Overweight Landings

[Zinger]

Just went through the PIPS manual and got the impression that the above subject is viewed to likely damage the landing gear attachemnt points, engine mounts etc...

Aircraft structural design is planned for 4G vertical stress. Under normal circumstances, a soft landing will unlikely transmit past the oleo struts much more than 1.1G vertical acceleration.

An important, although mentioned point should be stressed- braking. The system isn't designed to absorb the aircraft kinetic energy existent at that weight regime, and will likely exhibit both reduced performance and brake fire.
My first cockpit landing in a B747-258 as observer was at Kennedy runway 22 in 1974, with capt.  Abarbanel. The FE was reading  guess what? brake temperature- it rose to near limit faster than he could speak, with minimum fuel.

[OKD]

I bet you were sweating as you were listening to the temperature callout...I would, if I were you....haha....

Do you remember the autobrake setting, if they were using one, or the captain was using manual toe brakes?

[Zinger]

No idea.

[Hardy Heinlin]

Did they have autobrakes at all in 1974?

[OKD]

I would imagine so coz I watched one of the classic on youtube, where they already have FMS departing from Cairns to San Francisco, not that I have solid evidence. Need someone who has experience to tell us?

[Zinger]

Not sure about incorporation dates, but the model B747-200 series had them, according to the following RFP manual exerpt:
"Autobrakes
Autobrakes are part of the normal brake system. Pressure is applied evenly to all sixteen brakes through a single electrically controlled metering valve. The normal antiskid system provides skid protection.
Three deceleration levels are available:
• MIN (minimum): 4 feet per second
• MED (medium): 6 feet per second
• MAX (maximum): 3000 psi is applied to the brakes."

Comment: Deceleration should be expressed in unit distance per unit time squared.

[John H Watson]

It was quite sophisticated for its time, but the 747-200/300 Autobrake System used only wheel speed to compute deceleration. There was no INS input.

[OKD]

Zinger

Just going back to your original note which your experience was back in the mid 70s, and your subsequent notes about the manual.  I just wonder if the manual was for original model, or for "mid-term mid 80s" upgrading models, where the classic somehow were to be upgraded to a more sophisticated equipment?

As JHW pointed out, autobrakes seemed quite sophisticated for the classics back in those days?  But for the 300s, they were rolled out in 85, so I think they had the technical know hows to make one back then.

[Zinger]

Annyeonghaseyo OKD,
again, not sure about dates, searched images but came up with nothing.

[Phil Bunch]

I was surprised to read that the A380 only has thrust reversers on the two inboard engines, and they even thought seriously about not installing any thrust reversers.  

How do they get away with only using brakes for such a heavy airliner?  Part of the story may be the presence of more wheels than the 747.  I understand that part of the reason for not having thrust reversers on the outboard engines is that they are off to the side near or perhaps over the earth rather than the pavement.

It's interesting that some of the latest airliners are doing away with bleed air and using more electricity to accomplish various tasks previously done by pneumatics or hydraulics.

Here's an excerpt from the wikipedia article:

The A380 was initially planned without thrust reversers, as Airbus designed the aircraft with ample braking capacity to not require their use.[134] However Airbus elected to fit the two inboard engines with thrust reversers in a late stage of development.[103][135] The two outboard engines do not have reversers, reducing the amount of debris stirred up during landing. The A380 features electrically actuated thrust reversers, giving them better reliability than their pneumatic or hydraulic equivalents, in addition to saving weight.[136]

http://en.wikipedia.org/wiki/Airbus_380

[farrokh747]

on the subject of autobrakes, will the solenoid latch (28vdc) in the AB switch be modeled in psx? ie, will it have a variable for control?

Cheers,

[Richard McDonald Woods]

Somebody reading PIPS, eh?

[Hardy Heinlin]

on the subject of autobrakes, will the solenoid latch (28vdc) in the AB switch be modeled in psx? ie, will it have a variable for control?

Sure, it's automatic in PS. In PSX there's a network variable for the selector position. If you inject a value going against the automatics, it will snap back in PSX a fraction of a second later and eject that new internal value to the external addon.

For your real 744 selector with its stopper tooth between OFF and DISARM, it should be pretty straightforward; 1 - MAX positions snap back to DISARM, and RTO snaps up to OFF. Just let it snap. The only problem might be if you load a situation with RTO set while your hardware is right of DISARM; if PSX then snaps from RTO to OFF, your hardware perhaps cannot jump anti-clockwise via DISARM over the stopper tooth to OFF. But that's just a matter of situation loading and the correct manual panel preparation for that loaded situation.


Cheers,

|-|ardy

[farrokh747]

thanks hardy, wiring for future switch and psx....  will remember to load saved situations with correct switch prep....

and on we go... learning new things each day.

cheers

fc