Airplane debugging? It is very easy!
Some time ago I had to very closely participate in the acceptance tests of the aircraft. These tests were the main part of the process of transferring the freshly prepared, most (in my opinion) business-technology that is currently technically advanced to the customer. It would seem, and here testing, development, and in general the subject of Habr? Those who want to know this can turn the page and read quite a lot of text, and without any pictures at all.
Immediately I warn you - the introductory part will be long, but without this it is simply impossible to get to the heart of the matter.
For a variety of reasons, I will not give the names of specific manufacturers, model aircraft and other products mentioned in the article. If anyone can identify by himself - please, but I have nothing to do with it.
This article does not set out to give the reader a full course of all aviation sciences. I will explain only the most necessary, and most often in a simplified form (omitting details that are not essential for understanding the article).
')
So, it was necessary to make sure that the transmitted aircraft complies with its specification in all respects - starting with the appearance, and ending with the functioning of all nodes in all modes. In addition, during the tests, pilots are commissioned, who will later fly on this plane (before that, they were trained for this type using a simulator, but it was not yet on this particular aircraft).
An aircraft of this class is an extremely complex device. So complex that most people don’t even closely represent everything that is heaped up inside a relatively small enclosure. This complexity, together with the rather stringent certification requirements for everything and everyone - from the wings to the coffee maker, also determines the corresponding cost of the device - in this case it is not one ten million dollars.
The complexity of the product brings with it a rather unexpected feature for non-aviation people - almost always something is faulty in any more or less large aircraft. This should not (usually) frighten - malfunction means almost everything, beginning, figuratively speaking, from the lack of water in the same coffee machine.
To understand whether it is possible to operate an aircraft with one or another malfunction, there is a so-called Minimum Equipment List (MEL) - a document describing the criticality of the detected malfunctions to the possibility of performing various types of flight operation of the aircraft. If any particular malfunction does not completely prohibit flight operations, then the corresponding MEL item describes exactly what restrictions are imposed on the operation of the aircraft, and what additional measures need to be taken to perform the flight (in the case of a coffee maker - hang up a sign on the prohibition of activation).
The question arises - why are virtually faulty airplanes generally allowed to fly, because it is dangerous ?! The problem is that if absolutely 100% serviceability was required, the overwhelming majority of the aircraft would simply never take off at all. And, again, in the overwhelming majority of cases, MEL just provides the necessary level of security even in the presence of some malfunctions due to the narrowing of the allowable operating ranges of the equipment.
The aircraft under consideration has just begun to be produced, and a particular instance has a serial number in the top ten. This means a lot - for example, the fact that there is practically no operating experience, no maintenance experience, and even infant diseases will manifest themselves in all their glory.
In its filling is perhaps the most computerized type in its class. There are no direct analog connections between the components of the aircraft (sensors, actuators, controls, etc.). Even digital communications are not direct, but via a central computer. For example, if it is necessary to release flaps, transferring the corresponding lever to the desired position only sends a request to the central computer for this action. Next, the computer analyzes a whole bunch of parameters for the possibility of performing an action, and decides whether to satisfy the request, or whether the pilot is confused first. In the classic plane, this lever was connected to the actuator almost directly. All sensors work similarly - they tell their state to the central computer, and he already distributes this information on request. Compare - in the "normal" plane from each sensor wires to all nodes diverge, which may need to know the status of this sensor. For example, a dozen or two systems are interested in the sensor for compressing the wheel racks (to understand whether there is an aircraft on the ground or not).
Moreover, this is the only aircraft known to me (I’ll tell you right now that I’m not familiar with the details of the latest Boeing and Airbus devices), where you can realize the plot of the idiotic super-burglar action movie that took control of the aircraft remotely. Purely theoretically (well, very theoretically, but still with some degree of probability), it is possible to connect to onboard WiFi (not the one for passengers, but intended for some service functions) and load your program into control units. Then everyone can dream at their own discretion ...
Such a construction of the aircraft as it gives a whole bunch of advantages (which we will not discuss here), and creates an incredible amount of problems in operation. The manufacturer, in joy, realized such a cunning interaction of the systems with each other that it became incredibly difficult to identify the problem. If earlier, in the event of a malfunction of a node, the troubleshooting was limited to fairly clear boundaries, now the cause of the inoperative landing light may well be related to a poorly closed tap of warm water in the toilet. In addition, the plane uses fairly large blocks, produced by third-party companies, and which are for the aircraft manufacturer to be a black box with not quite understood processes inside. In general, this topic can be talked about a lot and interestingly, but let's proceed, nevertheless, to flights.
