Friday, June 20, 2014

De-icing with bug wipers...

WGC2014 – Rayskala, Finland 
20 June   (Second official practice day)
by John Good

Today’s weather did in fact match the forecast that called for improved soaring conditions.  The catch was that our window of good weather lasted from about 9am through 12:30.  Had we been launching at about the time of the daily pilot briefing (10:00), a respectable short task might well have been possible for all classes.  As it was, the launch began at noon, and the early pilots in the first class (Club) found good lift.  But the sky steadily darkened, light rain fell on the airfield even before the launch was complete (with plenty more visible to the west and northwest), and for most pilots the hoped-for good soaring conditions never materialized.

A pattern is emerging.  The good lift (there has been some most days) is largely a product of very unstable air.  Little solar heating is needed to get this going, so even the day’s early cumulus clouds can keep gliders in the air.  But unstable air and even moderate solar heating readily leads to overdeveloped cumulus clouds, spreadout, and rain.  Until this pattern changes, I think we can expect conditions that “cycle” rapidly – within half an hour, good lift can change to rain and put gliders in trouble (or on the ground).  For success, pilots will probably need to fly patiently, anticipate problems, and make plenty of detours.  Crews will probably be doing multiple retrieves.  Task setters will need to take care that pilots are sent into areas where safe landing fields are available.  The patience of Finnish farmers may be tested.

An interesting pair of devices seen of most gliders here are “bug wipers”.  In normal years, Finland produces an impressive crop of small flying insects, the remains of which steadily accumulate on gliders’ wings, increasing drag and compromising the normally amazing performance of modern composite wings.  A bug wiper is a spring-loaded device that spends most of a flight “parked” at the leading edge of its wing, next to the fuselage.  When the pilot decides the number of smashed bugs warrants attention, he cranks a sort of fishing reel that releases the bug wiper, at which point air flow causes it to track along the wing.  It drags small wires along the leading edge, which scrape away some portion of the bug remains, restoring (at least in theory) smooth airflow.  Once the bug wiper has reached the limit of its travel a short distance from the end of the wing, the pilot reels it in, back to its parked position.

If this all sounds to you rather Rube Goldberg-ish, you’ve formed an accurate impression.  These devices are expensive (a set can easily cost over $1000) and prone to failure (they get hung up partway out the wing, fall off, etc.).  But pilots hate the idea that they might have to suffer a handicap a competitor could avoid.  In my view, this issue would have been best dealt with by a rule that bans such devices in competition – that way, all pilots would face the same problem and manufacturers would have an incentive to design airfoils that tolerate contamination without losing much performance (something that would benefit all pilots).

Of course, this year isn’t normal in Finland.  The bugs have responded to abnormal cold by laying low, waiting for better weather.  Wing contamination hasn’t yet been nearly enough to justify the nuisance and drag penalty of bug wipers.  But most pilots have been carrying them during the practice period, if only to get used to them.  And today, Garret Willat found an unanticipated benefit: in the cold air under an early cloud he noticed a light accumulation of rime ice on his wings, and found that his bug wipers (okay, make that “ice wipers”) could deal with it.

Tonight we enjoyed the first big social event of the contest:  the contest organizers and Team Finland hosted a “Midsummers Eve” party.  This marks the summer solstice, and is a big deal in Finland.  We celebrated with salmon soup, schnapps, beer, sausages, and ice cream – all very good.  I’m not sure the dress code – which was basically “wear every warm thing you brought” – conformed to tradition, but the mood was certainly good.  A giant bonfire is promised at midnight – I’m not sure I’ll last that long, but perhaps.

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