INA201 Posted December 1, 2018 Report Share Posted December 1, 2018 I did a test flight a week ago just to see how my plane performs. Here is the info for you guys. I am not sure the exact % power but here is the data for some discussion. 1978 J 900 Hours since OH with a Donaldson air filter, inner gear doors, no step 6500 ft @ 13 degrees C 24"MP(Full Throttle) 2500RPM 10GPH Highest CHT #4@365 Lowest CHT #2@345 Highest EGT#3@1477 Lowest EGT #2@1429 North 156 East 168 West 144 South 154 Average 155.5 knots My guess is I could get 160 knots if I pushed up the RPM and ran some more fuel through. I may give it a try sometime. Quote Link to comment Share on other sites More sharing options...
Shadrach Posted December 1, 2018 Report Share Posted December 1, 2018 Seems like a reasonable number. Next time try doing the 3 legs separated by 90° And plug in to the linked calculator. http://www.csgnetwork.com/tasgpscalc.html Quote Link to comment Share on other sites More sharing options...
carusoam Posted December 1, 2018 Report Share Posted December 1, 2018 To complete the discussion... it helps to state... 1) °F LOP or ROP.... or at peak... 2) To Get %bhp... it helps to have the FF (10gph) you were using and the calculation (multiplier) If you were LOP... for %bhp ROP There is a key number that can be used... key numbers are plane specific and are MP+ RPM/100... Nice data either way! I get 165 kts for a few gph more, LOP... Best regards, -a- 1 Quote Link to comment Share on other sites More sharing options...
INA201 Posted December 1, 2018 Author Report Share Posted December 1, 2018 9 hours ago, carusoam said: To complete the discussion... it helps to state... 1) °F LOP or ROP.... or at peak... 2) To Get %bhp... it helps to have the FF (10gph) you were using and the calculation (multiplier) If you were LOP... for %bhp ROP There is a key number that can be used... key numbers are plane specific and are MP+ RPM/100... Nice data either way! I get 165 kts for a few gph more, LOP... Best regards, -a- Yeah, I’ll do the three way next time. Also, I just leaned to 10gph and didn’t pay attention to LOP or ROP. I’ll try again with a couple of different scenarios. To be continued Quote Link to comment Share on other sites More sharing options...
Bob - S50 Posted December 1, 2018 Report Share Posted December 1, 2018 I applaud you for doing flight testing rather than just boring holes in the sky on the way to a $200 hamburger (inflation). One of the items on my list of testing in the near future is to make a small wooden "key" that shows mixture knob position for target EGT at 2000', 4000', 6000', and 8000'. I can then use that key to set my mixture for a rough hack on where it should be for takeoff from a high altitude airport. Now, back to your topic... I've found that if I run LOP I get 145 KIAS at 10 GPH (75%), 135 KIAS at 9 GPH (67%), and 125 KIAS at 8 GPH (60%). Running barely LOP I can only get 10 GPH up to about 6500' or so because I run at 2600 RPM. If I ran at 2500 RPM that altitude would be lower and if I ran at 2700 RPM it would be higher. I can get 9 GPH up to about 10,000' or so at 2600 RPM. Since TAS is about 1.5% higher than IAS for every 1000' of altitude that would give me about (1 + (6.5 x .015)) x 145 = (about) 159 KTAS at 6500' That's why I like 8500' westbound and 9500' eastbound for long flights (over 300 NM). I get a pretty nice TAS on less than 75% power. I'm losing power at a rate of about 3% for every 1000' I climb, but my TAS vs IAS is increasing by about 1.5% at the same time so I'm only losing a little TAS while my FF is going down. For example (1 + (8.5 x .015)) x 135 = (about) 152 KTAS on 9 GPH westbound, and (1 + (9.5 x .015)) x 135 = (about) 154 KTAS on 9 GPH eastbound. That's only about 5 - 7 KTAS slower on a gallon/hour less fuel flow. In reality I use full throttle and see FF around 9.2 to 9.5 GPH and about 157 or 158 KTAS at 8500/9500. And now derailing a bit off topic again... I also pick my RPM based on TAS. I found an article by Dr. Rogers about prop efficiency and based on the assumptions he used, and the formulas he provides, for our relatively short 74" prop it appears that the most efficient prop speed for 160 KTAS is about 2600 RPM. At 150 KTAS it is about 2500 RPM and at 140 KTAS it is about 2400 RPM. Since I try to cruise around 155 to 160 KTAS on long legs I would want about 2550 to 2600 RPM. The ironic thing is, at altitude, if my TAS is lower and I reduce the RPM by 100, that reduces my potential power by about 4% which makes me go slower. If I then reduce RPM for the new slower speed, it again reduces my power which reduces my speed which reduces my desired RPM which.... So I just leave it at 2600 RPM and take what I can get. 1 Quote Link to comment Share on other sites More sharing options...
