Wake Turbulence: Part 1 - What is it?

A while back (more specifically, a couple of months ago), a reader sent an inquiry about an airborne wake turbulence encounter that they experienced on a flight inbound to LAX:

Thanks for this great blog. A question for you: I was on an Alaska Airlines Flight from CYVR to LAX on Sunday. We came in from the coast and headed east with LAX to our south. We expected to turn south to line up for landing, but then we rolled/banked suddenly to the left (north) what felt like 45 degrees, eliciting gasps from everyone on board. The plane felt like it was out of control at that moment, but then it leveled off. A few seconds later, the same thing happened again. After we leveled off a second time, the pilot announced that it was “wake turbulence,” and immediately banked hard to the south, then seemed to come in for a much faster than usual landing. I fly a lot and have never experienced anything quite like this. I’m curious how common this is, how serious a situation it is, and whether “wake turbulence” is just one of those things, or a hazard that could have been avoided.

(Photos borrowed from stock.xchng)

Airplanes produce wakes as they fly just as boats and ships create wakes as they move through the water. Unfortunately, the wakes created by aircraft are not normally visible, thus making them very hard to detect and avoid. The easiest way to visualize an aircraft's wake is the contrails that you can sometimes see as aircraft pass at altitude overhead:

(Image borrowed from Gadling)

However, while the contrail makes the concept of an airplane's wake visible, the wake itself is actually something different. The contrail is generally caused by the hot engine exhaust condensing water vapor in the very cold air aloft. The wake is caused by the movement of the airplane through the air. The act of creating lift involves having air pressure below the wing greater than the air pressure above the wing. This is why airplane wings are, for the most part, not flat, nor are they symmetrical: the top of the wing is curved much more than the bottom of the wing:

(Image borrowed from Air Warrior)

There are exceptions, naturally (aren't there always?): aerobatic stunt planes often do have symmetrical wings, while high speed military jets and balsa wood models have seemingly flat wings. In these cases, the angle of the wing to the airflow is used to make the air behave as if the wing were curved more on the top than the bottom. But I digress, as I so often do . . .

The difference in air pressures above and below the wing is what creates the lift that allows the airplane to fly. The wake is created by the air's natural tendency to even out the differing air pressures. Any area of high pressure is going to flood into an area of lower pressure, be it air or water or any other liquid or gas. When the pressures have become equalized, the flow will tend to relax.

As an airplane moves through the air, the higher pressure air below the wing swirls up into the lower pressure area created above the wing. This action is particularly prevalent at the wing tips where there's no wing to block the flow. This swirling air can best be pictured as a pair of horizontal tornados that extend behind the airplane from the wingtips:

As you can see in this graphic borrowed from an FAA training publication, the vortex coming off the left wing spins one direction, whereas the vortex off the right wing spins in the opposite direction.

On occasions when the humidity is high, the sudden change in air pressure can cause the water in the air to condense, illuminating these vortices:

This normally occurs when the wing is creating a lot of lift at relatively low speed, such as approach to landing. In this photo, which I borrowed from Wikipedia, you can see the vortex created by the extended wing flap. We rarely see these at LAX because the ambient humidity is usually pretty low; my compatriots in more humid climes are doubtless more familiar with the sight. That said, here's a rainy day shot from a few months ago:

In this shot, you can see the vapor trails, as well as a foggy area just above the wing. This is condensation of the water vapor in the air, caused by the pressure drop above the wing. A wing that is not creating lift will not exhibit this localized vapor, as demonstrated by this shot of the same aircraft seen above, taken moments earlier - before it lifted off:

Nifty as they may be, none of these shots show the airplanes' wake; the fog above their wings is a result of the wings creating lift, and helps to illustrate the pressure differential that exists when the wings are creating lift. The vapor trails come closer to showing the wake, but the turbulence that we're discussing is another by-product of the wing creating lift, and tends to be invisible. However, in the following NASA video clips, smoke is used to show the effect of an airplane's wake:

Home again

And we're back! I don't remember who it was that used to say that - maybe Johnny Carson - but in any case, I have returned (I do remember who said that, although I wasn't there at the time). This year's Christmas vacation was spent moving my household stuff from Memphis (where it's been in storage for about two and a half years), with a stop at the family farm in Texas. Over the past two weeks, I've been the captain of the biggest rental truck I could get:

The truck's as big as the house!

