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Frequently Asked Questions (FAQ's) on principle of flights

Continue to see more FAQs on Principles of Flight.



You can fine more information on VOR in this book "Flight Training Handbook", U.S. D.O.T.,1980 ed.:For many years, the VOR has been the basic radio aid to navigation.Transmitting frequencies of omnirange stations are in the VHF (very high frequency) band between 108 and 118 MHz. The word "omni" means all, and an omnirange is a VHF radio station that projects radials in all directions (360 degrees) from the station, like spokes from the hub of a wheel. Each of these "spokes," or radials, is denoted by the outbound direction of the"spoke". A radial is defined as "a line of magnetic bearing extending from an omnidirectional range (VOR)." however, due to the features of VOR receivers, it is possible to fly either to or from omniranges in any direction.


FAQ on Ramjet

Contact NASA's Dryden test flight center which you can reach through several clicks from http://www.nasa.gov 


FAQ on rotating anemometers conversions

For rotating anemometers conversions then,
1. Measure the distance from the center of the rotating cup to the axis of rotation in inches and call it R.
2. Multiply R by 1/12 to get it into feet.
3. Find the number of revolutions the cup makes in a second (we  would suggest you count the number of revolutions for 30 seconds and then divide the number of revolutions you get by 30--this will give you an average value). call that number w. It will have units of revolutions per second.
4. Multiply w by 2 pi (6.283053). This will convert the result to Radians per second since 2 pi radians = 1 revolution.
5. Multiply the result of step 2 with the result of step 4. The number you get will be the wind speed in feet per second
6. Multiply the number you get in step 5 by (3600/5280) to convert it to miles per hour.


FAQ on flight simulation/control tower

The ALLSTAR Network doesn't hold software about flight simulation/control tower. Patricia 'Pat' Ryan, director of the teacher resource center located at Embry-Riddle Aeronautical University in Daytona, FL has tied several aircraft simulators,MS flight simulator along with an ATC program to create a dynamic interactive learning experience. she can be contacted at:   
Embry-Riddle Aeronautical university
600 S. Clyde Morris Blvd.
Daytona Beach, FL 32114-3900
Tel.: 904.226.6499
Email: ryanp@hobbes.db.erau.edu
You can contact her regarding the flight simulation/control tower.


FAQ about Black box of Airplane

The "black boxes" found on aircraft that are used as data recorders are typically manufactured from stainless steel. The boxes are no longer blacks but painted high visibility orange or red to aid in their recovery in the event of an accident.


FAQ on how does a propeller plane gain speed down the runway ?

The propeller provides thrust (the force required to move the plane forward)
just like a jet does by moving air+fuel through its jet engine. The propeller thrust depends on the number of blades, the angle of the blades, the surface area of the blades among other things. The thrust generated by the propeller can be related to the torque (moment required to rotate the propeller). The torque of the propeller can be related to the horsepower generated by the engine of the plane. Thus once the engine of the plane kicks in, it provides the torque required to rotate the propeller. The propeller in turn generates the thrust required to move the plane forward.

Once the thrust force is bigger than the drag force (which retards the airplane's motion), then by Newton's third law (thrust-drag=mass of plane times the plane's acceleration) then the plane accelerates down the runway.


FAQ on information on oleo struts.

     The oleo strut was patented in 1915 as a recoil device for large cannons. The oleo combines a spring effect using compressed air with a damping effect using a piston which forces oil through a small hole or rifice. For max. efficiency, many oleos have a mechanism for varying the size of the orifice as the oleo compresses (metered orifice--see our hydraulics section on Level 3 ). When uses as a shock-strut, the oleo itself must provide the full required amount of wheel deflection, which can lengthen the total landing gear height. Also, the oleo strut must be strong enough to handle the lateral and braking loads of the wheels. To repair or replace the strut, the entire wheel assembly must be removed because it is attached to the bottom of the strut. This material is from a book Aircraft 1992. 


