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187 – … and suddenly everything happens all at once!

12/08/2015

Yesterday was a really momentous day in the life of 1264.

Yesterday 1264 flew.

And before you remind me that she flew a month ago, and privately write me off as going quite definitely senile, let me explain. Only then you can write me off!

Gene’s flights a month ago were an enormous step forward, and demonstrated that the aircraft was well under control as rigged. Yesterday Dodge Bailey took the controls for the first time (Gene now being back in New Zealand) and the flight testing began in earnest.

We had hoped to get two or three hours of good weather in the early morning of Tuesday, so on Monday I’d travelled down to check everything over and get the various instruments ready for Dodge to make proper calibrated tests. The only change to the airframe was to amend the gap seals between the upper wings and centre section so that they were a bit more airworthy. Rick came down in the evening, and we both spent an hour or two checking and rechecking everything we could think of.

On Tuesday morning, my alarm went off at 0500, and I got to the airfield at 0550. Rick and I managed to get the enormous hangar doors pushed open and the Scout rolled out. dodge turned up just before 0600, and we had a cup of tea and went through the plans for the first flight, and made sure all the instrumentation was the way Dodge wanted.

Dodge getting familiar with the layout of the office.

Dodge getting familiar with the layout of the office.

The weather was absolutely perfect – there was no discernable wind, and a high cirrostratus meant that we were unlikely to get much thermal activity.  Dodge got way in fine style, and was soon up at 2000ft – higher than 1264 had ever been. His focus of attention on this first flight was to calibrate the air speed indicator, which means heading into wind, setting the speed at a particular figure and seeing what the GPS says. Then when you’ve tried of each of the speeds you want (Dodge did 40, 50, 60, 70 & 80 knots), you turn round downwind and do the same thing. By taking an average of the two groundspeeds, you can factor out the windspeed. In fact, on that first run, the two numbers were astonishingly similar, and showed that the airspeed indicator was reading slightly low.

If you’d been attending classes regularly, you’ll remember that we checked the instrument against a calibrated one a little while ago and found that this too indicated that it was a bit slow. So why bother doing the same thing in the air? Because errors can creep in at the measuring point – the two little tubes sticking out in front of the port wing strut.

It’s very complex, and it would have been much simpler if from the outset we’d taken to measuring the angle of attack of the wing instead of its speed. but that’s another story, and not for now!

One of the main unknowns – particularly in the case of the Scout – is the longitudinal stability and how far it’s possible to move the centre of gravity (or CG for short). When you design an aeroplane, you try to arrange that the wings are positioned right where the centre of gravity is, for the same reason that you lift a tree branch from its balance point.

If you don’t,  the branch will tip up, and so it is with an aircraft. As with the branch, it’s usually possible to put up with a small degree of latitude in the position, and for an aircraft we need to be able to cope with variations in pilot weight, fuel load, etc., so we spent much of the rest of the time filling and emptying the petrol tank and strapping bits of lead flashing to the front and back of the fuselage in order to check that there was sufficient control in all phases of flight.

In between all this, Dodge tried out some stalls, steep turns and long climbs in order to prove that the handling was normal and that the engine cooling was satisfactory.

By the end of the day, we had virtually completed ALL of the work required to allow completion of the flight test report, which was several miles further down the process than i had expected to be, and Dodge seemed to be reasonably confident that we should be capable of flying it without any nasty surprises in store.

In his summary, he said that it performed much as he would expect an aircraft of this vintage. He said the roll rate was as good, or possibly better than the later Sopwith Pup and SE5A which are often held up as aircraft with fine handling characteristics. the stall is safe and predictable, and in the steep turns he was able to detect – in mild form because of the relatively low-powered engine – the Coriolis (gyroscopic) effects which caused so many problems to pilots in WWI.