So, after a couple of days of studying the aircraft on the ground, we had some kind of picture. In principle, you can fly. Yes, a number of problems have been found, some of which will be corrected in the next few days, some are known to the manufacturer and are in operation, some things seem to require serious decisions by the manufacturer and a complete rework of the relevant nodes in the future. After preparing the aircraft for flight and starting the engines, 5 informational messages are lit on the screen about various inconsistencies with what the aircraft thinks should be. In fact, the crew cabin is designed on the principle of “dark cockpit” - i.e. during normal operation of all nodes, there should be no messages at all, but ok, at this stage, this is normal.
To top it all, a file with a FAQ was attached to the aircraft, explaining why the incorrect operation of one system or another is still completely normal, and what to do in some cases when reading the flight operation manual (RLE) does not answer the question. To be honest, we were all embarrassed by more than a hundred positions in this FAQ, but there was nothing to be done.
We decide to make the first flight right at the airfield where the manufacturer's plant is located. We take off, remove the chassis and then for 10 minutes we carry out the dispatcher's commands before he sends us to land. After the first landing, we decide that in order to save time, we will leave for the next airfield, where traffic is more free. We fly there and begin the process of mastering the aircraft. After all the pilots have tried basic maneuvers under the direction of the test pilot of the manufacturer, the process of “winding up circles” begins - takeoff, short flight in a circle, landing and then taking off again. Thus, each pilot must make ten takeoffs. Usually, such things are not practiced on airplanes of this class - it is believed that the simulator is quite enough to obtain the necessary skills, and the flight time of such a board is very expensive (if interested, the cost is about 5 thousand dollars per hour). Fortunately, the owner understands that this approach is fundamentally wrong, and decides to give pilots the opportunity to experience the real aircraft.
So, the first fast flight in a circle. Normal take-off, climb, and suddenly in the office a beep sounds and a warning message lights up (as opposed to an informational one, such messages warn of more or less serious things). The message states that there was a failure of reverse thrust on the right engine.
And again, a learning retreat. On airplanes with turbojet engines, thrust reversal is performed by releasing special flaps on the engine that deflect some of the outgoing gases forward. As a result, these gases create backward thrust and help slow the aircraft. Reverse thrust is an auxiliary system, even the calculation of the length of the required band during landing is done without taking into account the work of the reverse. So his refusal in itself does not cause any particular problems, but a very serious question arises - what exactly happened?
We decide to return to the departure aerodrome so that in the factory conditions the staff of the manufacturer can deal with the problem. There is no particular concern - in theory, the task should not be difficult.
After taxiing we describe the situation and go to the hotel. The next morning, we receive a report from the mechanic responsible for our aircraft. Unfortunately, the report does not personally please me - I clearly understand that there is no clear understanding of what exactly happened. It seems that something was touched, something was adjusted, an error was dropped, checked on the ground - everything is in order. Well, maybe an accident ... Although I have a clear belief that it was not an accident.
We make the first flight again at the manufacturer’s aerodrome, everything goes fine. Like yesterday, we will fly to the airdrome more freely and continue the planned program. The first flight in a circle again gives us yesterday's problem. The mood drops sharply, we return back to the factory. I gently explain to the representative of the manufacturer that we have our own plans, which do not include a long stay in a pretty nondescript hotel at this airport. The representative apologizes and introduces us to the program manager for this type of aircraft, who came here specifically to deal with our problem. After several hours of very active work, the specialists are completely at a loss - everything seems to be in order, no signs of malfunction.
Here it is worth understanding that the plane is so new for everyone, including the manufacturer’s employees, that they still have no real experience with such systems. Potentially universal computerization allows you to get a huge amount of information about all stages of flight, but nobody has learned how to use it all.
I understand that the process comes to a standstill. The thought of having to stay longer in a hotel upsets me (and it’s just lazy to move to another), and I begin to strain my brains, although I understand all the ridiculousness of my attempts compared to people who have worked in the aviation industry all my life. However, an idea suddenly comes to me. I ask to prepare the plane for departure and I promise to demonstrate the first flight in a circle without an error, and the second - with an error. What is the point, while I am not telling anyone, but at the same time I am a little nervous - what if my guess is wrong and I will look like an idiot?
