“Take-off slot”
When there is an increased demand on Air Traffic Control (ATC), they may issue flights with a Calculated Take-off Time (CTOT) or ‘slot’. This is the time before which the flight is not allowed to get airborne.
If bad weather is forecast at the destination airport, it is likely that flights will have to wait in the sky before their turn to land. This increases the workload on ATC and results in aircraft using more fuel. If the delays become too great, flights may have to divert to another airport.
Rather than all flights arriving at the same time, it is better for an aircraft to wait on the ground until a time at which ATC can safely accept it into the traffic flow. Once airborne in accordance with their ‘slot’, the pilots know that their delay at the destination will be much less, greatly reducing the necessity of a diversion.
“Completing the last of the paperwork”
As much as airlines are trying to reduce paper use in daily operations, some requirements still remain. For every flight, the pilots are issued with a loadsheet and a NOTOC (Notice To Captain).
Complied by a special department in the airline, the loadsheet tells the pilots the weight and balance information of their aircraft. From this, they can tell how many passengers and bags are on board, how much cargo and how much fuel has been loaded. They can then accurately calculate their speeds and engine power required for take-off.
The NOTOC informs the crew of any special cargo that is being carried onboard. This could be from the benign such as fruits and vegetables, to items classified as dangerous goods such as batteries and explosive gases. This confirms to the crew that the cargo is being carried safely and enables them to respond in the correct manner should any problems arise.
Before the aircraft departs, the captain must sign a copy of the loadsheet and NOTOC, and hand it to the ground staff. This is to ensure a physical copy of the paperwork remains safe on the ground should anything happen to the aircraft.
“V1… Rotate”
To the outside observer, take-off may appear to be a beautiful art form. However, to pilots, it’s a calculated science. For every take-off, pilots calculate the exact speed at which they will pull back on the controls, rotating the aircraft into the sky. This speed, known as VR, is dependent on factors such as aircraft weight, wind velocity, runway length and condition, airfield elevation and air temperature and pressure.
Whilst we always anticipate a normal take–off, we always plan for the event of something not going according to plan. Should the aircraft suffer an engine failure or other problem during the take-off run, we need to know whether we should continue or abort. When moving at speeds of over 240km/ph, you have very little time to react. This why we have a decision speed – V1.
Should we decide to stop the take-off before reaching the V1 speed, there will be enough runway remaining on which to stop safely. Once beyond this speed, it is safer to take the problem into the air and then deal with it accordingly. On a twin engine aircraft, even in the case of an engine failure or fire, the aircraft can still climb safely away from the ground on the power of the remaining engine.
“I have control”
The flight deck of a modern airliner can be a very busy place. With two pilots always at the controls, duties are divided into the Pilot Flying (PF) and the Pilot Monitoring (PM). This enables one pilot to concentrate solely on the flight path of the aircraft. The other pilot then has the capacity to operate the radio, run checklists and liaise with cabin crew whilst still monitoring the actions of the PF.
Whenever there is a need for these duties to swap over, for example when one pilot needs the bathroom, it’s important to know who is PF. In order to do this, when assuming the PF duties, pilots verbally confirm this acceptance by saying “I have control”.
This may seem excessive in times of low workload in the cruise, but during non-normal events it’s very different. When complex checklists are being completed, it’s imperative that it is clear who exactly is responsible for maintaining the safe path of the aircraft.
“Positive rate, gear up”
Not long after the call of rotate, comes the call of “positive rate, gear up” (for you super avgeeks, this is the Boeing terminology. Airbus uses “positive climb, gear up”)
The call of ‘positive rate’ (or climb) is made by the Pilot Monitoring (PM) as an indication that the aircraft is safely climbing away from the ground. This is confirmed by checking that the altimetre indication is increasing. At this point it is safe to retract the landing gear.
On hearing the call of “positive rate”, the Pilot Flying (PF) then says “gear up”, the cue for the PM to move the landing gears up.
“The turbulence is caused by a jet stream”
We all know what turbulence is, but what is this ‘jet stream’ which is causing it? A jet stream is an area of locally focused fast-moving air which can often be in excess of 240km/ph. When flying in the core of the jet, where the winds are the fastest, flight conditions are often smooth. However, when flying in the area between core and the normal air outside the jet, conditions can often be bumpy.
It’s very much like watching a fast-moving river. In the centre, where the water is unobstructed, the water is fast and smooth. However, at the edges
where the flow comes into contact with rocks and trees, the water is often rough and turbulent.
