A question (or two (or three))...

On the diagram below, I live just about mid-way between the downwind leg and base leg. Usually, (when the active runway is east - west) I've noticed approaching commercial aircraft take the base leg past the end of the city, almost over the mountains. Have also noticed that the larger aircraft (777, 747) almost always pass the end of the subdivision, housing area, where they make their "base leg" turn - which is just over 10 miles to the runway.

A common occurance, is the smaller ones (southwest 737s) cut over "earlier", and while it's not very loud, you can hear them when they cut and fly most times directly overhead, or near abouts.

In my mind, I figure / realize that they are sometimes directed to cut early because there is another aircraft "coming in straight", instead of taking the downwind leg. But I have also noticed that there isn't always another one coming in straight, and they seem to me to just be cutting early to save time.

Since it seems to me the larger aircraft are following the rules, are the smaller ones who cut early not following the rules?

Not really an expert, I used to do flight planning for business jets. Have you looked at the approach plates?

https://flightaware.com/resour...port/KLAS/procedures

quote:

Since it seems to me the larger aircraft are following the rules, are the smaller ones who cut early not following the rules?

IANAP, but isn't "following the rules" doing what ATC tells them to? I suspect this is part of the planning that takes place long before the planes are in that short of range.

Approach plates don’t show the visual approach pattern of downwind, base and final.

A lot of the distances depend on speeds and aircraft size. The pattern for a 747 or C5, for example, is going to be much bigger than for a Cessna 172/152, both lengths and heights.

There are rules of thumb for each aircraft. Flying a pattern in a 172 is a bit different than in a Mooney Encore, and both are different than a Piper Malibu, all of which are somewhat different in a Cessna twin.

I imagine that a 737 flies a different pattern than a heavy.

The idea is to get lower and slower so that when you turn to final, you are at the proper altitude and speed given your distance from the runway.

quote:

Originally posted by Georgeair:

IANAP, but isn't "following the rules" doing what ATC tells them to?.l.

If your field gets 737s and 777s I'm certain there's a tower (and approach as well). Even in my puny Cessna 152 I do what ATC tells me! Straight in, right pattern, whatever.

That chart with the standard left hand pattern applies more to non-towered fields.

It's rare, in airline operations, to fly a traffic pattern at an airport. Arrivals are handled via instrument procedures called STARs or AP's; Standard Terminal Arrival Procedures, or just Arrival Procedures. San Fransisco also has several visual arrivals.

The Point Reyes 3 Arrival flies a very large pattern that would be well away from the airpor, but does make a large, long downwind and base. Arrivals from the north, such as the STINS 3, come from Point Reyes VOR, arrive just west of San Fransisco over the water, and are vectored...which can place them on a downwind of sorts.

San Fransisco has two visual approach procedures called the TIPP TOE Visual for Runway 28L/R, and the QUIET BRIDGE Visual, for the same runways. These approach over the the south end of the San Mateo Bridge, straight in to the runways. They also coincide with the instrument approaches to those runways.

The size of the pattern or flight path depends on aircraft speed, and where ATC (air traffic control) assigns the vectors, or turns. The approaches into KSFO are from the direction of the Dumbarton bridges, to the runways, for the best noise abatement.

Typically on a downwind, we'd be 250 knots slowing to about 230. At a base position we'd be beginning to configure for landing, slowing through 200, and by the time on final and fully configured with gear down and landing flaps, about 160-180 knots. (a knot is 1.15 mph). Maximum bank in those conditions will be 25 degrees until on final, when it's much less, which means that turns are fairly wide, with no hard turns. You can imagine that a turn at these speeds takes a certain amount of room. It's also a matter of a steady, controlled descent; the altitude is kept higher above populated areas until necessary to be lower for landing, which also means extending out past the populated areas in the descent. The actual patterns, turn points, etc, are something determined and set in stone for the most part as published procedures that each flight crew member is following on the arrival, and approach to landing.

There is no "cutting early to save time." Air Traffic Control determines when and where the turns take place. The distance and turns are generally predicated on maintaining a 3 degree descent slope on the arrival, as well as taking into account terrain and other factors. If one is high, turning early to save time would mean a higher rate of descent, and each flight is also governed by what is called "stable approach criteria." Once on final, this includes, among other things, a descent rate no more than 1,000 feet per minute. An early turn and rush to the runway to "save time" would be contrary to the nature of a stable arrival, and would be considered unacceptable.

Turns are generally made to coincide with arrival on the final approach course on the electronic glide path to the Instrument Landing System. KSFO has parallel instrument approaches to Runway 28L and 28R, which include reduced separation for qualified crews and aircraft. The runways are close together and standard spacing between arriving flights can be reduced with the use of precision radar monitoring. The nature of arrivals does not permit shortcuts for time. At seven and a half miles from the runway, arrivals start at 1,800' above sea level and proceed to the runway at a 3 degree glidepath, following an electronic glideslope signal. Deviation from that signal is not authorized and is grounds for a missed approach or "go around." This is a safety issue and not something crews can or will compromise.

