Musang From United Kingdom, joined Apr 2001, 912 posts, RR: 6
Reply 1, posted (14 years 3 months 1 week 5 days ago) and read 1655 times:
On the Avro RJ 100 the fadec limits the engines to 97% N1, 98.8% N2 and EGT of 613 degrees max continuous, 632 on take off and 649 in windshear escape mode. So you could firewall the engines although there would be no point except in dire emergency.
The Thrust Control Sytem (TRP + FADEC) sets the N1 reference value based on atmos. conditions for the air bleed config. selected, we use Reduced thrust most of the time and Max when operationally necessary, but this will still be 3 or 4 % short of the FADEC limit N1. FADEC also limits the engines minimum speeds; the N2 Floor changes according to ambient conditions and the bleeds selected.
Buzz From United States of America, joined Nov 1999, 697 posts, RR: 20
Reply 2, posted (14 years 3 months 1 week 4 days 21 hours ago) and read 1643 times:
Hi Balckbird, Buzz here. Well it's possible to overboost a 757 (PW2000) or A320 (V2500) engine.... but it has to have a couple types of EEC-FADEC failure first. And people are trained not to ram the throttles (pardon me, i play with taildraggers) back and forth with abandon, so ifyou have a dying engine, it might happen, but sure is unlikely. I haven't heard of it in the lst several years at UAL.
Gt1 From United States of America, joined Feb 2001, 133 posts, RR: 0
Reply 3, posted (14 years 3 months 6 days 16 hours ago) and read 1623 times:
On the PW4000 (94") and CF6-80C2 FACEC engines, the EEC will limit the engine in the "Normal mode" for 3 parameters: N1 & N2 overspeed, and "Overboost", which is PS3 pressure. PS3 is "pressure, static, station #3", which is to say the outlet of the high pressure compressor, or if you prefer, the inlet to the combustion chamber. If memory servers, the actual pressure is in the 475-500 psi range for both engines.
In the "Alternate mode", which is "N1" for PW, and "Reversionary" for the CF6, overboost protection is lost, leaving you with only N1 & N2 overspeed protection.
Note that neither engine protects for EGT.
One last thing, I would suggest that you could say a FADEC system IS a fly-by-wire system. There are no cables between the throttles and the fuel metering component.