Questions tagged [separation]

Questions regarding the distance separating aircraft during flight.

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What is the vertical separation minima between IFR and VFR?

ICAO Doc 4444, 5.3.2 says The vertical separation minimum (VSM) shall be: a) a nominal 300 m (1 000 ft) below FL 290 and a nominal 600 m (2 000 ft) at or above this level, except as provided for in b)...
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11 votes
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How does a TCAS system avoid unnecessary (RAs) resolution advisories when aircraft are operating on separate closely spaced parallel runways?

How does a TCAS system avoid unnecessary (RAs) resolution advisories when aircraft are operating on separate closely spaced parallel runways (e.g. 2500 feet or less separation between rwy centerlines)....
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Are mode C altitude returns valid for aircraft separation?

According to FAA JO 7110.65 5-12-8 'Validation of MODE C READOUT', Mode C is valid if there is less than 300 feet deviation from the pilot reported altitude. If ATC instruct 'A' aircraft to maintain 5,...
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During VMC conditions in terminal airspace (class B), does the pilots have to strictly follow separation standards issued by ATC?

Is it common for pilots to breach separation standards in terminal airspace while the conditions are VMC? I'm interested primarily in commercial aircraft that have scheduled operations in major ...
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How did lateral and longitudinal separation minima evolve?

What is the evolution in time of lateral and longitudinal separation minima?
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3 votes
2 answers
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Will there be dynamic or variable separation minima in future?

In the future, is it possible to apply in the same airspace different separations between pairs of aircraft? Depending on the relative speed, navigation capacity of the aircraft, intersection geometry,...
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How to find runway Centerline spacing on airport diagrams?

I know that airport diagrams show the exact position of airport runways in DMS (degrees, minutes, seconds) and therefore could use trigonometry to find how far apart runway centerlines are from ...
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Which avoidance maneuver is best when seeing crossing traffic on approach to a runway?

Let us say I am in final landing and I saw another aircraft is crossing the runway while I am still in air, should go around be my best choice? If I touched down and then I saw the traffic, how ...
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Are there conventions on which side to travel on Victor airways - USA?

I'm a low-time VFR pilot (100hrs) in the United States. I have not yet started IFR training (other than XC time building). I understand the purposes and reasons why the Victor airways exist. I also ...
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Is there any current and/or upcoming technology that alerts Air Traffic Controllers in case of loss of aircraft separation?

Currently doing an assignment and it to analyse an accident where older atc systems could have been at fault. In 1995 there was an incident where two aircraft came closer than the then current ...
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3 votes
3 answers
598 views

How to determine the traffic avoidance manuver?

Scenario A: I started the takeoff roll and then noticed another aircraft is crossing the runway in front of me, how could I determine what is the best avoidance maneuver, like full braking to abort ...
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What will be the immediate action by the pilot and ATC if any plane blocks the runway while landing?

Suppose, if the Airport has only one runway and one plane is trying to take off at the end of the runway and other plane trying to land from the other end of the runway. Due to any reason if the ...
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What is the FAA regulation for the 3 mile / 1,000' separation for a commercial airliner? [duplicate]

I need help finding the Number/Citation for the FAA regulation/order that states commercial airliner separation should usually be at least 3 miles laterally, or 1,000 feet vertically. I cannot find ...
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Is separation provided in class F airspace?

According to the Wikipedia page on different airspace classes, separation is provided for IFR/SVFR to other IFR/SVFR in class F airspace. In ICAO Annex 11 from 2018 (p.36 in the pdf file), I can't ...
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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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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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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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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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6 votes
3 answers
552 views

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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6 votes
4 answers
946 views

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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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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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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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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11 votes
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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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5 votes
1 answer
542 views

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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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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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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2 answers
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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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7 votes
2 answers
661 views

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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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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1 vote
4 answers
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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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5 votes
1 answer
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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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48 votes
6 answers
34k views

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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1 answer
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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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18 votes
1 answer
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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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19 votes
2 answers
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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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4 votes
1 answer
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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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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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6 votes
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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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9 votes
3 answers
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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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7 votes
4 answers
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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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3 votes
2 answers
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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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9 votes
1 answer
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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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7 votes
2 answers
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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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14 votes
1 answer
3k views

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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1 answer
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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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20 votes
2 answers
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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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4 votes
1 answer
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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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