“Awaiting a tug to push back from the gate”
Most commercial aircraft are unable to reverse. As a result, they require the assistance of a tug or tractor to ‘pushback’ from the gate. The tug either attaches to the nose wheel using a tow bar, or by clamping onto the nosewheel and lifting the front of the aircraft off the ground.
On parking stands where the aircraft faces the terminal building, aircraft are reliant on the arrival of the tug for the flight to commence. No tug, no pushback.
“The APU isn’t working”
Tucked away in the tail of an airliner is a small engine, the Auxiliary Power Unit – the APU. When on the ground with the engines shut down, the APU provides the aircraft with electrical power and also air to cool the cabin. Whilst the APU is a great addition to the aircraft, it is not necessarily needed for flight.
In order to reduce delays and cancellations, all aircraft are allowed to depart safely with certain systems not working, as outlined by the manufacturer in a special manual. The APU is one of these items, so whilst it does not compromise the safety of the flight, it can mean that there is no air conditioning until the engines have been started.
“Searching for a passenger’s bag”
One of the biggest causes of flight delays is passengers not arriving at the gate on time. If a passenger fails to arrive at the gate on time, the pilots and ground crew may decide to offload the passenger.
If they only have hand luggage, this is a ten second job on the computer. However, if they have checked in baggage, it creates a problem. Due to security concerns, it is normally not allowed to depart with the offloaded passenger’s baggage still onboard. As a result, the ground staff must remove the bag which can be a time-consuming process.
On larger aircraft, like the B787 Dreamliner, bags are scanned as they are loaded into specialised containers. These containers are then loaded into the aircraft holds. If the ground staff needs to find a particular bag, they know exactly in which container the bag has been loaded. This saves the staff from searching through hundreds of bags, minimising the delay to the flight.
“There is broken cloud at 1500ft”
One of my personal pet-hates in announcements to passengers is the use of over technical terms, “broken cloud” being one of them.
In order to portray to pilots how much cloud there is at an airport, the cloud coverage is measured in Octas, or eighths of the sky. One to two Octas coverage is referred to as ‘few clouds.’ Three to four Octas is ‘scattered clouds.’ Five to seven Octas is ‘broken cloud’ and eight Octas is ‘overcast’.
So, if your pilot refers to the cloud being ‘broken’, it means that it’s more cloudy than not, but with some breaks between them.
“We have entered a holding pattern”
When there’s congestion ahead, unlike cars, aircraft can’t just stop and wait. They always have to keep moving forwards. When approaching the destination airport, if there is a build-up of arriving aircraft, flights may have to wait their turn to land. In order to reduce the workload for ATC, airports publish holding patterns in which aircraft fly to await their turn to land. These are often referred to as ‘stacks’ as multiple aircraft can use the same pattern but are ‘stacked’ up above each other at 1000ft intervals.
As the aircraft progress in the queue, ATC clear them down in the stack before they are then directed from the bottom of the stack towards the landing runway.
“Delays due to poor visibility”
One reason why aircraft may have to enter a holding pattern is if the visibility at the destination has deteriorated. In order to land, pilots have to legally satisfy the published visibility requirements. This varies from airport to airport and runway to runway.
The most common type of approach aircraft make to runways is using an Instrument Landing System, or ILS. The basic version of an ILS, Category 1 (CAT 1), requires 550metre visibility on the ground before the pilots can start the approach. If the reported visibility is below that value, the aircraft must wait until it improves.
At larger airports, particularly those regularly affected by fog, the ILS system can be upgraded to allow aircraft to land in visibility lower than 550metre. CAT 2 systems allow aircraft to land if the visibility is at least 300metre and CAT 3 systems reduces this figure to as low as 75metre.
“Cabin crew, doors to manual and cross check”
At the end of the flight as you approach the gate, you’ll hear one of the pilots say this phrase over the PA system. This is not an indication for passengers to get up from their seats, but a very important safety command to the cabin crew.
Whilst the doors are there to allow passengers to board and disembark via steps or a jetty, they are also there to allow rapid exit down evacuation slides in an emergency.
Tucked away in each door is the evacuation slide. On departure, the cabin crew will place the doors into ‘automatic’. By moving a lever on the door, the slide attaches to the bottom of the door frame. Should the door be opened when in automatic mode, the slide will be dragged from its stowage and will then inflate.
Understandably, when arriving at the gate on a normal flight, this slide deployment isn’t particularly desirable. As a result, at an appropriate time the pilots instruct the cabin crew to return the doors to manual mode. This detaches the slides from the door frame, allowing the door to be used as normal.
Charlie Page
