231 vs 201: speed at low altitude

[carusoam]

I know a resource if you want an intercooler...?

-a-

[Austintatious]

Someone mentioned Turbines...

Why ohh why isnt someone trying to figure out how to  put THIS on a Mooney.

https://pbs.cz/en/our-business/aerospace/aircraftgines/turbopropgine-pbs-tp100.

 Yea, not as much power as a rocket or Acclaim... but turbine smoothness, reliability and simplicity up to FL290

 

Plus, it is pretty light weight and would probably shed some LBS off a 6 cylinder engine setup.  Maybe 200?

250 Hp... reasonable fuel burns that wouldn't even really necessitate the long range tanks.  At 75 gallons of 100LL, A Mooney with 75 gal tanks has 435 lbs of fuel.  However if you fill those same tanks with Jet A you have 500 lbs.   That engine at 170 hp in cruise flight will burn about 150 lbs per hour (.9 lb per BHP per HR)  so with 500 lbs you have just less than 3 hours + reserves.   If you had 105g tanks that's 700lbs of fuel.which would give you a solid 4 hours + reserves.  Cost wise for the fuel, remember that jet A is a bit less spendy so fill up cost would be less.

The 310 HP turbo Moonies are definitely a bit more efficient, but Turbines are so fun.

Edited May 27, 2019 by Austintatious

[carusoam]

Because somebody did this... in 2008.

https://www.businesswire.com/news/home/20080731006257/en/Rolls-Royce-Explores-Future-RR500-Turboprop-Applications-Mooney

All it will take is a stack of money and some STC writing skills...

AKA the Rocket Engineering approach...

Best regards,

-a-

[Austintatious]

how much does the RR engine cost?

Looks good too... a bit more fuel efficient as well... although that is probably at higher power settings.. Turbines seem to go down a lot in BSFC at lower power settings.

That is a lot of power and it could get a lot of people into trouble.  The nice thing about the engine I posted is that there would not be any nasty surprises due to putting a ton of extra power onto the aircraft.  There are already mooneys with over 300 Hp on them, so a 250 HP turbopro would likely be a safe bet.

 

Some of the turbopro Lancairs have had some nasty mishaps due to the extra torque.

[Mooney in Oz]

Turbine - Simple operation, light weight and generally more reliable than pistons but can be biiiiiiiiiig $$$$$$$$'s if sudden,  unexpected (or expected) maintenance is required. 

[carusoam]

Generally speaking, turbines...

• operate most efficiently at WOT....
• Are Great for high altitude long cruises...
• wear and OH cost can be similar to an IO550, when spread over the hours used...
• incredibly expensive IF it breaks...

Selecting a smaller power plant becomes problematic for shorter fields and longer climbs...

For the Long Body, a 250hp engine would have a bit of extra T/O roll, longer than the Bravo...

 

As far as high power and it’s associated high torque goes.... tail design and pilot training are important... hard to tell what the experimental crowd does in this case...

Overpowering the tail’s ability...   probably will lead to departure from controlled flight, until the excess torque is back in control...

 

PP thoughts only, not a CFI or turbine driver...

Best regards,

-a-

 

[johncuyle]

13 minutes ago, carusoam said:

Generally speaking, turbines...

• operate most efficiently at WOT....
• Are Great for high altitude long cruises...
• wear and OH cost can be similar to an IO550, when spread over the hours used...
• incredibly expensive IF it breaks...

Selecting a smaller power plant becomes problematic for shorter fields and longer climbs...

For the Long Body, a 250hp engine would have a bit of extra T/O roll, longer than the Bravo...

 

As far as high power and it’s associated high torque goes.... tail design and pilot training are important... hard to tell what the experimental crowd does in this case...

Overpowering the tail’s ability...   probably will lead to departure from controlled flight, until the excess torque is back in control...

 

PP thoughts only, not a CFI or turbine driver...

Best regards,

-a-

 

One expects that if it is possible to shove a 300hp TSIO-520 into a mid-body (particularly the already nose-heavy K model) and end up with something that flies, shoving a lighter 250hp turboprop in would not result in something that overpowers the rudder.  If one were inclined to try a long body (like, a Bravo), the weight difference of the big bore engine and the turboprop offers an opportunity.  I looked up the weight for the TIO-540 and the first Lycoming doc that came up indicated that it's a ~600 pound engine.  That little turboprop is listed as 140 pounds.  You could reduce max gross by 400 pounds, still gain some UL, probably break even on FF payload, and probably not lose much takeoff performance.  If a 300hp version becomes available, you could boost gross back up and have a Mooney with an actually useful useful load.

[gsxrpilot]

I'll volunteer my 252 for that little 250hp turboprop.

It actually might work to stick that little engine on the nose of an RV-14. 

[jaylw314]

The Wikipedia site suggests development for the RR500 was stopped in 2012.

The suggested cruise fuel flow was 240 for pph, or about 50 gal/hour(?)  

Edited May 28, 2019 by jaylw314

[carusoam]

Compare that FF to 310hp at 27.2 gph (STC) or preferred around 29gph... extra ROP cooling for extended climb...

