Aer­o­bat­ics Made Easy

Add some spice to your de­par­ture THIS MA­NEU­VER IS EX­CIT­ING BOTH TO WATCH AND TO PER­FORM, BUT IT IS ALSO DE­MAND­ING ON YOUR FLIGHT SKILLS.

Electric Flight - - CONTENTS - By John Glezel­lis

Take­off with a 1 1/2 Pos­i­tive Snap Roll

If you’re as­pir­ing to be­come a bet­ter aer­o­batic pi­lot, you are, no doubt, con­stantly search­ing to add ex­cite­ment and va­ri­ety to your fly­ing. Af­ter all, the best aer­o­batic pilots are skilled at com­bin­ing cer­tain el­e­ments from one ma­neu­ver with el­e­ments from an­other. This month, I am go­ing to com­bine the snap roll with a take­off, so you can get at­ten­tion fo­cused on your flight right from the start. Be­fore we get into a deep dis­cus­sion about this eye-catch­ing aer­o­batic move, how­ever, we will take a look at your air­craft and how it is set up re­gard­ing dual rates and ex­po­nen­tial set­tings. Now, let’s get down to busi­ness.

FIRST THINGS FIRST

Many aer­o­batic air­planes to­day are ad­ver­tised as be­ing “3D ca­pa­ble,” and they have very large con­trol sur­faces so that they can per­form ma­neu­vers while in a stalled con­di­tion. Hav­ing large con­trol sur­faces and a lot of con­trol sur­face de­flec­tion, how­ever, are not needed for any ma­neu­ver that isn’t con­sid­ered 3D, and with re­spect to this month’s ma­neu­ver, a lot of con­trol de­flec­tion is not a good thing. The goal is to per­form a pre­cise 1 1/2 pos­i­tive snap on take­off—nice, crisp, and clean.

I pre­fer to use flight modes, with my dual and/or triple rates on one switch. This means that my aileron, el­e­va­tor, and rud­der rates are on one switch. To per­form the combo ma­neu­ver of the month, I pre­fer to use two flight modes. On my low­est rate, I have about 15 de­grees of aileron, 12 de­grees of el­e­va­tor, and 35 de­grees of rud­der de­flec­tion, with 20, 25, and 50% ex­po­nen­tial, re­spec­tively. On my sec­ond rate, I have about 30 de­grees of aileron, 25 de­grees of el­e­va­tor, and 32 de­grees of rud­der de­flec­tion, with 45% ex­po­nen­tial on all these sur­faces. Keep in mind that val­ues dif­fer from air­plane to air­plane.

When I per­form any take­off and land­ing, I am al­ways on my low-rate set­tings. When I per­form a stunt like a snap roll only feet from the ground, I switch to my mid-rate set­tings right be­fore the snap roll and switch back to my low-rate set­ting when the snap roll is com­pleted. While ev­ery­one has dif­fer­ent per­sonal pref­er­ences, this is the setup that has worked best for me as I do not want my air­craft to be sen­si­tive while fly­ing on low rates. No mat­ter what size air­craft you are fly­ing, whether it is a small park flier or a gi­ant-scale one, al­ways take ad­van­tage of flight modes and ad­just each rate as needed to cater to your liking. For ex­am­ple, once you’re fly­ing, if you move the aileron stick to its max­i­mum and the roll rate of the air­craft is slow, then in­crease the dual rate per­cent­age for that given rate. Sim­i­larly, if you feel that the air­plane re­sponds too quickly around neu­tral but the end­point value is great (the dual-rate value), then in­crease the ex­po­nen­tial per­cent­age you are us­ing. Do this test for all your con­trol sur­faces.

OVERVIEW

Be­fore at­tempt­ing the 1 1/2 pos­i­tive snap on take­off, you should be pro­fi­cient with per­form­ing pos­i­tive snap rolls in gen­eral. When you ex­e­cute this move, you must be in com­plete con­trol and exit the ma­neu­ver at a safe al­ti­tude. Do not drop al­ti­tude through­out the snap roll as this can be fa­tal when you’re only feet from the ground!

