Mastropiero From Spain, joined Dec 2005, 119 posts, RR: 0 Posted (3 years 2 months 3 weeks 2 days 5 hours ago) and read 6287 times:
Hi everyone!
I have come on many ocasions across this, without ever understanding what do you talk about when you refer to either "normal law" or "direct law". I have done some research but, alas, no useful results so far.
Would you mind explaining what do you mean when you refer to it?
I hope it is not something as simple as to make me blush with shame for not being able to figure it out myself....
WILCO737 From Greenland, joined Jun 2004, 7719 posts, RR: 84 Reply 2, posted (3 years 2 months 3 weeks 2 days 4 hours ago) and read 6264 times:
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Quoting Mastropiero (Thread starter): I have come on many ocasions across this, without ever understanding what do you talk about when you refer to either "normal law" or "direct law". I have done some research but, alas, no useful results so far.
The "normal law" is the normal way or controlling Airbus Aircrafts. like 320s or 340s. Then the airplane trims on its own and maintains the bank and pitch etc etc. With the "direct law" the Airbus flies like a boeing.
I don't know too much about it, as I am flying MDs. But I am sure the Airbus pilots will explain it to you more detailed.
Jetlagged From United Kingdom, joined Jan 2005, 2326 posts, RR: 15 Reply 4, posted (3 years 2 months 3 weeks 2 days 3 hours ago) and read 6236 times:
Normal and direct law are levels of control provided by the FBW system
Normal Law provides envelope protection (which prevents stalls, overspeed, excessive g, etc). It also provides autotrim so the aircraft stays in the attitude it was put when the control was released (within limits).
Direct Law provides no envelope protection and the sidestick moves the control surfaces in proportion to the control input. The stabilizer trim has to be moved manually by the pilot, there is no electric trim.
In between these two there is Alternate Law, which provides much reduced protection and speed stability. Pitch trim is automatic, as with Normal Law.
Degredation from Normal to Alternate or Direct Law is automatic, depending on system failures.
TristarSteve From Sweden, joined Nov 2005, 3399 posts, RR: 36 Reply 5, posted (3 years 2 months 3 weeks 2 days ago) and read 6174 times:
Quoting Jetlagged (Reply 4): Degredation from Normal to Alternate or Direct Law is automatic, depending on system failures.
In 20 years on the A320, I have only once encountered Direct Law in flight. An A320 had a double failure of an elevator posn transmitter, and went into direct law. Saw the words direct law on the PFR.
One and only time.
Tdscanuck From Canada, joined Jan 2006, 10536 posts, RR: 71 Reply 7, posted (3 years 2 months 3 weeks 1 day 21 hours ago) and read 6128 times:
Quoting WILCO737 (Reply 2): With the "direct law" the Airbus flies like a boeing.
That's not true for FBW Boeing's (i.e. the 777). A 777 has normal, secondary (equivalent to Airbus' "alternate"), and direct (same as Airbus' "direct").
PGNCS From United States of America, joined Apr 2007, 2353 posts, RR: 46 Reply 8, posted (3 years 2 months 3 weeks 1 day 20 hours ago) and read 6125 times:
Quoting WILCO737 (Reply 2): With the "direct law" the Airbus flies like a boeing.
Jetlagged From United Kingdom, joined Jan 2005, 2326 posts, RR: 15 Reply 9, posted (3 years 2 months 3 weeks 1 day 8 hours ago) and read 6071 times:
Quoting TristarSteve (Reply 5): In 20 years on the A320, I have only once encountered Direct Law in flight. An A320 had a double failure of an elevator posn transmitter, and went into direct law. Saw the words direct law on the PFR.
One and only time.
I suspect most pilots only ever see it in the simulator. My experience of trying Direct Law out in the sim is that it is pretty ugly, certainly worse than hand flying a non FBW aircraft.
The glass isn't half empty, or half full, it's twice as big as it needs to be.
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