Archive for wake turbulence

Airline Pilot Confidential: The Teddy Bear Incident.

Posted in air travel, airline delays, airline pilot, airline pilot blog, airlines, airport, airport security, flight crew, flight delays, passenger, unaccompanied minors with tags , , , , , , , , , , , on March 23, 2013 by Chris Manno

flashIt’s the middle day of three back-to-back turns–pace yourself.

In fact, it’s the second leg of the middle turn, Dulles International, 7pm–time to get out of town: the elephant walk of international widebody jets commences shortly.  If we can push back even five minutes early, we can beat the line–and the wake turbulence delay.

prflt docsUse the captain’s invisibility cloak: the ability to do most pre-flight planning on the smart phone. Check the weather, the route, the fuel load. Add more fuel. Sign the release with a touch of the screen, then send a hard copy to a gate printer, all from the cockpit. Wait for it to finish printing then slip into the terminal discretely, invisibly, to pick up the paperwork, avoiding the gate chaos directly. Don’t make eye contact, don’t invite hassles, complaints, requests, anything that delays the door slam and brake release to get ahead of the fat boys headed for the runway. Still have to fly to DFW, drive home–then back out to do the turn again tomorrow. Minutes from pushback, be invisible now.

But wait. Out of the corner of your eye, you see it: a teenage girl, on her phone, tense; next to her, what could only be her younger sister in tears. No parents, no adults, just the agent telling them both, “You either board now, or you’ll have to fly tomorrow.” That sends the little one into big sobs.

timer 3Less than fifteen minutes till push. Can you maybe say you didn’t see any of this? But you did.

“What do you need?” you ask the older, maybe sixteen-year-old sister.

She puts the cell phone down for a second, plaintive. “She left her backpack at security.”

Sigh. The agent is looking at you pointedly, his eyes saying we need to board now and shut the aircraft door. But from the tears in the young girl’s eyes, you pretty much guess what’s in the backpack. I consider taking the youngster back through security–but then think better of it.

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We’d have to run to the center of the terminal, down two escalators, onto the train to the main terminal, up two more escalators, then find the security checkpoint that might still have the backpack–then retrace our steps, before departure time in fifteen minutes. Not going to happen.

I catch the older sister’s eye. “You have some ID?” She nods. “Let’s go.” I head off at a fast walk toward the mid terminal; “Wait here!” she tells her little sister, and the agent slumps the message damn you captain. Big sister’s on my heels, asking, “Can we do this?” Just shrug; “They’re not leaving without me.”

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We tumble down the two-story escalator two steps at a time, shoving past others like obnoxious travelers. I envision people watching, trying to figure out why an airline captain in uniform is running away from a teenager in hot pursuit. I also remember the miles I ran that morning before flight.

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Even though the automated voice is warning that the doors are closing–do not delay this train–I do anyway, holding the door as she jumps aboard. “It’s got all her school books,” she says, out of breath. Right: I have a big picture of a fifth grader hauling a load of schoolbooks on spring break.

“No worries,” I say, “It could happen to anyone.” She nods. “Special guys in there?” I ask casually. She smiles sheepishly.

I don’t care: that’s a very real tragedy for a youngster, losing all the stuffed guys that mean the world to them. Not on my watch.

We spill out of the train on the far end, then WAIT: this will take us to baggage claim and out of the secure area–we need the TSA checkpoint! We dash back through the closing exit doors, then push through the boarding passengers and out the other side.

Two sets of identical escalators–both going down. Means we have to rush up the steps–but which ones? “Which security checkpoint did you use?” I ask. She looks confused; they are identical, not sure how one could really know anyway. “Let’s try this one,” I say, rushing the steps.

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We reach the TSA supervisor’s stand. He shakes his head. “No pink backpack here–try the other side.”

Figures. We run the length of the concourse and arrive at the opposite checkpoint. “You’re lucky,” a cheerful TSA agent in a pressed blue shirt says, “we were getting ready to send it to lost and found.”

Identification checked, signatures. She sees me eying her sister’s backpack. “Uh, we need to start putting a nametag on this, don’t we?”

