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SWA 737 overrun at BUR - Dec 6 2018

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SWA 737 overrun at BUR - Dec 6 2018

Old 16th Dec 2018, 04:34
  #161 (permalink)  
 
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Discussion: The root cause of the wet runway stopping performance shortfall is not fully understood at this time; however issues that appear to be contributors are runway conditions such as texture (polished or rubber contaminated surfaces), drainage, puddling in wheel tracks and active precipitation. Analysis of this data indicates that 30 to 40 percent of additional stopping distance may be required in certain cases where the runway is very wet, but not flooded.
If you are down to your last 48m to be "legal", then should you be doing this? I've diverted in similar circumstances from almost exactly the same runway length in due to heavy rain.
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Old 16th Dec 2018, 09:15
  #162 (permalink)  
 
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#159, without details of performance ‘tools’:- what is the basis of calculation, origin, who published them and the guidance for use, suggests weak knowledge ‘in the workshop’.
Blunt or rusty ‘tools’ are of little value; a key point about landing distances is that they are approximate (never really sharp), and that accuracy decreases with increasing ‘wetness’ and contamination.

Technical variation can be estimated, but the human contribution less so, especially in new or novel conditions. The conditions in each landing differ, we never experience the same landing twice; past comparison is of lesser value, but the lessons learnt should be, providing they are applied to the next landing.
Tools are best used by skilled craftsmen, according to circumstance, judgement - ‘the right way to cut the grain’.

BA ‘good’, is good relative to a wet runway. Wet performance is a projection, an estimate based on dry runways, which have a different version of ‘good’.
Consider how performance tables might accommodate the range of water depths up to 2.99 mm, but differ where 3 mm is defined as flooded (% of runway covered). The tables do not cover every combination, particularly when we consider runway surface texture, tyre wear; that’s why we have regulatory advice and the need for professional knowledge, and above all else the ability to apply professional judgement.

CT, I support your underlying view, but please there is no ‘legal’ value in performance, nor perhaps in anything we do in aviation.

There are required or recommended values, and most important, justifiable choices of action - these are the basis of your defence.
There is nothing legal about sitting in EMAS quoting book figures when the lawyers are speeding down the runway behind you, measuring the actual landing conditions (‘legal’ hindsight), and forming their judgement on how you handled the situation and aircraft.
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Old 16th Dec 2018, 09:29
  #163 (permalink)  
 
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Reluctant Bus Driver

Thank you for your info. I just googled the available landing distance since I don’t fly there. With the numbers you came up with, a legal landing is not possible with our -700s. I don’t know the technical details of SWA aircraft, and the landing weight was a guess.
My numbers are raw numbers and do not include the legal margins. Add those on your runway lenght and this landing is a no go.
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Old 16th Dec 2018, 10:58
  #164 (permalink)  
 
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ManaAdaSystem

I'm curious, does this actual landing distance include distance to the touchdown point?

Which margin do you normally have to add in your operation?
(Just being curious here so the numbers have some more meaning for me)
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Old 16th Dec 2018, 11:25
  #165 (permalink)  
 
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Yes, they include air distance to full stop.
As for the additional margins, some performance buff will probably come along with the explanation, but if i remember correctly, wet runway add 15% to the required dry landing distance. If you operate in Germany, you follow the same rules as me.
I just can’t be bothered to dig into the books at the moment.
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Old 16th Dec 2018, 15:33
  #166 (permalink)  
 
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Regardless of the theories posted here, I hope for the sake of the SWA crew, that their landing data was calculated correctly and that they touched down in the touchdown zone. If they did not do the data or ignored it they will be in a lot of trouble. It's a similar scenario to the AA 737 that went off the runway in kingston where there was no EMAS and the aircraft was destroyed. The crew is back on the line and had no enforcement action against hem because the NTSB and subsequently the FAA stated they acted in accordance with all procedures and did not know of the standing water on the runway. I hope this will be the case here as well..
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Old 16th Dec 2018, 16:18
  #167 (permalink)  
 
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Agree re performance data. Is the 737 landing performance now based on OLD / FOLD calculations opposed to the old style ‘actual’ data. The wording in some posts suggest the latter, if so then either Boeing - tardy publication revision, or Operator - not using the best available data, might get a hard time from the FAA.

Re standing water; there are subtle differences between not knowing due to inaccurate surface descriptions, or if reported not ‘knowing’ because the previous information was not checked, based on what could be deduced - WXR etc, also not knowing or not seeking the best data at all. The dividing line of professionalism.

