Is my Mooney slow?

[Shadrach]

Just now, AndreiC said:

What does RAO mean?

Ram air Open.

I have logged many hours at 2500msl WOTRAO in the winter when the DA at that altitude is about -500MSL.  30”inhg, 2500rpm and 40LOP on richest cylinder 157KIAS (which corrects to about 155).

[Echo]

I also love when an M20E guy asks if his plane is slow and a turbo normalized F owner brings his flex in.  Super relevant and entertaining.

[M20F]

16 minutes ago, AndreiC said:

Wow! Impressive. Many speed mods, I assume?

No just one 

[AndreiC]

18 minutes ago, Shadrach said:

Ram air Open.

I have logged many hours at 2500msl WOTRAO in the winter when the DA at that altitude is about -500MSL.  30”inhg, 2500rpm and 40LOP on richest cylinder 157KIAS (which corrects to about 155).

What fuel burn do you see at this setting? Curious what % power you're at, but can't compute without knowing FF. (Lycoming manuals say at these settings, full rich you'd be at 103.3%, 207 hp.)

[Shadrach]

10 minutes ago, AndreiC said:

What fuel burn do you see at this setting? Curious what % power you're at, but can't compute without knowing FF. (Lycoming manuals say at these settings, full rich you'd be at 103.3%, 207 hp.)

I don’t have reliable data yet. I am in the process of fine tuning my totalizer. I would guess low 11 to high 10gph range depending on temp and pressure.

[Will.iam]

22 hours ago, Shadrach said:

I am pretty sure my engine will make 65% hp LOP at 7500’. 

 

 

 

 

Maybe so but i can make 73% at that same altitude or higher. I have choices that NA engines do not and still stay below oxygen use altitude requirements. Or i can climb LOP. Sure NA could start climbing LOP but would quickly run out of the extra air required to push 78% power. Sure my climb is cut in half but my fuel flow is also cut more than half giving me more range than if i climb at 25 gal/hr. But the best part is enjoying  20 degrees cooler cht’s when in the hot summer time with outside temps pushing 40c  when full rich my cylinders are around 400 cht but LOP they are 380 climbing out. 

[Will.iam]

7 hours ago, Fly Boomer said:

This is quite likely not relevant, but I was inspired by this topic to seek out some of Walter Atkinson's writings, and this one kind of jogged my brain in a new way:

"For example, when LOP all of the below settings produce the same HP:

25/2500/14 gph
25/2400/14 gph
23/2400/14 gph
25/2700/14 gph
28/2700/14 gph
and so on...

When ROP, all of the below settings are the same HP:

23/2300/18 gph
23/2300/17 gph
23/2300/16 gph
23/2300/15 gph
23/2300/14 gph
and so on."

 

I don’t know what engine he is referencing but it’s not my TSIO-360 as at that high of FF i would be roasting my turbo. 14gph puts me at 91% power.  LOP at 11.3 gal per hour (73% power) I’m at 1550TIT at 12 gal per hour (78% power) puts me at 1600TIT no way I’m getting 14 gal per hour and stay under 1650. 
LOP does run hotter egt than ROP which for an NA no problem exhaust manifold can handle the higher heat but not a turbo. 

[Shadrach]

4 hours ago, Will.iam said:

Maybe so but i can make 73% at that same altitude or higher. I have choices that NA engines do not and still stay below oxygen use altitude requirements. Or i can climb LOP. Sure NA could start climbing LOP but would quickly run out of the extra air required to push 78% power. Sure my climb is cut in half but my fuel flow is also cut more than half giving me more range than if i climb at 25 gal/hr. But the best part is enjoying  20 degrees cooler cht’s when in the hot summer time with outside temps pushing 40c  when full rich my cylinders are around 400 cht but LOP they are 380 climbing out. 

No question that a turbo affords you choices that NA operators don’t have. Whether those choices are worth the cost, heat and weight depends on the mission. I think you may be underestimating how well the NA birds do below Oxygen altitudes. My plane is vey useable up to  12’500msl even in the months where the DA might be in the mid teens. I’m not concerned with mixture setting up high, only available power and fuel burn.  Does it make book numbers? Close enough.  
 

[Shadrach]

9 hours ago, AndreiC said:

What fuel burn do you see at this setting? Curious what % power you're at, but can't compute without knowing FF. (Lycoming manuals say at these settings, full rich you'd be at 103.3%, 207 hp.)

Probably more at full rich if factoring in temperatures that accompany such conditions.  I only mention it as an example of my comfort running LOP at high power. On other hand, there are very few scenario where I would choose LOP above 5000’ DAs

[AndreiC]

1 hour ago, Shadrach said:

Probably more at full rich if factoring in temperatures that accompany such conditions.  I only mention it as an example of my comfort running LOP at high power. On other hand, there are very few scenario where I would choose LOP above 5000’ DAs

What would you run above 5000? Peak, 50 F above peak, 100 F above peak?

[Shadrach]

1 hour ago, AndreiC said:

What would you run above 5000? Peak, 50 F above peak, 100 F above peak?

