bjornhall

But an electrically controlled engine does not need to fail just because you have a complete electrical failure.

Do what you do on the larger aircraft: Fit dual FADECs/ECUs/equivalent to each engine, powered by their own permanent magnet alternators (PMA). The aircraft's electrical system provides FADEC power for engine start, ground tests and backup only.

In normal operation the FADECs are isolated from the aircraft electrical system, and thus unaffected by any transients or outages. Only if you have a PMA failure or if the engine is stopped is there a link between FADEC and ship's power.

Have a single FADEC failure: Engines keep running.
Single or dual PMA failure: Engines keep running.
Complete electrical failure (PMAs operating): Engines keep running
Two or even three FADECs fail, and dual PMA failure: At least one engine still running.

You'd need four FADEC failures, or failure of both PMAs and ship's power, to have a dual engine failure.

A diesel single could still have dual FADEC, powered by a PMA and isolated from the aircraft's electrical system, for increased safety.

IMHO, the reliability problem with modern diesels is not that an electronically controlled engine is inherently unsafe, but that they have not bothered making it as safe as it should be. Of course, that is due to cost.

soay

I'm not familiar with permanent magnet alternators, except that they seem to be popular for wind power generation - for obvious reasons. Do they have issues with size and/or weight, compared with field-wound alternators?

Life's a Beech

Mister Jellybean

The time the battery is likely to last! I'm not talking about what the POH says, but the experience in use, which is around 30 minutes.

vee-tail-1

Oh my god! Lets see if I have got this. Because of the decision to fit an electronic injection diesel, rather than a mechanical one we will need:
Two alternators per engine (one for the aircraft electrics, and a PMG alt for the FADEC) and that means two separate alternator drives (gears or belts)
Two FADECs per engine and the associated wiring to interconnect with the aircraft system and the other engine.
That is a serious amount of extra kit which is going to have a weight penalty, OK for twin jets, but we are talking GA aeroplanes here.
Perhaps there is some kind of buzz in flying a little aeroplane with all that electronic stuff, but is it reliable? It seems like the difference between the latest Audi TD which can only be serviced by experts, and a Peugeot 205 which is totally reliable and easy to fix by it's owner.

IO540

What I don't get is why Diamond/Thielert did not fit a small alternator on the back of each engine, to power the ignition/FADEC box?

For example, you can get little alternators which go in place of a standard vac pump, and these are certified for vac pump replacement - you use an electric horizon. And you end up with a far more reliable horizon system than the old vac pump setup.

bjornhall

Yes, I believe that is their drawback... Less of a problem for a very small unit that is only required to power the engine electronics; not avionics, lighting, starters etc.

Is it all really needed...? *shrugs* I don't know. But unless you want an electrical failure to stop your engine(s), that's what you have to do. On FAR 25 aircraft they consider it a necessity...

englishal

Really though, in a DA42 you must have BOTH alternators fail to be running on reserve....It has 4 ECUs, so all 4 must fail to lose both engines, if 3 fail, you still have one engine. Or you need to have a double ECU failure on one side followed by an alternator failure on the other side....hmmm......It'd not be your day if that happened!

I'll take my chances with it........

scooter boy

"You'd be more likely to survive a crash in a TS than a Mooney, the TS has been designed with a 25G safety cell and seats for a start...."

I doubt this - the Mooney has a built in tubular steel NASCAR style roll cage - the only evidence of this that you can see as an external onlooker is the central bar down the windscreen. Also airbags are now standard, does the Diamond or Cirrus come with these?

"On the subject of the TKS, I thought that actually increased the top speed of the TS due to the differences in leading edge of the wing with and without."

No that would be Diamond lying to you again! You lose 5-10kts in cruise with a TKS equiped Twinstar just as you do with a TKS equiped Mooney. I was amazed by the cost of retrofitting a TKS system to a Twinstar when it was quoted to me by a friend. Much cheaper I hope if it is put on at the factory but I bet it is still a more expensive option than for the Mooney. According to Mooney the TKS speed loss is due to the extra prop boots/grooves/slinger ring rather than any loss of laminar flow due to the titanium leading edge panels.

