Thursday, 21 April 2011

Lovely sunny day, but no good for flying.

Our dH Chipmunk has been out of action since late January initially because it had its scheduled 'Annual' major service at Barton (see earlier post in the Blog), then a further delay when the elevator trim tab cable failed on a post-maintenance test flight and we had to source another, and finally a delay as the Civil Aviation Authority were tardy in completing our paperwork. But last week it became available again and I had it booked for today as the weather looked to be set fine.

Well, it turned out to be a completely unflyable day weatherwise. It was sunny, hot, and to anyone who is not looking at the weather from the point of view of going flying, it looked an ideal day. But we have enjoyed many days of fine weather recently, caused by a high pressure system centred over the UK. High pressure brings low winds and stable descending air. Stable descending air mitigates against cloud formation, hence the lovely weather. But in preventing vertical air movement, or thermic activity, it causes all the crud and smoke and dust in the atmosphere to build up from the surface upwards, rather than being carried away vertically by thermic activity as normally happens. The result is a steady deterioration of visibility (and incidentally, the poor air conditions are problematic for those with respiratory problems, such as asthmatics). I was expecting this of course, but the Liverpool TAF (Terminal Area Forecast) on the internet stated visibility of 2,000 metres at 9:00 this morning, improving to CAVOK (10Km or more) by mid morning. So I drove to Liverpool Airport fully expecting a hazy but enjoyable flight.

I arrived at the aeroplane's new handling company of Ravenair (previously we were based with Liverpool Flying School - more about the reasons for this change will be aired in a future post on this Blog) at about 10:30 and immediately realised the visibility was not improving as per the forecast. The control tower on the south side of the airfield was easily visible, but a bit hazy. There was absolutely nothing to see beyond it. The far side of the Mersey estuary was invisible and I knew visual flight (which is what we do in the Chipmunk - as opposed to instrument flight that airliners can do) would be impossible. Once airborne the ground would vanish and there'd be no horizon, a recipe for disorientation and disaster. And anyway, it wasn't even legal to attempt visual flight in that visibility.

So I went home. And Chris and I had a very nice pub lunch in the garden of the Railway Inn at Mobberley... in delightful sunshine. The hazy shapes of jets passing low overhead having just taken off from Manchester Airport reminded me I wasn't missing much flying-wise. Indeed, as I drove within a mile of Frodsham hill on the journey home, its misty outline was barely visible in the haze.

By the way, these high pressure weather conditions that bring us hot rain-free (if hazy) days at this time of the year, bring deep freeze conditions in winter. The absence of cloud cover allows the earth's heat to radiate away into space, the weak sun in winter can't compensate, and the earth gets deeply frozen. It happened in the 'big freeze' of 1947, again in my memory in the winter of 1962/63, and it happened in December of last year. So really cold weather is due to winter high pressure. And what's the other characteristic of high pressure weather? NO WIND!

So if any politician tries to tell you that we can rely on wind power to generate our electricity, just remember that at the times we most need power, wind will be absent.

I do wish these decisions on future power could be made by engineers rather than politicians, but hey, windmills are very visual - voters can see them and the less knowledgeable might think they are a symbol that the politicians are 'doing something' about clean power.

Oh dear!

Anyway, I have re-booked the Chippy for a few weeks hence (hey, I'm busy!). Bet it will rain!


1 comment:

  1. dear Vince, please excuse my cheek. I am part of the organising team for the Train of Hope charity appeal. We have several aviation items up for auction on ebay link-:

    There will also be several railway interest items for auction as well. Please visit for details.

    Your blog makes retirement fun- all the promises I have heard about my (dismal)retirement prospects would power one of the windmills you refer to.

    Steve griffin