I was helping one of our engineers work underneath the helicopter the other day and the amount of structure and different types of materials used to build it were incredible. It got me thinking about what actually makes up certain parts of the helicopter, so I got the training manuals out, spoke to our helicopter sales reps and this is what I found out!
Helicopters are made from an array of alloys, composites, laminates, resins, and plastics all designed to give incredible strength, stiffness, flexibility & durability while keeping the helicopter as light as possible. Aluminum, Kevlar, carbon & glass-fiber composites are the most common materials.
Surely it must be easier to just build the whole helicopter out of a material like carbon fiber or aluminum, so why don’t the engineers and designers do that? Read on to find out…
Materials Used in a Helicopter
A helicopter is a marvelous piece of engineering and even when I’m flying around it still amazes me to this day at what these machines can do, but without careful consideration, research, design and testing, my helicopter would never get off the ground.
Each part in a helicopter has a specific job to do but it has to be safe, lightweight and last a long time. Many of the components on a helicopter are limited by either an hour life or time life.
- The main rotor blades on a Robinson R22 have a service life of 2200 hours of use or 12 years.
- If the helicopter was bought, placed in a hanger, and never flown, after 12 years the blades would be scrap, or
- After flying the helicopter for 2200 hours the blades would be scrap.
The main reason for this is the materials used to manufacture the blades have been given a life limit by the manufacturer to ensure they remain safe. The blades could run fine until 4000 hours but the manufacturer has limited them with a large margin of safety.
Each part of a helicopter may have very different stress loads imparted on it that it needs to stand up to and resist while in use on the helicopter. Some materials are very strong when twisted, whereas some may be stronger in rigidity for example.
Each component has a careful materials selection process done to it during the design phase to match the best material for the job all while keeping the weight and cost to a minimum.
Here are some of the main materials used in the Astar shown above:
This is a very strong, lightweight, and impact-resistant polycarbonate. It is like a flexible glass that can be easily shaped. It is used for the ceiling windows.
Most of you will know this as the brand name Plexiglass. This European variant is used for the windows. Its UV protection, impact-resistance and durability make this a great material to allow the occupants excellent visibility while keeping the weight down.
The main structure of most helicopters is comprised of an aluminum-based alloy. When shaped, folded and riveted together this creates an incredibly strong yet lightweight structure on which the rest of the helicopter can be built on.
Used with various coatings to prevent corrosion and blended metals, each helicopter manufacturer will select their own preference material to design the main structure.
These are materials that become pliable when heated and form a solid when cooled. Many of the external body panels are constructed using thermoplastic materials.
These materials give good strength and are easily formed, but they will break and crack if impacted or bent!
Laminates are a blend or sandwich of materials that are then bonded together to form a solid, strong but very light material. Many of the lower body panels are made of laminates like fiber-glass with honeycomb. Just like the Thermoplastics they can be easily dented or broken if too much pressure is applied.
Trust me I have made a hole in a belly panel once while moving an Astar with a Tow Cart! It cost me some beer to the engineer for that repair!
We all know steel is incredibly strong, but we also know it’s heavy as hell! Making a whole helicopter out of steel would mean it would become a paperweight. The skid tubes are the only part made of steel on this helicopter.
The skid tubes need to take the entire weight of the helicopter and not deform. This becomes apparent when landing out in the bush on undulating ground with rocks, logs, and dirt humps.
By allowing just a small part to be made of steel the landing gear will never bend under normal use allowing the helicopter to be able to land safely, every time.
This part of the helicopter is called the Firewall and it creates the engine compartment. A lightweight, corrosion, and fire-resistant material were needed here in case of a fuel leak and engine fire.
The stainless steel keeps the fire contained to allow enough time for the pilot to get the helicopter on the ground before the immense heat can deform parts around it like the tail boom attachment area.
There are many materials used to construct honeycomb but the main reason for the name is because it the shape. Aluminum, glass-fiber, carbon fiber are all common materials used in honeycomb.
They can be shaped and formed to provide incredible strength and support while being super light. Many structural panels are made from honeycomb on helicopters.
Why Not Use All The Same Material?
The larger and more sophisticated a helicopter becomes, the material selection gets ever more important. Lifting a helicopter into a hover requires immense power to generate enough lift to overcome the weight. The heavier the helicopter, the bigger the engine/s which requires a stronger fuselage.
For instance, the Leonardo AW139 begins to use much more expensive materials like Kevlar, Carbon and Titanium in its construction. This is one of the reasons why a new Astar costs around $3M while the AW139 is around $15M!
Yes, the AW139 is a much larger, twin-engine, IFR helicopter, but it needs these more expensive materials to do the job the designers gave them. If a cheaper alternative was available to give the same material performance you know it would be used!
“What about making the entire helicopter out of carbon fiber?” To a certain extent this would work and there are some helicopters coming onto the market where it is their main material. The SH09 from Kopter is a great example of this, but there are still many other materials used on it where carbon fiber is just not the best material.
The firewall I mentioned earlier is a great example. Jet fuels burns incredibly hot and a resin can soon melt under extreme heat. Having a helicopter fall apart around you from a fire is not a great selling feature!
Sometimes components need to be flexible to increase crash survivability, for example. The new fuel tank for the AS350/H125 Astar is a prime example of this. The old fuel tank was a molded plastic tank that would split upon impact releasing its fuel and causing horrendous fatal post crash fires.
The new crash resistant fuel tank is a bladder style tank that allows for deformation to absorb the impact and prevent rupture. A tank made of carbon fiber would not allow for this.
Materials are chosen because of their properties to make that particular part on a helicopter perform the best. Manufacturing, cost and durability are all high up on the designers need list when designing that component.
I take great comfort knowing that when I’m up flying every part on the helicopter has been designed to do a single job and do it well, although the pilot seats always seem to be an after thought!
If you found this helpful and interesting and are wondering what the main rotor blades of helicopter are made out of please check out my other article: