Delta Air Lines is nearing the completion of a multi-year program to replace auxiliary power units (APUs) on more than 300 of its Airbus A320 family aircraft. The initiative addresses concerns over potential cabin air contamination from toxic fumes, a long-standing issue in the aviation industry.
Key Takeaways
- Delta is replacing auxiliary power units on its Airbus A320 fleet to prevent toxic fumes in the cabin.
- The replacement program, which began in 2022, is approximately 90% complete.
- These "fume events" are typically caused by oil leaking into the aircraft's air supply system.
- Airbus plans a design change for new aircraft starting next year, but this will not affect existing fleets.
Delta's Proactive Fleet Upgrade
Delta Air Lines has confirmed it is in the final stages of a major hardware replacement across its fleet of 310 Airbus A320 family aircraft. The airline initiated the program in 2022 to replace the auxiliary power units on these jets.
An airline spokesperson stated that the replacement effort is now about 90% complete. This action follows reports and industry analysis identifying APUs as a potential source of contaminated cabin air, commonly referred to as "fume events."
What is an Auxiliary Power Unit?
An auxiliary power unit (APU) is a small turbine engine located in the tail of an aircraft. It provides electrical power and conditioned air for the cabin while the main engines are not running, such as when the plane is at the gate. It can also serve as a backup for pneumatic and electrical systems in flight.
The Cause of Contaminated Cabin Air
The issue of contaminated air arises from the way aircraft source breathable air for the cabin. Most modern jets use a "bleed air" system, which draws compressed air from the engines or the APU. This air is then cooled and circulated throughout the cabin and cockpit.
A fume event occurs when oil or hydraulic fluid leaks into this system. The high temperatures within the engine or APU can cause these fluids to vaporize, releasing potentially harmful chemicals and neurotoxins into the air supply. Passengers and crew may notice unusual odors during these events.
According to aviation safety experts, fume events have been linked to a range of health issues for passengers and flight crews, including respiratory problems, neurological symptoms, and, in some reported cases, brain injuries and long-term illness.
A Persistent Industry Challenge
While Delta's replacement program is a recent development, the underlying problem is not new. Keith Mackey, a retired airline captain and aviation accident consultant, noted that concerns over toxic fumes have been present for approximately two decades.
"The toxic fumes are apparently coming from an oil leak or external leak in the auxiliary power unit," Mackey explained. "This isn’t used to power the airplane in flight, but it is used to supply air conditioning or heating on the ground or in flight if needed."
Mackey suggested that the scale of the problem is only recently being fully understood. "It’s becoming evident that there have been more cases of crew and passengers complaining of odors or effects from it; some people have actually been hospitalized because of it, and there’ve been a couple of lawsuits filed," he added.
Airbus Identifies Source and Plans Future Fix
Aircraft manufacturer Airbus has previously acknowledged the issue, identifying the APU and its integration as a primary source of fume events on the A320 family. Investigations found that many incidents were linked to oil leaks entering the APU's air inlet, which is located on the underside of the aircraft fuselage.
To mitigate this risk in the future, Airbus announced a significant design change. For new aircraft built from 2026 onward, the air intake for the APU will be relocated to the top of the fuselage. This change is intended to reduce the likelihood of ground-based fluids being drawn into the system.
Limitations of the New Design
The planned design modification by Airbus will only apply to newly manufactured aircraft. It does not provide a solution for the thousands of A320 family jets currently in service with airlines worldwide. This leaves individual carriers like Delta to manage the risk on their existing fleets through maintenance and component replacement programs.
Another potential cause of fume events is oil leakage within the main jet engines, which supply the majority of bleed air during flight. While replacing APUs can reduce the risk of incidents, especially during ground operations, it does not completely eliminate all potential sources of air contamination.
Delta's decision to replace the units on over 300 aircraft represents a significant investment in addressing cabin air quality and enhancing the safety and well-being of its passengers and crew members.
