Getting ready to fly before the event
Here’s the order of preparation prior for a flight. This is the result of the collective experience (sometimes bitter!) of many Carrier pilots.
Several days before an event (or even before a simple practice session), you should inspect your model for wear and tear. Obviously much of this activity, though not all, will not apply to a new model. The life of a carrier model can be quite punishing and damage which goes unchecked often manifests itself later in the most inconvenient way, usually by spoiling a competition flight. Make sure all nuts, bolts and screws are tightened right up and where the threads are metal-to-metal, they have been treated with a thread locking compound such as Loctite. There’s no need to use anything stronger than a standard strength compound. The only exceptions are the cylinder head and crankcase cover bolts on the engine, which don’t normally require such treatment.
Ensure that all of the control system items are soundly fixed to the airframe or to each other, that they work properly without undue friction and that there’s not any excessive slop anywhere. This also includes the more obscure areas such as the horn (is it still firmly fixed to the elevator?), the elevator joiner (any flexibility between individual elevators?) and the elevator hinges (any visible tearing, splitting or parting of company?). Check the leadout cables in particular, replacing even the slightest fray with a complete new component.
Look critically at the airframe, notably at the wing/fuselage and tail/fuselage joints. These are classic sites for gradual fatigue cracking due to abrupt changes in material shape and stiffness which lead to stress concentration. The worst site for a profile-fuselages Carrier model can often be at the wing leading edge due to the outward flexing of the fuselage under the relatively large weight of the engine. Check also for cracking round the hook pivot reinforcement and if the model is equipped with a hook release, make sure that it works satisfactorily and that all the components appear undamaged.
Test possible cracks anywhere on the model by flexing the airframe in such a way that a crack will open up. If it does, run a knife blade the full crack length to widen it slightly, flex it open again, fill the fracture with the runniest superglue you’ve got and release the airframe so the crack closes up again. If the Cyano is thin enough, capillary attraction will draw it into the very extremities of the crack and the entire fracture will be locked solid. Do this with even the tiniest of cracks – they’re tomorrow’s big ones!
The day before an event, use a previously prepared (and debugged!) comprehensive check list to make sure that nothing gets forgotten. Such a checklist can only be based upon your own experience and tends to grow with time – so start writing it now as it’s not a five minute job! This way, you can arrive at a flying event (reasonably) confident that if your flying is brought to an early end or prevented altogether by some failure, at least it won’t have been due to an avoidable mistake or simply having left a vital part of equipment behind.
Getting ready to fly at the event
Once you’ve arrived at an event, the first thing you should do is to speak to the Contest Director, pay the contest fee and find out the actual times of flying so that you know exactly how much time you have to sort yourself out and whether and when any practice flights will be allowed. Then find the line park or, if one has not been provided, a sensible position near the flight circle but away from the obvious walking routes. Unroll your lines and connect them to model and handle. Inspect every inch for frays and kinks and discard any line without a second’s thought at the sign of the slightest damage. This is where at least one spare line of the right length can be very useful. Don’t ever skimp this check – the consequence could easily be the complete loss of both model and motor. Just think of all your hard work at risk, as well as all the safety aspects. It’s just not worth it!
Now check to see if you’ve connected the lines up correctly. There are always going to be some times when you haven’t. Find a helper, preferably the flying colleague or even team mate who is the person likely to be helping you to start your engine/release your model. Get him to hold the model horizontally at eye level while you pull the lines tight and move the handle until the fuselage is in the normal flight position.
If this is one of your first flights, you won’t know what the normal position is, so assume the fuselage flies tangentially to the circle and move around to get the lines perpendicular to the fuselage. Make sure that a reasonably neutral handle position gives a neutral elevator setting. If it doesn’t, changing to a different length line connector to shorten or lengthen a single line may well solve the problem, but it may also alter the throttle setting. It’s best to either change the length of both elevator lines by shortening one and lengthening the other by equal amounts, or to move the elevator linkage at the horn if you have a quicklink mounted on a threaded rod. If you use a hook release, check that the elevator angle at which it works is unlikely to be reached by the movements required during normal flight and that the angle can be comfortably produced by a quick downward (or upward?) jerk of the handle.