Not bad if your climb only lasts a few minutes.  The FF comes under control with the low density air aloft...

What TAS can we expect with that 300kts?

We need to keep an eye on Vne as well...  the Long Body has a Vne just below 200kias...

Best regards,

-a-

[Austintatious]

On 5/28/2019 at 1:22 PM, johncuyle said:

One expects that if it is possible to shove a 300hp TSIO-520 into a mid-body (particularly the already nose-heavy K model) and end up with something that flies, shoving a lighter 250hp turboprop in would not result in something that overpowers the rudder.  If one were inclined to try a long body (like, a Bravo), the weight difference of the big bore engine and the turboprop offers an opportunity.  I looked up the weight for the TIO-540 and the first Lycoming doc that came up indicated that it's a ~600 pound engine.  That little turboprop is listed as 140 pounds.  You could reduce max gross by 400 pounds, still gain some UL, probably break even on FF payload, and probably not lose much takeoff performance.  If a 300hp version becomes available, you could boost gross back up and have a Mooney with an actually useful useful load.

That is a TON of weight loss... to put it into perspective, the weight savings of 460 lbs is about 15% lighter!

The only problem I see is balance.  Certainly anything in the tail that could would need to be relocated to the nose ( batteries ECT) and even then the cowl might need to be lengthened to put that light engine further forward.

In any case, weight savings go a LOT further for aircraft performance than power increases.  A Mooney that is 400 lbs lighter with 250 Hp would likely perform pretty close to a 300 HP mooney at the heavier weight

3200 lbs /300 hp = 10.6666  lbs per HP

2740 lbs/ 250 hp = 10.96 lbs per Hp        a negligible difference of .3%

 

the whole thing makes a lot of sense to me.

 

and to reiterate ....  you would have reasonable fuel burns that wouldn't even really necessitate the long range tanks.  At 75 gallons of 100LL, A Mooney with 75 gal tanks has 435 lbs of fuel.  However if you fill those same tanks with Jet A you have 500 lbs.   That engine at 170 hp in cruise flight will burn about 150 lbs per hour (.9 lb per BHP per HR)  so with 500 lbs you have 2:45 + reserves all things being equal.   If you had 105g tanks that's 700lbs of fuel.which would give you a solid 4 hours + reserves.  Cost wise for the fuel, remember that jet A is a bit less spendy so fill up cost would be less.

 

You would DEFINITELY need to get high to get any kind of economy, which means Oxygen

Edited June 5, 2019 by Austintatious

[johncuyle]

On ‎6‎/‎5‎/‎2019 at 9:50 AM, Austintatious said:

That is a TON of weight loss... to put it into perspective, the weight savings of 460 lbs is about 15% lighter!

The only problem I see is balance.  Certainly anything in the tail that could would need to be relocated to the nose ( batteries ECT) and even then the cowl might need to be lengthened to put that light engine further forward.

In any case, weight savings go a LOT further for aircraft performance than power increases.  A Mooney that is 400 lbs lighter with 250 Hp would likely perform pretty close to a 300 HP mooney at the heavier weight

3200 lbs /300 hp = 10.6666  lbs per HP

2740 lbs/ 250 hp = 10.96 lbs per Hp        a negligible difference of .3%

 

the whole thing makes a lot of sense to me.

 

and to reiterate ....  you would have reasonable fuel burns that wouldn't even really necessitate the long range tanks.  At 75 gallons of 100LL, A Mooney with 75 gal tanks has 435 lbs of fuel.  However if you fill those same tanks with Jet A you have 500 lbs.   That engine at 170 hp in cruise flight will burn about 150 lbs per hour (.9 lb per BHP per HR)  so with 500 lbs you have 2:45 + reserves all things being equal.   If you had 105g tanks that's 700lbs of fuel.which would give you a solid 4 hours + reserves.  Cost wise for the fuel, remember that jet A is a bit less spendy so fill up cost would be less.

 

You would DEFINITELY need to get high to get any kind of economy, which means Oxygen

That fuel consumption is brutal, though.  170hp would get you, what 190 knots or so up high?  That's only 500 miles range on 70 gallons.  Even with JetA being a bit cheaper, you're still nearly doubling your fuel bill.  You're also doubling your fuel stop frequency.  This assumes there's self-serve Jet-A at your field.  I don't think my field does, so Jet-A is actually more expensive and you have to wait around for the truck.  Short hops of less than 150 miles become really painful due to being way out of the efficiency curve.  

[Austintatious]

I am not so sure you wouldn’t do 200 knots at 180 or higher.  Remember, the airplane will be quite a bit lighter.  So perhaps 550 miles?

That being said,  you are correct it would be a hit in range, absolutely.  But could still fit some typical mission profiles.

with ER tanks you are up to roughly 800 miles.   But with turbine smoothness and reliability.

[aviatoreb]

6 hours ago, Austintatious said:

I am not so sure you wouldn’t do 200 knots at 180 or higher.  Remember, the airplane will be quite a bit lighter.  So perhaps 550 miles?

That being said,  you are correct it would be a hit in range, absolutely.  But could still fit some typical mission profiles.

with ER tanks you are up to roughly 800 miles.   But with turbine smoothness and reliability.