The modern Mooney is slipperier than any Diamond, Cirrus or Columbia and independent reviews back this up. Another example of the efficiency of this magnificent airframe is the massive range achieveable with a long-body Mooney. Just make sure you pack your pee-pot and you can cross continents and oceans in a single hop, at max economy with Monroy long range tanks (also standard in new Mooneys) your range is closer to 2000nm than 1000nm.

IMHO the diesel engine is not yet ready for aviation use and equally 2 engines are not necessarily safer than one. My friend has a twinstar and lost an engine in IMC shortly after he took delivery due to one of the ECUs shutting it down in flight. He could not override this feature but fortunately made a safe landing on one engine on the ILS through a low overcast.

Maybe in a few years Diamond/Cirrus will have a fraction of the experience with the airframe/engine combination that Mooney has.

Would I buy a Cirrus, Columbia or Twinstar while Mooney are still in business, absolutely not! I am swayed by hard fact rather than glossy marketing and popular appeal of a particular type.

My next aircraft may well be a Mooney Acclaim-S when the newly tweaked aircraft becomes available next year - 243kts at 20gph @ 25Kft!

Sorry but it is difficult not to be proud of your aircraft when you fly a Mooney.

SB

IO540

According to Mooney the TKS speed loss is due to the extra prop boots/grooves/slinger ring rather than any loss of laminar flow due to the titanium leading edge panels.

I don't think that is correct in general. The TB20 goes exactly the same with and without prop TKS. The rubber boots are very thin and extend only about 1/3 up, and the slinger ring is totally hidden by the spinner.

Prop TKS is a brilliant system. Legally useless by itself (the CAA initial CofA inspector mandated an INOP sticker on the switch to stop pilots using it) but of all the legally useless things it gives you the best safety enhancement of all.

wsmempson

I think the Mooney looks like a very good, efficient piece of kit; if I fitted in one, I'd have it after the Arrow - but I don't. The twinstar looks great, but I can't name anyone I know, with either DA40's or DA42's, who have much praise for Diamond or their UK agents vis-a-vis sales aftercare. It would also appear that the product development is being left to the customer.

IO540 thanks for the email about the FAA IR - I hope the reply got through; I had a few problems emailing you back.

sternone

Pilots as tall as 6’8” fly in comfort in a mooney, i understand you must be much taller ? Have you ever been in one ? Please do so, i don't get it when people tell me the problem with mooney is that they don't have enough leg room, then i know they never have been in one.

deice

SB, are you sure the Mooney is slipperier than a Diamond? Probably when compared to a DA42, but it's got two engines hanging in the breeze. I'd like to see your Ovation engine stuck to a DA40 airframe. I think you'd get a run for your mo(o)ney... The DA40 is reminiscent of a glider which is very evident in the landing phase and when you put your nose down. Unlike a PA28or C172 you need not add power to increase speed in a descent!

I don't know if people forget, but a DA40 will easliy do 115-120 knots at 70% of 135BHP and low level (1000 feet). The DA42 is not alot faster with two engines, but twins aren't in general. Just compare the Saratoga/Seneca or Arrow/Seminole types. In fact, the Seneca 1 cruises only about 10 knots faser than a Six! 400 vs 260 horses but the weight and the drag increase is substantial!

I'm only jealous SB...

wsmempson

Yes, I've sat in a Mooney.

I've flown a Mooney P1, so I simply speak from 1st hand experience, rather than regurgitate something that someone told me in a bar, or something read in a magazine.

Legroom isn't the problem, I am long in the trunk and broad shouldered and the cockpit layout means that I am rubbing shoulders with p2 whilst I sit with a crick in my neck from the lack of headroom.

smarthawke

never flown a Mooney but we maintain two M20Js and I have a fair bit of time taxying/ground running them and it isn't a total height thing that is the problem, more of a body part ratio thing as Mr Empson has described.

