hi Guys,

I wanted to know how ppl decide if the flying conditions are good to fly a rc Heli ? , also interested in flying conditions for rc planes.

Today in Bangalore,.. From past 2 days monsoon is active in Karnataka coast hence @ Bangalore its very cloudy and windy. Which i presume is not a good time to fly, Or perhaps for my flying skills its not a good flying condition.

Please let us know how you guys decide.

Thanks,
Srivatsa

Rep 17# onwards, Basic Meteorology for RC Flying is covered[

it is a very complicated question which probably requires a thread to reply (Which i have been working on anyways, to start one) suffice to say, calm winds, Beaufort scale of 1 is what is recommend for model flying, Beaufort 2 is ok, 3 certainly not

Thanks sir .. is it generalised for all class of models? I mean sizes?

most! Beaufort 2, slope soarers, sailpanes excluded

For you - a simple rule of thumb is - if its too windy to play badminton
its too windy to fly.


- as you get better - you can decide for yourself.

So, instead of flying, it's time for creation.

And the rule same for RAIN too..

What to do in this rainy season , if we cant fly

I'm planning to build a 500 heli : .. i feel it might withstand winds than the 450v2 i have now ..

fly fomies in indoor court/stadium

Which is the right condition of a pilot to fly

foremost , "dont drink and fly"   

Quote from: swizera on June 21, 2012, 07:15:48 AM
What to do in this rainy season , if we cant fly

hold all your crashed planes and fix them in rainy reason...  or practice new manoeuvres on simulator... have a cup of tea and pakore... 

Just picked from  rcbazaar, yummm

Quote from: swizera on June 21, 2012, 07:15:48 AM
What to do in this rainy season

Fly an easystar, that bugger can handle mild drizzles very easily

i agree! even an FPV system ! just proven yesterday

Very few heli guys around here  

Sent via tapatalk

Right condition of flying the heli depends on the following:-

a. If you have all electonics like Gyro and ESC covered with water proof material (in case it's raining a bit)
b. Visibility if you can see the Heli 30 to 40 feet away in the sky.
c. Your flying skills, turn on the wind function in your simulator to practice how to handle sudden dips created by wind gusts.
d. Windy days are good to practice auto-rotations, so sometimes I beg for a windy day
e. buy a cheap anemometer from HK and keep progessing on your wind handling capability.

Once you get use to handle sudden dips you will be able to fly your heli in a reasonalbe windy day.

I hope this helps

Hellyflyer

Just enough Basic Meteorology (Hereinafter refered to as 'Met' in this thread) for RC Flying. we shall try and clear the cobwebs on Pressure, Temptrature, etc and various speeds in question (Airspeed, Ground speed etc) feel free to ask questions, refer to the post when you do do, PLEASE keep it relevant.

Look at this image and assimilate all that you can before we proceed, pay attention to Pressure, Mean Free Path and Acceleration lines.

The Atmosphere

1.   Atmosphere is the term given to the layer of air, which surrounds the Earth and extends upwards from its surface to about 500 miles (800 km).  The flight of all objects using fixed or moving wings to sustain them, or air breathing engines to propel them, is confined to the lower layers of atmosphere. The properties of atmosphere are therefore of great importance to all forms of flight.

2.   (Included to address issues of high alt FPV/autonomous flying)The Earth's atmosphere has gaseous layers.  The layer nearest to the surface is known as the troposphere, above which are the stratosphere, the mesosphere and the thermosphere.  The boundary of troposphere, known as the tropopause, is not at a constant height but varies from an average of about 25,000 ft at the poles to 54,000 ft at the equator. 

3.   The weight of the atmosphere is about one millionth of that of Earth, and an air column one square metre in section extending vertically through the atmosphere weighs 9800 kg.  Since air is compressible, the troposphere contains a greater part (over three quarters in middle latitudes) of the whole mass of the atmosphere, while the remaining fraction is spread out with ever-increasing rarity over a height range of some hundred times that of the troposphere.

