Mock Exam: Helicopter

1

What is the correct scoring formula for the 2026 Science Olympiad Helicopter event?

scoring formula easy

A. Flight Time + Log Bonus + 2-Blade Bonus
B. Flight Time × Log Bonus × 2-Blade Bonus
C. Flight Time × (Log Bonus + 2-Blade Bonus)
D. Flight Time / Log Bonus × 2-Blade Bonus

2

A team submits a flight log with some entries missing. What Log Bonus do they receive?

flight log bonus easy

A. 1.0× (same as no log)
B. 1.1× (partial log bonus)
C. 1.2× (full log bonus)
D. 1.3× (extra credit bonus)

3

A team's helicopter achieves a flight time of 60 seconds. They used two-bladed rotors and submitted a complete flight log. What is their final score?

scoring calculation medium

A. 60 × 1.2 = 72.0
B. 60 × 1.1 = 66.0
C. 60 × 1.2 × 1.1 = 79.2
D. 60 + 1.2 + 1.1 = 62.3

4

How many flights does each team receive during the 8-minute competition window, and which is scored?

event format easy

A. One flight attempt; it is automatically scored
B. Up to two flights; both are averaged for the final score
C. Up to two flights; only the best flight time is scored
D. Three flights; the median time is scored

5

Which of the following violations would result in a team being placed BELOW ALL legal devices in the final rankings?

rules and penalties medium

A. Submitting a flight log with only 9 test flights instead of 10
B. Using a four-bladed rotor instead of a two-bladed rotor
C. Using a commercially purchased propeller on the helicopter
D. Forgetting to include three team-selected parameters in the log

6

What is the primary structural function of the motor stick in a Science Olympiad helicopter?

motor stick easy

A. To generate aerodynamic lift during climb
B. To serve as the central spine connecting both rotors and supporting the rubber motor
C. To act as a counterweight that stabilizes the helicopter during descent
D. To store elastic potential energy when twisted

7

Why do most Science Olympiad helicopters use one fixed rotor and one free (spinning) rotor?

rotor configuration easy

A. To increase total rotor disc area for more lift
B. To allow counter-rotation that cancels torque and prevents the fuselage from spinning
C. To reduce total weight by eliminating one rotor shaft
D. Because the rules require one rotor to be fixed at all times

8

In a rotor blade, what is the structural difference between a spar and a rib?

blade structure medium

A. Spars run lengthwise along the blade; ribs run crosswise to maintain blade shape
B. Ribs run lengthwise along the blade; spars run crosswise for torsional stiffness
C. Spars are made of wire; ribs are made of balsa
D. Spars provide aerodynamic camber; ribs provide structural strength at the root

9

What is the purpose of the Measurement Box in the Science Olympiad Helicopter event?

measurement box easy

A. It is used to measure the rubber motor length before winding
B. It is a rectangular volume the helicopter must fit inside before launch to verify it meets size rules
C. It stores tools and repair supplies during the competition window
D. It measures the thrust produced by the rotor during static testing

10

A student bends a paper clip to form the rotor shaft but doesn't align it precisely. What is the most likely consequence during flight?

rotor shaft alignment medium

A. The rubber motor will break due to increased torque
B. The helicopter will fly faster and reach a higher altitude
C. The free rotor will wobble off-axis, causing vibration and reduced efficiency
D. The helicopter will gain extra flight time because of asymmetric spin patterns

11

A team is deciding whether to cover their rotor blades with Mylar. Which statement best describes the trade-off?

covering materials trade-off hard

A. Covering always improves flight time because lift increases more than drag increases
B. Covering is never beneficial because it always adds too much weight
C. Covering increases lift by completing the airfoil surface but also adds weight and drag; the net benefit depends on the specific design
D. Mylar covering is prohibited under Science Olympiad rules

12

Which factor most directly increases the lift generated by a helicopter rotor?

rotor aerodynamics medium

A. Increasing rotor RPM
B. Decreasing blade chord width
C. Reducing blade pitch angle to zero
D. Shortening blade radius by 20%

13

In the 2026 Science Olympiad Helicopter rules, what bonus does a team earn for using only two-bladed rotors on BOTH upper and lower rotors?

two-blade bonus easy

A. 1.0× (no bonus — two-bladed rotors are less efficient)
B. 1.1× multiplicative bonus added to the scoring formula
C. 1.2× bonus, same as a complete flight log
D. 2.0× bonus because two-bladed rotors are twice as hard to build

