Those Diamonds ..
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Those Diamonds ..
Noticed the new Twinstar in Bankstown last week, any feed back from anyone in the know.....
nice bit of gear, hope this is the future
nice bit of gear, hope this is the future
One would have thought that with the engines being "aero diesels" they would be more reliable than the avgas engines we fly. At least the "old clunky" Lycomings and Continentals don't stop when the battery is a bit low.
Avionics wise they are very smart, but nothing that can't be installed elsewhere in a new aircraft or in some cases retro fitted to existing aircraft.
Performance (cruise speed, payload etc) wise the Twin Star doesn't match what was being built over 20 years ago. I see that their original performance claims have been down graded by a big margin, from memory cruise speed of about 190 KTAS were first quoted now the highest figure quoted is around 165 KTAS. They don't list single engine rate of climb figures on their website info.
From what I hear, engine TBO's are quite low at the moment and the engines have to be sent back to the factory for overhaul/replacement.
When I've seen them fly they look like their climb rate is greatly aided by the curvature of the earth, this may due to the way they are operated.
On the ground they look fugly, in that air they sound like a rotax powered twin.
Avionics wise they are very smart, but nothing that can't be installed elsewhere in a new aircraft or in some cases retro fitted to existing aircraft.
Performance (cruise speed, payload etc) wise the Twin Star doesn't match what was being built over 20 years ago. I see that their original performance claims have been down graded by a big margin, from memory cruise speed of about 190 KTAS were first quoted now the highest figure quoted is around 165 KTAS. They don't list single engine rate of climb figures on their website info.
From what I hear, engine TBO's are quite low at the moment and the engines have to be sent back to the factory for overhaul/replacement.
When I've seen them fly they look like their climb rate is greatly aided by the curvature of the earth, this may due to the way they are operated.
On the ground they look fugly, in that air they sound like a rotax powered twin.
not quite related but i've spent a fair bit of time in the single diamond. Quite unimpressed with the performance. 120kt tas, 70kt climbout at 500fpm initial.
Not a bad training aircraft though as the performance is manageable for a student compared to something like a cirrus.
Not a bad training aircraft though as the performance is manageable for a student compared to something like a cirrus.
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From the little I have read, I think the problem is the Thielert engines, I believe they are simply asking too much from a 1700cc diesel engine, period.
As it is, they have a billet steel crank and special pistons, but the trouble is that aviation and marine engines live their lives at very high continuous power settings compared to automotive engines and the auto engines can't take it.
Bear in mind that a Commodore may have 160Kw or whatever, but when it is travelling at 100kmh it is only using 19kw!
To put it another way, you can take a 2 litre Suburu engine and tweak it to 400 hp - but try running it at that horsepower continuously and see what happens, it will last maybe an hour or two, thats why a 400hp truck engine is so big, its running at a much higher load. The limiting factor being getting rid of the heat associated with generating the high horsepower.
I suspect that if Thielert started with the 2 litre version of the Mercedes diesel they could deliver on their promises, but I reckon they are asking too much of that little 1.7 engine.
As it is, they have a billet steel crank and special pistons, but the trouble is that aviation and marine engines live their lives at very high continuous power settings compared to automotive engines and the auto engines can't take it.
Bear in mind that a Commodore may have 160Kw or whatever, but when it is travelling at 100kmh it is only using 19kw!
To put it another way, you can take a 2 litre Suburu engine and tweak it to 400 hp - but try running it at that horsepower continuously and see what happens, it will last maybe an hour or two, thats why a 400hp truck engine is so big, its running at a much higher load. The limiting factor being getting rid of the heat associated with generating the high horsepower.
I suspect that if Thielert started with the 2 litre version of the Mercedes diesel they could deliver on their promises, but I reckon they are asking too much of that little 1.7 engine.
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Fadec?
It seems to be the fadec control system that is letting them down. It is not the first time the fadec system has had problems. There was an AD some time ago which was triggered by a fadec failure.
Diesels make sense if they can get them right. It would be great to be rid of all those spark plugs and magnetos that give us so many problems.
I still like the idea of a metal aircraft, if it is going to spend lots of it's time sleeping out in the open, as most do in Australia.
Also, this electronic stuff will have to stay near the capital cities, because our third world maintenance system will not be able to cope.
Diesels make sense if they can get them right. It would be great to be rid of all those spark plugs and magnetos that give us so many problems.
I still like the idea of a metal aircraft, if it is going to spend lots of it's time sleeping out in the open, as most do in Australia.
Also, this electronic stuff will have to stay near the capital cities, because our third world maintenance system will not be able to cope.
I suspect that if Thielert started with the 2 litre version of the Mercedes diesel they could deliver on their promises, but I reckon they are asking too much of that little 1.7 engine.
Your points regarding the engines is noted and I agree re trying to extract high and reliable power from small engines. Also gearboxes on aero engines have generally been a dismal failure when you have less than 9 cylinders. I think part of the low TBO figure is gearbox related.
A good example of high tech not necessarily being the best choice.
I see on their website that they are talking of a Lycoming (IO360 I think) version as well. Perhaps this is an admission that the original engine choice might have not been the best choice.
Remember it was Diamond who made the promises re the performance of the Twin Star not Thielert. Diamond should have known what performance to expect with the engines they chose for the airframe they designed.
Bushy,
Have to agree re magnetos and spark plugs, metal airframes and the ability to repair/maintain in remote areas.
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Nah the double engine failure was because of a double fuel pump failure where both pumps get electrical supply from the same source. A/C now being fitted with independant power systems or something..it was in AVFLASH!?