amillet Posted December 1, 2018 Report Share Posted December 1, 2018 Having some weight in the baggage compartment improves cruise speed by several knots. I’ve started leaving the 30 lb. emergency kit back there. The extra weight is more than offset by the rearward CG shift. 4 1 Quote Link to comment Share on other sites More sharing options...
INA201 Posted December 1, 2018 Author Report Share Posted December 1, 2018 2 hours ago, Bob - S50 said: I applaud you for doing flight testing rather than just boring holes in the sky on the way to a $200 hamburger (inflation). One of the items on my list of testing in the near future is to make a small wooden "key" that shows mixture knob position for target EGT at 2000', 4000', 6000', and 8000'. I can then use that key to set my mixture for a rough hack on where it should be for takeoff from a high altitude airport. Now, back to your topic... I've found that if I run LOP I get 145 KIAS at 10 GPH (75%), 135 KIAS at 9 GPH (67%), and 125 KIAS at 8 GPH (60%). Running barely LOP I can only get 10 GPH up to about 6500' or so because I run at 2600 RPM. If I ran at 2500 RPM that altitude would be lower and if I ran at 2700 RPM it would be higher. I can get 9 GPH up to about 10,000' or so at 2600 RPM. Since TAS is about 1.5% higher than IAS for every 1000' of altitude that would give me about (1 + (6.5 x .015)) x 145 = (about) 159 KTAS at 6500' That's why I like 8500' westbound and 9500' eastbound for long flights (over 300 NM). I get a pretty nice TAS on less than 75% power. I'm losing power at a rate of about 3% for every 1000' I climb, but my TAS vs IAS is increasing by about 1.5% at the same time so I'm only losing a little TAS while my FF is going down. For example (1 + (8.5 x .015)) x 135 = (about) 152 KTAS on 9 GPH westbound, and (1 + (9.5 x .015)) x 135 = (about) 154 KTAS on 9 GPH eastbound. That's only about 5 - 7 KTAS slower on a gallon/hour less fuel flow. In reality I use full throttle and see FF around 9.2 to 9.5 GPH and about 157 or 158 KTAS at 8500/9500. And now derailing a bit off topic again... I also pick my RPM based on TAS. I found an article by Dr. Rogers about prop efficiency and based on the assumptions he used, and the formulas he provides, for our relatively short 74" prop it appears that the most efficient prop speed for 160 KTAS is about 2600 RPM. At 150 KTAS it is about 2500 RPM and at 140 KTAS it is about 2400 RPM. Since I try to cruise around 155 to 160 KTAS on long legs I would want about 2550 to 2600 RPM. The ironic thing is, at altitude, if my TAS is lower and I reduce the RPM by 100, that reduces my potential power by about 4% which makes me go slower. If I then reduce RPM for the new slower speed, it again reduces my power which reduces my speed which reduces my desired RPM which.... So I just leave it at 2600 RPM and take what I can get. Wow! Nice information here. Assuming full throttle@6500 feet and 2500RPM I leaned to 10gph on that one flight. I just looked at it as 10GPH vs LOP or ROP. I guess my question is, should I run tests at peak or slightly ROP(25 degrees or so) and slightly LOP allowing the fuel flow to be what it is and try 2600RPM instead? My guess is setting mixture based on fuel flow alone is not the best way to do it and will possibly lead to combustion inefficiency. Quote Link to comment Share on other sites More sharing options...
