View Full Version : TUI planes takes off 1200 kg overweight after software error

9th Apr 2021, 03:33
Tui plane in ‘serious incident’ after every ‘Miss’ on board was assigned child’s weight Service from Birmingham to Majorca took off with less thrust because pilot thought it was 1,200kg lighter

An update to the airline’s reservation system while its planes were grounded due to the coronavirus pandemic led to 38 passengers on the flight being allocated a child’s “standard weight” of 35kg as opposed to the adult figure of 69kg.

The Guardian, 9 April 2021 (can't post URL sadly)

9th Apr 2021, 04:58
Here it is:
Grauniad: TUI incorrect weight (https://www.theguardian.com/world/2021/apr/09/tui-plane-serious-incident-every-miss-on-board-child-weight-birmingham-majorca)

9th Apr 2021, 05:26
Yep been done before

9th Apr 2021, 07:07
Wouldn’t date of birth be a better data point to determine whether someone is a child? And is 69kg really the average adult weight in the UK?

9th Apr 2021, 07:16
I know what you mean but it'll be an assumed Female adult average weight ......and since you asked...


See Table 4.17 on page 87.
​​​​​​​ (https://www.easa.europa.eu/sites/default/files/dfu/Weight%20Survey%20R20090095%20Final.pdf)

9th Apr 2021, 07:17
Given the size and obvious weight of some of the rucksacks regularly being hauled on-board, perhaps a more accurate estimate of hand-luggage weight :-)

9th Apr 2021, 08:44
Not much (thankfully!) in the AAIB bulletin for April as no flying - once Commercial and GA returns to normal levels the monthly bulletins will be the size of the yellow pages!

Actual AAIB article for this one - https://www.gov.uk/aaib-reports/aaib-investigation-to-boeing-737-8k5-g-tawg-21-july-2020.

"Subsequent use of the actual takeoff weight for performance calculations showed that all departure airspeeds should have been one knot greater than those used on the incident flight, and the thrust required should have been 88.9% N1 compared to the 88.3% N1 set on the incident flight."

9th Apr 2021, 09:36
Well in the past, our aircraft; (extinct Luton based airline), were sometimes heavier than we thought, because we used standard passenger weights. Once in the cruise, I used green dot to work out the actual aircraft weight and it was sometimes 2 tonnes above what we had calculated at the gate.

One season, we subbed for another Luton based airline, and their standard weights were higher - 93 kg for a male, whereas we used 88kg - I cannnot recall the female figures.

And yet there was a hell of a fuss if the wrong catering weights were used - even though that only made an error of a few hundred kilos.

9th Apr 2021, 09:48
I suppose this is classed as a miss(hap)? :)

But seriously just as well they weren’t performance limited. I’ve often wondered how accurate the weights on a load sheet compared to reality. On a previous type the relation between Vref and weight varied by about 1 knot per three tonnes.

9th Apr 2021, 10:21
I always assumed that we were at least a ton heavier than the load sheet suggested., just look at the size of the passengers boarding (and the amount of cabin baggage)
Management will always want you to reduce to the limit but I always kept a little in hand, eg using performance from an intersection, then departing from full length.
It is your neck, not theirs.

Ollie Onion
9th Apr 2021, 11:48
Planes are regularly overweight. When departing at MTOW do we seriously think the average weights used are accurate for people or bags?

9th Apr 2021, 12:28
Relatively speaking the error was minor as 1200kgs would be less than 2% of the MTOW, though obviously it shouldn't have happened and procedures need to be put in place to ensure it doesn't happen again.

Narrow bodies are much more forgiving of incorrect take off calculations than wide bodies, particularly when operating at airports designed to accommodate the larger variants, though a South American cargo B727 was lost when all the holes in the Swiss cheese lined up. https://en.wikipedia.org/wiki/Aerosucre_Flight_157

Wide bodies are a different ball game with numerous accidents and near disasters happening because of incorrect take off data, the recent SAA A340 comes to mind.

9th Apr 2021, 15:23
If the aircraft is overweight it will show up in the fuel burn. At my airline we almost always underburn verses the flight plan so I suspect the weights are pretty accurate. 69 kilo’s is probably about 15 kilos short of the true average female boarding weight. The US uses 84 kilos for female winter weights. 79 in the summer.

9th Apr 2021, 15:48
Reading the report - it wasn't overweight, the actual load showing they were over 12T below MTOW.

From the AAIB report

Whilst an incorrect takeoff weight was used for aircraft performance planning, the thrust required for the actual TOW and environmental conditions (88.2% N1) was marginally less than the thrust used for the takeoff (88.3% N1). This meant the safe operation of the aircraft was not compromised.

