What speed does a Boeing 747 Jumbo Jet take-off and land at?
A look at the speed the at which the Boeing 747 takes off and lands
What speed does a Boeing 747 take off at?
A fully loaded Boeing 747 ‘Jumbo Jet’ on a normal long haul flight would take off at a speed of around 160 knots which is 184 mph. The calculated take-off speeds vary depending on environmental conditions, runway length and weight.
What speed does a Boeing 747 land at?
A 747 ‘Jumbo Jet’ would typically land at a speed of about 145kts-150kts (166mph-172mph), depending on the landing flap setting selected.
Most airlines and aircraft have a facility to de-rate thrust (or use assumed temperatures) for take-off. This occurs on runways where the aircraft has extra performance in hand e.g. the aircraft does not need the full length of the runway to take-off. Large commercial aircraft rarely use their full engine power for take-off as most runways at large airport long enough to support a reduction in thrust. Take-off thrust might be as little as 75% of the maximum thrust.
Taking off with reduced thrust reduces the temperature the various components in teh engine are exposed to. This in turn can significantly reduce engine wear and tear and thus maintenance costs, and ultimately extend the life of the engine.
Additional Speed for Landing
The greater the flap setting, the lower the take-off and landing speed. Jumbo Jets typically land at Flap 25 or 40. Pilots generally fly the approach speed faster than the actual touchdown speed to allow a speed ‘buffer’ in case of any airspeed fluctuations. This additional speed is ‘bled off’ during the flare or plain terms, the excess speed reduces as the nose is raised just before touchdown. In light wind conditions we would add 5 kts to the approach speed but in strong wind conditions up to 20kts can be added.
B747-400 Maximum Take-Off Weight
The xaximum take-off weight for the B747 is 396,000 KGS / 875,000 LBS
B747-400 Maximum Landing Weight
The Maximum landing weight for the B747 is 285,000 KGS / 630,000 LBS
Ever wondered how much fuel a Jumbo Jet burns? This page might be of interest.
How much fuel does a Jumbo Jet (Boeing 747-400) burn?
What fuel does a jumbo jet use between London and New York?
How Much Fuel Does a Jumbo Jet Burn?
The four engines of the Boeing 747 Jumbo Jet burn approximately 10 to 11 tonnes of fuel an hour when in the cruise. This equates to roughly 1 gallon (approximately 4 litres) of fuel every second. It can carry a maximum of 238,604 liters of fuel and it has a range of about 7,790 nautical miles.
A Jumbo Jet (Boeing 747-400) flying from London to New York burns approximately 70,000 kilograms of fuel. Jet fuel has an approximate specific gravity of 0.85, which therefore equates to 82,353 litres.
Therefore, the cost of the fuel (based on 1 litre costing 31 pence) required to fly from London to New York is approximately £18,500 (€23,600). The cost of fuel for a a jumbo jet carrying 450 passengers, would work out as about £41 (€52) per person.
The worldwide Jumbo Jet fleets are getting smaller with none now in operational service with UK airlines. Both British Airways (BA) and Virgin Atlantic retired their B747 fleet earlier than planned due to the reduction in travel demand as a result of the COVID-19 pandemic in 2020. Some airlines continue to operate the B747-8, the latest passenger version of the Jumbo Jet, such as Lufthansa. Boeing plans on stopping production of the Jumbo in 2022.
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Why do Passenger Planes Fly so High in the Sky?
Why do aircraft fly at high altitude?
Why Do Commerical Aircraft Fly So High?
The reason passenger aeroplanes have a high cruising altitude (between 30,000 ft – 42,000 ft), is due to the high levels of fuel efficiency they achieve at that level. At high altitude, aircraft fuel burn is much less per mile travelled when compared to low level flight because of the reduced aerodynamic drag and improved jet engine efficiency. This means a jet aeroplane can fly much faster whilst using less fuel at a high altitude.
Flying above 30,000 ft also has the benefit of allowing the aeroplane to fly above most weather systems making it more comfortable for the passengers.
This article will look at the main two reasons why passenger planes fly so high; improved engine efficiency and reduced air density.