14

What does 'blade pitch' refer to in the context of rotor design?

blade pitch easy

A. The width (chord) of a rotor blade from leading to trailing edge
B. The angle the blade makes relative to its plane of rotation
C. The speed at which the rotor tip travels through the air
D. The vertical distance between upper and lower rotors on a coaxial helicopter

15

A builder adds 'washout' to their rotor blades. What does this mean, and why is it beneficial?

rotor washout medium

A. Washing the blades with solvent to reduce surface roughness and lower drag
B. Gradually reducing blade pitch from root to tip to prevent tip stall and improve rotor efficiency
C. Increasing chord width toward the blade tip to generate more lift at the outer radius
D. Adding Mylar covering near the blade root to improve camber where airspeed is lowest

16

Why did a 'Chinook' (tandem rotor) configuration earn special bonuses in the 2012 and 2018 Science Olympiad Helicopter events?

historical bonus structures medium

A. Tandem rotors are always more aerodynamically efficient than coaxial designs
B. Rules that year specifically rewarded the more complex tandem configuration as an incentive to explore advanced design
C. Tandem designs always fly longer because they have twice the rotor area of coaxial designs
D. Coaxial helicopters were banned those years due to safety concerns

17

What is the Figure of Merit (FM) for a rotor, and how does it compare between Science Olympiad-scale rotors and full-scale helicopter rotors?

figure of merit hard

A. FM = ideal power / actual power; Science Olympiad rotors achieve FM ≈ 0.8, similar to full-scale rotors
B. FM = actual power / ideal power; higher is better; Science Olympiad rotors typically exceed 0.9
C. FM = ideal power / actual power; Science Olympiad rotors have FM ≈ 0.3–0.6, much lower than full-scale due to low Reynolds number profile drag
D. FM does not apply to small-scale rotors because they do not generate true aerodynamic lift

18

A team builds two rotor blades but one is 0.3 grams heavier than the other. What is the most likely effect on flight performance?

blade balancing medium

A. No effect — small mass differences have negligible impact at Science Olympiad scales
B. The heavier blade will generate more lift, improving overall climb rate
C. The rotor will vibrate due to mass imbalance, wasting energy and potentially destabilizing the helicopter
D. The heavier blade will naturally rotate slower, automatically balancing rotor torque

19

According to Newton's Third Law, how does a helicopter rotor generate lift/thrust?

Newton's Third Law and thrust easy

A. The rotor creates a low-pressure zone above it, pulling the helicopter upward by suction
B. The rotor pushes air downward; the equal and opposite reaction force pushes the helicopter upward
C. The spinning rotor creates centrifugal force that counteracts gravity
D. The rotor blades deflect incoming horizontal airflow upward, creating an upward reaction force

20

Why do coaxial Science Olympiad helicopters use counter-rotating upper and lower rotors instead of two rotors spinning in the same direction?

torque and counter-rotation easy

A. Counter-rotation doubles the total lift by stacking airflows efficiently
B. Same-direction rotors would cause severe vibration; counter-rotation eliminates it completely
C. Counter-rotation cancels the equal and opposite torque reactions from each rotor, preventing the fuselage from spinning
D. Rules require counter-rotation to prevent collisions between rotor blades

21

Bernoulli's principle is most relevant to which type of rotor blade design in Science Olympiad helicopters?

Bernoulli's principle medium

A. Flat, untwisted blades with no camber at all
B. Cambered (curved cross-section) blades, where faster airflow over the upper surface creates lower pressure and net upward force
C. Very thin blades with high pitch angles, where air compressibility becomes significant
D. Four-bladed rotors, because more blades increase the Bernoulli pressure differential

22

Science Olympiad helicopters operate at Reynolds numbers of approximately 10,000–100,000. Why does this matter for aerodynamic performance?