Where crews have followed procedures, this should not be taken to imply that the procedures are sufficiently accurate or have considered a wide range of situations.

CS 25.1591(~page 199) and particularly CS AMC 25.1591 (~page 878) give salutary enlightenment of the limitations in calculated performance.
Of note, these sections do not appear in the corresponding FAA documentation - non harmonised rule making.
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Old 16th Dec 2018, 19:59
  #168 (permalink)  

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@ hans, 172 (and C/A)
Both 737 and 320 have quite a similar landing geometry. If the antenna passes THR on the G/S at 50', later the MLG will cross at 33' (34) which should be the RA indication (calibrated that way).


The radio call "over the numbers" should be 30 (not 50 btw) - the normal landing technique for the expected touchdown point at 455 m (1490 ft). Irrespective of LDA. Runways >= 2400m are a small cognitive challenge due to the placement of the large distance marker and PAPI (nicely documented by the incumbent's almost contradicting statements above).

The no-flare point is 200m (-ish) plus another 255 m (835 ft) is calculated for the flare. That's a fair deal. On a good day, a 400 m touchdown is perfectly possible while keeping the normal profile. 350 surely too with a thump Re-iterated: To fit the actual trajectory inside the calculation model, no extra skill or fjord-pilot tricks are required.

video: https://www.youtube.com/watch?v=j2WHVjP60Gg&feature=youtu.be&t=330
54' TCH/RDH, aim-point 314 m deep (nominal 3)
35' RA when wheels over the THR
4 reds on the PAPI (displaced 470 m) at the round out and touchdown exactly abeam https://www.google.com/maps/@48.9931.../data=!3m1!1e3

However, the plot thickens in the second act where the relationship between the actual achieved vs. calculated deceleration needs to be discussed.

ManaAdaSystem:I'll pass on the measuring exercise, yet for my improvement: Which of these I actually said do you disagree with?
  1. Shorter runways require correct flying, whereas the long runways don't, absolutely.
  2. anything beyond 600 m is not correctly done. Irrespective of runway length.
  3. The best a pilot can do to be safe and effective on short runways is to practice on the longer ones to get that skill perfected.
  4. The touchdown is usually decided between 150 and 50 feet above the ground
  5. 350 (m touchdown) ...with a thump ...is surely ...perfectly possible ... while keeping the normal profile
  6. To fit the actual trajectory inside the calculation model, no extra skill or fjord-pilot tricks are required.
  7. Aiming closer to the threshold, steepening the angle in the last stages is more consistent with the intention (of saving distance)
  8. I am sure everyone does a bit more pushing on the short runways and tries to tweak it closer to the tarmac edge.
  9. A cautious duck under… is part of the duty even, to make sure all the odds are in our favour. The (another) extra 90 meters is not a negligible distance.
  10. The touch-down point and speed are what matters.
  11. retard the thrust to idle by 15'
  12. Vref to Vref -5
  13. "no landings beyond TDZ markings" is a sound principle
  14. the last two (extra and incorrect) distance markers on the pavement (at BUR RWY 8) are nothing but a deathtrap.
  15. (after the touchdown) the plot thickens ... where the relationship between the actual achieved vs. calculated deceleration needs to be discussed
  16. (due to low friction) The last 60 m (at the far end) you might critically need, and as if they did not exist (when wet or worse)
The numbers are not priorities, just labels so you can respond easily.

Last edited by FlightDetent; 16th Dec 2018 at 21:36.
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Old 16th Dec 2018, 20:04
  #169 (permalink)  
 
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One thing comes to my mind regarding this conversation.
Why is the First Officer not the Captain? If decisions around takeoff and landing performance ( along with hundreds of others) were simply a matter of checking the data and seeing whether it said yes or no, then plenty of 19 year old bright young things would be employed to operate the airliners flying around the globe.
The reality is that the regulator and the company have determined that the aviation environment has too many variables for this to work. For safe operation there needs to be an experienced person in the flight deck with the authority to say yes or no regardless of what the computer says. To abdicate decision making to the onboard performance tool is to disregard that reality and the paying passengers and their relatives would rightly feel uncomfortable if they were aware of this happening.
As technology becomes faster, more accurate and more reliable, are we less inclined ( as Captains) to exercise our command authority based on experience? I think so. There are examples of it on this thread.
If we are less inclined now than thirty years ago, where does that leave us twenty years from now? There will be Captains who have witnessed extremely reliable technology their entire lives, there is every chance of increasing reluctance to over ride or even question it’s solutions.
I think we need to be aware of this tendency within ourselves and actively question the common sense element of our decision making and consider what the passengers, company, and regulators expect of us.
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Old 16th Dec 2018, 20:33
  #170 (permalink)  
 