Which in my mind reads, nothing to see here, move on...

9th Apr 2021, 16:57
To be honest, I am actually amazed that anyone even noticed.

9th Apr 2021, 19:50

Or its the result of a sound safety culture that means the most inconsequential of events is treated with the appropriate level of seriousness, introducing new procedures and accountability which go on to prevent further events reoccurring.

9th Apr 2021, 20:13
Anyone able to comment on why narrowbodies are less susceptible to 'overloading' that widebodies ? Is this to do with reynolds number as weighrs and scale goes up?
I clearly remember a colleague routinely overloading an 5000lb aeroplane by 500lb or more, 10% and scoffing at the idea that it was unwise. (US pilot). Certainly the Caravan didn't show any distress though runway analysis (or common sense) wasn't involved.
Later I flew the 146 where afair weights for performance were pretty carefully defined and was astonished on conversion to the 737 classic where Boeing's performance book figures made little issue of half a ton or so either way. At that point massaging the loadsheet to comply with individulal kilos was thought more important than whether the aeropalne could take off, reject or land at the calculated weight by a factor of 500 or so which isn't very rational.
Structural reasons are a different matter; I'm curious why widebodies (does that actually mean 'heavies'?) are more susceptible to overloading than other(lighter/smaller) ones?

9th Apr 2021, 21:33
If I recall correctly the FAA mandated an increase in the average weight estimate per passenger as the rate of obesity increased in the USA.

At one point/once upon a time checked luggage was weighed as it was checked in.

When airlines started charging extra for checked luggage rather than carry-on, presumably they lost track of however many extra pounds people would stash in their carry-on luggage to avoid getting charged an extra $60 or whatever.

I know that I try to carry everything I can with me, if only to avoid the concern about it getting lost at a transfer point, or to skip the wait in the baggage area.

9th Apr 2021, 21:50
Is it a “software error”? Or is it a software “user error”?

9th Apr 2021, 21:53
Dannyboy - Quite agree that appropriate action is taken... But it has, hence my comment (probably stems from the fact I don't really like the title of this thread - The aircraft wasn't overweight but had 1200kg unaccounted for).

meleagertoo - Just in my experience and I don't call this 'overloading', but incorrect performance. Most shorthaul airliners flying out of moderate to large runways are frequently performance limited by the climb, not the runway length. Thus if a performance error occurs, usually there's little perceived problem due to both engines (hopefully!) running thus no actual issue with the climb segment. Going to longhaul aircraft, the performance is quite often runway distance limited - stop margins of 0m are frequently seen in the performance software despite moderate weights and 4km runways. Thus if the performance is run slightly incorrectly, then the perceived problem of the end of the runway is very apparent.

9th Apr 2021, 22:23
The TUI B737 was overweight for the performance figures used, meeting the requirements at its actual weight could involve different speeds and power settings.

An aircraft is required to be operated within its certification limits, go outside those and you become a test pilot. Center of gravity comes into play as well if you are overloaded, particularly in the event of an engine failure. If an accident occurs, the loadsheet is one of the first things to be checked and the insurance company will be looking for an excuse to get out of paying.

A while back, I was a pax on an ATR42 operating out of a limiting airport and everyone had to stand on the scales during check in. The take off involved stopping on the runway and powering up against the brakes so I was quite happy to know that the pilot was working with actual weights.

9th Apr 2021, 22:41
And yet the fuel gauges are only required to be accurate to +/-2%, which is quite a lot on a large aircraft...

9th Apr 2021, 22:49
Is it a “software error”? Or is it a software “user error”?

The former.

9th Apr 2021, 23:42
According to the report, a software error: the software was written in a country where "Miss" is only used of children (does anyone remember when boys were called "Master"?) Presumably not in fact the English word "Miss" but a word in some other language which kind of half translates to "Miss." A subtle example of the perils of outsourcing, if this was the cause.

10th Apr 2021, 22:53
Given the increasing use of software/firmware in various aspects of the transport fleet today (not just aircraft) I think this is the most important point to have come out of this incident.

What is worrying to me is that the country in which the software was written is not identified in the report. If a report is to have validity, and to be of some use in preventing future incidents or accidents, then I would expect full disclosure on causal factors.

As this report rests at the moment, if I was relying on software for a critical task 'written in a[nother] country' I'm still none the wiser as to whether I should be checking/expecting such errors to occur. If I was charged with conducting the 'initial risk analysis' on a system for example I'd like to have a headsup as to whether this is an area I should consider at increased risk of error should the software/system originate from say, Norway, India or Russia for example?