Take-off, cleaning the chassis, climb, go to horizontal flight - everything is fine. Representatives of the manufacturer begin to look at me with interest and suspicion. Well, if only the second part also went as planned! So, again takeoff, climb and painfully familiar beep. Everything, half the battle is done - at least, it is clear how to reproduce the problem.
The attentive reader has probably already noticed the difference in these two flights - namely, that the landing gear was not removed during the second flight. That was what occurred to me when I scrolled past flights in my mind and tried to understand what was special about those flights during which we received reports of a problem. I will explain a little - usually such airplanes fly far and long, and the first action immediately after separation from the runway during take-off is landing gear cleaning. In our cases, we were going to do very short flights in a circle, and in order not to wear out the landing gear once again, we decided to fly with the wheels released. This is a completely normal procedure, which is quite often used in such situations and does not contradict any regulatory documents. Another thing is that, as I have already said, such planes practically do not fly in a circle, so there is no particular need to fly with the landing gear.
Having on hand already quite a strong reference point, the staff of the manufacturer with a tripled enthusiasm began to search for faults. During the process, which I will not describe in detail, the first significant detail appeared. It turns out that the reverse thrust system (TR) did not break itself, but was forcibly disconnected on command from FADEC.
Here it is worthwhile to dwell on FADEC in more detail - this already directly corresponds to the subject of the site. Full Authority Digital Engine Control is a specialized computer that controls the aircraft engine. For me, one of the most impressive parameters of this box the size of a brick floor is the price. To say that a device is worth its weight in gold is to say nothing. In my opinion, FADEC costs 100 times more than it should, even if we take into account all the requirements for reliable operation. Moreover, there are two such boxes on each engine, they work one by one, and they even follow each other in the process of work so that in a difficult moment (if one of the boxes suddenly becomes ill) to put a shoulder to a friend. In fact, the aircraft asks FADEC to perform certain actions (start / stop the engine, set a certain power, etc.), and FADEC completely (and rather independently of the aircraft) controls the necessary systems (starter, fuel controller, etc.) to fulfill the request if it deems it possible.
So, for some reason, which is still incomprehensible to us, the reasons for FADEC forced TR into a state of failure under certain conditions, and we knew these conditions in the most general form (take-off without subsequent landing gear removal), but somehow link them between themselves could not. To understand the problem in more detail, I had to contact the engine manufacturer. Log files with FADEC were sent to the factory that produced the engines, and quite quickly (although by this time we had already moved to another hotel) the answer was received. It turns out that one of the branches of the FADEC logic provides for testing the operation of the brakes. If during the check FADEC decides that the brakes on some side of the aircraft do not work well, then the reverse on the opposite side will be disabled. And even more than that, they explained to us that, according to FADEC, the wheels of the aircraft after takeoff slow down their rotation at different speeds, which caused the corresponding FADEC reaction. If the chassis is removed immediately after takeoff, the wheels automatically brake quite energetically, and FADEC does not detect any problems in this place.
To test this theory, we made another flight, during which the chassis was not removed, but immediately after take-off, the wheels were manually braked. In principle, the flight confirmed the theory put forward - with forced deceleration, everything was normal, without it - the failure of the reverse appeared consistently.
It seemed that the problem area had finally narrowed down, and a ray of hope dawned ahead of us for a speedy departure from the already painful airfield. However, a complete rearrangement in places (from left to right and from right to left) of all the systems and units that had to do with the chassis and brakes did not solve the problem, and did not change places (what we really hoped for).
At this point, a representative of the engine manufacturer appeared at the airport, whom I decided to try to find out exactly how FADEC decides that something is wrong with the brakes. After lengthy consultations with the office, obtaining permits for disclosing confidential information and simply attempting to otmazatsya without any ideas, he finally provided me with the required information.
It turns out that FADEC tracks the speed of the wheels as a sliding time window with a duration of several seconds. Probably easier to explain with an example. Suppose this time window is 4 seconds. Let on the 10th second flight speed of one wheel was 20 revolutions per second. In this case, if starting from the 8th to the 12th second of the flight, the second wheel rotated at a speed of 20 revolutions per second at any moment, then everything is fine. If separately taken wheel speeds for a period of 4 seconds did not coincide even once, FADEC concludes that the brake system is out of order.
( , , . ), – ? , , . , -, ( , - ..), , .
, , - ( ). , . , (2-5 ), . , FADEC. , , , iPhone . , iPhone , , .
, 6 , iPad, Excel. , , – . , , , .
, . «» , , .
, , , , , , (, , – FADEC) — habrahabr.ru/post/144686
, , , , - FADEC, , .