Without the motor running and keeping the lines tight, open the throttle fully at the handle end and get your helper to look down the carburettor. Is the venturi fully open? Now shut the throttle. Does the venturi close right down as well?
Lack of full movement at one extreme usually means that your handle or bellcrank has reached the limit of it’s own travel before the throttle has. Whatever adjustment you make, be careful that you don’t simply transfer the problem to the other extreme of movement. If this is what actually happens, it means that the throttle arm travel is simply greater than that of the combined handle/bellcrank combination and the throttle arm throw needs to be reduced by selecting a hole closer to the pivot. The ideal is to have handle movements which are fractionally less than those of the bellcrank but slightly more than those of the throttle arm to ensure that the full range of throttle settings can always be obtained at the handle end of your lines.
Leaving your handle and lines on the ground, fill your tank and run your engine at a moderate speed for a minute or two. You should not check actual engine settings and throttle response until the motor has reached normal operating temperature. Most throttle types, though certainly not all, are set by first adjusting the engine for maximum speed and this is done at the full throttle opening simply by gradually leaning the mixture out using the needle valve. Once the peak revs have been reached, the setting should be richened by 200 rpm or so to allow for the slight leaning-out that happens once the model is airborne and subject to the load on the prop lessening and centrifugal force acting on the fuel supply. This is usually equivalent to no more than reducing the rpm by the smallest audible amount. Now shut the throttle and the engine should drop to a satisfactory idling speed.
Providing the engine will keep running, the slower the idle rpm, the better. A fast tickover is not a good setting since power is still being delivered and this may make it difficult to execute some types of landing technique which rely on a slow approach.
Let the engine idle for about 20 seconds and then bang the throttle open wide. The revs should pick up almost instantly to full or near-full power. Although some types of carburettor design are better than others in this respect, you really must have a quick response, particularly during the slow flight when you need instant power to pull the model out of the stall that you always have to fly so close to. Try this several times and if you don’t think the response is good enough, or if the idle is too fast (or even too slow), then the carburettor needs adjustment. Be careful here! Don’t undertake any adjustments lightly. There are many different types of carburettor, all of which vary in the way they achieve fast and slow mixture control and in sensitivity to adjustment. Unless you understand exactly what to do, it’s better not to fiddle unnecessarily at all. If adjustment really is needed, always refer to the manufacturer’s instructions, make only very small changes, and check for their effect each time. Best of all, get an experienced modeller to help you.
Once you have made any necessary adjustments to the carburettor, make sure you can get the same performance at the control handle end of the lines. Not even this double-check is a guarantee of faultless operation in the air, however. Airflow drag and turbulence can act on the lines and the model control system in peculiar ways, and such effects are not always predictable.
As the checking and adjusting of throttle movements and carburettor settings described above can sometime be a little involved, it is ideally carried out prior to a competition. Unfortunately domestic limitations on space and noise usually mean that most aeromodellers have to perform these activities at the actual competitions.
Right! Your engine is now properly set up and you’re happy with the model/lines/handle arrangement. Lay it all out again in the line park (if provided) or find somewhere safe where people won’t walk over your lines. No, you’re right. No such place! Anyway, have something to eat and drink, try and lose those pre-contest butterflies and wait either for an opportunity to practice or to be called for a competition flight.
Whether you’re indulging in a simple practice session or in a proper competition flight, your actions should be pretty much the same. Practicing is normally used to check the engine settings for the fast and slow runs and to see how the wind conditions of the day affect the slow run, as well as usually trying some slow flying and landings, as practice in these techniques is never wasted. It isn’t often that a practice session is used as a dummy competition flight, but there’s usually no objection to this provided that you can get someone to time your flight.
The Contest Director will probably do this if asked.