Southwest B737 Overrun @ Chcago MDW

[punkalouver]

"For the RECORD (please respond if incorrect)
CHICAGO MIDWAY runway 31Center usable length landing beyond GLIDESLOPE is:
4927feet."


Could you please tell me where you got this information from?

[jondc9]

Originally Posted by punkalouver

"For the RECORD (please respond if incorrect)
CHICAGO MIDWAY runway 31Center usable length landing beyond GLIDESLOPE is:
4927feet."


Could you please tell me where you got this information from?

Do you know what a Jeppesen 10-9 page is? for those who don't, it is a very nice diagram of the airport in question along with (on the back) useable runway lengths including beyond gs.

So that's where I got the info. Anyone who has different info, please post. The runways haven't changed at MDW in a heck of a long time, but as my charts are slightly out of date (this century though!) someone might have newer info.

regards

jon

[punkalouver]

"Do you know what a Jeppesen 10-9 page is? for those who don't, it is a very nice diagram of the airport in question along with (on the back) useable runway lengths including beyond gs.
So that's where I got the info. Anyone who has different info, please post. The runways haven't changed at MDW in a heck of a long time, but as my charts are slightly out of date (this century though!) someone might have newer info."


Thanks. I don't have access to Jepp's for a few more days. This would seem to imply that the Threshhold crossing height of 51 feet for runway 31C is for the displaced threshhold. Possibly misleading to some pilot's using government charts if landing distance beyond the glidepath isn't mentioned somewhere else.

[barit1]

Count me, and my entire lunchbunch, in that 99.99%. I would REALLY like to known who/when/where the r/t credit originated. Was it -

Boeing?
A (potential) customer airline?
A Boeing competitor?
An external (foreign) jurisdiction?

Someone is responsible, right?

[westhawk]

Hi Punkalouver.

I was trying verify that figure as well. I have been off the last several days, so have not been around the Jepps to check this out. The only place I am accustomed to seeing distance remaining beyond glideslope is on the Jeppesen 10-9 pages along with the runway specifics. Now I see that Jondc9 has verified that as the source of his stated figure. (Easy, big Jon, I think Punkalouver just wanted to know the source of that info! Thanks for the verification.)

I do think that if they touched down some 400' beyond the rwy/ G/S intercept point, it is indicative of a minimal flare, sufficient only to reduce the impact with the runway to a moderate 5.0 on the Richter scale! Flying it into the ground with no flair might (at the ROD required to stay on glideslope at their groundspeed) likely have exceeded the certified structural limts of the airplane. (part 25 calls for 10 fps (600 fpm) at max ldg wt) And going below the G/S in minimum visibility conditions doesn't have much of a future in it either. So it seems entirely possible under the above assumptions that:

1) The approach was begun with the belief that it could be completed according to regulation and policy. I would also, giving this crew the benefit of any doubt, tend to think that they believed it could be safely accomplished. (albeit with no margin for error or failure)

2) The approach was flown accurately enough to put it down about where the most ideal profile that could be planned under the prevailing visibility conditions and allowing for a minimal sink rate reduction prior to touchdown would put it. Just for reference, 400' goes by in about two seconds at touchdown speed. Not much float there!

3) Had the reversers deployed when first commanded, a successful stop on the runway would likely have been completed. It is important to learn why they did not.

I'm not trying to say that any of this is proven fact. Indeed it it not yet that. Need more data (such as a CVR transcript and FDR traces) for that. But I do want to challenge this idea that this was a long landing or that they floated way down the runway just because there was 2000' of runway surface behind them at touchdown. Based upon what is apparent so far, this idea should at least be viewed with suspicion if it is not discarded alltogether.

Finally, This idea of allowing landings to be planned down to a gnat's behind, with no built-in safety margin, taking credit for the effect of reversers, to an icy runway in minimal IMC conditions, is at the least, deserving of a thorough audit. It must be determined if this procedure provides the desired level of safety margin appropriate for public transport aircraft service. Even if there is no intent to do so on the part of SWA or the FAA, allowing the procedure used to determine the required runway for this landing could have placed a subtle kind of pressure to "make it happen" on that crew. Most pilots are honest working folks who want to get it done if they can. Rules and company safety culture set the limits. Consideration must be given to the possibility that eliminating the "reverse credit" in the future may reduce the chances for a repeat occurance. In it's letter to crews regarding this issue, the SWAPA safety committee gave some very carefully worded, yet useful suggestions on dealing with the issue. Especially if you read between the lines a little. PICs are being called upon to earn their Captain's pay by using their command judgement to make the tough calls. The letter suggests some ways to justify it.

Best regards,

Westhawk

[fepate]

Originally Posted by westhawk

But I do want to challenge this idea that this was a long landing or that they floated way down the runway just because there was 2000' of runway surface behind them at touchdown.

