How Marine Flottille 32F inspired the first helicopter deck landing assistance

Influenced by the Flottille 32F,an NY engineering office released its militarized helipad's landing assistance converted for yacht and civil flight desk ops.

NAVY FLIGHT DECK OPS
State of the art

H istorically, different categories of naval forces can be defined of the type of aircraft carriers they own, conditioning the types of aircraft on board as well:

  • Warship, the declination of aircraft carrier, carry only helicopters and aircraft with vertical takeoff. These warships are cheaper to buy and use that the more massive aircraft carriers, but the planes carry only low loads useful and limited to action due to consumption the vertical phases of flight.
  •  Aircraft carrier with take-off springboard and strand landing , STOBAR ( Short Take-off But Arreted Recovery ), generally have vertical take-off or conventional aircraft . However, they can not take off at full load because take-off requires a great thrust.
  • Finally, aircraft carrier with take-off by catapults and landing by strand, CATOBAR ( Catapult Take Off Barrier-Assisted Recovery )

To maintain the performance of an aircraft on land, with certain restrictions, due to the landing constraints ( symmetrical distribution of the airports of the aircraft ). Other countries than the Western Powers have carriers. There are still a few for years, they are second-hand purchases from NATO or Russia. Since emerging countries such as China, India or Brazil and begin to develop the capacity to build aircraft carriers.
China had bought a Ukrainian aircraft carrier, the Varyag, officially to make it a floating casino. He became an aircraft carrier for training,with which the Chinese navy became familiar with naval operations and concepts
Employment during the fiscal years. Similarly, some analyzes refer to the construction a group of three aircraft carriers by 2020 that would be largely "inspired" by this aircraft carrier. In order to arm these air groups, China developed the J-15, a copy of a Sukhoi Su-33 bought in 2001 from the Ukraine. But the Chinese navy also sees in the longer term, prospecting to UAVs. In October 2011, a competition organized by the Chinese company AVIC and the association UAU drone, concerned the automatic landing on aircraft carriers. Of course, they were only models and the results were still modest but

Which demonstrate a desire to acquire experience in the naval technological mastery.
A punchline in the conditions of this race participation reinforces its interpretation and can echo:  our vision landing system. 

Any guidance systems aside from DGPS and GPS are encouraged for naval ops

Because of its rivalry with its neighbor Pakistan, India has long been a naval power and is reinforced with a Russian aircraft carrier STOBAR, Admiral Gorshkov, now Vikramaditya, which has been profoundly altered. Another project led by India, based on an English concept, will give three Vikrant aircraft carriers over this decade. They will embark a heterogeneous fleet of Sea Harrier, Mig-29K and Indian aircraft Tejas. It should be noted that after the selection of the Rafale for the exclusive negotiation of a contract of 126 aircraft for the Indian Air Force, this combat aircraft was recently given for take-off compatible on aircraft carriers with springboard.
Brazil, with oil reserves off its coast, has been claiming its power for some years. To do this, it has expanded its navy and has a carrier group of Sao Paulo (ex-Foch) equipped with A-4 aircraft. This carrier group is aging and obsolete,
Which is why different projects evoke two new aircraft carriers to replace it in the coming years.
The first aircraft carrier of the next generation of US aircraft carriers is being manufactured, they will be of the Gerald R. Ford class. They will have a redesigned architecture compared to the previous generation Nimitz and will be equipped with electromagnetic catapults.
In addition, they will see the embarkation of combat drones and the generation of combat aircraft following the fighter-bomber F-18, the very expensive F-35 not necessarily appearing optimal for the US Navy.

FLOTTILLE 32F

Casual meeting snapshot - January 23 2013, Middle School of Chambourcy, France.

Xavier-Stanislas Azzis Flottille 32F Marine Commander and JBL¹ from Manhattan² hold discussion about the offshore's mission under the minister of the flottille 32F. According JBL, development of C18 converter would increase visibility of the TLOF boundaries from warship in bad weather with also a self-reactive guidance. A witness says the officer s' wonder about the efficiency level during operation on sea in order to relative speed of the warship.

Also according to JBL who seizures the Department of Defense² a year earlier on this purpose, demonstration could be made in 1/5 scale. The two men share contact information and the officer said that this device should be promised to a great future if realized.

