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Questions tagged [separation]

Questions regarding the distance separating aircraft during flight.

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How is radar separation assured between primary and secondary targets?

Air traffic control radars come in two flavours, with most ATC centers using both and displaying the output of both on a single screen: Primary surveillance radar (PSR) is a true radar system, which ...
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1answer
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How does the ICAO VOR separation apply to reciprocal radials?

If two aircraft are on VOR radials that are apart by 15 degrees or more and one aircraft is at least 15 DME out, they are considered laterally separate. I read this rule in ICAO documents but my ...
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1answer
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What does “zero offset between two waypoints” mean in ICAO Doc 4444?

My question is with reference to the GNSS based separation specified in ICAO Doc 4444. Could someone explain the significance/meaning of the condition "zero offset between two waypoints" criteria? if ...
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189 views

Why do planes above FL290 need more vertical spacing?

At altitudes no higher than 29,000 feet, planes need only 1,000 feet of vertical separation. However, planes over FL290 need twice that, i.e. they need 2,000 feet of vertical spacing between them and ...
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What vertical separation is required in a holding stack to avoid wake turbulence?

Sometimes in my free time I play Endless ATC, a game where one acts as the approach and departure controller. In the game (as in real life) the controller is forced to put planes in a holding stack, ...
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Why do heavy departures wait 5-10 minutes on the runway at ZRH?

I'm frequently travelling to Zürich for business and I usually make my schedule so that I have at least an hour to do some planespotting and photographing at the ZRH airport. Whenever I came to the ...
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1answer
402 views

What causes the adverse pressure gradient that leads to flow separation?

When reading about flow separation I generally see a diagram like this: imp source: Wikimedia commons This shows that the boundary layer slows as it passes over the wing, eventually creating an ...
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2answers
174 views

Why are both ATC and TCAS tasked to prevent collisions although TCAS takes precedence anyway?

« The primary purpose of ATC worldwide is to prevent collisions [...] Many aircraft also have collision avoidance systems, which provide additional safety by warning pilots when other aircraft get ...
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1answer
107 views

What would be a safe minimum vertical separation distance between passenger-carrying multicopter aircraft?

There is increasing talk about employing passenger-carrying multicopters ("taxi drones") to extend urban mobility into the third dimension. These aircraft will have MTOMs in the range of several ...
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2answers
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Is the Tower (Local) Controller responsible for “separating” VFR traffic in the pattern in the U.S. in Class D airspace?

For example, in U.S. Class D airspace, if an inbound aircraft operating VFR is instructed by the Control Tower to "enter left downwind for runway 18, report entering downwind," is the controller ...
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1answer
926 views

Vertical and horizontal separation between cruising and climbing aircraft

I was recently a passenger on a commercial aircraft at cruise altitude when I noticed another aircraft just reaching its cruising altitude while crossing our flightpath from below, at what looked like ...
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1answer
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Is true altitude vertical separation between airplanes dependent on temperature?

Does the "true" altitude vertical separation between airplanes (using the same altimeter setting) vary as the temperature changes? ( I fully realize that the "true" altitude of both airplanes is ...
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1answer
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How close is this Su-27 to the aircraft recording the pass?

There is footage of an intercept of a US Nay recon aircraft being intercepted by a Russian Su-27: (still from the BBC video article, who look like they got it from the US Navy directly) which was ...
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119 views

Diversions because of fog: What are the reasons?

It's fog season again around my local airport MUC (EDDM), and I have noticed a number of diversions recently. Some planes were holding a bit before attempting to land, performed a go around and then ...
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2answers
194 views

Can RVSM safely be further reduced?

Since the world population shows no signs of slowing down its rapid increase, it's pretty safe to say that means we can only expect more concurrent flights as time moves forward. Is it physically ...
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2answers
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What does “leave clear on its left” mean in UK regulations relating to collision avoidance on non-runway landings?

This doesn't seem to be plain English, could someone explain this with a simple example for me please? I'm not sure what 'Leave clear on it's left' means, and it's not clear whether the subject of the ...
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1answer
353 views

How exactly do ICAO's VOR-based minimum separation standards work?

This question is aimed at Air Traffic Controllers who are familiar with ICAO Separation minima. DOC 4444 states the following: Lateral separation between two aircraft exists when: VOR: both ...
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What is the legal definition of separation as it relates to ATC? [duplicate]

ATC provides "separation" for all aircraft in class bravo airspace. What is the legal definition of separation? Is it the same or different than the see-and-avoid rule (FAR Part 91.113(b)) where all ...
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4answers
166 views

How to make ourselves more visible to other aircraft?

What are the best practices in air to help others see our aircraft?
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1answer
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How is separation managed when there are only two parallel runways in a very busy airport?

In the world's busiest airports, how is separation managed between departures and arrivals when there are only two parallel runways like in London Heathrow. What is the minimum safe separation?
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3answers
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What is the effect of flow separation on lift, pressure distribution and drag?

Consider an airfoil (a wing) in an airflow. When angle of attack increases, at some point the flow start to separate from trailing edge. By increasing the angle of attack more, this separation area ...
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How close can planes fly to each other over the ocean?