I must second this assertion. In the conditions that night, near minimums for the approach with a tailwind, the touchdown point seems entirely reasonable.

[jondc9]

Originally Posted by potuspilot

barit1,

The SWAPA safety alert says reverse thrust credit is also used in RTO calculations.

This accident was a tragedy for the family of Joshua Woods (the 6 year old boy).

What concerns me even more is the aborted takeoff scenario at MDW (rto). Especially with the idea of TR's included in calculations. I grew up thinking that reverse was icing on the cake. Counting on reverse is something we shouldn't do!


But imagine taking off at max weight for runway 31center. AT V1 plus one knot BANG, massive engine vibrations, uncontained failure. The courage to FLY the plane shaking like hell will be the penultimate test of any pilot's mettle. To reject the takeoff at v1 or beyond will most certainly make the accident we have been discussing look like a picnic.

Legal and SAFE are spelled differently.

By the way, an engine failure departure procedure at MDW is no cinch, neither is the standard departure. Rapid turn within restricted airspace.

Be on your toes those who fly at MDW.

jon

[Buster the Bear]

So Joshua Woods, driving in his parents car, was killed by a rogue Boeing 737 landing at an airport. The on board Boeing computer calculated that an approach and landing could be easily conducted when the crew input the available data that they had access to.

As a mere by-stander, this is shocking! To potential Boeing passengers this must be awful, to read that on board computers, after years of use, are NOT fail safe?



Executive summary: the thrust reversers did not deploy properly, causing the plane to overshoot the end of the runway.

A point of contention right after the accident was that the pilots had apparently activated the automatic brake system in violation of Southwest policy, but the NTSB concluded the crucial factor was the unanticipated
18-second delay in the thrust-reversers deploying. As a result, NTSB is urging the FAA to to prohibit allowing for thrust-reversers in onboard stopping-distance calculations. (Before landing, the crew had used the onboard computer to calculate stopping distance for "wet-poor" conditions; those calculations assumed the thrust reversers would deploy normally.)

The risks here appear to be two of the most common ones: trusting an automatic system to activate within specification 100% of the time, and allowing that trusted system to be the critical margin between success and catastrophic failure -- even in the successful-landing scenario represented by the onboard computer's figures, the plane was anticipated to stop within
30 feet of the end of the runway after a rollout of over 4000 feet, a margin of error of less than 1%.

FACT or FICTION?

[barit1]

R/T on FAA.GOV

I went to www.faa.gov and did a Google of that site for "reverse thrust"- and found 259 hits.

But virtually all of them were related to Part 150 - Community Noise, placing restrictions on R/T to provide noise relief.

Is the airports side of the FAA talking to the aircraft side???

[flown-it]

This just in. 'bout time too!

National Transportation Safety Board
Washington, D.C. 20594
Safety Recommendation
Date: January 27, 2006
In reply refer to: A-06-16
Honorable Marion Blakey Administrator
Federal Aviation Administration
Washington, D.C. 20591

On December 8, 2005, about 1914 central standard time,
Southwest Airlines flight 1248, a Boeing 737-7H4,
N471WN, landed on runway 31C at Chicago Midway Airport
(MDW), Chicago, Illinois. The runway was contaminated
with snow. The airplane departed the end of the runway
and rolled through a blast fence and a perimeter fence
and then into traffic on an off-airport street. The
airplane came to a stop after impacting two cars,
which resulted in the death of a child passenger in
one of the vehicles. Of the 2 flight crewmembers, 3
flight attendants, and 98 passengers aboard the
airplane, 5 reported minor injuries, and the airplane
was substantially damaged. The flight was operating
under the provisions of 14 Code of Federal Regulations
Part 121 as a commercial passenger flight from
Baltimore/Washington International Thurgood Marshall
Airport, Baltimore, Maryland. Instrument
meteorological conditions prevailed for the flight.
The National Transportation Safety Board believes that
the urgent recommendation contained in this letter
requires immediate attention to restore landing safety
margins on contaminated runways.

Snow began to fall in the area surrounding MDW about 5
hours before the accident. While the flight was en
route and holding to land at MDW, the flight crew
obtained updated weather information and runway
braking action reports from air traffic control. On
the basis of this information, the flight crew planned
for fair braking action on landing on runway 31C. The
runway was last cleared and treated about 45 minutes
before the accident. About 30 minutes before the
accident, airport ground personnel performed a runway
friction measurement, which indicated that the runway
friction was “good.” About 1/8 to 1/4 inch of
scattered snow was on the runway when the airplane
touched down.

