Rising Temperatures: Aircraft Payload and Range Affects

This is the first part of a three part article series on the impacts of rising temperatures due to climate change.

When temperatures soar to exceptionally warm levels, such as the 109 deg F in Paris in July 2019,  not only is the utilization and efficiency of aircraft negatively affected, but aviation’s infrastructure suffers as well.  

For a given runway length, airport elevation, and aircraft type, there is a temperature threshold above which the airplane cannot take off at its maximum weight and thus must be weight restricted.  Ethan Coffel, then a doctoral student and Professor Radley M Horton of the Department of Earth and Environmental Sciences at Columbia University, conducted an analysis of “weight penalties” due to projected rising temperatures in the 2050-70 timeframe using the Boeing 737-800 as its baseline aircraft. They examined the weight penalties that would be inflicted on takeoff from Phoenix (PHX), Denver (DEN), New York LaGuardia (LGA) and Washington Reagan National (DCA) airports. 

PHX was chosen because of its frequent extremely high summer temperatures. DEN is a natural choice when considering high-density altitude airports for commercial air traffic. LGA and DCA were included in the analysis because of their short runways, limited space for expansion and high traffic loads. At LGA and DCA, a 737-800 cannot take off at its maximum weight at any temperature because of the relatively short runways. At DEN the runways are sufficiently long, but the required takeoff speed would exceed the maximum tire speed of 225 mph.

The maximum takeoff weight of a 737-800 is 174,200 lb. The average empty weight (no payload or fuel) is 91,300 lbs., leaving 82,900 lbs. available for both fuel and payload of passengers and cargo. The number of weight-restriction days caused by excessive temperatures increases significantly at each airport with the number of 10,000-lb. restriction days (10,000 lbs. being the equivalent of 52 pax) going from near zero to approximately 20 at PHX and doubling at LGA. Large increases in the number of 15,000-lb. restriction days (equivalent of 79 passengers, or approximately 30% of the payload capacity of the aircraft ) are seen at DEN, LGA and DCA. 

Aircraft payload and range will be substantially affected, and these performance reductions will have a negative economic effect on the air transport industry. 

As if the loss of revenue from carrying far fewer passengers on heat-restricted days isn’t bad enough, there will be other substantial costs to the aviation transport industry. Engine temperature thresholds used in this study assumed that maximum takeoff power is used, as opposed to reduced thrust takeoffs. The primary advantage to a reduced thrust takeoff is cost savings through increased engine life and reduced overhaul costs. The loss of these benefits from reduced thrust takeoffs will impose an additional (and sizable) cost burden onto aircraft operators.

A further cost factor caused by operations at hotter temperatures and higher takeoff speeds is the stress to tires. Tire are designed to withstand a wide range of operating conditions.  However, a combination of heat and high speed increases the possibility of tread loss.  The centrifugal forces on the outside circumference of the tire are directly proportional to the velocity multiplied by itself (“squared”).  For example, the centrifugal force on a 30-in. tire at 100 mph is 500 Gs, but when travelling twice that speed at 200 mph the force increases to 2,000 Gs.  Takeoffs attempted in thinner air caused by hotter temperatures will require higher rotation speeds, thus placing considerable additional stress on tires. Conditions which contribute to the stress on the tires include takeoffs at close to tire-speed-limit weight, quick turn-arounds, hot and long taxi distances, high-density altitude, slower-than-normal rotation rate, late rotation, or a tailwind. The consequences are likely to be an increased probability of high-speed tire failures and increased maintenance costs for earlier-than-predicted tire replacement. 

Air carriers may need to allocate summertime cross-country flights to aircraft with better takeoff performance. Heavily loaded flights may need to be rescheduled away from the hottest parts of the day.  

Flight operations from business aviation’s glamorous mountain destinations such as Aspen will experience similar impacts. Larger corporate flight departments with multiple aircraft may need to adopt the same tactic, but single-aircraft owners will primarily endure the effect of needing to reschedule flights during cooler parts of the day, thus impacting the flexibility and time optimization features of business aircraft. Unsympathetic bosses will not be happy to have their afternoon departures curtailed and/or the addition of a fuel stop in order to meet the necessary runway and climb performance requirements.  

Could airports extend existing runways or build new, longer runways? At urban airports like LGA and DCA, runway extension is unlikely, leading to more constrained summertime operations. 

Another tactic for operators would be to shift longer flights to nearby airports with longer runways, such as New York John F. Kennedy International (JFK) or Newark Liberty International (EWR) airports, and Washington Dulles International (IAD) in Virginia. However, such decisions would require advanced planning, especially since these airports operate at near 100% capacity today. Options for shifting business aviation flights from Westchester Airport (HPN) and Teterboro (TEB) to airports with longer runways will impact ground transport time for Manhattan clients.  

This is not the only study warning the industry of the weight penalties that will soon cause significant impacts. The Colorado Climate Change Vulnerability Study analyzed the weight penalties for aircraft in this notoriously “hot and high” environment. Even though DEN has the world’s longest public runway, the study projects that summer cargo losses as high as 19% will be encountered by 2030 due to increased temperatures.   

A separate analysis by the National Oceanic and Atmospheric Administration of the DEN and PHX airports estimated a summer (June through August) cargo loss for a single Boeing 747 of 17% and 9%, respectively, by 2030 because of the effects of increased temperature.  (Thomas R. Karl and David M. Anderson, Emerging Issues in Abrupt Climate Change, March 12, 2007)

The next part of this article series will explore climate change effects on infrastructure.