While driving across the country, I've had plenty of time to contemplate various options for a narrative about the whole thing, but I think the main points will suffice:

• It rained. A lot. Loading day in Memphis had a 80-percent chance of rain when I left LA three days before and a 90-percent chance the day before. And rain it did: the entire day. When I arrived in Texas, where additional loading took place, it rained some more. For a week.
  
• Hiring loaders was some of the best money I've ever spent. That truck went from empty to completely loaded in two hours. I still marvel at how well that went.
• Driving one of these trucks across the country - or even across town, for that matter - will give you a much greater appreciation for the work done by professional truck drivers. It will also give you much more insight into how stupid many car drivers are around big trucks.
  
• You think the truck rental costs a lot, wait til you have to buy the fuel!

After all the rain in Memphis and Houston, I returned to clear skies in the west. I heard that we had rain out here too while I was gone, and the mountains now have snow caps:

Downtown LA, as seen from the tower on a (rare) clear day.

And you know it's a clear day in LA when we can see the Hollywood sign from the tower!

I hope everyone has a safe and happy holiday season - Go Saints!

Somethings new, something old

For my US readers, hope you had a good and safe Thanksgiving. For those of you who have not spent the last week feasting and shopping, you haven't missed much. Thanks to the on-going painting, plumbing, and deliveries at the house, I haven't got much for you this time, although I am working on assembling an upcoming series on wake turbulence. Updates during the month of December are going to be sparse, as I'll be off for the next couple of weeks and getting the move done (I hope).

This time around, I've got some more new LAX stuff:

AeroMexico and AeroMexico Connect have just moved from Terminal 6 to Terminal 2, making Terminal 2 now almost another international terminal. Hawaiian and Sun Country are the only domestic carriers using Terminal 2; all the rest are international: Air France, Virgin Atlantic, Air China, WestJet, Air Canada, KLM, Air New Zealand, LACSA, TACA, Volaris, and Avianca.

Speaking of Avianca, they've shifted their schedule around: instead of arriving late in the evening and departing that night, Avianca now arrives first thing in the morning and leaves a little before lunch time.

I've mentioned winglets appearing on more models of aircraft before, and here are the latest:

This Continental was the first B757-300 I've seen with winglets. Nearly everyone who operates the -200's has been retrofitting their fleets over the last several years. At LAX, that includes American, Continental, Delta/Northwest, and United. The only other operator of B753's at LAX is Delta/Northwest; I don't know yet if theirs are getting them too.

In addition to the B753's getting winglets, I've also mentioned that a number of carriers have started retrofitting their B767-300's with winglets. American was the first, and I think I've shown you Delta and LAN aircraft as well. Here are the latest additions:

Air New Zealand, who uses B763's to/from Rarotonga in the Cook Islands (the only carrier going directly between LAX and Rarotonga; flight time is around nine hours)

Hawaiian, who unlike most of the other carriers that offer service from LAX to the 50th state, only goes into Honolulu from LAX. American, Delta, and United also serve Kona, Lihue and Maui.

While researching for a previous entry, I ran across a press release announcing the latest Horizon special paint scheme - 'Comfortably Greener' - and the next day, it showed up at LAX.

And finally, something old - this Northwest B744 arrived from Japan last week on its last revenue flight in Northwest livery. After unloading, it left for the paint shop in Victorville. The next time we see it, it'll be wearing Delta colors.

Who's That? Part 16 - Rogue's Gallery revealed

As promised, this was a hodge-podge of special liveries and generics, along with whatever else I found laying around. When I was in New Orleans, they would call this "sweep the kitchen" or maybe even "sweep the swamp". For my simplicity, the carriers with multiple entries are grouped together.