Expected Landing Performance on Contaminated Runways

The flight crew used an on-board laptop performance
computer (OPC) provided in the cockpit of Southwest
Airlines’ airplanes to calculate expected landing
performance. For landing performance calculations,
flight crews enter flight specific data into the OPC,
including the expected landing runway, wind speed and
direction, airplane gross weight at touchdown, and the
reported runway braking action. The 737-700 OPC is
programmed to assume that the engine thrust reversers
will be deployed on touchdown1 and to calculate the
stopping margin (the runway distance remaining from
the front of the nose wheel to the end of the runway
pavement after the airplane comes to a stop). The OPC
then alerts flight crews if the remaining runway
distance is not sufficient for the airplane to land
and completely stop on the runway under the selected
weather and runway conditions.

The flight crew entered weather data into the OPC and
input WET-FAIR as the runway braking condition. The
OPC calculated that the airplane would be able to land
and completely stop on runway 31C under the selected
weather and runway conditions with about 560 feet of
runway remaining.2 During post accident interviews,
the flight crewmembers told Safety Board investigators
that they considered 560 feet to be an acceptable
safety margin and, therefore, decided to execute the
landing.

The assumption that engine thrust reversers would be
deployed on touchdown is consistent with Southwest
Airlines’ Flight Operations Manual, which states that,
when landing under less than good braking conditions,
the thrust reversers are to be used as soon as
possible during the landing roll and are to be applied
with the brakes. However, flight data recorder data
revealed that about 18 seconds passed from the time
the airplane touched down to the time the thrust
reversers were deployed; at that point, only about
1,000 feet of usable runway remained. During post
accident interviews, the captain stated that he
attempted to immediately deploy the thrust reversers
but that he was unable to do so. According to the
first officer, at some point during the rollout, he
noticed that the thrust reversers were not deployed,
and he then reached over and deployed them. The late
deployment of the thrust reversers almost completely
negated the stopping distance benefit that had been
expected because of the use of the thrust reversers.
The airplane departed the end of runway 31C at a
ground speed of about 50 knots.

Reverse Thrust Usage Credit

The Federal Aviation Administration (FAA) does not
allow the use of the reverse thrust credit when
determining dispatch landing distances. Further, the
decrease in stopping distance resulting from thrust
reverser use (which increases the safety margin) had
typically been used to offset other variables that
could significantly degrade stopping performance.

However, the FAA allows the reverse thrust credit to
be used in calculating en route operational landing
distances for some transport-category airplanes, such
as the accident airplane, a 737-700. Accordingly, when
using the reverse thrust credit for contaminated
runways, the required runway length for 737-700 model
airplanes is about 1,000 feet less than the required
runway length without the reverse thrust credit. The
OPCs of Southwest Airlines’ 737-300 and -500 model
airplanes do not use the reverse thrust credit;
therefore, these model airplanes have a greater
landing safety margin. In this accident, when the
thrust reversers were not (or could not be) used in a
timely manner, the airplane could not be stopped on
the runway because of the absence of this extra safety
margin.

1 Boeing 737-300 and -500 model airplanes are not
programmed with this assumption.
2 The flight crew also input WET-POOR as the runway
braking condition. The OPC calculated that a 30-foot
runway margin would remain.


If the reverse thrust credit had not been factored
into the stopping distance calculations made by the
OPC, it would have indicated that a safe landing on
runway 31C was not possible under a braking condition
of either fair or poor. The Safety Board is concerned
that the landing distance safety margin is
significantly reduced on a contaminated runway when
the reverse thrust credit is allowed in landing
stopping distance calculations. As a result, a single
event, the delayed deployment of the thrust reversers,
can lead to an unsafe condition, as it did in this
accident. The Safety Board concludes that the safety
margin must be restored to those airplanes for which
the reverse thrust credit is currently allowed in
landing performance calculations.

Therefore, the National Transportation Safety Board
recommends that the Federal Aviation Administration:
Immediately prohibit all 14 Code of Federal
Regulations Part 121 operators from using the reverse
thrust credit in landing performance calculations.

(A-06-16) Urgent

Acting Chairman ROSENKER and Members ENGLEMAN CONNERS,
HERSMAN,
and HIGGINS concurred with this recommendation.
By: Mark V. Rosenker
Acting Chairman
as70co/Midway/Midway Urgent Rec.doc
KSears drafted 1/9/06; revised 1/12/06;revised 1/20;
final 1/26/06

[canyonblue737]

Originally Posted by jondc9

One question, does the handy dandy laptop computer with reversers figured it make its calculation from the THRESHOLD of the runway or from GS touchdown? I would bet "threshold" is the answer.

Bzzz. Wrong answer. Calculations are made from GS touchdown aim point with further penalties for anticipated float due to flare dependent on if flying a flare visually or with HUD flare cue and set in the software by the pilot.

Also the 5300 stopping figure from the NTSB was based on not using TRs for 18 seconds as in accident case. Obviously TRs were predicted by the software and the pilots in their decision making to be deployed immediately so the predicted stopping figure would be well under 5300 ft, and under the 4900 or so feet available beyond the GS touchdown. Why the TRs were not able to be deployed is still being investigated obviously.

