Weight and Balance…

[3WE]

Has this happened with SELF LOADING freight before…at least recently…with a real airliner?

We need to fire some Boeing executives!

A641E815-A4B1-4413-9B1C-32EA90EC489B.png (1.32 MiB) Viewed 4112 times

[Gabriel]

http://avherald.com/h?article=4bb39191&opt=234

[3WE]

I was referring to over-rotation during passenger unloading (or loading), totally due to weight.

Not_over-rotation during takeoff with elevator input being a significant factor.

Also, is this another failure mode of MCAS?

[Gabriel]

I was referring to over-rotation during passenger unloading (or loading), totally due to weight.

Not_over-rotation during takeoff with elevator input being a significant factor.

Me too. This had ZERO to do with any elevator input and EVERYTHING to do with self-loading cargo deciding to all seat in the back of the plane.
The plane tilted up and struck the tail at extremely slow speed as soon as the pilot advanced the throttles for take-off. They were lucky that they had to abort the take off due to the tail strike, otherwise they would have taken off WAAAAAYYYY out of CG limits.

[elaw]

I wonder if this happened in a red zone? My understanding is there is no loading or unloading in a red zone.

Joking aside, it looks to me like this was the result of unloading the front cargo compartment before unloading the rear or the pax. If the plane actually *landed* with that imbalance, that's scary.

[elaw]

Well apparently this matter has been settled: https://thepointsguy.com/news/united-fl ... D=ref_fark

The airplane had a balance problem. Who knew!

[3WE]

Well apparently this matter has been settled: https://thepointsguy.com/news/united-fl ... D=ref_fark

The airplane had a balance problem. Who knew!

I thought it was due to the pilots pulling the CB on MCAS?

[3WE]

Being serious for a moment: if this is ‘totally due to passenger unloading’, it would seem that EVERY unloading ought to get close as front seats empty while folks wait in the back…

Especially in the instance of the ever-present goof head who has to block the aisle for two minutes to grab his stuff…the whole line ahead of him deplanes and there goes all the counter weight.

Do they make a point of unloading rear cargo first to prevent this?

Note: I am aware of “stands” to prop up tails, but don’t ever see them on the passenger ramp.

[Not_Karl]

Especially in the instance of the ever-present goof head who has to block the aisle for two minutes to grab his stuff…the whole line ahead of him deplanes and there goes all the counter weight.

We should have a Brianie on every flight to stomp over those passengers.

[3WE]

Especially in the instance of the ever-present goof head who has to block the aisle for two minutes to grab his stuff…the whole line ahead of him deplanes and there goes all the counter weight.

We should have a Brianie on every flight to stomp over those passengers.

I was GOING to say that he only did that for emergency evacuations…then again, the need to get to a REAL lavatory may indeed be an emergency.

[Gabriel]

Being serious for a moment: if this is ‘totally due to passenger unloading’, it would seem that EVERY unloading ought to get close as front seats empty while folks wait in the back…

Especially in the instance of the ever-present goof head who has to block the aisle for two minutes to grab his stuff…the whole line ahead of him deplanes and there goes all the counter weight.

Do they make a point of unloading rear cargo first to prevent this?

I don't know, but given the fact that airplanes don't do this often, I would assume that there are margins in the design to avoid this to happen from pax only. Unloading the rear cargo first and loading it last, on the other hand, makes a lot of sense, I think it is a standard practice (not sure though) and these kind of incidents have happened in the past when loading heavy items in the rear cargo first.

In the Flybondy incident that I linked, passengers were sitting all in the back (because the fare was cheaper) and that was not taking into account when doing the weight-and-balance, and the CG was well aft of the aft limit, yet the plane did not rotate until the pilot advanced the throttles for take-off which added a thrust force below the CG (which implies a thrust pitch-up moment).

[3WE]

***the Flybondy incident***

If there had been a good “quartering headwind/crosswind”, blowing over nose-down crosswind inputs and gentler power advancement, the plane could have conceivably kept the nose on the ground (with the pilots unaware of the CG)…???

