Incorrect weight calculation 737 3

[LittleInch]

This report has just surfaced

https://www.theguardian.com/world/2...miss-on-board-child-weight-birmingham-majorca

Basically the load sheet allocated a childs weight to everyone listed as "Miss" instead of an a adult weight for everyone with "Ms". Apparently caused by a revised IT program in an unnamed other country where miss is commonly used for children.

Now something the size of a 737 it may not have been a huge issue, but I'm sure I recall a smaller commuter plane of 20-25 people which stalled on take off and when they recalculated all the Actual weights of the passengers the plane was over weight. US airways flight 5481 -

https://en.wikipedia.org/wiki/Air_Midwest_Flight_5481

https://admiralcloudberg.medium.com...crash-of-air-midwest-flight-5481-caa032313df6

Other things contributed more to that crash, but overweight without realising it was a major contributory cause.

So maybe not an engineering disaster, but a near miss and is a reminder than generic assumptions still need to be checked against your specific design or operation.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[jhardy1]

About 20 years ago, I was booked on a scheduled inter-island flight in Fiji. When I got to Nadi airport, there was a huge scrum of people at the check-in. The airport staff weighed everybody and their baggage, and gave us all boarding passes - without seat numbers.

We then went out to the tarmac, and directed us towards 4 aircraft - two Short's Skyvans (the "Flying Shoebox" - seats about 18 passengers) and a couple of 8 - 10 seat low-wing twin-engine planes. I got on one of the smaller planes - the pilot was a stickler for doing things right, and made sure his plane was not overloaded. No attempt was made to match passengers and luggage. My bag was not aboard - he told me not to worry, it would be loaded on one of the other planes, as all were part of the same flight.

We were the first to take off, and an hour or so later, we put down at our destination. Shortly later, the second small plane landed. The two Skyvans landed almost an hour later - apparently, they had been packed to the brim with luggage, even using the centre aisle for bags and boxes. I'm sure they must have been overloaded, and apparently they had flown the whole way "low and slow". The locals seemed to just accept that this is how airlines operated, but a couple of the Western passengers on the Skyvans looked like they hadn't enjoyed the experience at all!

http://julianh72.blogspot.com

 

[verymadmac]

That's those horrible balance field take off, AKA we add just sufficient power to takeoff in available runway with stopping space if it all goes wrong at the worst point. I just don't understand how it is legal (tail scrapes, overruns etc are way too common) without a secondary independent check method, such as an accelerometer to ensure sufficient power has been applied (this would catch both weight and power issues).

Taxi over load cells in the taxiway is probably the best way to get a good number (but no body seems to physically weight aircraft before flight, not even the police helicopters which would love an extra 50 litres of fuel).

 

[Alistair_Heaton]

There are two sides to mass and balance. One is structural limitations and the other is performance which centres round one engine failing at the the wrong moment and the ability to keep the aircraft pointing in a straight line and climb.

All public transport aircraft are what's called pref A which means that they will climb.

You can actually go quiet far over the max mass and as long as both engines keep working nobody will die.

NOw these days we do what's called de rated takeoffs which use less fuel and lower the wear on the engines. In fact I haven't done a full power takeoff in the last 10 years. When you do them you have a get out of jail free card if you see the runway running out of manually firewalling the engines.

They are now working on a systems for measuring acceleration and issuing a warning if its outside the envelope. For both take off and landing.

 

[verymadmac]

I worked for a company that ran 737 freighters, those engines were all derated, and switched around so nearly every aircraft had an engine on hot watch.

Alister have you seen the graph of the effect of time in service verse the aircraft's factor of safety, it decays from 1.5 toward 1 and then at maintenance check is restored to 1.5 (its in the Boeing structures course notes). Its somewhat of fantasy but that applies both ways (plenty of oops out there, even in EASA land to chew through that 1.5).

One of the down falls of weight and balance is it assumes that the empty weight for the aircraft is right, weighting the aircraft is easy, making sure everything on it was recorded and the calculations of the "as prepared for service weight"* are correct is not. I found one aircraft they had counted the service carts in the empty weight, thus counting them twice in the aircraft weight.