[canyonblue737]

Originally Posted by jondc9

I have a call into NTSB asking if spoilers deployed automatically. STILL no answer.

They absolutely did. Spoilers and Autobrakes both worked normally and immediately upon touchdown.

[canyonblue737]

Originally Posted by barit1

Count me, and my entire lunchbunch, in that 99.99%. I would REALLY like to known who/when/where the r/t credit originated. Was it -
Boeing?
A (potential) customer airline?
A Boeing competitor?
An external (foreign) jurisdiction?
Someone is responsible, right?

The data is Boeing's, why they ran numbers that way is anyone's (good) guess.

[Ignition Override]

Pardon the editing/duplication errors. It is hard enough choosing the correct keys for the "control page" which should enable the Sturmovik combat game "Forgotten Battles" to extinguish a Bf-110 or P-38 "simulated" engine fire.

[Ignition Override]

Barit1: Check #333. Even if airports were to communicate openly with airline Flt. Ops Departments and Union Safety Officers, mistakes regarding runway treatment and/or braking action evaluations might still happen. Problems in controller 'shift change' created communication problems at DFW (microburst), Charlotte (different Approach frequencies during weather) and other places. Not to mention the problems verifying, between Tower Controllers and Ground Staff, what was done to the runways during winter weather with snow and ice on all surfaces.

It still interests me to find out whether the Southwest crew requested an ILS in the opposite direction, so that a headwind could have been possible.
Some advice to us has been to find out when the latest braking action report was made (was it a jet? or did the plane have props which can mostly use ground fine/reverse blade angles to slow down?), was the runway treated with chemicals, are the turnoff areas treated at all , how much snow has fallen since the latest jet report?

A tailwind was never adviseable-even with just water on the runway. Next door to Midway, (ORD) O' Hare's runway 09R can feel like fair braking at best, with only light rain, and I made a PIREP to the Tower controller after we took the high speed (at a fairly low speed) exit. Even the big airports can have lots of rubber deposits- on the MIDDLE of the runways!

In the countries where most of you guys (and gals) live, airports operate by the book, therefore, these lessons are only for US pilots. Forget any "misson-oriented", "get-home-itis", desire to show the other (whether a guy or, especially a younger [female!]) pilot that you can handle anything. Don't land or takeoff if something does not seem quite right. Last leg of the trip-too da^^n$d bad. Who are they going to blame?

[westhawk]

It still interests me to find out whether the Southwest crew requested an ILS in the opposite direction, so that a headwind could have been possible.

Ignition Override:

If my memory serves me correctly, the reported visibility was less than the visibility minimums for the 13C approach, which were higher than the 31C approach. Subject to verification.

Best regards,

Westhawk

[barit1]

Originally Posted by canyonblue737

The data is Boeing's, why they ran numbers that way is anyone's (good) guess.

I'm sure the DATA comes from Boeing, and R/T accounting is fine for economics/statistical purposes - brake wear models, etc etc. It makes sense for the beancounter flying a desk.

My question is: Why did the FAA permit R/T accounting for flight planning? What made them change their minds? Who started down the slippery slope?

[d246]

Give it a rest boys, all this esoteric nonsense is all very well but, as those of us who operate commercial jets will tell you, putting one down on a runway of that length in those conditions is pushing one's luck to put it mildly.

[jondc9]

To CANYON BLUE:

You indicated that the auto spoilers deployed on landing and the auto brakes worked too.

How do you know?

The pilot reported no deceleration and started manual braking.

Were the throttles slightly forward of idle prohibiting deployment of thrust reversers?


Also, to all, the idea of using 13 Center has been brought up. some reported that the minimums were too high on that runway and the wx was not cooperating. I would just like to point out that one can hold for the wx to improve. One would have to wait awhile to get ORD to cooperate and the wx too. But still, it could have been done.

In fact, I have made the request going into midway. Initially I was told that I would have to hold for over half an hour. (this being an atc ploy I believe) As soon as I said I would hold for an hour if need be, amazingly I was vectored for the approach I wanted right away.


ALL pilots must remember that they (pilots) are the boss and the controllers are here to help the pilots, not the other way 'round.

jon

[Tanker]

Originally Posted by barit1

I'm sure the DATA comes from Boeing, and R/T accounting is fine for economics/statistical purposes - brake wear models, etc etc. It makes sense for the beancounter flying a desk.
My question is: Why did the FAA permit R/T accounting for flight planning? What made them change their minds? Who started down the slippery slope?

For the same reason that a 2 engine jet is now capable of ETOPS certification, reliability. What seems like just a few year ago a 2 engine jet would never be certified for ETOPS. Now due to engine reliability they are. The same with the thrust reversers. Does better reliability means that safety is better. The aircraft manufacturers convinced the FAA that is the case.