Many of the procedures and techniques used for Class 1 competition flight are the same as those used for Basic Carrier Deck. Where this is the case,reference will be made to the appropriate BCD text to avoid duplication of identical material in this section.
1. What length lines?
The rules require the distance between model and handle centreline to be between 60’0″ and 60’6″. Make your lines up so that length is as close as possible to 60’0″ (but never less) since speeds and therefore scores are calculated using 60’0″. Longer lines will simply increase lap times and reduce scores. An extra 6″ will cost you about 0.5 – 0.8 points and whilst this might seem small, contests have been won (and lost!) by this margin before.
2. What type of propeller?
Success in Class 1 is dependant to a considerable extent on speed and the choice of propeller is therefore much more critical than in BCD. Nevertheless, the same practical considerations still apply, ie: flexible blades are likely to survive deck impacts better, but stiff blades are usually more efficient and consequently produce faster speeds. As with BCD, however, the only real way to find the ideal airscrew is by trial, error and measurement by stopwatch. The golden rule to remember is that top speed is the most important factor of all. Your efforts must always be directed to minimising the time taken to execute the first 7 laps from the standing start on deck, and the engine must be propped with this in mind.
3. What sort of fuel and glowplugs?
You should by now be getting the message that Class 1 means high speed and therefore requires as much engine power as possible. Whilst diesels have occasionally been used in BCD with some success, the brute power required in Class 1 can only come from glow motors. The addition of nitromethane to model piston engine fuel is usually the single easiest way to produce more power, but nitro percentages cannot simply be increased. As a general rule, beyond about 10-15% nitro content, you should start to reduce cylinder compression ratio by the addition of thin shims under the cylinder head. Failure to do this will lead to the rapid burnout of plugs and perhaps even damage to some of the engine’s mechanical components. Nor is is merely a case of shimming – some engines are simply not designed to perform on high nitro fuels, so you should make sure you know the limitations of your power unit intended by the manufacturer.
Engine power increases by tuning have been subject in the past to publications that have dealt solely with this matter. Such modifications are a very specialist subject and whilst certainly worthy of attention once you have begun to build up your Class 1 experience, much of this type of work is carried out by recognised experts and the details are really beyond the scope of this document. Refer to the specialist tuning press for such details.
Once high performance of an engine becomes critical to success, the glowplug becomes a significant item. This is even more so when high nitro fuels are used. Unfortunately, the very plug qualities required for a robust element during the wear and tear of the high speed run, ie: colder plugs with lower grade numbers, are those which tend to make the fire go out during extended low throttle periods. Whilst this can perhaps be offset by the use of a barred cold plug, the problem is to some extent mitigated by the Class 1 technique of flight at or near 60 degree attitude during the slow run. In this type of flight regime, much of the lift is derived from the propeller’s vertical thrust component and the engine is consequently operating at a relatively high power setting which keeps everything at a sensible operating temperature. In the final analysis, plugs are much like propellers – trial, error and the stopwatch is really the only way to determine the most suitable type. Get ready to fly before the event
Most of the advice given for BCD is applicable here, with the proviso that Class 1 models are usually more highly stressed by virtue of being smaller, faster and having more powerful engines that operate at substantially higher revs. The pre-flight checks should therefore be even more critical, no matter how inaccessible some of the structural components may be. If something comes loose or falls off (…something always will!) and you could have prevented it by a simple inspection, you’ve only got yourself to blame.
4. Get ready to fly at the event
Nothing different here, so re-read the BCD advice.
5. Flying techniques
Marking your landing position and setting up the pilot’s circle are executed slightly differently to BCD. Since the flight radius is fixed, the pilot’s circle (a brightly coloured 3ft circle – that’s 3ft, not BCD’s 3 metres) is fixed in position so that all pilots fly from the same circle centre. The only operation therefore required is to decide where and how to mark your landing position and this is no different to BCD except that you cannot move the circle to act as the marker.
6. Starting your engine and final pre-flight checks
Again, nothing different here, so re-read the BCD advice.
7. The Take Off
The requirements here are no different to BCD, although it is worth emphasising yet again how important the high speed run is. Particular care should therefore be taken not to slow the model down in any way, either by a take off that’s too steep, not holding the handle against your chest and pivoting on the spot, and flying an undulating flight path.
