The Helicopter: A Fragile Fish

Helicopters do not have a lot going for them.  They are expensive to buy as well as operate, somewhat odd-looking, and, if movies like Die Hard 3 and Cliffhanger are reliable sources of information, they can be brought down with a hand gun or a rock or some rope... pretty much anything nearby.

Helicopters are fairly vulnerable pieces of hardware, but it takes more than a knock in the rotor to drop them out of the sky.

I have traveled by planes, trains and automobiles, but never by helicopter.  From an engineering standpoint, they scare me.  Where possible, it is good to avoid single-point-failure scenarios.  If one airplane engine were to fail, most airplanes can still be flown with the remaining engines.  If the main rotor blade of a helicopter were to fail mid-flight, down it goes.  The main rotor is responsible for the lift force, and without it, it is time to look for a good parachute (and then a good lawyer).

How does a helicopter navigate around?  The principal force is generated by the main rotor, which spins very quickly, displacing vast amounts of air in exchange for lift upwards.  If it wants to maintain altitude, the lift force upwards must be equal to the weight downwards. 

What is Aerospace?

To kick off “Aerospace Month” on the Engineer’s Pulse, let us first examine what the term aerospace refers to.  As the word indicates, aerospace studies the motion of objects through both air (in the Earth’s atmosphere) and space (outside the Earth’s atmosphere). 

The field of study can therefore be broken down into two principal areas: aeronautical (within the atmosphere) and astronautical (within space).  Examples of aeronautical navigation include aircrafts (aviation), helicopters, and even hot-air balloons.  Astronautical navigation is limited to spacecrafts and satellites.

There is no real line in the sand, where the atmosphere becomes space; there is just a very gradual transition between the two extreme states.  Near the surface of the Earth, the medium known as air is a reasonably dense gas, with roughly 1 atm of pressure (101.3 kPa); this figure depicts how tight the molecules of the matter are packed together.  In space, at about 300 km altitude, we begin to see the other extreme, where molecules like Oxygen may travel a kilometre before colliding with another molecule.