Why Most Trijets are Out of Service: Cost, Efficiency, and Safety Considerations

Trijet aircraft, known for their three engines, have seen a decline in popularity and usage among airlines. While they were once a common sight, they are now mostly phased out in favor of two-engine and four-engine designs. This article explores the reasons behind the decline of trijet aircraft, focusing on cost, efficiency, and safety considerations.

Cost Considerations: Manufacturing and Maintenance

One of the primary reasons trijets are out of service is the increased cost of manufacturing and maintaining these aircraft. Trijet aircraft require more complex structures, additional weight due to the third engine, and specialized maintenance and training for technicians. These factors contribute to higher operational and maintenance costs. For many airlines, the financial burden of operating these aircraft is too high, especially when compared to the more modern and efficient twin-engine and four-engine designs.

Efficiency Considerations: Fuel Efficiency

Three-engine aircraft often suffer from lower fuel efficiency compared to their two-engine and four-engine counterparts. This inefficiency is primarily due to the added drag from the third engine, which can compromise the aerodynamic performance of the aircraft. As fuel prices continue to rise, airlines are increasingly seeking ways to reduce their operational costs, and fuel efficiency has become a critical factor. Twin-engine and four-engine aircraft can often outperform trijets in terms of fuel consumption, making them more attractive to operators looking to minimize their environmental impact and reduce costs.

Safety Considerations: Engine Failure Impact

The safety record of trijet aircraft is another factor that has contributed to their decline. In case of engine failure, trijet aircraft often face a greater challenge in maintaining control and handling. When one engine is lost, the performance and handling characteristics of trijets can be significantly affected, posing a greater risk to the safety of the aircraft and its passengers. In contrast, four-engine aircraft have the advantage of redundancy, which can help in managing such emergencies more effectively. The additional engine on a four-engine aircraft can provide a more stable and safer flight experience in the event of an engine failure.

Examples of Trijets in Service

While the production of trijet aircraft has largely ceased, there are still a few examples in active service. The Boeing 727 is the only trijet airliner still in operation in the United States, with the tail-mounted engines configuration. Outside of the United States, the Tupolev TU-154, operated by North Korea's Air Koryo, remains the only commercial aircraft with three engines still flying regular service. As of August 8, 2021, the TU-154 is the last significant trijet in service, highlighting the limitations and challenges faced by these aircraft in the modern aviation industry.

Conclusion

The phase-out of trijet aircraft is a result of a complex interplay of factors, including cost, efficiency, and safety considerations. While trijets once held a prominent place in the aviation industry, the operational and economic advantages of modern two-engine and four-engine designs have led to their widespread adoption. Although a few examples of trijets still exist, they are exceptions rather than the norm, reflecting the changing needs and priorities of the aviation sector in the modern era.