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51

Generally speaking, pilots don't like it when a computer interprets or limits their actions. They want final control. They don't always get their way on this but that's their preference. If I recall correctly, Boeing tends to stick with the philosophy that "the pilot is the final arbiter." Airbus is more likely to preempt pilot inputs and modify them. ...


41

In flight mode the stick commands a load-factor. Which means it will be impossible to flare the aircraft, because as you pull on the stick, you'll be commanding a positive g-load. Because of this the Airbus has a flare mode which activates at 50' RA. At 50' the pitch angle is stored (memorized). At 30' the aircraft commands a 2° nose down (it takes 8 ...


38

Disabling the protections can technically be achieved. I say technically because there is not one scenario that Airbus has envisioned that would require the pilots to deliberately go into direct-law. The imposed limit in the question is something called alpha-protection -- a protection against pulling back too much that the plane stalls. Stalling is bad. ...


34

The fly-by-wire is absolutely vital for control of the aircraft, and the three dominating factors here are safety, safety and safety. Weight is not one of them. The fly-by-wire system is triple or quad redundant: instead of removing a set of cables, the manufacturers are installing 3 more cable looms, just to make sure that the system always works. Wires ...


33

Helicopter manufacturers seem to have been slow to adopt fly-by-wire systems. I used to work in the General Dynamics group which designed the fly-by-wire system for the F-16. That was the first production aircraft which had full-authority fly-by-wire (without mechanical backup systems). By the time I started working there, they were in process of updating ...


31

As far as I read in various documents about A320 and remember them correctly: There are three systems handling different parts of the primary flight control: ELAC (elevator & aileron computer) controls pitch with elevators+trim and roll with ailerons. SEC (spoiler & elevator computer) controls roll with spoilers and if ELACs fail, pitch with ...


25

Yes there will be a delay, but the delay caused by the control loop is really tiny. I've seen position control loops run successfully and stable at a couple of hundred Hz for simulator motion systems, and the time delay is just one iteration frame = less than 10 msec. And as @ymb1 correctly points out, if we deflect any control surface the end position is ...


24

I found this 16-year old thread on airliners.net. The Boeing 777 has the same system, and at the time it was unique in that. (You can watch it here.) When takeoff power is applied, hydraulic power is removed from the flaperons, as not to stress the actuators for an extended duration, which causes them to drop due to gravity. They are then slowly lifted by ...


21

The philosophy is that the pilot knows best. If they need to make a maneuver, they should be trusted to do so. Although there are absolute limits such as structure, other limits are less exact and depend on conditions (and even structure is built to withstand additional margins, failure, and damage). Something that qualifies as an "upset" is certainly not ...


18

Let's just focus on roll. The same command that can be used to roll the aircraft form 0° roll angle to 30° can be used to roll it from 30° to 60°. Who is to decide at what roll angle the airplane is and that from now on no further roll commands are acceptable? A computer-controlled FCS, obviously, if we decide the pilots cannot be trusted. But can we trust ...


18

Excessive phase lag is a direct contributor to Type I Pilot-Induced Oscillation (PIO). Phase lag comes from: Rigid body dynamics of the aircraft (e.g. delay between elevator surface and pitch rate response) Actuators (finite acceleration time between input and desired surface angle) Structural compliance (e.g. cable friction) Transport delay in signals ...


16

Computer limits can be overridden on an Airbus as a ‘last resort’, though I have serious doubts that would have helped with the landing on the Hudson incident. Granted, getting out of Normal Law is not SOP, or a normal procedure..but then again, why would it be? People complaining about the computer limits on flight controls, are similar to people ...


15

Most new designs do not accept such inputs. That includes: Airbus models from A320 onwards (includes A318 and A319 that are variants of A320). Boeing models B777 and B787. Sukhoi SuperJet Su100. Airbus has roll limit 65°, not 45°, but it automatically returns to at most 33° without constant pressure on the stick. I can't find explicit pitch limit, but it ...


15

For the complete electrical failure in the aircraft, the following systems have to fail: The onboard power generation system, usually a synchronous generator has to fail in all the engines. The APU (Auxiliary Power Unit) has to fail. The RAT (Ram Air Turbine) should fail to deploy. The batteries and static inverters should fail (this won't help in ...


