xxavier
  • Member for 5 years, 6 months
  • Last seen this week
  • Madrid, España
How to calculate the velocity gradient at the wall normal to the wall (Boundary layers)?
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In page 72 you'll find the value of µ at standard sea-level temperature...

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What does the statement painted on this P-51 mean?
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In my opinion, it's a reminder that 1) fuel should be 100-150 octane, and 2) when not available, a gasoline rich in aromatic hydrocarbons (i.e. high-octane) could be used in emergencies, following the ...

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I don't quite understand the bypass air
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Cold air accelerated backwards provides forward thrust by reaction. What really matters is the amount of mass accelerated backwards. Its temperature is not important... Concerning the 'percent of ...

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What aircraft could make non-stop transatlantic flights in 1958?
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There were regular transatlantic flights even before the 1950s. For example, in 1948, my father was among the passengers in a DC-4 flying the regular route from Madrid to Lima with FAMA, an ...

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Is there a way to calculate thrust without running experiments?
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For the case of an electric motor driving a propeller, you can get a rough approximation for the thrust t from the power p consumed by the motor when the plane is flying with a constant velocity v, ...

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What do the components of a shockwave's visual artefacts represent?
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What you see are changes in the refractive index of the air, caused by the different pressure and temperature at different places. Sometimes, with the right conditions, there may be zones of transient ...

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What procedures are followed for a planned landing in a field?
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First of all, I look for power or telephone lines. The wires are almost invisible against the ground, but poles and towers are more or less conspicuous. Second, the wind has to be right, and third, ...

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What is the purpose of having contra-rotating props on an aircraft?
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Apart from the reasons stated above, there is another important one, specially valid for the Tu-95. The turbines of that plane are very powerful, the most powerful ever built. In order to convert that ...

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Which 'pusher' propeller aircraft have been used in active military service?
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The German Do335 'Pfeil' was a twin-engined fighter of the forties. One engine driving a tractor prop at the front, and the other driving a pusher prop at the tail, with a long transmission shaft.

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Can an Autogyro with wings survive a rotor mechanical failure? Will it be safer?
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Sure those wings would help, but if the 'mechanical failure' of the rotor involved an important imbalance, such as the loss of a blade, the machine would be difficult to control, wings or no wings... ...

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What limits the lifespan of helicopters?
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Fatigue is a problem that limits, if not the life of the helicopter, at least the working life of some of its key elements, in particular of those subject to strong vibration and made from materials (...

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How can I calculate the force on the nose gear at landing?
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In order to calculate the force, you should start with an estimation of the angular momentum as the nose sinks and the wheel contacts the ground. That angular momentum am becomes zero as soon as the ...

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Do propellers have any lead/lag mechanism?
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I don't think props do (usually) have lead-lag hinges. Those lead-lag hinges are only necessary as a complement of the flapping articulations in fully articulated rotors, as in many helicopters, and ...

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What is the fuel burn rate for climb of a C-130J Hercules?
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A rough estimation: for a mass of 60000 kg, the energy needed for that (1000 ft = 305 m) altitude change will be 60000 x 9,8 x 305 = 179 MJ. Jet fuel has a heating value of 44 MJ/kg, and if we assume ...

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Is there a way for the helicopter rotor to get its power half by wind, half by engine?
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Most present-day gyros have a two-blade teetering rotor that has to be kept always under load, since it is the airflow associated with that load what keeps the rotor spinning and the blades rigid. If –...

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How does downwash affect angle of attack?
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Angle of attack AoA, aspect ratio A, and downwash deflection angle E, are linked by: sin E = 4 sin AoA/(2+A) Derivation here: Chris Waltham, Flight without Bernoulli https://booksc.org/book/45382205/...

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How can I estimate wind speed and direction in VFR?
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Flying circles and observing how the intended center of the orbit moves can give the pilot an idea of the wind speed & direction.

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Autorotation: Positive Pitch during descent phase possible?
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The angle of attack ALPHAr is the key magnitude in autorotation. The following images are from Gessow & Myers 'Aerodynamics of the Helicopter'. The angle of attack ALPHAr = PHI+THETA, PHI being ...

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Can an automatic gearbox improve engine transmission for an ultralight?
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The main point is to maximize the thrust that can be attained with the power available. Having a given power delivered by the engine at at given angular velocity, you should match that angular ...

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How can I calculate the maximum range of an aircraft descending with power (not gliding)?
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At a given airspeed, your plane (not only the wings, but the entire plane) will have an optimal L/D ratio. That's also the glide ratio. For example, if the best L/D is 10, your airplane, flying in a ...

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How does the Mi-26 tilt its rotor like this?
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It's less than 45 degrees, I think. Probably less than 30. There's nothing special about that. That helicopter is built with an important amount of forward cyclic. It's not the rotor head itself that ...

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How much of an airplane's forward energy is lost to lift?
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No energy is 'lost' to lift. All the energy delivered by the engine is spent, directly or indirectly, in accelerating air downwards in order to produce lift...

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How to take into account wind in aerodynamic forces balance?
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The falling object moves within the mass of air, and suffers no horizontal forces at all... For a ground observer, it drifts with the wind...

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What is lifting force of V-22 Osprey? Is any other than the two rotors?
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As in all turboprops, some thrust is derived from the turbine exhaust, but it's very little, compared with the big thrust of those enormous propellers...

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How Helicopters Change Attitude (Gyroscopic Precession or Thrust Vector Tilt)
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The 90º phase lag of a rotor has nothing to do with gyroscopes or precession, and is only due to resonance. A good explanation, by James Bennett, chief engineer of Cierva Autogiro Co. and a first-...

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How can a pilot deal with a magneto failure?
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If one magneto circuit fails, the engine keeps running, if only with one spark per cylinder, and there may be a very slight reduction of power. The only real risk is that the other circuit may fail ...

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What makes an airplane STOL?
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Those STOL (not VTOL) planes have wings with high-lift devices as large flaps and slats, that greatly increase the lift coefficient, thus allowing the plane to take off with relatively little airspeed....

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Do airplanes with fixed gear usually turn upside down during water landing?
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In theory, for small airplanes with a very low stall speed, and with the help of a kind headwind, you may slow the plane down so much that the impact with the water may be almost vertical. But that's ...

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I wonder if it's possible to make a "compressed air" turbine engine
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A turbojet with 'no ignition involved' is in principle possible, and it has been put into practice in the 1950s, in working prototypes of nuclear powered propulsion units. https://ntrs.nasa.gov/...

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Would a coaxial propeller with the second prop slower and larger improve speed?
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Contrarotating propellers may have a better efficiency than a single propeller, since the propwash is 'straightened out', the tangential component of the airflow being much reduced. Besides, and for ...

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