MD11: Reason(s) for Fadec mode "alternate"?

[Guest Susan27]

Hi,could you guys tell me which situations/incidents can cause the FADEC-mode display (overhead panel lower left side) showing "Alt"...so going to the "alternate mode"...?Sometimes (more and more) I get this display after engine-startup...but not always...so I am unable to identify what makes this scenario happen...And I still dont know what I did wrong here...Thanks very much! :)

[Guest DeltaSimTek]

Hi Susan,A brief explanation of FADEC:FADEC ALT is most commonly caused by pushing the throttles past the normal forward stop, into Overboost. Not sure why you would get this on start up with throttles at idle. What is happening when FADEC goes into the ALTERNATE mode is that a primary air data parameter is not available to the EEC (Electronic Engine Control)Some of the parameters that the EEC receives are, Pressure Altitude, Total Pressure, Total Air Temp. Bleed configuration, GMT, Date, Flap/Slat position (for idle selection), Weight on nosewheel, EPR trim and autothrottleReverting to the ALTERNATE mode will never result in a decrease in thrust, but may result in an increase in thrust.FADEC has the following functions:-Engine acceleration to idle speed during start.-Acceleration and deceleration limiting.-Automatic control of available thrust.-Minimum/approach idle speeds during descents.-Compressor airflow control.-Selection of alternate modes from the cockpit.-Thrust control as a function of throttle position and reverser lever.-Protection from exceeding N1, N2, internal pressures, and maximum thrust limits.Hope this didn't bore you too much...Bryan Gandall

[KCA9304 0]

Bryan, Susan,Just one thing to add:If throttles are pushed forward through the overboost stop, this stopbar has to be reset manually to return FADEC to it's normal operating mode.And yes, it is modelled! Overboostbar has a clickspot for this.Regards,HarryEDIT: after the bar is reset, push each FADEC Mode Push button in sequence to return the system from ALT to Normal mode.

[Shmiffy 0]

Great tip! Thanks Harry:I shall try and break that on my next trip ;)CheersPaul

[Guest Susan27]

Thanks very much for your lines, guys! :) :)When I read the part concerning "overboost" & "pushing the throttles past the normal forward stop..." I had a deja-vue:If I remember correctly every time before that "Fadec-Alternate-scenario" happened I did this:On short final I disengaged AP & ATS to land the bird full manually...The result is this "annoying" (lol!) red flahing frame/box at the PFD saying "ATS off" etc...Therefore I asked what can be done to cancel this flashing red box frame:The answert was that I should press this forward reset-point at the top of the throttle levers (sorry I dont remember the correct term here), this would cancel this red flashing "ATS-off" frame at the PFD,So I followed these hint: The result was that the red-box indeed was canceled at the PFD...but as a "sideeffect" the throttle levers also were set to max. forward position (Full power!) for that very second before I could bring the thrust levers (via pressing F1 key) back to idle...This max. thrust probably is this "overboost" situation you mentioned above, right? If so...1) Is there a way to reset the red-flashing "ATS-off" frame WITHOUT resetting ATS by bringing the throttle levers to max for a short time with the sideeffects I mentioned above...?2) If not could you please describe where I exactly find this Overboost reset bar to bring FADEC-Alternate back to the "normal mode"...? I really couldnt find it although looking closely at the throttle & overhead panel...Thanks very much for your help! :)

[Guest DeltaSimTek]

Harry, yes, I forgot to mention the reset function. Susan, the first press on the Auto Throttle disconnect swticth disconnects them. A second press cancels the audible and red box warning on the PFD. Pressing the ATS Ovrd buttons on the glareshield should completely disconnect the A/P and Auto Throttle and give full authority to the pilot.Bryan Gandall

[mburkhard 23]

>Pressing the ATS Ovrd buttons on the>glareshield should completely disconnect the A/P and Auto>Throttle and give full authority to the pilot.It does but this is NOT normal procedure.Regards,Markus

[tcas_climb 45]

>Thanks very much for your lines, guys! :) :)>>When I read the part concerning "overboost" & "pushing the>throttles past the normal forward stop..." I had a deja-vue:>>If I remember correctly every time before that>"Fadec-Alternate-scenario" happened I did this:>>On short final I disengaged AP & ATS to land the bird full>manually...The result is this "annoying" (lol!) red flahing>frame/box at the PFD saying "ATS off" etc...Therefore I asked>what can be done to cancel this flashing red box frame:>>The answert was that I should press this forward reset-point>at the top of the throttle levers (sorry I dont remember the>correct term here), this would cancel this red flashing>"ATS-off" frame at the PFD,>Susan, your pressing the wrong button. What you are pressing is the Go Around Button, thats why the thrust levers advance forward. What you need to press is the same button that you used to disconnect the auto-thrust, that will remove the flashing red box

[Guest Susan27]

Hi,>>Susan, your pressing the wrong button. What you are pressing>is the Go Around Button, thats why the thrust levers advance>forward. What you need to press is the same button that you>used to disconnect the auto-thrust, that will remove the>flashing red boxwell, I think now that you are absolutely correct: This are the TOGA buttons I pressed all the time! :)1) But where can I find the needed button on the trottle/thrust levers then instead...?2)I followed your advice and pressed again the button that is assigned for disconnecting the ATS: The result was that both "ATS OVRR Off" buttons came to the up-position again (as they were before disengaging for manual landing)...But:...The red flashing box (frame) wasnt removed at all...still flashing...really strange :)3) Where do I find this "mysterious"..."Overboost Reset button" which was mentioned in the posting above...which brings FADEC ALT mode back to Normal...?

[tcas_climb 45]

Susan the AFS OVRD switches will not remove the flashing red box.As a matter of fact, under normal operations you should not even touch the AFS OVRD Switches. What you need to do is go in the PMDG menu under keyboard commands, i dont have the MD11 so i cant tell you exactly what to look for, but look for something like AP Soft Disconnect (or instinctive disconnect) and ATS Soft Disconnect (or instinctive) and assign commands to those buttons and completely forget about the AFS OVRD switch.BTW, on MD11 there is no such thing as a TOGA switch as its never used on Takeoff;-) EDIT: I dont know about resetting an overboost bar but one of two ways i know you can reset the FADEC is by switching the EEC switches from NORM to ALTN and back to NORM

[Guest Susan27]

Thanks very much again, Bryan for your kind help! :)And Yes, the problem with getting FADEC back to Norm is solved...your lines solved this problem. I ll try to work on the other problem (red flashing box cancelling)tomorrow... Have a nice sunday! :)KRSusan

[tcas_climb 45]

:-wave

[mburkhard 23]

>BTW, on MD11 there is no such thing as a TOGA switch as its>never used on Takeoff;-) You're incorrect here. You MIGHT use this button on take-off: If you depart with derated thrust should you for any reason require more thrust than what you have set with the derate, pressing the GA switch will cancel derate and go to full TO thrust.Markus

[tcas_climb 45]

well yea sure but its not really a "conventional" TOGA is what i meant