| IMAC 2009 Basic Sequence Narrative
By: BJamesJr-NorthEast IMAC Contest Coordinator
NOTES: There are a few things you want to remember before doing any IMAC sequence. The first thing is there is no aerobatic box. This has been replaced by the Airspace Control Score. This score is based on the flow of the sequence and by that I mean did you keep your altitudes relatively equal throughout unless needed otherwise and were the end and center maneuvers properly placed. I will address this in each maneuver. So always treat where you are standing as the “center”. Second is the sound score. Again this is based on overall sound of the sequence. The judges will be looking for things like prop rip and general loudness. Basically you want to keep the sound signature down and that means a good exhaust system (canisters) and a 3-blade prop as well as throttle management. Now that is one of the best ways to get a good sound score but with stock exhaust and 2 bladed props you can exercise great throttle management and still score well. And finally, the rudder is everything for wind correction. IMAC is judged on track, not the attitude (A properly wind corrected sequence will actually look quite ugly to someone that does not know the rules in effect), though the wings must remain level at all times. In a vertical maneuver it’s not uncommon to have rudder into the wind to keep the track going straight up (I’ve seen the nose 30 degrees to one side but the track be perfectly straight and that is actually the correct way to fly a wind corrected line) as well as pitch being a little low or high. A good thing to look for in a vertical, properly wind corrected line is the plane will seem to go uphill in a huge hurry, same thing with going downhill, (with a few exceptions) such as a Yak or almost anything with a round cowl, think aerodynamic braking. 3-bladed props can also add to the braking effect.
All maneuvers start and end with the plane level in all respects. It’s important to remember that the line you are flying between maneuvers is also judged so do not “quit” flying the sequence between maneuvers. Sometimes you will be flying from one end to the other so remember that you are being scored for this so keep the wings level and keep from losing or maintaining altitude.
IMAC flying is certainly a challenge and will certainly improve all other aspects of flying. For those of you into 3D, learning to fly IMAC will definitely make you a better 3D pilot. As a sport flier, you will improve your overall flying and if you were the type that would find yourself questioning flying in a given wind, then that will go away as well. Contests are not cancelled because of wind until it reaches 25 to 30 mph. This all depends on the given CD of the contest. In every case, there was always a poll of the pilots at the meeting before the contest and in all cases the vote was to fly, understandable because a lot of people travel a few hours to fly and want to fly. You will also get really good with the left stick in both power and rudder.
Figure 1 – 45 Degree up-line. Just before you get to center, pull up to a 45-degree line. Hold this line for a long enough distance to set yourself up for the next maneuver and then push to exit upright and level. You want to try to exit this maneuver at center. The next maneuver requires one half of a loop coming down so you will need some altitude. Also remember that a 45-degree line is actually quite steep. Your caller can help by using the Aresti and using the 45-degree line against the horizon. A 45-degree line at the ends will look very different from the center so be aware of that
Figure 2 – Split “S”. This is an end maneuver. Coming from the previous maneuver you will be flying from roughly the center to the start of this maneuver near the end of your airspace. Begin by executing ˝ roll to inverted and wings level, then executing an immediate pull to a one half loop. There should be no discernable line between the ˝ roll and pull. Though not really necessary, the key here is to exit right at the same altitude that you started the 45-degree up-line. This will help with your overall ACS score.
Figure 3 – Hammerhead. Begin this figure by applying full throttle and executing a gentle pull to a vertical up-line. Use the rudder to keep the plane tracking straight up. Once you have reached sufficient altitude, begin to decrease the power. Leave 3 or 4 clicks of power on, and just before the plane stops moving, apply full rudder and come back to idle. It is almost always easiest to hammer INTO the wind if there is a crosswind. If the wind is down the runway, hammering either left or right is OK. Once the plane starts to pivot, the throttle can be reduced to idle. One method of preventing the plane from wagging its tail after the pivot is to keep some rudder input after the pivot and slowly take it out as the plane goes down. Though a bit harder to do, another method is to come out of the rudder just as the nose starts to pivot downwards. Also do not let the wings come off level. If you plane is trimmed well and the radio mixes are proper, this is not likely to happen as your mixes will take care of it but at the same time certain mixes can create this problem, it all depends on what aileron you had to mix in with the rudder. Almost all planes need some kind of rudder/ aileron mix. At the bottom of the line, execute a gentle pull to a horizontal exit and increase the throttle. Try to make the entry radius and exit radius equal don’t execute a sharp pull at the bottom. You should now be flying back to the center.
Figure 4 – One Full Roll. Just before you get to center, start an aileron roll. You will not be judged on the rate of the roll – it can be as fast or as slow as you like. Typically, the faster you roll, the harder it is to stop it with the wings level. Give a little down elevator while you are inverted so that you don’t lose altitude, and stop the roll with your wings level. For the best score do not let the nose come off the line at any time during the roll (pitch or yaw), keep the roll rate exactly the same all the way through the maneuver and stop with the wings level.
