Coaching Corner… Stay vigilant near gliding sites…

It pays to be vigilant when flying near gliding sites for a number of reasons, as Head of Coaching David Cockburn suggests. Plus, when did you last get a transponder check?

I’m pretty sure many of our members are, or have been in the past, glider pilots. However, there are a significant number of our pilots to whom what I am about to say will be new information, and the rest of us (including me) can always benefit from a reminder.

Our charts include markings for several features such as the letter G in the circle in the centre of the extract illustrated. Of course we all know what it means – this is a glider launching site, and we should be prepared to encounter gliders. However, as I expect we also know, there is a specific hazard which the marking highlights with the number following the ‘/’ written beside the ‘G’ symbol. Winch launching takes place, in this case up to 2,800ft above sea level (asl) – 2,000ft above the site, which is itself 800ft asl.

The gliders attached to the winch cables will cover most of that 2,000ft in about 15 seconds, and drag the cable very steeply upwards.

Glider launching cables are usually braided steel, which when moving under tension can saw through metal girders, so the hazard to our own aircraft and the unfortunate glider crew is pretty obvious – there have been fatalities in the past.

Many other serious accidents have been avoided by the sharp eyes of the launch team, but trees can hide an approaching aircraft until it is too late, and the noise of an

Below aircraft engine can be drowned out by other mechanical noises on the ground.

The normal times of glider launch operation are published in the UK AIP, and supplemented by Notam. However, these are only the ‘normal’ hours of operation. For various reasons launching will sometimes take place outside notified hours, so the hazard should always be expected.

Whether within notified hours or not, it seems that some pilots believe that it is perfectly safe to fly over a winch-launching glider site if they see no activity actually taking place, or if the weather appears unsuitable for soaring flight. They may argue that unless the launch site has an Aerodrome Traffic Zone (ATZ), there is no legal reason why they can’t fly through the circle marking the launch site below the published launch altitude. However, the launch of a glider requires very little supporting equipment, which may not be immediately obvious to an approaching aircraft. We should also be aware that it is against the law to endanger an aircraft.

So, does this mean that if we stay outside the marked circle there should be no problem? I’m afraid not. After launching, glider pilots invariably seek a means of extending their flight time. Numbers of them can often be found above the into-wind slopes of hills in the vicinity of the launch site, and these slopes usually stretch well outside the marked circle. Although gliders can be found anywhere in the country climbing in convective upcurrents (‘thermals’), and cruising at high speed between them, thermals near launch sites often contain large numbers of gliders circling in the rising air and climbing at rates, which although often quite slow, can sometimes exceed 30ft per second. And gliders, especially when pointing directly towards or away from us, are very difficult to spot.

Whether or not the glider site has a published winch launch altitude, many gliders self-launch, and others are towed by aeroplanes. These need to maintain their take-off direction for some distance before they are able to change direction safely; consequently their climb paths tend to extend beyond the marked circles, generally upwind of the sites.

Even when safely well above the ground, the combinations have restricted manoeuvrability, hence the rule that powered aircraft must give way to them. To maximise the glider’s ability to extend its flight time, pilots of both self-launching and towed gliders prefer to start their search for sources of lift some distance upwind of the site, so it is worth remembering that that area of sky is likely to contain large numbers of gliders. Winchlaunched gliders will seek to do the same, albeit probably a little closer to the site. Class G airspace is free for all, but remember that a glider on a converging course has right of way. As a particularly lazy pilot I try to avoid having to make any unnecessary last-minute manoeuvres to avoid hazards, so I try to keep clear of glider sites and the area upwind of them, unless I am actually flying a glider at the time!

Not that we need to keep away from glider sites all the time. They are often situated in areas of natural beauty which we might wish to visit. A glider site is an aerodrome, and many are quite capable of operating powered aircraft. Indeed, a number of gliding clubs welcome visitors in aeroplanes. However, all stress very strongly the need for the visiting pilot to obtain permission, and a thorough briefing from a club official, before attempting to land there, or even approaching the site. Even a light wind at sites in hilly areas can produce unwelcome turbulence, but each glider site has its own particular hazards in the air and on the ground. It is vital to stick to the local rules and procedures.

Transponder Mode C check on 1013

The CAA’s current emphasis on airspace infringements has highlighted some possible problems with transponder Mode C altitude reports. There have been cases when the information reported by the transponder to the air traffic control radar has been incorrect, and some pilots have been accused of infringing notified airspace when they were actually well below or above it at the time.

Every time we communicate with a radar controller he or she can be expected to ask us to confirm our altitude against what they are seeing on their screen. That’s what they are doing when they say ‘request altitude’ or ‘request altitude passing’, and all they want is a report of whatever our altimeter is reading at the time we reply. However, if we do not normally talk to a controller we may be unaware of any fault on our transponder. It may be an idea to deliberately call a local radar controller and have our transponder altitude readout checked from time to time, especially if we plan to fly close to notified airspace in the near future. Preferably when the frequency is not busy, a simple call of ‘Request transponder check’ should give both the controller and you confidence that your equipment is working correctly.

Even if a controller is not immediately available, many transponder displays, such as the one illustrated, provide an indication of the pressure altitude that their sensor will transmit. If we temporarily set our altimeter to 1013 HPa, perhaps after engine start, the transponder indicated pressure altitude should be the same as that indicated on our altimeter, in the case of the picture -50ft. If it isn’t, we should have the fault investigated and switch Mode C off until it is rectified. ■