Is my Mooney slow?

[ArtVandelay]

Some numbers I see on the internet I’ve come to think that IAS must mean Internet Airspeed, because my J can’t get there.

Don’t get confused, some use mph, some knots…and those of us who live in the warmer and humid climates are losing horsepower. I gain 5-7 knots when I fly to northern states.

[Ragsf15e]

4 minutes ago, ArtVandelay said:

Don’t get confused, some use mph, some knots…and those of us who live in the warmer and humid climates are losing horsepower. I gain 5-7 knots when I fly to northern states.

I agree about the temp making a big difference, but i think it’s pretty similar in the summer.  Of course it depends on exactly where you are, but summer temps aloft are relatively similar.  The winter ones have much more delta.  Maybe the turbo guys can get up high and take advantage of cooler temps even in summer?  
Just to pick an example, here’s Boise, Idaho vs Palm Coast, Florida:

[wombat]

1 hour ago, A64Pilot said:

Your mixing analogies, picking cases to support you assertion that LOP is “better”

Let’s use the case the OP posted about to start this thread.

”I’ll be flying WOT at 8500 LOP”

He will be flying slower than if he was ROP, yes he will be getting better MPG, I stated that, but at a slower speed, IF speed was more important than MPG, then you go ROP, burn the fuel and go faster. He was asking about what A/S he will get so speed is at least an interest.

Most of us cruise at higher altitudes when flying significant distances, most of us do so WOT, because even WOT we are most likely below 75% power, so if speed is most important, then ROP is the way to go, if efficiency is sought, then LOP, AND slow down will get you there with the least fuel burned. So most of us cannot fly at the same power setting LOP that we can ROP

Sometimes depending on length of the leg being flown, slowing down and LOP can get you there faster, because if ROP you would have to stop for fuel, while LOP and slower you won’t. It’s not common but worth flight planning to see.

There is no one “best” mixture to fly, I have nothing against LOP, probably 90% or better of my flying is LOP, because I’m Retired and not usually in a hurry, but if I am I know to screw the mixture knob in until I’m 100F ROP, the increase in speed is significant, but of course so is the fuel burn.

It’s a pretty safe statement to make that LOP makes less power than ROP.

I don't think LOP is better, it's different.   It has some advantages, such as better MPG.  It has some disadvantages, such as power settings you can't run. In my 182, I very rarely run any power settings that I could achieve LOP. 

At WOT at any given altitude you will have a lower power setting LOP than ROP because at WOT your power is limited by the amount of air you can get into the cylinder and if you change to limiting that by fuel, of course you are going to be lower power.   If you are flying WOT ROP and switch to LOP, you will fly slower. 

For every LOP setting, there is a safe ROP setting that will cause you to fly faster.   There are ROP settings for which there is no safe or achievable LOP setting.

LOP has more restrictive limits than ROP.  Some are temperature limits, some are not.   At 8,500' in a NA engine, you can probably skip LOP and ROP, and just fly whatever mixture you want.

If you want to fly at a power setting (including considering altitude) that is only available ROP, the nearest LOP is going to be lower power.  And as such, you'll be flying slower.

If you are already flying a power setting that is available in both ROP and LOP, you won't go faster or slower if you switch to the LOP version.

I disagree that it's a safe statement to say that LOP makes less power than ROP.    It is a safe statement to make that there are many power settings that are not available LOP but are available ROP, and that these are all going to be power settings higher than the closest available LOP power setting.

[McMooney]

Here she is 7500 ft, 23/2300, running really rich and a more rearward cg

the g5's are in kts.  It's usually not worth burning the extra gas, using 3 hour legs, i'd lland like 5 mins sooner

also, i'm noticing, i NEVER get a tailwind

i

 

Edited August 16, 2024 by McMooney

[Echo]

1 hour ago, McMooney said:

Here she is 7500 ft, 23/2300, running really rich and a more rearward cg

the g5's are in kts.  It's usually not worth burning the extra gas, using 3 hour legs, i'd lland like 5 mins sooner

also, i'm noticing, i NEVER get a tailwind

i

 

At 10.2 I am nearly 30 mph faster. That is why I bought a Mooney. ESPECIALLY if I have a headwind. A ground speed lower than 130 is not going to happen in my Mooney.  You don’t cover 60 miles in five minutes 

[Echo]

2 minutes ago, Echo said:

At 10.2 I am nearly 30 mph faster. That is why I bought a Mooney. ESPECIALLY if I have a headwind. A ground speed lower than 130 is not going to happen in my Mooney.  You don’t cover 60 miles in five minutes 

OK knots…Define “really really rich”. What is your fuel flow?