4.   Pressure falls steadily with height, but that temperature falls steadily upto the tropopause, where it then remains constant through the stratosphere, but increasing for a while in the warm upper layers.  Temperature falls again in the mesosphere and eventually increases rapidly in the thermosphere.  The mean free path (M) is an indication of the distance of one molecule of gas from its neighbours. Therefore in the thermosphere, although the individual air molecules have the temperatures shown, their extremely rarefied nature results in a negligible heat transfer to any body present.

Physical Properties of Air

1.   Air is a compressible fluid and as such it is able to flow or change its shape when subjected even to minute pressures.  At normal temperatures, metals such as iron and copper are highly resistant to deformation by pressure, but in liquid form they flow readily.  In solids the molecules adhere so strongly that large forces are needed to change their position with respect to other molecules.  In fluids, however, the degree of cohesion of the molecules is so small that very small forces suffice to move them in relation to each other.  A fluid in which there is no cohesion between the molecules and therefore no internal friction i.e. inviscid, and which is incompressible would be an "ideal" fluid - if it were obtainable. for theory we will consider air an ideal fluid

2.   Fluid Pressure.    At any point in a fluid the pressure is same in all directions, and if a body is immersed in a stationary fluid the pressure on any point of the body acts at right angles to the surface at that point irrespective of the shape or position of the body.

3.   Composition of Air.    Since air is a fluid having a very low internal friction it can be considered, within limits, to be an ideal fluid.  Air is a mixture of a number of separate gases, the proportions of which are:

Element   By Volume %   By Weight %
Nitrogen       78.08               75.5
Oxygen       20.94               23.1
Argon       0.93               1.3
CO2               0.03               0.05
Hydrogen            Traces Only

For all practical purposes the atmosphere can be regarded as consisting of 21% oxygen and 78% nitrogen by volume.  Up to a height of some five to six miles water vapour is found in varying quantities.  The amount of water vapour in a given mass of air depends on the temperature and whether the air is, or has recently been, over large areas of water.  Higher the temperature, greater is the amount of water vapour that the air can hold. (This is important for RC flying and will be referred to later)

Temperature

Measurement of Temperature.    The Celsius scale is normally used for recording atmospheric temperatures and working temperatures of engines and other equipment.  On this scale water freezes at 0° and boils at 100°, at sea level.  In scientific measurement of temperature absolute zero has a special significance. At this temperature a body is said to have no heat whatsoever.  Temperatures relative to absolute zero are measured in Kelvin (also known before 1967 as degrees Kelvin) and are used in all formulae dealing with density and pressures.  Kelvin (K) zero occurs at - 273.15° Celsius (C).

Conversion Factors.    Fahrenheit (F) scale may be encountered dealing with people from the US of A.  It is not suitable for scientific purposes, as Fahrenheit zero has no particular significance. Water at sea level freezes at 32° F and boils at 212° F.  To convert °F to °C, subtract 32° and multiply by 5/9. To convert °C to °F, multiply by 9/5 and add 32°.  To convert °C to Kelvin or °K (Absolute) add 273° (or more precisely 273.15°). My thumbrule 1/2 or double (Depending on the case) give or take 10% and + or - 32)


The standard sea level temperature of air is 15°C all eqpt, incl RC eqpt are calibrated to this temp. fro rest of the info see image above.

Pressure

The standard sea level pressure is 1013.25 mb. The pressure at any point in a stationary fluid is determined by the weight of fluid in question. Same is the case with air in the atmosphere. It follows that the pressure must fall steadily with increasing altitude. However, because the density also falls, the rate at which the pressure falls must decline as the altitude increases.

Pressure Altitude.    If the sea level pressure should be other than 1013.25 mb. Pressure altitude can be found either by calculating a height change of 30 ft for every 1 mb difference in pressure away from 1013.25 mb at the surface.

