Dihedral, Dihedral (Aircraft) Angle

Image: Dihedral

Dihedral:

The V-shaped bend in the wing. Typically, more dihedral causes more aerodynamic stability in an airplane, and causes the rudder to control both the roll and yaw axis. This is why some trainers and sailplanes require only 3 channels of radio control--i.e., having no ailerons.

Image: Dihedral Angle

Dihedral Angle

In the illustration above, A and B are two separate planes lying perpendicular to another plane C. The dihedral angle equals zero between planes A and B.

To demonstrate a dihedral angle greater than zero, first let aA and aB equal 90 degrees. Second, let plane B rotate around the line where plane B and C intersect while letting plane A remain perpendicular to C. For example, let aB (the angle where plane B intersects plane C) equal 60 degrees.

The dihedral angle (represented by the symbol J) between A and B now equals 30 degrees. This can also be viewed as the illustration below.

Dihedral (Aircraft)

Dihedral angle is the upward angle from horizontal of the wings or tailplane of a fixed-wing aircraft. "Anhedral angle" is the name given to negative dihedral angle, that is, when there is a downward angle from horizontal of the wings or tailplane of a fixed-wing aircraft.

 Schematic of dihedral and anhedral angle of an aircraft wing.

Dihedral angle (or anhedral angle) has a strong influence on dihedral effect, which is named after it. Dihedral effect is the amount of roll moment produced per degree (or radian) of sideslip. Dihedral effect is a critical factor in the stability of an aircraft about the roll axis (the spiral mode). It is also pertinent to the nature of an aircraft's Dutch roll oscillation and to maneuverability about the roll axis.

 Measuring the dihedral angle.

Longitudinal dihedral is a comparatively obscure term related to the pitch axis of an airplane. It is the angle between the zero lift axis of the wing and horizontal tail. Longitudinal dihedral can influence the nature of controllability about the pitch axis and the nature of an aircraft's phugoid-mode oscillation.

When the term "dihedral" (of an aircraft) is used by itself it is usually intended to mean "dihedral angle". However, context may otherwise indicate that "dihedral effect" is the intended meaning.

Image: Anhedral angle

Source: Wiki

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Video: Teaser for "Dead Stick Takeoff Flying Adventures"

Teaser for my new 45 minute video called "Dead Stick Takeoff Flying Adventures"

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Differential Throw

Differential Throw Ailerons
Ailerons that are set up to deflect more in the upward direction than downward are said to have Differential Throw. The purpose is to counteract Adverse Yaw.

Radio controlled aircraft with ailerons can benefit from differential throws of ailerons. Aileron differential means that the aileron that moves upward needs to be deflected by a larger angle, and the one that moves downward is being deflected by a smaller angle. This results in a more coordinated roll of the aircraft because if the aileron throws were the same, the equal angle of downward deflection causes more drag than lift for the upward moving wing, slowing the wing down and causing the aircraft to yaw in the direction opposite to the desired direction of turn (if any).
     While desirable, differential aileron throws is not really a critical flight function and is not implemented in many lower-cost computer radios. And, of course, it is not at all available in simple, non-computer radios. And if you sensibly choose to drive both ailerons with one servo then transmitter programming is of no use at all.
     There is a simple way of accomplishing differential aileron throws mechanically, by positioning control horns away from the hinge of the control surface. On this page we provide simple charts that allow one to measure and position aileron control horns to get precise maximum throw angles while achieving the desired differential.

To use the charts, first make a note of the deflection angle you need and of what percentage of the upward deflection angle you want the downward deflection angle to be (the differential). Next critical parameter is servo arm travel. This parameter is what you can change by placing the aileron linkage in the different holes in the servo arm.
 Next, follow the links in the table below to find the servo arm travel that will enable you to select the horn offset and clevis height, while giving the desired deflection angle and percentage of differential. Make sure that you use charts for the same servo arm travel.
Source: http://www.rcmix.com/diff_ailerons.html

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Dead Stick

A term used to describe unpowered flight (glide) when the engine quits running.

With the engine quiet and the plane ready for takeoff, Steve coaxes the Highlander into flight. The plane gains speed as it coasts down a steep hill and before long it is airborne. Now gliding through the air, the engine remains off; Steve brings the plane in, landing it just as he took off: completely deadstick. The shear excitement and joy from this maneuver is contagious. Not only do you easily feel Steve’s enthusiasm for the feat he is performing,
but you also feel his love for the air and for his plane. Without the Highlander this would be nearly impossible.  However, due to the unique qualities of the plane, Steve was able to master this act and share his joy with the world.

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Clunk

A weighted fuel pick-up used in a fuel tank to assure the intake line is always in fuel.

The Nitro Fuel Tank Clunk
For those of you in the RC airplane world this is nothing new, but it might be a new term or idea for those of you with nitro RC cars, truck, or boats.