[Ragsf15e]

1 hour ago, McMooney said:

Here she is 7500 ft, 23/2300, running really rich and a more rearward cg

the g5's are in kts.  It's usually not worth burning the extra gas, using 3 hour legs, i'd lland like 5 mins sooner

also, i'm noticing, i NEVER get a tailwind

i

 

Couple things…

The displayed GS is precise.  The displayed TAS is only as good as your CAS, temp, altimeter setting, etc.  is your G5 using CAS or IAS?  How good is your displayed airspeed?  You must do a good 3 way groundspeed test to and enter the GS values in a computer to know for sure.  I find that my IAS is about 3kts fast.

Now, why are you “always into a headwind”?  Well first, it’s actually true that you’ll see more hw component than tw because you always have to turn into the wind to maintain your course (not to be confused with heading).  So of the 360 degrees of possible wind angles, more than half result in a headwind.  Second, if your IAS is a couple knots fast (as I suspect), you’ll find that the correctly displayed GS vs incorrect TAS will show that you have a HW even if you don’t.

[Echo]

4 hours ago, MikeOH said:

Hmm, that doesn't seem right.  I can keep pulling the mixture until the engine pretty much quits making any power without any roughness.  Have you done the GAMI test to see how balanced your injectors are?

I have not.  I am more of a peak guy.  I fly high and give the beans...mostly.

[Echo]

49 minutes ago, Ragsf15e said:

Couple things…

The displayed GS is precise.  The displayed TAS is only as good as your CAS, temp, altimeter setting, etc.  is your G5 using CAS or IAS?  How good is your displayed airspeed?  You must do a good 3 way groundspeed test to and enter the GS values in a computer to know for sure.  I find that my IAS is about 3kts fast.

Now, why are you “always into a headwind”?  Well first, it’s actually true that you’ll see more hw component than tw because you always have to turn into the wind to maintain your course (not to be confused with heading).  So of the 360 degrees of possible wind angles, more than half result in a headwind.  Second, if your IAS is a couple knots fast (as I suspect), you’ll find that the correctly displayed GS vs incorrect TAS will show that you have a HW even if you don’t.

I am retired so headwinds are the exception...

[McMooney]

2 hours ago, Echo said:

OK knots…Define “really really rich”. What is your fuel flow?

it's right there in the picture 12.5 gph &) 

[McMooney]

wax her and put something in baggage, slide your seat back during cruise, you'll go 3 to 5kts faster

 

[ArtVandelay]

I agree about the temp making a big difference, but i think it’s pretty similar in the summer.  Of course it depends on exactly where you are, but summer temps aloft are relatively similar.  The winter ones have much more delta.  Maybe the turbo guys can get up high and take advantage of cooler temps even in summer?  
Just to pick an example, here’s Boise, Idaho vs Palm Coast, Florida:

Don’t forget humidity alone can rob you of 10% horsepower.

[AndreiC]

As the OP of this thread I should have said that on this trip I plan to be alone in the plane, starting with full tanks and going about 4 hours per leg. So starting about 300 lbs under MGW and ending about 520 under. Not much stuff to put in the baggage compartment. 

I’ll report in about a week and a half what performance numbers I see. Incidentally, I suspect my airspeed indicator is also showing a tad fast. I hope to figure out a bit more about calibrating it in the next few days. What calculator do you guys use to plug in figures from a three directions run?

[Ragsf15e]

44 minutes ago, AndreiC said:

As the OP of this thread I should have said that on this trip I plan to be alone in the plane, starting with full tanks and going about 4 hours per leg. So starting about 300 lbs under MGW and ending about 520 under. Not much stuff to put in the baggage compartment. 

I’ll report in about a week and a half what performance numbers I see. Incidentally, I suspect my airspeed indicator is also showing a tad fast. I hope to figure out a bit more about calibrating it in the next few days. What calculator do you guys use to plug in figures from a three directions run?

http://www.csgnetwork.com/tasgpscalc.html
 

[Shadrach]

21 hours ago, AndreiC said:

I have been curious if my 1970 E-model is on the slow side, or if I am seeing pretty much the speed to be expected (whatever it is, I don’t think mine is particularly fast). So I am asking you guys to take a guess what kind of TAS I should expect for a long upcoming flight (around 16 hours round trip).

My plane has a couple of things running against it — three blade prop, and the less clean wings (fewer flush rivets) than the earlier models. On the plus side the engine is relatively new (about 600 SMOH and 300 since new cylinders), and it has the LASAR guppy mouth closure (but not the more modern J-style). Pretty much no other speed mods to speak of.

I plan to fly it at 8500’, WOT, LOP 65% (8.6 gph), 2400 or 2500 RPM. Will you please take a guess what TAS I should see in these conditions at the two RPM settings above?

140kts +/- 5kts

[Shadrach]

20 hours ago, A64Pilot said:

Assuming you can get 8.6GPH at 8500 and be LOP, then you will be at 65% power. I don’t think I can, but then I likely am at a higher temp so 8500 MSL is likely a higher DA than where you are.

However if everything is equal, you will burn slightly more fuel and therefore develop slightly more power and therefore go slightly faster at 2500 RPM than 2400 RPM.