Light aircraft arriving are not necessarily constrained by the same operational requirements and will be directed by Air Traffic Control accordingly.

I wouldn’t call it rare to fly patterns in airline ops. It certainly is at some airports, where runways and arrival departure factors make it less desirable, like John Wayne or San Diego, but I have flown patterns in airliners, as a passenger, often enough to think it is not particularly rare. Phoenix, DFW, Bush Continental, El Paso coming from the west, among others.

It may be that the STAR in these cases or getting to the initial point involves a route which resembles a big pattern.

This is an international terminal (KLAS). I see the 737s taking the "long way" like the 777s and 747s, and now and then, they cut short, sometimes they really cut short - that they are flying west northwest to merge into the westerly final.

A traffic pattern in the way depicted, such as a light airplane might fly, is rare for an airline arrival. Arrivals with vectors may look like a pattern, but are not. Typically the last vector to the final approach course is thought of as a "base" leg, and if the arrival has been from the opposite direction as landing traffic, the vector prior to that is typically what might be considered a "downwind," but it's not the same as a downwind leg in a traffic pattern.

A visual downwind, base, and final is very rare. Phoenix is such an example. If arriving opposite direction, all traffic is getting routed to the runways, and the routing approximates what one might think of as a "downwind," but it's not, and such vectors can be from any direction or to any waypoint.

A light airplane enters the pattern in coordination with the tower (Xray Papa Ringworm Bubblesnot, enter left downwind runway two-six abeam the tower). An airline aircraft is still taking to approach and is on a vector (YabbaDabbaDo Two Six Seven, turn right heading 090, descend and maintain four thousand). It's a vector.

quote:

Originally posted by f2:
This is an international terminal (KLAS). I see the 737s taking the "long way" like the 777s and 747s, and now and then, they cut short, sometimes they really cut short - that they are flying west northwest to merge into the westerly final.

That's a vector to final, to sequence aircraft. What that means is that the controller has given the aircraft a heading to fly until established on the final approach course, and it's being done to arrange the aircraft in order for flow and spacing. This is done to allow for necessary spacing due to wake turbulence, different approach speeds, and time on the runway.

When you titled the thread, you said "sf." Did you not mean San Fransisco?

Think he meant Sig Forum - no San Fran...

what you have is dissimilar aircraft in the same area which have obviously dissimilar performance requirements.

for example if you're flying at 90 knots and want to do a 500 foot per minute decent for a nice touchdown on the runway, the distance for a downwind-base-final turn is going to be a lot less than if you're flying at 175 knots.

Also light aircraft have a pattern altitude of 1000 AGL so to descend 1000 feet at 500 fpm needs 2 minutes.

Its timing. The distance covered in two minutes at 90 knots is a lot less distance than 2 minutes at 175 knots or 135 knots.

quote:

Originally posted by SBrooks:
Think he meant Sig Forum - no San Fran...

Ah. Normally when I see SF, first thought is "special forces," but that didn't seem to fit.

Sig Forum should have been obvious, I guess.

edit: missed this:

quote:

Originally posted by sns3guppy:
When you titled the thread, you said "sf." Did you not mean San Fransisco?

SIGforum. Airport is KLAS (McCarran).

quote:

Originally posted by f2:

The above image is deceiving as there is no upwing leg or crosswind leg, as they are depicted in the diagram - all I see is aircraft lined up in the downwind leg - at night, when busy, you can see half a dozen or more at various altitudes, all heading for their base leg turn and final - which is around 10 miles, when the active runway is east - west (heading west to land).

This message has been edited. Last edited by: f2,

At the busiest of airports no one is really flying the pattern depicted in the runway diagram. Yes, it’s controlled by ATC with planes sequenced in from various arrivals.

Planes usually end up 10 miles in trail on the arrivals, that distance becomes 5, then ends up about 3(2.5 minimum) on the 10 mile or so final. That distance is increased behind a ‘heavy’ that has a higher potential for dangerous wake turbulence.

There are exceptions to most every rule, bad weather may need additional spacing. Even if one was to fly a visual approach or pattern, one usually maneuvers to the final portion of an instrument approach. That’s a good way to stay out of trouble.

The depiction is what is taught in private pilot training on proper entry and departure procedures for uncontrolled air fields. If everybody does things the same way, it is safer to see and avoid.

In busy terminal areas with a control tower, a VFR traffic pattern is rarely used. It may look like they are flying a pattern, but usually are just being vectored by ATC. In VMC conditions, typically, you will be cleared for a visual approach which then allows the pilots to choose heading, speed and altitude at their discretion if no other ATC instructions are given.

When being vectored for an ILS, intercept angles are generally around 45 degrees or less and happen around 7-10 miles out.

quote:

Originally posted by sourdough44:
At the busiest of airports no one is really flying the pattern depicted in the runway diagram. Yes, it’s controlled by ATC with planes sequenced in from various arrivals.

