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Aviation, Technology, Hungary, United Kingdom, History.
then the majority of the current might start flowing down a path with lower resistance instead. Now imagine that the flap operation circuit is energized with the grounding screw no longer connected to the chassis. What’s the path of least resistance back to the battery now? What other path to | medium | 2,692 |
Aviation, Technology, Hungary, United Kingdom, History.
ground exists? The failure mode that caused the crash of HA-LAJ. (AAIB, annotations mine) In fact, with the grounding screw pulled out sufficiently far, the main current will flow from the flap circuit, into terminal block A6X1, then — skipping the screw entirely — up the feathering circuit | medium | 2,693 |
Aviation, Technology, Hungary, United Kingdom, History.
grounding wires, across the normally closed side of the feathering switches, through the feather circuit wiring, past the 7-K6 feathering relays, and out through the normal grounding points for the feathering circuits. This path is depicted above. If the resistance between the screw and the chassis | medium | 2,694 |
Aviation, Technology, Hungary, United Kingdom, History.
was sufficiently high, then enough current could flow down each feathering circuit to activate both 7-K6 feathering relays, causing both propellers to feather simultaneously. This is in fact what happened as the pilots of HA-LAJ retracted the flaps at 500 feet on their 13th parachuting flight. As | medium | 2,695 |
Aviation, Technology, Hungary, United Kingdom, History.
soon as the feathering relays were energized, a command was sent to the blade pitch controllers to feather the propellers and hold them there. Then, because the propellers provide no thrust when feathered, the An-28’s engine failure detection system detected a loss of thrust in both engines, | medium | 2,696 |
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causing a number of knock-on effects. The An-28 has a fairly sophisticated engine failure detection system that automatically shuts off fuel to the engine when a large discrepancy is detected between the power lever position and certain engine operating parameters. Furthermore, because a failed | medium | 2,697 |
Aviation, Technology, Hungary, United Kingdom, History.
engine on the An-28 tends to produce a large and sudden yawing moment, the system also automatically deploys the outboard wing spoiler on the opposite side from the engine failure, in order to ensure that drag on both sides is as close to equal as possible. This makes the plane easier to control | medium | 2,698 |
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with one engine inoperative. However, in this case, when the engine failure detection system registered the loss of thrust in both engines, it not only cut fuel to each engine but also deployed the outboard spoilers on both wings, because the left engine failure triggered the right spoiler, while | medium | 2,699 |
Aviation, Technology, Hungary, United Kingdom, History.
the right engine failure triggered the left spoiler. This was consistent with the system’s operating logic but was nevertheless completely unnecessary, because deploying both spoilers simultaneously just increased drag on the airplane while providing no controllability benefits. The pilots of | medium | 2,700 |
Aviation, Technology, Hungary, United Kingdom, History.
HA-LAJ had no idea that any of this was about to occur. Instead, it felt almost like the flap switch had suddenly turned into a “crash airplane” button. At the same instant that the flaps were retracted, both propellers feathered, fuel was cut to both engines, and both spoilers deployed, causing a | medium | 2,701 |
Aviation, Technology, Hungary, United Kingdom, History.
catastrophic loss of both thrust and lift. The plane began to decelerate rapidly, forcing Captain Suskin to push the aircraft into a dive in order to maintain airspeed. If he tried to reduce their descent rate, it was certain that they would lose speed and stall, leading to a devastating crash. But | medium | 2,702 |
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the other outcome didn’t look rosy either. They obviously didn’t have enough height to return to the airfield, but the terrain was littered with obstacles like trees, ditches, and roads. With only seconds to act, Suskin and his First Officer made a snap decision to turn to the right and land in a | medium | 2,703 |
Aviation, Technology, Hungary, United Kingdom, History.
field of recently harvested corn stubble. There was no time for a brace call, but the parachutists didn’t need one — it was obvious that they were going down, and all they could do was hang on for dear life, since the plane didn’t have seat belts. The wing attachment points failed during the ground | medium | 2,704 |
Aviation, Technology, Hungary, United Kingdom, History.
slide but the fuselage remained intact. (AAIB) Moments later, HA-LAJ touched down hard in the cornfield, with a considerable descent rate, a slight right bank, and a nose high attitude with a forward airspeed of 92 knots. The landing gear swiftly collapsed, causing both wings to fold downward and | medium | 2,705 |
Aviation, Technology, Hungary, United Kingdom, History.
strike the ground, but within just a few seconds the plane slid to a stop on its belly, otherwise intact. When the plane came to a halt, the 19 passengers and crew discovered that despite the lack of restraints, everyone had survived the crash landing, and in fact no one was even seriously injured. | medium | 2,706 |
Aviation, Technology, Hungary, United Kingdom, History.
