Aviation Explained

Answers to some of the things that you thought about but maybe didn't know who to ask...

On a long haul flight does the crew get some sleep?

They certainly do! The crew (both pilots and cabin crew) on your long haul flight are only human too so need to have a sleep during a long flight. During the flight the crew will take turns to sleep in the crew bunks which are either under the cabin floor or in the space above the luggage racks.

Who is flying the airplane when the pilots are having a sleep on a long haul flight?

On short flights there are usually two pilots in the flight deck operating the aircraft. On a long flight there will be a 'relief crew' who have the task of flying the aircraft whilst the 'operating crew' have their sleep.

Do you need a key to start the engine on an airplane?

Starting a plane is not the same as starting a car. There is no key but on modern jets it is a simple process: There are two switches - one on an overhead panel called the 'Auto Start Switch' and the other one is behind the thrust levers on the central control panel called the ‘Fuel Control Switch’. A pilot flicks the first to 'Start' and the second to ‘Run’, then the FADEC (the Full Authority Digital Engine Control - a computer program) does the rest by starting the engine rotating, opening the fuel valve and, at the right time, starting the igniters. It's pretty much what happens in your central heating system every time you, or your thermostat turns it on.

What speed does a plane get up to on a runway?

The runway speed depends on the type of plane. A Boeing 777 reaches 180 Knots - just over 200 miles an hour - before lift overtakes gravity and it takes off. When the plane hits this speed on the runway a co-pilot will call 'V1'. At this call, the plane has to take off, there's not enough runway left for it to slow down, nowhere to go but up, up and away!

How does something as heavy as a plane get off the ground?

The engine provides the thrust which hurtles the plane down the runway but it can only push the plane forwards not upwards, something called lift does that: At the call V1 Rotate, a pilot pulls back on the control column and the tail of the plane (which is basically an upside down wing) is pulled downwards. When the tail comes down, the angle of the wings is altered and the air flowing over the wings creates lift (due to the Bernoulli effect) and lifts the plane into the air.

Do pilots talk to each other in the air?

Hmm- yes and no - pilots do talk to each other about the weather along their route but they do it via Air Traffic Control wherever possible. So, a pilot will radio Air Traffic Control and say, 'I'm trying to find out what my ride's like?' Air Traffic Control will locate another plane close by and call that pilot up and ask him whether he's encountered any chop or turbulence. The pilot will hear the other pilot's answer but I won't talk to him directly. A plane's radio only covers a 200 mile radius though so over oceanic airspace or other remote regions a pilot may not be able to reach Air Traffic Control. Here he'll call the Inter Pilot Frequency, give his rough co-ordinates and ask for information from any other planes in the vicinity. He will hear directly from other pilots in this instance.

What are those white streaks a plane leave behind?

They look just like long, thin, straight clouds heh? Which is exactly what they are. They are called contrails, which is a shortened version of the phrase 'condensation trail'. They form when warm, exhaust (which contains water vapour) from the jet engines cool, which it does very quickly in the cold and dry air at high altitude. Basically, they are man-made clouds.

Why do commercial airplanes typically fly at 35,000 feet?

35,000 feet is known as the cruising altitude. It the magic point where maximum efficiency and minimum drag intersect. As a plane climbs the temperature around it drops which is great news as a jet engine is more efficient at colder temperatures. The air also gets thinner, so there is less drag. Above 35,000 feet the temperature stops dropping but the air continues to get thinner which means the engine produces less power.

Are hard landings bad landings?

Passengers tend to think that if they feel a bump as the plane touches down the pilot has landed badly but this is not necessarily the case. Pilots refer to a firm touch down as a 'positive landing'. Because a plane cannot brake in the air, a pilot will perform a positive landing on a short runway rather than floating the plane along the runway for a softer touch-down, which would risk running out of runway before the plane could stop. Remember, the wheel brakes do not work unless the wheels are on the runway! The weather also plays a part in determining how hard the pilot comes in to land. On a wet runway a pilot would perform a positive landing to reduce the risk of hydroplaning.

Why don't tyres burst on touchdown?

Before landing a pilot flares the plane pitches up the nose to slow the rate of descent and ensure a comfortable landing. The impact on the tyres is not much more than you'd feel on your feet if you jumped off a five foot wall.

Can a plane fly on 1 engine?

Absolutely. Each engine on the airplane is big enough and powerful enough to keep the plane flying if the other fails mid-route. The pilot would need to descend to around 20,000 feet though where the air was thick enough for that one engine to produce enough power to keep flying.

Why do planes have autopilot?

Have you ever tried to keep your focus for 15 hours straight?! A computer does not lose concentration or need to take a break. Airplanes are not currently set up for automatic take-off though and the auto-pilot is only used to land if the visibility is so bad that a manual landing would be unsafe (because the pilot cannot see the runway!).

If a plane can land itself, why do a manual landing?

Special measures need to be put in place at an airport to allow an automatic landing. The plane uses something called an Instrument Landing System (ILS). The ILS sends out a radio signal to guide the plane onto the ground, vehicles and other aircraft near the runway disrupt this signal so the airport has to keep the area around the runway clear.

What do you use to control the plane in the air?

There are 3 primary controls: elevators; rudders, which are on the tail and ailerons, which are on the wings. The elevators pitch the nose up and down, the rudders turn the nose right and left and the ailerons roll the aircraft.

Does an airplane only carry enough fuel for the journey?

Excess fuel increases the weight of the aircraft which makes the journey more costly. Companies want to reduce costs wherever possible so an aircraft will always carry the minimum amount of fuel. That said, for safety purposes an aircraft must always carry enough fuel to extend the journey by 30 minutes in case it is kept in a holding pattern prior to landing and sufficient to reach the nearest airport in case it needs to divert.

Why do planes sometimes need to dump fuel and where does that fuel go?

Pilots only really dump fuel in emergency situations. If a passenger got sick for example, the plane would need to land at the nearest airport. The plane would be too heavy for the before schedule landing so fuel would be dumped. Fuel dumped at any point before 6,000 feet evaporates before it hits the ground.

Why do cabin lights get dimmed before take-off and landing?

It allows passengers eyes to adjust to the low light. If there is a problem, passengers evacuate the plane more quickly if their eyes have already adjusted.

Why is there a little hole in the cabin windows?

There are actually three panes in every cabin window, an inner, a middle and an outer. The outer window is the actual window, the inner one is there so that passengers don't touch the freezing cold outer pane or scratch or damage it in any way. The hole in the middle pane allows the pressure to equalise between the windows. It also stops condensation building. Modern aircraft no longer have window shades, windows are dimmed at the touch of a button.

Why doesn't the fuel freeze in the air?

At 35,000 feet the air temperature is -55 degrees Celsius (-70 Fahrenheit). The fuel, which is carried in the wings, turns to wax at -49 degrees Celsius and cannot flow through the pipes to the engine. The friction of the air passing over the airplane however warms up the outside of the plane so the aircraft skin is about -20 degrees Celsius. At this temperature the fuel is fine.