– , , FADEC , , . , ( FADEC , ) - , .
, , . , …
PS , , ? – FAQ , , TR – , .
PPS , , , , – , ( ).
Immediately I warn you - the introductory part will be long, but without this it is simply impossible to get to the heart of the matter.
For a variety of reasons, I will not give the names of specific manufacturers, model aircraft and other products mentioned in the article. If anyone can identify by himself - please, but I have nothing to do with it.
This article does not set out to give the reader a full course of all aviation sciences. I will explain only the most necessary, and most often in a simplified form (omitting details that are not essential for understanding the article).
')
So, it was necessary to make sure that the transmitted aircraft complies with its specification in all respects - starting with the appearance, and ending with the functioning of all nodes in all modes. In addition, during the tests, pilots are commissioned, who will later fly on this plane (before that, they were trained for this type using a simulator, but it was not yet on this particular aircraft).
An aircraft of this class is an extremely complex device. So complex that most people don’t even closely represent everything that is heaped up inside a relatively small enclosure. This complexity, together with the rather stringent certification requirements for everything and everyone - from the wings to the coffee maker, also determines the corresponding cost of the device - in this case it is not one ten million dollars.
The complexity of the product brings with it a rather unexpected feature for non-aviation people - almost always something is faulty in any more or less large aircraft. This should not (usually) frighten - malfunction means almost everything, beginning, figuratively speaking, from the lack of water in the same coffee machine.
To understand whether it is possible to operate an aircraft with one or another malfunction, there is a so-called Minimum Equipment List (MEL) - a document describing the criticality of the detected malfunctions to the possibility of performing various types of flight operation of the aircraft. If any particular malfunction does not completely prohibit flight operations, then the corresponding MEL item describes exactly what restrictions are imposed on the operation of the aircraft, and what additional measures need to be taken to perform the flight (in the case of a coffee maker - hang up a sign on the prohibition of activation).
The question arises - why are virtually faulty airplanes generally allowed to fly, because it is dangerous ?! The problem is that if absolutely 100% serviceability was required, the overwhelming majority of the aircraft would simply never take off at all. And, again, in the overwhelming majority of cases, MEL just provides the necessary level of security even in the presence of some malfunctions due to the narrowing of the allowable operating ranges of the equipment.
The aircraft under consideration has just begun to be produced, and a particular instance has a serial number in the top ten. This means a lot - for example, the fact that there is practically no operating experience, no maintenance experience, and even infant diseases will manifest themselves in all their glory.
In its filling is perhaps the most computerized type in its class. There are no direct analog connections between the components of the aircraft (sensors, actuators, controls, etc.). Even digital communications are not direct, but via a central computer. For example, if it is necessary to release flaps, transferring the corresponding lever to the desired position only sends a request to the central computer for this action. Next, the computer analyzes a whole bunch of parameters for the possibility of performing an action, and decides whether to satisfy the request, or whether the pilot is confused first. In the classic plane, this lever was connected to the actuator almost directly. All sensors work similarly - they tell their state to the central computer, and he already distributes this information on request. Compare - in the "normal" plane from each sensor wires to all nodes diverge, which may need to know the status of this sensor. For example, a dozen or two systems are interested in the sensor for compressing the wheel racks (to understand whether there is an aircraft on the ground or not).
Moreover, this is the only aircraft known to me (I’ll tell you right now that I’m not familiar with the details of the latest Boeing and Airbus devices), where you can realize the plot of the idiotic super-burglar action movie that took control of the aircraft remotely. Purely theoretically (well, very theoretically, but still with some degree of probability), it is possible to connect to onboard WiFi (not the one for passengers, but intended for some service functions) and load your program into control units. Then everyone can dream at their own discretion ...
Such a construction of the aircraft as it gives a whole bunch of advantages (which we will not discuss here), and creates an incredible amount of problems in operation. The manufacturer, in joy, realized such a cunning interaction of the systems with each other that it became incredibly difficult to identify the problem. If earlier, in the event of a malfunction of a node, the troubleshooting was limited to fairly clear boundaries, now the cause of the inoperative landing light may well be related to a poorly closed tap of warm water in the toilet. In addition, the plane uses fairly large blocks, produced by third-party companies, and which are for the aircraft manufacturer to be a black box with not quite understood processes inside. In general, this topic can be talked about a lot and interestingly, but let's proceed, nevertheless, to flights.