Reynolds number medium

A. At these Reynolds numbers, airflow is always fully turbulent, which maximizes lift generation
B. At these Reynolds numbers, viscous drag is disproportionately large and conventional full-scale airfoil theories break down
C. Reynolds numbers below 100,000 indicate supersonic flow, requiring special blade profiles
D. These Reynolds numbers are identical to full-scale helicopters, so the same aerodynamic design principles apply directly

23

At the low Reynolds numbers typical of Science Olympiad helicopters, which type of drag dominates and what is the primary design implication?

induced vs profile drag hard

A. Induced drag dominates; designers should use shorter, wider chord blades
B. Wave drag dominates; designers must avoid transonic blade tip speeds
C. Profile drag (viscous skin friction) dominates; designers should minimize chord width and keep surfaces smooth
D. Interference drag dominates; rotors should be spaced as far apart as possible

24

During a typical Science Olympiad helicopter flight, what three phases occur and which phase consumes the most energy from the rubber motor?

flight phases and power medium

A. Launch, hover, crash — launch consumes the most power
B. Vertical climb, hover, descent — hover requires the most sustained power output
C. Vertical climb, hover/transition, descent — the powered vertical climb phase consumes the most energy
D. Wind-up, release, landing — wind-up stores power but does not consume it aerodynamically

25

At low Reynolds numbers, which rotor blade cross-section profile produces the best lift-to-drag ratio?

blade profile at low Re hard

A. Thick, symmetric NACA airfoil profile (like NACA 0012)
B. Thin, cambered plate profile
C. Thick, heavily cambered profile identical to full-scale helicopter rotor blades
D. Completely flat, zero-camber plate for minimum profile drag

26

Why does larger rotor disc area improve thrust efficiency at the same total power input?

disc loading and efficiency hard

A. Larger rotors spin faster, converting more rubber motor energy to kinetic energy
B. A larger disc accelerates more air mass per unit time to a smaller velocity increment, which requires less kinetic energy for the same thrust
C. Larger rotors automatically reduce Reynolds number, moving blades into a more favorable aerodynamic regime
D. Larger disc areas reduce induced drag to zero, converting all motor power directly to thrust

27

Which product should be used to lubricate rubber motors, and why should WD-40 be specifically avoided?

rubber motor lubrication easy

A. WD-40 is preferred because it penetrates deeply into the rubber; silicone products should be avoided
B. Silicone-based products (like ArmorAll) should be used; WD-40 is petroleum-based and degrades rubber over time
C. Petroleum jelly (Vaseline) is the only approved lubricant under Science Olympiad rules
D. No lubricant should be used because it reduces the friction needed to hold winds in the motor

28

What three factors primarily determine how much elastic potential energy can be stored in a rubber motor?

elastic energy storage easy

A. Rubber color, ambient temperature, and motor age
B. Rubber cross-section (width × thickness), motor length, and number of turns
C. Winding speed, gear ratio used, and ambient humidity
D. Rotor pitch, rotor diameter, and motor hook spacing

29

A team switches from 3mm-wide rubber to 6mm-wide rubber on the same helicopter without changing the rotor pitch. What is the most likely outcome?

rubber width and torque matching medium

A. The helicopter will fly longer because wider rubber stores more total turns
B. The helicopter's rotor may be over-driven (stall) because the wider rubber produces more torque than the rotor pitch can efficiently absorb
C. The wider rubber will make no difference to flight time; only rubber length matters
D. The motor will break immediately because 6mm rubber cannot be wound in a helicopter motor

30

What is 'stretch-winding' (backwinding) and why does it allow more energy to be stored in a rubber motor?

stretch-winding technique medium

A. Winding the motor in reverse direction to uncoil tangles; it does not increase energy storage
B. Stretching the rubber 4–5× its relaxed length while winding, packing more turns in and shifting the torque curve to store more energy
C. Attaching a spring to the motor to pre-tension it before winding; the spring adds additional elastic potential energy
D. Using a high gear-ratio winder to spin the motor faster; higher speed increases energy stored per turn

31

A team uses a winder with a 10:1 gear ratio. If they turn the crank handle 200 times, how many turns does the rubber motor receive?

winder gear ratio medium

A. 20 turns
B. 200 turns
C. 2,000 turns
D. 210 turns

32

Which description best matches the shape of the torque-vs-turns curve for a rubber motor wound from 0 to maximum capacity?

torque-vs-turns curve medium

A. Torque increases perfectly linearly from zero to maximum turns, then drops sharply to zero
B. Torque is constant throughout the winding because rubber elasticity is uniform
C. Torque rises slowly at first, increases steeply near maximum winds (peak energy), then drops off as the motor unwinds during flight
D. Torque starts high, decreases gradually as turns are added, creating a smooth downward slope to zero

33

How should a team prevent rubber motor failure (breakage) during high-turn winding at competition?