Does look like a plastic kids toy though..sounds like two sewing machines
Does look like a plastic kids toy though..sounds like two sewing machines
Nah the double engine failure was because of a double fuel pump failure where both pumps get electrical supply from the same source. A/C now being fitted with independant power systems or something..it was in AVFLASH!?
Did you read the story from the link in SDT's post? It states the problem was a voltage fluctuation affecting the engine control units.
I would have thought any fuel pumps would be engine driven with perhaps electric back ups.
Grandpa Aerotart
Sorta puts some perspective into the 'old technology' rubbish engines that Continental and Lycoming produce don't it.
Anyone who suggests that an IO520 or IO540 produced today is the same engine as 20 years ago is dreaming....many, many incremental improvements have been rought on those engines...in production methods and materials if nothing else.
There is a reason why nothing much of an earth shattering nature has happened in piston engines for a very long time.
You can slag off TCM and Lyc for a few things, without doubt, but they produce very efficient and reliable engines when you take into account the dispacement, weight and reliability demanded of them...GAMi-ise them and they are unbeatable...TN them as well and Diesels get left in their wakes...see avgas fall back in price (again) and diesels will once again hit the shelf for another decade or two.
I did some numbers on the Theilert V8 diesel engine v my IO550b...the IO550b is MILES in front overall...I then I heard Theilert had no plans anyway for a Bonanza certification because of the nose bowl design.
Anyone who suggests that an IO520 or IO540 produced today is the same engine as 20 years ago is dreaming....many, many incremental improvements have been rought on those engines...in production methods and materials if nothing else.
There is a reason why nothing much of an earth shattering nature has happened in piston engines for a very long time.
You can slag off TCM and Lyc for a few things, without doubt, but they produce very efficient and reliable engines when you take into account the dispacement, weight and reliability demanded of them...GAMi-ise them and they are unbeatable...TN them as well and Diesels get left in their wakes...see avgas fall back in price (again) and diesels will once again hit the shelf for another decade or two.
I did some numbers on the Theilert V8 diesel engine v my IO550b...the IO550b is MILES in front overall...I then I heard Theilert had no plans anyway for a Bonanza certification because of the nose bowl design.
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Most of what you said is right 27/09. But climb performance actually isn't that bad - roughly 1000fpm to 10,000ft at heavy weight and 100kts. Asymmetric performance is similar to what you'll get out of a Seminole or Duchess at sea level.
Regarding the engines - yes, it seems the 1.7 litre engines aren't coping. I hear that Diamond are intending to retrofit derated 2 litre engines to the world's fleet when 1.7 l engines come up for overhaul. Might help.
Repair in remote areas is expensive as Bushy said. I suspect fibreglass airframes might not last all that long. But with respect to advanced engines - car engines got dragged those into the 21st century despite the trouble and expense of repairing the computers. Just like the age of fiddling with the carburettor has gone, I suppose in aviation the age of the local LAME tweaking the mixture is going to go too. "Replace the FADEC and she'll be right mate" - catchcry of the 2020's...
I realised how different engine handling is going to become when I climbed (full power) through 10,000', then did a power lever closed descent near Vne through 10,000'. T's & P's barely moved, and certainly didn't stray out of the green.
Regards to all,
O8
Regarding the engines - yes, it seems the 1.7 litre engines aren't coping. I hear that Diamond are intending to retrofit derated 2 litre engines to the world's fleet when 1.7 l engines come up for overhaul. Might help.
Repair in remote areas is expensive as Bushy said. I suspect fibreglass airframes might not last all that long. But with respect to advanced engines - car engines got dragged those into the 21st century despite the trouble and expense of repairing the computers. Just like the age of fiddling with the carburettor has gone, I suppose in aviation the age of the local LAME tweaking the mixture is going to go too. "Replace the FADEC and she'll be right mate" - catchcry of the 2020's...
I realised how different engine handling is going to become when I climbed (full power) through 10,000', then did a power lever closed descent near Vne through 10,000'. T's & P's barely moved, and certainly didn't stray out of the green.
Regards to all,
O8
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Reading between the lines on the Avweb report of the double engine failure, it might well come to be that pilot error played a part. It appears the alternators didn't come on line following a flat battery ground start scenario.
The composite FRP airframe should prove to be more durable to weathering than alloy structures with reasonable care, and in field repairs to the structure not much harder than alloy aircraft, just different.
For the petrol heads, interesting to note that the BSFC is .365 lb/hp/hr., not that much better than a properly set up TCM at around .385
The looks of the machine maybe a bit subjective, I reckon they look sh*t hot.
Performance appears quite good 165 TAS on about 210 hp for a burn rate of about 45L/hr.
Love the old engines but herald the arrival of some new technology and fresh thinking. But fair suck of the sav these guys got of their arses and made it happen, shame that sought of thing doesn't happen in Oz (Jabiru excempted).
It would be a bit of an ask to expect them to hit the market with a new product and get it perfect first go.
Time will tell the full story I guess.
M
The composite FRP airframe should prove to be more durable to weathering than alloy structures with reasonable care, and in field repairs to the structure not much harder than alloy aircraft, just different.
For the petrol heads, interesting to note that the BSFC is .365 lb/hp/hr., not that much better than a properly set up TCM at around .385
The looks of the machine maybe a bit subjective, I reckon they look sh*t hot.
Performance appears quite good 165 TAS on about 210 hp for a burn rate of about 45L/hr.
Love the old engines but herald the arrival of some new technology and fresh thinking. But fair suck of the sav these guys got of their arses and made it happen, shame that sought of thing doesn't happen in Oz (Jabiru excempted).
It would be a bit of an ask to expect them to hit the market with a new product and get it perfect first go.
Time will tell the full story I guess.
M
