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66

In general, flights get cancelled when arriving flights are delayed or themselves cancelled. Your flight needs three critical things to depart on time, or at all: an airplane, flight + cabin crew, and weather that meets requirements Aircraft may not arrive due to weather diversions (couldn't land with fuel on hand, etc). If there's no airplane, your flight ...


54

Windsocks come in various sizes and speeds, but an FAA Standard Wind Sock aligns with the wind at 3 knots, and is fully extended at 15 knots like CGCampbell pointed out. A typical wind sock (at least around here) looks something like this: The stripes are actually useful: The first stripe indicates a 3-knot breeze (The wind sock has turned and aligned ...


44

A cumulonimbus cloud (CB) is dangerous because of the processes occurring in them. At a minimum you will have an updraft and a downdraft containing rain. The particular CB you posted in your picture is typical of severe convection. The anvil is spreading out along the tropopause and there is significant overshooting tops over the anvil. This indicates ...


41

I could see the airport as clearly as one can see an airport in thick fog... If you saw the runway by looking down from your passenger seat as the airplane passed over the airport on the missed approach, you were looking only through an amount of fog approximately equal to the altitude of the aircraft above the ground. For purposes of discussion, let's say ...


38

The Concorde had 2 discrete windshields for different stages of flight. During subsonic flight (mainly take off and landing) the nose was drooped and the inner windshield was exposed. For supersonic flight the Concorde would raise its drop nose which also contained an outer windshield that would cover the inner windows. This outer windshield was made of ...


38

Ultrasonic anemometers are replacing the traditional cup anemometers in automated weather stations. The sensor measures the time it takes for an ultrasonic pulse to travel between the probes, which is affected by wind speed. In your second image, the object directly above the lights appears to be an anemometer. Source Ultrasonic sensors have the advantage ...


38

They looked out the window! If you are talking about a developing thunderstorm, especially during the day, they can be quite easy to see in front of you provided decent visibility. Here is some good footage of what it looks like to fly around a towering cell, you will note its fairly easy to see. At night, lightning, even in the clouds tends to be a ...


37

There are a few ways that pilots are aware of potentially turbulent areas. Eyesight The most obvious way is just by looking outside and observing the sky. Large billowing clouds, called cumulus clouds, indicated pockets of unstable air (the clouds are rising because the air under them is as well). If the pilots must fly through these clouds then its a ...


35

Quoting from the METAR decoder: BR Mist (Foggy conditions with visibilities greater than 5/8 statute mile) FG Fog (visibility 5/8 statute mile or less) You may ask "Why 5/8th of a statute mile?" That's because 5/8ths of a mile is 1,006 meters, or about 1 kilometer.


34

If you take off with a storm 20 minutes away from the airport, it won't have been "unforecast"; the NWS is much better than that. They can pretty accurately predict what's going to happen regarding various fronts at least 24 hours in advance, in turn giving you the advance notice to adjust your flight schedule to ensure you can get around the storm or well ...


32

Other answers have addressed the case of weather that's too bad for flights to operate, but another situation that can occur is congestion. Take a look at the Average Arrival Rate chart for San Francisco International Airport (SFO) (more details on this in this blog post by an airline dispatcher). During visual conditions with favorable winds, they can ...


31

A maintenance indicator sign, $, is included when an ASOS/AWSS (Automated Surface Observing System / Automated Weather Sensor System) detects that maintenance is needed on the system. Reference: http://www.faa.gov/documentLibrary/media/Order/JO%207900.5C.pdf Or if you need an easy way to remember it, courtesy of the awesome Ralph J: It means that they ...


31

The controller didn't overstep his boundaries, and he didn't tell the pilot to ignore a weather warning. Shamrock demanded something that's extreme for the NYC airspace: runway heading for 15 miles. Usually asking for right or left deviation is sufficient, and that appears to be what the previous Delta departure did. Once Shamrock declined an easterly ...


30

Yes, temperature effects airplane performance both the engine itself and the aerodynamics involved. What Is Density Altitude? Density altitude is pressure altitude corrected for nonstandard temperature. As temperature and altitude increase, air density decreases. In a sense, it's the altitude at which the airplane "feels" its flying. How Will High ...


29

Q: Was it dangerous? Is it according to standard procedure when approaching an airport in bad weather conditions? If the aircraft did not go below the Decision Height, no, it was not dangerous and it was according to standard procedures. Decision Height is defined as DECISION ALTITUDE/DECISION HEIGHT [ICAO Annex 6] - A specified altitude or height (A/H)...