[3WE]

I was referring to over-rotation during passenger unloading (or loading), totally due to weight.

Not_over-rotation during takeoff with elevator input being a significant factor.

Me too. This had ZERO to do with any elevator input***

I reread the link- I don’t know how many damn paragraphs I had to read to get any hint that thrust from underslung engines tipped it up…

And even after 8 or so paragraphs, I’m still not sure that it clearly and explicitly says that…it only kind of hints at it.

What is so hard abort putting the bottom line in the top paragraph (ironing and humor noted, but also serious).

[Gabriel]

Towards the beginning of the article:

Aviation sources in Argentina are considering a mass and balance problem

In the middle (interim report)

The dispatcher computed and provided a load sheet, that the captain accepted, indicating the CG was at 22.2% MAC requiring 3.4 trim units nose up. Takeoff weight and CG were within permitted limits. However, the actual passenger distribution throughout the cabin did not match the dispatcher's documents, almost all the passengers took their seats in the aft cabin, which moved the CG to about 38% MAC outside of the permitted takeoff limitations. A Boeing simulation based on the FDR data estimated the CG near 40% MAC.

Some cherry-picked sentences / paragraphs towards the middle and bottom (final report)

the Center of Gravity was between 38 and 40% MAC outside the permitted envelope, the actual distribution of passengers on board did not match the distribution used in the dispatch forms. As result the aircraft experienced a sudden pitch up causing the contact of the rear fuselage with the runway surface (tail strike)

No visual monitoring of passenger distribution was done though required by Flybondi's Operations Manual

there were 65 passengers on board of the aircraft, 60 of them were seated aft of seat row 15. In additional 450kg of cargo was loaded in the aft cargo hold.

The loadsheet had computed a takeoff mass of 55,633 kg and had computed the CG at 22.2% MAC, however, the JST found the actual CG was between 38 and 40% MAC. The limit of the CG was at 26% MAC however.

When the engines were accelerated for takeoff the aircraft was accelerating through 5 knots over ground and the engines accelerating through 75% N1 the aircraft began to pitch up as result of the pitch up moments produced by the engine thrust until the aircraft's tail contacted the runway surface.

The seat assignments of passengers was done according to sales specifications. The seats in the aft cabin were generally cheaper than those in the forward cabin and were therefore the first to be sold.

After completing the passenger registration the operator using their computer system informed dispatch about the assigned seats on the aircraft and the billed amount of luggage. This information was transmitted through a series of photos taken from the computer screen and transmitted by mobile phone, a procedure which was not established in the operations manual by Flybondi. The manual stated the dispatcher must be informed, however does not specify how this information is to be transferred.

Based on the information received from the operator the dispatcher created the load sheet on his computer system, which computed the CG to be within the permitted envelope for takeoff though actually it was way outside the envelope.

Picture in the article:

[3WE]

Quote=Gabriel
[Six paragraphs of Blah, Blah, Blah]

Paragraph 7 (Paraphrased) The plane pitched on to its tail as the thrust hit 75%.

Why so hard to get to what happened?

https://youtu.be/MabLtuTpDw8

[elaw]

The seat assignments of passengers was done according to sales specifications.

Well I think that pretty much says it all.

[Gabriel]

Quote=Gabriel
[Six paragraphs of Blah, Blah, Blah]

Paragraph 7 (Paraphrased) The plane pitched on to its tail as the thrust hit 75%.

Why so hard to get to what happened?

https://youtu.be/MabLtuTpDw8

The way The Aviation Herald works, they report the incident / accident as soon as Simon becomes aware of it, and then adds new information as available. The interim and final report were not available at the time of the initial news story. By the time he updated the interim report, the final report was not available. Could he go and modify the information in the top as new information becomes available. Yes, and he does that from time to time, when the new information renders the previous one incorrect, not incomplete.

But I am sure that Simon will be interested in your opinion about how his editorial skills and preferences are not compatible with your desire of being spoiled at the beginning of the story about how the story ends (a desire I share, by the way).