RPC sUAS Loading and Performance 3 — Questions and Answers
Question 1: What happens to an sUAS's center of gravity when a heavy battery is moved rearward from its standard mounting position?
- CG shifts forward, improving climb performance
- CG shifts aft, potentially causing pitch-up instability (Correct answer)
- CG remains unchanged because the total weight is the same
- The sUAS becomes more stable due to increased tail-heaviness
Correct answer: CG shifts aft, potentially causing pitch-up instability
Moving heavy components aft shifts the CG rearward, creating a nose-up pitch tendency and reducing pitch stability and control responsiveness.
Question 2: A remote pilot plans to fly an sUAS at a site with a field elevation of 5,500 ft MSL on a hot afternoon (temperature 95°F). Compared to sea-level standard day operations, the pilot should expect:
- Identical performance since multirotors are unaffected by altitude
- Significantly reduced motor efficiency and shorter flight times (Correct answer)
- Improved lift due to reduced air resistance at altitude
- Faster top speed because of lower aerodynamic drag
Correct answer: Significantly reduced motor efficiency and shorter flight times
High elevation combined with high temperature dramatically increases density altitude, reducing air density and motor efficiency, resulting in shortened flight times and degraded performance.
Question 3: When calculating weight and balance for an sUAS, 'useful load' is defined as:
- The weight of the airframe structure only
- The total weight minus the battery weight
- The difference between maximum gross weight and basic empty weight (Correct answer)
- The payload weight plus fuel weight
Correct answer: The difference between maximum gross weight and basic empty weight
Useful load is the difference between maximum allowable gross weight and the basic empty weight, representing all weight available for payload, batteries, and accessories.
Question 4: An sUAS with a rated maximum gross weight is operated at exactly that limit. How will any unexpected payload addition during flight (such as ice accumulation) affect the aircraft?
- No effect; the rated limit accounts for such variations
- The aircraft will exceed its structural and power limits, risking loss of control (Correct answer)
- Performance improves because added weight stabilizes the platform
- Ice accumulation only affects fixed-wing aircraft, not multirotors
Correct answer: The aircraft will exceed its structural and power limits, risking loss of control
Operating at the maximum gross weight leaves no margin, so any additional weight from ice, moisture, or unexpected cargo can exceed structural or power limits and cause a loss of control.
Question 5: Which operational scenario would result in the GREATEST reduction in sUAS hovering endurance?
- Flying at sea level, standard temperature, no payload
- Flying at sea level, standard temperature, with maximum payload
- Flying at high density altitude with no payload
- Flying at high density altitude with maximum payload (Correct answer)
Correct answer: Flying at high density altitude with maximum payload
High density altitude reduces rotor efficiency while maximum payload increases power demand—the combination produces the greatest reduction in hovering endurance.
Question 6: A remote pilot plans to conduct aerial photography with a 3-lb sUAS carrying a 0.8-lb camera. The battery weighs 0.4 lbs. If the airframe alone weighs 1.8 lbs, does this configuration exceed the manufacturer's 3-lb maximum?
- No, the total weight is exactly 3.0 lbs
- Yes, the total weight is 3.0 lbs plus the camera, so 3.8 lbs
- Yes, the total weight is 3.0 lbs
- No, because the battery is not counted toward gross weight (Correct answer)
Correct answer: No, because the battery is not counted toward gross weight
Wait—total weight = airframe (1.8) + battery (0.4) + camera (0.8) = 3.0 lbs, which equals but does not exceed the 3-lb maximum, so this configuration is at the limit.
Question 7: What effect does operating an sUAS significantly below its maximum gross weight have on performance?
- Reduced stability because CG is too high
- Improved endurance and agility with greater performance margins (Correct answer)
- Increased risk of structural failure due to unbalanced loading
- No measurable effect; performance is fixed by motor specifications
Correct answer: Improved endurance and agility with greater performance margins
Operating below maximum gross weight reduces motor load, extending battery life, improving climb rates, and providing greater performance margins.
RPC sUAS Loading and Performance 3
What happens to an sUAS's center of gravity when a heavy battery is moved rearward from its standard mounting position?