Twin engine helicopter safety: what two engines really mean

Key points

• A twin-engine helicopter is designed to keep flying safely if one engine stops, within certified limits, which widens the pilot's choices.
• That matters most over built-up areas, over water and in poor light, which is why the rules for some operations favour twins.
• An Air Operator's Certificate (AOC) is the CAA approval a company needs to carry passengers for payment. It covers procedures, crew training, maintenance and safety management.
• Two engines reduce one kind of risk. They do not replace good decisions, weather minima or a well-trained crew.
• Our whole fleet is twin-engine, flown under a UK CAA Air Operator's Certificate and fully insured.

What does twin-engine actually mean?

Twin engine helicopter safety starts with the design. A twin-engine helicopter has two turbine engines driving the same rotor system. If one fails, the other can usually carry the aircraft to a safe landing, or, in many conditions, to continue flight, depending on weight, altitude and temperature. Certification sets out exactly what the aircraft must be able to do.

A single-engine helicopter has one, so an engine failure leads to a controlled descent, known as an autorotation, where the rotor keeps turning and the pilot lands at a suitable spot. Pilots train for it extensively and it works, but it needs a suitable place to land. Over a dense city or open water, a place may not exist. Our article on choosing the right helicopter explains how this affects the choice.

Where does having two engines matter most?

Two engines matter most when the choices below the aircraft are limited. That means flying over congested areas, over water such as the Channel or the Solent, and in poor light. It also gives more performance margin when taking off from small or confined sites, when the helicopter is heavily loaded, or on hot days when engines produce less power.

It is the reason that many corporate and protection teams only fly twins. For a team moving a principal, see moving people securely by helicopter. The Battersea Helicopter site also compares them in its guide to twin-engine versus single-engine helicopters.

Protection teams planning a move can use our close protection helicopter planning checklist alongside this guide.

What does two engines not do?

Two engines are not a guarantee, and nobody should present them as one. A twin still depends on a trained pilot, a maintained aircraft and the right weather. A heavy load on a hot day can reduce the single-engine margin. A fault that is not an engine fault, for example a problem with the controls, is still a problem.

This is why safety is built in layers: the aircraft, the crew, the company procedures and the regulator. Engines are one layer. We say so plainly because overselling a feature does nobody any good.

What is an Air Operator's Certificate?

An Air Operator's Certificate (AOC) is the approval a company must hold from the Civil Aviation Authority (CAA) to carry passengers for payment in the UK. The CAA only grants one when the company can show that it meets the requirements, and then supervises it. The CAA publishes a guide to the different certificates on its air operator certificates page.

In practice an AOC means the company has approved procedures for flight planning and weather, a training programme for its crew, an approved maintenance system, a safety management system and the insurance and financial standing the rules demand. Flights are not just permitted, they are audited.

Charter-A Helicopter is the helicopter charter service of Charter-A Ltd, which has arranged private flights across the UK and Europe since 2011. We use helicopters on a UK CAA or EASA approved AOC only. For the wider rule book, see our guide to helicopter safety and regulation in the UK.

Who is flying, and how are they trained?

Commercial pilots hold a licence and a type rating for the helicopter they fly, plus regular proficiency checks and training under the company's AOC. Those checks cover normal and emergency handling, including engine failures in flight. Pilots must also operate within published limits for flying hours and rest.

You do not need to check any of this yourself: it is the reason we only use approved companies. But you can ask us at any time what applies to your flight, and we will answer plainly.

How do the aircraft in our fleet compare on engines?

Every helicopter we use has two engines. The Leonardo AW139 and the Airbus H145 D3 each seat eight passengers, the Agusta 109 Grand seats six and the AS355 Twin Squirrel seats five, with the Sikorsky S-76 available as another twin option. The choice between them is about seats, luggage and range, not about whether the aircraft has a second engine.

If you are weighing the cost of a twin against something smaller, remember that the extra engine is what allows operations over cities and water and what supports heavier loads. We would not advise a single-engine helicopter for a journey that crosses a large city or a stretch of sea.

What should I ask about safety before booking?

• Is the helicopter twin-engine, and is it on a UK CAA or EASA approved AOC?
• Is it fully insured for passenger carriage?
• Are the pilots type-rated for the aircraft?
• What are the weather limits, and what happens if conditions are marginal?
• What is the alternative if the flight cannot go?

We answer each of these for every booking. See also the fleet page for the aircraft and request a quote for your journey.