Just to make it clear, I'm not saying the pipeline survey aircraft are 'causing a problem', they've got a job to do. To be honest I haven't got a clue what speed they would do...you would have thought at 20kts they use a lot of fuel!

Well, I'm not a pipeline surveyor, far from it, but what I understand is that they're not surveying the pipeline per se. For starters because it's normally buried underground, and an actual leak would be detected via sensors in the pipe itself, or via an inflow/outflow discrepancy, pressure drop or something. Instead, what they are actually surveying from the air is activity on the surface which may have an impact on the pipe. Unannounced/uncoordinated digging/site development for instance.

I assume this is done at normal cruise speeds, with the ability to hover and take photographs as required.

At our gliding site, Cotswold Gliding Club at Aston Down (N51.42.358 / W0002.07.916) we have wire launching notified up to 3000ft AGL (3600ft AMSL). The main hard runway is 03/21 and 5000ft long. With a reasonable head wind of say 15-20 kts some of our lighter gliders (such as single seat Ka8) will get c. 2500ft AGL on the launch. Many others will get 2000ft AGL on the launch. The less the headwind the lower the launch.

The same applies to Lasham in Hampshire, with many more gliders in the area normally.

At Aston Down we regularly experience powered aircraft coming through the overhead below the glider launch height, often en route into Kemble (not outbound so much as Kemble brief accordingly). Pilot possibly relying on GPS navigation and not combined with 1/2 mil map reading? In more recent years the message seems to have been understood and more traffic seems to fly around our site with adequate margin. But not all.

Some time ago I remember seeing a photo (from within mainland Europe) of a an aeroplane that 'mixed it' with a cable. The wing was half severed but fortunately the pilot got away with it and landed safely. I believe the CAA publication GASIL published the photo

One of our club members who sits on the Airprox Board as a GA & gliding rep produced a paper a few years ago setting out the time factors involved in sighting (or hearing) a light aircraft approaching a winch launch gliding site whilst the launch process was started (always with a ground based launchmaster visual check of the sky). It was a detailed analysis and showed that from the time the launchmaster gave a visual all clear to launch, to the top of the launch for the glider, an approaching unsighted powered aircraft was likely to have travelled a greater distance than was possible to detect visually at the start of the glider launch procedure. I'll see if this document can be posted as an attachment or link, later. It makes interesting reading.

Nuff said.

Which is why in my paper about Flarm and PCAS etc., I suggest that winch launching gliding sites should consider having a PCAS at the launch point – it will alert to transponding GA aircraft approaching that are at first not in view of the launch point controller.

I knows it is not all the possible conflicts, but anything that helps avoid another tragedy is worth it in my view.

(Copies of the latest version available by email to identified and non-hostile correspondents.)

Chris N.

Example issues, or come and see for yourself
 

(Come to a gliding site and have a trial lesson - you'll be welcomed and will almost certainly enjoy the experience)

See "Section 1 Flying close to or over active glider or para drop sites" in
http://www.airproxboard.org.uk/docs/423/gab15web.pdf

Consider the power and energy involved in

• 0-50kt in 3s (cf "Top Gear" thinking a Lambourghini's 0-60mph in 6s is fast),
• 0-2000ft in 30s climbing at 35-45 degrees (so horizontal visibility is somewhat limited :)

Higher launches are possible in high winds e.g. my last flight was to 2300ft in a K13, and IIRC 2800ft has been achieved.

Consider the effect an ~6mm steel cable travelling at >60kt will have on an aircraft wing (think bandsaw :)

Why is a glider like a barrage balloon?
 

A more obvious example is to think of a glider being winch launched as a fast-moving and not-very-visible barrage balloon that suddenly leaps into the sky. Worth avoiding :)

effect of winch launch cable on wing
 

was it 7 or 10 years ago, that a visiting aircraft, after we suspect a merry luncheon in a local pub, took off despite safety briefing THROUGH A LAUNCH CABLE. Fortunately the glider had already let go, and the cable was descending on its parachute so perhaps not as taut as it might have been.

The cable separated from the wing before the wing was sawn off, in fact, the pilot continued his flight to his home airfield, and did not report the incident until the following day, so we were told. There was damage to the wing.

Not everything gets reported to the authorities.