While on a recent Air Transat flight from Toronto Pearson to London Gatwick, several hours into the flight and over the Atlantic Ocean, my daughter and I noticed a plane behind ours to the left, ...
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1answer
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What is the minimum separation for aircraft operating on or intersecting the same runway?

How capturing of this photo was ever possible: (photo courtesy of jetphotos.com) Shouldn't there be a bigger time / distance separation of three aircrafts using, operating or intersecting the same ...
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1answer
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How does vertical separation work above FL400?

The information mentioned in "Jeppesen Airway Manual" is that after FL400, fight levels are FL430, FL470, FL510 for the 'even' FL's column. Normally, I would expect every level divided by a thousand ...
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2answers
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Is the pilot required to keep visual lookout during IFR operations in VMC?

During VFR operations, the pilot must always self-assure separation from other aircraft, and thus must maintain a visual lookout all the time. For IFR operations but in VMC, are there any rules as to ...
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1answer
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How far should commercial jets be from each other when on the runway or while departing?

Does anyone know how far should a commercial jet (787,777,etc...) be away from each other in runway or in process of taking off? Are there public resources that I can look up?
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Is there a “maximum” airplane count in the visible sky at a given location? [closed]

At night, I look at the planes in the sky and count them. I can normally spot between 2-5 planes, never more. As the visible sky is always a constant area and there are security distances and aerial ...
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0answers
173 views

What are normal landing separation minima? [duplicate]

As far as I know we have separation minima of 10 minutes in horizontal flight, so do we have any equivalent separation minima for landing? If so, how it is possible to land two aircraft in a very ...
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2answers
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How are aircraft separated at high altitude?

When cruising at high altitude, a fixed-wing aircraft has less margin for adjusting its speed, due to the convergence of the stall "speed" and the overspeed limit: If and aircraft has to be separated ...
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2answers
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How does ATC handle changing QNH/altimeter values?

Obviously for aircraft arriving to or departing from an airport/airspace (as relevant), they listen to the ATIS and/or are given the QNH. But what happens if that pressure changes? Even a fairly ...
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4answers
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Does ATC have to maintain separation on diverging aircraft?

Say you have an eastbound flight at FL210 that wants to climb and a westbound flight on a converging track at FL220 that wants to descend. There's the minimum required 1000 ft vertical separation. ...
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2answers
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How much noise does flow separation cause?

I recently found the following image showing the different sources of noise in vehicles. I notice that Aerodynamics is actually quite a big part of vehicle noise, as shown below by the blue line: ...
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Radar Control; is it possible for ATC to instruct track instead of heading?

Is it possible to use the track instead of headings in the aim to apply a radar separation?
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1answer
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What method does ATC use to calculate distance between two aircraft?

The distance between aircraft must be larger than the minimum separation all the time and is therefore quite important for Air Traffic Control (ATC). As I need to calculate the distance between ...
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2answers
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What are the rules for close/formation flying of civilian planes?

Two recent questions and their answers have raised a further question. In Are there laws about how close military aircraft can fly to passenger jets, and are they enforced?, we learned that "the ...
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1answer
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Are there laws about how close military aircraft can fly to passenger jets, and are they enforced?

Yesterday I was on a passenger plane flying at 35000 feet from Denver to JFK on a fairly clear day. Just west of Sioux City, we made a relatively sharp, but short, right turn for whatever reason (may ...
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How is a “conflict” between aircraft predicted and determined?

To answer my question about the prediction and determination of conflicts, we need a clear definition of the term. As far as I know is the term conflict often mistaken with the term loss of separation....
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2answers
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What are the most efficient layouts of multiple runways?

Many airports have more than one runway. How should runways be built in order to achieve maximum usage and minimum delays? Many major airports have most, if not all, parallel runways. Examples ...
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1answer
483 views

What are the differences and benefits between/of time-based vs distance-based separation?

This video suggests a time-based approach to landing aircraft separation is preferable to the distance-based standard commonly used. It advertises a greater arrival volume at airports, as strong ...
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At what distance between two aircraft will the air traffic controller get an alarm?

I am developing an air traffic control radar simulation. At what minimum distance between two aircraft in mid-air should a conflict alert be given?
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What information does a pilot have about aircraft operating on an intersecting runway?

This incident at O'Hare from July 2006 made me wonder what information is available to a pilot (specifically, in an airliner) regarding aircraft that are using an intersecting runway. In this ...
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Is it enough for crossing/ascending/descending IFR-flights to adhere to the separation minima?

The separation minima in Europe are in general 5NM lateral or 1000ft vertical. If the safety distance is too small, there is a conflict (loss of separation). When both aircraft are on the same track, ...
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Who is responsible for aircraft separation in IFR (limited/no visibility)?

I was reading how-much-is-the-minimum-safe-distance-between-two-planes-in-flight and realized part of it confused me (or maybe I'm just tired.)1 In a low- or no-visibility environment (i.e. under IFR ...
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How do ATC radars know where to position a primary target?

Primary target: An aircraft not reporting mode-C, the only thing the controller has is the return on the radar. When a controller reports a primary target as traffic to other aircraft, the controller ...
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How safe is IFR in class E?

In class D and E airspace, there is no separation between IFR and VFR traffic. However, most airspace in the United States below 18,500 feet MSL is class E airspace, which is exactly where non-...