Tristarsteve
Posts: 3364
Joined: Tue Nov 22, 2005 11:04 pm

Fadec/EEC MEL Availability

Sat Apr 07, 2007 9:54 pm

I work on B757 and B767 with RB211 engines, and B777 with Trents and A319/320 with V2500 engines.
Over the years I have had many EEC faults on the RR engines and The MEL has always let me dispatch the aircraft. On B757 both EEC may be inop, and on B767 and B777 normal mode may be inop and C1 faults are allowable.
But on the V2500 both channels of both FADECs must be serviceable. There are a couple of messages that are dispatchable, but last week I was trapped and was AOG for an EEC which had a fault on one channel.
Question is, why are the RR engines allowed to fly with faults, whilst the IAE engine cannot?
I can understand the B757. The EEC is only a limit controller over a mechanical FCU.
But the B767 RB211 is fully electronic and the B777 is a real FADEC.
Any one out there who can shed some light on this.
Steve
 
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zeke
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Joined: Thu Dec 14, 2006 1:42 pm

RE: Fadec/EEC MEL Availability

Sat Apr 07, 2007 11:27 pm

My guess would be on the V2500 on the 320, without the EEC you loose the data bus between the EIU, you would not be able to start, no autothrust, no reverse, approach idle, no bleed corrections, ignition on all the time etc. If you had both the EECs fail in flight, it would be seen by the FWC and FMGC as a double engine failure.
We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
 
movingtin
Posts: 87
Joined: Sat Oct 21, 2006 1:03 am

RE: Fadec/EEC MEL Availability

Sun Apr 08, 2007 2:18 am

Quoting Zeke (Reply 1):
If you had both the EECs fail in flight, it would be seen by the FWC and FMGC as a double engine failure.


If the EEC fails in flight, the motor should'nt shut down, it will go to a preset fuel position slightly above FLT idle.

I am curious to know if the V2500 restriction is a master MEL restriction or the airlines restriction? on the 737NGs we fly, the EEC NML light "on" is MEL able with the EEC in ALTN. The PW2037, 1 channel (PRI or SEC) can be MELed.
 
Goldenshield
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RE: Fadec/EEC MEL Availability

Sun Apr 08, 2007 2:30 am

Quoting Movingtin (Reply 2):
If the EEC fails in flight, the motor should'nt shut down, it will go to a preset fuel position slightly above FLT idle.

While only turboprops, the engines on the aircraft I dispatch that have EEC's do just that, but you also lose a host of other abilities, too, like reverse pitch if the EEC is lost.
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zeke
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Joined: Thu Dec 14, 2006 1:42 pm

RE: Fadec/EEC MEL Availability

Sun Apr 08, 2007 5:34 am

Quoting Movingtin (Reply 2):

If the EEC fails in flight, the motor should'nt shut down, it will go to a preset fuel position slightly above FLT idle.

Not saying the engine will shut down, just that aircraft will see it as a double engine failure as the databus is unavailabe.

Quoting Movingtin (Reply 2):
n the 737NGs we fly, the EEC NML light "on" is MEL able with the EEC in ALTN.

Thats a CFM56, which uses N1. The V2500 uses EPR and reverts back to either a N1 rated or unrated mode depending on the failure.
We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
 
movingtin
Posts: 87
Joined: Sat Oct 21, 2006 1:03 am

RE: Fadec/EEC MEL Availability

Sun Apr 08, 2007 7:01 pm

Quoting Zeke (Reply 4):
Not saying the engine will shut down, just that aircraft will see it as a double engine failure as the databus is unavailabe.

The A/C will see it as an ENG that it cant control, not as a Double eng failure. Failure means a whole lot more than not being able to control max EPR or N1, loss of TMS, etc. The 757/767 speed card gets its speed signal directly from the speed sensor, not the EEC. that way the critical A/C systems are only affected with a TRUE Eng failure. The 737NG is similar, DEU reads signal from EECs, no signal, it uses the analog signal directly from the speed sensor.

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