Furthermore, no fire broke out, and egress was trivial because of the removed rear doors. By the time the pilots had shut down the plane’s remaining systems, all the passengers were already off the airplane with no need for an evacuation call. Subsequently, the First Officer was the last person | medium | 2,707 |
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off, exiting through the cockpit window after stopping to disconnect the battery. Emergency services arrived shortly thereafter, but there was little for them to attend to. ◊◊◊ The A6X1 terminal block as it was found after the accident. (AAIB) Because the crash was minor and occurred over a bank | medium | 2,708 |
Aviation, Technology, Hungary, United Kingdom, History.
holiday weekend, Britain’s Air Accidents Investigation Branch didn’t begin an investigation until three days later. Nevertheless, when the investigation did get underway, it resulted in a number of fascinating findings. Although both pilots had already returned to Russia by the time the AAIB got | medium | 2,709 |
Aviation, Technology, Hungary, United Kingdom, History.
there, investigators were able to obtain statements from both through the Russian Department of Air Transport, in which they described how the propellers feathered, the engines shut down, and the spoilers deployed when they attempted to retract the flaps. The deployment of the spoilers and | medium | 2,710 |
Aviation, Technology, Hungary, United Kingdom, History.
feathering of the propellers was confirmed not only by the condition of the wreckage, but by a photograph of the airplane in flight, taken shortly before impact by a nearby witness. My understanding is that this photo remains the property of the photographer and has not been released. Because the | medium | 2,711 |
Aviation, Technology, Hungary, United Kingdom, History.
An-28 was designed in the Soviet Union, and because Russia had inherited the USSR’s obligations, investigators from Russia participated in the inquiry, and in fact they were the first to identify a possible mechanism by which the pilots’ command to retract the flaps could have triggered the | medium | 2,712 |
Aviation, Technology, Hungary, United Kingdom, History.
observed failures. Their suspicions were subsequently proven right when on-scene measurements by the AAIB detected elevated electrical resistance when the flap operating circuit was energized. Subsequently, the grounding screw connecting terminal block A6X1 to the chassis was found loose, having | medium | 2,713 |
Aviation, Technology, Hungary, United Kingdom, History.
unscrewed itself slowly over time. Another image of the airplane, taken shortly after the crash by what I assume to be one of the passengers. (Unknown author) Meanwhile, the AAIB began to uncover a number of facts that raised questions about why HA-LAJ was allowed to fly parachutists at | medium | 2,714 |
Aviation, Technology, Hungary, United Kingdom, History.
Weston-on-the-Green in the first place. One glaring issue was brought to light by representatives of the Antonov aircraft company — namely, that the An-28 was never intended for parachuting operations, was not approved for that purpose, and was never tested or certified to fly with the rear | medium | 2,715 |
Aviation, Technology, Hungary, United Kingdom, History.
clamshell doors removed. Representatives of the Russian Department of Air Transport expressed the same views. This contradicted the plane’s Hungarian airworthiness certificate, which stated that HA-LAJ was approved for flight in that configuration. In fact, the operation of the aircraft without the | medium | 2,716 |
Aviation, Technology, Hungary, United Kingdom, History.
rear doors so alarmed the representatives of Antonov that the final report on the accident describes their statements against the practice as “categorical” and “emphatic.” Elaborating further, Antonov personnel told the AAIB that the An-28 had never been tested for adverse strength, metal fatigue, | medium | 2,717 |
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or flight characteristics without the doors, and that in their view turbulence with the doors removed could result in structural damage to the airplane. However, investigators also wrote that Antonov was strongly opposed to accepting any “liability” — which does make one wonder how much of this | medium | 2,718 |
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response was out of genuine concern, and how much was an attempt to deflect responsibility for the design decisions that caused the crash, which I’ll cover in more detail in a moment. Another issue that came up was of course the registration of the airplane in two different countries | medium | 2,719 |
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simultaneously. This lapse was accidental, but investigators noted that had Hungarian authorities informed their Russian counterparts of the new registration, as was their obligation, then they would have been required to provide information about the aircraft to the Russian Department of Air | medium | 2,720 |
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Transport. Since this agency was apparently aware that the aircraft was not approved for parachuting operations, it’s possible that they might have brought the discrepancy to the Hungarians’ attention had this required step been completed. Lastly, and perhaps most importantly, investigators also | medium | 2,721 |
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examined the process by which HA-LAJ was granted permission to fly in the United Kingdom. Under UK law at the time, in order to hire a foreign aircraft to perform “aerial work,” including parachuting, it was necessary to apply for explicit approval from the Department of Transportation. After | medium | 2,722 |
Aviation, Technology, Hungary, United Kingdom, History.
