Transition to C172 Diesel (FADEC)

[FlyingStone]

Having flown couple of hours in O-320 powered C172, I will begin flying Thielert powered one soon and I have some "stupid" questions:

Since the engine is turbocharged, is it important to have very smooth throttle operation (as in conventional turbocharged engine) or you can "slam" the throttle from idle to full and vice versa while FADEC controls the rate of acceleration? I was thinking of doing 10 seconds acceleration from idle to takeoff power instead of normal 3-5.
On the ground is the throttle lever in idle position or do you set it to provide higher-than-idle RPM in order to increase quality of combustion (and decrease carbon deposits)?
Are there any statistics of single or dual FADEC failure in flight regarding Thielert engines?
The manual (supplement) doesn't state the type of constant speed propeller - is it controlled electrically or hydraulically?
Regarding the electrical supply to the FADEC: if I understand correctly, if the engine is running and the BAT and ALT switches are switched to off and therefore no electric power is provided by battery or alternator, the engine stops working?
Although the aircraft is operated with Jet A-1 only, I have to ask: does fuel consumption/performance differ from Jet A-1's when using Diesel fuel?Every answer as well as any advice will be highly appreciated.

[englishal]

Never flown a 172 but in general (after flying DA42)....

You can slam the throttle open and closed, FADEC takes care of everything
Idle on the ground, or power as required to taxi
Before shutting down you should let it idle for a couple of minutes to allow the turbo to cool.

Do you have a BAT / ALT switch anymore or simply and "Engine Master" switch? The DA42 has an engine master for each engine, and yes if this is turned off the engine stops and the propellor feathers. In fact in the event of engine failure, you just switch the master off and that is it.

FADEC is so easy. You set power using the throttle, for example 75% power and the FADEC sets engine and prop for you. Turbo is nice too as power remains in the climb. I believe that the DA42 runs at about 80 inches of manifold pressure.....

[BillieBob]

These questions should all be covered during the SLPC differences training that you are required to receive.

[BackPacker]

Agree. FADEC is great, as long as it works. You can open and close the throttle at whim, don't have to worry about overboosting/overrevving, shock cooling, carbon deposits at idle, carb ice, leaning, whatever. Just set the %power and off you go.

I had never flown anything other than a fixed pitch prop before, and the only thing I really had to get used to was the fact that engine noise (pitch) is no longer related to the amount of power the engine is generating. You really need to look at the engine displays to know what's going on. If you've flown C/S props before this is probably not an issue, though.

BUT... What is really important to learn is the completely different failure modes a FADEC has, and what you can do about it. The Thielert has dual FADECs and you need to know how to test them, and how to switch from one to the other if that doesn't happen automatically. Also you need to know how exactly the dependency on the electric system works. Which buses are relevant, how to feed these from the (multiple!) batteries you have, and how long you can fly on battery power alone before the engine quits.

Oh, and there are no performance differences between Diesel and Jet-A. But with Diesel fuel the temperature limits for starting and take-off are a little tighter than with Jet-A. However that's only relevant at temperatures lower than -15C or so. In the DA-40 that I flew, certification for Diesel came later than the base certification for Jet-A. So there was a POH supplement for running on Diesel. If you grabbed a POH off the internet, you might be missing that supplement.

[englishal]

Actually I forgot one major difference. There is no run up required.

You simply hold the TEST buttons in and it runs through an automated check routine which switches FADECs, cycles the prop etc....This is quite useful if you have a longish taxi, on the taxiway, simply hold the TEST button in until the checks have completed (15 seconds?), manually swap FADECs (Switch to B) to check that works, switch back and that is it, you are good to go (after doing pre-take off checks of course).

[Katamarino]

A cautionary point about those advocating "slamming the throttle open"; having done my checkout on our club DA40 yesterday, the instructor cautioned against opening the throttle too fast because the constant speed prop governer reacts a little slower than the engine does, and you can inadvertantly overspeed the propellor. He said that the usual smooth 3-second advance should be fine.

[Halfbaked_Boy]

Although the aircraft is operated with Jet A-1 only, I have to ask: does fuel consumption/performance differ from Jet A-1's when using Diesel fuel?

Nope.

You can run 'em (and they are rated for) on Jet A1, diesel from the forecourt, and also red/green diesel.

[IO540]

Do any airfields sell car diesel?

[FlyingStone]

Thanks for all the answers, I really appreciate it.

These questions should all be covered during the SLPC differences training that you are required to receive.

No worries, I will be getting proper differences training, I just wanted to discuss some questions here in order to better prepare for it.

Do any airfields sell car diesel?

Not that I know of...

[BackPacker]

I was at an airfield that sold Avgas 100LL, Mogas and Jet-A. Although clearly airside, the Mogas pump specifically specified "not for aviation use".:=

Anyway, I don't think all Thielert/Centurion engine installations are approved for diesel fuel (it was a supplement to the DA40 POH after all), and from what I recall from reading the Flyer article about this, other engines (SMA?) may not be approved for car diesel ever.

Having said that, car diesel is cheaper than Jet-A, at least over here (1.09-ish vs. 1.50-ish) so if there was a choice, I'd run on diesel.

[FlyingStone]

I doubt diesel fuel is the future of general aviation - diesel engines yes, diesel fuel no...

I recall from somewhere that 99.5% of all sold aviation fuel is kerosine (of which Jet A-1 is probably the most common) and since most aircraft takeoff from airfields and not roads I don't see practical use of diesel. Also, why would you need to have two type of fuel trucks, if all (diesel and turbine) engines use same type of fuel (Jet A-1)?

Also, diesel fuel has very obvious problems with low temperatures (in C172 POH supplement it says that fuel temperature before takeoff has to be above 0°C and in flight above or equal -5°C). That would make aircraft pretty useless in those nice sunny winter days with temperatures around -15°C and unlimited visibility.

And over here, benefit doesn't justify of selling diesel fuel at airports - diesel fuel is almost 1.20€ and Jet A-1 1.30€ (tax inc.).