However if you lean more at higher RPM to keep the fuel burn the same, then you will go slightly slower due to power being the same, but increased friction of both the engine and prop. Higher RPM only increases speed due to higher power output, but higher RPM is slightly less efficient due to greater frictional losses, again small numbers, not much difference.

WOT is slightly more efficient than partial throttle due to lower pumping losses, no vacuum.

We aren’t talking big numbers here, a kt or two.

If I were to guess I’d guess your airplane is lighter than a newer aircraft as most often newer aircraft weigh more than earlier ones and that lower weight will offset any additional drag you may have from more button head rivets etc.

Loading any heavy baggage in the rear etc to push the CG back as long as your well within acceptable range seems to do as much to increase speed as many of the speed mods.

LOP really hurts speed, but of course does increase MPG, a significant amount of that better MPG comes from lower speed, but whatever, LOP does increase MPG.

 

Cruise power tables suggest that LOP is doable at the altitudes mentioned, but in some cases rpm will need to be increased.

[Echo]

10 hours ago, McMooney said:

it's right there in the picture 12.5 gph &) 

Ahhhhhh, O.K. up there in the top right corner.  I don't know how I missed that.

[Shadrach]

22 hours ago, A64Pilot said:

Your mixing analogies, picking cases to support you assertion that LOP is “better”

Let’s use the case the OP posted about to start this thread.

”I’ll be flying WOT at 8500 LOP”

He will be flying slower than if he was ROP, yes he will be getting better MPG, I stated that, but at a slower speed, IF speed was more important than MPG, then you go ROP, burn the fuel and go faster. He was asking about what A/S he will get so speed is at least an interest.

Most of us cruise at higher altitudes when flying significant distances, most of us do so WOT, because even WOT we are most likely below 75% power, so if speed is most important, then ROP is the way to go, if efficiency is sought, then LOP, AND slow down will get you there with the least fuel burned. So most of us cannot fly at the same power setting LOP that we can ROP

Sometimes depending on length of the leg being flown, slowing down and LOP can get you there faster, because if ROP you would have to stop for fuel, while LOP and slower you won’t. It’s not common but worth flight planning to see.

There is no one “best” mixture to fly, I have nothing against LOP, probably 90% or better of my flying is LOP, because I’m Retired and not usually in a hurry, but if I am I know to screw the mixture knob in until I’m 100F ROP, the increase in speed is significant, but of course so is the fuel burn.

It’s a pretty safe statement to make that LOP makes less power than ROP.

He’s not mixing analogies to support anything. 65% is 65%. You’ve spent several paragraphs needlessly muddying the water. All that matters is that there is sufficient air available to facilitate a lean of stoic combustion event that contains sufficient fuel to generate 65% horsepower.

 

[Schllc]

Beware of the magic Mooney owners, they are always  opining on the performance that defies the rest of the fleet.   Just like all the O3 owners who see 190tas at 8,000 on 11gph. 
trust but verify…..

[Shadrach]

19 hours ago, Echo said:

What a guy on youtube logged:

 

Those numbers look optimistic me. Without seeing gps flight data of a three-way speed run, I am skeptical.

I am currently in the process of adjusting JPI K-Factor with the goal of achieving FF accuracy of <.3GPH. That process has left me skeptical that any monitor is sufficiently accurate to determine LOP power until tested.

[N201MKTurbo]

19 minutes ago, Shadrach said:

Those numbers look optimistic me. Without seeing gps flight data of a three-way speed run, I am skeptical.

I am currently in the process of adjusting JPI K-Factor with the goal of achieving FF accuracy of <.3GPH. That process has left me skeptical that any monitor is sufficiently accurate to determine LOP power until tested.

I could dive from 8500 feet then level off and snap a pic and get better numbers than that.

[Echo]

1 hour ago, Shadrach said:

Those numbers look optimistic me. Without seeing gps flight data of a three-way speed run, I am skeptical.

I am currently in the process of adjusting JPI K-Factor with the goal of achieving FF accuracy of <.3GPH. That process has left me skeptical that any monitor is sufficiently accurate to determine LOP power until tested.

Ross, I had 2500 instead of his 2400rpm  and bested his 7500’ speed.  I essentially have a J in my E. He had cowl and speed slope mods on his E. 

[Echo]

1 hour ago, N201MKTurbo said:

I could dive from 8500 feet then level off and snap a pic and get better numbers than that.

Congrats?

[Echo]

I just provided Andre some data. Lol

[Shadrach]

2 hours ago, Echo said:

Ross, I had 2500 instead of his 2400rpm  and bested his 7500’ speed.  I essentially have a J in my E. He had cowl and speed slope mods on his E. 

Are you the YouTube guy to which I was referring? Those are the number that looked a bit flakey.  Seems highly unlikely that an additional 1000ft and .01gph of fuel netted nearly 4kts of additional TAS.