Q for pilots about comercial airliner landing

[scottmandue]

A few years back I picked up my wife at LAX in the evening and I got on the 105 freeway that parallels the airport and the path of the huge airliners coming in for a landing. Looking straight at them with their lights on you could see for a good twenty miles or more. They seem to be hanging motionless in the sky, five or six of them lined up. My wife asks "how do they hang out like that?" my man brain starts whirring {airfoil+movement=bernoulli} but then we were both tired and I just said "honey they are moving". I was about to say "a couple hundred miles an hour" but then looking right at them... just hanging in the sky like that... I cut myself off because I honestly don't know how fast they are coming in. I'm sure it varies by airplane but generally how fast is a big airliner moving on the final approach?
TIA

[Joe Bob]

Landing speed for a 747 is a little above 160mph. So, that plus glide rate.......figure 200+ on approach. I'm seeing 115 for a stall.....warning alarms screaming at 125.

[Nostril Cheese]

I used to live right on the hill in Gundo overlooking 25L/R. Those planes do appear to come in pretty slow.

[TheMentat]

Windy day perhaps? All of the speeds Joe Bob is listing are air speed, so ground speed could come down significantly with a big headwind

[HardDrive]

Your whole post is testament to the just how bright the lights are on a modern jet aircraft. The illusion of hanging comes from you being able to see them from a long way away, and the fact that they are all following the same glide path. At 180 mph, it takes a plane 8 minutes to travel 24 miles, and I'm pretty sure you can see them that far out on a clear night. If you're near the runway, their relative angle to you stays pretty much the same until they are very close. So they appear to 'hang' until they are very close.

[Porsche-O-Phile]

I know exactly the phenomenon you're mentioning - LAX is a great airport precisely because the visibility is often so good so you get that perception a lot. As has been said, it's airspeed that matters and as a general rule they'll always take off & land into the wind (helps reduce ground roll, etc). IIRC LAX won't "turn around" until it's a 7+ knot tailwind component. This is to to keep the preferred operational direction to the west. Less noise, etc. A pilot can always refuse that and request whatever runway is desired but 99 times out of 100 they'll play ball with the controllers and the agreed-upon operational restrictions worked out with the local yokels.

Inside the FAF (final approach fix) you want a stabilized approach - aircraft in landing configuration, slowed to approach speed and no significant control inputs or changes to power. The FAF for an ILS approach (used most often at LAX or approximated on a visual) is glideslope intercept. Since they keep the big boys high for noise over the basin that's a long way out - can be 20-25 miles. So they'll dump the gear, flaps, etc. and get dirty way out there and line up in the queue. I think required entrail spacing is 2 minutes unless you're dealing with heavies or actual IMC (forget offhand it's been a while and one of the controllers on here can correct me if I'm wrong).

Figure a +/- 150 knot ground speed on final (give or take) is 2.5 miles a minute. 2 mins separation between aircraft is 5 miles. So on those nights you're seeing them lined up 5 or 6 back you're seeing them about 25 miles out and about 10 minutes from the runway. When something is coming towards you there's no sense of movement / parallax so it seems to stand still especially if it's on a straight path for 10 minutes so yea it looks like they're standing still even though they're definitely motoring along towards you.

When learning to fly at night one has to keep their eyes moving. If you see a lighted object moving that's a possible hazard. If you see a lighted STATIONARY object that's a very likely hazard!

[rattlsnak]

A smaller airplane will look like its moving twice as fast as a large airplane when moving at the same speed. Its a phenomena based on the size. Your eyes judge speed on how far something moves in a certain time frame. A bigger airplane appears to takes twice as long to move the same distance as a small airplane because we base this on how far the the plane moves times the length of its body. or something like that.. lol..

[Joeaksa]

The above post says a lot.... I am back to flying the smaller Learjets now (Lear 60XR) and we have a ref of 140 knots which is just a bit over 160 mph. This is our minimum speed on final but we can add a bit to it depending on winds and so on....

The bigger birds have better wings with lift devices that allow them to fly slower in the landing phase... and their size makes them look like they are standing still...

[scottmandue]

Okay, so my uneducated guess would have been to say "around 100 to 200 mph" which would not have been too far off.

[74-911]

Originally Posted by Joeaksa

........The bigger birds have better wings with lift devices that allow them to fly slower in the landing phase... and their size makes them look like they are standing still...

C-5's on approach absolutely look like they are barely moving if not standing still. One expects them fall out of the sky at any moment.

[dave 911]

Originally Posted by 74-911

C-5's on approach absolutely look like they are barely moving if not standing still. One expects them fall out of the sky at any moment.

So true! When I was in flight school in Beeville TX our apartment was in the flight path of the base, and the C-5's used to come down to shoot GCA approaches (Navy bases had them, I think AFB's didn't). They flew directly over our apartment at a couple hundred feet altitude, with everything hanging out - landing gear, full flaps, and they looked like they were flying at 10 knots...it was like a total eclipse when they flew over -- cool as hell....