P

prkaye

Well Known Member
What (ballpark) is your speed for best range? I did a bit of testing this morning to explore mine. It seems to be quite a bit slower than I expected. I have a -9A with an O-320 / FP prop. I calculate my range values as IAS (kts) by GPH, giving a number in nm/gal. At 135kts (leaned-out) I get about 17nm/gal. If I slow way down to 105kts, it goes up significantly to about 21nm/gal. I still have to do way more data collection, and try even slower speeds, but it seems that if I want to my x-country flying as cheaply as possible, I need to fly really slow :(
What have other folks found?
 
Speed cost money
Click to expand...

Not necessarily. In a car, your best mpg is achieved typically between 90 and 100km/hr. If you go more slowly in a car, you actually get worse range. I know airplanes are different, I was just a bit surprised that the most economical speed seems to be so down the range of flyable speeds.
 
Should be doing better than this

You need to use true airspeed Phil.

I've been flying my '9 since 2004 and can reliably reproduce the following two cruise conditions.

8000' density altitude (or there abouts) Wide open throttle, 2500 rpm, leaned (but rich of peak for the carb) produces 164 knots true on 8 gallons per hour for 20.5 nm/gallon.

2000' - 3000' density altitude, 22 inches 2200 rpm, leaned produces 130 knots on 6 gallons per hour or 21.67 nm/gallon.

Even better would be go up to 10000' - 12000' or so and lean it back. That'll be really efficient

BETTER THAN MY TRUCK!




prkaye said:
What (ballpark) is your speed for best range? I did a bit of testing this morning to explore mine. It seems to be quite a bit slower than I expected. I have a -9A with an O-320 / FP prop. I calculate my range values as IAS (kts) by GPH, giving a number in nm/gal. At 135kts (leaned-out) I get about 17nm/gal. If I slow way down to 105kts, it goes up significantly to about 21nm/gal. I still have to do way more data collection, and try even slower speeds, but it seems that if I want to my x-country flying as cheaply as possible, I need to fly really slow :(
What have other folks found?
Click to expand...
 
Phil,

Your numbers don't seem quite right to me. I have a 9A also, FP O320 and here are some rough numbers I typically get.

%Power. TAS mph. GPH. MPG
75. 180. 8. 22.5
65. 170. 7. 24.3
55. 160. 6. 26.7

These numbers are not exact but fairly close and I use them for planning purposes and bragging. You should probably be using TAS rather than IAS in your calculations. Also, if you do not have all your fairings and pants on (wheel pants that is), you numbers will be much worse.
 
IIRC, according to Max Conrad, low and slow is the key to max range.

Just as best L/D gives you best "glide distance", so to will it provide best range with the engine running.
 
What instruments do you have in your panel? How are you calculating your fuel burn? Have you calibrated your instruments? If not, are you sure your readings are accurate?

I ask because I would like to know some of these speeds, readings, etc. on my airplane but am not sure I am ready to calculate them yet. I am flying behind the GRT HX display with the GRT EIS4000 for engine monitoring. I have 26 hours on my airplane but am not ready to start on things like best economy cruise or other such measurements yet because I am still trying to calibrate the fuel flow and fuel quantity readings on my instruments. I also have not made any determination as to whether my air speed readings are accurate or not.

I want to make sure the instruments I have are informing me of the actual readings before I start relying on them to make determinations on best economical speed, etc.
 
hmmm... not sure why my numbers are so much lower. I do have my pants and fairings on.
I have a Dynon and a steam airspeed indicator, both agree within about 2kts.
Fuel flow from Red Cube through Dynon.
I was at about 3600' densisty altitude. Any ideas why my numbers might appear so much worse?
 
prkaye said:
hmmm... not sure why my numbers are so much lower. I do have my pants and fairings on.
I have a Dynon and a steam airspeed indicator, both agree within about 2kts.
Fuel flow from Red Cube through Dynon.
I was at about 3600' densisty altitude. Any ideas why my numbers might appear so much worse?
Click to expand...

