Topic Author
Posts: 3384
Joined: Wed Oct 06, 1999 10:48 am

Fadec Limit?

Sun May 20, 2001 3:27 pm

Can a pilot using a plane with FADEC firewall the engines, or overboost them in any way? Or is it like Fly-By-Wire, where it restrains any excessive setting?

Or is it like Airbus and Boeing where it depends on company?

Posts: 788
Joined: Sun Apr 08, 2001 4:11 am

RE: Fadec Limit?

Sun May 20, 2001 9:28 pm

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.

Regards - Musang
Posts: 694
Joined: Sun Nov 21, 1999 11:44 pm

RE: Fadec Limit?

Mon May 21, 2001 12:39 am

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.
Posts: 124
Joined: Wed Feb 21, 2001 10:30 am

RE: Fadec Limit?

Sat May 26, 2001 5:44 am

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.
A/c train
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Joined: Sun Jun 10, 2001 7:57 am


Sun May 27, 2001 9:46 am

Were about's in East Sussex are you from Musang?

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