Humpty Bump. Cross-Box Bridge

Transcription

1 1ST U.S. R/C FLIGHT SCH OL 1/4 1/4 Humpty Bump Cross-Box Bridge 1/4 1/4 Tip: When diagnosing the type of corrections your airplane requires, esp. on uplines, first assess whether the deviation is slight, medium, or large? Next, input the corresponding small, med., or large correction. G-44

2 Basic Humpty Bumps Like the hammerhead, another fun and highly versatile maneuver is the humpty bump. The two primary humpty bumps, or humptys as they are often called, are the pull-pull-pull and pull-push-pull versions: Pull up to and maintain a perfect vertical upline the same way you set up a hammerhead, but do not reduce the power as every bit of power and speed will be needed to loop over the top of the humpty cleanly. Maintain the upline for a count of to set the tempo for placing rolls along the upline later on. Pull or push the elevator smoothly to initiate a loop over the top. Quickly neutralize the elevator the moment the airplane points straight down. Note that the reduced elevator effectiveness at such a slow airspeed atop a humpty will require a larger elevator input than is normally used to loop. The humpty is more pleasing to fly when the power is partially reduced, say, to 1/4, at the start of the downline thereby creating more time to later perform rolls on the downline. (Side note: While the airspeed on the downline probably won t exceed what it was at the start of the maneuver, it can seem to be flying faster straight down, and thus cause the pilot to subconsciously start pulling out of the downline early thereby diminishing the most dynamic feature of the maneuver, a perfect vertical line.) Pull out after maintaining the vertical downline for a count of to set the tempo for later placing rolls along the downline. G-45 KPTR: The ease of the loop over the top of a humpty will be a direct reflection on how well you flew the preceding upline.

3 Humpty Bump: P-factor Influence on Loop Over the Top The combination of slow airspeed, high power, and considerable pitch required to cleanly loop over the top of a humpty bump will produce considerable P-factor effect. (See Precision Aerobatics.) If P-factor is a left turning tendency on a pull (elevator), it stands to reason that P-factor would be a right turning tendency on a push. P-factor Left Turning Tendency Negative P-factor Right Turning Tendency. Pull-Right. Pull over the top: One has to anticipate needing right rudder pulling over the top of a humpty to counter the left turning tendency of P-factor. Unless a strong contrary crosswind was being corrected, the P-factor correction over the top will be an increase of the right rudder already applied to counter slipstream along the upline. Pull Push The amount of right rudder required to track straight over the top will be determined in practice: Steadily increase your right rudder input, say, 1/4, as you initiate the pull over the top, then target different amounts until you find what works best. In a positive pitch attitude (pull) the right side propeller blade bites more air and tends to thrust the nose to the left (requiring a Right rudder correction). In a negative pitch attitude (push), the left side propeller blade bites more air and tends to thrust the nose to the right (requiring a Left correction). P-factor rudder correction summary: Pull-Right. - Push-Left.. Push-Left. Determining the direction to apply the rudder is based on which way you go with the elevator (not how you view the plane). Push over the top: Both gyroscopic precession and slipstream will resist the right turning tendency of negative P-factor when pushing over the top of a humpty. It is therefore wise to perform the first few pushes over the top without any rudder in order to watch and learn how much rudder will, or will not, be needed in subsequent attempts. Side note: After the warmup, an advanced aerobatic pilot will then lead with the rudder input that experience has shown him will most likely be needed, rather than rely solely on watching the plane. He will, however, keep his input small, so that just in case it has to be taken out or switched, he can do so without it being obvious. KPTR: In less than strong crosswinds, anticipate needing significant right rudder pulling over the top of a humpty, or some left when pushing. G-46

4 Classic Humpty Bump Turnaround w/balanced Vertical Performing a half roll on either the up or downline of a pull-pull-pull or pull-push-pull humpty bump will reverse the course making these classic advanced level turnarounds. one two roll one Humpty w/half roll on the downline: After looping over the top, simultaneously reduce power and start gradually taking out the P-factor rudder correction to maintain a perfect vertical downline. Note: Neutralizing the rudder all at once will tend to cause the tail to pendulum, and the plane to deviate from vertical. However, any rudder will have to be completely neutralized before initiating the half roll for the roll to remain axial. The half roll should be centered along the downline by holding the slower upper section for a count of one two, and the faster lower section for a count of one before pulling out. Humpty w/half roll on the upline: Set the vertical for a count of one, quickly perform the half roll, and then maintain the upline for a count of one two before pulling over the top. Note: Should the plane start to torque (roll) a bit to the left looping at such a slow speed, correct with a little right aileron. Reduce power after looping over the top and maintain the downline for a count of before pulling out (near the altitude the maneuver was started at although that is technically not required). one roll one two G-47 KPTR: Maintaining an even tempo facilitates a routine humpty and therefore your ability to think ahead of the plane.