Phil,

Yours seems pretty close to mine. I too hear about folks getting 6gh at 140kts and wonder how that's happening. I cruise at 2500 RPM 140 KTAS, leaned (not LOP) and burn about 7.5gph or so. I haven't calibrated my Red Cube and it still is set to 68k. I did test on the way back from SD and found that I was reading high by 7%. I am going to start dialing in my fuel flow to see if the number come down.
 
I have a 9A/320/FP and my numbers are similar to 647jc with 140-150mph yielding almost 30 mpg. I do have electronic ignition, and that brought the mpg up quite a bit. Also, I pull carb heat and find sweet spots where I can lean LOP. Pulling CH can make a real difference, at least in my plane. That levels the EGTs to all being nearly equal. At these mileages, I find no reason to ever slow below the 150 mphTAS mark, except out sightseeing.

Bob Kelly
 
" If I slow way down to 105kts, " :eek:
Please don't do that.. I'll bet you would be the butt of all jokes when a 172 passes you at cruise.
 
The numbers I quoted earlier are for typical X country cruise between 5500 and 9500 MSL leaned out on the rich side of peak. I have also calibrated my Dynon fuel flow transducer (old style) and it is very accurate now. Originally the K factor was 29410 according to the tag provided with the transducer but after keeping accurate records of fuel usage over 80 hours of flight time, I recalculated the K factor to be 32173 which I have been using for the past 90 hours and it is very accurate. I think the original K factor caused the fuel flow readings to be much higher than they really were but I am not positive about that.

Note: The percentage of power readings I quoted earlier were taken from my Dynon EMS and I'm not sure how accurate those numbers are, I think they are fairly close. I also have plain Slick mags, no electronic ignition.
 
Last edited:
I did some checks on this when I first got the -6A. Now I just fly. About 2550 RPM (FP prop) and leaned out. I get what I get. No way will I slow down to well below 150 knots to gain a few more MPG.
 
Ok, it sounds like I need to do two things to find out if I'm actually slow:

1) start looking at TAS (shown on my Dynon) instead of IAS.
2) start testing at higher altitudes (today I was under 4000ft DAlt).

Question: Roughly how much does TAS differ with altitude for a typical RV? Will TAS be significantly greater at 8,000ft than at 4,000ft?
 
Last edited:
prkaye said:
Ok, it sounds like I need to do two things to find out if I'm actually slow:

1) start looking at TAS (shown on my Dynon) instead of IAS.
2) start testing at higher altitudes (today I was under 4000ft DAlt).

Question: Roughly how much does TAS differ with altitude for a typical RV? Will TAS be significantly greater at 8,000ft than at 4,000ft?
Click to expand...
One rule-of-thumb is to multiply IAS by 2% per thousand feet, but all you really need is an altimeter, temperature and an E6B or equivalent, to figure it out. Yes there is a very significant difference between 8,000 ft and 4,000 ft.

Oh, and the aircraft type has nothing to do with it.
 
One rule-of-thumb is to multiply IAS by 2% per thousand feet... ...Oh, and the aircraft type has nothing to do with it.
Click to expand...
Yes, I know that rule for converting IAS to TAS, but you misinterpreted my question. For a given power setting, IAS will decrease with altitude (as air density decreases). The difference between TAS and IAS increases with altitude, according to the rule you quoted. What I actually want to know is how much the actual TAS at a given fixed power setting (say at full power) changes with altitude. In other words, how does the true top speed change with altitude? Engine HP will be smaller, but the density of air to push the airplane through will be smaller as well, so it's not clear how the overall true top-speed changes with altitude.
Put simply, my question could be stated as follows: For level flight with WOT, how will the TAS vary at different altitudes? How significant should the effect be?

And yes, this would certainly depend on aircraft type.
 
Last edited:
Here is the data for my plane:

N66AP%20fuel%20burn%20vs%20airspeed%20chart.JPG


While there is a lot of noise in this data, it appears that mine does the best mileage at around 110 - 120 knots TAS. The actual mileage is very sensitive to leaning, and I did not spend a lot of time getting the mixture the same for each setting, hence the noise.

Regarding the earlier post about best mpg for cars, my experience is that it is around the 35 mph speed. I've owned a number of cars with real time mpg computers in them, and the mpg drops quite rapidly with speed (as one would expect - drag "power" is a function of the speed cubed). In what is now called a large car, it is not hard to get 35 to 40 mpg at 35 mph, while getting only 24 mpg at 60 mph. If one is in high gear in both cases, the pistons will go up and down the same number of times per mile at either speed, but they need more gas to push harder.
 