28

Wind The problem with wind is that it can be from any direction, not necessarily the direction of the runway. When the wind is coming from the side instead of straight ahead, it is called a crosswind. This means that landing aircraft have to point into the wind to remain lined up with the runway. The slower they are flying, the further to the side they must ...


27

The ceiling is the lowest altitude where clouds cover more than half of the sky. This is important because climbing above that altitude means you will most likely have to fly through clouds. This makes navigation more difficult and pilots are required to have special training to fly in low visibility. If the ceiling is too low, pilots can't be at a safe ...


26

The vast majority of aircraft require an inspection, from small Cessna singles to Boeing airliners. Usually, they require at the very least: A visual inspection of the aircraft for damage, particularly the nose, tail section and wingtips. Most of the time, the damage is easily visible as "burn" marks or erosion of parts of the skin. A check of the ...


26

The main difference between the fog and mist is their density and as a consequence, the visibility. From UK Met office: ... they are two distinct terms for a similar phenomenon. Visibility less than 1,000 metres we call 'fog' and obscurity with visibility greater than 1,000 metres we call 'mist'. This is the same one given in FAA Aeronautical Information ...


26

Jet stream is a stream of air flowing around the Earth from West to East at high altitude. With wind speed averaging more than 100+ km/h, it has a tremendous effect on a plane's ground speed. The pattern, strength and location of the stream is constantly changing. For example, during the (Northern Hemisphere) winter the stream generally strengthens, and ...


25

The cause is reduced pressure in the wingtip vortex trailing behind the wing. Reduced pressure causes reduced temperature and if ambient humidity is high enough the result is the condensation you observe.


25

Hmmm, opening the window at 30.000ft, where the air temperature is about -40°C/-40°F, air speed is extreme, you can't survive without oxygen, and you want to put your arm outside??? Well, if you really do, you'll get a sunburn quite fast. I got a sun burn within an hour in an altitude of 3500m / 12000ft, though I was tanned due to two weeks at the beach. ...


25

The first trick to make windshields stronger is used also in aerodynamics: Sweep reduces the effects of speed. Giving the windshield an inclination both back- and sideways will reduce the impact energy of whatever hits it in flight direction. X-15 carried by a B-52 (picture source). Note the angled windows: They were oriented at 75° to the air stream, so an ...


25

The device used to measure wind speed is called an anemometer. The one that spins with 3 spoon-like arms is just one type. There are some that have a propeller or fan that spins like a windmill. There are other types that aren't so obvious, such as the ultrasonic anemometer that has no moving parts, but instead uses ultrasonic sound waves to measure wind ...


24

It is a mixture of factors. All else being the same: a contrail at a higher altitude will last longer (the lower temperature slows the sublimation of the ice cristals) a contrail formed in air with higher humidity will be bigger and last longer (more water is being turned into ice) If there is not enough (relative) humidity, the contrail will not form at ...


24

Short answer Based on past observations and a study led by Patrick Minnis from NASA, contrails could result in increasing the temperature over the ground by 1°C every 30 years over the US. From a study by German researchers Ulrike Burkhardt and Bernd Kärcher, the effect of contrails is comparable in other areas with a similar level of air traffic. Because ...


24

Practically speaking this isn't much of an issue, at least under VFR and if you're paying attention. Thunderstorms take some time to form, and as long as you can see them you can avoid them. I'm assuming you're asking here about isolated thunderstorms, the kind that form in late afternoon in hot, muggy conditions and aren't part of a frontal system. ...


23

The "anvil" of a Thunderstorm is always on the downwind side. Airline pilots routinely deviate around the upwind side in hopes of a smoother ride. photo source: CRAZY CLOUDS: The Thunderstorm Anvil


22

Severe convection will have anvil tops at the tropopause and overshooting tops can penetrate much higher (severe thunderstorm warnings often use a value of 60,000 ft for threats to aircraft). How high the overshooting tops can get is a balance of the positive buoyancy during parcel ascent against the negative buoyancy once it gets into the warming ...


22

These are wingtip vortices, which also appear in formula one, and this article explains the reason quite nicely (including airplane pictures and going into the difference between them and contrails). The significant paragraph: After the formation of the vortex, the pressure inside it decreases significantly as compared to the ambient pressure. This ...


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