Squad Snapshot

Flottille 32F
Base aéronautique navale
Lanvéoc-Poulmic
FRANCE
www.defense-gouv.fr

ELISA new york
elisa aeronautics

Native principles of deck-landing
B y good weather as the visual clues are reliable, the pilots work close to the aircraft carrier during this visual approach. Thus, they make a first passage along the route of the ship, pass it by the right, make a U-turn and realign themselves on the axis of the track by starting the final descent.
In case of poor visibility, the trajectory begins much further and is called the Carrier Control Approach (CCA). This trajectory is longer due to a necessary period of adaptation between instrument flight and the visual acquisition of the optics and the difficulty of landing by low visibility or night. The two approaches share the same final phase, consisting of a constant descent slope by order of 4° compared to the carrier, for a wind on the bridge = 10m/s. For the final phase, the difference between the two approaches is the duration of this phase which is much longer for the low visibility approach. For the descent phase, the principle applied by operators consists in maintaining the same aerodynamic slope γ whatever the wind speed on bridge, composed by the speed of the aircraft carrier Vpa and that of the wind Vw. This principle makes it possible to keep the aircraft in a flight zone where its behavior is stabilized. The impact on the bridge is rounded.
This is intended to ensure a precise impact and to hook the landing stick to one of the three strands placed across the track and which will serve to decelerate the aircraft by evacuating its kinetic energy in pistons. Some even dare to call the landing of the name a little exaggerated of "controlled crash".
The final trajectory is designed to meet several constraints: precision of the point of impact on the bridge, vertical speed in order to limit the forces of the landing gear of the aircraft, horizontal speed for the strands and height at the stern in order to limit any risk of premature impact due to a rotational movement of the aircraft carrier. At the moment of the impact, the last action of the pilot is to put full gas in order to provide for a possible bolter and thus be able to re-launch. To treat the effect called divergence, the method used by the pilots consists in imposing a non-zero relative heading to compensate for the lateral velocity.

Encountered difficulties

A landing on the deck is already a delicate phase, the proximity with the ground requiring to react quickly. Several factors complicate this last part of the flight. In many situations, the landing is carried out at the end of a mission which may have lasted a few hours, resulting in physical and intellectual fatigue of the pilot, who was confronted with the movements of the aircraft and accomplishment of his mission . In addition, one can imagine a return of an airplane in limit of dry or damaged breakdown in the most extreme cases. However, in the majority of mission returns, the difficulties relate more to restricted visibility, aircraft carrier movements and the wake of the warship.

Visibility

The external visibility of the cockpit, whether affected by the time of flight or climatic conditions, is a factor affecting the quality of the landing. FIG. 1 presents a set of images from an on board camera, with an estimated field of view at forty degrees. They were provided by the DGA with the help of the French Navy and recorded during four flights with different visibility conditions and for three given instants of the approach. Regarding the night flight, it can be observed that the trajectory is different from those of the other flights.

Indeed, in this case, given the low visual feedback for the pilot, a breakthrough is carried out well upstream of the aircraft carrier in order to arrive aligned at the beginning of the descent, as, where the Charles de Gaulle lights appear center at the bottom of the image. The three videos taken during the day allow to appreciate the differences of visibility of the building according to the climatic conditions.
In the case of flights in good weather and with clouds, the contours of the ship are visible while the carrier is clearly less discernable in the video with fog. On the sequence of the landing at night, there is only the lights of the carrier to provide an appreciation of the situation.
The stress and concentration of the driver obviously do not appear on these images but they are clearly felt on the sequences provided with a sound track and especially on the night sequence. Indeed, one hears strongly the accelerated respiration of the pilot during the alignment and the descent which ends with a deep sigh once the aircraft impacted and retained by the strands.

