How to land the largest passenger aircraft in the world!
Well it has been a while since I’ve put a blog post together. Sorry about that. I have been very busy with various projects including the videos which I hope you have seen and enjoyed. I have previously discussed how we get the A380 into the air, now comes the tricky bit….landing it.
A typical landing weight for the A380 is a quite remarkable 365-370 tonnes! To put that into context, that is only 30 or so tonnes below the maximum takeoff weight of a 747-400! However, due to the quite brilliant wing design, the final approach and landing speed of the A380 is actually quite low. Lower, in fact, than the 747, 767, 777, and 787. In a recently published notice by Air Traffic Control at Heathrow, they state their typical approach speed of an A380 to be 133 knots. By comparison the 777-300 approach speed is stated as 143 knots and the 747-400 as 144 knots. This only adds to the appearance of the A380 flying so slowly near the ground.
We will start our approach around 20 miles from the runway. At this point we would normally be flying at 220 knots. The wing is designed for optimum performance at high speed. If we want to fly slower than around 200 knots we have to change the shape to make it more curved and add extra lift using slats on the leading edge and flaps on the trailing edge. These are the large surfaces you will see moving as we slow down to final approach speeds. There are 8 slat surfaces and 3 flap surfaces on each wing. In addition, the three ailerons also act as flaps in what is termed a droop function.
At this point we would typically reduce our speed to 180 knots. In order to do this we check the airspeed is below the maximum speed for Flap 1, then move the flap lever on the centre console to the Flap 1 position. Unlike Boeing aircraft, which have flap settings which correspond to the angle of flap deployment, Airbus have gone with a simpler nomenclature of Flap 1, 2, 3, and Full. There is also a Flap 1+F position, but this cannot be directly selected. When we first reduce speed and select Flap 1, only the leading edge slats extend. When the speed drops below 205 knots the first stage of flaps automatically extends, resulting in the 1+F (flap) setting. This setting actually gives 20° of slats, 8° of flaps, and 5° of aileron droop. The table below gives the surface positions for each flap lever position.
The speed of 180 knots is a typical speed at which we start down the glideslope to the runway. At busier airports, Air Traffic Control have to ensure aircraft do not get too close together on the approach, but also need to maintain a high flow rate for landing, so accurate speed control is essential. The next speed reduction will be to 160 knots. This requires further flap extension to configuration 2. We will typically hold this speed until 5 miles from the runway, at which time we will select the landing gear down, Flap 3, and start reducing to our final approach speed. The majority of landings are conducted at Flap FULL position, in order to minimise the approach speed. However, there are certain situations where we may wish to land using Flap 3 instead. This results in a slightly higher approach speed, but may be preferable if we are landing, for example, on a day where significant windshear has been reported on final approach and there is an increased possibility of having to perform a go-around. Flap 3 produces significantly less aerodynamic drag than Flap FULL, so the aircraft performance in a go-around would be better.
By 1000 feet above the airfield we will be established on the final approach with the undercarriage locked down, the flaps at landing position, at our final approach speed of around 135 knots. This is a mandatory requirement for safety reasons. We have to be fully set up for landing by 1000 feet above the runway. Now the fun part…Putting 370 tonnes of aircraft onto the runway in exactly the right place. Each runway has a touchdown zone. We MUST land within this touchdown zone. If it becomes obvious we are not going to land by the end of the touchdown zone we have to fly a go-around. This is because our landing performance is calculated based on us landing within the touchdown zone. If we were to land beyond the end of it there is a chance we would not have enough runway left to stop the aircraft. Unfortunately, over the years, there have been a number of accidents which have been caused by pilots not flying a go-around when they have ‘floated’ too far down the runway. Therefore, the British Airways Safe Landing Policy is explicit in allowing either pilot to call go-around if they consider the aircraft will not land in the right place. As always, safety is our number one concern.
But let’s get on with the practicalities of actually landing the aircraft. We will assume this is to be a manual landing, not an automatic one. The vast majority of landings are flown manually. Automatic landings are normally only carried out in foggy conditions. The landing pilot will have taken control of the aircraft just below 1000 feet. They will concentrating on keeping the aircraft flying down the extended centreline of the runway. This is done by imagining the painted line running down the centre of the runway extending beyond the runway itself and coming straight at you. The idea is you keep that pointing straight at you by moving the aircraft left or right as appropriate. It is also essential to keep descending at the correct rate and following the 3 degree glideslope to the runway. This is done partly by reference to the flight instruments, but also by looking outside at the runway. All pilots have a mental image in their mind of how a runway should look, the perspective, and the angle. Over time it becomes automatic to manoeuvre the aircraft on the approach to maintain this visual image. The closer you get to the runway, the more time is spent looking out at it, with just the odd flick of the eyes back inside to look at the instruments to make sure all is ok.
This is the view from the flight deck at 500 feet above the landing runway….
Continuing down the approach to 200 feet above the runway….
The PAPIs (Precision Approach Path Indicator) lights are visible to the left of the runway. We should touch down next to these. If we are on the correct glideslope we will see two red lights and two white lights. More reds than white mean we are too low, and more white than red mean we are too high.
Now just 100 feet above the runway. PAPIs very clear. On the glideslope. Centreline of the runway pointing straight at us.
At 100 feet above the runway the flight control laws change. Pitch trim is no longer automatic, and the previous pitch flight control law changes to a landing ‘flare’ law. This is a modified pitch law which provides smoother control, allowing precise control of vertical speed and touchdown point.
Now only 50 feet above the runway….
At 50 feet above the runway, the flare law introduces an effect which produces a slight nose down tendency. This means the pilot has to start moving the control stick back during the landing manoeuvre, which is known as the flare. In normal conditions the flare height is 40 feet above the runway, but varies slightly due to operational conditions such as wind speed and direction. As we go into the landing the sequence of events is as follows:-
- Start the flare with positive back pressure on the sidestick, raising the nose of the aircraft a couple of degrees, then hold the pitch attitude as you look down the end of the runway
- At around 20 feet close the thrust levers. The aircraft has an automatic call out of ‘RETARD’ as a reminder. It may be necessary to close the thrust levers earlier or later than this depending on the weather conditions.
- Keep looking down the end of the runway. Do not allow the aircraft to roll and if necessary use rudder to bring the nose of the aircraft left or right to point directly down the runway just before touchdown. This is called the ‘crabbing’ technique when there is a crosswind.
- Wait for touchdown, making very minor corrections if required. DO NOT over-control.
- At touchdown the ground spoilers extend to ‘dump’ the majority of the lift, putting weight onto the wheels as the automatic brakes activate.
- Select reverse thrust as required, always a minimum of idle. The A380 only has reverse thrust on the inner engines.
- Use the rudder pedals to keep the aircraft tracking the centreline of the runway.
- Lower the nose gently without delaying touchdown. It must be flown onto the runway and there may be a slight pitch up tendency as the ground spoilers deploy.
Just before touchdown…….
Congratulations! You have just landed 370 tonnes of A380 in Vancouver!
I hope this has been an interesting introduction in how to land an A380. If you have any comments or questions please ask…..
Below is the video of our landing at Vancouver on runway 08L on 11th September 2017, from which the above still photos were extracted. I hope now you have read the above description you can see exactly what First Officer Jon Leggett was doing as he performed this perfect landing.