Conditions and concepts
Use the supplied aircraft-specific mass limit and include all onboard/attached items. A learning calculation does not establish an actual aircraft limit. This original energy model assumes constant stated consumption and a specified reserve. Real battery endurance varies with loading, weather, condition and flight profile. Loading changes balance and handling; use the aircraft's actual center-of-gravity and loading limits rather than assuming total mass is the only constraint. Performance planning must consider the actual aircraft data, loading, battery condition and environment; one successful prior flight is not a universal capability guarantee.
Worked decisions
An original planning model gives a 20 lb maximum takeoff mass. The aircraft with battery weighs 14 lb. What payload mass remains within that supplied limit? Subtract the quantities on the same reference: 20 − 14 = 6 lb. Adding the values would combine the reference with the difference instead of measuring the requested separation. The supported result is 6 lb. A supplied learning model has120 Wh usable energy before reserve and reserves30 Wh. At a constant180 W draw, how many minutes can the remaining energy support? Available energy after reserve is 120−30=90 Wh. Dividing by180 W gives hours; multiplying by60 gives30 minutes. Using all energy would spend the required reserve. The supported result is 30 minutes. A payload stays under the mass limit but moves the center of gravity outside the aircraft's allowed range. Which issue remains? Loading changes balance and handling; use the aircraft's actual center-of-gravity and loading limits rather than assuming total mass is the only constraint. The supported result is The loading configuration is not acceptable. An aircraft completed a mission in calm conditions with a lighter payload. The new mission adds payload and headwind. What should be recalculated? Performance planning must consider the actual aircraft data, loading, battery condition and environment; one successful prior flight is not a universal capability guarantee. The supported result is Performance and energy margins for the new conditions.
A change that matters
An original planning model gives a 30 lb maximum takeoff mass. The aircraft with battery weighs 21 lb. What payload mass remains within that supplied limit? Subtract the quantities on the same reference: 30 − 21 = 9 lb. Adding the values would combine the reference with the difference instead of measuring the requested separation. Here choose 9 lb. A supplied learning model has100 Wh usable energy before reserve and reserves20 Wh. At a constant240 W draw, how many minutes can the remaining energy support? Available energy after reserve is 100−20=80 Wh. Dividing by240 W gives hours; multiplying by60 gives20 minutes. Using all energy would spend the required reserve. Here choose 20 minutes. A crew moves the same payload farther from the aircraft's center. Which effect should be reassessed? Loading changes balance and handling; use the aircraft's actual center-of-gravity and loading limits rather than assuming total mass is the only constraint. Here choose Balance and control characteristics. A battery shows normal charge percentage but has degraded capacity. What assumption is unsafe? Performance planning must consider the actual aircraft data, loading, battery condition and environment; one successful prior flight is not a universal capability guarantee. Here choose That displayed percentage guarantees the original endurance.
Transfer check and reasoning
A model has100 Wh and reserves20 Wh. At240 W, what modeled flight time remains? (100−20)/240 hours=one-third hour=20 minutes. This is the supplied idealized model, not guaranteed real endurance.
An original planning model gives a 20 lb maximum takeoff mass. The aircraft with battery weighs 14 lb. What payload mass remains within that supplied limit?
- The relevant case condition is: An original planning model gives a 20 lb maximum takeoff mass.
- Subtract the quantities on the same reference: 20 − 14 = 6 lb. Adding the values would combine the reference with the difference instead of measuring the requested separation.
- Therefore choose “6 lb”. The alternatives must be tested against that same stated condition; an unrelated document, unit or approval cannot supply a missing requirement.
Compare the other answer choices
The proposed choice “34 lb” does not follow from the given conditions. Subtract the quantities on the same reference: 20 − 14 = 6 lb. Adding the values would combine the reference with the difference instead of measuring the requested separation.
The proposed choice “20 lb” does not follow from the given conditions. Subtract the quantities on the same reference: 20 − 14 = 6 lb. Adding the values would combine the reference with the difference instead of measuring the requested separation.
The proposed choice “14 lb” does not follow from the given conditions. Subtract the quantities on the same reference: 20 − 14 = 6 lb. Adding the values would combine the reference with the difference instead of measuring the requested separation.
Try it, then explain it.
Complete a short set without looking at the example. After each answer, explain which evidence or rule supports your decision and why the alternatives do not fit.
Sources & authorship
Original Slope explanations and examples. References support the concepts; they are not the source of copied questions. Independent educator review is pending.
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