Density

Density (ρ) is mass per unit volume.  The unit of density used in this book is kg per m³. 

Effect of Pressure on Density.    When air is compressed, a greater amount can occupy a given volume, i.e. the mass, and therefore the density, has increased.  Conversely, when air is expanded less mass occupies the original volume and the density decreases.  provided the temperature remains constant, density is directly proportional to pressure, i.e. if the pressure is halved, so is the density, and vice versa.

Effect of Temperature on Density.    When air is heated it expands so that a smaller mass will occupy a given volume, therefore the density will have decreased, assuming that the pressure remains constant.  The converse will also apply.  Thus the density of the air will vary inversely as the absolute temperature.  In the atmosphere the fairly rapid drop in pressure as altitude is increased has the dominating effect on density, as against the effect of the fall in temperature, which tends to increase the density. Pressure is the Boss! boss 

Effect of Humidity on Density.    In the atmosphere some water vapour is invariably present.  important factor in the performance of a RC aircraft.  The density of water vapour under standard sea level conditions is 0.760 kg per m³.  Therefore water vapour can be seen to weigh 0.760/1.225 as much as air, roughly 5/8 as much as air at sea level.  This means that under standard sea level conditions the portion of a mass of air, which holds water vapour, weighs (1 – 5/8), or 3/8 less than it would if it were dry.  Therefore air is least dense when it contains a maximum amount of water vapour and most dense when it is perfectly dry.

Density Altitude. (Shillong Effect )    For aircraft operations air density is usually expressed as a density altitude.  Density Altitude is defined as that height (above or below mean sea level) in the standardized atmosphere to which the actual density at any particular point corresponds.  For standard conditions of temperature and pressure, density altitude is the same as pressure altitude.

Viscosity

Coefficient of Viscosity (μ).    The value of coefficient of viscosity of air at sea level in the standard atmosphere, μ0, is 1.79 X 10 -5 kg / ms. The coefficient, μ, for any given gas, depends directly on its temperature (μ is proportional to T¾). Thus μ falls steadily with increasing altitude until the tropopause is reached and remains constant in the stratosphere.

Kinematic Viscosity.    An alternative measure of the viscosity of a gas is its kinematic viscosity, defined by the formula K  = μ / ρ. Its standard sea level value is 1.46 X 10 – 5 m²/s.  In the troposphere μ & ρ both reduce with increasing altitude but ρ does so more rapidly.  In the stratosphere ρ falls while μ  is constant.  Therefore  increases with altitude in both regions.

Look a tthe table below as an indication to what we discussed so far

Alt n Ft        Temp                 Pressure in MB    Pressure in PSI  Density (Kg per m³)
0           +15.0             1013.25                    14.7                   1.225   
5,000   +5.1                      843.1                    12.22           1.056   
10,000   -4.8                      696.8                    10.11           0.905   
15,000   -14.7                      571.8                    8.29                   0.771
20,000   -24.6                      465.6                    6.75                   0.653   

this is Beaufort scale, a good thumb rule for RC fliers,

Little trivia on Beaufort, thanks to wiki, rest you can read there

The scale was devised in 1805 by Francis Beaufort (later Rear Admiral Sir Francis Beaufort), an Irish-born Royal Navy officer, while serving on HMS Woolwich. The scale that carries Beaufort's name had a long and complex evolution, from the previous work of others, including Daniel Defoe the century before, to when Beaufort was a top administrator in the Royal Navy in the 1830s when it was adopted officially and first used during the voyage of Charles Darwin on HMS Beagle. In the early 19th century, naval officers made regular weather observations, but there was no standard scale and so they could be very subjective — one man's "stiff breeze" might be another's "soft breeze". Beaufort succeeded in standardizing the scale.

here is the link on Model News discussing Density Altitude, titled Beat the heat, remember your Density Altitude

PS
Did they take a cue from our thread