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Speedbrakes not armed before Southwest 737 excursion


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By: DAVID KAMINSKI-MORROW LONDON03:36 18 Jun 2012 Source:

US investigators have determined that the speedbrakes on a Southwest Airlines Boeing 737-700 were not armed before the twinjet slid off the runway at Chicago Midway.

The crew did not deploy the thrust reversers until 16s after touchdown on runway 13C, which was damp as a result of rain showers.

In an update to the inquiry the National Transportation Safety Board says the braking action was reported as "fair" by a preceding Southwest 737 crew.

But it adds that flight recorder information shows the pilots of the incident flight did not arm the speedbrakes during preparations for arrival.

The crew had created extra workload by initially uploading and briefing the wrong approach procedure, and not realising the error until receiving clearance to leave the holding pattern and begin the approach to Midway.

Having reprogrammed the flight-management system for the correct approach, a recalculation indicated sufficient landing distance available. Runway 13C is 6,522ft (1,988m) long.

The crew correctly set the autobrake but the NTSB says the pilots experienced "additional operational distractions" during the final minutes of the approach, including a momentary flap overspeed.

This flap issue occurred at about the time that the before-landing checklist would normally have been performed - a checklist which includes arming of the speedbrakes.

But the NTSB says "no mention" of the checklist or the speedbrakes was found on the cockpit-voice recorder, and the flight-data recorder shows that the speedbrakes were not armed.

After touchdown the speedbrakes did not deploy and the thrust reversers were not activated. The captain "quickly" applied full manual braking after realising that the aircraft was not slowing as expected, says the NTSB, and reverse thrust was engaged with about 1,500ft of runway remaining - an action which automatically deployed the speedbrakes.

"As the airplane neared the end of the pavement, the captain attempted to turn onto the connecting taxiway but was unable," it states. The 737 hit a taxiway light and rolled 200ft into grass.

Without the speedbrakes' interruption of lift, the deceleration capability is "severely degraded", the NTSB says, because the braking effectiveness on the type is reduced by as much as 60%. Delay in the selection of reverse thrust also contributed to the amount of runway used.

Simulations determined that, had the speedbrakes deployed at touchdown, the 737 would have stopped with 900ft of runway to spare - and as much as 1,950ft if the thrust reversers had been activated at the same time.

None of the 139 passengers and crew members was injured in the 26 April 2011 incident.

flaps 9

"Extened" "Deployed" :-)

johnso29

Bummer. I think we've all been there. It's easy to run a checklist without confirming the item has actually been completed. I know I've done it. The best part about this is no one was hurt. Live and learn.

TheFly

Ouch. Sometimes it's just "one of those days."

Marvin

Just curious, but even if one missed the speedbrake checklist item ... why not deploy the thrust reversers with only 5826' LDA on 31C?

I suppose maybe the Captain was distracted by the airplane not slowing down as he expected, but deploying the reversers would have also deployed the boards as long as the system was working properly.

It's always easy to throw stones from the cheap seats, though .....

1Seat 1Engine

Good question. It's not anywhere near normal procedure to not hang out everything for stopping at MDW. There's no meterological conditions that exist that make me relax when landing there. Smack it down and git'er stopped.

Feel similar about SNA but it's also frequently much better wx.

Can't wait to start going into Key West....4800 ft or so?

nerd2009

I agree *doo-doo* happens, however, knowing that MDW is a performance critical airport with short runways, and it was raining,....let's see,... stable approach, touchdown on the touchdown zone markings, speedbrakes deployed, Reversers applied . ....not

Rolf

It's always worrisome when educated and generally clever pilots make a critical misstake. Where does that leave me?

1Seat 1Engine

I don't know too much about this accident but here's what can be determined from the article.

It wasn't a normal day. They were in holding, so something was up. I'm guessing that the runways were changing because it says that they had the wrong procedure in the FMC when they departed holding.

They had a flap overspeed right before they should have been doing the "before landing checklist" which says to me that they had trouble getting the airplane down and slow (probably because they were going to a runway much closer than they originally thought). Another possible reason for the overspeed might be gusty winds...but I really don't know what the weather was. Either or both could contribute to a higher than normal work-load.

Bottom line, it seems like a lot of accumulated feces. Not saying it shouldn't have happened, or that it could never happen to me. But it helps to understand the scenario that helped to set up this incident.

Sink r8

First, you have to run the checklist:

"...But the NTSB says "no mention" of the checklist or the speedbrakes was found on the cockpit-voice recorder, and the flight-data recorder shows that the speedbrakes were not armed..."

When you look at Burbank, or Midway, it validates what many of us think about Southwest's speed culture. It's good to be mission-oriented, to a point. The way I see it, Southwest long ago crossed over that threshold. I don't know if it's a product of getting paid by the trip, or complacency generated by flying one type of airplane for so long, but in my opinion, there is something there.

To be sure, I think the industry in general could use a tune-up in terms of some of our practices, and, to be sure, my airline makes mistakes, and this pilot makes mistakes. They're just not the product of trying be a little too cute.