Ragsf15e Posted December 2, 2018 Report Share Posted December 2, 2018 9 hours ago, INA201 said: Wow! Nice information here. Assuming full throttle@6500 feet and 2500RPM I leaned to 10gph on that one flight. I just looked at it as 10GPH vs LOP or ROP. I guess my question is, should I run tests at peak or slightly ROP(25 degrees or so) and slightly LOP allowing the fuel flow to be what it is and try 2600RPM instead? My guess is setting mixture based on fuel flow alone is not the best way to do it and will possibly lead to combustion inefficiency. You’ll get lots of advice on LOP and ROP. Plenty of other threads to read too. However, I’d caution you on just setting a fuel flow without knowing where you are ROP, Peak or LOP. Probably should be somewhere around 90ish ROP, 20 or more LOP (depending on altitude) or Peak maybe if you’re real high. It’s pretty difficult to detonate an IO360 at 6,500’, but possible, especially lower. It’s also just a bad habit to set mixture half hazardly when you’ve apparently got egt info from all 4 cylinders. 25ROP is not a great place to operate the engine for efficiency, speed or longevity. Im definitely not trying to sound like a jerk or condescending, just trying to make us all better... and you beat me too... I did very similar speed testing last weekend in my M20F. 90 ROP, 10.2gph, 145 kts, 10300’ density alt. 136 knots at same altitude 20LOP. Js are nice! 2 Quote Link to comment Share on other sites More sharing options...
gsxrpilot Posted December 2, 2018 Report Share Posted December 2, 2018 https://drive.google.com/drive/folders/1BmxtvTtWAWXTqEkQ6lsq0t94zcQl0km7?usp=sharing I kinda do this performance recording on many flights by taking a quick pic that records all the data. So for any of you flying M20K's, there's a lot of performance data in that folder. 2 Quote Link to comment Share on other sites More sharing options...
carusoam Posted December 2, 2018 Report Share Posted December 2, 2018 An explanation of why setting 10gph works for some, but not for others... you want to prove this works on your engine before setting and forgetting... Using the FF method is great, when you have defined where peak is in your plane at a particular group of settings...MP/RPM/OAT/Altitude... Some people do this, and then short-cut to a particular FF... while keeping everything constant as before... Short-cutting to a particular fuel flow based on somebody else’s plane might cause you a problem that you may not recognize for a while... especially when getting outside the standard atmospheric conditions... There are a few things to avoid when using the red knob... known as the redbox around here... the redfin around other places... Either way, the red box has a limit at 65%bhp... in a NA IO360 being above 8k’, the %bhp is limited by MP... So.... you are free to lean anyway you like when generating less than 65%bhp... Because you are outside the redbox! The next limitation is the CHTs you get with your choice of leaning... 380°F is a number people use to avoid high cylinder wear... really important anywhere near the redbox... Also keep in mind people like to avoid 50° ROP because it is associated with the highest ICPs... (internal cylinder pressures)... Take a look at the power charts in your POH... %bhp should be clearly written in there with MP/RPM/ALT references.... It will be plane/engine combination specific.... Power charts are known to not tell the whole truth... especially when giving data at 50°F ROP... Often people will cruise at 100°F ROP to be kinder and gentler to their engine while making out the output... for a few bucks more in gas... Experiment with your leaning procedure... depending on the knobs you have in the cockpit... you can roughly lean to peak based on FF data... then finish finding peak twisting the mixture knob slowly, while the EGTs react.... Keep in mind, not everyone is using fast acting EGTsensors, or their engine monitor may not be quick on the display... PP thoughts only, trying to promote good engine monitoring ideas... I may miss a few points every now and then... Don’t forget to look outside... or have somebody fly with you... while you experiment... Best regards, -a- 2 Quote Link to comment Share on other sites More sharing options...
Mooney-Mark Posted December 2, 2018 Report Share Posted December 2, 2018 5 hours ago, gsxrpilot said: https://drive.google.com/drive/folders/1BmxtvTtWAWXTqEkQ6lsq0t94zcQl0km7?usp=sharing I kinda do this performance recording on many flights by taking a quick pic that records all the data. So for any of you flying M20K's, there's a lot of performance data in that folder. Great looking glass cockpit! 1 Quote Link to comment Share on other sites More sharing options...