Figure 5 - Teardrop. As you get to the end, pull a gentle radius to a 45-degree up-line. Fly this line a short distance and pull a 5/8th loop to a vertical down-line. Execute a ˝ roll on that down-line. Remember that roll must be centered on the line between the point where the down-line is established and your pull out to level flight. The loop can be as tight or as open as you want. If you find you are in too close, make the partial loop nice and tight and of you are out too far, make it nice and big to help get yourself back in. Remember that for the best scores, keep the loop constant no matter how big or little, keep the roll rate constant and make sure you do a 45-degree line (remember it’s going to look a little different since you are on the end) and the down-line is truly vertical using the rudder and elevator. Now fly towards the center for the next maneuver.
Figure 6 - Loop. This figure looks easy and is probably the first aerobatic maneuver you flew when learning to fly. It is, however, extremely difficult to fly well. Just before center, begin by increasing the throttle to full power, and start a gentle pull. The size of the loop is not judged, but the bigger the loop, the harder it is to make perfect. You need keep the radius consistent using the elevator and wind correct with rudder if necessary as you execute the first half of the loop. As you come over the top, you may need to keep a fair amount of power as this portion will be flown into the wind. You may even need to apply some down elevator across the top of the loop to keep it round. As the plane starts down the backside of the loop, start to decrease power smoothly to idle and use the elevator to keep the radius consistent. Finally, increase the power as you come back to horizontal flight. The loop should start and stop in the exact same place at the same altitude for the best possible score which will help ensure that it was round and not some other shape. You will quite often see judges take a pen or a finger and place it right on the point where the airplane started the first pull. This lets them see where the plane should end up at. Be sure when using the elevator, not to “Show” the judges any type of flat spot in the loops radius. Each discernable flat spot is one full point off your score.
Figure 7 - Sharks Tooth. Fly towards the end of the field, and increase power to full throttle. Execute a gentle pull to a vertical up-line. As before, use the rudder to maintain a nice vertical track. Execute a gentle pull across the top of the figure to an inverted 45-degree down-line coming back towards yourself and decrease the power to idle or close to idle. Hold down elevator to maintain a nice line (not too shallow!) and then complete a half roll to upright. Hold this line and then execute a gentle pull back to horizontal flight and increase the throttle. You will now be flying to the other end before starting the next maneuver so be sure to keep this line level in all respects as it can be quite long.
Figure 8 - Half Reverse Half Cuban 8. Just before getting to the end, begin by increasing the throttle to full power and execute a pull to a 45-degree up-line. On the up-line, execute a 1/2 roll to inverted, now flying the same distance as you did before the 1/2 roll pull 5/8th loop to level flight. In this maneuver be sure to center the 1/2 roll on the 45-degree line and be sure that the 45-degree line is actually 45 degrees, remember, you are now at the end so it will look different than in the center. As with the other loop elements, be sure to keep the radius smooth and the same all the way through.
Figure 9 - Vertical line with a ˝ roll. This is another end maneuver so after you complete the previous maneuver, fly all the way down to the other end keeping the line level in all respects. You also need to be plenty high for the final maneuver as a two turn spin will eat up a lot of airspace coming down. Don’t forget to center the ˝ roll on the vertical line. Pull 90 degrees to vertical, fly a given distance and perform a ˝ roll, fly the exact same distance as you did before you preformed the ˝ roll and push to level.
Figure 10 – Two turn positive spin. This maneuver is best viewed and judged at center. You are trying to time the stall to be right in front of where you are standing as this will help you and the judges see the stall and give you the best score. Most people zero this maneuver right here as the plane must stall and the way to tell is the nose and one wing will drop...
As you approach the center of the field at a high altitude, begin to reduce the throttle smoothly. As the plane slows, you will have to feed in up elevator to keep it from descending. This will gradually bring the nose up. Once the throttle has reached idle, you need to keep feeding in up elevator until the nose drops in a stall. You will also have to be keeping the line straight with rudder – particularly if there is any crosswind and your airspeed decreases. Don’t worry if the nose of the plane is ****ed 45 degrees before the stall – it is most important to keep the line straight! As the nose drops, feed in rudder in the same direction as the wing that is falling right rudder if the right wing is falling and left rudder if the left wing is falling. Once the spin begins, go to full rudder and full aileron in the same direction (you should already be at full up elevator). After 2 turns, neutralize all controls to stop the spin. If the nose is high, give down elevator to establish a vertical down-line. After the down-line has been established, execute a gentle pull to horizontal flight and increase the throttle. | |
01-05-2009, 01:24 PM
IMAC 2009 Basic Sequence Narrative 
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