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View Full Version : Southwest Airlines suddenly grounds scores of planes due to aircraft weight issues


underfire
14th Aug 2018, 15:43
How does this happen and what the heck does it really mean?

"Southwest Airlines (http://companies.bizjournals.com/profile/southwest-airlines/135171/) abruptly grounded 66 Boeing (http://companies.bizjournals.com/profile/boeing/124397/) 737 aircraft in its fleet last Wednesday after issues with the carrierís aircraft weight records were discovered.
In an internal memo to employees on the matter that was obtained by the Chicago Business Journal, Southwest said: ďToday (Wednesday) we discovered the weights being sent to our Dispatch Operation did not match our other weight records for a number of aircraft in the fleet. As a result, and out of an abundance of caution, we have stopped flying those aircraft to recalculate the weights of the aircraft in question and reset the program.Ē
Aircraft weight is important because dispatch personnel and pilots need the correct information to determine the amount of fuel to load and other data needed to safely operate a flight."

https://www.bizjournals.com/chicago/news/2018/08/13/southwest-airlines-suddenly-grounds-scores-of.html?ana=yahoo&yptr=yahoo

Bigpants
14th Aug 2018, 15:59
Erm, go with the higher weight from the two sources and operate with reduced passengers loads until the data issue is resolved? Any safety reports to suggest this is a serious airworthiness issue?

pattern_is_full
14th Aug 2018, 16:21
Mnnh - SWA, particulary with regards to aircraft records, is getting "the fisheye" from the FAA at the moment. As well as a lawsuit, both stemming from the fatal engine explosion near Philly. A time to make sure all the i's are dotted and t's crossed.

And the backstory is, the FAA itself is getting some flak and oversight (IG investigation) for perhaps being too "chummy" with operators.

"An abundance of caution," as the memo states.

As to how it happens - weight may "accrete" on an air frame, as things like passenger wi-fi, or even flight systems, get added or upgraded (or even removed). And maybe not all departments "get the memo" of the change to aircraft N000SW's weight, so the records don't match. Big corporate bureaucracy (or perhaps too small and overworked a corporate bureaucracy).

Eric Janson
14th Aug 2018, 16:23
It's possible the higher of the 2 weights may also be incorrect.

Sensible to ground the aircraft as a precaution imho.

aterpster
14th Aug 2018, 16:35
And the backstory is, the FAA itself is getting some flak and oversight (IG investigation) for perhaps being too "chummy" with operators.

Some things never change. Shortly after the Decmeber 1, 1974, TWA 514 CFIT, TWA's POI was transferred. Rumor had it that he was too chummy with TWA's flight ops management.

lomapaseo
14th Aug 2018, 16:41
either it meets the FARs or not, "chummy" has nothing to do with it, except for how long it was out.

Of course the bigger issue is what went wrong in the process at SW end..

fokkerjet
14th Aug 2018, 16:41
...with the merger between Southwest and airTran, airTran had 66+ B737-700's in their fleet.

pattern_is_full
14th Aug 2018, 17:03
Lomapaseo

Well, "chummy" can mean the local FAA guy him(her)self doesn't cross-reference all the weights on file: in the onboard W&B paperwork; in the airframe's FMS; in dispatch's paperwork; in the maintenance records; in the master file at HQ. Never assume that even "good guys" can't get a little lax, now and then, trusting the operator's processes because they are also "good guys/gals."

I'm not knocking either the FAA or SWA (for whom the fatal event was their first (onboard, aircraft failure) in 51 years) particularly - human mistakes can creep in anywhere. You catch 'em, you tighten ship.

er340790
14th Aug 2018, 17:53
I am convinced the biggest risk on aircraft weight remains the under-calculation of pax + carry ons. This despite the recent mandated FAA et al increases.

In 2013 the H&S dept of our N. Canada mining operations did a full verification of our rotational personnel. Yes, these flights were over 80% male and miners are probably larger than the average male, but....

The result???

Summer 278 lbs.

Winter 291 lbs.

Enter those kind of figs into the last Weight & Balance you personally calculated and you'll see where I'm coming from.

OldLurker
14th Aug 2018, 18:00
Is this related to the issue of fleet weights discussed recently in Tech Log?
changing registration on Loadsheet.... (https://www.pprune.org/tech-log/612092-changing-registration-loadsheet.html)

BAengineer
14th Aug 2018, 18:34
Erm, go with the higher weight from the two sources and operate with reduced passengers loads until the data issue is resolved? Any safety reports to suggest this is a serious airworthiness issue?

