Raptor Composite Aircraft

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by Dexacare, Mar 28, 2016.

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  1. Aug 1, 2019 #1121

    Venom

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    What you say is true. ANY federal, or state aviation grants compel the airport owner to operate without deference. In this particular case the city was not in receipt of any outside funding. I would guess that Cherokee County airport DOES accept grant money. Time will tell.
     
    Last edited: Aug 1, 2019
  2. Aug 1, 2019 #1122

    rv6ejguy

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    You may have missed the part that with full fuel, the aircraft is at gross weight with nobody aboard...

    With the 62 inch wide fuselage, no way this is going to true 230 knots on 7 gph (132hp roughly) either. My guess would be about 13-16 GPH.
     
  3. Aug 1, 2019 #1123

    Doggzilla

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    Remember it’s a diesel and it should be able to hold 75% speed at 50% throttle.

    I have a 455hp diesel and during a 55mph windstorm in South Dakota I had to hold the pedal to the floor just to keep 60mph while towing 44,000lbs.

    It got 4.5mpg after several hours of full throttle in those conditions. With a notoriously inefficient DEF system installed as well.

    That’s roughly 13gph at full throttle with a 455.

    I would be surprised if it didn’t break 2000 miles. And likely 1500 with two people.

    Regardless of if his frame succeeds, the engine will likely be worth the effort. The only reason the 172 diesel failed was because the 2008 recession.
     
  4. Aug 1, 2019 #1124

    mcrae0104

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    What BSFC does that work out to, and how does that compare to other diesels?
     
  5. Aug 1, 2019 #1125

    BJC

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    The Glasair Aviation Diesel Sportsman 2+2, at half the cost (or less) of the 172 diesel, out performs the Cessna in all categories.

    It was introduces ca. 2015, but has had very few sales during a time when gasoline TWTT sales have been at full capacity.

    There are more factors at play in the selection of an engine, especially for E-AB aircraft, than the 2008 economy.


    BJC
     
  6. Aug 1, 2019 #1126

    jedi

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    Sportsman Diesel is a great airplane with two or three problems.

    First, most Sportsman owners want the big engine. The Cessna is the Chevrolet sedan. The Sportsman is the GTO. My son still has not forgiven me for getting the Tempest instead of the GTO. He doesn't agree that my fuel savings put him through college.

    Second, cost. Not just purchase price but the 1,000 hour TBO with the requirement to return the engine and purchase a new one.

    Third, and a minor reason, the typical use of the Sprotsman is to many airports that do not have Jet A.

    Fourth: After the first preflight it was clear that if this was my airplane I would always smell like Jet A. In some circles that might be considered a plus but I do not agree.

    PS: The Factory Diesel has been sitting without an engine for a year or so.

    For what it is worth. A Diesel Sportsman is on my "I want that list". A gas Sportsman is not.
     
    Last edited: Aug 1, 2019
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  7. Aug 1, 2019 #1127

    rv6ejguy

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    I used .35 which is about what the Austro and Conti aero diesels deliver in cruise. I don't expect the Audi will be any better at the relatively high rpms it will be running in this application. My guess is that Raptor would require at least 250-300hp to do these speeds at FL250 with that huge fuselage and likely high cooling drag.
     
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  8. Aug 1, 2019 #1128

    Doggzilla

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    Yes, because that’s a kit plane that is flown rarely, not a production training aircraft where fuel usage is a primary concern. Nobody is going to pay an extra $30,000 for something they won’t use and can’t maintain at rural airports. It’s not for pleasure aircraft. It’s for business.

    Thielert actually went bankrupt but was saved by the Chinese in 2013. They couldn’t sell engines if they were basically out of business for several years.

    The customers who were lucky enough to get them have been raving about them.
     
  9. Aug 1, 2019 #1129

    rv6ejguy

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    I'm not sure what your first sentence means. An airplane will require X hp to cruise at X speed at X altitude. Throttle position is not very relevant. Fuel required to move the aircraft at X speed is determined by X hp times the BSFC. Applies to Diesel or SI engines equally.

    The 3500 mile range would require about 700 pounds of fuel at Peter's projected fuel burn. That puts the aircraft over gross weight with no people aboard- not very useful.

    At the likely fuel burn, range would be about 1500-1700 miles, still requiring that same 700 pounds of fuel so you still couldn't even take the pilot on that trip-again not useful.

    Now let's take 500 pounds of people (3). That leaves 200 pounds for fuel. Range is likely to be less than 500 miles. Carry 4 people at 600 pounds and range drops to 230 miles roughly.

    The airframe and the engine will both not work as envisioned for the many technical reasons we've discussed in this thread.

    Other aero diesels don't make economic sense in North America while we still have cheap avgas and diesels costing at least twice as much initially. Nothing to do with with 2008, everything to do with economic reality.
     
  10. Aug 1, 2019 #1130

    Doggzilla

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    That’s how fuel burn is judged in the POH for most piston aircraft and taught in university ground school. Almost every POH has that kind of information included.

    For a given altitude and air density reducing the fuel flow to 50% will usually maintain 70-80% of top speed.

    For instance, a Cessna 172 operating at 50% of its maximum fuel burn of 13gph will cruise at 95kts, which is 75% of its top speed of 126kts.

    This gives a substantially higher range than advertised, being able to break 800 mile with standard 2x26 gallon tanks if you can stand 8+ hours in such a cramped space.
     