demonstrating that no UK-based company could perform the work in question, the Civil Aviation Authority’s Safety Regulation Group–Operating Standards Division was required to verify, among other items, that the aircraft was currently being used for the specified type of work in its home country; | medium | 2,723 |
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that the crew were competent and qualified; and that there was a parachute operations supplement to the Flight Manual. Submission of the aircraft’s certificate of airworthiness and the certificate of the operating company were also required. In the case of HA-LAJ, there was no question about the | medium | 2,724 |
Aviation, Technology, Hungary, United Kingdom, History.
competence of the crew or the presence of the correct documents, and the aircraft had previously conducted parachuting flights in Hungary, so the permit was issued. However, the CAA failed to discover that the An-28 was not approved for parachuting operations, because there was no requirement to | medium | 2,725 |
Aviation, Technology, Hungary, United Kingdom, History.
consult the manufacturer as long as HA-LAJ’s certificate of airworthiness indicated such an approval, which it did. The AAIB was therefore concerned that the verification process had become a rubber stamp, causing discrepancies to be missed. In a worst-case scenario, it might even have been | medium | 2,726 |
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possible for an applicant to hoodwink the CAA simply by inserting false approvals into the submitted documentation. As a result, the AAIB recommended that the CAA Safety Regulation Group consider checking directly with the states of design, manufacture, and registry of aircraft from the former USSR | medium | 2,727 |
Aviation, Technology, Hungary, United Kingdom, History.
before giving them permits for aerial work in the UK, in order to verify the documentation. ◊◊◊ Two possible design features that could have prevented the accident. (AAIB, annotations mine) However, perhaps the most interesting part of the AAIB’s report on the accident was its analysis of the | medium | 2,728 |
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design of the An-28’s electrical system. Unsurprisingly, the AAIB wrote that the use of a common grounding point for several systems, whose failure could cause the uncommanded shutdown of both engines, was “not sound design philosophy.” Some consolidation of grounding points is desirable in order | medium | 2,729 |
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to reduce the number of stray currents flowing through the aircraft chassis, but care must be taken to ensure that single points of failure are not created. The ideal configuration would have been to isolate the safety-critical autofeather circuit from all other systems by grounding the normally | medium | 2,730 |
Aviation, Technology, Hungary, United Kingdom, History.
closed side of the feather switches at a separate location. Alternatively, devices called reverse current diodes could have been installed on the wires connecting the normally closed sides of the feather switches to the terminal block. A reverse current diode ensures that current can only flow in | medium | 2,731 |
Aviation, Technology, Hungary, United Kingdom, History.
one direction, which in this case would be from the switches to ground, while preventing current flow from ground to the switches. The AAIB pointed out, rather incredulously, that use of reverse current diodes on aircraft had been the standard means of protecting critical systems from stray | medium | 2,732 |
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currents since the 1950s. The accident aircraft did have some reverse current diodes in certain locations, but investigators observed that their use was not systematic. It’s also worth mentioning an issue that I previously discussed in my article on Capital Airlines flight 20 — namely, the | medium | 2,733 |
Aviation, Technology, Hungary, United Kingdom, History.
isolation of the autofeathering systems for each engine, so that only one propeller may feather at a time. Isolating these systems has been standard since the late 1950s, so I would presume that the An-28 had some sort of interlock that should prevent both propellers from autofeathering | medium | 2,734 |
Aviation, Technology, Hungary, United Kingdom, History.
simultaneously. The AAIB’s diagram of the An-28’s feathering switches shows a feature that might be an interlock, although it’s not labeled. If so, then the interlock appears to function by ensuring that the remaining switch cannot activate if one switch is active already. This design would have | medium | 2,735 |
Aviation, Technology, Hungary, United Kingdom, History.