Legally you are not allowed to despatch an aircraft without knowing the correct weight. As they cannot determine which record is correct, if any, then they had no other option.

PAXboy
14th Aug 2018, 22:22
Classic example of the 'Normalisation of Deviance'. Best to stop because, irrespective of the laws quoted above, losing a single pax life is not good for anyone.

Anilv
15th Aug 2018, 02:21
Its not only the weights, the weight document from technical services will also indicate the centre of gravity (basic index) which the starting point to calculate the aircraft CG and have %MAC.

B2N2
15th Aug 2018, 02:33
Sensible to ground the aircraft as a precaution imho.

I beg to differ.
Itís nothing but an excercise in paperwork.
Amd Iíll tell you why it doesnít matter.
íStandardí FAA passenger weights have left the realm of reality long time ago.
Even with everything averaged at least 50% of pax exceed their allotted weight.
So on a full airplane load letís say 70 pax exceed by an average of 20lbs that means W&B is already 1400lbs off. Add to that the fact that carry on is not weighed and youíre already passed 2000 lbs.
What may have happened on some of the airplanes is that seat configurations were changed and maybe not noted.
In any case the airplanes could just as well be lighter then the paperwork says they are.

B2N2
15th Aug 2018, 06:04
Just to clarify, paperwork errors make the airplane 100% illegal to fly while it is still 100% safe to fly.
Because youíre already 3000lbs off to begin with...and thatís on a good day.

pattern_is_full
15th Aug 2018, 06:32
Underfire - I'm pretty much with you. Gallup reports that U.S. men self-reported weights that averaged out to 191 lbs (women, 159 lbs). One may think that even those are low (due to vanity) but the same groups reported that their ideal weight would be about 20 lbs less (they were honest enough to admit they were a bit - chubby). 25% of men admitted to 200+ lbs; 29% of women admitted to 175-200+ lbs.

So the FAA numbers are about right - IF one excludes clothes and carryons, and only counts flesh. And 20 pounds shy with those added (in my case, the real extra weights are below the assumptions most of the time, if not, sadly, the body weight ;) I weighed my winter overcoat - 3 lbs)

OTOH, let's take, oh, a nice average 737-800 with 2-class seating. 160 people plus babes-in-arms and crew = 180 x 20 = 3600 lb error. Given a MTOW for the 738 of 174,200 lbs, that is a 2% error. 157 feet/50 m on a nominal MTOW takeoff run, negligible in terms of exceeding MTOW unless one habitually flies with full tanks.

Redo the math as needed, for an Islander or an A380.

Nevertheless, I'm all for some updated statistics from which to "average."

Ian W
15th Aug 2018, 15:56
...with the merger between Southwest and airTran, airTran had 66+ B737-700's in their fleet.

This is the most interesting and potentially apposite comment so far. Perhaps Air Tran methods/standards were different and when put into the SWA system the calculations did not work. A simple ontological problem could cause that if there is no Boeing standard.

DaveReidUK
15th Aug 2018, 16:19
...with the merger between Southwest and airTran, airTran had 66+ B737-700's in their fleet.

Of which SWA inherited 52, I believe, so that doesn't account for all of the 66 grounded 737s.

Hussar 54
15th Aug 2018, 16:36
Did we not have a discussion on here a couple of years ago about the Irish VLCC ' gaining advantage ' by registering some / all its fleet with lower gross weights in order to benefit from lower En Route Charges from Eurocontrol ?

Something similar at Southwest, perhaps ?

KenV
15th Aug 2018, 19:32
Did we not have a discussion on here a couple of years ago about the Irish VLCC ' gaining advantage ' by registering some / all its fleet with lower gross weights in order to benefit from lower En Route Charges from Eurocontrol ?
Something similar at Southwest, perhaps ?Really? They did it on purpose to "gain an advantage" with 66 out of over 700 of their aircraft and then suddenly changed their mind and grounded those aircraft? Excuse me if I sound a bit incredulous.

HarryMann
15th Aug 2018, 23:34
I am convinced the biggest risk on aircraft weight remains the under-calculation of pax + carry ons. This despite the recent mandated FAA et al increases.

