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Post subject: Re: Low cost turbine.... Posted: 28 Jul 2022, 01:36 |
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Joined: 12/21/08 Posts: 931 Post Likes: +519 Location: Townsville (YBTL), Australia
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Quote: Uh, no, horsepower is horsepower. If both planes are making the same power at the same altitude, they’ll fly at the same speed. My science brain is telling me, " That makes no sense"!
_________________ Lee Fitzpatrick (aka Forkie!)
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Post subject: Re: Low cost turbine.... Posted: 28 Jul 2022, 08:17 |
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Joined: 04/30/09 Posts: 1517 Post Likes: +859
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Username Protected wrote: I don't think that is clear. You see an airspeed change with cowl flaps even though the cross section changes very little. It does take aerodynamic power to cool a piston engine. It is indeed a significant amount of lost energy. On the 414, I get a pitch change with the four cowl flaps opening and closing. Imagine if there was a powerplant so efficient, it required almost no cooling system? Almost no power lost to cooling drag? No Tetraethyl Lead required? No fossil fuels required?
_________________ Former Taco Chef Now - Battery Salesman No Engineering Skills I don’t know what I don’t know
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Post subject: Re: Low cost turbine.... Posted: 28 Jul 2022, 08:23 |
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Joined: 12/17/10 Posts: 1611 Post Likes: +272 Location: Valparaiso, IN
Aircraft: Lancair Evolution
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Username Protected wrote: Uh, no, horsepower is horsepower. If both planes are making the same power at the same altitude, they’ll fly at the same speed.
A nose redesign to package a turbine probably won’t buy much, as the cross-sectional area of the fuselage isn’t changing, the airframe wetted area is probably identical, and exhausting the turbine to the free stream might actually increase drag. This is not correct at all. The IO-550R conversion that is done on a Bonanza for example uses a cowl that has much smaller openings for cooling air. Typically a V-tail Bo will cruise around 170 ktas. A similarly equipped V-tail will be 15-20 ktas faster with the IO-550R setup because of the reduced drag. I have real world experience with this. I had a V-tail that I converted that flew 168 ktas before and 184 ktas after the IO-550R conversion (would have been closer to 190 ktas if I didn't have tip tanks). The IO-550R is only rated 10 hp more than the IO-550. A turbine cowl is much more streamline than a piston cowl. This article by David Rogers explains it. https://www.nar-associates.com/technica ... screen.pdf
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Post subject: Re: Low cost turbine.... Posted: 28 Jul 2022, 08:46 |
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Joined: 02/27/08 Posts: 3179 Post Likes: +1263 Location: Galveston, TX
Aircraft: Malibu PA46-310P
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Username Protected wrote: Uh, no, horsepower is horsepower. If both planes are making the same power at the same altitude, they’ll fly at the same speed.
A nose redesign to package a turbine probably won’t buy much, as the cross-sectional area of the fuselage isn’t changing, the airframe wetted area is probably identical, and exhausting the turbine to the free stream might actually increase drag. This is not correct at all. The IO-550R conversion that is done on a Bonanza for example uses a cowl that has much smaller openings for cooling air. Typically a V-tail Bo will cruise around 170 ktas. A similarly equipped V-tail will be 15-20 ktas faster with the IO-550R setup because of the reduced drag. I have real world experience with this. I had a V-tail that I converted that flew 168 ktas before and 184 ktas after the IO-550R conversion (would have been closer to 190 ktas if I didn't have tip tanks). The IO-550R is only rated 10 hp more than the IO-550. A turbine cowl is much more streamline than a piston cowl. This article by David Rogers explains it. https://www.nar-associates.com/technica ... screen.pdf
Those speeds seem off. My io520 V35B was between 170-172 knots. I thought the 550 variants easily hit 180kts. At least thats what I read on the "Should I get the 550" threads. Kevin
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Post subject: Re: Low cost turbine.... Posted: 28 Jul 2022, 09:49 |
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Joined: 12/17/10 Posts: 1611 Post Likes: +272 Location: Valparaiso, IN
Aircraft: Lancair Evolution
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Username Protected wrote: This is not correct at all. The IO-550R conversion that is done on a Bonanza for example uses a cowl that has much smaller openings for cooling air. Typically a V-tail Bo will cruise around 170 ktas. A similarly equipped V-tail will be 15-20 ktas faster with the IO-550R setup because of the reduced drag. I have real world experience with this. I had a V-tail that I converted that flew 168 ktas before and 184 ktas after the IO-550R conversion (would have been closer to 190 ktas if I didn't have tip tanks). The IO-550R is only rated 10 hp more than the IO-550. A turbine cowl is much more streamline than a piston cowl. This article by David Rogers explains it. https://www.nar-associates.com/technica ... screen.pdfThose speeds seem off. My io520 V35B was between 170-172 knots. I thought the 550 variants easily hit 180kts. At least thats what I read on the "Should I get the 550" threads. Kevin Truth be told, my plane originally had an IO-520. However, my dad's V-tail, same model as mine, no tip tanks and had IO-550B would only cruise at 168 ktas.