Engine Efficiency, Airspeed & Density
Modern jet engines on commercial passenger aircraft (referred to as Turbo-Fans), are most efficient when they are operated at high altitude. This is because jet engines gain an efficiency benefit when they are run at close to their maximum RPM limit or maximum (exhaust) temperature limitations. At lower altitudes, the engines can only be run at maximum thrust during take-off or perhaps the climb or else the aircraft would quickly exceed its maximum speed limitation. If you tried to fly straight and level at 10,000ft with more than 70% thrust set, you would quickly overspeed most commercial jet aircraft. At 70% thrust, the engine isn’t running very efficiently.
As the aircraft climbs in altitude, the jet engines produce less thrust (as the air is thinner), but it maintains a high compression ratio and thermal efficiency. As the air is thinner, the plane is able to achieve a much higher True Air Speed (TAS) than lower down, meaning the aircraft travels much faster whilst the engines burn less fuel.
The higher in the air you go, the less dense the air is, or put in a different way, the thinner it is. Therefore, there is less resistance (or friction) to stop the aircraft moving through the air. This is called resistance “drag”. This means that less thrust is needed from the engines to propel the aircraft through the air, or in other words, it the aircraft can fly faster for the same high (and therefore efficient) thrust setting.
Here’s an example to demonstrate how the air thins out as you get higher; imagine moving your hand through water and golden syrup. If you want to move your hand through both of these liquids at the same speed, you need much more effort to move your hand through the golden syrup than the water. This is the same principle with an aircraft flying at a higher altitude when compared to a lower altitude.
If you found this article of interest, check out our page on How fast do planes fly?
What happens if all the plane’s engines fail in the air?
If all the aircraft’s engines fail, will the plane still fly or will it fall out of the sky?
Can a plane fly if all its engines have failed?
A passenger aircraft will glide perfectly well even if all its engines have failed, it won’t simply fall out the sky. Infact it can fly for around 60 miles if it loses its engines at a typical cruise altitude of 36,000ft. Aircraft are designed in a way that allows them to glide through the air even with no engine thrust. The chances are that if you’ve flown on a plane, it will have been gliding during the descent when the engine is commanded by the pilots to produce very little thrust/power. For most of the descent, the engine is running at ‘idle’ (minimum thrust) – it maintains it’s forward airspeed by descending.
How Planes Keep Flying with no Engines
Aircraft are able to fly because of the movement of air passing over the wings and as long as this process continues (i.e. the aeroplane is moving forwards at a suitable speed), the aircraft will continue to fly. If both engines fail, the aeroplane is no longer being pushed forwards through thrust, therefore in order to keep the air flowing over the wings, the aircraft must exchange energy through losing altitude (descending) in order to maintain forward airspeed. If the aircraft tried to maintain height with no thrust, it would stall (which would cause it to fall out the sky). However, pilots are trained for such occurances and will maintain a suitable air speed to keep the aeroplane flying.
The aircraft doesn’t have to lose altitude particularly rapidly to keep flying and therefore if both engines were to fail a high altitude, the aircraft may have as much as 20 – 30 minutes of airbourne time to find somewhere to land before it reaches the ground.
How far can a passenger jet glide if all its engines have failed?
A passenger jet could glide for up to about 60 miles if it suffers a total engine failure at its cruising altitude. Here’s an example. A typical commercial aircraft has a lift to drag ratio of around 10:1. This means that for every 10 miles it travels forward it loses 1 mile in altitude. If an aircraft is at a typical cruise altitude of 36,000 (which is 6 miles up) and loses both engines, it can therefore travel a forward distance of 60 miles before reaching the ground. Therefore, if such an incident occurs within 60 miles of a runway, the aircraft could potentially be landed safely.
US Airways Flight 1459
Rest assured, dual engine failure is almost unheard of. We all know about the story of US Airways flight 1459 landing in the Hudson River in New York after both its engines were destroyed by birds, but that really was exceptional – and everyone survived thanks to the quick actions of the actions of the pilots Captain Chesley Sullenberger (‘Sully’) and First Officer Jeffrey Skiles.
