Do you mean that you would go for another turboprop engine or do you mean you would spend your money on a completely different non-turbine engine?Quote:
Originally Posted by steveinindy
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Do you mean that you would go for another turboprop engine or do you mean you would spend your money on a completely different non-turbine engine?Quote:
Originally Posted by steveinindy
Ok this will be my last question:
Hypothetically if that TP-100 had lower fuel burn than a piston, let's say close to what a diesel engine burns (I know that it's not possible, but let's just assume that it was), and it was FAA certified. Would you still stick to the piston even if the price premium was "only" 25-50% over the piston??
Assume even that after 4000 hrs of use the total cost of the engine will be lower than for the piston (assuming lower operating (fuel+maintenance) cost). I know that 4000hrs is almost a lifetime for a GA private pilot.
Seeing as there's no good turbine engine for that price and the fact that the low to middle end of GA (which is what we're discussing here) is well served by much easier/cheaper to maintain piston engines....Quote:
Do you mean that you would go for another turboprop engine or do you mean you would spend your money on a completely different non-turbine engine?
If I were looking to get a turbine (which I am for the larger design I am working on), the engine is going to run me for at a minimum for $150,000 to $160,000. That's for a 940 hp (at sea level) TPE-331-10 that's used and about half way through it's TBO cycle. New, it's closer to $400,000.
By comparison, a high end turbocharged piston engine for the top end of what most people consider GA (TIO-540-AE2A) will run you about $150,000 new or about $120,000 for a factory rebuild. Unless you have to go freakishly fast (>275-300 knots) or really high (>FL280) to accomplish your "mission", there's no reason to pay more for an engine that is used and sucks more fuel under most circumstances (until you get up into the really high flight levels (>FL350)). It just doesn't make sense.
The only reason I am going for a turbine is because of my desire to go very long distances (think Indianapolis to the northeastern islands in the Caribbean or Boston to LA without refueling ) and the most efficient way to do that is at high altitude and high speed. That more or less requires a turbine powerplant. Most people aren't looking for that sort of thing.
So, if I were your "average" GA pilot and not my own heady blend of slightly crazy, for $125K I'm getting a new top of the line Lycoming and enjoying still being able to pass >80% of the planes at the local airport.
So like 3 gph less than a similar piston engine?Quote:
let's say close to what a diesel engine burns
The thing is that it is possible. The issue is that most GA pilots don't do the sort of flying that is suited to turbine engines to have that kind of efficiency. The average cross country flight for a GA pilot is somewhere between 100 and 200 miles. There's literally no benefit to it because even a ten or twenty knot difference in cruising speed over that short of a distance isn't going to make that much of a difference in time. Also take into account that to get to the "sweet spot" altitude for nearly any turbine is going to take you 30-50+ miles. For shorter flights, you'd literally go almost from cruise power to flight idle for the descent because top of climb and top of descent are going to be more or less the same point.Quote:
Hypothetically if that TP-100 had lower fuel burn than a piston, let's say close to what a diesel engine burns (I know that it's not possible, but let's just assume that it was),
For low altitude "standard GA" flying? Yes. A turbine is simply a round peg trying to be crammed into the smaller square hole of GA in the majority of flights. I hate to say it (since I'm one of the "fans" of turbines on this forum) but you seemed to have picked an argument for your paper that's more or less defensible and anyone who knows much about flight operations or aircraft engines would be able to rip it apart.Quote:
Would you still stick to the piston even if the price premium was "only" 25-50% over the piston??
Here's the problem: neither of those are cheaper. I'm actually looking at doing the training to become an A&P just so I can maintain my own engine because of the costs associated with turbine maintenance. In most places (unless you're operating at a field that has a LOT of commercial traffic and very little GA....think Honolulu), you're going to pay considerably more for Jet-A than 100LL.Quote:
assuming lower operating (fuel+maintenance) cost
Google "cycle maintenance" or "calendar maintenance". If you have a low use rate, you still have to have it overhauled every few years (5 or 10 depending on the model) because one of the worst things you can do to engines is let them sit. It's asking for corrosion to not at least have it looked at.Quote:
I know that 4000hrs is almost a lifetime for a GA private pilot.
You've asked for honest opinions and you've gotten them. Trying to reword the question to fit your desired result isn't exactly real research.Quote:
Originally Posted by kjensen
Yes, something like that. They say that diesel is about 20-30% less than gasoline, so let's assume that this hypothetical turbine engine burns 10-20% less than a gasoline piston, even at low altitude.Quote:
Originally Posted by steveinindy
If you assume that a turbine burns less than a piston even at low altitude, would that change your opinion?Quote:
For low altitude "standard GA" flying? Yes. A turbine is simply a round peg trying to be crammed into the smaller square hole of GA in the majority of flights.
I appreciate your information on this!
LOL Eh....depends on where you're at. Around here, the difference is $0.17 a gallon at the airport we use ($5.90 vs $5.73).Quote:
They say that diesel is about 20-30% less than gasoline, so let's assume that this hypothetical turbine engine burns 10-20% less than a gasoline piston, even at low altitude.
What he said.Quote:
You've asked for honest opinions and you've gotten them. Trying to reword the question to fit your desired result isn't exactly real research.
I strongly suggest you take some classes on statistics or how to formulate research questions because positing all these wild hypotheticals that are never going to happen just to suit your desire to prove that a turbine engine can be a "disruptive technology" for general aviation. I can argue that we might be able to lift 747 loads with a weed whacker engine but I'd have to frame it like "Would you think it was viable if gravity were suddenly reduced by 99.999999999999%?". Either way, any rational person who is well versed in the subject (or goes back and checks your citations) is going to leave you doing the academic equivalent of bleeding from your rectum with that sort of theorizing.Quote:
If you assume that a turbine burns less than a piston even at low altitude, would that change your opinion?
Go to your professor and admit you picked a non-viable choice. It's a better choice than trying to BS an argument that- unless your professor drools uncontrollably or smokes joints the size of tampons prior to grading papers- will result in you failing the class. Most professors will support you coming to them and realizing that you've done enough research to know that what you thought initially doesn't pan out.
I talked to the Mistral people today at the AERO. The status is that the engines have successfully been flown, but the company is too short of money to certify them. They have changed their marketing concept and are now aiming at the homebuilt and experimental market. They claim that there are already some flying in the US. The price for the 200 HP engine is 45000 EURO and the 300 HP costs about 54000 EURO. I think we have to wait until Mistral finds a strong investor for seeing their engines certified.
I'm only trying to find where the threshold is, I don't have any favorite here. I will not ask anything anymore, my intention was not to create irritation.Quote:
Originally Posted by Flyfalcons
Point taken. I will not post any more questions. Thanks all for the feedback, I really appreciate it.
Quote:
Originally Posted by kjensen
For sure, 25-50% premium for turbine power would change the landscape. Not overnight, but it would eventually push piston engine dominance aside in light planes. None of this is going to happen without a technology breakthrough, cause regardless of the name on the dataplate, can't manufacture a turbine engine at a price that will be competitive with current piston engines.
Quote:
Originally Posted by steveinindy
Most GA flying does not make efficient use of piston engines. The average GA mission isn't about flying from point A to B on the most efficient climb/cruise/descent profile. Many times point B isn't even involved, flying is from point A to A. Sometimes people fly just to have fun with no concerns about efficiency, you know, see something on the ground so you circle around to have another look. Powering GA with turbine engines would be the greatest thing since the Wright Flyer. Unfortunately, it's not happening with current technology.
I think you're going to be sorely disappointed flying a turbine engine airplane. Fantasy land is going to meet reality head on and they are not going to be anywhere near matching up.