In essence, when you sharply rotate the nose of the plane upwards, it causes it also to want to turn to the right. The most common time you come across this is not in level flight, but in steep turns. So when you turn steeply to the left, you are pulling the nose upwards, and the Coriolis force to the right tends to make the nose rise. This is inherently safe, and because you have already applied left rudder to initiate the turn, you simply apply more left rudder to keep it going round in a level turn.

But in a right turn, it tends to make the nose drop, and you have to switch from applying right rudder to initiate the turn to left rudder to counteract the Coriolis forces, and if you aren’t expecting it, this can cause problems.

Landing and takeoff presented no particular problems, though Dodge confirmed that there was no crosswind capability at all. You have to land exactly into wind.

We also demonstrated that the CG was perfectly safe with the CG well forward. this was to check that Rick, who only weighs 70kg, would be able to fly it with full tanks, and this too proved quite satisfactory.

So far, so very, very good.

But there were a couple of outstanding issues that raised their heads during the day that will need to be resolved before we fly again.

The effect of 30 minutes' flying

The effect of 30 minutes’ flying

The first is all that oil. Everyone expects a rotary engine to throw out lots of oil, but 1264 produces far more of it than most. You may remember that we spent a while fitting a seal between the firewall and the cowling, and I was very disappointed to note that things seemed not a jot better, as you can see. At this rate, the fuselage will need recovering in a couple of months, and while we were never very happy with it to start with, this is certainly an unacceptable rate of deterioration.

The second is the plugs. The engine ran very sweetly for Gene, but of much of today the engine sounded distinctly uneven, and by the time we got to the afternoon, it clearly wasn’t right. We took all the plugs out and cleaned them, and it was even worse; in fact one plug wasn’t firing at all. After a hurried conversation with Jean Munn at the Shuttleworth (where would we be without them?) we removed the lot and Rick and I drove them up to Old Warden where Andy and Phil tested them , cleaned them (properly!) and retested them. We dashed back to Bicester, refitted the plugs, and when we started it, we got a full 1100 rpm. we waved Dodge off, and he set off to complete the final 40 minutes flight, including the 5 minute climb. The climb was completed satisfactorily but by the end the engine was sounding uneven again, and after 20 minutes he returned.

But all isn’t gloom and doom. As always, we come back with loads of good advice from the Shuttleworth, and Andy and Phil recommended switching to a different type of plug, with four electrodes instead of two. they also recommended removing the plugs after every day’s flying and cleaning them. Today I’ve been in touch with the Green Spark Plug company and was delighted to find they had sufficient of the new type of plug for two complete sets. So the order has been placed, and we will have to work out how to swap the connecting caps over from the old plugs when they arrive.

And having got home about midnight I couldn’t sleep, so at 0430 this morning I took a look at the manual for the le Rhone engine to investigate a theory about the source of all that oil.

Before we’d left, we’d topped the oil tank up to where it had started, and confirmed that it’s pumping through the correct amount  about 5lt/hr. But I couldn’t understand how the whole of the firewall was covered in a thick film of oil. the oil from the exhaust valves will mostly go downwards, with some being sprayed round the inside of the cowling, but there didn’t seem to be any way it could end up all over the firewall, and particularly such fresh oil.

The only possible explanation was that the main crankshaft bearing oil seal wasn’t working, or was missing altogether.

I had been concerned that if there was a lip seal, it might be necessary to dismantle the entire engine to get at it, so I was mighty relieved to find that it’s actually a felt ring which is contacted by the bush in the front mounting plate.

2015-08-12 Felt seal (531x800)

We’d assembled the engine onto the mounting plate, of course, and hadn’t (in our ignorance) checked this particular feature, so we don’t know quite what’s in there, and my bet is that it might be missing altogether. Replacing it will require extracting the engine from the airframe, but this is pretty straightforward, and I’ve done a deal with Jean Munn to do the work at old warden under the supervision of himself, Andy and Phil. We’ll also take the opportunity to get a second opinion on the design of the lip seal to see if we can improve things. But my bet is that the felt seal should pretty much do the trick…

 

 

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