In 2013 the H&S dept of our N. Canada mining operations did a full verification of our rotational personnel. Yes, these flights were over 80% male and miners are probably larger than the average male, but....

The result???

Summer 278 lbs.

Winter 291 lbs.

Enter those kind of figs into the last Weight & Balance you personally calculated and you'll see where I'm coming from.
haha.. double my weight !

B2N2
16th Aug 2018, 00:24
Iím thinking maybe a configuration change in number of Economy class seats, Preferred seats and whatever else they call them.

Hussar 54
16th Aug 2018, 09:36
Really? They did it on purpose to "gain an advantage" with 66 out of over 700 of their aircraft and then suddenly changed their mind and grounded those aircraft? Excuse me if I sound a bit incredulous.

It was just a thought about the ex-AirTran aircraft....

I think the discussion about the Irish VLCC was something along the lines of as long as they were flying comparatively shorter stage lengths and so were rarely carrying full fuel then it could be that the aircraft never departed at the manufacturer's MTOW....Or something like that....

But as I said, just a thought...

.

txl
16th Aug 2018, 14:17
Interested PAX here. I always wondered what the average figures for calculating passenger weight are. Is that a global standard?

underfire
16th Aug 2018, 17:03
Aviation Watchdog Investigating FAA Oversight of Southwest Airlines (https://thepointsguy.com/news/aviation-watchdog-investigating-faa-oversight-of-southwest-airlines/)

b1lanc
17th Aug 2018, 00:32
Iím thinking maybe a configuration change in number of Economy class seats, Preferred seats and whatever else they call them.


Or maybe had to relocate a few to accommodate mini horses as service animals as announced today.....

MarkerInbound
17th Aug 2018, 03:22
Interested PAX here. I always wondered what the average figures for calculating passenger weight are. Is that a global standard?

In the USA it's 190 pounds in the summer and 195 in the winter. There are separate male/female numbers of 200/205 and 179/184 but everyone I know just uses the average. Children up to 12 are 82/87 but most times they are just counted at 190/195 also. Sometimes when trying to carry a jumpseating crewmember on a weight restricted flight I've heard Captains asking if any of the pax are children. Two kinder would allow the jumpseater.

No idea if the numbers are standard around the world. The FAA raised the numbers several years ago after a Beech 1900 crash in CLT. They said they would monitor American weights and adjust as necessary.

groundagent
19th Aug 2018, 05:35
Did we not have a discussion on here a couple of years ago about the Irish VLCC ' gaining advantage ' by registering some / all its fleet with lower gross weights in order to benefit from lower En Route Charges from Eurocontrol ?

There is another European LCC who does/did this. Not sure about a previous discussion, but they registered lower Max weights for the fleet. The weight of the aircraft was what it weighed but the max payload was reduced. From memory, the structural limit was around 71T, one group reduced to around 64T, another to around 62.5T and some more to around 60.5T. No idea of the saving it generated but with large fleets, even small amounts will help and go straight to the bottom line.

fox niner
19th Aug 2018, 06:11
Lowering the max TOW is standard practise at klm as well. There are scores of 737ís with a max tow of either 70t, 71t, 72t, instead of the official 73,8t. (-800)
or 61t for the 737-700, which is officially 64.something. Saves a huge amount of hard cash.
not only RYR does that.

meleagertoo
19th Aug 2018, 12:37
A few years back one of the UK locos ran an exercise to check the accuracy of their weights. Aircraft were weighed in the hangar during maintenance to verify actual weight against the recorded figures and also selected at random as they entered the apron after a flight and directed onto a stand equipped with pressure pads. They were marshalled carefully onto the three pads and after about a minute, if even that, were able to disembark pax normally. Results were correlated with the flight papaerwork and processed.

Results showd the standard weights used were remarkably good, iirc something like a 2-300Kg deviation from the paper figure which on a 60t aeroplane is extremely accurate.

waito
15th Oct 2020, 19:27
Temporary grounding of 115 737-800 at Southwest took place due to weight difference of 75lbs in IT vs. actual mass. Took some days until half of the fleet returned to service. Reported to be a difference <0.05% of MTOW.

from aero international magazine

Safety matters, but isn't this a bit surprising?

andrasz
16th Oct 2020, 11:28
Did we not have a discussion on here a couple of years ago about the Irish VLCC ' gaining advantage ' by registering some / all its fleet with lower gross weights in order to benefit from lower En Route Charges from Eurocontrol ?