been fine, except that in this accident scenario it was rendered useless, because the current entered the feathering circuits through the normally closed side of the switches, energizing the feathering relays without either switch ever activating. Note: After publication, readers pointed out to me | medium | 2,736 |
Aviation, Technology, Hungary, United Kingdom, History.
that the lack of any retention mechanism on the grounding screw was a design flaw as well. Throw it on the pile! The Antonov design engineers’ original intention, according to the original design drawings. (AAIB, annotations mine) Although the AAIB didn’t have access to the personnel involved in | medium | 2,737 |
Aviation, Technology, Hungary, United Kingdom, History.
the An-28’s design and manufacturing process, they were able to examine Antonov’s original design drawings, which contained interesting differences from how the plane was actually built. Whereas on the actual aircraft the two wires M01 and M02 connected the A6X1 terminal block to a common grounding | medium | 2,738 |
Aviation, Technology, Hungary, United Kingdom, History.
screw, the original drawings depicted these wires connecting to separate grounding screws. The intention presumably was that if one screw failed, the systems attached to A6X1 would remain safely grounded via the other. However, the AAIB pointed out that while two grounding screws were better than | medium | 2,739 |
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one, this was still far from an ideal solution because there was no way to detect if one screw was no longer grounding correctly. This condition could therefore persist indefinitely until the second screw also failed, causing an accident anyway. In its final report, the AAIB wrote that “widely used | medium | 2,740 |
Aviation, Technology, Hungary, United Kingdom, History.
design principles for identifying common failure modes… should have revealed the potential hazard.” Investigators pointed out that common failure mode analysis techniques had been used in the West since the 1950s, and more complex fault tree analyses since the 1960s. The fact that the AAIB took the | medium | 2,741 |
Aviation, Technology, Hungary, United Kingdom, History.
time to mention these dates underscores the investigators’ apparent confusion over how such a blatant design flaw could have made it into an aircraft that entered service only in 1986. Investigators wrote that they didn’t know what failure analysis techniques were in use in the USSR when the An-28 | medium | 2,742 |
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was designed, but that in any case such techniques evidently were not applied to the system in question — or if they were, then it was certainly before the decision to reduce the number of grounding screws on terminal block A6X1 from two to one. The fact that the original design drawings included | medium | 2,743 |
Aviation, Technology, Hungary, United Kingdom, History.
two separate grounding screws indicated that Antonov engineers were aware of the need for redundancy in this area, even though their solution was suboptimal. That this design was changed prior to production, apparently without any further analysis, may have been symptomatic of the way aircraft | medium | 2,744 |
Aviation, Technology, Hungary, United Kingdom, History.
design and manufacturing were organized in the Soviet Union. Although Antonov today is an independent company that designs and builds its own aircraft, under the USSR it was a “Design Bureau,” which was responsible for the aircraft design phase only. The AAIB report mentions that once the drawings | medium | 2,745 |
Aviation, Technology, Hungary, United Kingdom, History.
left Antonov’s headquarters in Kyiv, the design bureau “ceased to have total control over the production standard,” because the production engineering and assembly phases were handled by different organizations within a ministry-level umbrella. That meant that the engineers responsible for building | medium | 2,746 |
Aviation, Technology, Hungary, United Kingdom, History.
Soviet aircraft often had limited communication with the engineers responsible for designing them. In contrast, a traditionally organized Western manufacturer such as Boeing has design and production engineers under the same roof. Production of many components may be outsourced, but Boeing and its | medium | 2,747 |
Aviation, Technology, Hungary, United Kingdom, History.
suppliers sign contracts stipulating the specifications of the systems being produced, and the supplier must inform Boeing of any intent to deviate from those specifications if they want to avoid being sued. Such safeguards are obviously imperfect, but the Soviet Union lacked even these. As a | medium | 2,748 |
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result, Soviet planes were more likely to suffer from design flaws introduced at the production stage, which is a problem I previously discussed in my article on LOT Polish Airlines flights 007 and 5055. The An-28 would have been particularly vulnerable to this type of mistake due to its abnormally | medium | 2,749 |
Aviation, Technology, Hungary, United Kingdom, History.