When running LOP, I choose the mixture setting that is as close to peak as possible that yields healthy CHTs taking into consideration the OAT. As I get higher, that setting gets closer and closer to peak EGT. At DAs of 10K or more I run 100ROP. 
 

in most cases, I am shooting for maximum speed per unit of fuel. At a given manifold pressure and RPM, the intersection of best speed and fuel burn is peak EGT. It is near best BSFC and before significant power loss, but well after peak CHT. It’s not ideal, but it’s a close to ideal as there is for NA operations.

 

[Echo]

15 hours ago, AndreiC said:

Since I was asked “compared to what?” — my question was meant to be “compared to similar planes to mine, but well-configured.” In other words — am I getting the most bang for my airplane, or should I try to improve rigging, add speed mods, etc. 

The reason for asking this is that I have heard it said many times that book numbers are a bit of a marketing gimmick, as in they are what a test pilot managed to get on a perfectly calm day, with a plane that had no antennas, freshly waxed new paint, brand new prop, etc. I certainly can’t seem to be able to reproduce these numbers. The question was, for my airplane as described (55 years old, 3 blade prop, non-flush rivets, etc.) how much of the performance penalty comes from these, which are things I can’t change easily, and how much is a problem of rigging, or other small things that I can hope to correct.

By asking people to guess, and then comparing to what I will see in a real world situation, I hope to answer the question above. The specific power setting, and especially the LOP/ROP debate was not what I meant to ask — it was just so we have a specific setting to talk about. 

Andre,

We both have E models.  I used to have an E with a three blade prop.  I don't think the cruise penalty is more than a couple knots.  The rivets are a trivial speed penalty as well.  What do you normally see for true airspeed at what I think are best altitude for our M20E models (7500-9500')?  I tried to provide what my plane does with a similar weight (600lbs with me, dogs, baggage and fuel).  At 7500' burning 10.2 my TAS was 159 knots.  Because of J cowl, speed slope and two blade prop I would estimate that at same engine set up you would be able to achieve 151 knots in your plane.  Let me/us know how you do.  Have a fun safe trip.  Scott

[Pinecone]

LOP can be used at any power setting.  As long as you ARE LEAN OF PEAK.   The problem with the higher power settings is that people tend to think if the temps are a bit high, richen.  But when LOP, that can put you in the danger area.  You MUST remember, LEANER to COOL if you LOP.

John Deakin ran his Bo by taking off, and giving the BMP (Big Mixture Pull) to LOP at full throttle, max RPM at near sea level.

[Shadrach]

1 hour ago, Echo said:

Andre,

We both have E models.  I used to have an E with a three blade prop.  I don't think the cruise penalty is more than a couple knots.  The rivets are a trivial speed penalty as well.  What do you normally see for true airspeed at what I think are best altitude for our M20E models (7500-9500')?  I tried to provide what my plane does with a similar weight (600lbs with me, dogs, baggage and fuel).  At 7500' burning 10.2 my TAS was 159 knots.  Because of J cowl, speed slope and two blade prop I would estimate that at same engine set up you would be able to achieve 151 knots in your plane.  Let me/us know how you do.  Have a fun safe trip.  Scott

Scott,

Those are really good numbers. I am not trying to pee in your cheerios here but some Aspen installations have the propensity to overstate OAT which in turn can inflate calculated TAS. Have you crosschecked the primary thermometer with the Aspens OAT reading?

A 3 way GPS speed run on a smooth day is the closest we can get to determining actual speed.

[Echo]

24 minutes ago, Shadrach said:

Scott,

Those are really good numbers. I am not trying to pee in your cheerios here but some Aspen installations have the propensity to overstate OAT which in turn can inflate calculated TAS. Have you crosschecked the primary thermometer with the Aspens OAT reading?

A 3 way GPS speed run on a smooth day is the closest we can get to determining actual speed.

Yes. I have two probes. One on Aspen. One on 830. I fly to go places fast. I just don’t find time for three way. Speed in planes have many variables 

[Echo]

One 66 on temp one 67. 

[Echo]

All good Ross. I provided my data with photos and compared to another E owner. Just trying to help Andre get there. Speed mods and flying with more fuel ((like 1gph) DO make a big difference 

[Echo]

11.00 for my usual two hours flight. Cheap speed mod

[AndreiC]

3 hours ago, Echo said:

Andre,

We both have E models.  I used to have an E with a three blade prop.  I don't think the cruise penalty is more than a couple knots.  The rivets are a trivial speed penalty as well.  What do you normally see for true airspeed at what I think are best altitude for our M20E models (7500-9500')?  I tried to provide what my plane does with a similar weight (600lbs with me, dogs, baggage and fuel).  At 7500' burning 10.2 my TAS was 159 knots.  Because of J cowl, speed slope and two blade prop I would estimate that at same engine set up you would be able to achieve 151 knots in your plane.  Let me/us know how you do.  Have a fun safe trip.  Scott

I don't think I see speeds even close to that. What I know is that at 7500, with a gross weight of 2200 lbs,  on 10.2 gph the Mooney test pilots were not able to squeeze more than 151 kts (174 mph) out of a very clean, brand new airframe and engine. (See table from POH.) My guess is that your speed mods do a lot of work, and you have an exceptionally straight airframe to get an extra 8 kts out of the same airframe. I will go out this afternoon and try to check my speeds using a 3 way run, but I think on these kinds of fuel burns I won't see more than 145 kts, if even that.