Planes usually end up 10 miles in trail on the arrivals, that distance becomes 5, then ends up about 3(2.5 minimum) on the 10 mile or so final. That distance is increased behind a ‘heavy’ that has a higher potential for dangerous wake turbulence.

There are exceptions to most every rule, bad weather may need additional spacing. Even if one was to fly a visual approach or pattern, one usually maneuvers to the final portion of an instrument approach. That’s a good way to stay out of trouble.

Even at far less busy towered GA airports, a full pattern is uncommon. Sometimes, the tower will respond to “enter a right(left) downwind, cleared to land runway XX” or “cleared for a straight in to runway YY, follow a Bonanza now on 3 mile straight in, report that traffic in sight,” etc.

One of the factors a pilot must acquaint himself with is what to expect at an airport you intend to land at, especially if there is no tower. Usually, wind and runway alignment makes particular routines customary, but winds change, traffic may dictate something else.

The picture is a basic VFR (visual flight rules) traffic pattern. Aircraft operating under IFR don't fly traffic patterns. Airline aircraft fly instrument approaches; published procedures using ground and airborne navigation systems to guide them to a runway. When in the terminal area, typically within about 25 miles of the runway, the aircraft are either arriving on a published STAR, or on a routing to the approach, or being directed (vectored) by air traffic control.

Navigation systems today are very precise; it appears that aircraft on a given arrival all fly the same track and are often lined up perfectly because of the navigational precision. When you see them coming from different directions, they're on different arrivals, coming from different places. Ultimately, aircraft for one runway are usually sent to one of several marshalling points.

Runway 26R has a final approach fix (FAF) of CONDY at 7.6 nautical miles, and an altitude of 3,800. Traffic will join the final outside the FAF with adequate time to complete their checklist and configuration prior to starting down the electronic glideslope. The next fix outside CONDY is HAWKO at 12.7 miles and 5,400'.

runway 26L has a FAF at RELIN, 7.2 nm and 3,800'. Next fix outside RELIN is SHAND, at 10.8 nm and 4,900'.

The opposite direction runways, 8L and 8R, do not have approaches.

One of the busiest arrivals, coming from the southwest, drops traffic at CLARR intersection at 250 knots and 13,000. From there traffic is vectored to the landing runway.

Traffic arriving from the northwest on the SUNST 4 arrival crosses Boulder City VOR and goes east toward Boulder Dam before turning a descending base and final, then drops off at PRINO, the start of the ILS approach to runway 26L. The pattern is arranged with a squared off base downwind and base, after a fashion, and intercepts the final approach course at 8,000 just southwest of the Boulder Narrows by Lake Mead.

The KEPEC 6 has a similar path to final.

quote:

Originally posted by sns3guppy:
Traffic arriving from the northwest on the SUNST 4 arrival crosses Boulder City VOR and goes east toward Boulder Dam before turning a descending base and final, then drops off at PRINO, the start of the ILS approach to runway 26L. The pattern is arranged with a squared off base downwind and base, after a fashion, and intercepts the final approach course at 8,000 just southwest of the Boulder Narrows by Lake Mead.

The KEPEC 6 has a similar path to final.

As to east toward Boulder Dam, does it specify how far east they have to go before turning west and straight in land? If that's the westward landing approach I'm talking about.

explain STAR, FAF, CONDY, HAWKO, RELIN (I think most of those are points / locations? except for STAR and FAF).

And what is KEPEC 6?

I sit on my porch facing west, so I see the (from the diagram (which is backwards to my situation that I'm talking about)) downwind leg coming toward me on the left, and then they turn behind me (most times) and make the turn to the west to straight in land.

f2, crumble up that paper showing the pattern. It really doesn't apply to KLAS. Go here and listen to ATC. You should get a better idea of the way it works by listening to aircraft/ATC.

https://www.liveatc.net/search/?icao=klas

How far east they go depends on whether they fly the full arrival. In the case of the arrival I described, I also described the area they're turned back; just south of the Boulder Narrows, if you know where that is.

STAR, as previously explained, is a Standard Terminal Arrival Procedure. FAF, as already given, is the final approach fix. A fix is a point in space that exists at a specific geographical location over the ground, and sometimes a specific altitude. The final approach fix, is a point at which the electronic glideslope (a beam broadcast from the runway that forms a guidance path down which aircraft fly to the runway) intersects the geographical fix at a certain altitude. It's usually the last fix on the approach until the aircraft arrives at a minimum altitude close to the runway.

Names such as CONDY, HAWKO, and RELIN are fixes.

KEPEC 6 is an arrival procedure; it's a STAR. Procedures, whether arrival, departure, or approach procedures are published diagrams that spell out exactly what altitudes and fixes an aircraft must pass through when departing or arriving at an airport. There are numerous procedures at most busy airports, including KLAS (McCarren).