I nod. Lesson learned. It’s confusing, especially kids traveling alone. “I was on the phone with my Mom,” she says, “hoping we could get someone to drive out here and pick up the backpack.”

“No worries,” I say, in my mind’s eye picturing the waves of 747s and A-340s pushing back, lining up for takeoff.  “Anyone can lose stuff at the airport, especially at security.”

We retrace our steps as fast as we can, me feeling the morning miles, my friend feeling and looking relieved. At the gate, she hands the backpack to little sister who still looks mortified.

They rush down the jetbridge to board. I walk, telling the agent “Just charge me with the delay.” He gives me a glare that says I was going to anyway, which I answer with a smile that says I don’t care.

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The elephants already started the parade and we squeezed into the conga line. Sure, I’d have some explaining to do a thousand miles or so west. But no one missed their connection in DFW, no one was unduly delayed; and most importantly, no one’s little world collapsed with the loss of everyone they loved. That, to me, matters a lot.

Because we don’t just fly jets–we fly people. That, and the occasional special bear.

Jet Wake Turbulence: Distance Ain’t Enough.

Posted in air travel, airline, airline pilot blog, airliner, jet, jet flight, passenger, pilot, travel, weather with tags , , , , , , , , , , , on January 19, 2013 by Chris Manno

Sneaking up behind me, are you? Here’s an infrared view you might need to heed: not the hotspots, but powerful the twin horizontal corkscrews of air current swirling off the wingtips of my jet. They’re wily, dangerous, and not to be trusted.

According to the Flight Safety Foundation, the vortices from a jet can have an internal rotation of up to 300 feet per second and often extend between 2 and 10 nautical miles behind a jet aircraft. The twin tornadoes–that’s literally what they are, horizontal but spinning powerfully–sink at a variable rate, between 300 and 500 feet per minute to an altitude  between 500 and 900 feet below the aircraft’s flight path and can persist for three or more minutes depending on the meteorological conditions.

That’s the problem, but hardly the full situation. Add to this hazard the closely constrained flight path of jet traffic in terminal areas. For instance:

SFO Q bridge

Approaching from the east, you’ll have a traffic stream from the west as well converging on the same runway complex. Not unusual as far as airports go–except that San Francisco International has less than the standard distance separating the two parallel runways. The FAA has waived the normal lateral separation, but you’d better keep that in mind nonetheless because that also means less than normal separation from the vortices of the aircraft next to you. Remember the outward spreading motion of those two tornadoes?

747 BAThis guy could be your dance partner all the way down final–and if he’s next to you, you aren’t entitled to the separation you’d get if he were ahead of you. Mostly, ATC will “advise” you to “use caution” for the heavy on the west runway, workload and time permitting–but they don’t have to.

And time and workload may not permit any advanced warning, and adverse weather can shroud the entire scene anyway:

SEA 16CLook at the inset on the bottom right corner: Seattle (one of my favorite destination cities!) has three parallel runways grouped together, and you won’t be told which of the three runways you’re landing on until you turn base to final about three minutes from touchdown. Would it make sense or even be possible to keep you informed of the heavies on all three inbound tracks? Add to the mix the typically obscured Seattle visibility, plus the added workload of programming and validating the FMS  sytem approach waypoints at the last second demanded by the late runway assignment and is there a possibility of situational awareness overload, on final approach: was that a heavy in front of us? Or on the outboard runway?

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Bring that back to San Francisco, where the standard runway separation is “waived,” like in MSP and many other cities. Now you’ve got a “buddy” laterally whose wake turbulence is drifting outwardly–just as yours is–and just because he’s not a “heavy” doesn’t mean he can’t roll you.

The ICAO worldwide “recommendation” for separation between a “heavy” and a “medium” following aircraft  (say, a 747 and a 737) is 5 NM (9.3 KM); between two heavies, 4 NM (7.4 KM). But the wild card not even mentioned in the separation rules is configuration and maneuvering: simply put, a “dirty” jet (flaps, gear) creates a nastier wake than a “clean” jet, and maneuvering distorts weight. That is, if I level off my 160,000 pound 737 with an addition one-half “G” force, I add to the effective weight another 40 tons of effect. And we’re a medium jet–imagine a heavy maneuvering dirty adding to his effective weight and wake.

