Why do some aircraft need to be started in the air?

In the aviation sector, the reliability and efficiency of aircraft engines are of vital importance. However, there are situations where an aircraft requires an air start device (commonly called an air start) to start the engine. Understanding why some aircraft require mid-air starts requires a deeper look into the mechanics of aircraft engines, the role of onboard batteries, and the various situations in which this auxiliary support might be needed.

An air starter is a portable device used to provide the power needed to start an aircraft engine when the onboard batteries are low. This can happen for a variety of reasons, including adverse weather conditions, battery failure, or even the peculiar design of the aircraft itself. Essentially, an air start is a backup system that ensures the aircraft can still operate normally if the primary system fails.

One of the main reasons aircraft need to be air-started is the limitations of onboard batteries. While modern aircraft batteries are designed to be rugged and reliable, they can sometimes fail under extreme conditions. For example, in extremely cold weather, battery performance can degrade significantly, making it difficult to generate enough electricity to start the engine. In this case, the air start device can provide the necessary boost to start the engine, ensuring that the aircraft can take off as planned.

Additionally, certain aircraft designs may inherently require an air start due to their engine configuration. For example, some military jets and large commercial aircraft use engines that require higher initial power output to start the combustion process. In these cases, relying solely on the onboard battery may not be enough, and air starts become essential. This is especially true for aircraft operating in environments such as military operations or busy commercial airports where fast turnaround times are critical.

Another factor that may cause the need for an air start is a battery problem. Batteries, like any other component, can fail or degrade over time. If an aircraft’s batteries are insufficiently charged or malfunction, they may not be able to provide the power needed to start the engines. In this case, ground crews can use an air starter to bypass the battery problem and ensure the aircraft is ready to fly.

Air starts are used for more than just starting engines; they also play a vital role in maintaining operational efficiency. For example, during pre-flight checks, if an aircraft’s systems are not functioning properly due to low battery, an air starter can help troubleshoot and resolve those issues before takeoff. This capability is critical to ensuring the safety and reliability of aviation operations.