RC aircraft fly in many different attitudes – meaning pointing up, pointing down, on their sides, and upside down... not to mention the high G forces pulling the fuel to one side of the tank or the other.

If the fuel pick up was at a fixed location in the tank – say the lowest part of the tank like in a car – the air craft would only get fuel when it is flying straight and level. Any banking or inverted flying would starve the engine of nitro fuel.

A very simple solution of using a short length of fuel tubing inside the fuel tank with a heavy weight at the end of the tube called a "CLUNK" ensures no fuel starvation. This tube and clunk will simply flop around inside the fuel tank which ever way gravity pulls on it - just like the fuel in the tank. This means no mater what the RC aircraft is doing, the pick up end of the fuel tube in the tank is always submerged in fuel.

This clunk, more specifically the fuel tube it is hooked up to inside the fuel tank should be checked for deterioration every year or so. The tube over the years will get brittle and may crack or come off the supply tube in your fuel tank. This of course means you now have a fixed nitro fuel pick-up and all the benefits of the clunk are lost.

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Chicken Stick

A hand-held stick used to "flip start" a model airplane engine.

The Hobbico Safe Start "chicken stick" is a safe, easy way to Flip-Start Glow Powered Engines. This stick is held in your hand and with the extended end placed against the propeller on the engine. Then with a quick flip of the wrist to rotate the prop, starting the engine.

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Charger Tips

CHARGER TIPS:

1. Your always there to monitor the cells (don't leave it unattended) 
2. Get a quailty battery (Thunder Powers are great) 
3. Quailty LIPO CHARGER, you MUST (notice the caps) get a LIPO CHARGER. You cannot charge lipos with ordinary chargers for NI-CD, etc.
4. Investing in a good balancer is a wise decision 
5. Get well known Lipo batteries. DO NOT get no named cheap batteries just because their cheap because you might have to spend another $10,000 fixing your house if it burns.
6. It is not mandatory for you to get a fire-proof box but it is recommended
7. Do not charge/store your lipo on your plane/heli
8. Do not charge near flammables/explosive substances (common sense)
9. If your pack is damaged/broken, soak it in salt water for a while then contact your hazardous waste disposal company for advice on throwing it out
10. DO NOT OVERDISCHARGE YOUR LI-PO BATTERY (don't fly until you can't get the rotor to turn anymore)!!!
11. Store in a dry, cool area with some sort of case (so it won't get damaged)
12. Connect your charger to the main power supply first then your battery to your charger to prevent shorting your pack
13. Double, Triple check your setting on your charger before you charge your battery
14. Read the charger manual before you charge
15. Always solder the female plug onto the battery.
16. If any single cell in your lipo drops below 3.0 volts your pack may be ruined. 9.0 volts for a 3 cell pack is too low of a setting on a monitor.
17. IF you crash, set your lipo aside in a safe place for a while, even if it looks undamaged. Internal shorting can occure and cause a fire
18. When setting up a lipo power system, always try to match battery Mah capacity to be at least, over the expected current draw from your motor and ESC systems. Always use good quality power connectors like deans or similar. Poor quality connectors can = meltdown = burnt model = burnt house or car = dead modeller.
19. Li-pos should NOT get warm during a charge. During a discharge, they should not exceed 140F (worst case, lower is obviously better). 

 Be Bright, Charge Right
 Charge Wrong, Your Gone

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Charger

Device used to recharge batteries, usually supplied with the radio if NiCd batteries are included.

LiPo charger: It is imperative that you use a specially made LiPo charger to recharge your batteries. Never use a charger designed for other types of rechargeable battery, the charging current will be wrong and there is no safety switch-off, the need to stop all LiPo chargers overcharging. Overcharging a LiPo battery, the battery caught fire, there are reports of exploding batteries.

Charge Rate: Always make sure that your charger at the same voltage as your LiPo battery. LiPo batteries are commonly used in batteries, so many chargers have a variable fee setting so that you can charge more packs. Check the label on the battery or battery to determine the output voltage. Place the charger on the same voltage, a little lower no problem, but a higher voltage damages the battery and can be dangerous, as in Section 1.

Excessive Discharge: LiPo batteries can be recharged at any point during the discharge with no ill effects or damage. However, if you fully discharge the battery and try to successfully - and that's unlikely, since LiPo manufacturers have built in a safety device to prevent this - it will not recharge. This is because, deep discharge destroys the chemical basis of the battery and make it unusable.

LiPo Charging: BagLegen Always store your batteries in a bag while they are chargeable. The bag is a fire and explosion protection so that if a problem occurs while the batteries are charged, you will be safe. They are fairly inexpensive and widely available from electrical and hobby stores. Never leave LiPo batteries, the charge will be unsupervised. Always turn the charger when the batteries are charged and allow them in the bag before they cool.

CHARGER TIPS

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