Horizon

Boise State Broncos
(love those colors!)

University of Oregon Ducks
(Although it sure looks like John Deere to me)

University of Washington Huskies

Bonus: Horizon also has a Dash 8 in Huskies colors.

US Airways

State of Arizona

State of Nevada

Arizona Cardinals

Philadelphia Eagles

Star Alliance

This was tricky because it isn't an airline, but rather an airline marketing alliance. I think I've mentioned the Star Alliance before; it was the world's first airline alliance, and I believe it is the largest of the three major airline alliances. There are about two dozen member airlines. An airline's membership in the Star Alliance is usually denoted by the star logo appearing on the aircraft, just aft of the cockpit windows. But there is also this Star Alliance livery which appears on a few aircraft, in this case another US Airways A319. As a controller, I don't care for it because it's very difficult to distinguish what airline the plane actually flies for: The operating airline's name/logo appears in relatively small print below the windows aft of the front door. This makes it difficult for the controllers and other pilots to figure out who the airplane is, especially at night. I've personally had situations where I've told another aircraft to follow or pass behind a United or US Air (among others) aircraft who unbeknown to me was in the Star Alliance livery, only to have the pilot not do what I instructed him to do because I had incorrectly described the airplane he was waiting for. Here are a few more Star Alliance-schemed aircraft:

You can see the Star Alliance logo on this Air Canada E190, between the cockpit window and front cabin door.

All Nippon B773

United B744

United B763

Unlike most other airlines, Singapore's Star Alliance livery retains the airline's logo on the tail, which makes identifying the airline much easier. I wish they were all this way.

SkyTeam

Not to be outdone, the second-largest airline alliance, SkyTeam, has introduced its own special livery in commemoration of its tenth anniversary. Like Star Alliance, SkyTeam's member aircraft display the SkyTeam logo just aft of the cockpit, and the special-liveried aircraft have the parent airline's name/logo aft of the front door, below the window line. The tail I showed you was an Air France B773; here are couple more:

Delta (nee Northwest) B752

China Southern B772

This Northwest Airbus shows the usual placement of the SkyTeam logo on participating airlines' aircraft: Just aft of the cockpit window.

Evergreen

Okay, there really wasn't anything tricky about this one, I just recently started seeing them here again and got some pictures. Evergreen International is a cargo operator based in Oregon. We used to get Evergreen DC9's in the wee hours, but not for some time now.

Air Shuttle

Air Shuttle is the callsign for Mesa Airlines, who appears at LAX as a regional partner for US Airways. They fly mostly to/from Las Vegas and Phoenix using various models of CRJ like this CRJ2. Here's how they normally appear:

Alaska

To commemorate 50 years of Alaska's statehood, Alaska Airlines held a contest for a special paint scheme to appear on a B734: The Spirit of Alaska Statehood was designed by a student from Sitka, Alaska. The design is different on each side of the aircraft, and I like the way the sled dog appears to be wearing shades:

Mexicana

The Vive Mexico campaign was launched earlier this year by Mexican President Calderon to reinvigorate the Mexican tourism industry.

I've been seeing this white-tailed Mexicana A320 for months now; apparently they've run out of logo decals. Interestingly, this airplane and the one with the Vive Mexico livery both carry French registrations - if you look closely, you can see that they're consecutive.

Omega

This was another sneaky one, as it isn't a regular airline. I knew that the armed services have been contracting out non-essential services (anybody remember Halliburton?), but until these guys showed up, I had no idea that the practice had extended to mid-air refueling service. Omega Air offers this specialized capability, which seems like really targeted marketing. As far as I know, the only users of mid-air refueling are the military forces around the world; a mid-flight top up is not available to the flying public at large. This is a B707 - an old and rarely-seen aircraft these days. Compare to the B747 that's tail-on to the camera.

Sun Country

Of all the sneaky shots, this one was the most underhanded: The tail of this B737 wears Aloha colors, but the fuselage carries the Sun Country name. Adding to the underhandedness is the fact that I actually took this shot a couple of years ago. This is how the plane (well, one of its fleet-mates actually) looks now:

Decisions, decisions . . .

