Smaller regional jets have lower maximum operating temperatures than full size jets
Tue 18 July 2017 – Rising temperatures as a result of global climate change will make it harder over the coming decades for aircraft to take off at certain airports, finds a Columbia University study published in the journal Climatic Change. Since 1980, average global temperatures have gone up nearly 1 degree C and this may already be having an effect. Last month, American Airlines cancelled over 40 flights out of Phoenix when daytime temperatures reached nearly 120ᵒ F (49ᵒ C) as smaller regional aircraft are only tested up to 118ᵒ F. As air warms, it spreads out and its density declines, and in thinner air, wings generate less lift as a plane races along a runway, explain the researchers. A packed plane may therefore be unable to take off safely so weight must either be dumped or the flight delayed or cancelled.
Average temperatures worldwide are expected to go up by as much as another 3 degrees C by 2100 and heatwaves, which can produce the most problems, will probably become more prevalent with annual maximum temperatures at airports projected to rise by between 4 and 8 degrees C, says the study.
Building on an earlier paper in 2015, the researchers looked at the effects of projected increases in global temperatures at 19 airports worldwide and used five common passenger aircraft models. Some aircraft with lower temperature tolerances will fare worse than others, they found, and certain airports – those with shorter runways, in hotter parts of the world or at higher elevations – are likely to suffer disrupted operations.
“This points to the unexplored risks of changing climate on aviation,” said co-author Radley Horton, a climatologist at Columbia University’s Lamont-Doherty Earth Observatory. “As the world gets more connected and aviation grows, there may be substantial potential for cascading effects, economic and otherwise.”
Depending on the level of global action taken to reduce emissions and limit the temperature increase, by the middle to late century aircraft fuel capacities and payload weights will have to be reduced by between 0.5 and 4 per cent, predict the researchers. Yet even a small change in the total aircraft fuel and payload weight represents a large decrease in capacity when aggregated across an airline’s fleet, they say. For example, a 0.5% decrease from maximum take-off weight (MTOW) for a Boeing 737-800 equates to about 722 lb (327.5kg), or three passengers. A 4% weight reduction would mean 12 or 13 fewer passengers on an average 160-seat aircraft.
While the projected change in weight restriction is relatively consistent across aircraft, the total impact of restriction varies, with the larger Boeing 777-300 and 787-8 potentially experiencing the greatest impacts from restriction. For an aircraft departing near MTOW, by mid- to late-century, total fuel and payload capacity may be reduced by 3-5%, with 30-40% of flights experiencing some restriction.
The smaller Airbus A320 and Boeing 737-800 are less impacted, so when departing near MTOW, approximately 5-10% of flights may experience some restriction, on average sacrificing 0.5% of their fuel and payload capacity. This, says the study, is due in part to aircraft design characteristics as well as most of the world’s commercial airports have far longer runways than are required, even at high temperatures. The A380 is also less likely to experience weight restrictions except at extremely high temperatures due to its exclusive operation at large airports.
Airports will face varying impacts with, for example, New York LaGuardia vulnerable due to its short runways and Dubai because of its already high temperatures despite long runways. Those in temperate regions – such as London Heathrow and Paris CDG – will be less affected.
For an industry operating on thin margins, losing passengers or cargo due to weight restrictions could be significant and the major logistical and economic effects of delays or cancellations can instantly ripple from one airport hub to another, pointed out Horton.
Some effects could be mitigated with new engine or body designs, or lengthened runways, he said, but modifications would come at a cost as aircraft are already highly engineered for efficiency and expanded runways are often not an option in built-up cities due to the expense and political opposition.
“Our results suggest that weight restriction may impose a non-trivial cost on airlines and impact aviation operations around the world,” said lead author of the study Ethan Coffel. “The sooner climate can be incorporated into mid- and long-range plans, the more effective adaptation efforts can be.”
While there has been considerable research on the impact of aviation on climate change, until relatively recently little has been done on the effects of climate change on the sector itself and presents fertile ground for future research, said the authors.
With weather a leading cause of disruption to flight operations, studies have now been published over the past few years that have looked at the effects of a changing climate on transatlantic air traffic routes as a result of a strengthening jet stream (see article), the probability of more clear air turbulence events affecting aircraft and passengers (see article), the impact on airports of extreme precipitation events and rising sea levels threatening low-lying coastal airports (see article).
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