Air accident expert reveals the parts on a plane that can break without causing it to crash-land

It’s endlessly repeated – air travel is one of the safest modes of travel.

And this article will show you just why using the expert knowledge of safety and accident investigation lecturer Dr Simon Place, from Cranfield University.

Here he explains which bits an airliner can lose, or suffer damage to, without it falling from the sky using, in some instances, real-world examples of extraordinary landings by planes that have lost key parts, including the wheels, tail fin and even the wing…

Pilots

All airliners fly with at least two pilots. They choose different menu options in case of food poisoning

[On airliners] there are two pilots, and the aircraft can be flown with just one in an emergency. 

This is why they still choose different menu options in case of food poisoning.

Wings

An Israeli military F-15 landed safely after losing one wing in 1983

An Israeli military F-15 landed safely after losing one wing in 1983

Aircraft rely on wings to generate lift and without them flight is generally not possible.

Wings are able to flex up and down by a limited amount and can withstand normal buffeting in flight and minor impact from birds and so on.

It is practically unknown for structural failure to occur.

However, an Israeli military F-15 did manage to land after losing one wing in 1983.

Winglets

Winglets are fitted for aerodynamic purposes and are not vital to a plane's stability

Winglets are fitted for aerodynamic purposes and are not vital to a plane’s stability

Winglets are fitted to many aircraft at the end of each wing – they help reduce drag.

These have been known to be damaged and the aircraft can still fly normally.

Flaps

If the flaps fail, an aircraft would still be able to land safely, said Dr Place. But it would be a fast touch-down and the pilots would find handling the plane harder

If the flaps fail, an aircraft would still be able to land safely, said Dr Place. But it would be a fast touch-down and the pilots would find handling the plane harder

These can be damaged (or simply not work) but the aircraft can still land. 

However, the landing speed will increase and the aircraft would be harder for the pilot to handle.

Fuselage

The main body of the aircraft protects passengers from high-speed air flow and lack of oxygen. Small holes can be tolerated but cause the aircraft to de-pressurise (with the need for oxygen masks). A rapid descent must be carried out urgently. 

The aircraft cannot cope with large scale damage.

Fin and rudder

A USAF Boeing B-52H Stratofortress suffered an exceptional failure in 1964 when the vertical fin sheared off in turbulence. It landed safely

A USAF Boeing B-52H Stratofortress suffered an exceptional failure in 1964 when the vertical fin sheared off in turbulence. It landed safely

The fin provides stability for the aircraft and the rudder makes the aircraft move left and right. 

It is very difficult to control the plane without the fin. 

An exceptional case occurred when a USAF Boeing B-52H Stratofortress suffered an exceptional failure in 1964 when the vertical fin sheared off in severe turbulence.

Despite the problems this created the crew was able to land the aircraft safely.

Without the rudder the aircraft can still be controlled using ailerons.

Tail-plane and elevator

The tail-plane is the very end of the aircraft and the elevators are the horizontal stabilisers

The tail-plane is the very end of the aircraft and the elevators are the horizontal stabilisers

In the 1990s, Nasa conducted a research program in 'propulsion controlled approach'. A specially equipped MD-11 aircraft was flown and landed using engines alone (pictured)

In the 1990s, Nasa conducted a research program in ‘propulsion controlled approach’. A specially equipped MD-11 aircraft was flown and landed using engines alone (pictured)

The tail-plane helps provide stability and the elevator controls the ‘pitch’ of the aircraft (up and down). Without these the aircraft cannot be controlled.

However, in the 1990s, Nasa conducted a research program in ‘propulsion controlled approach’. 

A specially equipped MD-11 aircraft was flown and landed using engines alone. This shows that it is possible to land an aircraft without the normal flight controls.

Engines

At Heathrow Airport in 2008, the formation of ice restricted the fuel flow in the engines of British Airways flight BA38 (a Boeing 777). The aircraft was only a short distance from the airport and the crew carried out a successful emergency landing

At Heathrow Airport in 2008, the formation of ice restricted the fuel flow in the engines of British Airways flight BA38 (a Boeing 777). The aircraft was only a short distance from the airport and the crew carried out a successful emergency landing

Engine failure is serious, but does not lead to fatalities in the majority of cases. 

Normally when a pilot describes ‘losing an engine’ they mean that the engine has stopped producing thrust.

This could be for a variety of reasons – for US Airways Flight 1549 (which ditched on the Hudson River in New York) this was due to birds being sucked into both engines. 

At Heathrow Airport in 2008, the formation of ice restricted the fuel flow in the engines of British Airways flight BA38 (a Boeing 777). The aircraft was only a short distance from the airport and the crew carried out a successful emergency landing.

Qantas flight QF32 was an Airbus A380 that suffered an uncontained engine rotor failure  on 4 November, 2010, having just left Singapore (pictured). It landed safely

Qantas flight QF32 was an Airbus A380 that suffered an uncontained engine rotor failure on 4 November, 2010, having just left Singapore (pictured). It landed safely

And Qantas flight QF32 was an Airbus A380 that suffered an uncontained engine rotor failure (or rotor burst) on 4 November, 2010, having just left Singapore. 

Expert flying skills of the pilots on board, plus the design of the aircraft, resulted in a successful landing.