The following excerpt from the report shows what I consider to be a deficiency in the report and which could itself lead to further non-identification of risk factors (my underlining):

"The incident occurred due to a simple flaw in the programming of the IT system, which was
due to the meaning of the title ‘Miss’ being interpreted by the system as a child and not an
adult female. This was because in the country where the system was programmed, Miss is
a child and Ms is an adult female. This issue had not been identified as part of the initial risk
analysis and did not manifest itself during the trial simulations."

10th Apr 2021, 23:04
Can I just add, acknowledging that I am not a professional of aviation or data processing, that I am surprised and worried that an item like the passenger weight allowance should be automatically filled in from the honorific? I mean, Dr, Prof., the Revd--these immediately leap to mind as being non-gender specific honorifics in common use in Anglophonia, just for starters.

11th Apr 2021, 03:57
Bullseye! The weight context for passengers per regulation is based on age. The system has the birthdate and should label/populate the passenger element accordingly. Using "titles" is plonkers of a job at the SW definition phase, regional customs or language notwithstanding.

And the proper ones do. I ran once into an issue of an infant turned child between the check-in time and loadsheet closure. Partly for us being late and it has become a substantial headache on a full flight. Tirana in Albania it was.

As long as some are looking to point fingers, perhaps it's the business choice of TUI not to use proper industry-grade systems which deserves the attention. Or (to demand and pay for) proper aviation-style validation procedures, i.e. white-box testing.

11th Apr 2021, 19:29

The problem is not so much which country might have been involved - it really shouldn't matter - the initial risk analysis should be done by the system owner/operator, in this case, the airline. Secondly, the fact that the problem did not manifest itself during the trial simulations simply means that the test schedule was incomplete and inadequate. Both issues should be managed by the system owner, even if the work is done by another agency.

Notwithstanding that, in this instance, the impact on the flight was insignificant, particularly given the approximations and other inexactitudes involved in loading calculations, the potential for a more serious event to occur as a result of similar process failures should be of concern.

Roj approved
11th Apr 2021, 23:01
Many years ago doing a 1hr sector to a holiday destination in a 321, lots of passengers that “enjoyed” fast food and free carry on luggage.

At transition (10,000ft) a quick calculation of the FOB + Fuel Burn and all was well, but then I glanced at the GW on the Lower screen.

Recalculating the numbers, FOB+FB+ZFW= 1.8 T more than an our Calculated TOW. Our projected LW was only 1.2T less than our Calculated TOW for a 3T burn.

So, the FAC calculated GW was 1.8T higher than the Calculated TOW??? The Alert for incorrect data entry only happens at ~7T

At the time we were still using the paper T/O tables, so lots of factoring was built in, especially by the crew, thankfully.

I reported it to the company, there was an investigation. Changes were made and shortly after the weight used for Males and Females was changed to be the same, 83kg.

The 83kgs includes 7kg of carry on, bags were checked for weight and size with the heavier/larger bags going underfloor at a very exorbitant charge. This has become a very profitable revenue stream.

I look at the pax sometimes and wonder if this is enough. I’m 5’7” (172cm) and am 80kg, there are a lot bigger people than me.

The company continued to have issues with the boarding programs and had more incidents of incorrect paperwork being ACARS’ed to the aircraft. Ie: one flight took off with 150 on the manifest, but actually had 180 onboard.

Major errors were found with the boarding system, it took more than 12 months to sort it out, and we still have to conduct a headcount about 4/10 flights because they can’t seem to get it right.

I noticed our newer CEO’s don’t have any mention of this FAC calculation post take off in the manuals, but still mentions it for Approach speed calculations.

On the Wide body, summer/winter weights were scrapped, as were “Asian” weights, as it was found our pax were predominately Anglo and had maximum carry on.

12th Apr 2021, 08:46
Does the aviation industry not have software engineering standards ?

kiwi grey
13th Apr 2021, 01:49
The bean counters will tell you that would be far too expensive.
I'm sure they would rather just use much cheaper development techniques for aircraft-control systems, too, but the certification authorities won't let them for some reaaon.

13th Apr 2021, 07:38

What is this country?
Does anybody know?
India? Australia? Jamaica

13th Apr 2021, 14:11
If it was Swissport, I believe their load sheets are generated in Morocco or Kenya.

13th Apr 2021, 16:49
I believe the 64k question, unanswered, is where was the software upgrade written.

Kirks gusset
13th Apr 2021, 17:52
We often used "all adult weights" or "standard charter weights " which came close to 76KG an adult, probably so the baggage could be "legally loaded"! Looking at some of the Arab country and German pax, 70KG for a female was about half right and the male weight was ludicrously low. On 280 pax we could have early been 3000 KGs out, but as long as we showed an underload no one gave a hoot. The thrust difference on this flight was the width of a fag paper.