De­pend­ing on the power-to-weight ra­tio of your air­craft, your throt­tle per­cent­age may dif­fer slightly. On most of my mod­els, I pre­fer to ap­ply al­most max­i­mum power through­out the take­off roll and then de­crease power slightly once the air­plane breaks ground. I then pitch the air­plane up slightly by pulling back on the el­e­va­tor con­trol stick and ap­ply­ing the samedi­rec­tion rud­der and aileron. I’ll re­lease el­e­va­tor to un­load the air­plane and en­sure that it does not drop any al­ti­tude through the ro­ta­tion. Then, once in­verted and af­ter 1 1/2 snaps have been per­formed, I’ll re­lease aileron and rud­der in­put and ap­ply a touch of down-el­e­va­tor to sus­tain level in­verted flight. While this may sound

sim­ple, there are a lot of dif­fer­ent el­e­ments that need to be per­fected.

BY THE NUM­BERS

Let’s di­vide the ma­neu­ver into four steps. In this ex­am­ple, we will take off from left to right. Al­ways take off into the wind. If there’s a strong cross­wind, take off in a di­rec­tion that is the most fa­vor­able.

Step 1. While on low rates, add about 80% throt­tle and ap­ply rud­der as needed to keep the air­plane straight down the run­way. With tail­drag­gers, you’ll need to hold some up-el­e­va­tor and slowly re­lease el­e­va­tor in­put as the air­plane is near­ing the liftoff speed. Then, pull back ever so slightly on the el­e­va­tor stick un­til the air­plane be­comes air­borne.

Step 2. Once the air­plane is about 15 feet above the ground, flip to your mid-rate set­ting and cut back slightly on power if the air­plane’s speed is too fast. Pull back slightly on el­e­va­tor, and ap­ply the same-di­rec­tion aileron and rud­der to ini­ti­ate the snap roll. In this case, we will per­form the snap roll to the left, so we will need left aileron and left rud­der. Some­times, peo­ple are con­fused by the con­trol in­puts needed in per­form­ing snap rolls. When per­form­ing a pos­i­tive snap roll, up-el­e­va­tor is needed along with aileron and rud­der in­puts in the same di­rec­tion. When per­form­ing a neg­a­tive snap roll, down-el­e­va­tor is re­quired along with op­po­site di­rec­tions of rud­der and aileron in­put. It is crit­i­cal to time this por­tion of the ma­neu­ver so that the air­plane will pre­cisely ex­e­cute ex­actly 1 1/2 ro­ta­tions, caus­ing the model ex­its the ma­neu­ver in­verted.

Step 3. Through­out the 1 1/2 ro­ta­tion, ap­ply throt­tle (if needed) to keep the air­speed up. Once the air­plane nears the 1 1/2 ro­ta­tion point, you’ll need to neu­tral­ize aileron and rud­der so that the air­plane stops the ro­ta­tion pre­cisely where de­sired. This will take prac­tice and some time to per­fect, so al­ti­tude and fa­mil­iar­ity are key. Af­ter all, this ma­neu­ver should only be done on take­off if you are con­fi­dent in your abil­ity to ex­e­cute snap rolls pre­cisely on de­mand.

Step 4. Since the 1 1/2 pos­i­tive snap rolls have just been per­formed, you will have to ap­ply down-el­e­va­tor, as needed, to sus­tain your al­ti­tude. Once you are fa­mil­iar with how to per­form this ma­neu­ver, you can then pull the throt­tle back to lower the air­speed slightly and de­scend so that you are just inches off the ground while in­verted. Of course, this is in a per­fect world with no wind present. If a cross­wind ex­ists, I rec­om­mend that you per­form the snap roll into the wind. For ex­am­ple, if we are tak­ing off from left to right and there is a strong wind blow­ing in, I would snap to the left so that the air­plane snaps away from you. Heavy winds may cause the air­plane to drift through­out the snap.

Now you have the keys to per­form the 1 1/2 pos­i­tive snap rolls on take­off with piz­zazz. This ma­neu­ver is ex­cit­ing both to watch and to per­form, but it is also de­mand­ing on your flight skills, so do not at­tempt it un­til you are com­fort­able in ex­e­cut­ing snap rolls with­out any loss in al­ti­tude. Un­til next time, safe fly­ing and al­ways re­mem­ber to have fun.

Enter and take off into the wind.

Snap rolls are ex­cit­ing ma­neu­vers. When you add them to your take­off and ex­e­cute them at a low al­ti­tude, the im­pact is even more in­tense.

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