Monday, May 02, 2011

Stuck in the Mud


Last week, Southwest Airlines topped off a month of unwanted publicity when one of their B737s slid off the end of Runway 13C at Chicago's Midway Airport. Thankfully, nobody was seriously hurt and the aircraft appeared to suffer only minor damage. It's not the first time Southwest has been off the runway in Midway: in 2005, SWA1248 departed the same stretch of pavement (in the opposite direction, on 31C) at high speed, crashing through the airport fence and coming to rest on South Central Avenue, where a six year old boy in a car was killed.

This time around, the happier ending had a few airline pilots making cracks at Southwest's expense. It's true, SWA's accidents have all involved running off the end of runways, and their pilots do have a reputation for taxiing at a, umm, brisk speed. That said, I think there's a bit of schadenfreude over SWA's financial success and the fact that their B737 pilots are now better paid than senior widebody pilots at all the legacy airlines. The old advice about stone-casting in glass houses definitely applies here. The fact remains that Southwest has yet to kill a passenger in 40 years of flying, something none of the legacy airlines can claim. Moreover, to the extent legacy pilots haven't been running airplanes off runways lately (ahem), it's worth pointing out that much of their flying to marginal airports has been outsourced. Delta and American and United jets have all gone on offroad adventures lately, but in each case the airplane was operated by a regional carrier. Every Southwest jet has a Southwest pilot at the controls, something that should shame legacy pilots a whole lot more than Southwest's superior payrates and work rules.

The 2005 accident occurred while landing downwind on a contaminated runway in an intense snowstorm. Touchdown occurred 2000 feet down the runway, and the thrust reversers failed to deploy for 18 seconds. This incident took place in considerably better conditions, although the runway was reported to be wet. The NTSB will do its thing and we'll find out what went wrong, but for now it's worthwhile noting that the airplane went off the end of the runway to the side, and not straight ahead into the EMAS bed that was installed to prevent a recurrence of the 2005 accident. I'm guessing the pilot tried to make a fast left turn onto Taxiway Echo and lost traction.

Regardless of what mistakes were made in this case, Midway is a pretty marginal airport for most jet airliners. Runway 31C is the longest landing runway with 6059' usable, and all the others have under 6000 feet. There are no approaches to 22L/R, and only the ILS 31C is available in under one mile visibility. Circling approaches and landings with strong crosswinds or slight tailwinds are all common. There's really nothing wrong with the airport that an extra 1000' of pavement for each runway wouldn't fix, but that would involve bulldozing a fair amount of South Chicago low-income housing. It isn't going to happen.

In the meantime, Midway is one of those airports that require special attention. I am particularly mindful of what the wind is doing and what runways are available, and will divert rather than land downwind. O'Hare is very close, and there are a number of other usable alternates within a half-hour's flight time. I always land with full flaps regardless of landing weight (we land at normal airports with "Flaps 5;" full flaps make the Junglebus "shake like a dog trying to pass a peach pit!"). At Midway, my idea of the "touchdown zone" shrinks significantly, and I'll usually touch down in the first 1000' or so of runway.* I'll always try to touch down firmly, and few of my MDW landings would be considered "pretty." A firm touchdown ensures that the landing gear proximity sensors close immediately, extending the ground spoilers and enabling immediate braking. All of this is admittedly overkill on a good day, but I use the good days to practice for the really bad ones.

Most pilots that land at Midway or similarly marginal airports with any regularity can understand how it wouldn't take a whole lot going wrong to end up sliding off the end of the runway. Seeing the Southwest 737 stuck in the mud off Runway 13C is a good reminder to stay vigilant and continue doing everything I can to prevent it happening to me. Incidentally, I worry a lot more about the "Engine Failure at V1" scenario in MDW than a long landing, and there's not much I can do to decrease my risk in that department. The good news is that the chances of anyone suffering a complete engine failure in the few seconds between 100 knots and Vr while departing Midway are rather small, which makes my own personal risk quite tiny indeed.