It takes O2 . . .

. . . to use this profile from my DUATS account :D

Climb: 110ktas; 10gph; 500fpm
Cruise:159ktas; 5.9gph; 17,500ft
Descent: 170ktas; 7gph; 500fpm

This profile is repeatable in my RV-6: IO-360 (parallel valves); Gamis; Lightspeed III; 9.2:1 c/r; Sensenich 72fm pitched at 85". In cruise flight, the prop is spinning at 2575rpm and the mixture is >10deg. lop.

This profile yields about 27 nmpg. By using the Hotel Whiskey auxillary fuel tanks, the aircraft's no-wind range is over 1100 nm with vfr reserves. Just remember to bring over 7 hours of O2!
 
Last edited:
Phil,

There seem to be a number of variables at play here that make apples to apples comparisons difficult. Your numbers do sound low, but using TAS will make a difference and altitude will make a difference in both fuel flow and TAS. Another issue is statute versus nautical...some are using NM, and some are using SM...and the SMPG number will always look bigger, just as MPH looks faster than KTS. But some here have given NMPG (and Pete, man can you lean!!) Just don't forget to convert if you are comparing to a MPH result.

First TAS:

For your scenario, 135 KIAS at 4K is 143 KTAS (at ISA), so your up to almost 18 nmpg off the bat...still low, right? If its ISA +20 (summer day), your KTAS is 148, and you're over 18.5...still low.

Next KTS vs MPH:

Converting the above results to MPH/SMPG, you get:
ISA = TAS 164 MPH = 20.5 SMPG
ISA +20 = 170 MPH = 21.3 SMPG

Still too low, right?

Now start climbing.

In planning for Airventure Cup, several of us used a loss of speed (due to loss of HP in the climb) of 1 knot per 1000' of climb (I think that is the answer to the question you were asking). I think that is conservative, as I don't think I actually lose quite that much. Granted I'm doing max speed tests, and am pushing a lot of air with my hershey bars, but my testing and racing have shown an average of 214 KTAS at SL down to about 205 KTAS at 17,500 (9 knots per 17K feet, or a little over .5 knot per 1K. Those are many different flights on different days, and temps varied, so its way into ball-parking...so I stick with 1 kt per 1K' for estimates.

My testing on fuel flow versus altitude is also WOT/2700 RPM, leaning for 100 ROP (mostly up high...I lean gingerly at high power at low alt...if at all...I'm running hard in these tests). Not sure if it would relate to LOP ops closely or not, but what I've found is that my FF at those settings drops 1 gph per 2,000 feet of climb, or .5 gph per 1000'. Its pretty linear too, as far as I can tell. My guess is that the change per 1000' at LOP ops would be somewhat less.

Say you climbed from 4K to 8K. If you leaned to LOP at each altitude, the difference may or may not be 2 gph (my gradient above). But if it was close, and you were running 6 gph at 8K, but you lost 2 kts due to the climb, that 135 KIAS would be 151 KTAS (ISA), and your NMPG would be a tad over 25 NMPG...getting better!!

OK, there are a LOT of assumptions, rules of thumb and SWAGs in there, and testing is really the only way to see for sure. The more X-Cs you take as you stretch your legs, the more you will be able to sit in cruise and play with this.

It would be interesting to hear from you as you record results, and to hear from others on airspeed loss gradients in climbs and fuel flow decrease gradients in climbs. I think Web Willmott did some work on this a while back, but haven't heard from him lately...Web, you out there?

Finally, on the discussion of best range speed. Take a look at this article on "Maximum Endurance, Maximum Range, and Optimum Cruise Speeds" by an RV-6 pilot. The gist is that:

Max Range occurs at minimum drag (L/D max = Best Glide Speed)
Max Endurance occurs at minimum HP required (Best Glide Speed / 1.316)
Optimum Cruise Speed occurs at minimum fuel flow per knot (Best Glide Speed X 1.316)

The article goes into the math, shows the graphs and discusses it in much greater detail, and calls the Optimum Cruise Speed "Carson's Speed"...never heard that before tonight (in this thread and in the article).

