Saturday, February 17, 2007

DCA-PHX

My poor, poor wife. The next time we fly out west, I can't imagine just how intolerable I'll be.

As you'll recall, I jumped in feet first when I bought Flight Simulator a few months back. The more observant of you might have noticed a new link over to the right - United-Virtual.com. I put my career at UPS on hiatus, opting for more flight options (by necessity, United and UVA have to offer more flights than UPS).

The downside is that UVA is more intensive, and I'm currently working on a checkride (i.e., a test) to ensure I'm capable of flying bigger and more complex aircraft. At the moment, I'm in a turboprop; hopefully soon, I'll be in command of a 737 or an A-320.

It's only been a few months since I got FS, but I've learned so much. I e-mailed loyal reader Matt Edwards yesterday, and he told me found the whole deal fascinating too. So I thought I'd share what happens on a typical commercial flight. For this example, I'll use what is often the first leg of our flights out west: Washington National to Phoenix Sky Harbor.

If you've ever flown, perhaps you've noticed the labels on your luggage and the hard-to-miss three-letter identifier. That's the FAA code for the airport you're going to; in this case, National is DCA and Phoenix is PHX. (The International Civil Aviation Organization uses four letters; in which case we'd be flying from KDCA to KPHX. The "K" simply means we're in the U.S.)

For the purposes of this example, we'll assume that the pilots have already completed their walkaround and have been full briefed by their airline's dispatchers. Dispatchers route the plane according to winds aloft and to avoid nasty weather, among other things. (And let's also remember that I'm still new at this, so I'm answering to the best of my ability but may be wrong on some minor points.)

So now, the pilots are in the flight deck. Their first radio call will be to airport's clearance delivery. Clearance gets the flight in the system, so to speak, so that everyone along the way knows where this plane is going and how it's going to get there. Clearance may also give special instructions concerning departure.

Once the pilots have read back their clearance instructions, they'll push back if they haven't already. During push back, they'll make the final adjustments, start the engines and prepare to taxi. Once they're ready to taxi, they'll contact ground control. Ground control is in charge of all ground-based movements at the airport, with the notable exception of the active runway(s). (Larger airports, such as JFK in New York, may require pushback clearance as well.)

Ground tells the pilots what runway they'll be using and how to get there. The pilots will have maps of the airports, but can also get directions from ground, if they won't be overwhelmed.

The pilots give a little boost to the engines, and the taxi begins. (One member of our board of directors at UVA is a real-world 747 pilot. She once noted that on the longest of flights, say JFK to Hong Kong, the aircraft will be pushed to the runway. Using any fuel in taxi would cause them to land with less than minimum fuel amounts.)

But this plane isn't the only one moving around. Ground may tell our pilots to yield to other aircraft turning onto the same taxiway. Once we're fully in sequence, ground will hand us off to to the tower - "Monitor tower on 1xx.xx." When we arrive at the runway, we'll notify tower that we're there and ready to go.

We'll get one of three responses: hold short (stay where you are; most likely, an inbound plane is about to land), position and hold (enter the runway but don't take off; the inbound or outbound plane is no longer a factor at our end of the runway) or cleared for takeoff.

Eventually, we'll get takeoff clearance. We taxi onto the runway (if we're not there already) and make sure we're lined up with the centerline. The pilots push the engines to 70 percent with brakes on, to make sure we'll be rolling straight (we move forward slightly); when they're happy, they cut the brakes and push the engines up higher. (Pilots often use a "derated" takeoff, where they won't use all of the power available to them. This saves gas and wear and tear on the engines.)

The passengers are pushed back in their seats as the plane begins to roll and accelerate. Based on weather, weight and other conditions, the pilots have three speeds to watch out for. They'll pass V1 first, which is decision speed. If a pilot wants to abort a takeoff, he/she must do so before this speed to ensure there's enough runway left to come to a safe stop. The next is VR, rotation speed. At this point, the pilot tilts the nose up and lifts off the ground. Lastly is V2, an airborne speed known as "maneuvering speed."

We hit VR, the pilots rotate upward and the plane takes off. Once they've confirmed that they're off the ground, they'll retract the landing gear. At about 1,000 feet is an extremely busy time. They'll cut back on the engines to observe certain airborne speed limits; they'll retract flaps, which are used to help get the plane off the ground; they'll tilt the nose down slightly and make a slower climb to cruise altitude; and the tower will tell them to contact departure control.

Not long after, we'll start making a turn to join a standard departure pattern, called a SID (standard instrument departure). DCA doesn't have any SIDs, so chances are, clearance delivery will have told us which way to go. Departure can amend that, however, with a vector, which is any unscheduled change to the flight plan.

The next major change will come when we reach 18,000 feet, known as transition altitude. If we took off at night, we'll turn off some of the exterior lights that we won't need. But transition height gets its name from a change in the altimeter, our on-board height indicator. The pilots will change the altimeter to a standard rate that applies to all aircraft at 18,000 feet and above. The reason for this is pretty simple: a pilot that takes off from Denver might reach 18,000 feet, but they'd be at 23,000 feet over Washington. (Incidentally, once you reach transition, altitudes are abbreviated. We won't cruise at 36,000 feet, but we'll cruise at flight level 360. Twenty-thousand feet is flight level 200, etc.)

