Switching to ALTN law

[Rocket3837]

Greeting all...
A college told me that there is a new pushbutton on the FBW aircraft (on O/H panel) which, when pressed, will downgrade control law from normal to alternate...
Was he correct?
Thanks

[Atlas Shrugged]

Yeah............it's called "The Boeing Button"

[wiggy]

Greeting all...
A college told me that there is a new pushbutton on the FBW aircraft (on O/H panel) which, when pressed, will downgrade control law from normal to alternate...
Was he correct?
Thanks

Which FBW aircraft, there are a few around?

FWIW the 777 isn’t new and it doesn’t “do”alternate law for flight controls but it has a disconnect switch on the Overhead panel. If operated it disconnects the Primary Flight Computers and puts the FBW system in a basic Direct Mode...

[Rocket3837]

I meant on Airbus FBW aircraft... Could be on NEO A320

[hikoushi]

He is probably thinking of the B/UP SPD/ALT button on the NEO series. It does not affect the flight control laws in any way; however it brings the “BUSS” backup speed scale (AKA fast / slow AOA indicator) and GPS altimeter onto the PFD without requiring to turn off multiple air data sources like previous iterations. It works independently on each PFD, and since the underlying data is still correct the autopilot will still work (though the ECAM will tell you to disconnect it).

Can switch it on and off all day with no ill effect supposedly; still haven’t had the balls to try it in the air yet!

[Airmann]

There is no such button on commercial Airbus. However Alternate Law can still be activated if you know which flight computers to turn off.

[pineteam]

Both FACs or 2 ADRs are probably the fastest and safest way to put the aircraft in alternate law. From what my chief pilot told me, in the good old days, to be instructor in my company it was mandatory to do one approach in direct law in the real aircraft and they were switching both FACs to force the aircraft to go in alternate law . Until 2 years ago, it was mandatory during the base flight to do one single engine approach, SE go around, followed by single engine landing.

[krismiler]

The military versions such as the A330 tanker can be made to come out of normal law to take evasive manoeuvres which would otherwise be prevented. Exceeding bank angle and pitch limits is of secondary importance when someone is shooting at you.

[Check Airman]

How is that functionality implemented?

[vilas]

krismiler
Are you flying the military version? Because even the military version of the A330 will have the same load factor limitations. It couldn't be an aerobatic aircraft.

[krismiler]

There is a older thread covering control laws for military versions here.
https://www.pprune.org/australia-new-zealand-pacific/313774-raaf-a330-mrtt-progress.html

Military aircraft are operated under different conditions to civilian ones and often require modifications. Allowable load factors could be increased if strengthening was carried out in required areas. Armor plating may be specified in critical places which wouldn’t be required on the civil version. Control laws would need to take into account the nature of military flying and be configured accordingly. Protections and limitations would still be required but they would be tailored to the specific role that the aircraft was designed for.

[IFLY_INDIGO]

Though I would love to have such a button on A320, but there is none on NEOs yet.

Instead of a single button, presently select any 2 ADR pbs to downgrade to alternate law.