This works primarily in Europe, where landing fees and Eurocontrol charges are all driven by a MTOW based formula. In the US these charges are per movement or category based, so playing with the weight figures for a given aircraft model has no effect on operating costs.

TotalBeginner
16th Oct 2020, 11:56
As to how it happens - weight may "accrete" on an air frame, as things like passenger wi-fi, or even flight systems, get added or upgraded (or even removed). And maybe not all departments "get the memo" of the change to aircraft N000SW's weight, so the records don't match. Big corporate bureaucracy (or perhaps too small and overworked a corporate bureaucracy).

Would it not make sense for the flight crew to complete their own weight and balance calculation using an EFB or similar device? This way the airline can ensure that they have up to date records of their own fleet weights without having to worry about disseminating the information to all of their handling agents and auditing it. The handling agent present a loading form with passenger weights, distribution and load in compartments for the flight crew to enter into their own EFB. Similar devices are used for computing takeoff performance, surely adding a WB function wouldn't be too difficult?

old,not bold
16th Oct 2020, 18:38
Ummm...isn't that the point of using an average weight? If 50% are over the average, the other 50% can only be less than the average. So all is OK.

Just sayin'.

The real problem is that frequently it's not 50% who are fatties and over the assumed average weight, it's 80%, especially when they lug on board 25 Kg of "cabin baggage" that no aircraft is designed to accommodate.

Dannyboy39
17th Oct 2020, 14:00
Lowering the max TOW is standard practise at klm as well. There are scores of 737ís with a max tow of either 70t, 71t, 72t, instead of the official 73,8t. (-800)
or 61t for the 737-700, which is officially 64.something. Saves a huge amount of hard cash.
not only RYR does that.
And its not just in Europe. The AFM will likely show 70,999 or 71,999 for instance. This is not an unusual occurrence.
On the Airbus, you have multiple WVs.

India Four Two
17th Oct 2020, 16:07
Originally Posted by txl View Post (https://www.pprune.org/rumours-news/612187-southwest-airlines-suddenly-grounds-scores-planes-due-aircraft-weight-issues-2.html#post10225452)
Interested PAX here. I always wondered what the average figures for calculating passenger weight are. Is that a global standard?
Here are the numbers for Canada. Note that the adult weights in the table include a 13 lb allowance for carry-on:

https://cimg9.ibsrv.net/gimg/pprune.org-vbulletin/802x735/screen_shot_2020_10_17_at_09_01_16_936ecc059619fa0275dd50a8d afeae6342b9b58c.png

https://tc.canada.ca/en/aviation/reference-centre/advisory-circulars/advisory-circular-ac-no-700-022

MarkerInbound
18th Oct 2020, 19:34
andrasz

Had some 727s at an old job, exNW airframe converted freighters, the landing weight had purposely been lowered to reduce the landing fee paid. We sent a check to Boeing and in a few weeks had new placards raising the max landing weight 4000 pounds.

NWA SLF
19th Oct 2020, 17:59
I remember several years back taking a co-worker to the airport for a flight to Sydney on a very small airline. Earlier that year they had experienced a fatal crash. One thing I had never seen before was weighing each passenger and when everyone was checked in, assigning seats. Second was that the pilot got a fuel sample from the fueling truck, took it into a back room, and after a few minutes came out and gave the fueler the okay to proceed. Too bad it took a crash to tidy things up.

GlueBall
20th Oct 2020, 10:40
It's hard to imagine taking 66 jets abruptly off the line when as many available jets are roosting in the sun at VCV, plus the now recertified 34 Max jets.

Icarus
20th Oct 2020, 11:46
txl No here is not a global standard; there are 'regulator' standards and should an airline choose to do so, they can seek approval for their own standard passenger and baggage weights. There is a strict process and mathematical model behind the derivation of the standard weights published, used and approved. Typically they are derived from a study of real passengers (actually weighing many hundreds if not thousands across a population at the aircraft side, including all hand baggage) and the numbers run through standardisation methodologies with a confidence interval of 98%. Meaning that the average weights applied for Male, Female, Child and Infant (including hand baggage) is accurate to within +/- 1%. Same for those that use a standard, as opposed to actual, baggage weight for mass and balance calculations prior to a flight departure.