Fully enclosed retracted gear on a Mooney? Not exactly, their may be more faired in than an Arrow but it isn't total, the lower doors stop half way down the wheel and the wheels don't hide fully in the wings hence the lump of plastic fairing rivetted to the wing aft of the wheel well. Lo Presti speed kits (Knots 2 U also) for an Arrow copy this idea - does it really work?

Remember the Thielert/Centurion (1.7) engine is a modded Merc A Class motor. I don't think Thielert had a lot of input when it came to the fuel system design, all they did was take a perfectly good car engine and mod it to be a not particularly reliable aircraft engine.

My diesel car is happiest cruising below 3000rpm (max torque from 2-3k). At 70mph car engines are running about 12% power. Put a car engine in an aircraft and make it turn over fast enough to produce 65% power for hours on end and wonder why they object (not to mention relatively non-lubricating properties of Jet A1 screwing up the designed for diesel fuel pump etc etc).

100LL

Ok so we know that there are confirmed luddites on this forum. A FADEC could fail, Magnetos could and have failed, Re the mooney sadly in October 2004. Or the Aeronca champ in August 2006. Not everything can be foreseen it’s only Diamond that fit the ECU backup battery and that’s good enough for EASA, LBA, Austro Control and even the FAA.
It’s taken the USA's finest nearly 50 Years to achieve this.
Lets face it when Hugo Junkers built the first metal skinned aircraft back in the 20's people said it would never work, it’s a bad idea, it will never last. Diesel power is still relatively new technology in aviation and no amount of testing can foresee all the problems. It takes a bold manufacturer to develop a completely new product and only when it’s right do the other manufacturers jump on the bandwagon ala Cessna. But then again that a 1940’s airframe with 21’st century engine.
Even Cessna have had to buy Columbia to keep up with Europe.

Smarthawke, the pumps are not the standard pump fitted to the Merc, TAE do modify them, and at cruse the engine is turning around 3500 Rpm / 2100 prop and flat out at 100% its running at 3800 Rpm / 2300 prop.

scooter boy

"Fully enclosed retracted gear on a Mooney? Not exactly, their may be more faired in than an Arrow but it isn't total, the lower doors stop half way down the wheel and the wheels don't hide fully in the wings hence the lump of plastic fairing rivetted to the wing aft of the wheel well."

Smarthawke, you are talking about an early marque of Mooney gear door on an M20J, the more recent versions completely enclose the wheels with inner and outer doors - occasionally people who operate out of rough strips elect to remove the door in order to avoid their becoming damaged.

SB

englishal

Well everyone has their prefered aeroplane....mine just happens to be the DA42 at then moment

I have a fair few hours in the DA42, the one I fly has full TKS and manages 155 kts TAS at 9500 at 75% power sipping around 6.1 US Gal per hour of JET, so if it didn't have TKS then just imagine how fast it would be (I don't think so....)...

JET A is the big thing for me. I would NEVER buy a NEW AVGAS powered aeroplane now. You'd be nuts to...If for no other reason as Avgas going out of fashion. Jet has got to be less hassle, and is also cheaper at the moment. But even if it wasn't cheaper, imagine a Twin burning 12 gals per hour.

Not sure why your mate lost his engine, unless both FADECs on that side packed up. It should have automatically switched to ECU B and there is also a manual selector switch......

sternone

The oil dropped dramaticly the last days below 90 dollar a barrel...(good news!) My idea is when the AVGAS will not be available anymore in let us say 10 years ? We will have diesel replacements that will work from Lycoming & Continental who will fit in current airframes. Continental is making a diesel engine right now.

soay

I wonder if it will take them as long to get those engines right as it did with their current 50 year old designs.

172driver

sternone, you are missing something. AVGAS already IS difficult to obtain in many places. Anything running on Jet A or Mogas definitely has a huge advantage.