*this adds in all that extra weight, of flight crew, documents, their bags, etc but no the cargo, fuel and passengers

 

[Alistair_Heaton]

no mate they keep that stuff well away from normal stick monkeys.

I have been through the trials and tribulations of weighing a Jetstream 32 in and getting its C of A for the G reg as the test pilot. As usual the claim that you just go there for 8:30 brief and you will be done by 16:30 was a complete and utter lie. 4 days later we eventually flew it and handed in a 2 page list of snags.

I never want to be involved in that crap ever again.

A de-rated engine is different to a de rated departure. With a full power you get what ever the engine is set up to produce as per your 1.5 thing. A performance de rate is when we reduce that even further to use the full runway distance. They can do it two ways either through a hard limit to the fadec limiting the power or use whats called flex temp which feeds a false outside temperature into the fadec which then reduces the max thrust.

The min that we can derate our 21k engines to is 17k I think. But we don't work with engine power ratings the performance app just gives us numbers to plug into the FMC which then speaks to the fadecs and then all we see is a required N1% and we cross check that with the app to make sure they are both the same. If when your rolling you believe that something is wrong you just push through the auto throttle which then disengages and hit the end of travel and then it defaults to emergency power and disregards the FMS info and then reverts to the fadec max hard limits which is probably set by your x1.5 thing.

BTW our 21k engines can be turned into 24k engines by a software change. The 24k aircraft are used in hot and or high airport routes. And when you need to use full 24k then there is a financial penalty and maint and we have to have to submit a report showing that we needed the performance and it wasn't just done for fun. We can use max on the 21k engines if we feel like it because of local conditions on the day without having to justify it. But we never do.

The Q400 every take off was done at 80% torque. MTOP of 100% I was told about in type rating but never did one and 3 years later and 2500 hours I stopped flying them and and had still never done one.

 

[CWB1]

Bahaha....grade-school errors strike again! Personally I have been weighed prior to boarding bush planes and helicopters many times without giving it a second thought. I'm usually more concerned with the pilot than the aircraft, just the same as I am drivers vs the condition of their car. In both cases my worst experiences have been with folks from relatively mild climates. I dont believe I have ever had a sketchy landing in arctic climates despite many landings on ice runways in high crosswinds during a snowstorm but it seems that landing in major airports in the contiguous-48, mainland Europe, and elsewhere on dry asphalt in calm air often results in the plane feeling a bit "squirrely." OTOH, the days with the most traffic accidents seem to be the best weather.

 

[Alistair_Heaton]

helicopters will kill you when they are over weight. They have so little power margin while hovering its scary especially in the R22 and R44 machines.

The colder it is the slower we are going when we land.

Some of my worst landings have been done in flat calm. When its sunny on asphalt there is a blast of lift just as you go over the runway surface from over the grass. Other airports have water at the ends and the air descends over that and then lifts over the runway.

 

[1503-44]

Rice paddies and hot asphalt road always gave a nice balloning effect just before touching down on a grass runway.

 

[Alistair_Heaton]

Oh and when its windy and gusty and/or wet we don't want to do a smooth landing and if one is done by accident its a pain in the bum.

Wet we want to get the rubber through the water so the thing doesn't start aquaplaning.

And gusty we want the lift spoilers to deploy to stop us flying and put weight onto the tyres to slow down so the gusts can't shove us sideways.

If you do a greaser in some conditions it as has been said gets squirrely.

Also most aircraft like a 5-10 knt crosswind so you can put one wheel down then the next. If you put both down together the friction of the wheels spinning up together gives a huge jump in drag and drags you down. giving a firm feeling. Some of us create a cross wind and fly out of balance just to put one wheel down at a time. Ice covered runways with low friction the drag is much reduced and its much easier to get a greaser.

 

[RedSnake]

A reason why big birds that migrate south and north ever spring and autumn often navigates and follow large motorways.