long and uneven development process. ◊◊◊ Another view of HA-LAJ after the crash. (Alan Bushell) In 1993, the aviation industry in the West still had little knowledge of most Soviet aircraft types, and the strengths and weaknesses of those types were not widely known there. An An-28 from Hungary | medium | 2,750 |
Aviation, Technology, Hungary, United Kingdom, History.
could not have been hired to perform work in the UK before about 1990, and neither the CAA nor the intended users knew much, if anything, about the circumstances under which it was built. Despite this, the CAA could allow such an aircraft into the UK to perform work with UK nationals on board | medium | 2,751 |
Aviation, Technology, Hungary, United Kingdom, History.
without any particular scrutiny, because Hungary (the state of registration), Poland (the state of manufacture), and the USSR (the state of design) were all members of the International Civil Aviation Organization and were expected to uphold that organization’s minimum safety standards. Today, some | medium | 2,752 |
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countries such as the United States are able to audit the extent to which each other country is adhering to ICAO standards, but in 1993 this type of auditing was a very new concept and it doesn’t seem that the UK was doing it. The AAIB wrote that the An-28 as built did not meet ICAO standards | medium | 2,753 |
Aviation, Technology, Hungary, United Kingdom, History.
requiring that aircraft be designed to minimize the probability of inadvertent operation of systems affecting flight controls and powerplants. It was unclear to the investigators whether or how Antonov addressed these ICAO standards during the design process. And yet the UK CAA was required to | medium | 2,754 |
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trust that these standards were met without any direct verification. Such oversight would only be provided if the aircraft were leased to a company with a UK Air Operator Certificate, which HA-LAJ was not. As a result, the AAIB recommended that the UK CAA “develop an increased awareness of the | medium | 2,755 |
Aviation, Technology, Hungary, United Kingdom, History.
aircraft design and manufacturing philosophies which have been, and are being used in the former Soviet Socialist Republics.” ◊◊◊ US Air Force C-145As at Eglin Air Force Base. (US Air Force) The story of the An-28 did eventually reach something like a happy ending. Starting in 1993, the PZL-Mielec | medium | 2,756 |
Aviation, Technology, Hungary, United Kingdom, History.
aircraft plant in Poland began producing license-built An-28s with updated avionics and Canadian-made Pratt & Whitney PT6A engines, intended to meet Western safety and performance standards. Redesignated as the PZL M28 Skytruck, the revamped model sold more examples than the original and was still | medium | 2,757 |
Aviation, Technology, Hungary, United Kingdom, History.
in production as recently as 2019. The Skytruck found plenty of users outside the traditional markets for Eastern Bloc aircraft, including, interestingly enough, in the US military. In 2012, the United States Air Force purchased around 10 M28 Skytrucks, which were given the military designation | medium | 2,758 |
Aviation, Technology, Hungary, United Kingdom, History.
“C-145A Combat Coyote.” A brief Air Force Times article on their introduction made no mention of the plane’s Soviet pedigree, but it did quote Colonel JD Clem of the Air Force Special Operations Command, who said, “The [Skytruck] is simply to haul people around. There is nothing really cosmic about | medium | 2,759 |
Aviation, Technology, Hungary, United Kingdom, History.
it at all.” The C-145A served in the US Air Force for 10 years, until the last example was retired in 2022. An article posted on the Air Force Reserve Personnel website at the time quoted Master Sgt Bobby Barton of the 919th Special Operations Group, which operated the type: “There weren’t many | medium | 2,760 |
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other aircraft in the Air Force like this one,” he said. “It really stood out from the crowd.” But this article didn’t acknowledge where the design came from either. In fact, I was not able to find any that did. One last photo of HA-LAJ in better times. (Unknown author) As for the crash of HA-LAJ, | medium | 2,761 |
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its significance was limited at the time and has only lessened since. It was, at the end of the day, a small crash involving a small plane in an out of the way location from which everyone walked away. I only found out about it because it was listed in the “recently published reports” section of a | medium | 2,762 |
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different AAIB accident report from around the same time. And yet the more I read, the more interesting the story became, from the background of the airplane to its head-scratching design flaws to the outlandish failure that caused it to crash. From the language in their report, it’s possible to | medium | 2,763 |
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surmise that the AAIB investigators had much the same reaction. How often did they get to investigate the crash of an Antonov on British soil? Certainly not every day! Often I end these stories with some kind of lesson, but this time I don’t think I will. “Don’t design a plane with a single point | medium | 2,764 |
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of failure that causes both engines to fail when you retract the flaps” is probably too obvious. And ultimately the reason I wrote this article is because I thought the story was worth sharing for its own sake. So I hope, having read all of this, that you agree. | medium | 2,765 |
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_______________________________________________________________ Don’t forget to listen to Controlled Pod Into Terrain, my podcast (with slides!), where I discuss aerospace disasters with my cohosts Ariadne and J! Check out our channel here, and listen to our latest episode, about an airline | medium | 2,766 |
Aviation, Technology, Hungary, United Kingdom, History.