For me Max Range would be 87 KTS, Max Endurance would be 66 KTS, and Optimum Cruise Speed would be 114 KTS. Not gonna do that, though..."Speed Costs, How Fast Do You Want To Go" is a good axiom, but so is "Time is Money"...I want to get there! ;)

If you have to stay airborne to let that fog lift, fly Max End (or use the RV speed to fly to a VFR airport!). If you want to stretch that flight to the limts of range to make the island, fly Max Range (a little faster in a headwind, a little slower in a tailwind...another rule of thumb...there is another article showing that and comparing Max R and Max E here).

Good luck in your testing...have fun!!

Whoa...that was longer than I intended...hope it adds value! :eek:

Cheers,
Bob
 
Thanks Bob! Great post. My question about loss of TAS with altitude is now answered. I also corresponded directly with Kevin Horton, who has studied this in depth. Sounds like the gist of it is that the loss in engine power as you go to higher altitudes is not enough to make up for the reduced drag, so there is a loss in the WOT max TAS as you go up (as you indicate in your post, Bob). I have a FP prop which makes the situation fairly complex because the RPM for a fixed power setting will change with altitude. Basically, however, for a fixed percent power (e.g. 75% power), TAS increases with altitude, up to the maximum altitude at which one can generate 75% power. I assume that the fuel flow to generate 75% power remains relatively constant (i.e. you add throttle but can lean more to maintain 75% power as you climb, assuming these roughly cancel-out in the fuel consumption), which means you'll use less fuel to maintain a given speed at altitude. Does this seem correct?
I'll have to do testing to determine how high up I can generate 75% power. Next time we have a clear day (we've been envoloped in cloud for a couple of weeks) here I'm going to take her up to 8000ft (i haven't been anywhere close to that high yet) and see if I can produce Vans' cruise performance. I will post my results when I get them.
Question - for an O-320 FP, what generally should I expect for the highest density altitude at which my engine can produce 75% power?
 
Last edited:
2 steps forward, 3 steps back

Bob indicates that for his aircraft, Carson's Speed is 114kias. The high altitude profile that I outlined above produces 117kias. So, that high altitude profile is actually much closer to Carson's Speed than the speed for best range, the topic of this thread. Oh, well. I'll never be a test pilot :eek:

I think about it this way: true airspeed increases by roughly 2% per thousand feet of increased altitude; but, horsepower decreases by about 3% per thousand feet of increased altitude.
 
Go high for range

If you want to maximize range (irrespective of wind, which is another issue) go high. For increased range you need to power down the engine and burn less fuel. Instead of pulling the knob back, leave it wide open and climb up to 10k or more and let the diminishing air pressure throttle the motor back, plus you'll get the increase in true airspeed.

Theres nothing magic about trying to make 75 percent power except that its the point at which Lycoming says we can lean agressively and run continuously. But if you really want to mazimize range, you'll want to run much less power. Remember that airspeed goes up (and down) to the CUBE ROOT of power. So if you reduce the power, you lose speed but your fuel burn goes down much faster than the airspeed does.

Assuming you don't have a wind issue, you would probably want to climb really high. (might be prop limitations, only way to know is to test it)

If I remember correctly the last time I took the '9 up to 12500' or so it was down to around 57-58 percent power and about 6.6 gallons per hour, but was flying at 155 Ktas. Thats well over 23 nm/gallon.

Just out of curiosity, does your airplane make Vans book numbers at 8000', wide open, 75% etc... Just wondering if maybe you haven't got it faired completely or something.


