What could have caused the Air India crash? An expert examines the proposed failure scenarios

The recent crash of an Air India Boeing 787 Dreamliner in Ahmedabad has prompted widespread discussion about potential causes. As an expert with a background in aircraft design, I would not attempt to speculate on the cause of the incident. We should wait for the crash investigators to carry out a rigorous analysis.

Instead, I will explain the various flight scenarios currently being discussed in the public domain, and explore what each of them implies from the perspective of aircraft design and performance.

Understanding how such factors interact with aircraft systems and flight performance can shed light on how modern aircraft are designed to handle rare but critical situations.

Loss of engine thrust

Modern commercial aircraft are designed to safely continue takeoff and climb with one engine not operating. This is a fundamental certification requirement, particularly for twin-engine aircraft. It ensures that the loss of a single engine, even during the critical takeoff phase, should not result in a catastrophic failure.

However, the loss of both engines is an extremely serious scenario.

A notable case of dual engine failure occurred in 2001 on Air Transat Flight 236, which was traveling from Toronto, Canada, to Lisbon in Portugal. The Airbus A330 aircraft lost both engines over the Atlantic Ocean due to a fuel leak, but managed to glide approximately 75 miles (120km) before safely landing at Lajes Air Base in the Azores. This was possible because the aircraft had sufficient altitude and airspeed at the time of its total engine failure.

However, takeoff and landing are considered the most critical phases of flight because the aircraft is close to the ground, giving pilots limited time and altitude to respond to failures. At low speed and altitude, the aircraft may also lack the necessary energy (in terms of both airspeed and height) to glide a meaningful distance.

Bird strikes can also cause engine failure, as seen in the case of US Airways Flight 1549, an Airbus A320 that struck a flock of birds shortly after take off from New York’s LaGuardia Airport on January 15, 2009. Both engines failed and, due to the aircraft’s low altitude and limited speed, the pilots determined that returning to the airport was not feasible.

Instead, pilot Chesley “Sully” Sullenberger and co-pilot Jeffrey Skiles executed a successful emergency water landing on the Hudson River, resulting in the survival of all onboard. As such, the incident became known as the “miracle on the Hudson.”

These examples highlight how altitude, speed and pilot decision-making, along with robust aircraft design, play a critical role in the outcome of rare but severe engine failure events.

Landing gear not retracted

During a normal takeoff procedure, the landing gear—the sets of wheels under a plane that support it on the ground—is retracted within seconds after liftoff, once the aircraft has safely left the ground.

Extended landing gear produces significant aerodynamic drag. So, during the initial climb when the aircraft requires maximum thrust to gain altitude, eliminating this drag by retracting the landing gear is highly beneficial for both climb performance and fuel efficiency.

However, commercial aircraft are designed to remain controllable and flyable even if the landing gear fails to retract. In such cases, the aircraft should still be able to perform a “go-around” before safely landing again, assuming no other critical failures have occurred.

That said, a scenario involving both loss of engine thrust and non-retracted landing gear can severely degrade glide performance. The additional drag from the extended gear reduces the aircraft’s lift-to-drag ratio, an indication of the aerodynamic efficiency of the airplane.

The extended landing gear might limit the distance it can glide and increase its descent rate—which is especially critical when altitude is limited.

Flaps retracted prematurely

An aircraft’s ability to generate lift depends on several factors, including wing area, airspeed, altitude, and the “lift coefficient”—a number that describes how effectively a wing or other surface generates lift under specific flight conditions. The lift coefficient is largely influenced by the wing’s geometry, particularly its curvature (called camber).

During takeoff and landing, the aircraft operates at relatively low speeds where the wings alone may not generate enough lift. To compensate, high-lift devices such as flaps are deployed. These devices are usually mounted on the wings’ trailing edges and, when extended, increase each wing’s curvature and surface area, thereby raising the lift coefficient and allowing the aircraft to remain airborne at lower speeds.

However, deploying flaps also increases aerodynamic drag. For this reason, once the aircraft accelerates and reaches a safe climb speed, the flaps are gradually retracted to reduce drag and improve fuel efficiency.

If the flaps are retracted too early, before the aircraft has reached sufficient speed, there can be a sudden loss of lift. This may result in a stall or insufficient climb performance.

This situation becomes even more critical if it occurs in combination with other issues, such as extended landing gear (which increases drag) or a loss of engine thrust, as the combined aerodynamic penalties may prevent the aircraft from maintaining controlled flight.

Conclusion

Over the years, numerous improvements in aircraft design, maintenance and operational procedures have resulted from crash investigations. Each incident, especially a fatal one such as the Air India Boeing 787 crash, offers valuable lessons that can drive further enhancements in aviation safety.

The fact that both the aircraft’s flight data recorder and cockpit voice recorder (sometimes referred to as the “black boxes”) have now been recovered offers hope that the precise cause of this crash will be identified.

Whatever is ultimately determined to be the cause—technical failure, human error, or a combination of both—there will be lessons to be learned. Every event highlights areas where systems, procedures or training can be strengthened to make aviation even safer in the future.

This article is republished from The Conversation under a Creative Commons license. Read the original article.