_______________________________________________________________ Join the discussion of this article on Reddit Support me on Patreon (Note: I do not earn money from views on Medium!) Follow me on Twitter Visit r/admiralcloudberg to read and discuss over 260 similar articles (New feature!) | medium | 2,768 |
A Star Algorithm, Graph Algorithms, Graph, Data Structure Algorithm, Algorithms.
Data Structures and Algorithms: Weighted Graph Processing — Part 2: A* In continuation to my last blog, this time around we’re going to discuss the A* algorithm. Last time around we saw about Dijkstra’s algorithm and I mentioned that A* is similar to Dijkstra with only a slight but crucial twist to | medium | 2,770 |
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its approach. Note If you need a recap on Dijkstra’s or if you’re new to weighted-graph processing algorithms, check out my last post on Dijkstra’s algorithm: Data Structures and Algorithms: Weighted Graph Processing — Part 1: Dijkstra Last time around, we saw what is a weighted graph? How to build | medium | 2,771 |
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one from scratch? Where can it be used? In case…sethuram52001.medium.com So, if you’re wondering — What is the A* algorithm? Why is it preferred most of the time over Dijkstra’s algorithm? Let’s get started then! A* is a path-finding algorithm based on weighted graphs. A* is also known as the | medium | 2,772 |
A Star Algorithm, Graph Algorithms, Graph, Data Structure Algorithm, Algorithms.
best-first search algorithm or informed search algorithm. Given a starting node of a graph(usually a weighted-graph) it aims to find a path to the target node having the smallest cost ( the factors for the cost can vary from distance, time, or any sought of hindrances along the way and etc.,) Let’s | medium | 2,773 |
A Star Algorithm, Graph Algorithms, Graph, Data Structure Algorithm, Algorithms.
take a real-life example, you’re planning to move from place A to B. So, now you open a digital mapping service (like g-maps for example), you would have noticed that there are multiple paths from source to destination and the best path is pointed out in reference to the estimated time of travel. | medium | 2,774 |
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Although there may be some paths that are shorter in distance but due to other factors such as traffic and speed limit, you might have been recommended another path as the best option. So, now let’s connect this example with our base concept the road network is the graph, and the location such as a | medium | 2,775 |
A Star Algorithm, Graph Algorithms, Graph, Data Structure Algorithm, Algorithms.
landmark, are the nodes, the various roads which connect the locations are the edges in the graph, distance, speed limit, or any other factor which may hinder the travel is considered as the weight along the path. So, the digital mapping service uses a path-finding algorithm such as the A* | medium | 2,776 |
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algorithm will find the best possible path from the starting point to the destination. I hope we have some basic intuition on a path-finding algorithm so that now we can jump to the topic of the hour A* algorithm. Basic terminology Before looking into the algorithm, let’s first get familiar with | medium | 2,777 |
A Star Algorithm, Graph Algorithms, Graph, Data Structure Algorithm, Algorithms.
some basic terminologies related to the A* algorithm: Open list: It is a collection of all generated nodes, i.e., those are the nodes that were neighbors of expanded nodes. (The open list is often implemented as a priority queue so that algorithm can easily dequeue the next best node.) Closed list: | medium | 2,778 |
A Star Algorithm, Graph Algorithms, Graph, Data Structure Algorithm, Algorithms.