8. The Fast Run
A competitive Class 1 model is most in its element during the fast run, so if the speed is frighteningly fast and the model seems to be trying to pull your arms off (you are holding on to the handle with both hands, aren’t you…?), you’ve probably got it about right!
9. The Slow Run
This is probably the activity which can exhibit the greatest differences to the techniques used in BCD.
Although it is clearly sensible to execute slow flight by extending your arm as much as possible and walking round the diminutive pilot’s circle, the slow run is now less significant to your overall score than it is in BCD. By virtue of the potentially more problematic handling of a typical Class 1 model, you may feel that a successful flight is more likely to be achieved by pivoting in the centre and applying your full concentration on extracting the model’s best slow run performance rather than worrying about your own performance as well.
If your Class 1 model is equipped with nothing more than a speed control system and a hook (and some successful models have had nothing more…), then skip the next bit and go on to read about the different types of slow run flight attitude. There’s no need to drop the hook – why lose that little (but potentially valuable) bit of useful airspace beneath the model when you might need it for stall recovery?
Most Class 1 models, of course, have a variety of devices designed to enhance slow run performance. Each different system will almost certainly alter the trim of the model and it is naive to hope that such effects will collectively be insignificant. The reverse is almost a certainty! This means that when you trigger off such devices, typically by a brief burst of down elevator, you must be prepared for a substantial change in the model’s pitch, yaw and roll attitudes. This can be quite violent, but you must be ready for it by slowing down to a moderate speed and giving the model a reasonable amount of height in which to recover, if this proves necessary. Most models drive their slow flight systems off the arrester hook, although this means a deployed hook during the slow run and consequent loss of the recovery airspace previously mentioned. It may be worth considering independent triggers, so that up elevator fires off the slow run systems and subsequent down elevator drops the hook when the slow run has been completed. Complicated? Nonsense! Mechanicity is what Class 1 is all about!
It is worth noting here that whilst ditching during a BCD flight brings instant and complete disqualification, the equivalent in Class 1 is ‘flight termination’ (Rule 7) in which the flight score is not lost, but merely limited to the scores accrued up to the instant of termination.
There are two main flying techniques for executing the slow run and they are described below.
- AERODYNAMIC FLIGHT: The easiest (!) is when the model is flown just above it’s minimum stalling speed at an angle of attack as close to the stalling angle of the wing as possible – typically 10 to 20 degrees, depending on the characteristics of the aerofoil section. This is aerodynamic flight, because the wing is working as a proper aerofoil. This is typical of the approach to BCD and the whole of that text devoted to slow flying applies here. However, unlike BCD, there can be many systems augmenting slow aerodynamic flight in Class 1 and considerable practice may be required to arrive at the deflections and movements which set the model up to produce the slowest speeds of all. Flight during this experimental phase will clearly be assisted by the provision, right back at the design stage, of suitable access hatches to all systems and means of adjustments to those systems. Aerodynamic slow flight is much easier to master when you’re learning to fly Class 1 and it is perfectly possible to place highly or even win competitions using this more normal technique, simply because the phase contributing most to flight scores is that of high speed, not low speed. You should therefore practice and familiarise yourself with aerodynamic slow flight first.
- STALLED FLIGHT (“The Hang”): A model may (though not necessarily can) also be flown at an angle of attack that is way beyond the stalling angle of the wing. Rule 11.2.2.2. limits this angle to 60 degrees. This is stalled flight, because the aerodynamic lift produced by the aerofoil has broken down, the wing is fully stalled and is simply planing along on a cushion of air (a flat plate for a wing would be just as effective) with much of the lift being provided by the vertical component of propeller thrust. This flying attitude, as you might imagine, is very much more difficult to achieve than the attitudes for slow aerodynamic flight as it requires much practice and a careful adjustment of model balance. Nevertheless, ‘prop-hanging’ is the principal technique used by many of the top Class 1 fliers. Whilst the effect of wind is obviously less on a technique which itself has much less reliance on wing airspeed, the same considerations as described for BCD in Section 2.4 are generally relevant and should be applied.
