Thanks for the 'clean-up'.
I didn't know the actual order of magnitude - but clearly it was a rhetorical question.
The other thing is that in a turboprop you are likely to be at FL250 or so and your glide range (with say a 30-40nm radius, zero wind) is quite likely to include an airport.
Assuming the battery lasts long enough...
The other thing is that in a turboprop ...
And what about piston twin like Seneca, Baron or DA42 in terms of safety margin for night IFR and flying in IMC in general?
Some, possible me, would rather have a single turboprop than a piston twin.
However, a piston twin (if not too heavy) should be able to maintain altitude or at least only a very slight rate of decent. But, unless turbo, it's unlikely you'll be up at Peter's F250 at #25
I think this issue is overblown. When you look at the stats, actual mechanical failure is rarely the cause of an accident. If the engine stops, it is usually fuel exhaustion. With the Mirage at FL250, I have around 50nm glide range.
That said, I am quite sure that a turboprop is more reliable but we are talking more reliable than an incredibly reliable engine.
The problem is the pilots not the piston engine (although of course there are exceptions even with turbines).
I was thinking of all of this as I flew home tonight. Since daylight time ended, the flight home at the end of the day is no longer lit! I had to make a stop at another airport along the way home. Though I have flown out of that one for 30 years, I am still very careful at night. The departure is out over a black hole. By discipline, as soon as I rotate, and see positive rate, it's on instruments, 'cause there is nothing to see ahead outside. Climb to 500 feet, then re-establish the outside world.
When I arrived home, and crossed overhead, I noticed a white light off the extended centerline of my runway, and apparently several hundred feet up. it looked like another aircraft on final, but it was not moving. I know there's no tower there (well, there was not when I took off this aft, but they do spring up quickly!). I fixated on it as I joined mid downwind. Once established on downwind it began to move away. I then figured out that it was a car driving along, on a road several miles away, but the relative motion of me, and the car, cancelled each other out, and for a long time the car appeared still.
The night has all kinds of illusions, and tricks to normal visual cues..
[Pilot DAR] I noticed a white light
Sorry, slightly off topic. This reminds me of last Friday's flight from Shobdon back to WW, with the sun down on the horizon at 3.30pm, when I saw this blinding light in the distance, and mistaking it briefly for another aircraft travelling opposite direction, similar level. Turned out to be the Shard (new 1,016ft skyscraper in London)!
Spurious lights were a suspect in Graham Hill's (the F1 driver) crash, although this was mentioned in one of the books written about it rather than the official report.
I've certainly seen plenty of lights which were misleading. This is why GPS is so useful even for "official VFR". You can set up a DCT to the airport and set the OBS to the runway track, and set yourself up on the inbound track exactly.
However, in one case the light was a helicopter apparently hovering c. 300ft AGL, right on the approach path. Or he may have been climbing UP the approach path at the same time I was coming in. I went around and then I saw it. After I landed I walked over to him to find out more but he (an instructor) ran off...
That said, I am quite sure that a turboprop is more reliable but we are talking more reliable than an incredibly reliable engine.
Jason - what is your take on the PA46 piston engine issues? I didn't want to mention this until you got home 
but one famous report (albeit criticised for being a selective sample) found a 10% rate of in-flight engine shutdowns, IIRC. The engine was at some stage changed from Conti to Lyco which reportedly helped. One pilot I spoke to used to work in the USA doing specialised night express cargo in a PA46 and they were swapping cylinders every few hundred hours. More advanced pilots say it is due to excessive CHTs, which is all too easy to achieve without engine instrumentation. I am sure you must have done the research.
Jason - what is your take on the PA46 piston engine issues? I didn't want to mention this until you got home but one famous report (albeit criticised for being a selective sample) found a 10% rate of in-flight engine shutdowns, IIRC. The engine was at some stage changed from Conti to Lyco which reportedly helped. One pilot I spoke to used to work in the USA doing specialised night express cargo in a PA46 and they were swapping cylinders every few hundred hours. More advanced pilots say it is due to excessive CHTs, which is all too easy to achieve without engine instrumentation. I am sure you must have done the research.
I think like many things in this aircraft the engine needs careful disciplined control or you can get into trouble. Overall I think the Lycoming is fine but in leaning when established at your cruise altitude, 23gals/h gives 1650 TIT and sub 400f CHTs. If you are a little more aggressive and go much below you can be up over the 1750 red line easily - excluding LOP. Engine problems are now regarded as very rare however the engines rarely make TBO without a top end being done. I think an engine monitor is mandatory..
