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44. Decoration, subcontraction and instrumentation

06/01/2013

I took another look at the engine mounting plate and decided to have another go myself. It looks a little bit better, and since it’s completely obscured from view on the completed aircraft I’ve decided it’s probably good enough. At least it isn’t going to rust in a hurry, which is the main thing.

And suddenly over Christmas all those who are making bits for the aircraft are coming good – mostly on quotations and estimates, but some actual kit. Thus the seat is apparently made, but is awaiting the leather padding and cushion. The struts, which are being made on a specialist NC propeller-making machine, are modelled digitally and the next step is to cut a sample in scrap wood first to make sure it looks okay before using the real stuff, and we have an estimate for the next set of metal parts,to be bartered in exchange for an engine. Since the engine is single most important purchase we have to make, this is a big step forward. It’s been a salutary lesson to see how much they are going to cost if the labour is charged at commercial rates – it certainly helps to demonstrate the commercial replacement cost of what we’ve achieved so far – but at least it’s feasible, and so I’m starting to set the wheels in motion for this critical part of the project.

There’s no progress yet on the fuel tanks, which we can’t do ourselves, but we do have progress in another potential problem area – that of instruments. The instruments originally fitted are, unsurprisingly  hard to find, but I’ve come across a specialist in aircraft memorabilia who does a steady trade in aircraft instruments and he’s looking out for us. Many were fairly standard fit by that time, but apparently the compass is a very rare beast, and we may be lucky to find one.

Happily, the Scout had very few of them, most of the instrumentation you needed being located in the seat of your pants, each side of your head, and at the ends of your arms and legs. But we do need a tachometer (to measure the engine speed), an airspeed indicator, an altimeter, and a clinometer.

The latter is a spirit level (a curved glass tube with the ends pointing downwards, filled with clear liquid with a small bubble of air left in it) mounted on the instrument panel and used, weirdly  to determine whether the aircraft is flying straight. In essence, you commence a turn using the rudder pedals, and if the bubble in the clinometer moves to one side, you follow it with the stick – and that ensures that the aircraft is going straight through the air, rather than skidding sideways.

It’s one of those simple ideas that, once you’ve seen how it works, makes you smack the palm of your hand against your forehead and wonder how something so simple could be so effective.

In fact, it’s so effective that you’ll see something similar in the cockpit of every conventionally-controlled light aircraft today. There is one essential difference, however. In those days, the rudder was very effective and the ailerons (the controls at the ends of the wings that make the aircraft rock from side to side) much less so. As a result, standard practice was to make the turn with rudder, and the ailerons were used as a secondary control to keep the aircraft in balance.

Nowadays, the ailerons are so much more effective that they are used as the primary control, and the rudder has the secondary roll – indeed, on many modern aircraft, you really don’t need the rudder at all.

But the old bubble clinometer wasn’t instinctive if you used it to control the rudder – if the bubble went to the right, you had to remember to use the LEFT pedal, and so nowadays we have a slip ball instead, where the glass tube bends upwards at the sides and a little ball in the middle. The ball moves in the opposite sense to the bubble, and student pilots are taught to ‘step in the ball’ – if the ball goes left, you step on the left pedal, which pretty much everybody can remember instinctively.

When we get to fly the Scout, it’s something we’re going to have to remember, of course…

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