That would be the elusive billionaire that wants to make a small fortune in aviation......Quote:
Originally Posted by Thomas Stute
How so? It's going to be expensive, kind of boring but it is a means to get from point a to point b. But then again I feel much the same about all flying: it's stretches of boredom punctuated by a couple of minutes of challenges. Maybe it would be different if I were into aerobatics or something. There's no magic or romance or any of the other emotions a lot of people feel towards aviation. It is a scientific and engineering challenge that allows me to learn and challenge myself. A fringe benefit is that I wind up with an interesting and somewhat useful aircraft. If I do it right, this will be rather dull flying in the minds of a lot EAAers. Routine and kind of dull in aviation is a good thing in most cases. I don't have an particular illusions about it. Care to elaborateas to what you mean?Quote:
Originally Posted by martymayes
Thanks a lot for you input!Quote:
Originally Posted by martymayes
Have you seen this development? It has gone quiet for a couple of years but it is not dead. This model is "only" around 100hp but an "affordable" upscale version is not outside the realms of possibility.
What do people feel would be a price for a 150-180hp turboprop engine that would attract buyers? A new 180hp IO360 is around $32000, what do you think people would pay for a 180hp turboprop to use instead of the IO360 (up to 25% more as previously alluded to or the same price as the equivalent piston)? I'm curious what the general opinion is. The turbine would probably be 30% less efficient, but it could be a sub-120 lbs installation versus 280 lbs for the IO360. 160 lbs is a lot of weight to save on a sub-1000 lbs empty weight aircraft and would have to count for something. Sure, range is compromised due to the higher SFC of the turbine but how much would this come into consideration for someone considering such an engine?
If a turbine cost the same as the equivalent piston, I would put such an engine in my project in a flash as fuel burn doesn't really worry me. The weight saving would count for a lot for me, but what do others think?
I agree, it would be short-sighted for someone not to develop a potential family of engines from a single design. 100-400 hp and most of the GA fleet is covered. For 180 hp, 50% over 32k is $48k. All manufacturers would rush to get a turbine 4 place on the market and salivating buyers would line up to buy them.Quote:
Originally Posted by flyvulcan
do you have any more info on that?? There's no details in the youtube video, very interesting looking design though!Quote:
Originally Posted by flyvulcan
The turboprop in the video was by N2 Turbines. I had a link to their website and was going to post it but but I just visited the page, only to find that the site lapsed on 04/04/12 so is no longer available. You can find a little information about them on the web, including a second video of their engine. I can recall that either Sport Aviation or Kitplanes magazines ran an article on them a few years back.
In the 1990's United Airlines was taking deliveries of B-757 's and I had a Pratt & Whitney tech rep riding jumpseat with us on a trip. UAVMX, when he finished taking engine parameter readings I asked him the EXACT question you have raised about a 300-400 hp turbo prop we could afford in GA. His answer was as long as we machine the blades we cannot get the cost down. I asked about making ceramic blades and he said they were working on that, but I have not heard anything about it since then. Adrian BewleyQuote:
Originally Posted by uavmx
Yeah, that's obviously where the cost is tied up....not in the technology. Axial flow blades don't seem like that are all that complex to machine.....where as a blisk, or centrifugal compressor seems like it would be very difficult. But again, with all the automation today, all these CNC machines, etc, you'd think that the cost would have come down.Quote:
Originally Posted by Adrian Bewley
The outer housings are pretty basic, pressed/welded tubes essentially. I think the shafts would be expensive because of the trueness required and often times you have shafts running inside another.
I know another VERY expensive aspect to the manufacturing cost are fuel nozzles. The amount of misting/atomization required, dual flow, conical spray patterns these suckers is complex and on a TPE run around $6k A PEICE!!! (and there's 8 of them....)
There's got to be a way to attack these issues with a group of smart guys and over come these limitations.
A large chunk of cost is that you can't build turbine engine parts out of plain 'ol steel. Some high temp alloys in raw bar stock form is >$1000 per linear inch. The benefit of ceramic is that it would be cheap if they could find a way to make it work.Quote:
Originally Posted by uavmx