5 1ST U.S.R/C FLIGHT SCH OL AWAY Humpty Bump Humpty Bump Small Wind Corrector Turnaround A version of the pull-pull-pull humpty bump turnaround involves performing s on the up and downlines to reposition the airplane further away or closer to the runway s extended centerline. The most common application of this version of the humpty is as a small (crosswind) wind corrector to reposition the airplane a bit further upwind. Wind one two roll one Right one roll one two Left Note: Initially concentrate your humpty bump wind corrector at one end of the field until you gain confidence judging the directions to perform the s. The on the upline has to be applied a certain direction for the pull over the top to be into the wind, and the on the downline then has to be applied the opposite direction to effect the turnaround. A simple technique for judging the on the upline is to input the roll in the direction that you intend to loop over the top (into the wind). In this example, that will be to your left. The on the downline will then be the opposite direction, right. Note that, along with some pre-flight planning, the key to correctly judging both rolls is affording yourself time to think by holding each vertical for a count before rolling: When able, center the s along the vertical lines by holding the faster lower sections for a count of one, and the slower upper sections for a count of one two. R L KPTR: on the upline in the direction that you want the airplane to go over the top. G-48

6 1ST U.S. R/C FLIGHT SCH OL Humpty Bump Small Wind Corrector Summary A good vertical foundation, tempo, and knowhow all come together in the humpty bump to make the intricate appear easy which is what truly good pilots do! Wind 1. Smoothly but quickly set the upline for a count of one, in the direction that you want the airplane to go over the top, and then maintain the upline for a count of one two. 2. Simultaneously pull over the top and increase right rudder. Upon completing the loop, simultaneously reduce power and start gradually taking out the rudder. 3. Maintain the upper section of the downline for a count of one two, the opposite direction of the first roll, and then maintain the remaining downline for a count of one. 4. Smoothly pull out and advance the throttle to the position appropriate for the next maneuver. One has the option to perform s on one or both of the verticals, as well as push over the top, and/or even push out at the bottom. Although, taking the humpty bump to that level will require solid planning with your stick model beforehand. Note: If altitude continually forces you to pull out immediately after the roll on the downline, adding extra counts to the upline before and after the roll will help you achieve more altitude: Set the upline, one two, roll, one two three. Pull over the top, one two, roll, one. Pull out. one roll one two two three Left one two roll one Right G-49 KPTR: Increase your count along the upline to alleviate rushing the downline.

7 Cross-box Bridge Major Wind Corrector: Cap Off Inverted When a significant repositioning of the airplane is required away or closer in to the runway s extended centerline, a cross-box bridge (perpendicular to the runway) is one of the more efficient ways that advanced pilots reposition. Flown (and judged) as two separate maneuvers, this version of a bridge is essentially a pull-pull-pull wind corrector humpty with an inverted line of some length flown at the top of the loop. one two Roll one Right Cross-box bridge (first part): Perform the first part of a bridge the same as a (crosswind) wind corrector humpty, with the centered along the upline and rolling in the direction that you want to fly across the aerobatic box. Simultaneously pull into the ( ) loop and increase right rudder. Cap off inverted at the top of the loop with forward elevator. Hold altitude (push) for the required distance, and gradually take out the right rudder as the airspeed increases. (Second part): Pull to the vertical downline and reduce power. Center the along the downline and roll in the opposite direction of the first roll. Wind Overhead view Performance Zone (Aerobatic Box) Parallel Cross-box one Roll one two Left KPTR: Fly a cross-box bridge as a wind corrector humpty bump with a line at the top. G-50

8 Cross-box Bridge Major Wind Corrector: Cap Off Upright Another version of a bridge is essentially a pull-push-pull wind corrector humpty with an upright line of some length flown at the top. Wind (First part): on the upline to position the plane for a push to level flight in the direction that you want to fly across the box (into the wind typically). one two roll one Left Atop the upline, simultaneously push into a outside loop and apply some left rudder to correct for negative P-factor. Cap off upright at the top of the loop with a little up elevator to hold altitude, and smoothly take out the rudder. Anticipate and look for right rudder to then be needed to counter the effects of slipstream during slow flight. A common fault atop bridges is allowing the plane to sag a bit after the loop and then reacting with elevator. Realizing that the airplane will be quite slow at that point, the advanced pilot inputs his push or pull immediately after the loop before the plane drops anticipating that it would. The amount will have to be determined in practice by committing to different inputs until finding and staying with what works best. Note: At the advanced level timing and rhythm become as important as visual reference. Since the control amounts required to do the job will depend on the airspeed, to be consistent, the airspeed needs to be similar at any given point in a maneuver each time it is performed by using the same power settings and maintaining the same even tempo counting along your lines. (A varying tempo is often the reason why flyers who don t feel they are doing anything different frequently experience different outcomes!) one roll one two Right (Second part): Resume the push to the vertical downline and reduce power. Center the along the downline, and roll in the opposite direction of the first roll. Pull Pull G-51 KPTR: Prior to bridging a line at the top, anticipate whether you want to pull to inverted, or push to upright.