FIG. 1

Rare direct visual clues

T he visual information used during the landing takes up only a fraction of those used during conventional runway landings and presents a synthesis.
Depth analysis of human modeling in landing control and distinguishes three types of models used to characterize a pilot's behavior. We shall take up these three models and consider the possibility of applying them to landing:

  • The first model relies on the optical flux of the scene on pilot's retina, linked to its own displacement. The scrolling of the landscape surrounding the runway makes it possible to apprehend certain information related to the direction and speed of travel and even to the rate of descent. Thus, this model works well when the textures of the scene offer sufficient information to evaluate the scrolling. In the case of landing, the aircraft carrier is small in size and is surrounded by water. Depending on the state of the sea and flight altitude, the optical flux is disturbed by either a lack of texture of the scene or a scene whose texture is moving, with a distinction of the details of the dependent scene Of the altitude of the aircraft. For this, this first model is not entirely satisfactory for our application.
  • Can be considered as a derivative of the optical flow, the model is based on the angle ratio between two points of the image and the derivative of this angle. This model, in the case of landing, is mainly related to the triggering of the rounding phase which makes it possible to go from a non-zero downward slope to a touch of the track at almost zero vertical speed. This model is quite controversial in the perception community, because it is not directly perceived, but dependent on other clues. In addition, in the case of landing, no rounding phase. Therefore, this model is not suitable for our application.

  • The last model uses characteristic elements of the image, often geometric, commonly called visual cues. These indices appreciate the distance between pilot and airstrip with objects of the scene whose size is known as well roads, cars, trees or buildings. Other indices such as the angle θ formed by the two edges of the airstrip or the distance Y between the points of impact and leakage serve for the longitudinal control.
    For the lateral control, one can cite the angle of the horizon φ for the roll; And the angle of the ψ airstrip center line for heading control. This information has been studied since 1972. These studies establish, with the hypothesis of small angles, the relations linking vertical, lateral and visual positions.
    Different relationships related to this form are analyzed in order to determine which one gives the best perception to the pilot of the slope followed.

In addition to the optical illusions associated with desk landing, some others complicate the landing task. In our application, the only objects that the pilot knows are the aircraft carrier, the airplanes on it and the marking of the airstrip. This track is also very small in size compared to a land track. Indeed, it is characterized by a much smaller ratio of length and width than that of land tracks, which leads to a certain difficulty in apprehending its relative orientation and position. Moreover, the horizon that the pilot sees is that of the sea, and is not linked to the bridge, which is subjected to the pitching and rolling movements of the aircraft carrier.

To fill this lack of visual cues, passive and active devices are present on the aircraft carrier.

DECK LANDING ASSIST
In order to improve the operational yield

Passive interaction device

P  assive assistances are mainly composed by the airstrip markings and all elements related to the geometry of the building which will increase quality of the eyes perception. To track the vertical trajectory, a triangle-shaped markup is placed at the end of the track. It is used as a visual cue on which the pilot must place two reticles displayed on his HUD: the slope mark and the speed vector.

The difference between the slope marker and the base of the test pattern a static appreciation of the positioning with respect to the trajectory while the difference of the velocity vector and the base of the test pattern provides a trend information to pilot. On a concrete case as presented (taken from the camera embedded on the Rafale, positioned behind the HUD, the corresponding position and speed. The aircraft is above the desired trajectory and pilot corrects by pointing his velocity vector below the base of the sight, in order to return to the correct trajectory.

This method has the advantage of being very precise and not sensitive to pitch variations because the test pattern is located near the pitch axis of the aircraft carrier. However, in difficult climatic conditions with large platform movements, it does not take into account the constraint of the rounding guard and leads to oscillations around the desired descent trajectory.

For alignment, the axis and the edges of the track provide information as in the case of a land track but less representative of its relative position and orientation due to the short length of the runway. The perception of the lateral gap can be reinforced by the drop line, a vertical line located at the stern of the ship. The break in desk axis and drop line makes it possible to appreciate very precisely the lateral error.

Under the influential encounter with the Flottille 32F, Elisa refined the content of its C18 experimental protocol which initially allows passive marking to convert into active visual clues.
The protocol not only integrates a lighting equipment optimizing the naked eye spatial referencing but it released its operational usefulness in bad weather condition by taking advantage of a real time guidance system even compatible with rotary wings.