* Touching down at 1000' requires going below the VASI in the final stages of the approach. Some airline pilots balk at this based on a flawed understanding of 91.129(e)(3), which requires pilots to "maintain an altitude at or above the glide path until a lower altitude is necessary for a safe landing." If you follow the VASI all the way down, you will touch down 1500-2500 feet down the runway, which is unacceptable at Midway with anything other than dry, bare pavement. Most airplane's contaminated runway numbers are contingent on touchdown at the 1000' mark. I certainly don't suggest dusting off the chimneys of the houses surrounding Midway, but with the displaced thresholds and lack of high obstacles on approach, going below VASI in the last quarter-mile at MDW is both safe and legal. You will see most aircraft cross the displaced threshold at well under 50'.

10 comments:

typingtalker said...

From the NTSB preliminary report.

Witness marks on the runway indicated the airplane touched down about 450 feet from the displaced arrival threshold. Runway conditions were reported as "wet and fair [braking]" by a preceeding arrival.
http://www.ntsb.gov/aviationquery/brief.aspx?ev_id=20110426X53639&key=1

David Troyer said...

As a passenger, I definitely notice the difference in landings at KMDW... As you mentioned, they are generally harder and there is no time wasted in engaging full reverse thrust.

Dave said...

Is landing on 13C extremely rare? Of the many flights I've flown on as a passenger into Midway over the last 6 or so years (lots of WN, even NewCo once!), all have been on 4R/22L or 31C...

Rob said...

Southwest is the one beacon of hope and an airline that all pilots should aspire to make theirs like. What is most surprising is that the airline is an America, the place where arguably the race to the bottom began, and the place that Australian airline managers are so keen to copy.

If only they looked at the profits looking after your staff generates...

i3simes said...

Hi Sam,

I believe the ground spoilers auto-deployed at touchdown, but the TR's were stowed for the first 18 seconds of the ground roll.

How many flap settings does the E-jet have anyway?! At least it has slats. haha

Brandon

Aviatrix said...

I sound like a spammer, but all I have to say is "Superb post as always, Sam." It's always worth waiting for your excellent mix of research, industry knowledge and supported opinion.

Randolph Aviator said...

Taxiing fast means going through your checklist fast, which resulted in a Northwest accident in Detroit.

Time to take a little time, boys!

Harrison said...

I agree with you about the VASI. A visual duck under is legal and appropriate.

Rick B said...

Sam you wrote "The fact remains that Southwest has yet to kill a passenger in 40 years of flying, something none of the legacy airlines can claim."

Depends on how you classify Hawaiian Airlines, certainly not as large as other large airlines (in sheer size and number of employees and hulls) but qualify's as a Major Carrier, fifth oldest in the United states (now that's a Legacy huh?) & 11th largest (CAA ops certificate #5) and no fatal accidents in its entire history see http://en.wikipedia.org/wiki/Hawaiian_Airlines for specifics.

Just the facts.

Sam said...

Brandon-- Thanks, I brain-farted and typed spoilers when I meant TRs. Fixed. The JungleBus has 6 slat/flap settings. Flaps 5, the normal landing setting, is Slats 25 degrees and Flaps 20 degrees. Flaps Full is Slats 25 and Flaps 35.

Dave-- I wouldn't say 13C is "rare", but 31C and 22L are certainly more common due to the prevailing west winds in the Chicago area.

Typingtalker-- That's very interesting, they didn't waste any time at all getting it down so it should have been able to stop in the runway remaining. Will be interesting to see what happened.

RickB-- Is this Horizon Rick? How you doing, man? You're right, I overlooked Hawaiian and their exemplary safety record. They certainly qualify as a major and as an airline with a long, rich history. I guess my unofficial definition of "legacy carrier" would be major airlines with nationwide/worldwide networks who reached maturity before deregulation. As of ten years ago, I'd put United, Delta, NWA, Continental, USAirways, American, and TWA in that category.