Most people think that helicopters can land anywhere. They imagine that the pilot can just find a small area and lower vertically on to it with no problems. Many people want to learn to fly helicopters for precisely this reason, and I once knew a student who hoped to buy a helicopter after he learned to fly and land it in his very small back garden. Though this is theoretically possible, it is really difficult.
The Difficulties of Landing in a Confined Area
To land a helicopter in a small confined area, you need to fly with precision, slowing down gradually and not overshooting the landing site. Helicopters can hover, but they cannot do it quickly. Slowing down a helicopter takes a long time, and though there is a helicopter maneuver called a ‘quickstop’, it is only a relatively quick stop; the maneuver actually takes quite some time and covers a lot of ground. So, landing in a small area is not for novice pilots.
The Problem of the ‘Vortex Ring’
The main issue with landing in a confined area is that you have to be very careful not to get into what is known as a ‘vortex ring state’. This is an uncontrolled descent in which the helicopter falls down into its own downwash, and usually crashes. A vortex ring can occur if three conditions are present: a very low airspeed, a high rate of descent, and applied power. These are all common conditions if you are trying to land a helicopter in a small area – you slow down until the aircraft is moving very slowly, you try to descend quickly, and you apply power to control your descent. If you do this, the helicopter can very easily lose control, which can cause an accident.
How do You Land in a Confined Area?
Because of the above issues, pilots land in confined areas slowly and carefully. The pilot flies around the landing spot, checking for obstacles and planning how to approach. There could be rough ground or other possible problems. He or she then approaches the landing site slowly and carefully, descending gradually. If at all possible, he makes this gradual approach all the way to the ground. However, if there are obstacles on the approach, he may need to stay high and come down vertically at the last minute. This vertical descent is the most dangerous part, as the helicopter has no airspeed and power will be applied; two of the conditions that create a vortex ring. So the pilot must ensure that he keeps the rate of descent low. This is why you see helicopters descending to landing sites, such as hotel helipads, very slowly – it ensures a safe landing.
Confined Area Landing: One of the Last Exercises
Confined area landings are one of the last exercises in the private pilot’s license course for helicopters. And some flying schools, including the one where I learned to fly, will not allow newly qualified pilots to land in a confined area unless they do it with an instructor first – as all confined areas are different, and there may be additional problems to those I mentioned.
However, as with most things, confined area landings become easier with practice and experience. Eventually, the student I mentioned above was actually able to land a helicopter in his back garden, but it took a while.
Decoding Science. One article at a time.