Air Transat Flight 236
One other exception was Air Transat Flight 236. The plane had a fuel leak causing both engines to fail at approximately 65 nautical miles from Lajes Air Base in the Azores. With an average descent rate of 2,000 fpm, the aircraft glided without power to the airbase where the crew carried out a successful landing about 17 minutes after the last engine failed.
Gliding Every Flight
The lower the engine power, the less fuel the engines burn. On most flights pilots try and burn as little fuel as possible and part of this process involves descending the aircraft towards the destination airport at idle (minimum) thrust. When the thrust is at it’s minimum setting, it isn’t really producing any meaningful thrust at all so the aircraft is effectively gliding. Therefore you will have experience the aircraft gliding on almost every flight you have been on!
If you found this article of interest, you may find our article about how both engines on a passenger jet can fail to be worth a read.
Can a passenger jet fly with only one engine?
A twin-engine plane can fly perfectly well on only one engine. In fact, it can even continue the take-off and then safely land with just one engine. An engine failing in flight is not usually a serious problem and the pilots are given extensive training to deal with such a situation.
What do the pilots do if an engine fails?
All pilots are taught to abide by a basic aviation rule regardless of the severity of any airborne event. This is summarised by the acronym; Aviate, Navigate, Communicate. The crux of this is to ensure the flight crew prioritise flying the aircraft first. This is ensuring that it is fully under control before verifying or correcting its navigational path and making sure it is flying where the pilots want it to fly, i.e. not heading towards a high mountain. This is followed by communicating the relevant information to all the appropriate parties, starting with Air Traffic Control.
There are several different severities of engine problems that might require slightly different responses from the flight crew, defined by the level of urgency. For example, if an engine fire is indicated, this requires an immediate response after ensuring the aircraft is under control (‘Aviating’!). If for example, there was an engine fire indication, there are several ‘Memory Actions’ for the flight crew to complete. This will involve completing the engine shutting down, and subsequently deploying the fire extinguishers from memory, without the aid of a checklist.
Once the engine is shutdown…
Once the engine is safely shutdown and the fire extinguished, the crew would reference that the ‘Engine Fire Memory Actions’ had been completed correctly by referencing the appropriate checklist. The checklist will then detail further tasks for the crew to complete that were not included in the ‘Memory Actions’.
On the other hand, if it was a straight forward engine failure with no damage indicated, there would be no ‘Memory Actions’. In this case, the pilots would follow a checklist to diagnose and potentially restart the engine. Any engine failure on a twin-engine aircraft will require the pilots to land the aircraft at the nearest suitable airport. Statistically this is unlikely to be your destination unfortunately!
‘Memory Actions’ for an Engine Fire or Severe Damage
Different types of aircraft may have different names for the various switches, handles and procedures, but the basic principle remains the same; to safely shut down and secure the engine in a timely manner. These steps are typically as follows:
- Disengage the Autothrottle – this stops automatic thrust control.
- Reduce the thrust on the damaged engine to idle – this involves moving the respective thrust lever all the way back to its idle position.
- Fuel control switch to off – this closes the fuel valve, stopping fuel flow to the engine.
- Pull the fire handle switch – this typically disengages the electrical, hydraulic, pneumatic and fuel systems from the respective engine.
- If a fire is still indicated in the engine, turn the engine fire handle to discharge the first fire bottle. After waiting around thirty seconds, if fire indications are still present turn the fire handle the other way to discharge the second fire bottle.
Each of these actions MUST be verified by both crew members. For example, the pilot completing the checklist will touch the respective control switch, such as the Fuel Control Switch, and the other pilot will confirm they are about to action the correct switch prior to moving it. It is required to be completed at a reasonable pace (not rushing through) to ensure the wrong engine is not shutdown.
The engines are designed to contain any fire within it’s housing to stop it spreading to any other part of the aircraft. However, if an engine fire continues after this procedure has been followed, the flight crew may need to consider an immediate landing. In very severe cases, this may mean a forced landing away from any airport (i.e. in a field or suitable area). However, rest assured, the potential of such an occurrence is unbelievably remote.
