This week, I was able to get the chance to sit in a glider and experience a lot of maneuvers that I learnt throughout my aerospace degree. But it also astonished me how effortlessly these gliders could stay up in the air and even gain altitude, despite having an idea on how they work.
A Paper Weight
A standard glider weighs up to only about 600 kg with the more advanced ones weighing up to just 400 kg. This is around half to three times the weight of a Cesna 172 all fueled up. So what makes these aircraft so light?
Well as most of these gliders are becoming more modern, they include more use of glass fibre reinforced plastic (GFRP). GFRP is a composite material, like carbon fibre, that has a great strength to weight ratio. It allows these aircraft to be much lighter whilst experiencing the same loads as other aircraft materials like aluminium, steel or even plywood.
High Aspect Ratio
The aspect ratio of an aircraft is the measure of the wings width to its length and is a determines its lift and maneuverability capabilities. Fighter jets will have a lower aspect ratio so they can maneuver quicker, whereas higher aspect ratio wings will be better for long range endurance flights, typically used by civil transport aircraft as well as gliders. The aspect ratio of a glider is typically around 6, which paired with its high aerodynamic efficiency and low weight means that they have a great glide ratio.
The glide ratio is how far an aircraft can travel before loosing a unit of altitude. Here the glide ratios of gliders are typically around 25 and can go up to 60 for high performance gliders which means if at a height of 3000 ft, a glider can travel 75000 ft or around 23km. Now, you might think that these gliders don’t travel fast, and compared to a general powered aircraft, they are slow, but they are comparable to cars. At cruising speeds they can travel up to 110 km/h and the maximum allowable speed is around 290 km/h. This means that they can go cross country faster than cars because they don’t have to account for twisting roads.
Now, despite these parameters, gliders are still unpowered, and will eventually come down. Even though the gliders descend for almost the entirety of its flight, gliders can also go up for extensive periods of time.
Thermalling and Soaring
Gliders are capable of gaining altitude without the power of a motor by two ways, thermalling and soaring. Thermalling capitalises on convection currents created by thermal sources from the ground usually generated by reflected solar energy. This column of rising air, usually occurs on darker shades like plowed fields and asphalt making cities and countryside ideal. Inspired by birds, this is a very efficient way for gliders to increase their altitude and with one even increasing its altitude by 25,000 ft1.
Soaring happens due to the wind movement when deflected upwards from a mountain or hill.
Due to these parameters gliders can traverse hundreds of kilometers and stay up in the air for several hours. The world record for the longest glider flight is 70 hours and the furthest one has travelled 3008km2, and no, there isn’t a toilet onboard. But how do they get off the ground to start off with?
Lift Off
There are three ways that gliders can get off the ground. The least used is a motor that extends out of the main body which allows the glider to take off and reach a certain altitude before stowing it away again. The following one is by winching the glider. Here a winch is attached to the glider and rapidly accelerates it giving it enough speed to take off and reach up to 2000 ft which is frequently used as training for take off and landing.
As commonly used, but more effective for long distance flight is by towing. Here a rope gets attached to a plane where is gets towed to a certain altitude and then gets released.
With the technological advancements gliding will only become better and maybe one day we will see a glider circumnavigate the world, but that would highly depend on the weather.
If you are interested in gliding, there are many gliding clubs around the UK and US where for a relatively affordable price you can experience it yourself, but be weary, if a lot of acrobatics are done it can feel like a long rollercoaster ride.
Let me know what you think of it, if you got the experience in one by leaving a comment.
Till then, see you next week.
Lift Sources - Soaring Society of America - https://www.ssa.org/lift-sources/
What is the Furthest a Glider has Flown - Black Mountains Gliding
https://www.blackmountainsgliding.co.uk/gliding-faq/what-is-the-furthest-a-glider-has-flown/#:~:text=The%20current%20world%20record%20for,20m%20wingspan%20glider%20in%202007.