/A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[zeusfaber]

Whether a helicopter will fly under a given set of circumstances is a thing known unto only God and the helicopter.

A long time ago, on a flat calm, scorchy-hot (for that part of the world, anyway) summer's day, I was riding observer while one of our TPs put in some autorotation practice in a single-engined helicopter. After three or four uneventful attempts waved off at 1000', we beeped the governor back to ground idle and committed to a forced landing on a short mown strip in the middle of the Area.

Everything started off nicely, with a very tidily controlled 70 kn autoration, all lined up and headed neatly for the near end of the strip. At the appointed moment, the pilot flared (just like it says to) and we prepared to "settle" onto the grass. The aircraft had other ideas, and just carried on across the countryside at 70kn, buoyed up on a pad of air that kept us 10' above the ground watching more and more of the nice smooth grass disappear behind us. About 50 yards before the end of the strip, the spell broke, we sank the rest of the way and skated to the end of the strip, coming to rest with 6" of cut grass left in front of the skids and our feet hanging over the rough. The ensuing discussion really couldn't have been any shorter.

A.

 

[JohnRBaker]

I used to fly into Los Alamos, New Mexico, which sits on top of a mesa. The elevation is a bit over 7,300 ft. The commercial flights used high-wing De Havilland Twin Otters. I talked to one of the pilots once and he said it was sort of like a carrier landing as the runway went right up to the edge of the mesa. Of course, taking off you didn't have to pull-up too much to gain altitude since you were already at 7,300 feet.

John R. Baker, P.E. (ret)
EX-'Product Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

 

[dik]

A simple electronic pressure gauge would be an easy fix, unless there's something I'm missing. Maybe the 'redtape' would be an issue. The method of calculating the weight is seriously flawed.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[RedSnake]

Today, you often choose your chair in the plane yourself, at least here.
But I guess something would have to be done if the national team in sumo wrestling and the Chinese women's national gymnastics team would fly in the same plane but the sumo wrestlers sat on the right side and the women's team on the left.
Or is it just solved in a technical maner then.

Best Regards A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[Alistair_Heaton]

If its free seating they will get a brief sent through and will block rows off to keep it in trim.

Most of the time in Europe we are landing weight limited anyway.

So for say a 737-800 to be anywhere near max takeoff weight on a long runway the sector would have to be over 4.5 hours long.

 

[dik]

I thought they broke up teams just in case of an accident... didn't want the entire team to leave, unexpectedly...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[RedSnake]

Was just an example.. maybe a bad one..
When I fly from here the planes are mostly fully booked so I guess the mix of people makes the weight quite even without moving people around.
Even if all people on the paper weights "85 kg" ;-)

BR A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[waross]

There have been onboard scales available for logging trucks in the Canadian West Coast for over 50 years.
In BC, if you pull a commercial trailer over 10,000 lbs gross weight, your driver's license, vehicle registration and licensing, and insurance jump from class 2 to class 1.
Greyhound buses (class 2) used to pull small trailers to carry express packages.
The trailers all had electronic scales fitted so as to never load over 10,000 lbs gross.
Working in an oil mine, the 400 ton heavy haulers in one mine had a display on top of the cab showing the weight of the payload.
This is not new technology.
The bean counters want to know how much tar sand is being delivered to the plant.
If an on-highway logging truck is overweight, it is subject to heavy fines.(Take the pun if you like.)
If a Greyhound trailer is over-weight, it is subject to fines.
But
If a 737 is overweight, it is only a hazard to life and limb.
To weigh or not to weigh?
An easy choice for Boeing's bean counters.
Of course not.

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[Alistair_Heaton]

Its not Boeing its the airlines that don't want it.

A full load of pax doesn't weight that much to be honest. think its about 14 tons for a 737-800. With a max TO weight of 79 and landing of 66.3 they are 41 tons empty.

 

[dik]

I remember a couple of decades back there was a DC-3 crash in Oshawa, Canada because of overloading... I didn't believe you could overload a DC-3... problem ended up being the load 'shifted'... maybe still not possible to overload them.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik