An affordable twin???
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An affordable twin???
Posting a reply on another thread about twins prompted my failing memory about this What - A Twin-Engine Kit Aircraft?. I hope Chris Heintz finishes the development of this before he finally retires!! I wonder if he chose the name Gemini to reflect that lovely, affordable (ish) twin built by Mr. Miles.
I think there could be a market for this amongst the safety concious who would prefer a twin for regular overwater / montain flying. Does anybody else agree or is the market completely catered for by the Vans family and their assorted high end kit built cousins?
I think there could be a market for this amongst the safety concious who would prefer a twin for regular overwater / montain flying. Does anybody else agree or is the market completely catered for by the Vans family and their assorted high end kit built cousins?
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I think there could be a market for this amongst the safety concious who would prefer a twin for regular overwater / montain flying.
I have just 2 hours ME (against nearly 1k hours SE) but everybody knows there are all kinds of issues with twins. You need a lot of currency for it to be statistically safer, having two "cheap" engines (as in your URL) rather than one big old sturdy one is not necessarily going to be safer at all, there are complex issues with SE performance (not just at low speeds but also stuff like the SE ceiling which becomes pretty relevant over high terrain which is exactly where you may want the spare engine) and finally there is the extra drag which knocks the MPG by best part of a factor of two.
And finally there is the extra training, and the need for regular training because one does have to pass the 2 yearly checkride with a 'failed' engine. But cost is a personal decision! One would just hope to be getting something tangible for that extra money.
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Well yes but the cost is a bit of a problem, and cheap turbines are nowhere near being even on the horizon. And if you got one cheap you still have a much worse SFC than a piston engine. They are hugely reliable but make economic sense only at high altitude.
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It is a shame that cheap low powered turbines are not available.
I believe such a unit was/is being built for Mooney?
On the one hand we still have antiquated old engine designs powering our piston aircraft running on expensive and hard to get hold of Avgas.
Diesel units dont appear to be meeting their expectations.
Small low powered and low cost turbines should have been the future for GA
Pace
It is a shame that cheap low powered turbines are not available.
I believe such a unit was/is being built for Mooney?
On the one hand we still have antiquated old engine designs powering our piston aircraft running on expensive and hard to get hold of Avgas.
Diesel units dont appear to be meeting their expectations.
Small low powered and low cost turbines should have been the future for GA
Pace
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The last post on this development is about 10 years old 
Don't hold you breath. There is the Tecnam twin about to go on sale, which is probably a better bet if you have around Euro 350,000 to spend 
Don't hold you breath. There is the Tecnam twin about to go on sale, which is probably a better bet if you have around Euro 350,000 to spend
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I think there could be a market for this amongst the safety concious who would prefer a twin for regular overwater / montain flying.
However, I wonder if you really do have double the chance of failure in a twin. I suspect that a significant number of engine problems/failures are due to maintenance, misuse, mismanagement or missing fuel. Suggesting that if one goes, the other may well follow soon suggesting that to most practical purposes the extra expense of a twin really probably is about peace of mind rather than any significant strides in terms of safety.
An ex-RAF chap at one of the clubs I'm with gave pretty much the same summary of the safety aspects of having a second engine. Apparently some twins cannot climb on a single engine, they can only maintain height. So if one engine fails at a point where you need to climb you are stuffed.
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normally aspirated twins would struggle to hold 4,000' AMSL on one engine, probably more like 3,500; which is less than the MSA over just the hills of the UK. Add turbocharging and you're probably well to the right of relatively 'affordable' compared to a decent high performance single, even then don't expect much above 8,000'.
I agree the BE76 or Seminole have pretty crap SE performance.I'd rather fly a decent twin any day though. With a SE if the engine fails you have one option, go down. Most light twins I've flown can fly quite happily on one engine, even when moderately loaded. Turbo's make a great difference though and even the likes of a Twin Star with 3 POB and overnight baggage and lots of fuel (probably at Max UUW) will happily climb on one engine to a good altitude.
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Hello!
Our flying school Seminole (non-turbo!) easily maintains 6000ft on one engine. With the exception of the Alps, you can fly anywhere in central Europe at that altitude. And other than with some more complex twins like the C340 or C421B, all the fuel on board is available to the remaining engine, so longer overwater flights can safely be completed.
At this time of the year with poor weather and early darkness, I feel much safer in the lightest of light twins than in any piston single.
Greetings, Max
Should read "most knackered old training type twins..." I agree the BE76 or Seminole have pretty crap SE performance.
At this time of the year with poor weather and early darkness, I feel much safer in the lightest of light twins than in any piston single.
Greetings, Max
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Thank you Englishal for fighting against the twin bashing.
The higher up the flying ladder you go, the higher the requirements for currency, eye hand coordination and systematic handling of the craft.
Those who can only fly less than 25 hours per year should not fly twins or even complex singles, even less so if one wants to fly at altitude with oxygen or in marginal weather.
But those that can afford to fly regularly in a modern proven twin and who have the eye hand coordination, the urge to fly accurately and who by their very nature enjoy the renewal stress could do a lot worse than flying something like a good modern Seneca, a Baron or a DA42
Those people can afford to fly high over the Alps, Pyrenees, Carpats etc or at night over the sea with more confidence at speeds close to 200 knots true, often well above the weather and feel not too distant from the professional flyers.
I have found flying my twin mch more usefull than the PA28's i flew before, more enjoyable and indeed more people now fly with me.
The higher up the flying ladder you go, the higher the requirements for currency, eye hand coordination and systematic handling of the craft.
Those who can only fly less than 25 hours per year should not fly twins or even complex singles, even less so if one wants to fly at altitude with oxygen or in marginal weather.
But those that can afford to fly regularly in a modern proven twin and who have the eye hand coordination, the urge to fly accurately and who by their very nature enjoy the renewal stress could do a lot worse than flying something like a good modern Seneca, a Baron or a DA42
Those people can afford to fly high over the Alps, Pyrenees, Carpats etc or at night over the sea with more confidence at speeds close to 200 knots true, often well above the weather and feel not too distant from the professional flyers.
I have found flying my twin mch more usefull than the PA28's i flew before, more enjoyable and indeed more people now fly with me.
Small "cheap-ish" turbines are available for the home built market..
Innodyn :: Aviation :: The Innodyn Turbines
Article on them here:
Aero-News Network: The Aviation and Aerospace World's Daily/Real-Time News and Information Service
Here is an RV with an Innodyne:
Innodyn :: Aviation :: The Innodyn Turbines
Article on them here:
Aero-News Network: The Aviation and Aerospace World's Daily/Real-Time News and Information Service
Here is an RV with an Innodyne:
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The biggest problem with these twin v. single debates is that they usually fail to separate the two very different things
1 - stuff which only a twin gives you
A spare engine
At the top piston end (e.g. a C421) loads of payload and speed
2 - stuff which a single can give you but is more common on twins
Full de-icing
Redundant electrical systems (see Cessna 400 for an example)
Good capability versus weather
Pressurisation
One would be a fool to be flying a twin to get a high operating ceiling for example, when any half decent SE IFR tourer can go to 20k and the turbo ones can do 25k.
If I recall right, the NTSB data shows SE turbines about 5x less likely to go down than piston twins. Now, this could be hiding a lot of factors, for example the population of SE turbines is likely to be younger and better maintained than the population of piston twins (just look around your airfield for ample evidence of this).
The extra cost of a piston twin is high. I reckon the total operating cost of a Meridian and even more so a Jetprop is going to be similar to the OC of a Seneca or something similar. Well, after the capital cost has been set aside
1 - stuff which only a twin gives you
A spare engine
At the top piston end (e.g. a C421) loads of payload and speed
2 - stuff which a single can give you but is more common on twins
Full de-icing
Redundant electrical systems (see Cessna 400 for an example)
Good capability versus weather
Pressurisation
One would be a fool to be flying a twin to get a high operating ceiling for example, when any half decent SE IFR tourer can go to 20k and the turbo ones can do 25k.
If I recall right, the NTSB data shows SE turbines about 5x less likely to go down than piston twins. Now, this could be hiding a lot of factors, for example the population of SE turbines is likely to be younger and better maintained than the population of piston twins (just look around your airfield for ample evidence of this).
The extra cost of a piston twin is high. I reckon the total operating cost of a Meridian and even more so a Jetprop is going to be similar to the OC of a Seneca or something similar. Well, after the capital cost has been set aside
Thread Starter
Bringing it back to the realms of affordable VFR day-only twins I can see why Chris Heintz isn't putting any effort into developing the Gemini. The extra cost of the 2nd engine isn't offset against the potentially increased risk of an engine failure. The reason I looked at this initially was that then I had the potential to be flying across to Ireland regularly and for that I would like two engines. I know the Rotax 912 or Jabiru engine that the Gemini would potentially use seem as reliable as your average car engine so the actual risk is relatively low, but half way across the cold Irish Sea I would feel greatly reassured looking past my 10-year old daughter at the spare "get out of jail free" card sitting on the wing!
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the future of GA?
the future of GA?
On the bottom of the PDF it gives a table comparing the Tecnam with 2 rotax engines to its GA rivals, cessna 172,Cirrus,Piper,Da 40 ect
http://www.tecnam.com/PDF/schede/twin.pdf
On the bottom of the PDF it gives a table comparing the Tecnam with 2 rotax engines to its GA rivals, cessna 172,Cirrus,Piper,Da 40 ect
http://www.tecnam.com/PDF/schede/twin.pdf
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Twins versus singles - now here is an old chestnut.
The first comment people usually make is that twins are less safe. That statement is wholly erroneous without qualification. Twins are, on the whole, used for quite different mission profiles. Far more poor weather sectors are flown in twins - because on the whole they can cope with worse weather.. The general statistics also pay regard to the experience over the last forty years. Particularly in the States it dawned many years ago that twins were susceptible to asymmetric accidents in particular, and accidents in general with pilots flying in conditions for which they had inadequate training. Twin training has improved enormously in that time and even more importantly the insurance companies had made it increasingly difficult for inadequately trained pilots to find cover. There is no evidence in the current environment that twins are less safe, and if you take account of the mission profiles flown they are more safe than singles.
There are many similarities with high performance singles. In the early years the accident rate in the Cirrus was far higher than you would have expected. Pilots with inadequate training were lulled into a false sense of security by the fancy avionics, performance and promise of a state girdling light single. Of course the Cirrus was still a single, and with its added performance less forgiving in poorly trained hands than a Cherokee. The training has improved enormously, and in the States at least the insurance companies have set the standard. The accident rate is probably now better than that for other singles. (Probably because statistically it is still early days).
It is true that the climb performance of many twins on a single engine is poor or almost non existent. It is equally true that for many twins the climb performance is acceptable. How many critical engine failures do you read about each year in the UK? Of these how many singles do well in terms of avoiding injuries?
I have quite a few hours on 42s. An engine failure immediately after take off before you have cleaned up the undercarriage is an issue, but not unmanageable. An engine failure a few moments later is also an issue but far less of one. As long as you are on the ball the aircraft continues to climb quite nicely even at MAUTW - I have flown singles that barely do much better. An engine failure in the cruise is a complete non event. I had one last year. If I had to we would have flown on for as long as necessary. Personally I don’t subscribe to the school that a failure is anything other than an emergency and I don’t subscribe to flying home on one engine - but if there is no alternative one could and would. Had I been in a single which might easily have developed exactly the same fault I would have landed in a field. With luck I would not have been uninjured, with a whole lot more luck the aircraft might have survived without a reasonable amount of damage, but probably not.
In the last two weeks two Cirrus have sadly been lost due potentially to engine failures. In once case the pilot lost his life, in the other one crew member escaped without injury, the other was injured. The aircraft is a write off. In a twin with a current pilot if the accidents were caused by an engine failure neither the aircraft or crew would have suffered any consequence.
On the whole twins carry more weight. On the whole twins are better equipped to cope with weather. That does not mean to say singles cannot be so equipped but in reality few are. Twins will typically be certified for flight in known icing. Twins will typically have boots rather than fluid which is only “lifed” for as long as the fluid in the reservoir lasts. Twins on the whole have significantly higher cross wind limits and are more stable both on the approach and in flight. If you care to fly an Aztec in turbulence, and a single in the same conditions you may well wonder why the passengers are throwing up in the single. Twins on the whole have significantly more redundancy. Twins are on the whole are faster and perform significantly better - at least when both engines are working!
Some modern high performance singles attempt to emulate twins on some of these counts but none emulate twins on all counts.
In defence of twins you therefore get a great deal more than just an extra engine. On the whole you get better performance, greater comfort, more redundancy, improved all weather capability and, with a current and well trained pilot, more safety.
One last thing - you worry a whole lot less. I know engine failures are remarkably rare. I know the engine doesn’t know it is over the sea or the Alps or it is night or there is a 800 foot base. Never the less it still doesn’t stop me worrying in a single half way to the CI in the middle of February with a cold 5 foot swell beneath that an engine failure will definitely ruin my day. I would only fly twins if safety was the sole issue - as it is singles are good fun to fly for other reasons, and a whole lot less expensive.
So to answer your question Diamond were brave enough to try and prove there was a market for a modern twin - inspite of the ill informed bad publicity with which they had to contend - I think they have been very successful in that regard if let down by the choice of engine. Tecnam will hopefully apply the same formula to powering a mdern twin with a much cheaper Rotax already used in loads of non certified aircraft. They apparently have a pretty good order book. I hope others try.
The first comment people usually make is that twins are less safe. That statement is wholly erroneous without qualification. Twins are, on the whole, used for quite different mission profiles. Far more poor weather sectors are flown in twins - because on the whole they can cope with worse weather.. The general statistics also pay regard to the experience over the last forty years. Particularly in the States it dawned many years ago that twins were susceptible to asymmetric accidents in particular, and accidents in general with pilots flying in conditions for which they had inadequate training. Twin training has improved enormously in that time and even more importantly the insurance companies had made it increasingly difficult for inadequately trained pilots to find cover. There is no evidence in the current environment that twins are less safe, and if you take account of the mission profiles flown they are more safe than singles.
There are many similarities with high performance singles. In the early years the accident rate in the Cirrus was far higher than you would have expected. Pilots with inadequate training were lulled into a false sense of security by the fancy avionics, performance and promise of a state girdling light single. Of course the Cirrus was still a single, and with its added performance less forgiving in poorly trained hands than a Cherokee. The training has improved enormously, and in the States at least the insurance companies have set the standard. The accident rate is probably now better than that for other singles. (Probably because statistically it is still early days).
It is true that the climb performance of many twins on a single engine is poor or almost non existent. It is equally true that for many twins the climb performance is acceptable. How many critical engine failures do you read about each year in the UK? Of these how many singles do well in terms of avoiding injuries?
I have quite a few hours on 42s. An engine failure immediately after take off before you have cleaned up the undercarriage is an issue, but not unmanageable. An engine failure a few moments later is also an issue but far less of one. As long as you are on the ball the aircraft continues to climb quite nicely even at MAUTW - I have flown singles that barely do much better. An engine failure in the cruise is a complete non event. I had one last year. If I had to we would have flown on for as long as necessary. Personally I don’t subscribe to the school that a failure is anything other than an emergency and I don’t subscribe to flying home on one engine - but if there is no alternative one could and would. Had I been in a single which might easily have developed exactly the same fault I would have landed in a field. With luck I would not have been uninjured, with a whole lot more luck the aircraft might have survived without a reasonable amount of damage, but probably not.
In the last two weeks two Cirrus have sadly been lost due potentially to engine failures. In once case the pilot lost his life, in the other one crew member escaped without injury, the other was injured. The aircraft is a write off. In a twin with a current pilot if the accidents were caused by an engine failure neither the aircraft or crew would have suffered any consequence.
On the whole twins carry more weight. On the whole twins are better equipped to cope with weather. That does not mean to say singles cannot be so equipped but in reality few are. Twins will typically be certified for flight in known icing. Twins will typically have boots rather than fluid which is only “lifed” for as long as the fluid in the reservoir lasts. Twins on the whole have significantly higher cross wind limits and are more stable both on the approach and in flight. If you care to fly an Aztec in turbulence, and a single in the same conditions you may well wonder why the passengers are throwing up in the single. Twins on the whole have significantly more redundancy. Twins are on the whole are faster and perform significantly better - at least when both engines are working!
Some modern high performance singles attempt to emulate twins on some of these counts but none emulate twins on all counts.
In defence of twins you therefore get a great deal more than just an extra engine. On the whole you get better performance, greater comfort, more redundancy, improved all weather capability and, with a current and well trained pilot, more safety.
One last thing - you worry a whole lot less. I know engine failures are remarkably rare. I know the engine doesn’t know it is over the sea or the Alps or it is night or there is a 800 foot base. Never the less it still doesn’t stop me worrying in a single half way to the CI in the middle of February with a cold 5 foot swell beneath that an engine failure will definitely ruin my day. I would only fly twins if safety was the sole issue - as it is singles are good fun to fly for other reasons, and a whole lot less expensive.
So to answer your question Diamond were brave enough to try and prove there was a market for a modern twin - inspite of the ill informed bad publicity with which they had to contend - I think they have been very successful in that regard if let down by the choice of engine. Tecnam will hopefully apply the same formula to powering a mdern twin with a much cheaper Rotax already used in loads of non certified aircraft. They apparently have a pretty good order book. I hope others try.
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I think the DA42 was a great formula which would have eventually been very successful.
Total flow rate is identical to my TB20, at the same cruise speed of 140kt (11GPH) but you get a spare motor in that.
I say "eventually" because Diamond p*ssed off so many people and that was before Thielert went bust. The reliability was so poor that one needed the second engine! I know of a number of owners and almost none of them dared to fly them anywhere too far. Defeats the point of a twin, completely.
I am sure 5-10 years from now it will be a well shaken down airframe with reasonably reliable engines. Shame it will have taken that long. That is longer than most private pilots' flying career.
Total flow rate is identical to my TB20, at the same cruise speed of 140kt (11GPH) but you get a spare motor in that.
I say "eventually" because Diamond p*ssed off so many people and that was before Thielert went bust. The reliability was so poor that one needed the second engine! I know of a number of owners and almost none of them dared to fly them anywhere too far. Defeats the point of a twin, completely.
I am sure 5-10 years from now it will be a well shaken down airframe with reasonably reliable engines. Shame it will have taken that long. That is longer than most private pilots' flying career.
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I say "eventually" because Diamond p*ssed off so many people and that was before Thielert went bust. The reliability was so poor that one needed the second engine! I know of a number of owners and almost none of them dared to fly them anywhere too far. Defeats the point of a twin, completely.
I have not had any failures on the 42 (other than the engine
) which made be nervous about going far, and the failures that have occurred have been minor. That is the experience of others to whom I have spoken. I guess with any new aircraft (and I dont mean in the design sense) there is some inevitable beding in - I have had the coms fail for example, but I think in the early days you had similiar issues with your TB20. Whether or not these issues should arise at all is debatable - perhaps it is just poor quality control. Everyone is pi**ed over the issues with the engines but that is well rehearsed. 42s have had a lot of "heavy" use with the schools and have been used and abused as only a training aircraft can. As we have discussed how well they will really stand up to the test of time once they have been left out on the pan in all weathers remains to be seen - but that is another story.I think the 42 with twin Lycomings as now been rolled off the production line could be a great twin fro anyone needing just 4 seats.
I would be interested to know what specific reliability issues people have had with 42s?