prkaye said:
Thanks Bob! Great post. My question about loss of TAS with altitude is now answered. I also corresponded directly with Kevin Horton, who has studied this in depth. Sounds like the gist of it is that the loss in engine power as you go to higher altitudes is not enough to make up for the reduced drag, so there is a loss in the WOT max TAS as you go up (as you indicate in your post, Bob). I have a FP prop which makes the situation fairly complex because the RPM for a fixed power setting will change with altitude. Basically, however, for a fixed percent power (e.g. 75% power), TAS increases with altitude, up to the maximum altitude at which one can generate 75% power. I assume that the fuel flow to generate 75% power remains relatively constant (i.e. you add throttle but can lean more to maintain 75% power as you climb, assuming these roughly cancel-out in the fuel consumption), which means you'll use less fuel to maintain a given speed at altitude. Does this seem correct?
I'll have to do testing to determine how high up I can generate 75% power. Next time we have a clear day (we've been envoloped in cloud for a couple of weeks) here I'm going to take her up to 8000ft (i haven't been anywhere close to that high yet) and see if I can produce Vans' cruise performance. I will post my results when I get them.
Question - for an O-320 FP, what generally should I expect for the highest density altitude at which my engine can produce 75% power?
Click to expand...
 
I did some testing back in 2005 with the Subby and found BEST RANGE was a function of power down to a point. That point was power at 5.1 GPH. I believe the same applies with a Lycoming. I have not done the test with the 0360 but will get around to it one of these days. It is interesting stuff. With a FP prop, the point of getting behind the power curve will be different as WOT will not be possible except for the first reading.


At 12,500', OAT 53?F, WOT.

RPM 2600
BURN = 10.1
TAS = 148 KTS (170 MPH)
MPG = 16.83 (Still Air)

RPM 2500
BURN = 9.3
TAS = 146 (168)
MPG = 18.06

RPM 2400
BURN = 8.5
TAS = 144 (166)
MPG = 19.52

RPM 2300
BURN = 7.8
TAS = 140 (161)
MPG = 20.64

RPM 2200
BURN = 7.1
TAS = 135 (156)
MPG = 21.97

RPM 2100
BURN = 6.8
TAS = 133 (152)
MPG = 22.35

RPM 2000
BURN = 6.0
TAS = 127 (146)
MPG = 24.33

RPM 1900
BURN = 5.5
TAS = 125 (144)
MPG = 26.18

RPM 1800
BURN = 5.1
TAS = 122 (141)
MPG = 27.64

RPM 1700
BURN = 4.9
TAS = 114 (132)
MPG = 26.93

It would appear we are behind the power curve at 12.5 @ 1700, speed started to drop off relative to burn. *1800 RPM is a best at this altitude for economy.
 
Just out of curiosity, does your airplane make Vans book numbers at 8000', wide open, 75% etc...
Click to expand...

As I mentioned, I haven't yet had it anywhere near 8000ft, and I've been looking at IAS, not TAS. Next clear day I can get up, I'll check to see if I'm in the ballpark for Vans' numbers.
 
-9A Performance.

Wow, lots of good info in the thread!

IAS is meaningless because of all the variables the result in TAS, which is the true "constant". Yes, TAS increases with altitude at the same power setting.

If your EFIS doesn't have a %power table, for a fixed pitch prop, you should find 75% power at about 8,000 ft and Full throttle (should result in 2700 rpm.)

Although I have a CS prop, you might find helpful numbers in the performance table I generated here:

http://www.mykitlog.com/users/display_log.php?user=n539rv&project=161&category=0&log=111111&row=3

Good luck and have fun!
 
This morning I took it up to 8K and collected True Airspeed numbers. Unfortunately, for 75% power at 8000ft I'm still about 10knots lower than Vans' numbers. Even at WOT at 8000ft (78% power), I'm still about 6knots below Vans' 75% number. I have a Catto 3-blade prop, so my theory is that the difference in prop between my aircraft and Vans accounts for some of the performance difference. The rest is probably due to Vans having done a better job with getting their fairings and pants installed with greater accuracy. I had to estimate OAT (my dynon probe was reading high on the ground, so I made a guess and reduced it). Anyway, I think I can live with the numbers:

DAlt=8000ft, leaned to peak or just ROP.