That’s the science, now here comes the art. You know the reported winds at the field, but that’s a red herring: your encounter with wake turbulence won’t happen on the field. You need to be aware of the winds on approach, at your altitude. If the lateral wind at your altitude is blowing into the other jet’s wake, here’s what can happen: if the drift equals the outward spread momentum of the wake–and you have to figure the “dirty,” “maneuvering” wild cards mentioned above–the effect will either be to move the wake away more rapidly, or freeze it in place till it dissipates. Which is it?

You can’t see wake turbulence. You can’t be sure where it is, or know it’s strength based solely on the aircraft designation. And sooner or later, you’ll find yourself in it despite your best, most diligent precautions. What are you going to do, captain?

dusk b

For a true jethead like me, the first answer is always speed–but not so fast (pun intended): you’re configured with restrictive maximum flap speeds. If you’re in a final configuration with 40 degrees of flaps, you’re limited to 162 knots max. But the second instinct is valid: power.

throttle bugeye

But power alone is only part of the answer: what you’re not doing is going down. Why not? Because we know the vorticies are sinking. If we remain level or climb, we’ll escape the effects. What are they?

The Flight Safety Foundation survey of hundreds of wake turbulence encounters reveals uncommanded roll in trailing aircraft of up to 45 degrees at altitudes below 1,000 above the ground. One thousand feet is another magic number at my airline: stabilized approach  (on speed, on altitude, power set) is mandatory from 1,000 feet to touchdown. On glidepath–not above or below; not accelerating or decelerating, power set to flown speed and stable. And certainly wings level.

Which brings up the next problem of two major headaches you’ll instantly own. First, the right amount of counter-aileron, even if applied prudently, in many jets will bring up the wing spoilers to drop the low wing rapidly, inducing adverse drag, requiring more power.

Second, the option of climbing or even flying level is constrained by the published missed approach: protected airspace may be below you if you are above the missed approach altitude. And laterally, not only is there often parallel traffic, there’s also dangerous terrain you must always monitor and stay clear of:

MMMX ILS DME 5R

If you encounter wake effects in a level portion of the approach segment, prior to the aircraft ahead descending, at least you know his vortices will descend eventually below you and in this case, you normally feel the “burble” which now cues you: if the winds are keeping his wake aligned with your flight path, on glidepath you’re likely to fly into the tornadoes again when you’re slow and configured with speed-restricting flaps. Now look at the “mileage separation:” still think distance alone is enough? Still committing to the glidepath?

All of that doesn’t even consider the added, inevitable spoiler in every approach: weather. There’s more than terrain and aircraft for you to avoid in a very constrained airspace.

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There’s really only one good answer: up. And “up” may be a s simple as “no more down,” meaning a stopped descent or a slight climb to exit the effects. In any case, if you’re below 1,000 feet you’re no longer “stable” per the mandatory requirements. If you’re above 1,000 feet, you’ve just been cued that the mileage interval, given the meteorological conditions, nonetheless has left you vulnerable to the adverse effects of wake turbulence–and you’re not going to proceed.

Which means, in the immortal words of my old friend the Chief Pilot at my airline addressing my 1991 class of Captain’s “Charm School” (officially, “Captain’s Duties & Responsibilities”) as we sat rapt: you’re going to “get the hell out of town.” Amen.

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Back in the cabin? Expect the usual complaints about the delay for the second approach, plus a regular dose of exaggerated “there I was” tales about their wake turbulence encounter. So, don’t tell them–if you’ve done your avoidance and even escape properly, they’ll never know you even had a problem, which is the ultimate goal anyway: detecting and avoiding the problem in the first place.

The end result is, what they don’t know won’t hurt them, because you won’t let it. And that’s kind of why you get the privilege of flying the jet in the first place, isn’t it?

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