Most models are capable of stalled flight, providing the correct longitudinal balance is obtainable without compromising fast run stability too much. The general technique to get a model into this attitude from the aerodynamic flight phase is to progressively reduce speed, whilst feeding in more and more up elevator and progressively increasing power to prevent height loss as the model slows down. It is easiest to do this in the wind-behind-the-model sector, since the model’s tail will most readily sink down here. If the model is capable of executing stable stalled flight, it will usually make the transition from aerodynamic to stalled flight fairly smoothly this way, and once this has been achieved, it is possible to maintain a very high angle of attack around the whole circle provided that the wind is neither too strong or too gusty. Practice is thereafter required to fly the model as close to the 60 degree limit as possible, since this angle will clearly provide the slowest speeds.
The stalled flight attitude represents something of a balance which has to be maintained by careful interplay between throttle and elevator. Too much disturbance of this balance either by external (ie: wind-related) factors or pilot-induced irregularities can produce a number of interesting effects! The obvious effect is simply that the model sinks down too far and ditches, terminating the flight. Although this is undesirable, forward and vertical speeds are often low enough to avoid any damage. The model may alternatively merely rotate over into aerodynamic flight, in which case stalled flight has to re-established all over again. It is also possible that the model may rotate the other way and flip right over onto its back! Whether or not the model can stay in the air once inverted, this will always cause termination, since Rule 7.4 requires continuous maintenance of forward motion, relative to the ground,throughout the entire flight.
The slow run system which probably contributes most to stalled flight is the line sweep, followed by the rudder and perhaps airbrakes. As mentioned before, the drag aspects of ailerons and flaps may also contribute, but these devices are usually much less significant in this context than when used during aerodynamic flight. Slats and slots are – probably – useless. Since this style of flight is unique in any area of aviation, either in full size or model practice, no data exists to explain the characteristics associated with it or to show how variation in the different parameters can affect performance. It’s a technique peculiar to Carrier. Although even the originators – the Americans – are occasionally critical of this obviously ‘non-scale’ practice in what is otherwise a very ‘scale’ event, the technique is with us for the foreseeable future and account therefore has to be taken of it.
10. The Landing
If aerodynamic flight is the technique used during the slow run, then the landing will also be executed under these conditions. The variations in landing style that are possible are therefore identical to those explained for BCD and the procedures described there apply.
Some pilots prefer to execute the slow run using stalled flight, but to revert to aerodynamic flight for the landing, since control response is undoubtedly better. Provided model landing speed is acceptably low, the normal BCD techniques will again apply, as above. If the slow run is carried out using stalled flight and this is then extended to the landing, matters are slightly different. Stalled flight is a careful balance between applied power, forward speed, elevator authority and model weight. Height is mainly controlled by power, with attitude, and therefore forward speed, mainly by elevator setting – effectively a reversal of the normal controls! Although it is possible to follow all the different landing approach paths described for BCD, stalled flight has in fact generated its own practices.
- The Constant Height & Speed Approach (ie: the ‘Creeper’) becomes more workable in Class 1 than in BCD. Stalled flight can be extremely slow and it is therefore possible to use the Creeper technique since there is much more time to adjust model position relative to the deck in the time between first sighting the carrier in your left hand peripheral vision and crashing into it or missing it completely
- The Power-Controlled Descending Approach. This is peculiar to stalled flight and has sufficient latitude in execution that its description really covers most of the other variations on the theme of stalled flight landings. The model may approach at a wide range of heights (say 3-12ft) and when the carrier’s stern comes into sight, power is gradually reduced so that the model descends towards the aiming point centred in the middle of the arrester wires. Forward speed is usually slow enough to have sufficient time for any necessary power and pitch adjustments. Because the model is stalled, there is little or no speed increase associated with the downward angled flight path (you cannot really call this a ‘dive’) and the landing is generally gentle no matter what the original approach height – the model essentially ‘flops’ into the wires in an extremely tail-down attitude, maximising its chances of picking up a wire. This sounds ideal, but, of course, it relies on being able to maintain the balance of forces that constitutes stalled flight and this only achieved with extensive practice.
Whether aerodynamic or stalled flight landings are undertaken, all other considerations, such as signals to the Contest Director, overshooting and post hook-up matters, are identical to those already described for BCD and reference must be made to them.