Nowadays, commercial airplanes do not fly with metal wires moving the ailerons anymore. Now it is managed digitally, from the source (the sidestick or yoke movements) to the control surfaces movement. This system is called Fly-by-wire.

The fly-by-wire system consists of some computers (5 computers on board the Airbus’ planes, 3 primary and 2 secondary), that read the pilot movements, interpret them, and it sends a modified signal (from the original one) to the control surfaces. 

All these means that the airplane movements will not match proportionally what the pilot is doing actually. This philosophy shocked a lot of pilots, they couldn’t imagine flying something without a cable between the yoke and the surfaces. Finally, it was demonstrated that this system was much efficient, safer and much versatile.

Airbus was the first one using fully fly-by-wire (A320 were the first) and they create a set of laws that would govern this system. There are 4 laws: normal law, alternate law, direct law and mechanical back-up depending on the degradation of the airplane.

• Normal Law: It is on when normal operation is carried out. It controls the 3 axis (pitch, roll and yaw) balancing the aircraft and interpreting the sidestick movements. In addition, it offers some envelope  flight protections (on pitch attitude and roll attitude) and alleviate load factors, like the gravity when turning for a much better comfort.
• Alternate Law: If a minor failure exists (sensors disagreement, computer blackout, hydraulic system upset,etc) this law becomes the active one. Basically it provides the same control as the normal law, but without protections. Also, the roll control becomes “direct law-like” control.
• Direct Law: If a major failure exists (radio altimeter failure when approaching, 3 inertial references down, etc) this law become the active one. Then, the movements of the control surfaces are the same as the sidestick movements. There is no auto trim, and any protection system will be available (even alpha-floor for stall warning).

• Mechanical Back-up: This mechanical aid should be used when the electrical system is all down. Then, the airplane can only be controlled with the trim wheel for pitching, and rudder pedals for rolling.

Virgin America will release an in-flight wireless Internet on all his flights by the second quarter of 2009. In fact, they flew a test flight from San Francisco to test the whole system and it kinda works.

This gadget, called GoGo, will not forbid any special content, but there will be some constraints though ( no Skype, no IP voice systems,…). The company’s philosophy is not to edit the content that passengers want to watch, but to offer WiFi in order to let the people choose what to watch. This system will be available above 1000 feet and it works with 3G technology.

Thence, get connected in the airplane will be $10 on short flights, and $13 on longer legs. You just need a laptop to get access. Virgin says that later in 2009 they will include an integrated in-flight entertainment system, that will give connectivity to people who don’t have laptops or PDA’s.

Of course, nowadays, a lot of airlines are willing to incorporate this devices to their birds.

Source: Original Link

Each conventional aircraft, just because they have wings, they create wake turbulences at wing tips. Since we have high pressure underneath the wing and low pressure above it, this pressure difference converge at the wing tips. Air from high pressure goes up to low pressure zones, plus the forward movement of the airplane create an espiral-like movement of rough air behind the airplane. These wake turbulences are increased (abruptness and size) when dealing with heavy airplanes and low speeds, like the approach stage.

Wake turbulence created by the airplane (NASA)

This rough air does not concern this aircraft, but the aircraft behind it does. Actually, the aircraft behind might fly through this turbulence. As the air is in rotation, it does not keep sticked to the wing foil, so it may cause a lift loss. That’s why ICAO establishes a minimum separation between aircrafts, enroute as well as in approach, in order to avoid rough air. These turbulences drive away because of air viscosity and because of the wind. Even that, they could be 5 miles long and go down up to 900 ft.

In order to decrease these effects, there is a very used and useful tool called winglet, set up at the wing tip, and it slows down the air flow reducing then, the wake turbulence (and the fuel consumption).

Winglet                        Source: Air Guide Online

Every single day, hundreds of commercial airplanes cross the north atlantic, flying transcontinental routes linking North America and Europe basically, the NAT (North Atlantic Tracks). The performances of these flights are much different and complex due to its distant routes from any kind of airport.

The twin-engine aircrafts operating these flights (usually big ones) must have the ETOPS rating, explained in other post. That is because the nearest alternative airport when flying above the atlantic is 180 minutes far. If an engine failure happens (or any other system), this aircraft should divert to the closest airport immediately.

Another huge problem is the radar coverage. As a matter of fact, this radar coverage does not exist. Radars must be set up on ground or close (not floating over the sea). The main Air Traffic Control facilities (Shanwick Oceanic for European side and Gander Oceanic for US side) are equipped with air traffic management systems that by means of pilot manual position reports, they have some sort of “radar-like” screen with all the airplanes’ positions.

The third and big problem as well (but solved anyway) is about communications. The communicacions between pilots and controllers use VHF (Very High Frequency from 30 MHz to 300MHz) frequency range. VHF waves only reach “line-of-sight” spaces. So, in that case they must use HF (High Frequency from 3 MHz to 30MHz) that bounces off the ionosphere and give coverage to greater distances. Nevertheless, even this advantage, sound quality is much poor.

The NAT routes are designed and published daily. They are defined with an entry waypoint, an exit waypoint and between, waypoints are defined with coordinates (there are no navaids to define them). Early in the morning, westbound routes are published. Then late at night, eastbound routes are published. Europe incoming routes are usually defined at higher latitude, to take advantage of the Jet Stream (high speed wind, will post about this).
By the way, pilots flying these routes cannot eat the same meal.

Here we can appreciate North Atlantic Routes all the day long

The quick fuel draining system (called Fuel Jettison) is an onboard system in large aircrafts like B747, B767, B777 and some B757 and also A330 and A340.

When an emergency procedure around an airport is carried out, the airplane must be able to land with the Take Off Weight (sometimes Maximum Take Off Weight). Then, the low/mid range airplanes have no problems dealing with that, but long range airplanes does.  

Heavy airplanes usually carry a huge amount of fuel (because of long haul flights). Thence, according to JAR regulation JAR 25.1001 about Airworthiness, these heavy aircrafts must be equipped with a Fuel Jettison system. The regulation require to the system to empty the tanks in 15 minuts, and then leaving enough fuel to keep a 3.2% climb gradient in landing configuration at 1.15 stall speed. For example, a B727 releases 1060 kg (2330 lbs) of fuel per minute, with all tank pumps running. The fuel nozzle is set at the wing tip, in order not to make any damage at the airplane fuselage. 

    Source: Wikimedia

Even though this procedure seems pretty enviromentally harmful, it isn’t much critisized because its low frequency, low amount of sprayed fuel and the procedure conditions. If possible, fuel jettison procedure must be done over the sea.