It is a collection of all expanded noes, i.e., those are the nodes that were already searched. This prevents the algorithm from revisiting the nodes. A* algorithm has 3 parameters: a) g: the cost of moving from the initial node to the current node. Basically, it is the same as all the nodes that | medium | 2,779 |
A Star Algorithm, Graph Algorithms, Graph, Data Structure Algorithm, Algorithms.
have been visited since leaving the first node. b) h: also known as the heuristic value, it the estimated cost of moving from the current node to the final node. The actual cost can’t be calculated until the final node is reached. Hence, h is the estimated cost. We must make sure that there is | medium | 2,780 |
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never an overestimation of the cost. c) f: It is the sum of g and h. So, f = g + h. Algorithm Define the open list and initialize it with the start node. Define the closed list. If the open list is empty, return failure and exit. Remove node n with the smallest value of f from open and move it to | medium | 2,781 |
A Star Algorithm, Graph Algorithms, Graph, Data Structure Algorithm, Algorithms.
the closed list, if the n is the target node, return success and exit. Expand node n. If any successor to n is the target node, return success and the shortest path by tracing the path from the target node to the start node. Else, for each successor node, a) Apply the evaluation function f to the | medium | 2,782 |
A Star Algorithm, Graph Algorithms, Graph, Data Structure Algorithm, Algorithms.
node b) If the node has not been in either list, add it to the open list. Note The code implementation that we’re going to discuss is going to be in java (as I’m more comfortable with java 😅), but don’t worry I have given a pseudo code for the same algorithm below, which you could refer to | medium | 2,783 |
A Star Algorithm, Graph Algorithms, Graph, Data Structure Algorithm, Algorithms.
implement the algorithm of the language of your choice. Pseudo Code Code We’re going to try to implement A* algorithm for the weighted graph, given below: We’re using an adjacency list to represent the graph, where each element in the list will have two values. One is the other node to which the | medium | 2,784 |
A Star Algorithm, Graph Algorithms, Graph, Data Structure Algorithm, Algorithms.
node is connected with and the other is the weight along with the edge passing between the two nodes. So, the output of the above program can be seen below which is 0->1->3->4 ->5 Applications A* is often used for the common pathfinding problem in applications such as video games but was originally | medium | 2,785 |
A Star Algorithm, Graph Algorithms, Graph, Data Structure Algorithm, Algorithms.
designed as a general graph traversal algorithm. It finds applications in diverse problems, including the problem of parsing using stochastic grammars in NLP. Other cases include an informational search with online learning. So, we have come to the end of this post, and thank you so much 😊 if you | medium | 2,786 |
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have made it this far into this post. I will see you in the next post! Always grateful, never complacent! References http://theory.stanford.edu/~amitp/GameProgramming/AStarComparison.html https://www.algorithms-and-technologies.com/a_star/java | medium | 2,787 |
A Star Algorithm, Graph Algorithms, Graph, Data Structure Algorithm, Algorithms.
https://github.com/TheAlgorithms/Java/blob/master/DataStructures/Graphs/A_Star.java https://www.educative.io/edpresso/what-is-the-a-star-algorithm https://en.wikipedia.org/wiki/A*_search_algorithm https://stackabuse.com/graphs-in-java-a-star-algorithm/ | medium | 2,788 |
A Star Algorithm, Graph Algorithms, Graph, Data Structure Algorithm, Algorithms.
https://stackoverflow.com/questions/45577114/a-star-algorithm-open-and-closed-lists/45577852 https://www.gatevidyalay.com/tag/a-algorithm-applications/ https://www.researchgate.net/figure/A-search-algorithm-Pseudocode-of-the-A-search-algorithm-operating-with-open-and-closed_fig8_232085273 My Github | medium | 2,789 |
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Consequences and causes of global warming Global warming, a phenomenon caused primarily by human activities, has serious consequences for the environment, society and economy. In this article, we will delve into the consequences and causes of global warming, explore together alternative solutions, | medium | 2,791 |
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plankton, disrupting marine ecosystems and fisheries. Biodiversity Loss: Global warming exacerbates habitat loss, fragmentation, and degradation, leading to species extinction and loss of biodiversity. This loss undermines ecosystem resilience and compromises essential ecosystem services. Causes of | medium | 2,797 |
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wind, hydroelectric, and geothermal power can reduce reliance on fossil fuels and mitigate GHG emissions. Energy Efficiency: Improving energy efficiency in buildings, industries, and transportation sectors can significantly reduce energy consumption and GHG emissions, contributing to climate change | medium | 2,802 |
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Developing resilience and adaptive capacity to cope with the impacts of global warming, such as extreme weather events, sea-level rise, and changes in agricultural productivity, through community-based adaptation measures and disaster preparedness. Impact on the World Economy Economic Costs: Global | medium | 2,807 |
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