will the potential benefits be worth the effort? The competent authorities still have to think about this.
Despite the wave of criticism of the vertical take-off concept used in the aircraft, the need to resume production of aircraft of this class has recently become increasingly talked about in Russia December 15, 2017, 11:33
One of the Pentagon's most expensive "toys" - the F-35B fighter-bomber - this week took part in joint US-Japanese exercises aimed at cooling the DPRK's nuclear missile fervor. Despite the wave of criticism of the vertical take-off concept used in the aircraft, the need to resume production of aircraft of this class has recently been increasingly discussed in Russia. In particular, Deputy Defense Minister Yuri Borisov recently announced plans to build vertical take-off and landing aircraft (VTOL). About why Russia needs such an aircraft and whether the aviation industry has enough strength to create it.
The most popular domestic combat aircraft with vertical take-off and landing was the Yak-38, which was put into service in August 1977. The aircraft has earned a controversial reputation among aviators - out of 231 aircraft built, 49 crashed in accidents and aviation incidents.
The main operator of the aircraft was the Navy - the Yak-38 was based on the aircraft-carrying cruisers of Project 1143 "Kyiv", "Minsk", "Novorossiysk" and "Baku". As veterans of carrier-based aviation recall, the high accident rate forced the command to sharply reduce the number of training flights, and the flight time of Yak-38 pilots was a symbolic figure for those times - no more than 40 hours per year. As a result, there was not a single first-class pilot in the naval aviation regiments; only a few had second-class flight qualifications.
Its combat characteristics were also questionable - due to the lack of an on-board radar station, it could only conditionally conduct air battles. Using the Yak-38 as a pure attack aircraft seemed ineffective, since the combat radius during vertical takeoff was only 195 kilometers, and even less in hot climates.
Supersonic multi-role vertical take-off and landing fighter-interceptor Yak-141
The “problem child” was supposed to be replaced by a more advanced vehicle, the Yak-141, but after the collapse of the USSR, interest in it disappeared. As you can see, the domestic experience in creating and operating VTOL aircraft cannot be called successful. Why has the topic of vertical take-off and landing aircraft become relevant again?
“Such a machine is vital not only for the Navy, but also for the Air Force,” military expert, captain first rank Konstantin Sivkov told RIA Novosti. “The main problem of modern aviation is that a jet fighter needs a good runway ", and there are very few such airfields; destroying them with a first strike is quite simple. Vertical take-off aircraft during a threatened period can be dispersed even across forest clearings. Such a system for using combat aircraft will have exceptional combat stability."
However, not everyone sees the feasibility of using VTOL aircraft in the land version as justified. One of the main problems is that during vertical takeoff the aircraft consumes a lot of fuel, which greatly limits its combat radius. Russia is a large country, therefore, to achieve air supremacy, fighter aircraft must have “long arms.”
“The implementation of combat missions of fighter aircraft in conditions of partially destroyed airfield infrastructure can be ensured by short take-off of conventional aircraft from a section of the runway less than 500 meters long,” says Oleg Panteleev, executive director of the Aviaport agency. “Another question is that Russia has plans for the construction aircraft carrier fleet, here the use of vertically taking off aircraft will be most rational. These may not necessarily be aircraft carriers, they may also be aircraft-carrying cruisers with the lowest cost parameters."
F-35 fighter
By the way, the F-35B today is a purely naval aircraft, its main customer is the US Marine Corps (the aircraft will be based on landing ships). British F-35Bs will form the basis of the air wing of the newest aircraft carrier Queen Elizabeth, which was recently commissioned.
At the same time, according to Konstantin Sivkov, Russian design bureaus do not have to wait for new aircraft carriers to begin work on creating a Russian analogue of the F-35B. "Vertical take-off and landing aircraft can be based not only on aircraft carriers. For example, a tanker is equipped with a ramp and becomes a kind of aircraft carrier; in Soviet times we had such projects. In addition, VTOL aircraft can be used from warships capable of receiving helicopters, for example frigates,” our interlocutor said.
Meanwhile, it is obvious that the creation of a Russian vertical take-off aircraft will require impressive resources and funds. The cost of developing the F-35B and its horizontal take-off cousins, according to various estimates, has already reached $1.3 billion, and several countries participated in the creation of the vehicle.