Bob - S50 Posted December 2, 2018 Report Share Posted December 2, 2018 On 12/1/2018 at 10:28 AM, INA201 said: Wow! Nice information here. Assuming full throttle@6500 feet and 2500RPM I leaned to 10gph on that one flight. I just looked at it as 10GPH vs LOP or ROP. I guess my question is, should I run tests at peak or slightly ROP(25 degrees or so) and slightly LOP allowing the fuel flow to be what it is and try 2600RPM instead? My guess is setting mixture based on fuel flow alone is not the best way to do it and will possibly lead to combustion inefficiency. Correct. Just setting a fuel flow doesn't tell you much. You could be LOP or ROP. Personally I set my power by starting with the ROP settings MP+RPM/100 = 50 for 75%, 47 for 65%, 44 for 55%. I then lean to LOP, close the cowl flaps and make a slight adjustment in the throttle to get the equivalent LOP fuel flow: 10 gph = 75%, 8.7 gph = 65% and 7.4 gph = 55%. In reality, down low I'll set 22", then reduce to 2600 RPM (which brings the MP up to about 23") and then lean to LOP. This usually gives me a fuel flow around 9.5 gph. Up high I'll use WOT, 2600 RPM and just LOP. 75% = 75% = 75%. It doesn't matter how you get there, the speed will be the same. You can do it 100 ROP or you can do it LOP. However, for any given RPM, when LOP it will take more MP than it will when ROP to get the same power. For that reason, you can get 75% (or any power percentage for that matter) at a higher altitude when you run ROP than you can when LOP. So for maximum speed pick the altitude that lets you get the desired percentage of power when 100 ROP. However, being a CSOB, I use LOP and accept slightly lower speeds for significantly less cost. Same for RPM. The higher the RPM, the higher to possible power available. It's up to you to decide how high you want the RPM. I'm probably in the minority by cruising at 2600 RPM. Most people probably use 2500 or less. 3 Quote Link to comment Share on other sites More sharing options...
carusoam Posted December 2, 2018 Report Share Posted December 2, 2018 Ina, You are going to see a few people don’t guess or assume when setting power settings... Then there are a few people that will use the lean til rough, then enrichen til smooth or by X°F... I use Bob’s approach above because... fuel costs motivate a lot of learning... as do cylinder costs... You might find that each time you set the mixture, you might choose a different objective... 1) Start-up... hot vs cold... 2) Taxi... Avoiding lead deposition... 3) T/O... maximizing power vs altitude above SL... EGT method. 4) Climb... maximizing power during a continuous change of MP.... not maximum FF... 5) Cruise... Maximizing efficiency while keeping cool CHTs. LOP uses all the fuel to produce power. 6) Descent... controlling air speed in an increasing MP environment while adjusting mixture... 7) Landing... Setting mixture for the Go Around... 8) Taxi... again... 9) Shutdown... Last mixture adjustment, eyes on the tach looking for the rpm rise prior to engine cut.... Look at this as several ways to save a few dollars each flight and for the long haul... fuel, maintenance, wear.... It gets easier with time. Lots of flights are to the same altitude, same loading, lots of same..... kind of like using the same WnB data that you have generated for going to grandma’s house every month... What motivates you? What tools do you have to achieve your goals? PP thoughts only, not a CFI or mechanic... Best regards, -a- 1 Quote Link to comment Share on other sites More sharing options...
AH-1 Cobra Pilot Posted December 2, 2018 Report Share Posted December 2, 2018 On 11/30/2018 at 9:55 PM, INA201 said: My guess is I could get 160 knots if I pushed up the RPM and ran some more fuel through. Theoretically, you cannot. Going from 2500 rpm to 2700 rpm will result in a TAS of 159.9 kts and fuel flow of 10.8 gph. (All else being equal.) What really surprises me is the difference in your EGT. I usually get a maximum of about 1430 with those conditions. Quote Link to comment Share on other sites More sharing options...