over-winding prevention hard

A. Wind as fast as possible to minimize the time the rubber spends under high stress
B. Use a torque meter or consult published max-turns calculators based on rubber dimensions to avoid exceeding turn capacity
C. Wet the rubber with water before winding to increase its elasticity
D. Only wind in one direction; never stretch-wind as it increases breaking risk

34

A team has two rubber motor options: (A) a shorter, thicker strand and (B) a longer, thinner strand. Both are wound to the same number of turns. Which configuration typically stores more total energy, assuming neither breaks?

rubber length and energy optimization hard

A. Option A — thicker rubber always stores more energy regardless of motor length
B. Option B — longer rubber can absorb more turns at lower torque per unit length, allowing more total energy before the breaking point is reached
C. Both options store exactly the same energy if wound to the same turn count
D. Neither stores more energy; total energy depends only on rubber mass, not its geometry

35

Why is balsa wood the preferred structural material for Science Olympiad helicopters?

balsa wood properties easy

A. It is waterproof and resistant to humidity, preventing warping during flight
B. It has exceptional strength-to-weight ratio, allowing builders to create light yet strong structures
C. Balsa is the only material approved by Science Olympiad rules for helicopter construction
D. Cost is the primary concern for student teams, and balsa is the cheapest available wood

36

Why is cyanoacrylate (CA) glue preferred over PVA (white glue) for Science Olympiad helicopter construction?

adhesives easy

A. CA glue is flexible when cured, preventing joint cracking during rough landings
B. CA glue is lightweight, sets fast, and achieves a precise bond without adding significant mass like PVA
C. PVA glue is explicitly prohibited by Science Olympiad rules for structural joints
D. CA glue is the only adhesive that can bond Mylar covering to balsa spars

37

A team needs balsa for the section of the motor stick immediately surrounding the motor hook, which experiences high stress during full winding. Which balsa density should they choose?

balsa density selection medium

A. The lightest available balsa (2–4 lb/ft³) to minimize helicopter weight
B. Medium or higher density balsa that can handle concentrated stress without cracking
C. It doesn't matter — all balsa densities handle motor hook stress equally well
D. Carbon fiber must replace balsa here, as balsa is too weak for any high-stress area

38

Compared to a simple single-stick motor stick, what is the primary advantage of a rolled hollow-tube motor stick?

motor stick designs medium

A. It is faster and easier to construct, saving valuable build time
B. It is the lightest and most structurally balanced design, with the internal rubber motor providing additional bracing
C. The hollow interior allows the rubber motor to unwind more efficiently by reducing air resistance
D. Hollow-tube designs are required to achieve the maximum rotor diameter allowed by the Measurement Box

39

Why are building jigs and blade templates particularly important when constructing rotor blades?

building jigs and templates medium

A. Jigs add structural reinforcement to the blades during high-speed flight
B. Jigs ensure blades are constructed with identical shape and pitch, critical for balanced counter-rotation and minimal vibration
C. Templates determine the maximum legal rotor diameter as specified by the Measurement Box
D. Jigs are used to measure blade weight to the nearest milligram for mass budget tracking

40

What is the correct launch technique for a Science Olympiad helicopter to minimize flight-to-flight variance?

launch technique easy

A. Grip the rotor blades and spin them by hand before releasing, to pre-start rotor RPM
B. Hold the helicopter body with the free rotor shaft vertical, then release smoothly without imparting any hand spin
C. Throw the helicopter gently upward at a 15° angle to convert launch velocity into additional climb altitude
D. Hold the rubber motor directly and release the body, allowing the motor to unwind freely without body contact

41

A competition gives each two-person team 8 minutes total. Why is pre-planning roles before the competition window begins critical for maximizing score?

competition time management easy

A. Rules require roles to be declared to the judge before the window opens
B. Pre-assigning who winds and who launches/times enables efficient parallel work, leaving maximum time for flight attempts
C. Both team members must wind simultaneously to achieve the high turn counts needed for competitive flights
D. Pre-planning roles eliminates the need to bring a flight log on competition day

42

What is the recommended winding sequence to prevent premature motor kinking?

winding procedure medium

A. Wind all turns at full stretch from the very start to maximize energy per turn
B. Wind the full target turn count straight (without stretching) to avoid any stress concentration
C. Wind approximately half the target turns straight first, then stretch-wind the remainder to distribute turns evenly
D. Only stretch-wind; never wind straight as it creates uneven torque distribution along the motor

