Recent content by SCP

This is only correct if the system you are studying has a single degree of freedom. For a lumped-parameter system with multiple degrees of freedom, this expands into the more general matrix version quoted by @FEAnalyst: In the case of the more general distributed-parameter system, you get a...

I see why you're getting confused. You're thinking in terms of an external sign convention that defines the positive y-direction as up. However, the Fy vector is drawn pointing down. The vertical component of F is up. Your sign convention defines that as positive. However, the Fy vector is...

Whether Fy is positive or negative depends on your sign convention. In the free-body diagram, the component Fy is sketched directed downward, so a positive result indicates that the force component does, in fact, point downward. A negative result would indicate that the component Fy is...

Older aircraft with "conventional" flight instruments (referred to in aviation, somewhat pejoratively, as "steam gauges") use mechanical gyros. This is still fairly common in single-engine and light twin-engine aircraft -- although it is becoming less so. Low-end Electronic Flight Information...

That's correct. There is a distinction between the undamped natural frequency (##\omega _n##) and the damped natural frequency (##\omega _d##). In terms of language, when someone says "natural frequency", they usually mean ##\omega _n##. Damping is usually expressed in terms of the damping...

Resonance occurs when the input to a system occurs at a frequency that matches a natural frequency of the system. When this happens, the input continuously adds energy to the system, so oscillations get continuously larger. In a simplified mathematical model of an undamped system, the...

I think they show a lot of promise. They look good on paper and the ground test data seems to support the theory. But we're still pretty light on flight test data. That might work well enough for writing science fiction, realistic and plausible, but not exactly accurate. You'll certainly see...

Ok, so no induced drag. That makes more sense. Ok. I though you were trying to find the wake of the aircraft. I was actually thinking in terms of downwash, but that's not applicable if there's no lift being produced. For the wake of the prop, use the area of the prop disk (so your blade...

No, the SSME's can't get 450 seconds at sea level, even theoretically. The thrust of a rocket engine can be shown to be: $$T=\dot{m}V_{e}+\left ( P_{e}-P_{a} \right )A_{e}$$ where the ##e## subscript refers to the nozzle exit conditions, and the ##a## subscript refers to ambient/atmospheric...

You need to account for the characteristic area here. This area is probably the wing planform area, or it could be the wetted area, depending on how the drag coefficient was determined. I'm not sure where this comes from. I'm assuming this is the torque of the engine (that's how it appears to...

No. The weight (mass, actually) will influence the transient response (spool-up and spool-down time) and gyroscopic loads during rapid maneuvering. But steady-state thrust will be unaffected. The blade count is driven primarily by the need to carry power. The bigger (i.e. - more powerful)...

The error you're making here is equating force and work. They aren't the same. Think of propulsion as the airflow exerting a force on the aircraft and the aircraft exerting an equal and opposite force on the airflow. So far so good. But force is not work. In order to get work, we need to...

Hi msat. Propulsive efficiency is a measure of how much energy is transmitted to the aircraft versus how much is left behind in the airstream. You're right about changing up the massflow and the velocity, so run with that concept and see where it leads: Consider a high-massflow propulsion...

I'm not really sure I follow your post,but I think you're talking about gust alleviation. Gust alleviation is already in use on most (all?) fly-by-wire aircraft. It's based on a feedback control system that senses normal acceleration and identifies turbulence by comparing the measured...

Yes, this is correct, and what you've described is a simplified version of an airspeed indicator (which actually measures dynamic pressure, not airspeed) used in aircraft.