    Last edited: Aug 1, 2019
  11. Aug 1, 2019 #1131

    Doggzilla

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    And no, they do not cost twice as much initially. The price increase on most production aircraft is 12-20%. But at a savings of no less than $48,000 per 2000 hours, PER ENGINE they save noticeable amounts for schools and busy Bush aircraft businesses.

    For air businesses that operate over 1000 hours per year the aircraft can pay for themselves in 5-10 years. Especially those operating twins.
     
    Last edited: Aug 1, 2019
  12. Aug 1, 2019 #1132

    Scheny

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    The horsepower is torque multiplied by speed. Unless you rev it at super high rpm, you will never have the full power and therefore consumption.

    I have flown both the Thielert and the Austro in the Diamond DA-42. If you exchange the 180hp Lycoming for a 135hp Diesel, you will save around a third per engine (40l/h down to 27l/h), have the same take-off run but cruise faster at 10k feet due to the turbo... All these although the plane gets way heavier due to an extra 100kg for the engine and heavier gear, but they increase take-off weight, so it doesn't matter.

    The Thielert had bad reliability, until they changed from 1.7l to 2 0l engine blocks. RPM is reduced to 3300, compared to 4500 in the car. Many pilots also complained about redundancy. ECU has a "hot standby" (second already running and ready to take over), but some pilots missed redundant injectors... Not me, it would continue to run on 3 cylinders and also some gas engines don't run without power. Only problem I ever experienced was a prop that never unfeathered and therefore started again during a training. Uses an oil accumulator which failed. We switched training to simulated OEI afterwards.

    The only real problem was the lifetime of the gear with 300 hours.

    Diamond aircraft took over when Thielert was not an option and created the Austro. This has better gear and turbo and true double redundant ECU. While the gear was not long time proven in the beginning, they provided coupons for a free service (Peter could offer free couplers). Also power was wayyyyy better. At 170hp instead of the previous 135hp the speed went up from a former 130kt at 70% to around 150kt at 55%. Climb power is only possible in still air, as it would accelerate to red speed. On the ground you couldn't even test the ECU anymore if not doing it symmetrically on both engines, as the plane would spin in circles. For the new DA-62 they increased power again, being in the range of almost 200hp now. Whatever Peter does, my 100 hours on Diesel planes tell me that anything above 250hp on the Audi engine will let it fail within short time.
     
  13. Aug 1, 2019 #1133

    BJC

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    Yup, lots of reasons. Why don’t you make Glasair a lowball offer? Might make then happier than just having the engine sit unused.


    BJC
     
  14. Aug 1, 2019 #1134

    Doggzilla

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    The 455 is at 1500rpms, which is normal operating range while towing 44,000lbs.

    And the Audi engine is designed for significantly higher performance than the Benz engines. One is for a economy car and the other is for a performance car.
     
  15. Aug 1, 2019 #1135

    jedi

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    I think the engine has found a new purpose. Good Idea though. I may look into that. I was planning on a different Diesel.
     
  16. Aug 1, 2019 #1136

    rv6ejguy

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    Many folks don't cruise their Lycs ROP over here these days so let's compare apples and apples in cruise.

    40L/hr. is about 10.5 US gal./hr. LOP gives you around 32L/hr. LOP with EFI and EI gives you around 28-29 in the Experimental world.
     
  17. Aug 1, 2019 #1137

    Doggzilla

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    That is a twin. That’s 20 per engine.

    All of the “new” tech in gasoline engines is based off of diesel tech, it’s literally copied specifically because diesels are so much more efficient.

    An 80,000lb commercial diesel truck gets 6.5mpg fully loaded at 65mpg, which is like a 3500lb car getting 148mpg.

    Commercial diesel technology leaves gasoline in the dust.
     
  18. Aug 1, 2019 #1138

    BJC

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    Are you suggesting that comparative fuel efficiency between two engines is a function of the gross weight of the driven vehicle?


    BJC
     
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  19. Aug 1, 2019 #1139

    BoKu

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    When operated at near constant speed on level ground.

    I can see that for a car with the same ratio of Cd to mass. As long as it's operated at a constant speed on level ground.
     
  20. Aug 1, 2019 #1140

    rv6ejguy

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    From Avweb, where they did a detailed operating cost analysis on the AE300 to Lyc IO-360 in the North American market- "The last analysis I did on the Austro AE300 against a Lycoming IO-360 yielded a $53.53 per hour cost for the Austro-inclusive of fuel-versus $66.50 for the Lycoming, not including any mid-run cylinder overhauls or typical mag work.That’s good, but not necessarily slam dunk if the diesel is more expensive to buy."

    Once you figure in the $30K price premium of the AE300, that changes the figure to $68.53 over 2000 hours so it doesn't save any money, certainly not so if you invest that initial $30K saved for a few years.

    This comparison was for flight schools where the Lyc is operated ROP. In cruise if operated LOP, the comparison ends up a wash in per hour costs between the 2 engine types, again not taking into account the much higher initial acquisition costs of the diesel.

    Truth is, something like a Conti IO-550 operating LOP with variable ignition advance rather than fixed timing mags can do better than .37 BSFC- which is within spitting distance of the aero diesel designs we currently have.

    If you look at the top mileage, non-hybrid cars right now, many have SI engines.
     
    Last edited: Aug 2, 2019
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