Why do planes crash? Here are the five most common causes

Investigators in the wreckage of a crashed plane in Alabama in 2013. Image: Getty.

News of any terrible air accident instantly raises questions about aircraft safety and the threat of terrorism. Until the facts are known, however, it is unwise to speculate on what might actually have caused a specific crash.

What we do know is that there are several causes that are more likely to occur than any other. Here are five. 

1. Pilot error

As aircraft have become more reliable, the proportion of crashes caused by pilot error has increased and now stands at around 50 per cent.

Aircraft are complex machines that require a lot of management. Because pilots actively engage with the aircraft at every stage of a flight, there are numerous opportunities for this to go wrong, from failing to programme the vital flight-management computer (FMC) correctly to miscalculating the required fuel uplift.

While such errors are regrettable, it is important to remember that the pilot is also the last line of defence when things go catastrophically wrong. In January 2009 an Airbus A320 hit a flock of geese over New York City. With no power, the captain, Chesley Sullenberger, had to weigh up a number of options and act quickly. Using his extensive flying experience and knowledge of the plane’s handling qualities, he elected to ditch the aircraft in the Hudson River.

The 150 passengers were not saved by computers or any other automated system. They were saved by the two pilots – the very components that techno-enthusiasts claim can be replaced by computers and ground controllers.

2. Mechanical failure

Equipment failures still account for around 20 per cent of aircraft losses, despite improvements in design and manufacturing quality. While engines are significantly more reliable today than they were half a century ago, they still occasionally suffer catastrophic failures.

In 1989, a disintegrating fan blade caused the number one (left-hand) engine of a Belfast-bound British Midland Boeing 737-400 to lose power. Hard-to-read instrumentation contributed to the pilots’ misreading of which engine was losing power. Confused, the pilots shut off the number two (right-hand) engine. With no power, the aircraft crashed short of East Midlands Airport’s Runway 27, killing 47 and injuring many, including the captain and first officer.

More recently, a Qantas A380 carrying 459 passengers and crew suffered an uncontained engine failure over Batam Island, Indonesia. Thanks to the skill of the pilots, the stricken aircraft landed safely.

Sometimes, new technologies introduce new types of failure. In the 1950s, for example, the introduction of high-flying, pressurised jet aircraft introduced an entirely new hazard – metal fatigue brought on by the hull’s pressurisation cycle. Several high-profile disasters caused by this problem led to the withdrawal of the de Havilland Comet aircraft model, pending design changes.

Southwest Airlines Flight 1248. Image: Gabriel Widyna/airliners.net.

3. Weather

Bad weather accounts for around 10 per cent of aircraft losses. Despite a plethora of electronic aids like gyroscopic compasses, satellite navigation and weather data uplinks, aircraft still founder in storms, snow and fog. In December 2005, Southwest Airlines Flight 1248, flying from Baltimore-Washington International Airport to Chicago Midway International Airport, attempted to land in a snowstorm. It skidded off the runway and crashed into a line of cars, killing a toddler.

One of the most notorious bad-weather incidents occurred in February 1958 when a British European Airways twin-engined passenger aircraft crashed while attempting to take off from Munich-Riem Airport. Many of the 23 killed on the aircraft played for Manchester United Football Club. Investigators established that the aircraft had been slowed to such a degree by slush (known to pilots as “runway contamination”), that it failed to achieve take-off speed. Surprisingly, perhaps, lightning is not the threat that many passengers believe (or fear) it to be.


4. Sabotage

About 10 per cent of aircraft losses are caused by sabotage. As with lightning strikes, the risk posed by sabotage is much less than many people seem to believe.

Nevertheless, there have been numerous spectacular and shocking attacks by saboteurs. The September 1970 hijacking of three passenger jet aircraft to Dawsons Field in Jordan was a watershed moment in aviation history that prompted a review of security. Hijacked by devotees of the Popular Front for the Liberation of Palestine, the three aircraft were blown up in full view of the world’s press.

Despite improvements, malcontents still penetrate the security veil, as with the 2001 “shoe-bomber”, Richard Reid. Fortunately, Reid’s attempt to bring down an aircraft mid-flight proved unsuccessful.

5. Other forms of human error

The remaining losses are attributed to other types of human error, like mistakes made by air traffic controllers, dispatchers, loaders, fuellers or maintenance engineers. Sometimes required to work long shifts, maintenance engineers can make potentially catastrophic mistakes.

In 1990, a windscreen blowout on a British Airways flight nearly cost the life of the aircraft’s captain. According to the Air Accidents Investigation Branch, almost all of the windscreen’s 90 securing bolts “were of smaller than specified diameter”. Rather than attributing the mis-match between bolts and countersunk holes to his selection of the wrong-sized bolts, the maintenance engineer responsible for fitting the new windscreen blamed oversized countersinks. The engineer had not been sleeping well and did the windscreen replacement work during the period when his body clock wanted him to sleep – a time when reasoning and judgement easily falter.The Conversation

Simon Ashley Bennett is director of the Civil Safety & Security Unit (CSSU) at the University of Leicester.

This article was originally published on The Conversation. Read the original article.

 
 
 
 

Was the decline in Liverpool’s historic population really that unusual?

A view of Liverpool from Birkenhead. Image: Getty.

It is often reported that Liverpool’s population halved after the 1930s. But is this true? Or is it a myth?

