Direct drive means the propeller is bolted directly to the engine crankshaft with no gearing. Because there’s no gear train to change the speed, the propeller’s angular velocity matches the engine’s exactly. So if the engine is turning at, say, 2,600 rpm, the propeller is turning at about 2,600 rpm as well. In contrast, gear reduction would slow the propeller relative to the engine, and a setup that speeds the propeller up would require gearing not present in direct drive.

Dumping fuel is done to reduce the airplane’s weight to meet the maximum allowable landing weight. When a flight would otherwise arrive overweight for a safe landing—perhaps due to a diversion or unexpected extended flight—pilots may dump fuel to reach a lighter, allowable landing weight. This helps protect the landing gear, runway performance, and braking performance, and it’s done only under approved procedures with proper coordination and environmental considerations. Water and dirt contamination checks aren’t performed by dumping fuel; instead, fuel samples are taken from drain points or during maintenance to assess quality. Adjusting the fuel mixture isn’t accomplished by dumping fuel either; mixture control (or fuel metering) is managed by the engine systems. Clearing air pockets in the fuel system is handled through purging and priming procedures, not by dumping.

Spars are the wing’s main load‑bearing members—the long beams that run from the wing root to the tip and form the primary framework of the wing. They carry the bending loads produced by lift and transfer those forces into the fuselage at the wing root, working together with ribs and skin to create a rigid wing box. This is different from engine cylinders, which are part of the engine; ribs, which define the wing’s airfoil shape; or control surfaces, which are movable parts on the wing. The spars are the key elements that give the wing its strength and attach the wing to the aircraft structure.

Electrical power distribution is what the bus does. It acts as the central network that carries power from sources like generators and batteries to all the aircraft’s systems. By tying loads to a common distribution point, the bus lets each component—avionics, lights, flight controls, etc.—draw what it needs while protected by breakers and other safeguards that isolate faults and keep the rest powered. Modern aircraft use multiple buses (essential, main, nonessential) so critical systems stay energized even if some power sources drop offline. Storing energy is the job of energy storage devices, not the bus; monitoring temperatures is handled by sensors and avionics; routing fuel is a function of the fuel system, not the electrical distribution network.