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One of the most pertinent contributions to Prune I have read in quite some time. It does touch on some pretty profound philosophical considerations.
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Old 17th Dec 2018, 04:59
  #171 (permalink)  
 
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Have not every post on this long thread.
My thoughts (and actions in the cockpit) is that a short runway,
tailwind, or wet runway require vigilance. Having two of these together requires an extra amount of vigilance and thoughts of holding or diverting,
All three, is realistically something you don't want to subject yourself, crew and pax to. A 5800 foot runway with numbers that give just a margin of just a couple of hundred meters is unacceptable.
Heavy rain may mean that the braking action and reported winds are incorrect.
Don't know all the facts in this case, but everything reported does not seem to point to landing in these conditions.
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Old 17th Dec 2018, 11:44
  #172 (permalink)  
 
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ManaAdaSystem

BUR RW 8 is 5802’ long not 6500’. Using medium or a 3 for braking action that +R would require I can’t make the numbers work for a 700 with a 10 knot tailwind.
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Old 17th Dec 2018, 15:57
  #173 (permalink)  
 
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Originally Posted by Reluctant Bus Driver View Post
As some have alluded to, the usable landing distance, assuming they did not go below GS, is 4575ft. Not much to hang your hat on..
I realized afterwords that this statement is incorrect. You use the runway distance on the 10-9 pages minus any displaced thresh hold. In this case it is indeed 5802 ft., so they may very well have been legal with a very light -700. Apologies.
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Old 17th Dec 2018, 19:15
  #174 (permalink)  
 
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Sailvi767

Is 3 automatically required for heavy rain? Does that override the airport’s current field condition report?
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Old 19th Dec 2018, 02:16
  #175 (permalink)  
 
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Not at SWA anyway. Heavy rain is a weather condition, not a runway condition. You could always argue to use a more conservative setting than is being reported, but you'd still just be guessing. There's a table in the back of our AOM that provides a relationship of runway conditions to RCC values. Wet is damp or standing water up to 1/8in, RCC 5. There's also a slippery when wet for excess rubber, RCC 3, which is probably what they actually had and if it was reported would most likely have prevented them from attempting to land. But when you're given an RCC of 5 and "braking action good" by the Tower it's hard to argue with their decision based on what they knew at the time.
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Old 19th Dec 2018, 11:43
  #176 (permalink)  
 
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The report of the rain increasing to +R should cue any crew to downgrade to medium braking for calculations.
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Old 19th Dec 2018, 13:10
  #177 (permalink)  
 
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Sig, interesting views.

Because ‘slippery when wet’ is additive, not directly related to weather or runway contaminants, it might be better used to reduce the assessed braking action; select the next lower value.

‘Tower’ information is advisory; it might be the best assessed or calculated, or their best guess by looking out of the window, worst still, incorrectly passing on a PIREP.
None of these remove the need for reassessment according to the situational conditions.

Some operators have a rule of thumb which linked any red WXR over the airfield in the preceding 15 min, to the assumption of a flooded runway.

Risk is not determined by assessing what is known, it’s the understanding of what is not known and possible consequences of the knowledge gap.

Last edited by PEI_3721; 19th Dec 2018 at 13:28. Reason: typo
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Old 22nd Dec 2018, 17:37
  #178 (permalink)  
 
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At my operator, +RN equals a Runway Condition Code of 2. That would limit the tailwind to 5 knots. However, the braking action report of GOOD from the preceding aircraft could have upgraded the BA to GOOD and possibly allowed the landing, depending on weight.
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Old 23rd Dec 2018, 14:29
  #179 (permalink)  
 
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Unfortunately, we'll never know.
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Old 24th Dec 2018, 05:52
  #180 (permalink)  
 
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One of the first posts in this thread quotes aviation-safety.net's web page that claims "Aircraft damage: Minor". It looks like the cowlings are resting on the ground, although aerial views online do not clearly show scrap marks on the EMAS blocks, with blocks costing around $2000 each average, not including labor. Is there anyway this accident is minor, or does a minor accident go up to a few million dollars in repair costs?
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