INA201 Posted December 3, 2018 Author Report Share Posted December 3, 2018 Good advice, you guys are on it. I'm starting to learn and practice with the JPI900. Hopefully I can get out and do some more data mining tomorrow. Might as well add the weight to the baggage compartment too and see what transpires. Quote Link to comment Share on other sites More sharing options...
carusoam Posted December 3, 2018 Report Share Posted December 3, 2018 Get out your WnB app... load your data exactingly... and experiment moving the CG back, slowly, stepwise... No need to rush to the back of the envelope and find out you mis calculated or assumed something incorrectly.... Make sure your weight is tied down... no sense in having you get whacked in the back of the head by it... For most effect, use the lightest weight as far back as legally possible... (hat shelf, or more permanently...Charlie weight stack?) Post your WnB graphs to compare with other people... Of course, this isn’t magic if you do WnB all the time, or doing statics calculations is the norm for you... PP thinking out loud, not a CFI... Best regards, -a- 1 Quote Link to comment Share on other sites More sharing options...
Oldguy Posted December 3, 2018 Report Share Posted December 3, 2018 One easy way to check your weight would be to look at your elevator while flying your legs. Any significant deflection of it would tend to indicate drag you might minimize by changing CG. 1 Quote Link to comment Share on other sites More sharing options...
superfly1 Posted December 3, 2018 Report Share Posted December 3, 2018 Can anyone provide any input on a 231 Turbo Performance? I just purchased an M20k 231. Great flying machine, but a lot going on in the cockpit. She's loaded out with all the bells and whistles but curious as to MP at or around 11,500. If my MP is set to 30MP and my Dif Temp is -55, should I run at 27MP? How low can one go on the MP before it's "too cold" or is there such a thing.......? Quote Link to comment Share on other sites More sharing options...
INA201 Posted December 3, 2018 Author Report Share Posted December 3, 2018 Went up today. I made sure to be level and stable before taking any numbers. The average speed running close to 83 ROP 11.4 GPH 6500 feet 2600 ROM 11deg OAT WOT NSEW 23.7MP with 35 pounds of weight in the baggage compartment was 162.5 knots. Same altitude 13 LOP 9.2GPH 23.6MP everything else the same yielded 155.75knots. This is roughly the same as my original post with 10GPH fuel flow. My conclusion is that the rear weight contributed to a couple of knots. Interestingly, using 2600 RPM also added to the numbers for sure. I attached some pics of the LOP and ROP settings. Any advice or comments would be really appreciated. I’m new to the engine management game. Quote Link to comment Share on other sites More sharing options...
Ragsf15e Posted December 4, 2018 Report Share Posted December 4, 2018 (edited) Those numbers seem about right. Next thing would be to do same thing around 9,500’ just to get an idea how altitude will affect both. At some point less than 65% power you may want to run closer to peak egt when LOP but there’s probably gonna be debate on that. Just make sure all 4 are past peak. Higher up you’ll find even better miles/gallon, but at a slightly slower airspeed. Rop, you’re in a good place. Probably don’t wanna get any leaner there. Remember, all the settings are dependent on altitude, temp, etc. you now have an idea of ff, but best to use the lean function on the jpi to set it each time in cruise. You should figure out how to download your data and use jpi’s software to analyze the leaning. It will give your gami spread. Lop, #4 is farther lop, but that isn’t necessarily indicative of a bad gami spread. I also use the normalize mode after leaning as it will quickly show an egt walk off if you have an exhaust valve issue. Edited December 4, 2018 by Ragsf15e 1 Quote Link to comment Share on other sites More sharing options...
Ragsf15e Posted December 4, 2018 Report Share Posted December 4, 2018 Also note generally cooler CHT temps LOP. It wasn’t bad for ROP, but cooler is generally better for longevity. For that OAT, your temps look reasonable. Nice avionics btw! 1 Quote Link to comment Share on other sites More sharing options...
carusoam Posted December 4, 2018 Report Share Posted December 4, 2018 3 hours ago, superfly1 said: Can anyone provide any input on a 231 Turbo Performance? I just purchased an M20k 231. Great flying machine, but a lot going on in the cockpit. She's loaded out with all the bells and whistles but curious as to MP at or around 11,500. If my MP is set to 30MP and my Dif Temp is -55, should I run at 27MP? How low can one go on the MP before it's "too cold" or is there such a thing.......? Search for the words Transition Training... Mooney Specific CFII... There isn’t a better traveling Mooney out there. It deserves to be fully familiar with before running into challenges... For real interesting reading there are actually a couple of threads dedicated M20K operations... Enjoy the new 2U bird. Best regards, -a- Quote Link to comment Share on other sites More sharing options...