Reasons why an engine might fail or be shut down by the pilots:
- Severe Damage (for example a turbine/fan blade separation or bird strike)
- Separation from the aircraft
- Stall (an engine stall is different to the aircraft wing stalling)
- Fuel Starvation or Contamination
- Flame Out
- High vibration
- Limitations exceeded (too hot for example)
What are the implications of an engine failure?
Asymmetric Thrust / Controllability
The first implication is the asymmetric thrust that will be produced. If an engine fails and is shutdown, the other engine’s thrust is increased to stop a decay in airspeed. This results in the aircraft wanting to turn away from the working engine and entering a turn. If left unchecked, this will result in loss of control of the aircraft. This usually has to be corrected manually by the pilots through the rudder pedals. Any time there is an adjustment in speed, thrust or altitude, the pilots will need to ensure the aircraft remains balanced and in control.
With 50% of the aircraft’s power no longer available it will not be able to maintain its cruise altitude. If the aircraft is in the cruise at the time of the failure (which is statistically most likely), a descent will need to be quickly initiated to an intermediate altitude which can be maintained by the remaining engine (typically between 15,000ft – 25,000ft for most aircraft, depending on weight).
Many of the aircraft’s systems are powered by its engines. These usually include the Hydraulics, Pneumatics (which provide cabin air) and Electrics. Whilst these systems have a level of redundancy (in part through the other engine), some parts of the system may no longer be available which could affect aircraft handling and performance.
Losing an engine often requires a different flap configuration for landing, in part due to the performance that must be achieved were the aircraft to abort the approach/landing and conduct a ‘go-around’. Landing with a lower flap configuration increases the landing distance required and therefore the pilots must carefully consider which airport they elect to land at. Airport weather, runway length and aircraft weight all play a part in these considerations.
What is the most dangerous phase of flight to have an engine failure?
For a pilot, the most testing place to have an engine failure is during the take-off phase, i.e. the start of the ground roll until the aircraft passes around 1,500ft. However extensive training is provided for this scenario and the pilots are tested on their reactions to such an event every six-months in the simulator. They must safely deal with such a scenario to a high standard or they will not be allowed to continue to fly until adequate performance is demonstrated.
During the take-off, the pilots use a carefully pre-calculated speed called V1 (pronounced “Vee One”) to determine their actions were an engine to fail. During the take-off roll, if an engine failure occurs before the V1 speed, the pilots must abort the take-off, which is known in the industry as a ‘Rejected Take-Off’ or RTO for short. If they elected to continue, the aircraft would not gain enough speed to take-off with the remaining engine power available on the runway length remaining.
Continuing the take-off
If a failure occurs after V1, the pilots must continue the take-off and get airborne. If the pilots tried to abort the take-off at this speed, there would not be enough runway left to safely bring the aircraft to a stop.
Once the aircraft is in the air, the pilots will just concentrate on flying and controlling the aircraft until approximately 400ft. At this altitude, they will review what has occurred and carry out any ‘Memory Actions’ if required.
What happens if you lose an engine on an aircraft with more than two engines?
A four-engine aircraft losing a single engine is even less of an issue. A few years ago, a four-engine Virgin Atlantic Boeing 747-400 (a jumbo jet) had an engine failure over the United States en-route to the UK. The aircraft continued all the way over the Atlantic Ocean back to the UK without any further problems.
If a four-engine aircraft lost more than one engine, it can still potentially fly at a lower altitude and will perform better at lower weights.
What is the likelihood of an engine failure?
With the significant technological improvements that have occurred over the last few decades, engines are built to an incredibly high standard and are very robust as a result. Over the last few decades, engines failures have become increasing rare to the point that the majority of pilots will now only see an engine failure in the simulator over the course of their career.
Safety statistics suggest that less than one in every one million flights will have an engine failure or forced engine shutdown in the air or on the ground. This works out at approximately 25 such failures a year across commercial aviation.
If a failure does occur, the engine is designed to contain any problems and stop it spreading to the rest of the aircraft. For example, if one of the fan blades at the front of the aircraft detaches, the engine casing should stop it leaving the engine.