FAQ about laser guided propulsion

You might get information on regular NASA site at http://www.nasa.gov   and pose the question to their webmasters. They may be able to get that information for you. Also, take a look at the following site-- http://www.islandone.org/Propulsion/   you might find more information.


FAQ to reduce cavitation effects

To reduce cavitation effects:
The effects of cavitation have been minimized by employing surge tanks,
relief valves and (in water conduit systems) burst plates. Other ways to reduce cavitation include:
1.reducing the fluid's velocity, thus increasing fluid pressure
2.increasing the absolute pressure of the system
3.increasing the pressure head of the suction pumps
4.decreasing sharp bends in the hydraulic system
5.decreasing abrupt changes in tubing cross-section
6.controlling the temperature and vapor pressure of the system.


FAQ to determine the  upper and lower coordinates with wing airfoil number as long as you know the chord line length?(for ex. 12009)

From the book Airplane Aerodynamics, by Dommasch, Sherby and Donnally, Pitman
Press, 1967, pg 147:
The NACA 4-digit airfoils mean the following: The first digit expresses the camber in percent chord, the second the location of the maximum camber point in tenths of chord, and the last two the thickness in percent chord. Thus 4412 has a maximum camber of 4% of chord located at 40% chord back from the leading edge and is 12% thick, while 0006 is a symmetrical section of 6% thickness. The NACA 5 digit series airfoil means the following:
the first digit designates the approximate camber in percent chord, the second indicates twice the position of the maximum camber in tenths chord, the third (either 0 or 1) distinguishes the type of mean-camber line, and the last two gives the thickness in percent chord. Thus 23012 airfoil has a maximum camber of about 2% of the chord located at 15% of the chord from the leading edge (3
tenths divided by 2) and is 12% thick. If your airfoil holds true to NACA form, 12009 means a maximum camber of 1% chord located at 10% of the chord from the leading edge and is 9% thick.
There are formulas that define all the stations of the airfoil section from these digits and you can probably find those in your library in any good aerodynamics book.


FAQ on height of Atmosphere

Air resistance ceases for all practical purposes at about 635,000 feet (about 120 miles up). However, satellites placed in orbits at that height degrade. To evaluate performance of aircraft, we need some reference standard conditions for comparison. Yet the conditions in the atmosphere vary continuously, and it generally is not possible to obtain exactly the same set of conditions on two different days. Accordingly, we must arbitrarily set up a group of standard conditions that we may use for reference. The set of standard conditions used in the US is known as the ICAO atmosphere, which has been adopted as standard by most of the principal nations of the world. The ICAO atmosphere defines average conditions up to approximately 65,000 feet of altitude; beyond this point the standard in the US is the 1962 model atmosphere, which defines conditions up to 700 kilometers. It is doubtful whether either the kinetic theory of gases or the equation of state are meaningful much above 300,000 feet. The book Mechanics and Thermodynamics of Propulsion by Hill and Peterson, 1965, (Addison Wesley publishers) reports that The Air Research and Defense Command (ARDC) of the US Air Force used a model that goes up to an altitude of 295,276 feet. So it looks like 300,000 feet is what most people use as the limit of the atmosphere. To convert all numbers given in feet to numbers in kilometers, multiply feet by .0003048 to get kilometers.


FAQ on Impulse Coupling

Engines having a small number of cylinders are sometimes equipped with what is known as an impulse coupling. This is a unit which will, at the time of spark production, give one of the magnetos attached to the engine a brief acceleration and produce a hot spark for starting. This device consists of small flyweights and spring assemblies located within the housing which attaches the magneto to the accessory shaft.  The magneto is flexibly connected through the impulse coupling by means
of the spring so that at low speed the magneto is temporarily held while the accessory shaft is rotated until the pistons reach approximately a top center position. At this point the magneto is released and the spring kicks back to its original position, resulting in a quick twist of the rotating magnet. This, being equivalent to high-speed magneto rotation, produces a hot spark.  After the engine is started and the magneto reaches a speed at which it furnishes sufficient current, the flyweights in the coupling fly outward due to centrifugal force and lock the two coupling members together. That makes
it a solid unit, returning the magneto to a normal timing position relative to the engine. The presence of an impulse coupling is identified by a sharp clicking noise as the crankshaft is turned at cranking speed past top center on each cylinder.  Use of the impulse coupling produces impact forces on the magneto, the engine drive parts, and various parts of the coupling unit. Often the flyweights become magnetized and do not engage the stop pins; congealed oil on the flyweights during cold weather may produce the same results. Another disadvantage of the impulse coupling is that it can produce only one spark for each firing cycle of the cylinder. This is a disadvantage especially during adverse starting conditions.