Your IO-520 was 4 kts faster than mine. If you don't have tip tanks, then that makes sense because I did have them. My dad's IO-550 plane had a McCauley 3-bladed prop. If he had a Hartzell he probably would have been in the 173 kts range.
The one IO-550R plane I flew in that didn't have tip tanks flew 190 ktas.
Last edited on 28 Jul 2022, 10:24, edited 4 times in total.
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Post subject: Re: Low cost turbine.... Posted: 28 Jul 2022, 10:07 |
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Joined: 08/14/13 Posts: 6074 Post Likes: +4651
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Username Protected wrote: Those speeds seem off. My io520 V35B was between 170-172 knots. I thought the 550 variants easily hit 180kts. At least thats what I read on the "Should I get the 550" threads. Kevin 6% more displacement gives you ~5% more speed? Fascinating departure from reality id wager
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Post subject: Re: Low cost turbine.... Posted: 28 Jul 2022, 10:59 |
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Joined: 01/06/08 Posts: 4702 Post Likes: +2705
Aircraft: B55 P2
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Comparing airspeeds between different planes is not easy. ASIs are not all that well calibrated - the two on my plane disagree by ~3 knots at 160 IAS. Then some tachs are not well calibrated so one person may be at 2500 rpms, the other at 2550. Rigging can be different. Different antennas, engine baffles. Some cowl flaps don't close completely.
Then of course updrafts can make a big difference in cruise speed. Unless the air is very smooth its not uncommon to see a few knots variation. (and most pilots tend to notice the high numbers).
It is possible to do a careful measurement, but most people are too lazy to actually do it (myself included)
All that said, having ownd a IO520 baron and a IO550 baron with similar weights, the 550 performance advantage (climb and cruise) "seems" substantially more than the difference in displacement would imply.
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Post subject: Re: Low cost turbine.... Posted: 28 Jul 2022, 14:28 |
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Joined: 12/17/10 Posts: 1611 Post Likes: +272 Location: Valparaiso, IN
Aircraft: Lancair Evolution
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Username Protected wrote: Comparing airspeeds between different planes is not easy. ASIs are not all that well calibrated - the two on my plane disagree by ~3 knots at 160 IAS. Then some tachs are not well calibrated so one person may be at 2500 rpms, the other at 2550. Rigging can be different. Different antennas, engine baffles. Some cowl flaps don't close completely.
Then of course updrafts can make a big difference in cruise speed. Unless the air is very smooth its not uncommon to see a few knots variation. (and most pilots tend to notice the high numbers).
It is possible to do a careful measurement, but most people are too lazy to actually do it (myself included)
All that said, having ownd a IO520 baron and a IO550 baron with similar weights, the 550 performance advantage (climb and cruise) "seems" substantially more than the difference in displacement would imply. Yes this is all very true. That's why I don't compare airspeeds on planes I fly unless I do GPS testing. Fly a box and find the true TAS.
