Could someone explain construction and working of helicopter blades.?

Question

In the 1960's, quite a while back I know, but I was working on helicopters. Just like to know the difference and some technology involved in the new blades. Some of the older one were made of wood, some aluminum honeycomb, and others were just aluminum skin, nothing inside for support.

Thank Cotton

Answer 1

Frank Piaseki used steel tubing, spruce wood, birch plywood and fabric to construct the rotor blades of his PV-2. Today, almost all military and civilian rotor blades are made from polymer composites. Blades are designed with specific geometry that adapts them to the varying conditions of flight. Cross-section shapes of most rotor blades are not the same throughout the span. Shapes are varied along the blade radius to take advantage of the particular airspeed range experienced at each point on the blade, and to help balance the load between the root and tip. The blade may be built with a twist, so an airfoil section near the root has a larger pitch angle than a section near the tip. Without polymer composites, the complex airfoils of today's rotorcraft would likely not be possible.

Answer 2

Blade materials varies widely.

The MH-53J Blades are made using a Titanium D cord which is hollow and wrapped with composites to give it the proper shape. They then have the leading edges coated with Blade tape with is a double coating of thick rubber tape which helps prevent wear and tear on the edge. Once the blade is mounted on the Helo it is pressurized with Nitrogen. The blade contains a IBIS (In-Flight Blade Inspection System). If this pressure drops the system releases a SMALL quantity of a radioactive substance that is picked up by a detector in the top of the Helo. This lets the pilots know if there is damage to the blades.

Usually they are mounted to the hubs using Steel Bolts and A LOT of safety wire, just so they don't come loose. ^_^

I do know that the Army's canceled Comanche Helo used an ALL composite blade.

Answer 3

There is still a wide variety of structures, airfoils and materials. Some of the early blades were even made of balsa wood with a metal skin. Modern blades are made of 7075 aluminum (or titanium) including the internal I-beam and ribs construction. They get their real strength from centrifugal force. If you use a crane and try to lift a helicopter by the blades they cannot support the weight and will fold up yet they will easily support the craft if they are spinning.