FADEC, but no autothrottle?

[TotalBeginner]

I'm trying to get my head around some of the autoflight systems of the citation-x.

Is it true that, despite the engines being controlled by a FADEC, there is no autothrottle. There are selectable detents, similar to Airbus where you can select TO - CLB - CRZ and the FADEC will control power, but no autothrottle? This seems very strange?

[Maude Charlee]

Not unusual at all. All FADEC does is prevent a ham-fisted clot like me placing demands upon the powerplant that take it outside safe operating limits. All autothrottle does is allow you to eat and drink at the same time, instead of keping one hand free for the power levers.

[Hufty]

The Embraer 135/145 has FADECS but no autothrottles. Not sure about the rest of the Embraer family though.

[Speedbird48]

You should remember that FADEC comes in many flavors, but with the same name.

You appear to be talking Airbus, but there is a Mooney with FADEC, and the Diamond DA-42 TwinStar has full FADEC. Neither of them have autothrottle but the FADEC controls engine functions to give you the power you ask for, within the controlling limits. No messing with mixture when it is "hot & high" for instance.

FADEC can do as little as control bleed valves to prevent you exceeding your engine EPR limitations, or it can control everything. relating to
temperatures ,fuel flow, EPR settings etc.

I am sure you will get better explanations but that is it basically.

Speedbird 48.

[Mad (Flt) Scientist]

As mentioned a FADEC and an AT are distinct beasts. All a FADEC does is (as the "EC" parts says) provide "Engine Control".

Basically, there are systems-levels controls, and there are aircraft-level controls.

Aircraft-level can be a pilot, or an autopilot and/or an autothrottle
System level can be a FADEC or hydro/mech control (for engines), or FBW or cable/lever for flight controls.

The relationship between FADEC and AT is exactly the same as between a FBW system and the AP. The FADEC controls the "inner loop" around the engine itself, while the AT controls the "outer loop" which includes engine/aircraft interaction. In a FBW/AP system, the FBW controls the actual aircraft dynamics, while the AP takes care of the bigger picture. In both cases the AP/AT can be replaced by a pilot doing the same task of a top level system/aircraft controller.

It's also possible to have an AT and no FADEC, just as you can have an AP and no FBW - the AP or AT just provides mechanical commands which mimic what a pilot would do.

Having everything electronic can make the integration easier but its not a necessity.

[Beeline]

Autothrottle or autothrust, no resolver movement on FADEC throttle levers? Instuctor asked me what letter came after a/thr I said 'o' he said 'u'?? :confused:

[Whispering Giant]

EMB 170-195's all have autothrottle whereas the the EMB135-145 do not have autothrottle's.
Also the Dash8 Q400 has FADEC engine control but has no Autothrottle's.

brgds
W.G

[potkettleblack]

Autothrottle or autothrust, no resolver movement on FADEC throttle levers? Instuctor asked me what letter came after a/thr I said 'o' he said 'u'??

Depends which way you swing:) Boeing would say throttle. Airbus say thrust.

[ahramin]

A large portion of the first 50 Citation Xs were destined for NetJets. Cessna was going to delay the delivery because the autothrottle system was giving them problems. NetJets didn't care enough for autothrottles to delay delivery.

This is why early Citation Xs do not have autothrottles.