%Pwr , RPM , KTAS , GPH , NM/GAL
78 , 2700 , 156 , 8.8 , 18
74 , 2550 , 152 , 8.0 , 19
64 , 2430 , 141 , 7.0 , 20
58 , 2360 , 134 , 6.5 , 20.6
33 , 1940 , 106 , 4.0 , 26.5
 
Last edited:
prkaye said:
This morning I took it up to 8K and collected True Airspeed numbers. Unfortunately, for 75% power at 8000ft I'm still about 10knots lower than Vans' numbers. Even at WOT at 8000ft (78% power), I'm still about 6knots below Vans' 75% number. I have a Catto 3-blade prop, so my theory is that the difference in prop between my aircraft and Vans accounts for some of the performance difference. The rest is probably due to Vans having done a better job with getting their fairings and pants installed with greater accuracy. I had to estimate OAT (my dynon probe was reading high on the ground, so I made a guess and reduced it). Anyway, I think I can live with the numbers:

DAlt=8000ft, leaned to peak or just ROP.

%Pwr , RPM , KTAS , GPH , NM/GAL
78 , 2700 , 156 , 8.8 , 18
74 , 2550 , 152 , 8.0 , 19
64 , 2430 , 141 , 7.0 , 20
58 , 2360 , 134 , 6.5 , 20.6
33 , 1940 , 106 , 4.0 , 26.5
Click to expand...

Leaned to peak or just ROP would not be producing your best power for 75% at 8,000ft DA. I assume the 75% figure from Vans would be at best power. From memory you would need to be about 150 degrees ROP for best power and this should give you a higher TAS. I suggest you use the spreadsheet from NTPS to accurately calculate your TAS http://www.ntps.edu/information/downloads click on GPS PEC Spreadsheet (MS Excell).
Using the spreadsheet and leaned to best power I got 169, 170 and 171 kts TAS over 3 test flights on different days (8,500ft DA, 2,700 rpm and WOT).

Fin
9A
0-320, Hartzell, 9:1 CR, mag and one LS Plasma III
 
Last edited:
Phil,
Just to add to my post # 29. I had a look at the CAFE 9A numbers and your 8,000ft DA ,2700 rpm, peak EGT, WOT, TAS of 156 kts is similar to the CAFE figure of 155 kts (2,600 rpm and 8,500ft DA with a lean mixture). However your FF at 8.8 g/h is higher than the CAFE figure of 6.1 g/h.

Fin
9A
 
Last edited:
Thansk Fin. That is a big discrepancy in FF for that configuration. Was CAFE using a CS prop? Of course it's possible my fuel flow sender is not well calibrated.
 
Let me echo Fin...

...are you SURE your indicated (hence calculated TAS) airspeeds are correct? I bring this up because I have had to do some modifications to get things close. I have a pitot tube with the static source in it and it was WAY OFF. One of the reality checks I was proposing to do was to fly next to an aircraft with a known, good airspeed system and compare. Come to find out that there are a number of folks with the "standard" Vans static source (pop rivet head in plans location) that symply rely on the IAS and simply know the indicated numbers for stalls etc. That's all they care about. When I was proposing this test, my friend actually did a data run and asked for the spreadsheet. It turns out that there are still significant errors even when done according to plans.

These errors can really throw a monkey wrench into trying to get "real" (calibrated) numbers rather than "indicated" numbers.

Also, definitely check the fuel flow. Fill the tanks to an easily-matched-when-refueling level. Take off on one tank, get established, switch tanks, do the testing and record all of the numbers, switch back to the takeoff tank. I find it easier to have one tank for getting there and back and the other for the test series. I've found that operation of my boost pump (FI system) alters the fuel flow readings so leaving the boost pump operations to the non-test tank eliminates that as a data problem.

Just sharing the pain:eek: !

Jeremy
 
...are you SURE your indicated (hence calculated TAS) airspeeds are correct?
Click to expand...
Not totally sure, no, but I did do a quick sanity check against GS with a GPS. I flew at a fixed airspeed (152 KTAS) in two reciprocal headings. The average of the ground speeds indicated by my GPS for the two reciprocal headings was within a couple of knots of my airspeed of 152KTAS, so I'd say it's probably pretty close.
 