Often, it’s simply assumed that it’s true. The end. Indeed, proud Londoner Lord Adonis – a leading proponent of the Liverpool-bypassing High Speed 2 railway, current chair of the National Infrastructure Commission, and generally a very influential person – stood on the stairs in Liverpool Town Hall in 2011 and said:

“The population of Liverpool has nearly halved in the last 50 years.”

This raises two questions. Firstly, did the population of the City of Liverpool really nearly halve in the 50 year period to 2011? That’s easy to check using this University of Portsmouth website – so I did just that (even though I knew he was wrong anyway). In 2011, the population of the City of Liverpool was 466,415. Fifty years earlier, in 1961, it was 737,637, which equates to a 37 per cent drop. Oops!

In fact, the City of Liverpool’s peak population was recorded in the 1931 Census as 846,302. Its lowest subsequent figure was recorded in the 2001 Census as 439,428 – which represents a 48 per cent decline from the peak population, over a 70 year period.

Compare this to the population figures for the similarly sized City of Manchester. Its peak population also recorded in the 1931 Census as 748,729, and its lowest subsequent figure was also recorded in the 2001 Census, as 392,830. This also represents a 48 per cent decline from the peak population, over the same 70 year period.

So, as can be seen here, Liverpool is not a special case at all. Which makes me wonder why it is often singled out or portrayed as exceptional in this regard, in the media and, indeed, by some badly briefed politicians. Even London has a similar story to tell, and it is told rather well in this recent article by a Londoner, for the Museum of London. (Editor’s note: It’s one of mine.)

This leads me onto the second question: where have all those people gone: London? The Moon? Mars?

Well, it turns out that the answer is bit boring and obvious actually: after World War 2, lots of people moved to the suburbs. You know: cars, commuter trains, slum clearance, the Blitz, all that stuff. In other words, Liverpool is just like many other places: after the war, this country experienced a depopulation bonanza.


So what form did this movement to the suburbs take, as far as Liverpool was concerned? Well, people moved and were moved to the suburbs of Greater Liverpool, in what are now the outer boroughs of the city region: Halton, Knowsley, St Helens, Sefton, Wirral. Others moved further, to Cheshire West & Chester, West Lancashire, Warrington, even nearby North Wales, as previously discussed here.

In common with many cities, indeed, Liverpool City Council actually built and owned large several ‘New Town’ council estates, to which they moved tens of thousands of people to from Liverpool’s inner districts: Winsford in Cheshire West (where comedian John Bishop grew up), Runcorn in Halton (where comedian John Bishop also grew up), Skelmersdale in West Lancashire, Kirkby in Knowsley. There is nothing unique or sinister here about Liverpool (apart from comedian John Bishop). This was common practice across the country – Indeed, it was central government policy – and resulted in about 160,000 people being ‘removed’ from the Liverpool local authority area.

Many other people also moved to the nearby suburbs of Greater Liverpool to private housing – another trend reflected across the country. It’s worth acknowledging, however, that cities across the world are subject to a level of ‘churn’ in population, whereby many people move out and many people move in, over time, too.

So how did those prominent images of derelict streets in the inner-city part of the City of Liverpool local authority area come about? For that, you have to blame the last Labour government’s over-zealous ‘Housing Market Renewal Initiative’ (HMRI) disaster – and the over enthusiastic participation of the then-Lib Dem controlled city council. On the promise of ‘free’ money from central government, the latter removed hundreds of people from their homes with a view to demolishing the Victorian terraces, and building new replacements. Many of these houses, in truth, were already fully modernised, owner-occupied houses within viable and longstanding communities, as can be seen here in Voelas Street, one of the famous Welsh Streets of Liverpool:

Voelas Street before HMRI implementation. Image: WelshStreets.co.uk.

The same picture after HMRI implementation Image: WelshStreets.co.uk. 

Nonetheless: the council bought the houses and ‘tinned them up’ ready for demolition. Then the coalition Conservative/Lib Dem government, elected in 2010, pulled the plug on the scheme. 

Fast forward to 2017 and many of the condemned houses have been renovated, in a process which is still ongoing. These are over-subscribed when they come to market, suggesting that the idea was never appropriate for Liverpool on that scale. 

At any rate, it turns out that the Liverpool metropolitan population is pretty much the same as it was at its peak in 1931 (depending where the local borough boundaries are arbitrarily drawn). It just begs the question: why are well educated and supposedly clever people misrepresenting the Liverpool metropolis, in particular, in this way so often? Surely they aren’t stupid are they?


And why are some people so determined to always isolate the City of Liverpool from its hinterland, while London is always described in terms of its whole urban area? It just confuses and undermines what would otherwise often be worthwhile comparisons and discussions. Or, to put it another way: “never, ever, compare apples with larger urban zones”.

In a recent Channel 4 documentary, for example, the well-known and respected journalist Michael Burke directly compared the forecast population growths, by 2039, of the City of Liverpool single local authority area against that of the combined 33 local authority areas of Greater London: 42,722 versus 2.187,708. I mean, what bizarre point is such an inappropriate comparison even trying to make? It is like comparing the projected growth of a normal sized-person’s head with the projected growth of the whole of an obese person, over a protracted period.

Having said all that, there is an important sensible conversation to be had as to why the populations of the Greater Liverpool metropolis and others haven’t grown as fast as maybe should have been the case, whilst, in recent times, the Greater London population has been burgeoning. But constantly pitching it as some sort of rare local apocalypse helps no one.

Dave Mail has declared himself CityMetric’s Liverpool City Region correspondent. He will be updating us on the brave new world of Liverpool City Region, mostly monthly, in ‘E-mail from Liverpool City Region’ and he is on twitter @davemail2017.