43

A team's torque meter shows the motor has reached a value much higher than their established pre-flight target. What is the correct response?

torque meter use medium

A. Launch immediately to take advantage of the extra energy before any dissipation occurs
B. Carefully unwind some turns to bring the torque back to the target value before launching
C. Replace the rubber motor — any motor that reaches high torque is about to fail
D. Ignore the reading; torque meters are unreliable at Science Olympiad scales and should not affect decisions

44

A team is competing in a gymnasium with a significantly lower ceiling than their practice venue. How should they adjust their strategy?

venue adaptation winding strategy hard

A. Increase turn count to maximize climb energy so the helicopter reaches the ceiling faster
B. Reduce turn count or lower blade pitch to decrease climb rate, preventing ceiling strikes and preserving hover and descent time
C. Ceiling height is irrelevant — turn count should always be maximized regardless of venue
D. Switch to a four-bladed rotor which climbs more slowly and is better suited to low-ceiling venues

45

What are the three mandatory parameters that must be recorded in a Science Olympiad Helicopter flight log for every test flight?

required log parameters easy

A. Flight time, peak altitude, and drift distance from launch point
B. Flight time, number of motor turns before liftoff, and motor length before wind-up
C. Flight time, rubber motor mass, and estimated rotor RPM at launch
D. Number of turns, torque at launch, and ambient temperature at time of flight

46

What is the maximum Log Bonus a team can earn in 2026, and what does earning it require?

flight log bonus medium

A. 1.3× — requires 15 or more test flights with all parameters filled completely
B. 1.2× — requires a complete flight log with all 6 parameters (3 mandatory + 3 team-selected) recorded for at least 10 pre-competition test flights
C. 1.2× — requires only that a flight log is physically present at check-in, regardless of completeness
D. 1.1× is the maximum; a 1.2× log bonus does not exist in the 2026 rules

47

A team runs a test series varying only the turn count (200–400 turns in increments of 50) while keeping all other variables constant. What scientific principle does this demonstrate, and what are they looking for?

test plan design medium

A. Trial-and-error testing — they hope to accidentally discover the best configuration through repetition
B. Controlled variable experimentation — they isolate the effect of turn count on flight time to find the optimal wind count
C. Safety testing — they are checking at which turn count the rubber motor is likely to break
D. Regulatory compliance — Science Olympiad requires teams to test exactly this range before competition

48

A team uses a thrust jig during testing: the helicopter is secured vertically on a scale zeroed with the helicopter's weight, and the scale reads −18g when the rotor spins at launch wind count. What does this measurement tell them?

thrust jig static testing hard

A. The helicopter is 18g overweight and must lose mass before competition
B. The rotor is producing 18g-equivalent of thrust force, which can be compared against helicopter weight to assess hover and climb capability
C. The rubber motor is producing 18g of torque at this wind count
D. The scale reading is meaningless because aerodynamic thrust cannot be validly measured in gram units

49

What is the MOST critical item to verify first on the pre-competition checklist before entering the flight window?

pre-competition checklist easy

A. That the rubber motor is fully wound to maximum turns for immediate launch
B. That both helicopters physically fit inside the Measurement Box
C. That the winder crank has enough rotations remaining for two full wind-ups
D. That the flight log has exactly 10 flights with no blank parameter cells

50

A team's four-bladed helicopter consistently achieves 70-second flights. Switching to two-bladed rotors (earning the 1.1× bonus) is expected to reduce flight time to 60 seconds. Should they make the switch, assuming a complete flight log in both cases?

two-blade bonus break-even analysis medium

A. Yes — the 1.1× bonus always improves final score regardless of any flight time reduction
B. No — any reduction in raw flight time makes the two-blade switch a net loss
C. No — 4-blade score: 70 × 1.2 × 1.0 = 84.0; 2-blade score: 60 × 1.2 × 1.1 = 79.2; the four-bladed design scores higher
D. Yes — fewer blades reduce weight and rotor drag, which always outweighs any aerodynamic loss in lift

51

With 8 minutes available for two flight attempts, what is the optimal general strategy for a well-prepared team?