Bob - S50 Posted December 4, 2018 Report Share Posted December 4, 2018 6 hours ago, INA201 said: Went up today. I made sure to be level and stable before taking any numbers. The average speed running close to 83 ROP 11.4 GPH 6500 feet 2600 ROM 11deg OAT WOT NSEW 23.7MP with 35 pounds of weight in the baggage compartment was 162.5 knots. Same altitude 13 LOP 9.2GPH 23.6MP everything else the same yielded 155.75knots. This is roughly the same as my original post with 10GPH fuel flow. My conclusion is that the rear weight contributed to a couple of knots. Interestingly, using 2600 RPM also added to the numbers for sure. I attached some pics of the LOP and ROP settings. Any advice or comments would be really appreciated. I’m new to the engine management game. Theoretically, 2600 RPM vs 2500 RPM will give you about 4% more power and thus maybe 1 or 2% more speed. That would be an extra 1.5 to 3 knots because of the higher RPM. While an aft CG will allow you to go a little faster, I doubt it would make more than 1 or 2 knots difference. It has also been my experience that it is easier for me to keep my #3 CHT below 400F when I'm operating at 2600 RPM vs 2500 RPM even though I'm making more power. According to my POH, a 440# difference in weight (2740 vs 2300) only makes a 3 knot difference in cruise speed. There is only an 8.3" difference in forward and aft CG limits but the tail is probably 15 feet aft of the CG. At max weight, 2740 lbs x 8.3" = 1895'# pitching moment difference. Divide that by 15' and you get a 126# difference in tail download and an equal decrease in wing loading. While there may also be a little better streamlining, that's less than 1/3 of the weight difference from the POH. So 1/3 of a 3 knot difference is only about 1 knot. Now if you reduce your weight by the 440# AND you have that CG at the aft limit, it could make about a 4 knot difference between that and full weight at forward CG. 2 Quote Link to comment Share on other sites More sharing options...
Ragsf15e Posted December 4, 2018 Report Share Posted December 4, 2018 (edited) 14 hours ago, Bob - S50 said: Theoretically, 2600 RPM vs 2500 RPM will give you about 4% more power and thus maybe 1 or 2% more speed. That would be an extra 1.5 to 3 knots because of the higher RPM. While an aft CG will allow you to go a little faster, I doubt it would make more than 1 or 2 knots difference. It has also been my experience that it is easier for me to keep my #3 CHT below 400F when I'm operating at 2600 RPM vs 2500 RPM even though I'm making more power. According to my POH, a 440# difference in weight (2740 vs 2300) only makes a 3 knot difference in cruise speed. There is only an 8.3" difference in forward and aft CG limits but the tail is probably 15 feet aft of the CG. At max weight, 2740 lbs x 8.3" = 1895'# pitching moment difference. Divide that by 15' and you get a 126# difference in tail download and an equal decrease in wing loading. While there may also be a little better streamlining, that's less than 1/3 of the weight difference from the POH. So 1/3 of a 3 knot difference is only about 1 knot. Now if you reduce your weight by the 440# AND you have that CG at the aft limit, it could make about a 4 knot difference between that and full weight at forward CG. Interesting thought on the aft CG aerodynamics. I have always understood the benefits of an aft CG to be from reducing the amount of negative lift that the tail has to generate to hold the nose up and thus reducing drag created by the horizontal stabilizer. It’s not the weight reduction, but the reduction of induced drag created by the tail that results in slightly better airspeed. At our cruise speed, any reduction in drag will have a larger effect than increase in power (percentage drag vs percentage power). And maybe that’s what you meant too as wing loading/weight is going to directly affect lift required and therefore drag... I buy the ~3 knots between max gross and very light weight and have seen about that pretty consistently. I think I’ve got more like 2-3 knots out of an aft CG though. I will need more data to back that up. Edited December 4, 2018 by Ragsf15e 1 Quote Link to comment Share on other sites More sharing options...
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