Also it will be more aero right?  The nose will be narrower and pointier.

[Austintatious]

30 minutes ago, aviatoreb said:

Also it will be more aero right?  The nose will be narrower and pointier.

Good point, however I am not sure if that would make it more aerodynamic or not.

Certainly much smarter people than me have considered something like this. So perhaps it's non existence is an indicator there is something I dont see.

[carusoam]

Expect smooth curves that allow air to pass easily will be more aerodynamic than flat plates...

essentially air in front of a flat plate gets displaced extra inches away, costing more energy...

Really bad aero, causes eddy currents and air has to pass by or around them as well...

really goofy aero includes compressing air before it can move away... compressing air takes energy.

go with narrow and pointy when able...

Best regards,

-a-

[Tx_Aggie]

On 5/21/2019 at 8:47 PM, PT20J said:

Help me understand. The 231 has 210 max. HP and the same prop blades as the 200 HP 201. The airframes are basically the same. It would seem that up to about 8500 feet at 75% power, they should perform similarly. Above 8500', the normally aspirated 201 will lose power and slow down. The turbocharged 231 can maintain 75% power up to it's critical altitude and will pull ahead. This is just theory, not experience: It's been 30 years since I last flew a 231. Am I missing something?

Skip

Does the 201 make 75% power at 8500?  My engine monitor is from last century so it doesn’t calculate % power. I have some notes from a jpi 900 showing an ovation2 at 11,000’ making 59% power, I realize OAT would be helpful to know but didn’t get that info. 
 

By the same logic though, if a J makes 59% power at 11k, if you held the k to 75% power, your cruise tas should be far ahead of the J right? 
200 x .59 = 112 hp

210 x .75 = 157.5 hp

157/112 = 40%, so should cruise be 40% faster?! Maybe I’m improperly ratio’ing?

[Fly Boomer]

29 minutes ago, Tx_Aggie said:

157/112 = 40%, so should cruise be 40% faster?! Maybe I’m improperly ratio’ing?

I don't know what happens at very low percent power, but adding horsepower at higher speeds doesn't come anywhere near the linear relationship you are suggesting.

[EricJ]

2 minutes ago, Fly Boomer said:

I don't know what happens at very low percent power, but adding horsepower at higher speeds doesn't come anywhere near the linear relationship you are suggesting.

Yeah, it's a square relationship.   A flying airplane only has drag to overcome to convert power to speed, and the power to overcome aero drag goes up with the square of the speed.   So to double speed requires four times the power. 

[Tx_Aggie]

33 minutes ago, EricJ said:

Yeah, it's a square relationship.   A flying airplane only has drag to overcome to convert power to speed, and the power to overcome aero drag goes up with the square of the speed.   So to double speed requires four times the power. 

Do you have an equation? Engineer here, but not aerospace!

[Shadrach]

8 hours ago, Tx_Aggie said:

Does the 201 make 75% power at 8500?  My engine monitor is from last century so it doesn’t calculate % power. I have some notes from a jpi 900 showing an ovation2 at 11,000’ making 59% power, I realize OAT would be helpful to know but didn’t get that info. 
 

By the same logic though, if a J makes 59% power at 11k, if you held the k to 75% power, your cruise tas should be far ahead of the J right? 
200 x .59 = 112 hp

210 x .75 = 157.5 hp

157/112 = 40%, so should cruise be 40% faster?! Maybe I’m improperly ratio’ing?

The POH  for my F model shows max power at 7500’ at  83% and 77% at 10,000.

I have never flown a 231.  However, I did take off behind a very nice looking example last year. My box stock F model was at least 10kts faster at the same ROC.  I thought I was imagining it as he became larger in my windscreen. About that time, tower called me to verify that I still had a visual as they had gotten a collision alert. I jogged to the right and increased pitch a bit. I passed him about 6 miles from the runway and 500’ above him when he turned south at the VOR.  I have no idea what climb power setting he was using, but am sure it was conservative. K models do have more cooling drag than their normally aspirated brethren.

[PT20J]

13 minutes ago, Tx_Aggie said:

Do you have an equation? Engineer here, but not aerospace!

Look in any basic aerodynamics text. At cruise speed parasite drag predominates, so a first order approximation ignores induced drag (which will, of course, underestimate the total drag). Parasite drag increases as the square of true airspeed. Power required to overcome parasite drag varies as the cube of true airspeed.

[ArtVandelay]

I recommend this book:

“Illustrated Guide to Aerodynamics” by Hubert Smith.

[Danb]

9 hours ago, PT20J said:

Look in any basic aerodynamics text. At cruise speed parasite drag predominates, so a first order approximation ignores induced drag (which will, of course, underestimate the total drag). Parasite drag increases as the square of true airspeed. Power required to overcome parasite drag varies as the cube of true airspeed.

Huh. 

[Ricky_231]

Here's an interesting read comparing the J and the 231 K. With data!

https://web.archive.org/web/20200219184610/http://www.mooneypilots.com:80/mapalog/M20K231 Eval Files/M20K231_Eval.htm