Fin, I have to question the 6.1 GPH value for WOT at 8500' Personally I would not be aggressive leaning at that power setting.
 
prkaye said:
Thansk Fin. That is a big discrepancy in FF for that configuration. Was CAFE using a CS prop? Of course it's possible my fuel flow sender is not well calibrated.
Click to expand...
Phil,
CAFE flew the Vans factory 9A and I think it had the MT C/S prop at the time. I know CAFE conducts accurate testing but I have difficulty believing they measured 155 kts TAS at 8,500ft DA with 2,600 rpm and only 6.1 g/h. See page 12 http://cafefoundation.org/v2/research_aprs.php. Pete Howell has done a lot of testing with carb heat, LOP etc and about the best practical economy cruise both he and I can get is around 150 kts for 6 g/h at similar heights. Mind you, I ain't complaining. This is good fuel economy at a reasonable speed..


Ron Lee said:
Fin, I have to question the 6.1 GPH value for WOT at 8500' Personally I would not be aggressive leaning at that power setting.
Click to expand...
Ron,
This is how CAFE flew it (see above link page 12) and personally I see no problem with these settings. According to Lycomings graph; "Part Throttle Fuel Consumption for the injected I0-320 D series (page 3-22 of my Lycoming Operators Manual), CAFEs setting of 2,600 rpm, 6.1 g/h at Best Economy (peak EGT) would give give 73 hp or about 46% power which is well under the limit for aggressive leaning (Lycoming 75% power limit, most other experts 60 to 65% limit). My normal economy cruise is 2,250 rpm at about 6 g/h leaned to around peak which gives about 49% power for around 149/150 kts TAS at 8,500 ft.

Fin
9A
0-320
 
Last edited:
Just Like Fin......

Fin Speaks the truth. I run WOT/2250rpm/6gph/partial carb heat - that will always get me 149-151 KTAS at 8K - It is my target cruise when the skies and winds are favorable.

I have never been able to get the CAFE #'s of the factory 9A. Just like Fin, Not complaining at all.

Hartzell/carb/EMAG/PMAG -

Pete Howell has done a lot of testing with carb heat, LOP etc and about the best practical economy cruise both he and I can get is around 150 kts for 6 g/h at similar heights. Mind you, I ain't complaining. This is good fuel economy at a reasonable speed..
 
Hey Pete (just a reminder, my name is "Phil" , not "Paul" ;) ), i remember being in your -9A and being amazed by how it basically launched off the runway. Mine doesn't do that. Also your cruise fuel consumption and speed is far better than mine. I attribute almost all of this to the CS prop vs my FP Catto prop. My prop runs nice and smooth, and i have loads of ground clearance, but I sure underestimated what a difference in performance a CS would have made! Too late now, my engine was set-up for a FP. Anyway, it's probably time for me to stop obsessing about my aircraft's performance and go enjoy it! I'll just be sure never to challenge you to a race, Pete!
 
Sorry Phil!

I am talking with a "Paul" on another issue and slipped!

They are all great planes - just different - Your is simpler for maint, cost less and weighs less - that makes me envious. I don't race anyway - there is always someone faster.

I spend lots of time tooling around at 125 knots. It is great fun!

BTW - your paint job is great!
 
prkaye said:
Hey Pete (just a reminder, my name is "Phil" , not "Paul" ;)
Click to expand...
Do you get that a lot. I know I goofed on that. It's funny because forever people have called me "Phil", and I would always correct them, now I have given up.
 
Toobuilder said:
What is your concern with aggressive leaning at 8,500 feet? Just curious.
Click to expand...

Ignorance possibly. I just wait until I am well below 75% power (say 65% or so) to lean near peak/lean of peak.

I went back and did see that Fin posted that it was a 9A. I did not read that or connect that it was a 320 versus 360 Lycoming.

Plus I seldom fly as low as 8500'
 
Ron Lee said:
Ignorance possibly. I just wait until I am well below 75% power (say 65% or so) to lean near peak/lean of peak...
Click to expand...

Fair enough, but at 8,500, you are below 75% power even at WOT and 2700 RPM . In this case (75% and under), Lycoming even approves leaning to and running "AT" peak for economy. Since "peak" is... well, peak, this condition must be considered the MOST aggressive condition. Further leaning reduces temperature and cylinder pressure, so there is really nothing you can do with the mixture to get "too aggressive". If you do, the engine simply quits from fuel starvation.

If anyone has any data to contradict the above, I'd sure like to hear about it, because I quit worrying about damage from aggressive leaning a long time ago.
 
You must log in or register to reply here.