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Post subject: Re: Low cost turbine.... Posted: 28 Jul 2022, 16:04 |
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Joined: 12/24/18 Posts: 486 Post Likes: +484 Location: KHFD
Aircraft: F33A
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Username Protected wrote: Uh, no, horsepower is horsepower. If both planes are making the same power at the same altitude, they’ll fly at the same speed.
A nose redesign to package a turbine probably won’t buy much, as the cross-sectional area of the fuselage isn’t changing, the airframe wetted area is probably identical, and exhausting the turbine to the free stream might actually increase drag. Two words: "cooling drag". A significant amount of power is being used to push air through the piston engine for cooling. That is why some setups have cowl flaps, to reduce that drag. The turbine also has jet thrust. Typically, this is about 10% of the power output, so the effective horsepower is 10% larger when the shaft horsepower is the same. For any given shaft horsepower, the turbine airplane has much lower drag and higher effective output power. Mike C. In theory you are all correct - however, I've been on the design end of this problem, and it doesn't buy much. Yes, a turboprop adds some jet exhaust (assuming you can duct it properly), but the re-packaging of the nose isn't going to get you as much as you think. The extended length required for the turboprop and exhaust will increaser fineness ratio of the airframe, but you'll still have a very similar installation as the reduction gearbox (on either a PT6,TPE331, or Allison 250) is in the same cross-sectional ballpark (vertically) as a IO-550 (horizontally). And yes, cooling drag might be lower if the inlet is properly tailored, but you still need airflow around the turboprop to ensure radiant heat doesn't cook the harnesses, coke the fuel lines, and destroy the sensors.
Oh, and Roy Lopresti did some great work on Mooneys, mostly cleaning up the sloppiness in the original design. Not a lot of magic - just attention to detail.
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Post subject: Re: Low cost turbine.... Posted: 29 Jul 2022, 09:18 |
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Joined: 12/17/10 Posts: 1611 Post Likes: +272 Location: Valparaiso, IN
Aircraft: Lancair Evolution
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Username Protected wrote: In theory you are all correct - however, I've been on the design end of this problem, and it doesn't buy much. Yes, a turboprop adds some jet exhaust (assuming you can duct it properly), but the re-packaging of the nose isn't going to get you as much as you think. The extended length required for the turboprop and exhaust will increaser fineness ratio of the airframe, but you'll still have a very similar installation as the reduction gearbox (on either a PT6,TPE331, or Allison 250) is in the same cross-sectional ballpark (vertically) as a IO-550 (horizontally). And yes, cooling drag might be lower if the inlet is properly tailored, but you still need airflow around the turboprop to ensure radiant heat doesn't cook the harnesses, coke the fuel lines, and destroy the sensors.
Oh, and Roy Lopresti did some great work on Mooneys, mostly cleaning up the sloppiness in the original design. Not a lot of magic - just attention to detail. What I know from my experience with the Evolution was that it is quite easy to predict what your TAS will be based on the HP you are producing (within a given rage). They had tried to install a piston on the Evo and had estimates on speeds for that as well. Those estimates fell short. It was explained to me that it was due to the extra drag of the larger nose to fit the piston, since everything else was equal. Would you suggest something different? If I remember correctly they said the piston Evo was going to cruise at 260-270 ktas and the real world speeds were under 240 ktas.
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Post subject: Re: Low cost turbine.... Posted: 29 Jul 2022, 09:56 |
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Joined: 08/12/08 Posts: 7429 Post Likes: +2256 Company: Retired Location: Santa Barbara, CA
Aircraft: '76 A36 TAT TN 550
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Username Protected wrote: The one IO-550R plane I flew in that didn't have tip tanks flew 190 ktas. A V35 with an IO-520 (if memory serves) has a book cruise speed of 176 knots. Throw in an IO-550 and I think that goes to 180 KTAS. My experience with Beech products tells me book airspeeds can often be exceeded (and they can be flown at lighter than gross weight which also helps them go faster). My IA has a V35 on which he routinely sees 184 KTAS. So could an IO-550R see 190 KTAS? I think it’s possible. But I don’t feel as though it is a massive improvement over what a well rigged V35 can do with an IO-550B. For the extra cost I’d rather have a TAT TN vs the 550-R. With a TAT TN 550 in my A36 we see 185 KTAS all day every day at 12,000’. If we go higher we get an easy 195 KTAS at 17,000’ on 15.x GPH. With any kind of tailwind we’re well over 200 knots groundspeed. I saw 247 knots going east earlier this year. It makes a big difference when you’re going from CA to FL.