DaveReidUK
20th Oct 2020, 12:59
plus the now recertified 34 Max jets.

SWA are no more able to fly their grounded MAX aircraft than any other operator is.

bekolblockage
21st Oct 2020, 03:50
pattern_is_full

Disclaimer: Not PP (not for 30 years at least) but ATC and flight procedure designer.
While an extra 50m on the take-off run might not faze you, I would have thought even that extra 2% would start to worry you in a OEI situation. That margin between the book climb rate figure and the 1.6% contingeny surface (only ~100 ft/NM ) starts to get pretty thin doesn't it?.
We already have (or had) problems with ULH brand new generation large twins unable to take default SIDs under common temp/pressure conditions for our location due to OEI issues.

Ex Cargo Clown
21st Oct 2020, 15:55
Having worked with 744Fs, I always kept my eye on the reg as quite often the DOW was different.

Sailvi767
24th Oct 2020, 13:44
TotalBeginner

The calculations are dynamic in that the ground handlers have to start running calculations even before the aircraft is loaded so they know where and how much cargo can be placed onboard. This has to be tied in with how many passengers and where they are seated. The numbers are run many times in the course of loading a aircraft prior to departure. Many operators build a tolerance into the numbers to allow for last minute adjustments by the flight crew without rerunning all the numbers.
You can’t just load the aircraft and hope the numbers will be within limits.

Chris2303
24th Oct 2020, 22:27
What happened to the idea of scales on the landing gear? (Put very simplistically)

TotalBeginner
25th Oct 2020, 21:12
Sailvi767

I'm not sure that's the case for an aircraft like the B737. There are plenty of A320/B737 operators here in Europe who use a standard load plan and then just allow the Departure Control System to monitor passenger distribution. I'm also reliably informed that there are a few large European LCCs who perform the W&B calculation in the flight deck.

STN Ramp Rat
25th Oct 2020, 21:17
If its passengers and baggage only that's possible, the moment you introduce Cargo and DGR than it requires ground based professionals. This thread and the recent Wizz Air one have highlighted to me how little most flight deck crew know about weight and balance, and how many assume what their carrier does is what everyone does.

FlightDetent
26th Oct 2020, 00:14
Better yet, insert trim tanks. Admittedly the way some very shrewd people managed to cut the flesh off with some single equipment operators is admirable. Same as anywhere else, it only works as long as it works.

ShyTorque
26th Oct 2020, 00:30
What happened to the idea of scales on the landing gear? (Put very simplistically)

It added too much weight.....

Maninthebar
26th Oct 2020, 08:21
That is VERY good

Also a good bit of Heissenberg in action - you can't make an observation without changing the observed

Gipsy Queen
3rd Nov 2020, 23:37
ShyTorque

Why could the function not be performed by a simple strain gauge? These things weigh little.

DaveReidUK
4th Nov 2020, 07:38
At a guess, they would require to be calibrated periodically.

By weighing the aircraft. Which would be kind of self-defeating. :O

STN Ramp Rat
4th Nov 2020, 15:17
I always understood that it was not possible to have any method of weighing linked to the aircraft because, even on the ramp, a relatively small wind provides lift and changes the readout.

tonytales
4th Nov 2020, 21:45
There were on-board weighing equipment on several aircraft including some B747 classics. One system was to check the gas pressure in the oleo struts. Pressue in the oleos goes up as weight increases as one can see during refueling. Problem was struts are "sticky" and hang up and go down in jerks and bumps.
There were some aircraft equipped with strain gauges, I think it was on the bogie beam. Problem there was the harsh environment they lived in on the landing gear. Very hard to maintain and how do you check for accuracy and at what intervals?
As an aside, one of the most tedious exercizes is weighing an aircraft. You have to check for the presence (or absence) of each and every item of ships equipment listed and get unlisted items off. Has to be done in a hangar to prevent wind-loads and rain from causing errors. You also have to drain fuel, etc. Weighing got a lot easier though with portable roll-on scales. Beats having to use load cells on the jack points which I have seen partially twist. Very scary to have an airplane jump off its jacks. It didn't fortunately in my case but I have seen the very large holes a jack makes in wing planks. That was caused by an operator trying to do a gear swing outdoors. Wind came up and aircraft jumped a wing jack. Very ugly.