107 votes
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What are these criss-cross patterns close to Cambridge Airport (UK)?

In 2017 there was a major archeological dig in the area of Hatherdene Close and Coldhams Lane at the south end of the Cambridge airport. The "criss-cross patterns" are additional exploratory trenches ...
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73 votes
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Why are Oscar, India, and X-Ray (O, I, and X) not used as taxiway identifiers?

Because those symbols are easily confused with the number 0, the number 1 and the symbol for a closed runway/taxiway (✕) respectively. (1) Numbers by themselves, and the letters "I" ...
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55 votes
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My windsock is erect, what does this mean?

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 ...
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38 votes
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What is this star shaped symbol on the tarmac?

That is a Compass Rose, painted on a Compass Calibration Pad. It's used to mark a location on the airport surface that is suitable for calibrating the compass of an aircraft. Here's one in a slightly ...
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37 votes
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What does RTF mean?

"RTF Instructions" probably means "Radiotelephone Instructions" As suggested here, it should not be confused (as I initially did) with the "RTF" of internet fame (from RTFM, for those that are still ...
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35 votes
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What is "judgemental oversteering" in taxi procedures?

"Judgmental oversteering" means to intentionally not follow the taxiway centerline when turning. It is a technique used on large aircraft to turn on tighter or smaller taxiways. In a sense, it is ...
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32 votes
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What are the slash markings on Gatwick's 08R/26L?

They are "Rapid Exit Taxiway Indicator Lights" as described in section 9.6 of CAP 637. 9.6 Rapid Exit Taxiway Indicator Lights 9.6.1 Rapid exit taxiway indicator lights (RETILs) ...
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  • 8,843
31 votes
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What is this radar-like thing?

It is a wind tee; it serves the same function as a wind sock. It is designed to resemble an airplane from the air so that pilots overflying the field can more easily determine in which direction they ...
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  • 8,150
29 votes
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What is this white rectangle painted on runway 23 at KCRW?

Seems to be touchdown zone markings for assault landing practice by C-17's. For assault landings, the standard is to touch down in the first 500' of the Landing Zone (LZ), and to go around if your ...
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  • 42.1k
27 votes

What are these large yellow circles painted across the runway?

That would be the "line" telling military pilots where the arresting cables are. If you look to the side of those circles, you can see the arresting mechanism these. It would be yellow so that it ...
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26 votes

Why are lat-lon coordinates written at parking bays in civil airports?

These checkpoint coordinates are used to verify the current location of the aircraft for navigation purposes. The coordinates can be used to check, input or calibrate the navigation system's current ...
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  • 1,095
24 votes

What is this radar-like thing?

It's a lighted 'wind tee'. this website shows various wind direction indicators
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  • 1,802
24 votes
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What are these devices on or adjacent to an airport taxi-way?

It is not a road that you are looking at, it is the edge of the runway / taxiway. The double yellow lines are used to define the taxiway edge from the shoulder or some other abutting paved surface ...
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22 votes
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What are these large yellow circles painted across the runway?

A large number of airports in the world are used for both civil and military operations and quite a few of these have arresting systems installed on them. According to Boeing Aero No. 13: Of the ...
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22 votes
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What are these symbols on the runway?

The first one is the holding position marking. It denotes the entrance from the taxiway into the runway. The dashed lines are in the side of the runway. The second one is the non movement area ...
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19 votes
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What are these markings on the runway at Haneda Airport?

I dug around for a while but couldn't find any official documentation on this (I suspect someone whose Japanese is better than mine will have to do that.) But! I did find the markings on all of ...
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18 votes

FAA Commercial Pilot Knowledge Test: Sign Question

This sign is a taxiway ending marker. I retrieved this graphic from the CFI Notebook Website.
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18 votes
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Why are lat-lon coordinates written at parking bays in civil airports?

If you are referring to GPS coordinates shown at the gates, as in this image: Source: ADB Safegate the reason is: to allow the pilots to properly prime their inertial navigation system with a known ...
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17 votes
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What is this odd large sign near Aalborg airport/millitary airport?

It's a maritime navigation aid. I'm fairly rusty, but I'm pretty sure it's a form of lead mark. When seen from the water, as you travel towards the mark, if you keep the diamond centred between the ...
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  • 1,262
17 votes
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What does the sign "Caution your blast" mean?

I'm fairly sure that sign is beside taxiway C*, and as you can see from the aerodrome chart it is right next to the main apron. Aircraft holding in this position have the main apron directly behind ...
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17 votes
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What is the meaning of this airport marking?

The marking indicates that vehicles must yield to aircraft. It is placed in areas where a service road crosses a taxiway.
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16 votes
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How do you calibrate the compass of an aircraft on a compass rose?

Most aircraft compasses include compensating magnets to correct for installation error (due to natural magnetic fields in an aircraft from steel parts and electrical equipment). When installing a new ...
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16 votes
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What's the point of having ILS on runway signs?

These markings designate the hold-short point during different runway operations. Runway hold-short points are marked by white text on a red background. They designate a point which any aircraft must ...
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  • 39.3k
16 votes

Why would an airport use an L/R runway combination and a second number instead of L/C/R?

There is flexibility on the numbering of parallel runways based on a number of factors as described in FAA advisory_circular/150-5340-1J -page 4 (see excerpt below). In the case of KPHX for example, ...
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  • 19.8k
15 votes
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What are the areas marked in green around the taxiways?

It's essentially "fake grass" -- a "no taxi" / "no drive" area, the same as real grass would be. The concrete may very possibly be stressed to support the full weight of big aircraft, and the areas ...
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  • 42.1k
14 votes

My windsock is erect, what does this mean?

According to the FAA, Advisory Circular 150/5345-27E, dtd 26 Sep 2013, Paragraph 3.2.2, 3.2.2 Dimensions The taper or the fabric windsock from the throat to the trailing end must be designed to cause ...
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