Well, the pink bedroom isn't pink anymore. Yippee! What it will be is yet to be decided; what it is currently is beautiful primer, although the ceiling is done. The problem with the paint color brochures that all the Home Depot/Lowes type places have is that the colors look very different when they're actually on the wall. Fortunately, they now sell little sample jars of paint so that you can go home and try them out:


And this is the result. Not quite a rainbow, but enough. It may help to explain the sequence here: I did three batches of three colors apiece, each subsequent batch because I was not sold on the previous one. My father, a retired architect, once told me that a good rule of thumb when choosing colors using the little sample cards is to find a color you like, and then use one that is two shades lighter than the one you chose. I really like the blue on the right in the first shot, but is does appear darker on the wall than it did in the brochure; I fear that in a 10' x 13' room it will be too much if done on the whole wall; thus the blue in the middle of the second shot. Likewise with the two greens.

I have a coworker who is currently also going through the 'painting the new house' routine, and her take on the choice of colors is "Who cares? It's just paint" Which is true of course, but it's just as much work to paint it the second time around . . .

Anyone who fancies him/herself an interior designer sort is welcome to comment with suggestions, although I make no promise to follow any of them. The one constant is that the ceiling is and will remain white. Period. I don't do colors on the ceiling.

Who's That? Part 16 - The Stinkers

You thought we were done? Ha! I've been saving these for last: a sneaky collection of odd balls, one-offs, and assorted other stinkers. Many of them are carriers whose everyday colors I've already shown you, and some of these have been seen here before in other topics. And a few are just downright unfair. Good luck!

Changes

A couple of weeks ago, I mentioned that Midwest (formerly Midwest Express) was operating out of Terminal Four. So naturally, they had to move: They're now at Terminal Six, using the same gate as Frontier. This came about because Republic Airways, the parent company of the carrier we know as Brickyard (that flew as Midwest Connect) has now also bought the bankrupt Frontier Airlines, and is consolidating their operations. We've seen Midwest E190's on the Frontier route to Denver, although Frontier Airbuses are still the norm - we've even had Frontier A320's here recently, which we haven't seen in quite some time. Legally, the Frontier we're seeing now, which is a subsidiary of Republic Airways, is not the same Frontier that we had before.

Out with the old: A Midwest B717 pulling into gate 48A, which the Midwest Connect E190 has just vacated. This is actually out with the old times two, as not only has Midwest moved from Terminal 4, but the mainline Midwest is no more: the B717's have flown their last in these colors, and have been returned to the leasing company (I've heard that they're now in Mexico), and the crews furloughed . Republic has allowed the mainline Midwest operating certificate to expire, but the name will carry on - with the formerly Midwest Connect aircraft and crews covering the routes. Thus the airline formerly known as Midwest no longer exists (I think - the whole thing is a bit confusing, which I suspect is by design).

In with the new: A Midwest (nee Midwest Connect) E190 at gate 67A. This was actually the second recent move at LAX for the Midwest name: it was just earlier this year that Midwest moved from Terminal 3 to Terminal 4. At the same time, AirTran, Frontier and Spirit moved from Terminal 3 to Terminal 6, while Sun Country moved from Terminal 3 to Terminal 6, and then to Terminal 2, and WestJet went straight from Terminal 3 to Terminal 2. Virgin America, who had been at Terminal 6, moved to Terminal 3, thus consolidating all the Virgin brands on the north side of the airport: Virgin Atlantic at Terminal 2; Virgin America and V Australia at Terminal 3, which they share with Alaska and Horizon.
Got all that?

Here's the other recent arrival that I wanted to show you the other day (but couldn't because the shots weren't yet in the MacBook): Besides Japan and Cathay, Malaysia has also started showing up in B777's, although unlike the other two, Malaysia is using -200's.

If you want to read more about Frontier and Midwest, try these Wikipedia entries:
Frontier Airlines
Midwest Airlines

The pink bedroom

See?
Even the ceiling!