So, after a couple of days of studying the aircraft on the ground, we had some kind of picture. In principle, you can fly. Yes, a number of problems have been found, some of which will be corrected in the next few days, some are known to the manufacturer and are in operation, some things seem to require serious decisions by the manufacturer and a complete rework of the relevant nodes in the future. After preparing the aircraft for flight and starting the engines, 5 informational messages are lit on the screen about various inconsistencies with what the aircraft thinks should be. In fact, the crew cabin is designed on the principle of “dark cockpit” - i.e. during normal operation of all nodes, there should be no messages at all, but ok, at this stage, this is normal.
To top it all, a file with a FAQ was attached to the aircraft, explaining why the incorrect operation of one system or another is still completely normal, and what to do in some cases when reading the flight operation manual (RLE) does not answer the question. To be honest, we were all embarrassed by more than a hundred positions in this FAQ, but there was nothing to be done.
We decide to make the first flight right at the airfield where the manufacturer's plant is located. We take off, remove the chassis and then for 10 minutes we carry out the dispatcher's commands before he sends us to land. After the first landing, we decide that in order to save time, we will leave for the next airfield, where traffic is more free. We fly there and begin the process of mastering the aircraft. After all the pilots have tried basic maneuvers under the direction of the test pilot of the manufacturer, the process of “winding up circles” begins - takeoff, short flight in a circle, landing and then taking off again. Thus, each pilot must make ten takeoffs. Usually, such things are not practiced on airplanes of this class - it is believed that the simulator is quite enough to obtain the necessary skills, and the flight time of such a board is very expensive (if interested, the cost is about 5 thousand dollars per hour). Fortunately, the owner understands that this approach is fundamentally wrong, and decides to give pilots the opportunity to experience the real aircraft.
So, the first fast flight in a circle. Normal take-off, climb, and suddenly in the office a beep sounds and a warning message lights up (as opposed to an informational one, such messages warn of more or less serious things). The message states that there was a failure of reverse thrust on the right engine.
And again, a learning retreat. On airplanes with turbojet engines, thrust reversal is performed by releasing special flaps on the engine that deflect some of the outgoing gases forward. As a result, these gases create backward thrust and help slow the aircraft. Reverse thrust is an auxiliary system, even the calculation of the length of the required band during landing is done without taking into account the work of the reverse. So his refusal in itself does not cause any particular problems, but a very serious question arises - what exactly happened?
We decide to return to the departure aerodrome so that in the factory conditions the staff of the manufacturer can deal with the problem. There is no particular concern - in theory, the task should not be difficult.
After taxiing we describe the situation and go to the hotel. The next morning, we receive a report from the mechanic responsible for our aircraft. Unfortunately, the report does not personally please me - I clearly understand that there is no clear understanding of what exactly happened. It seems that something was touched, something was adjusted, an error was dropped, checked on the ground - everything is in order. Well, maybe an accident ... Although I have a clear belief that it was not an accident.
We make the first flight again at the manufacturer’s aerodrome, everything goes fine. Like yesterday, we will fly to the airdrome more freely and continue the planned program. The first flight in a circle again gives us yesterday's problem. The mood drops sharply, we return back to the factory. I gently explain to the representative of the manufacturer that we have our own plans, which do not include a long stay in a pretty nondescript hotel at this airport. The representative apologizes and introduces us to the program manager for this type of aircraft, who came here specifically to deal with our problem. After several hours of very active work, the specialists are completely at a loss - everything seems to be in order, no signs of malfunction.
Here it is worth understanding that the plane is so new for everyone, including the manufacturer’s employees, that they still have no real experience with such systems. Potentially universal computerization allows you to get a huge amount of information about all stages of flight, but nobody has learned how to use it all.
I understand that the process comes to a standstill. The thought of having to stay longer in a hotel upsets me (and it’s just lazy to move to another), and I begin to strain my brains, although I understand all the ridiculousness of my attempts compared to people who have worked in the aviation industry all my life. However, an idea suddenly comes to me. I ask to prepare the plane for departure and I promise to demonstrate the first flight in a circle without an error, and the second - with an error. What is the point, while I am not telling anyone, but at the same time I am a little nervous - what if my guess is wrong and I will look like an idiot?
Take-off, cleaning the chassis, climb, go to horizontal flight - everything is fine. Representatives of the manufacturer begin to look at me with interest and suspicion. Well, if only the second part also went as planned! So, again takeoff, climb and painfully familiar beep. Everything, half the battle is done - at least, it is clear how to reproduce the problem.