_________________ ABS Life Member
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Post subject: Re: Low cost turbine.... Posted: 29 Jul 2022, 10:09 |
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Joined: 12/17/10 Posts: 1611 Post Likes: +272 Location: Valparaiso, IN
Aircraft: Lancair Evolution
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Username Protected wrote: The one IO-550R plane I flew in that didn't have tip tanks flew 190 ktas. A V35 with an IO-520 (if memory serves) has a book cruise speed of 176 knots. Throw in an IO-550 and I think that goes to 180 KTAS. My experience with Beech products tells me book airspeeds can often be exceeded (and they can be flown at lighter than gross weight which also helps them go faster). My IA has a V35 on which he routinely sees 184 KTAS. So could an IO-550R see 190 KTAS? I think it’s possible. But I don’t feel as though it is a massive improvement over what a well rigged V35 can do with an IO-550B. For the extra cost I’d rather have a TAT TN vs the 550-R. With a TAT TN 550 in my A36 we see 185 KTAS all day every day at 12,000’. If we go higher we get an easy 195 KTAS at 17,000’ on 15.x GPH. With any kind of tailwind we’re well over 200 knots groundspeed. I saw 247 knots going east earlier this year. It makes a big difference when you’re going from CA to FL. As I said, the V35 that we owned with an IO-550B flies 168 ktas.
As far as the IO-550R plane flying 190 ktas. It does. I flew it. It was impressive how fast it climbed and how fast it flew at 10k.
I have heard there are some IO-550R planes that fly over 200 ktas. Perhaps they found someone that is good with rigging like you mentioned for IO-550B planes. Don't know.
The other benefit of the IO-550R setup vs the IO-550B as well as a TN plane is that you have much cooler cylinder head temps and have a longer TBO.
The A36 with the IO-550R flies 185 ktas with no tip tanks. (At least that is what is reported, I have not flown in one)
IO-550B overhaul schedule is 1700 hours IO-550R overhaul schedule is 2000 hours
The IO-550R conversion also moves your CG forward a couple inches.
I have also heard that at overhaul of the IO-550R that there is less wear and tear.
Last edited on 29 Jul 2022, 11:58, edited 1 time in total.
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Post subject: Re: Low cost turbine.... Posted: 29 Jul 2022, 11:27 |
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Joined: 08/22/12 Posts: 523 Post Likes: +281
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This is the first I've heard of the IO-550R. I'm intrigued. When our IO-550B needs overhaul I may consider this option. What does the package cost to do?
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Post subject: Re: Low cost turbine.... Posted: 29 Jul 2022, 11:56 |
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Joined: 12/17/10 Posts: 1611 Post Likes: +272 Location: Valparaiso, IN
Aircraft: Lancair Evolution
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Username Protected wrote: This is the first I've heard of the IO-550R. I'm intrigued. When our IO-550B needs overhaul I may consider this option. What does the package cost to do? It's EXPENSIVE. Worth it IMO if you plan to keep the plane, but it costs $170,000 right now. The reason it's so expensive is because you get an entire new front end. Engine, cowling (upper and lower), lighting, prop, etc. I forgot to mention that it moves your CG forward some too. Pretty much the same amount adding a TN does. It used to be done by Atlantic Aero but it was bought by Summit Aviation. The guy that I bought mine from is still working there. His name is John Ackerman. Great guy. https://summitaviationmfg.com/io550/
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