13th Apr 2021, 18:51
Given it seems to be pretty simple to cross check the actual weight from performance data when in cruise why not make a point of recording that in flight number and comparing it to the number entered on the ground.
Pretty quickly the operators would be able to see if pattern exists. Flights from certain locations, time of year - winter ski season comes to mind.
Also be a good way to catch software and provider busts.

14th Apr 2021, 00:09
The bags get weighed, the carry on too here, why not weigh the pax? It does happen in some areas of aviation and never seen anyone object.

14th Apr 2021, 02:56

14th Apr 2021, 03:45
Standard weights for pax are reviewed regularly and can be overridden by the loadsheet agent, a common example during training was if a group of Sumo wrestlers were travelling.. even here the crreection that you applied was an estimate. A colleague working for another airline which had a high traffic of Indonesian female workers (quite petite) applied for, and was granted a lower standard passenger weight for that sector. This resulted in more payload available for cargo.

When I worked for LH, the weights for short haul flights were higher than for long-haul, the rationale was that short-haul pax tend to have hand-carry luggage so this was factored in.

Confirmed Must Ride
14th Apr 2021, 06:36
AMC2 CAT.POL.MAB.100(e) states procedure on how to establish standard passenger weights

14th Apr 2021, 07:09

"The bags get weighed, the carry on too here, why not weigh the pax? It does happen in some areas of aviation and never seen anyone object."

I suspect that most baggage scales aren't capable of registering a passenger's weight, so a big investment in additional infrastructure would be required. Then there would be the additional terminal capacity needed because passenger throughput would be slowed down.

14th Apr 2021, 08:31
In these days of on-line check in, etc, I think any move to get those travelling light, travelling frequently to the airport early to stand on scales at the gate would not be well received....and if you have to wait until you have weighed the last pax before "closing" the flight and being able to prepare a load sheet the consequences would be interesting.

14th Apr 2021, 20:05
Back in the day when I was a check in agent for NZNAC at WLG we used to have to weigh pax fairly frequently, usually on DC3 flights but sometimes on the nonstop WLG-DUD flight on a winter time V807 flight.

There was usually no kickback from the pax, but back then people were generally more intelligent than they are now

14th Apr 2021, 20:20

I started my aviation hobbyism as a spotter at Leeds/Bradford in the seventies. The present runway is, in the local vernacular "not o'wer long" but in those days it was only 5400 feet. Britannia used 737-204ADV kit off there as far afield as Palma and, for a while Tunisia. Not uncommon to see pax being weighed at check in, using the baggage scales, so as to establish if a 'splash and dash' at Luton might be needed.

Much further back, in the fifties, my parents were weighed at Lands End (St Just) before boarding a Rapide for the Scillies.

14th Apr 2021, 20:46
Given it seems to be pretty simple to cross check the actual weight from performance data when in cruise
How do you do this in a 737? The FMC displays the zfw which is pilot entered from the loadsheet + the fuel quantity to give gross weight. Possibly you could go backwards through a cruise fuel flow table. The interpolation would be ninja, but then 3+hrs in the cruise is a long time, maybe something to try if I get back flying.

15th Apr 2021, 02:21
Much like Uplinker I noticed discrepancies between the loadsheet and Green Dot and other characteristic speeds on the 320 family. I started to keep track and make a record. According to Airbus variability within systems and instrumentation etc can lead to minor discrepancies of up to 3 knots. 1 knot = 1 tonne. However, the discrepancy should obviously be either side of an average - sometimes higher speeds and sometimes lower. According to what I recorded we were almost invariably adding 1-3 knots on each approach to makes sure Vapp was five knots clear of VLS. Often adding five knots to achieve the same.

The only major problem was that we were consistently operating short sectors and fuel tanking as much as possible. Our OFP planned for us to land at MLW - 500kg. I reckoned in reality were landing over max landing weight by a few tonnes very regularly - ie several times a day. Not a problem on a day to day basis but a serious issue for the life cycles of the airframe.

I raised the issue with management and that's as far as it went.

15th Apr 2021, 05:05
Some aircraft do « weigh » themselves. Freighter 747´s being an example. There are of course tolérances, and in the event of a big enough discrepancy the load sheet is taken as Gospel. So far from infallible. Then again what system is. As to installing it on pax aircraft, well it would be back to risk, added benefit vs the cost of installation and regular calibration. So it ain’t going to fly.
I assume most manufacturer’s build sufficient padding in to flex/ derate calculations to cater for most shortfalls or cock ups.
The average adult (Caucasian) male, or female for that matter, hasn’t weighed in at the notional weights for some years.