The attentive reader has probably already noticed the difference in these two flights - namely, that the landing gear was not removed during the second flight. That was what occurred to me when I scrolled past flights in my mind and tried to understand what was special about those flights during which we received reports of a problem. I will explain a little - usually such airplanes fly far and long, and the first action immediately after separation from the runway during take-off is landing gear cleaning. In our cases, we were going to do very short flights in a circle, and in order not to wear out the landing gear once again, we decided to fly with the wheels released. This is a completely normal procedure, which is quite often used in such situations and does not contradict any regulatory documents. Another thing is that, as I have already said, such planes practically do not fly in a circle, so there is no particular need to fly with the landing gear.
Having on hand already quite a strong reference point, the staff of the manufacturer with a tripled enthusiasm began to search for faults. During the process, which I will not describe in detail, the first significant detail appeared. It turns out that the reverse thrust system (TR) did not break itself, but was forcibly disconnected on command from FADEC.
Here it is worthwhile to dwell on FADEC in more detail - this already directly corresponds to the subject of the site. Full Authority Digital Engine Control is a specialized computer that controls the aircraft engine. For me, one of the most impressive parameters of this box the size of a brick floor is the price. To say that a device is worth its weight in gold is to say nothing. In my opinion, FADEC costs 100 times more than it should, even if we take into account all the requirements for reliable operation. Moreover, there are two such boxes on each engine, they work one by one, and they even follow each other in the process of work so that in a difficult moment (if one of the boxes suddenly becomes ill) to put a shoulder to a friend. In fact, the aircraft asks FADEC to perform certain actions (start / stop the engine, set a certain power, etc.), and FADEC completely (and rather independently of the aircraft) controls the necessary systems (starter, fuel controller, etc.) to fulfill the request if it deems it possible.
So, for some reason, which is still incomprehensible to us, the reasons for FADEC forced TR into a state of failure under certain conditions, and we knew these conditions in the most general form (take-off without subsequent landing gear removal), but somehow link them between themselves could not. To understand the problem in more detail, I had to contact the engine manufacturer. Log files with FADEC were sent to the factory that produced the engines, and quite quickly (although by this time we had already moved to another hotel) the answer was received. It turns out that one of the branches of the FADEC logic provides for testing the operation of the brakes. If during the check FADEC decides that the brakes on some side of the aircraft do not work well, then the reverse on the opposite side will be disabled. And even more than that, they explained to us that, according to FADEC, the wheels of the aircraft after takeoff slow down their rotation at different speeds, which caused the corresponding FADEC reaction. If the chassis is removed immediately after takeoff, the wheels automatically brake quite energetically, and FADEC does not detect any problems in this place.
To test this theory, we made another flight, during which the chassis was not removed, but immediately after take-off, the wheels were manually braked. In principle, the flight confirmed the theory put forward - with forced deceleration, everything was normal, without it - the failure of the reverse appeared consistently.
It seemed that the problem area had finally narrowed down, and a ray of hope dawned ahead of us for a speedy departure from the already painful airfield. However, a complete rearrangement in places (from left to right and from right to left) of all the systems and units that had to do with the chassis and brakes did not solve the problem, and did not change places (what we really hoped for).
At this point, a representative of the engine manufacturer appeared at the airport, whom I decided to try to find out exactly how FADEC decides that something is wrong with the brakes. After lengthy consultations with the office, obtaining permits for disclosing confidential information and simply attempting to otmazatsya without any ideas, he finally provided me with the required information.
It turns out that FADEC tracks the speed of the wheels as a sliding time window with a duration of several seconds. Probably easier to explain with an example. Suppose this time window is 4 seconds. Let on the 10th second flight speed of one wheel was 20 revolutions per second. In this case, if starting from the 8th to the 12th second of the flight, the second wheel rotated at a speed of 20 revolutions per second at any moment, then everything is fine. If separately taken wheel speeds for a period of 4 seconds did not coincide even once, FADEC concludes that the brake system is out of order.
( , , . ), – ? , , . , -, ( , - ..), , .
, , - ( ). , . , (2-5 ), . , FADEC. , , , iPhone . , iPhone , , .
, 6 , iPad, Excel. , , – . , , , .
, . «» , , .
, , , , , , (, , – FADEC) — habrahabr.ru/post/144686
, , , , - FADEC, , .
– , , FADEC , , . , ( FADEC , ) - , .
, , . , …
PS , , ? – FAQ , , TR – , .
PPS , , , , – , ( ).
Source: https://habr.com/ru/post/202184/
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