Recent arrivals and a follow up

Sorry guys, not much happening on the ole blog this time around -

Thanks to a recent certification (congrats Yoda!), my overtime for this week was cancelled, and that means . . . a 2-day weekend. Whoopee!!! Time to paint the pink bedroom! And the appliances are supposed to be delivered today also; I think I'm doing my part to invigorate the economy: dishwasher, stove, refrigerator, garage-door opener, lawnmower . . . in addition to the afore-mentioned gallons and gallons of paint, with all the accessories.

The follow-up: In response to some of my recent entries, I've received some (unpublished) comments about runway safety at LAX and airborne wake turbulence. While neither request will be addressed in today's entry, I am working on responses and/or giving them consideration for possible future columns.

Horse racing fans know that the Breeder's Cup World Championship was run in LA this year at Santa Anita. This was the first time that the same track has hosted the event in consecutive years, as we had it here last year for the event's 25th anniversary. Horses pass through LAX regularly, although we usually don't get to see them from the tower. I spotted these horse boxes being unloaded from a KLM flight the week before the Cup.

Quite some time ago, I mentioned that Cathay Pacific had started bringing B777's into LAX, but bemoaned the fact that at the time they were only here after dark. Well, no more:

More recently, Japan Air has also started showing up in B777's. Like Cathay, we're still seeing B747's as well - for now anyway.

Today is Veterans Day in the US, as well as Armistice Day and Remembrance Day in other parts of the world. I want to thank all of those who have served and those who are serving now. And for everybody else: Fly your flag today and thank a vet!

Day off

I don't apologize for the dearth of recent entries, but I will mention some of the reasons why:

I had one day off this week, and one the week before that (and the one before that, and . . . ) While the overtime money is nice, the chores and such tend to pile up. As a result, I'm halfway through replacing a static line behind the Baron's panel, and no progress has been made in over a week. Meanwhile I finally put the truck back together, only to discover that it still leaks.

The good news: After nearly two months of mortgage and escrow wrangling, I finally got the keys to the house this past Saturday. The not-so-good news: Since then, I've had no time to even go by and check the mail, much less get started on the painting and other things that I'd like to get done before moving furniture next month. Photos sometime in the future.

This week's day off has been booked for nearly a month: I went to see a radio program last night. No, that's not a misprint. I went up to Pasadena to see a taping of Wait,Wait . . . Don't Tell Me! Afterwards, I got to meet the hosts of the program, who somehow don't look at all like they sound. The show is very topical, and so the taping I attended will probably air this weekend - I'm on the right side, as you face your radio. Spoiler Alert: skateboard pro Tony Hawk is the celebrity guest for the 'Not my job' segment. What probably won't make the show is how he skated onto the stage when they introduced him, and how he gave his board to Peter Sagal as he was leaving at the end of the segment. While the radio program is an hour long, the taping session took nearly twice that long, as there were some edits and re-takes that will get spliced in before air time.

As Pasadena is a bit of a drive from Long Beach even on a good day, I went up early to avoid the traffic. Like five or six hours early. A bit of overkill, to be sure, but I had noticed a movie theater across the street from the Pasadena Civic Center. So I saw Amelia - a film about the life of Amelia Earhart. Nothing too surprising there - the plane still disappears (sorry if I gave it away). While there were some neat shots of an Electra flying over some beautiful landscapes, I doubt if we'll be hearing about this one at the Oscars.

After the movie and before the show, I wandered around a bit and discovered that Pasadena has its own ice rink! Meanwhile, at the ballroom next door to the civic center, there was a big to-do for the retiring police chief. On display was a Plymouth Satellite police car from the late 1960's, looking better now than it ever did when it was in service - or even when it was new. They also had a new Honda police bike with enough lights to fill in for one of LAX's approach light systems if needed. I noticed that the bike's certified speedo went up to 160 mph. Yikes! You would have to be absolutely insane to try and go that fast on our highways, much less the streets.

And that's pretty much it for now. Don't forget to fly your flags for Veterans' Day, coming up Wednesday the 11th.