14

Most decidedly not, at least not for the first fly-by-wire fighter in the NATO arsenal, the F-16. Its stick, in initial block versions, did not move at all, instead using piezoelectric load cells to detect stick pressure. This caused some issues with novice Viper drivers overreacting to the stiffness of the controls compared to anything they had flown and ...


13

That will be very unlikely simply because wireless is much less reliable by several order of magnitude. considering the current day an age of terror threats if the encryption (and you will need encryption) is ever compromised this would allow a passenger to hack into the datastream and Man in the Middle the controls for a hijack without ever entering the ...


13

I don't have an answer for the timings (I personally don't think that's publicly available information), but I can answer this is the delay noticeable by pilots? as I have some direct experience, and I can affirm that no, the pilot does not perceive a delay between a stick deflection and the aircraft reaction.


12

Valse Des Ailerons (Waltz of Ailerons) or VDA is a nickname for the Load Alleviation Function (LAF) which is part of the flight control system. LAF uses all ailerons and spoiler 6 to 8 to alleviate the fatigue and static loads on the wings by reducing the wing bending moment. It consist of various sub functions dealing with passive load alleviation (based ...


12

There are multiple factors here: The first and main one is of course weight. Fly-By-Wire requires computers and hydraulics to actuate the surfaces in a small plane weight is critical and a FBW system may be the difference between 3 and 4 passengers in total capacity. The next that comes to mind is certification, I'm not sure exactly how this works but I ...


12

No. Modern FBW airliners use less static stability than what the early jets were used to, but stability is still positive. The negative camber at the root airfoil of sweptback horizontal tails might indicate predominantly negative tail loads, but is also used to keep the isobars on the swept surface parallel. Also, the bent-up leading edge delays separation ...


11

It appears in both situations that the PF had trouble stabilizing the aircraft roll attitude. Note that roll control is secondary when recovering from a stall. Restoring normal pitch and roll, he stresses, are "of secondary importance" The situation required that the pilots heed the stall warnings, be aware of the stall and put the nose down to trade ...


11

Note: I focused more on changes in aviation hardware and software than what's currently used since the question linked about programming languages is still current for "new" aircraft. I do not wish to duplicate that question or its answers. In my opinion C++, C#, and Ada will probably be the dominant programming languages for avionics for the next decade ...


11

A simple answer is that the aircraft control system has ultimate responsibility for survival of the aircraft. If it completely fails, you are as good as dead in most cases. Short of in-flight destruction, hardly anything can be worse. Thus, full-authority (i.e. without mechanical backup) FBW gained acceptance only when the confidence in its overall ...


11

From the FCOM v2 (9.20.1): The primary flight control system uses conventional control wheel, column, and pedal inputs from the pilot to electronically command the flight control surfaces. The system provides conventional control feel and pitch responses to speed and trim changes. The system electronic components provide enhanced handling ...


11

The Space Shuttle's manual stick mode is called Control Stick Steering (CSS). It commands load factor in pitch (yaw is similar). In pitch it of course accounts for the existing load from vertical deceleration. And rate in roll. When released it holds the attitude. A second submode is indicated airspeed hold (the stick controls speed via the speed brakes), ...


10

Probably not. One manufacturer of "Active Control" joysticks, as used in F-35 training simulators says Because the active control stick is controlled by a computer almost any characteristic can be programmed. Typical and useful characteristics include: Multi modal feel characteristics - the ability to completely change the stick feel when moving ...


10

On Airbus aircraft, the guidance law provides attitude protection on take-off which should prevent a tail strike. However, this is not fool-proof and it remains up to the PF to maintain the correct nose-up angle.


10

In fact, ARINC 429 is used in the "federated" avionics, this is the "old" system used in many aircraft like A320, B737, ... Federated avionics require a lot of wires which generates a lot of weight. In ARINC we have approximately one wire per device, so the speed (100Kbps or 12,5Kbps depending on the selected mode) is sufficient. ARINC 429 Architecture : ...


10

For commercial airliners: the computing power is set during development and certification of the type. The A320 was developed in the 1980s and still uses Intel 80186 and Motorola 68020 processors. Your i7 CPU would be able to run rings around anything on board of the average airliner. But processing capacity is of secondary importance to airliners, safety ...


9

There are two extremes: No augmented controls, i.e. most normal aircraft. Pilot controls control surfaces and engines directly. Heavily augmented controls (left, right, up down shifts exactly like that), like quadcopters. Pilot gives command how the aircraft should move that is translated by algorithm into control surface and engine inputs. At either of ...


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