What makes a visual approach quicker than an ILS approach?

Question

In the question What's the preferred approach for a passenger jet? it is mentioned that pilots prefer Visual Approaches over ILS Approaches, as they are a lot quicker.

Why would a visual approach be quicker than an ILS approach?

Answer 1

Visual approaches can be conducted from any point around the airport where the runway is in sight, e.g. if you are approaching from the north of the airport, you can be vectored to a position which is closer to the airport and be cleared for a visual approach from a position where you can turn visually and reach the runway threshold.

ILS approaches begin at the approach gate before the final approach fix (FAF) for the localizer and glidepath indications to be correctly used and the aircraft configured for the approach. The FAF is at many airport around 10 NM from the runway threshold at 3.000ft AGL, thus placing the approach gate at around 12-14 NM.

A pilot on a forum has summed it up like this:

Visual approaches are usually shorter than instrument approaches. By that, I mean that the turn to final is accomplished closer to the runway when on a visual approach.

When traffic is heavier, or weather is around, or it's hazy, smoggy, etc, ATC will usually route everyone out for an ILS.

Many times, a pilot will call runway in sight, yet be sequenced behind someone who is on the ILS. So, he'll get routed out for an ILS approach, even though he'll go visual within the cockpit.

Airport size doesn't have a whole lot to do with it. Also, even though an aircraft may be on a visual approach, that does not absolve ATC of separation resposibility.

^{(Source: www.airliners.net - Author: Tom in NO)}

Effectively, this means that visual approaches tend to be shorter and quicker than ILS approaches with vectors to the FAF/approach gate.

Answer 2

At the risk of just repeating information from the great answers that SentryRaven and casey already gave, here's a real example.

Last night I flew the ILS 22 into KLEX for practice, although conditions were perfectly clear and most aircraft were using a visual approach. If it had been a 'real' flight and not practice I would certainly have taken the visual as well because it would have saved almost half an hour of flight time (and fuel):

• I was inbound from the west and ATC started vectoring me when I was still more than 10 miles from KLEX to get me onto the ILS approach. They sent me northeast, east then southeast to intercept the glideslope. That means that instead of just flying 10 miles directly to join the pattern, I was vectored for almost 40 miles. Normally, you just don't want to use up that much time and fuel if you don't have to. Unfortunately I don't have track data from the flight but it looked roughly like this; even if you aren't familiar with the chart you can probably see how using the ILS required a huge diversion. The pink line is my route and the red arrow shows where the vectors started:

• I was cleared for the ILS while about 10nm from the runway. But the winds were very high, and instead of having a ground speed of 80 or 90 knots (in a C172), I had a ground speed of 50. That meant I took about 12 minutes to land, which effectively blocked the final approach course for that amount of time. A faster aircraft on a visual approach was turned in behind me and had to do S-turns on final to avoid getting too close. If I had been on a visual approach instead, I would have been in the traffic pattern very close to the runway and would have spent just a minute or two on final.

It's also worth noting that apart from flight time, another reason to prefer visual approaches is that a pilot (a private one, anyway) has a much lower workload. You don't have to brief the approach, set up your nav equipment (and maybe autopilot) etc.; instead, you just look outside and fly visually.

Answer 3

Visual approaches are preferred because it means you can potentially avoid being vectored out to intercept the final approach fix (FAF) which needs to be done for a an ILS approach. If there is a long line of aircraft being vectored for the approach this may not yield any time savings as minimum spacing with the aircraft in front of you becomes a factor. At an airport that isn't busy this can be the difference between flying a tight traffic pattern and landing quickly or a long vector 5+ miles past the airport to join the approach.

Also, being on a visual approach clearance with the aircraft in front of you in sight relieves the controller from providing normal spacing. This means you can squeeze a bit closer to the airplane you are following and you just have to make sure you are keeping far enough back that the runway will be clear when you get to it. This can also help if the airplane in front of you slows down unexpectedly or too early, which if you are on an non-visual approach could result in S-turns for you or a missed approach. In these cases the controller often asks if you can see the aircraft so you can be given the visual clearance and manage the spacing yourself and avoid going missed.