Just read out what FADEC stands for :
FULL AUTHORITY DIGITAL ENGINE CONTROL

Doesn't matter if it has a manual reversion mode or not, when it is operating it has full authority over what is going on. The extra definition of "not having manual reversion" is somebody's idea of what it perhaps SHOULD be.

From various technical sources:

WHAT IS FADEC?
To be a true, 100%, Full Authority Digital Engine Control, there must not be any form of manual override available. This literally places full authority to the operating parameters of the engine in the hands of the computer. If a total FADEC failure occurs, the engine fails. If the engine is controlled digitally and electronically but allows for manual override, it is considered solely an Electronic Engine Control (EEC) or Electronic Control Unit (ECU). An EEC, though a component of a FADEC, is not by itself FADEC.

FADEC : LIMITATIONS
Pilot cannot override the FADEC Control. In the event of complete FADEC Failure pilot left with no other option than having to land safely with least performance.

With modern FADEC systems there are no mechanical control rods or mechanical reversions,

Still the system is not void of disadvantages. During critical conditions the system does not provide with manual override.

:ooh:

Absolutely agree HLCPTR - the introduction of FADEC to the Chinook resulted in some uncontrollable runaways that trashed the engine.. It's all very well handing full control to the computer but the software needs to be bug-free.

Sevarg - the Wessex had a fuel computer but that would just freeze in the event of a loss of signal - it could be recovered by resetting the speed select lever. The same computer and engine (Gnome) were used on the Sea King but that had a manual reversion (throttles in the roof). The Whirlwind - I think - had the same computer and that had a manual reversion as well. Definitely not FADEC.

My (tongue in cheek) definition of PADEC was not related to computer malfunctions but to the occasional pilot "malfunction" in mishandling the manual back-up and exceeding an engine limitation in the process.

FADEC never gave me that opportunity. ;)

yes, double manual in the Sea King provided plenty of opportunities for that:ok:

crab,
The Wessex 2,4,5 and 60 all had a full authority analogue computer, with a double-datum over speed protection, which as you say froze not infrequently but could be reset. I think it was the same computer on the Whirlwind but when I was flying them in Nigeria we had so many computer problems we just flew them in manual the whole time. It took a little getting used to initially as, of course, there was no throttle correlator.

How time flies.....

In those days, those contraptions were "computers". Today's techies would probably not recognize them as such. :8

Today's systems are a whole new story.

The RTM322 as installed in the Merlin Mk1 onwards (c. 1994), WAH64, EH101-512 & -518 is controlled by dual channel FADEC with no manual reversion.

The CTS800N in Super Lynx & AW159 is also has dual channel FADEC with no manual reversion as does the GE CT7-8E in the AW101.

Soggy - yes, apart from the loss of Ng, NF or PTIT signals causing freezes, the cheekiest was low voltage which ISTR froze the computer below 18V but locked the throttle actuator - however, with voltages below about 12V, the throttle could vibrate open or closed.

We had several double computer freezes in the 80s caused by generator issues - which were quite exciting for the crews involved!

FADEC...e for engine, or electronic?

E for Engine - don't trust wiki implicitly, a google search throws up plenty of websites of companies that make them.

Not Wiki Crab, my current Bell RFM has both E for engine and E for electronic in different sections!

Well it's unlikely to be Electronic. You can't have Digital without electronics, so that is a bit like talking about a personal Identification PIN Number.

And a FADEC sure as heck doesn't control the electronics in my 76B, it controls the ENGINE.

SilsoeSid,

What do you call it then?

The Turbomeca Arriel 2B1 in the AS350B3-2B1(B3+) and EC130B4 has dual channel FADEC and EBCAU (Electronic Backup Control Ancillary Unit) Same with the Arriel 2D in the later model AS350B3e/H125 and the EC130T2/H130

In these helicopters you have no input whatsoever on engine governing, only selecting Flight or Ground Idle after start.

HLCPTER,

I think not. (in the models above at least)

In case of full FADEC failure (dual channel) the EBCAU takes control automatically, keeping NF within preset value and you'll land as soon as practicable.

So that would imply there is a 3rd channel of FADEC, if the EBCAU is able to control the throttle valve electronically when both lanes of FADEC have failed then it seems to be a triplex rather than duplex system.

I presume the throttle response in EBCAU mode is significantly damped to encourage smooth collective inputs and avoid rapid Nf changes.

I think other systems would just freeze the throttle valve in the event of a double channel FADEC failure.

EC225 has only switches to play with.

And with the AS350B3e and EC130T2 the FADEC controls all. If you try to select ground idle in flight with the collective still 'up' it wont let you, it carries on (after a short blip) in flight mode. You then can not re-select ground idle, you have to shut the engine down in flight idle to reset it. You can only go to idle with the collective (almost) down first.

When on course on a full FADEC helicopter I asked if the dual FADECs were protected from EMP (Electro Magnetic Pulse) by some sort of Faraday Cage or other system.
Instructor did not know but thought it was a valid question and called the manufacturer to find out.
Answer: NO!

For all UK Mil aircraft there are HIRTA (High Intensity Radio Transmission Area) avoidances for the different bands of RF TX - each Release to Service will detail how susceptible the aircraft systems are to various signal strengths in those bands and mil maps are marked with the HIRTA avoids.

There are plenty of places in UK where you can't fly a mil helo due to the HIRTA restrictions but civilian helicopters can just blat through them.

It is systems like FADEC, AFCS and weapons (or even a hoist with an electrically operated cable cutter) that are susceptible.

All modern transport category rotorcraft certified under Part 29 are tested against stringent HIRF (High Intensity Radiated Field) criteria. Electrical harnesses are terminated in very specific ways to help reject rf induced interference. FADEC and other critical systems have detailed loom routing and separation requirements. The problems of HIRF are well understood and catered for, whether this includes the field strength/density generated during an EMP event I could not say.