By now, we're well over the western exurbs of Washington. We'll follow jetways - think of them as freeways in the sky - to head west. We'll be aided by GPS and certain other radio and non-radio navigational aids. And around this time, departure will transfer us to a regional control center. As you can see in this map, we'll start out with Washington Center (ZDC). Halfway across West Virginia, we'll transfer to Indianapolis Center (ZID). Once we're into Illinois, we'll be handed off to Kansas City Center (ZKC) and into Colorado, we'll contact Denver Center (ZDV). As we make the turn south to Phoenix, we'll talk with Albuquerque Center (ZAB).

(In case you're wondering, the other centers are: Boston, New York, Atlanta, Jacksonville, Miami, Houston, Fort Worth, Memphis, Chicago, Minneapolis, Salt Lake, Seattle, Oakland and Los Angeles.)

Just as we had a SID to give us a uniform way to leave the airport, we have a standard way to arrive at our destination, called a STAR (standard terminal arrival route). Basically, this takes traffic from all directions and funnels into a few directions to ease the workload (and stress) on the air traffic controllers. Since we're coming from the north, we'll likely use the BUNTR One arrival. (BUNTR is a navigational point along the STAR; "one" is simply the number of times this procedure has been changed.) You can see a map of BUNTR One here (it's a PDF).

From the north, we'll fly over Winslow and due south towards the navpoint JESSE. When we cross JESSE, we should be at 12,000 feet. (We'll have started our descent long before we get here.) After JESSE, it's on to GUMMO and EAGUL. At EAGUL, we'll make a slight right-hand turn and descend to 10,000 feet. From there, we'll pass PICHR, DBACK, HOMRR and, finally, BUNTR. (Notice a trend? Perhaps a tribute to Phoenix's MLB team? This was the subject of a column I did a few weeks ago; you can find it here.) By now, we'll likely have been handed off from ZAB to Phoenix approach.

Of course, there's a chance we could be vectored off before we ever reach BUNTR, depending on what runway we're assigned to. If we have to land from the west, we'll have to bail out of the STAR for a different approach, and approach control will tell us this.

They'll put us on an approach path at 45 degrees or less to the runway. That way, we can pick up the radio signals from the runway, collectively known as ILS (instrument landing system). There are two components: the glideslope, which tells us our path of descent, and the localizer, which gets us on the runway centerline.

We'll make a turn to intercept the localizer and get ourselves lined up. Eventually, we'll cross the glideslope as well, around 6-7 miles out. By this time, we'll be in touch with Phoenix tower. When it is able, tower will give us landing clearance.

By the time we begin our final approach, we'll have landing gear down and flaps fully extended. They'll help us slow down enough to make a safe landing. (The gear also helps slow us.)

We get landing clearance and we're good to go. When we're 200 feet off the ground, we're at decision height. If it were really, really foggy, we'd have to see the runway by this point; otherwise, we'd have to accelerate, ascend and try again. At DH, we may turn off the autopilot (in certain circumstances, like gusty winds, we'd have to turn off autopilot) or allow the plane to use its autoland feature.

At 50 feet off the ground, we'll pitch the nose up slightly to ensure that the main landing gear touches first. This is called a flare. The main gear touches, and we bring the nose down too. But we're still going way too fast.

Instead of trying to describe it alone, check out this video and I'll walk you through it. (You can skip the first 1:25.) At 1:52, just after touchdown, you see part of the wing pop straight up. These are called speedbrakes, and will help slow us down. You'll also hear the engine roar; it's not really reverse thrust per se, but it also helps. The pilots also use autobrakes, which work just like those on a car. (The autobrakes deploy automatically on touchdown, and can be preselected to various levels of intensity, depending on the weather and the weight of the aircraft.)

To save wear and tear, we'll cut the reversers off at 60 knots, and we'll bring the speedbrakes down too. By that point, we'll just about be at a safe enough speed to turn off the runway, and tower will hand us off to ground. They'll tell us how to taxi to our gate and, like before, it we need to give way to other aircraft that are also taxiing.

Whew. That was a lot longer - and took a lot longer - than I would have thought. If I bored you to tears, I'm sorry. (But blame Matt.)

At least one positive came from it: I can just hand this to my wife and she won't have to listen to me blabber on for three and a half hours.

2 comments:

ME said...

Hey, I'll take the blame. That was very interesting.

At least now I know that I could never, ever fly a plane, real or virtually. Wow, that's in-depth.

V1, VR & V2. Are those signs on the sides of the runways? They seem familiar.

Your column on the navigational aids & sports references was very cool.

As an aside, do you know of an RSS feed for your column?

Thanks boss! I hope you graduate to the big boys soon! Thanks for sharing.

Brian said...

V1, VR and V2 are collectively referred to as V-speeds. V1 is decision speed, VR is liftoff speed and V2 is maneuvering speed. Sorry if I didn't make that clear, big guy.

The signs you see are just directional signs. They'll tell you what you're on and what's ahead. Letters that are yellow with a black background is the taxiway you're on; letters that are black with a yellow background are taxiways you're intersecting; and red-and-white numbers indicate you're crossing a runway. (Chances are you'll have to stop and receive clearance from ground to cross it.)