[Shadrach]

3 minutes ago, AndreiC said:

I don't think I see speeds even close to that. What I know is that at 7500, with a gross weight of 2200 lbs,  on 10.2 gph the Mooney test pilots were not able to squeeze more than 151 kts (174 mph) out of a very clean, brand new airframe and engine. (See table from POH.) My guess is that your speed mods do a lot of work, and you have an exceptionally straight airframe to get an extra 8 kts out of the same airframe. I will go out this afternoon and try to check my speeds using a 3 way run, but I think on these kinds of fuel burns I won't see more than 145 kts, if even that.

At 2200lbs, you should definitely be 150kts or more leaned for best power at 7500’.

[Echo]

1 hour ago, AndreiC said:

I don't think I see speeds even close to that. What I know is that at 7500, with a gross weight of 2200 lbs,  on 10.2 gph the Mooney test pilots were not able to squeeze more than 151 kts (174 mph) out of a very clean, brand new airframe and engine. (See table from POH.) My guess is that your speed mods do a lot of work, and you have an exceptionally straight airframe to get an extra 8 kts out of the same airframe. I will go out this afternoon and try to check my speeds using a 3 way run, but I think on these kinds of fuel burns I won't see more than 145 kts, if even that.

I understand.  I think the J cowl is a big speed enhancer.  I have full dorsal fairing too. I was only 2 mph faster than book with nice mods….

Edited August 19 by Echo

[Shadrach]

2 hours ago, Echo said:

I understand.  I think the J cowl is a big speed enhancer.  I have full dorsal fairing too. I was only 2 mph faster than book with nice mods….

The early poh’s were optimistic. Someone gave the factory a dose of truth serum in 1968.

1967 AFM cruise numbers for M20F at 7500’

 

1968 AFM cruise numbers for M20F at 7500’

[Fly Boomer]

16 hours ago, Will.iam said:

I don’t know what engine he is referencing but it’s not my TSIO-360 as at that high of FF i would be roasting my turbo. 14gph puts me at 91% power.  LOP at 11.3 gal per hour (73% power) I’m at 1550TIT at 12 gal per hour (78% power) puts me at 1600TIT no way I’m getting 14 gal per hour and stay under 1650. 
LOP does run hotter egt than ROP which for an NA no problem exhaust manifold can handle the higher heat but not a turbo. 

He is not quoting numbers for any specific engine.  Rather, he is making the point that when ROP, an engine is puking out unburned fuel, so you can't determine power by measuring fuel flow because there is no direct way to know how much fuel is being burned--power is determined by MP and RPM.

When LOP, the engine has excess air, and virtually all the fuel is being burned--power is directly proportional to fuel flow without much regard to MP and RPM.

[Shadrach]

2 minutes ago, Fly Boomer said:

He is not quoting numbers for any specific engine.  Rather, he is making the point that when ROP, an engine is puking out unburned fuel, so you can't determine power by measuring fuel flow because there is no direct way to know how much fuel is being burned--power is determined by MP and RPM.

When LOP, the engine has excess air, and virtually all the fuel is being burned--power is directly proportional to fuel flow without much regard to MP and RPM.

AKA mass airflow. 

[AndreiC]

OK, I went up today and did 5 different 3-way runs to test things. The conditions were all ISA+25F (so DA was about 1500FT over PA), but unfortunately the air was not quite perfectly smooth at 7500 and 8500 -- there was some very light chop. I don't know how much this affects things. The plane was light, well under 2200 lbs.

In any case, as I had thought previously, I did not get anywhere close to the numbers predicted above; I think my plane has a penalty of about 8-10 knots over the book numbers. I would appreciate it if people could tell me what aspects of the rigging can be improved, so I can talk to my mechanic to look at these at annual.

Here are the various runs. All were done with Ram Air Open, WOT. This meant I got 23.2" MP at 7500, and 22.2" at 8500.

Run 1: 7500 FT, 100F ROP, 2420 RPM -- TAS 142.4 kts

Run 2: 7500 FT, 100F ROP, 2550 RPM -- TAS 146.4 kts

Run 3: 7500 FT, peak EGT (9.0 gph) 2400 RPM -- TAS 138 kts

Run 4: 8500 FT, 100F ROP, 2550 RPM -- TAS 144 kts

Run 5: 8500 FT, peak EGT (9.0 gph) 2400 RPM -- TAS 139 kts.

So it seems there is not much difference between 7500 and 8500. Running at peak and 2400 RPM saves about 2 gph (= 17.8 mpg) over 100F ROP 2550 RPM (= 15 mpg), but it means losing about 8 knots.

Main questions:

a) Can a light chop affect the TAS significantly?

b) Can a strong wind at altitude affect measurements? (The winds were about 24-29 kts.)

c) What aspects of the rigging can be checked relatively easily and improved upon?

Thanks, Andrei.