flight window strategy medium

A. Attempt both flights simultaneously to double the chances of a good result
B. Use the first 4 minutes to inspect and re-check the helicopter, then attempt both flights in the final 4 minutes
C. Attempt a conservative first flight early to secure a baseline score, then decide based on remaining time and helicopter condition whether to attempt a more aggressive second flight
D. Save both attempts for the last 2 minutes to benefit from watching other teams and adjusting strategy accordingly

52

During venue scouting, a team notices large HVAC vents blowing air across the competition floor at significant velocity. How should this affect their competition plan?

venue scouting and adaptation hard

A. No adjustment needed — HVAC airflow is uniform and will affect all competitors equally
B. They should launch directly into the HVAC headwind; horizontal airflow provides additional forward lift component
C. They should identify sheltered launch positions away from direct HVAC airflow and adjust launch direction to minimize horizontal drift that could end the flight prematurely
D. They should increase turn count by 50% to generate enough climb power to overcome the HVAC horizontal wind

53

A team wants to apply the iterative design philosophy to their helicopter program. Which approach best embodies this?

iterative design philosophy medium

A. Build one perfect helicopter using the best available materials and never modify it, to avoid introducing new variables
B. Document each design change alongside flight data so improvements are traceable and reproducible, treating each build as a data point in a systematic optimization process
C. Copy the previous year's winning team's design exactly for guaranteed competitive results
D. Make as many changes as possible simultaneously between test flights to cover more design space in less time

54

A builder is constructing a hollow rolled-tube motor stick. What technique is used to form the tube shape from flat balsa sheet?

hollow tube motor stick construction hard

A. Cutting the balsa into thin strips and laminating them in a spiral pattern using CA glue
B. Soaking the balsa sheet in hot water to increase flexibility, then drying it on a cylindrical form to hold the tube shape
C. Heating the balsa sheet with a heat gun and pressing it around a metal mandrel while hot
D. Scoring the balsa sheet with a knife at regular intervals and folding it into a triangular cross-section for rigidity

55

Using the torque equation τ = F × r, if a rotor blade exerts a force of 0.05 N at a distance of 0.15 m from the rotation axis, what is the torque produced?

torque calculation medium

A. 0.0033 N·m
B. 0.0075 N·m
C. 0.075 N·m
D. 3.0 N·m

56

Which of the following is NOT a correct definition of fluid dynamics terminology as applied to rotor aerodynamics?

fluid dynamics vocabulary medium

A. Angle of attack: the angle between the blade chord line and the direction of the incoming relative airflow
B. Stall: the condition where angle of attack exceeds the critical angle, causing flow separation and a sharp drop in lift
C. Camber: the curvature or asymmetry between the upper and lower surfaces of a blade cross-section
D. Aspect ratio: the ratio of rotor RPM to blade chord width

57

Why do teams build their Science Olympiad helicopter rotors as large as the Measurement Box permits?

disc loading and rotor diameter medium

A. Larger rotors spin faster, generating more kinetic energy per unit of rubber motor input
B. Larger disc area reduces disc loading, allowing the same thrust to be produced with less power
C. Larger rotors are heavier and lower the helicopter center of gravity, improving stability
D. Rules award bonus points based directly on rotor diameter

58

A rotor shaft bends slightly after a crash. No replacement paper clip is immediately available. What is the best rapid repair?

repair techniques medium

A. Carefully straighten the bent shaft with pliers, then verify the free rotor spins on-axis before the next flight
B. Remove the shaft entirely and test-fly with only one rotor
C. Pack CA glue over the bent section to stiffen it and prevent further bending
D. Replace the shaft with a wooden dowel of the same diameter

59

Why should teams review the competition's tie-breaking rules before entering the flight window?

tie-breaking rules medium

A. Tie-breaking rules must be declared to the judge before the window opens or forfeited
B. Understanding tie-breaking criteria allows teams to make strategic decisions (e.g., attempting a second flight) that could determine placement in close competitions
C. Tie-breaking rules change every flight attempt, requiring constant re-evaluation during the window
D. Tie-breaking only applies to the log bonus, not to flight time scores

60

A team's helicopter consistently drifts far from the launch point during every flight. What is the most likely root cause?

drift troubleshooting hard

A. The rubber motor is too long, causing excess turning momentum after landing
B. Upper and lower rotor torques are unequal; net residual torque causes the helicopter to yaw and precess horizontally
C. The helicopter is too heavy in the rear, pitching backward and translating rearward
D. The winding direction is reversed, causing the helicopter to spiral outward from launch

🚁 Helicopter Mock Exam