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Words from our CFI Duncan Stewart

Converting to the Astir from K21


The Astir is our first single seat glider for our early solo pilots. It is fun to fly, rugged and inexpensive, but it seems a lot of people find it quite a handful when they try it for the first time. There have been number of incidents over the last year or so: wing drops during the aerotow ground run, inadvertent release in the early stages of the aerotow, pulling the airbrake lever instead of the yellow release knob, ground loops during the landing run.

 

The K21 is a particularly well-mannered training glider and allows you to get away with habits that may cause a problem in the other less forgiving gliders. In an ideal world we would instruct on a fussier glider and move people on to a more benign single seater, but there isn’t an obvious modern candidate for such a 2 seat trainer. So, the first few outings in the Astir can be quite a different experience, and it’s important that you are well briefed.


Astir Foibles during the Aerotow Launch


Wing Drop during early stages of the ground run:- At low speeds the Astir's ailerons are much less effective than the K21's. Full aileron may very likely be needed in the Astir – which would be very unusual in the K21. Our love of taking off down wind, with a crosswind component, undoubtedly makes wing drops more likely. Be ready to use more aileron than you usually do, and take off into wind on your first outing.


One of the key differences to the K21 is that it’s a tail dragger, so the tail needs to be raised unlike the K21 which sits with its nose on the ground. The rough ground at the southern launch point, combined with the solid suspension means that you may be tossed around quite violently while trying to raise the tail and level the wings. This distracting bumpy ride may be the cause of the second take off problem: inadvertent release.


Each of the pilots this has happened to reported that 'the glider released itself'. I think it is more likely that the BGA recommendation, to hold the release knob, means they pulled it when they hit a bump. Having your hand touching the release knob so that you can use it if you need to during the early stage of the ground run is a good idea. It might save you from pulling the wrong control if you are having a minor crisis. Firmly holding the release knob is particularly valuable at the start of a winch launch, as the rapid acceleration can very quickly turn a wing drop into a cartwheel. However, there is a bit more time to manage the situation during an aerotow, and cartwheel accidents are highly unlikely, so you probably don’t have to hold it so tightly that you pull it by mistake as you go over a bump. It is also worth considering when you no longer need to cling onto the release. Shortly after becoming airborne, you are likely to reach a point where, with the trees coming towards you, that the landing options become little more than a controlled crash. An inadvertent release at this point is definitely to be avoided.


Landing the Astir


After touch down, continue to ‘fly’ the ground run in a straight line and keep the wings level. Unlike the K21, the Astir has most of its mass behind the main wheel. Pilots need to recognise the early signs of yaw or a wing drop and deal with them promptly. If a yaw rotation begins to develop while decelerating on the landing run, it may get worse very rapidly and lead to a wing drop. Braking can make it feel as if the tail wants to overtake the nose, so beware of using the wheel brake unnecessarily.


Landing-on with too much speed will increase the likelihood of experiencing difficulties during the ground run. The recommended practice of performing a fully held off landing means that you land at the lowest speed possible, and pulling the stick back is not going result in you taking off again. I have noticed that some pilots are habitually not getting the tail on the ground during landing runs. make sure that you don’t touch down with too much speed, and get the tail down as soon as possible as two points in contact with ground will help stop the glider yawing.