Passive visual clues to air navigation shell 2011 Patent modified winter 2013 through Flottille 32F

Active landing assistance

On all modern aircraft carriers, a landing mirror is positioned on the port side at three quarters of the airstrip. It is adjustable according to the aircraft on approach and wind conditions on the desk. This mirror provides a reference on the vertical path to pilot. That one of Charles de Gaulle is composed of a horizontal line of green lamps, materializing the slope to be followed, and six modules. These modules are used to indicate the position of the aircraft relative to the slope to follow. The mirror has different settings in inclination and position in order to make the plane with constant aerodynamic slope appear.
In addition, it is stabilized to cancel, as much as possible, pitching and rolling. If the main mirror is inoperative or if the climatic conditions are really critical ( pitching and rolling around 1◦ and 2◦ respectively ), there is an emergency mirror, manually controlled by the landing officer.
These active aids are useful to the pilot but are necessarily complemented by the presence of a landing officer on port,
Possibly wave-off commands ( disengagement of the approach phase ). It is of paramount importance for operations. Its behavior has even been recently modeled to include it in a simulation environment. To assist in monitoring the airplane's trajectory, a system called DALAS is present. It consists of a camera in the visible area, a Murene camera in the infrared range and a laser. The laser provides the telemetry-distance-meter function with respect to the desired trajectory; It follows the reflector installed on the front axle of the aircraft. It is very accurate for the estimation of the position or the speed, besides, it was considered for a time to use it for an automatic landing system. However, it is sensitive to climatic conditions. Monitoring based on vision sensors is also used in degraded modes of DALAS. You can see a reticle with the trajectory to follow.
Note the low precision in the final trajectory due to a parallax defect. A system equivalent to DALAS has been studied for Chinese aircraft carriers.
Note also the use of night vision glasses with intensification of light and FLIR ( Forward Looking InfraRed ) sensors in the US Navy. It has been envisaged to use infrared optronics for landing in an operational framework for the future American fighter F35 with its optronic DAS ( Distributed Aperture System ). However, the visibility is still significantly reduced by difficult climatic conditions and the spatial resolution of the front sensor used for landing is not large enough and offers no significant advantage over vision sensors Night.
In addition, a potentially problematic point is related to human factors. Indeed, the infrared representation is quite different from that of the visible, and questions arise about the ability to move quickly from one to the other. For example, the markings on the flight deck are distinctly less although visible.

YACHT HELIPAD CONVERTER
Military desk landing assistance adapt for civilian ship
ELISA

Elevated Helipad light equipment for yacht. Prescriptive illustration

US Elisa aeronautics

 Droneship Conversion R&D for yacht and offshore implantation. Prescriptive illustration

A utomatic landing is now well detailed in ground for helicopters and more especially for drones; Often shipped on warship, maneuvers are more subject to the elements that require a specialized landing system. Lot of studies have focused on this application. The EADS Astrium Deckfinder system uses electromagnetic beacons positioned on the frigate so that the helicopter drone calculates its relative position. Thales² D2AD system relies on another technology to estimate its relative position: a beacon is mounted on the helicopter and receivers on the ship. ELISA C18 Helipad / Droneship converter system develop a 3D illustration signals emitted beyond 3500 feets from the entire shell. This electroluminescent organs linked with an affinity of many sensors to a CPU called Symbiote², estimates the position of aircraft and warship as well as the weather forecasters.
From knowledge of the FAA², this system is the first to use electroluminescent painting to perform helicopter landing on a ship in a quasi-operational way.

Automatic locking devices have been in place in the US Navy since the Mid-fifties in prototype stage, and were then operated operationally in the early sixties. To improve reliability and manage of the components's obsolescence, some parts of the system have been redesigned.
Nevertheless, C18 system inspired by the Flottille 32F is based on the same principle: The aeronautical marking in the outer shell of the yacht is converted into heliport light equipment and connected to a management unit itself composed of by a machine learning². Two radars on the ship follow the aircraft in azimuth and elevation. Taking into account the corrections due to boat movements, PAPI² is calculated by the symbiote and simultaneously displayed on the yacht's hull and sent to the aircraft by UHF radio link, the pilot undertaking to apply them in case of electronic failure. There are three system modes ranging from the simple ( but very large ) light beaconing of the helipad to landing visual assistance with display of meteorological database.
In the future, C18 ELISA system, like other terrestrial and maritime navigation systems, will be replaced by a differential GPS and will be able to acquired new abilities.

Source: Coutard, JBL
University: ENCPB, IEJ, CHUPS
Illustration: Elisa, NXDesign

Flottille 32F
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