How many ways to land an airliner (safely!)

[Maxbert]

After reading through the Ryanair incident Ciampino thread in the R&N forum, I am wondering how many ways there are to land an airliner at any given airport?

From the mentioned thread, I gather that companies specify a number of procedures / rules which must be followed, and I also assume that the surroundings play a big part-

That being said, is adherence to set glide paths / approaches always mandatory, or do pilots have a degree of leeway as to their approaches, under normal conditions?

Thanks,

Maxbert

[SNS3Guppy]

If there's a published instrument approach, we fly it, day or night, instrument conditions, or visual. I can't speak for others.

[Maxbert]

SNS3Guppy

Thank you! :ok: Does this mean that airports set the criteria, or airlines? I suppose it also depends on aircraft, that is commercial / private, and avionics?

Sorry, just SLF here, a very few notions gleaned from PPRuNing :ok:

[Maxbert]

To clarify my initial question:

Does one have to be at a particular height and speed for a given distance from a runway or, again given non-emergency conditions, does a pilot have discretion as to this, apart from traffic / location constraints?

I think I know what question I'm asking, really...

[pilotmike]

This is a very simplified treatment.

In general all aircraft would follow the correct localiser (left and right) and glideslope (up and down) at the appropriate speed for its weight and flap setting. The localiser and glideslope is effectively defined by the ILS, a radiating radio beam which guides the aircraft down (either through instruments, autopilot, or both). There is also a PAPI, a visual 'precision Approach' aid which shows two red lights and two white lights when you are correctly on glideslope. More reds show that you are too low and more whites show that you are too high.

As the glideslope defines your height for any distance from the runway (about 900 feet for every 3 miles away on a standard 3 degree or 5% slope), yes, we stick these heights. Indeed, we use these specified heights and distances to check that the ILS is giving us the correct glideslope.

Having followed the localiser and glideslope, at a height which is specified by the manufactured for the specific type, but around 30 to 60 feet, a flare is initiated to reduce the vertical speed at touchdown, along with reducing thrust. This flare technique is specified for each type as it varies considerably from type to type.

Crosswinds present another set of issues to deal with which I won't cover here.

[Maxbert]

pilotmike,

Many thanks to you as well:ok: I realise that my initial question is more complex than I thought... :ugh:

I think that what I am getting at is this:

I assume that commercial transport operating from commercial airports has to follow specific rules insofar as approaches go, flights are channeled into "lanes" to keep everything flowing (a bit like roads...)- Yes?

I suppose my question is really this: Given a totally empty sky, and assuming that visibility is fine and wind is zero (also I suppose VFR), do the laws of physics / aircraft manufacturer's spec dictate a specific, rigid approach, or can I initially be too low / high / fast / slow and correct "later", yet still land within tolerances (if any)?

How and why do airine companies' procedures influence this, if at all?

Maxbert

[NudgingSteel]

The answer to this is so huge and technical I can't face going into much detail!!!! Briefly, the bigger the aircraft, the less manouverable it is and the more vital it is to land at the correct speed at the correct place on the runway. A 747 on a 3000-metre runway has very little margin for error - just a few knots too fast might lead to an overrun. A small, slow Cessna 152 is much more nimble and can land on about 400 metres, hence they have a couple of thousand metres spare! The 152 is quite 'draggy' and when the throttle is closed, the aircraft will slow down quickly. The 747, being heavy and aerodynamic, doesn't slow down as quickly so the speed has to be managed much earlier and more accurately.
Most companies require an airliner to be stable (wheels & flaps down, right height, right speed etc) by 500' or 1000' above the ground (that's roughly 1.5 to 3 miles from touchdown on a normal 3-degree glidepath).
The most extreme example you'll see of heavy aircraft manouvering at low level is probably the approach to the old Kai Tak airport, but that was a unique thing and very difficult indeed. Generally speaking, the slower and lighter an aircraft is, the more they can correct from a high/low/fast/slow approach safely. The bigger they get, the more gentle the manouvering has to be. In am emergency the pilot can pretty well do whatever they need to to land safely, although in most cases a stable approach (as above) is the preferred option. Can't comment on the Ryanair incident as I know very little about it.

[SNS3Guppy]

Max,

Government and international organizations establish criteria for airports and instrument procedures. If one flies a published instrument procedure, it's gauranteed to meet certain requirements, such as obstacle clearance by so many feet, obstacle protection, etc. Some procedures are designed strictly around obstacles, others around obstacles and noise abatement.

Aircraft not flying by instrument flight plans aren't under the same restrictions and often don't fly these procedures. Most airline and corporate aircraft fly instrument rules and procedures...but some aircraft don't.

I've done a lot of flying involving firefighting and other such things; in these cases we often never climbed to the altitudes that an airline operation flies, and consequently we also didn't fly instrument procedures. We were often loud, low, and not in places that people on the ground might expect.

Presently I'm in a 747, and you can pretty much plan on where we'll be within a foot or two; same altitudes, same flight patterns every time.

Each airport will have instrument approaches prescribed which guide an airplane by various means to the runway. These approaches will have very specific altitudes over certain points above the ground, and very specific courses to fly. Each airport also has arrival and departure procedures that do the same thing. The arrival and departure procedures, known generally as SID's (standard instrument departures) and STARs (Standard Terminal Arrival Procedures) are designed for obstacle clearance, traffic flow, and for noise abatement...the impact that airplanes have on the environment beneath them.

Most of us, regardless of what we're flying, try very hard to abide by a good neighbor policy. It's in everyone's interest to fly as quietly as possible and to minimize impact. It's easy on the ears down below, and it eliminates needless regulation changes that restrict flight operations when people decide they've had enough of the noise.

[Northbeach]

Maxbert,

Most of the time we do have degrees of leeway as to the way we fly our approaches. There is an exception when we do not. When the visibility is extremely poor and we are forced to conduct an autoland operation. That is where the pilots take a monitoring role over the automation that actually lands the beast. During those low visibility conditions the airplane will be at a specific altitude, configuration and speed. Those constraints will be dictated by the instrument approach, government regulations and company policy and there is virtually no wiggle room. Things must go exactly as scripted.
When the visibility is better but not visual conditions the pilots may be hand flying the airplane while conducting the instrument approach. The altitudes the airplanes fly will be the same but the speeds and configurations will be a little different depending on pilot technique and comfort level.
When the visibility is good and air traffic control is sequencing the flow then we have less leeway as the controller will expect us to be on the speed and at the altitude that they assigned. A “typical” profile will have us 1,000’ above the ground for every 3 miles away from the landing airport. So if we are 30 miles away we will be about 10,000’ above the airport.
Let’s say the “tower” isn’t in operation and the visibility is good then we have wide latitude. I’m not going to be doing any “buzzing” but I will make sure my passengers get the best view and finest experience given all the other regulatory constraints I am obligated to comply with.