15th Apr 2021, 15:35
Many years ago I remember taking an A320 from NCL to LHR. During the take-off the aircraft felt 'sluggish', but on final approach to LHR it felt like it was wallowing all over the place.

During my usual 'good-byes' to the pax I noticed about 3 dozen of the biggest human beings I had ever seen close up. It turned out that we had the Newcastle Falcon rugby team onboard!

After re-checking the loadsheet, I saw that load control had used 'standard weights', but those guys were HUGE. I reckoned that we had been about 2500kgs heavier than the plan AND they were all sitting at the back of the aircraft. No wonder the aircraft was wallowing!!

I filed an ASR, and telephoned several departments and contacts, but I feel it just went into the 'too difficult' bin!!

15th Apr 2021, 15:36

The average weights are revised every few years - and they always go up at each revision.

kiwi grey
16th Apr 2021, 00:10

These days, a Super Rugby forward pack of eight behemoths usually weighs in between 900 and 920 kg, one weighing less than 875 kg would be regarded as 'a bit light'. So that's around 110 kg each in their rugby shorts, jumpers and boots. Add a couple of kg for street clothes and 7 kg (hahahaha!) for their carry-on and they'll be 120kg each. Surprisingly enough, the backs aren't an awful lot lighter. In a travelling team group, the physio is probably the lightest by some margin. Sure makes your 'standard weights' look silly.

18th Apr 2021, 05:55

I would suggest neither.

The code worked as designed, users (customers) acted in line with the application demands.

It is a business process design error resulting in computer code that manifests that error into a real world problem.

18th Apr 2021, 06:05

But was a 9% error v payload and thats where the focus really needs to be.

18th Apr 2021, 06:10
Out of interest, can anyone confirm the standard passenger weights used by TUI? Clearly 35kg for children and 69kg for Females; but what are the Male and Infant standard weights in use by them?

18th Apr 2021, 09:37
The 35kg and 69 kg tie in with the EASA "Holiday Charter " figures quoted in the 2009 survey I linked to upthread (I've also C&P'd that link below).

If they are using still the numbers from that matrix then for it's 83kg for a "standard" male...but obviously that is subject to confirmation.

Looking at our local (Southern France, not far from the Med,) general population I can see how the numbers might still be credible for a charter from the airport to say the Balearics ...elsewhere. :confused:


19th Apr 2021, 01:29
Thanks Wiggy, I had managed to reverse engineer it based on zero for Infants.

Bag wt not as reported by AAIB (150 x 14.5 + 35 x 16) but matches final weight data in report.

Old Grouch
19th Apr 2021, 23:44
I work in a big airline based at LHR. During the last year, we've flown many cargo-only flights on PAX A/C. In the last 3 months, I've had 3 occasions where the 'pantry code' on the loadsheet was set to freighter flight catering (~300kg), whereas the galleys were full-fit with catering carts for outstation use (~4600kg). We are not required, by formal company process, to check the galley loading on freighter flights, yet I do so, "to be sure". On each occasion, we were 4.3t heavier than on the loadsheet. On each occasion, a safety report was filed. How many times had incorrect pantry codes been used on flights, where the actual galley loading wasn't checked (and corrected)?

Sadly, the company reply to my 1st report was along the lines of "L/S error noted, however, be advised that the max weight difference before a new flightplan is required is 5t. Your weight difference was 4.3t, so a new flightplan wasn't needed". The reply to the 2nd report was "L/S error noted, however, in my opinion, this does not warrant a safety report, as the catering weights vary all the time". It really does beggar belief.

Confirmed Must Ride
20th Apr 2021, 07:20
Back in my old Loadplanning days we were allowed a 5T variation before new loadsheet required on narrowbodies and 10T on widebodies.

20th Apr 2021, 08:09
Let's not confuse the need to print-out a new edition as opposed to obligations to correct known errors manually by LMC.

Either way, not relevant to the story, IMO. The core message says the Q&S supervisor refused to acknowledge the seriousness of using wrong numbers.

Horrible. If anything like that was confirmed at a non-EU operator the outcries to ban them from entering airpace would be very loud.

24th Apr 2021, 03:35
Old Grouch

Nitpicking I guess, but as these items were not being used for catering, they should not be a component of the pantry (code) anyway - they should be accounted for as (non-revenue) payload (company stores perhaps). Perhaps a clearer policy in that direction would prevent future occurrences?

Also, most of the topic here in general has focussed upon the weight issues, no one seems to be looking at the balance implications, why is that? There are two important factors in play here all the time, weight and where it is loaded.