FAQ on stressed skin

An example might be if you have long wings. Due to their weight, the wing would droop due to the large moments that the wings would experience. This would have some detrimental effects on the flight characteristics of the wing. So, to remove the droop, you would stress the skin so that it would be in compression and then place it on the wing structure. What would happen is that due to the weight of the wing, the skin would "stretch" due to the large moments BUT the wing would have less droop since the stretch of the skin would take up some of the large moments' effect. This would make the wing have better aerodynamic characteristics.


FAQ on wind tunnels

There is much material about wind tunnels enough for several books to be published about them. Here is the name of one: Low Speed wind tunnel testing by Willieam Rae and Alan Pope published by Wiley Interscience in 1984. A very quick overview of wind tunnels is that they can be used to test wing shapes or any body, for that matter, to see how it would react to wind. Wind tunnels obey both the law of continuity (density x cross-sectional area x velocity is a constant) and bernoulli's law (pressure + density x velocity squared /2 = constant) as well as the gas law (pressure = density x universal gas constant x temperature). That means that along every point of the centerline of the tunnel both continuity and bernoulli's laws hold for steady, nontimevarying flow.  These equations hold pretty much in the center of the wind tunnel and less so as you near the walls of the tunnel. Wind tunnels have been used to see how wings/airfoils produce lift and drag. They have also been used to see how buildings on fire will react to wind. They have also been used to see how aircraft will react to icing conditions (see our research section of the website).


FAQ on why airships use helium now than hydrogen ?

It was flammable and if a spark lit it, it could explode. That is why helium is used--it is an inert gas. Use our search engine and type in helium to find out why they switched over. also learn and hear about the Hindenburg that was a hydrogen filled airship that burst into flames.


FAQ on What type of hair should be used to make a more accurate Hygrometer?

According to the instructions just use an ordinary hair, especially one that is straight and
not very curly. Since you were told to make sure the oil is removed from the hair, any chemical treatment might affect the results but for the overall purpose of the hygrometer, to see how the dampness and dryness of the air has different affects, it should not matter very much. Once you determine where the number 10 goes, you can use a protractor to make markings as close as you wish to get an accurate scale.
Look at the diagram to see that the scale you create is along the arc of a circle.


FAQ about  how long before pilots put on their autopilot

This answer is provided by Capt. Bill Palmer, a commercial airlines pilot:

There's not going to be a solid answer to this one. Much will depend on the aircraft type and the mood of the pilot. For more advanced aircraft with advanced FMS systems (a really great autopilot) he may turn it on at 500 feet and not turn it off again until short final. For older generation aircraft (727) it might be more common to hand fly it to at least 10,000 feet, or even to altitude, and hand fly again in the terminal area. There there's everything inbetween. I fly the DC-10 with an old but OK autoflight system. For a complex departure procedure, I'll turn on the AP maybe at 500-1000 feet, otherwise maybe at 5000 feet. and typically leave it on until final.


FAQ on the effects of "flaps" on wings

They are there to increase the drag on the airplane but do not affect appreciably the lift, for example during landing.  Go to http://www.allstar.fiu.edu/aero/wing33.htm for more information on flaps and when to use them.


FAQ on flying upside down

Please read the information on flight.


Continue to see more FAQs on Principles of Flight.



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Updated: June 04, 2008