Flight BA009, meanwhile, lost thrust in all four of its engines in the skies above Indonesia in 1982 due to volcanic dust. The crew managed to eventually restart all the engines although a great deal of internal damage occurred.

Ailerons

Ailerons help to turn the aircraft but aren't essential as the rudder is also used for this purpose

Ailerons help to turn the aircraft but aren’t essential as the rudder is also used for this purpose

Why flying is the safest mode of transport 

Next time you are on a flight, says Dr Place, you can take some comfort from the high standards in design, maintenance and operations that makes flying one of the safest forms of travel.

Modern passenger aircraft are built by different companies, but they are often similar in terms of safety and design. Every aspect of an aircraft, including the materials, systems and overall design are checked and verified as part of the certification process. The latter is conducted by an external authority with the power to insist on changes, and if necessary to ground an aircraft. Not only is the design proven, but pilots, cabin crew and maintenance engineers are all trained and must pass rigorous checks.

In describing the aircraft as a whole, there is a back-up for almost everything. The body of the aircraft, wings and flight controls make up the structure. The engines provide the power and propel the aircraft through the air and run all on-board systems – hydraulic, air, electrical and avionics systems.

These in turn make sure that aircraft can be flown safely from the flight deck, the engine gets enough fuel and the cabin stays at normal pressure and temperature. There are back-up systems for the landing gear and brakes, plus fire protection and emergency oxygen.

Almost all on-board systems are duplicated on a modern aircraft, so that failure of any one system should not cause an aircraft accident.

One of the design basics is that should be no ‘single-point’ failures. Such systems include the principle of ‘redundancy’ so that aircraft remains controllable in the event of a system or component not working.

Jet aircraft typically fly at between 32,000 and 38,000 feet (six and seven miles) high for most flights, where the engines are most efficient and there is less air resistance. The main body of an aircraft (fuselage) is a large cylindrical tube, which is the strongest and most efficient way to withstand the low air pressure at these altitudes. The materials used are well tested and structural failures are very rare. Those that do occur have been due to an error in operation or maintenance. 

Ailerons make the aircraft turn and so without these, flight becomes more difficult.

However, it is still possible to turn the aircraft using the rudder.

Air-conditioning (AC) pack

Pressurisation is required so that passengers have air to breathe whilst the aircraft is flying at high altitude. For this reason all aircraft have two AC packs in case of failure. If one fails, the aircraft must descend just in case the other one were also to fail. Without any pressurisation, oxygen masks would drop and the aircraft would make an emergency descent.

Hydraulic systems

There are normally three separate hydraulic systems on a large aircraft and these are the primary way to move the flight controls (rudder, elevator, ailerons and flaps etc). It is therefore essential that at least one hydraulic system is available, otherwise the aircraft cannot be controlled. As mentioned above, it has been shown that in exceptional cases, the engines can be used to steer the aircraft, but this has only worked in one or two cases.

Electrical systems

There are a number of separate electrical systems on the aircraft, each of which powers different systems. Again, the objective is to increase safety by making sure that essential systems will still operate if part of the electrical system fails. One action that might occur is that in-flight entertainment and other non-essential items might be switched off to conserve power.

Autopilot

The autopilot helps the aircraft to fly automatically. There are still two pilots but they do not have to hold on to all the controls. There are normally two autopilot systems, because without one of them the plane would need to be ‘hand-flown’. Pilots are able to do this easily, but it is impractical for a long flight. It would also mean that certain complex approaches in bad weather may be prohibited.

Radios

There are at least two or three radio systems on the aircraft to enable communication with the ground, air traffic control etc. Special procedures exist for what to do if a plane loses the ability to communicate.

Wheels and brakes

A LOT 767 made a safe emergency landing in Warsaw after the landing gear failed to come down

A LOT 767 made a safe emergency landing in Warsaw after the landing gear failed to come down

The aircraft landing gear is designed to support the weight of the aircraft when landing and provide braking.

As well as wheel brakes, aircraft also have ‘reverse thrust’ from the engines to slow the aircraft when it lands.

From time to time, landing gear failures do occur, either partially or completely. It is not possible to have a back-up for the undercarriage wheels. However, there have been some remarkable examples of the pilot and aircraft coping with unusual events.

In one extreme case, an aircraft landed with no landing gear at all. This happened to a LOT 767 at Warsaw in 2011, where the landing gear did not come down due to a hydraulic leak. After flying around and trying to find the problem, a landing was attempted and the aircraft effectively skidded to a halt on the runway. 

There were no injuries during the emergency. 

In the case of TAM A332 at New York in September 2012, the nose gear can be seen to be at 90 degrees to the direction of flight, during the first attempt to land. On the final approach, and just before landing, the nose gear straightened just before the aircraft touched down.

A TAM A332 at New York in September 2012 made one approach with the nose gear at 90 degrees to the direction of flight

A TAM A332 at New York in September 2012 made one approach with the nose gear at 90 degrees to the direction of flight

In 2005, a Jet Blue Airbus A320 landed at Los Angeles, California, with the nose gear at 90 degrees. 

Despite generating a shower of sparks, as the rubber was worn away, the aircraft made a controlled landing with no fire and no injuries on board. 

Dr Simon Place is a Senior Lecturer at the Safety and Accident Investigation Centre, Cranfield University. The Centre has an international reputation for award-winning teaching, research and consultancy in transportation safety management, human factors, airworthiness and incident/accident investigation.



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