Climb Performance- POH Also Optimistic?

[802flyer]

 

New owner of a M20F and am getting settled into the plane. It seems well agreed upon that the cruise performance numbers in the POH were written by the sales team rather than the engineers/test pilots. Is this also true for the climb performance table?

 

It would suggest that a 67 M20F at ‘standard altitude’ of 2000ft as determined by the POH chart (appropriate for my field elevation/temp/density altitude lately) would climb at 1260fpm when loaded to 2300lbs, but I’m seeing roughly half that.

 

Engine monitor shows appropriate MP and RPM (verified against optical tach) and seems to be running fine based on the savvy test profiles.

 

I’ve searched and found a few threads discussing takeoff profiles which seem to hint that my performance is in the range of normal, but those threads seem to spend more time discussing the merits of Vx vs. Vy and when to raise the gear, rather than real world expectations for FPM through the first few thousand feet at varying density altitudes. Most of my takeoffs will be with negative DAs during the winter and in the 2-3000 ft DA range during the summer.

 

Curious to hear what you all see for climb performance during the first few thousand feet after takeoff?

 

Thanks!

 

 

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Edited August 2, 2022 by 802flyer

[Marauder]

 
New owner of a M20F and am getting settled into the plane. It seems well agreed upon that the cruise performance numbers in the POH were written by the sales team rather than the engineers/test pilots. Is this also true for the climb performance table?
 
It would suggest that a 67 M20F at ‘standard altitude’ of 2000ft as determined by the POH chart (appropriate for my field elevation/temp/density altitude lately) would climb at 1260fpm when loaded to 2300lbs, but I’m seeing roughly half that.
 
Engine monitor shows appropriate MP and RPM (verified against optical tach) and seems to be running fine based on the savvy test profiles.
 
I’ve searched and found a few threads discussing takeoff profiles which seem to hint that my performance is in the range of normal, but those threads seem to spend more time discussing the merits of Vx vs. Vy and when to raise the gear, rather than real world expectations for FPM through the first few thousand feet at varying density altitudes. Most of my takeoffs will be with negative DAs during the winter and in the 2-3000 ft DA range during the summer.
 
Curious to hear what you all see for climb performance during the first few thousand feet after takeoff?
 
Thanks!
 
 
Sent from my iPhone using Tapatalk
 

I’ve owned my F for 31 years and can tell you that density altitude will have an influence as well as the speed you climb out at.

What airspeed are climbing out at? If I climb at Vx, I’ll see initial climbs in the range of the POH. But add in warmer temps, it’ll drop.


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[802flyer]

24 minutes ago, Marauder said:

I’ve owned my F for 31 years and can tell you that density altitude will have an influence as well as the speed you climb out at.

What airspeed are climbing out at? If I climb at Vx, I’ll see initial climbs in the range of the POH. But add in warmer temps, it’ll drop.


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Density altitudes have been around 2-3000ft and I typically climb at 110-120mph indicated; 110 being around Vy at those density altitudes, and accelerating to 120mph for cooling/cruise climb. The table in the POH suggests I should still be getting at or above 1000fpm through 4000ft DA at Vy, when in reality I'm seeing more like 650fpm.

 

 

[gmonnig]

I'd say that im seeing the same performance discrepancies you are. I was looking specifically for an E model due to the higher climb rates over other models. In reality, they probably all climb out similar. One thing to note is the "full power/2700rpm & powerboost on". I don't know if everyone actually climbs like that, a lot might be using 25 Squared. I have been babying the new engine but I'm thinking about running harder now that there's more hours on it. Still don't use the powerboost in climb until 6k feet too.

[Marauder]

I'd say that im seeing the same performance discrepancies you are. I was looking specifically for an E model due to the higher climb rates over other models. In reality, they probably all climb out similar. One thing to note is the "full power/2700rpm & powerboost on". I don't know if everyone actually climbs like that, a lot might be using 25 Squared. I have been babying the new engine but I'm thinking about running harder now that there's more hours on it. Still don't use the powerboost in climb until 6k feet too.

I think you point out a really good point. The “power boost” on my plane is good for 1.5 inches of manifold pressure on an F model. I would never open that door in the lower altitudes. If you did, I suspect he’d see numbers closer to the POH.

Another thing to keep in mind, I’m sure this POH was done under “optimum” conditions that as you (the OP) mentioned as something the sales and marketing people would want.

And I’m sure it was with a new engine. I would also check your CAS airspeed. It may be a knot or two slower.


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[Igor_U]

I am quite certain that if you compare 67 POH with 68 and later, speed are different, with newer POH being more realistic. Perhaps Vertical speed were changed as well?

My modified 67 F (201 Windshield, gaps, LASAR cowl) matches the book speeds but not really the VS, especially in the summer. I also do not use RAM air below 4000'.

 

[Guest]

Imagine how poor the climb performance would be if the earth were actually flat.  The curve does improve it somewhat.

 

[Marauder]

Imagine how poor the climb performance would be if the earth were actually flat.  The curve does improve it somewhat.
 

I thought that only applied in my SR-71.


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[MikeOH]

29 minutes ago, Marauder said:

I thought that only applied in my SR-71.


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Yeah, it's probably only climbing at 650 fpm, too......at 100,000 feet

[802flyer]

3 hours ago, gmonnig said:

I'd say that im seeing the same performance discrepancies you are.

2 hours ago, Igor_U said:

My modified 67 F (201 Windshield, gaps, LASAR cowl) matches the book speeds but not really the VS, especially in the summer.

Well there's a few data points to suggest that my engine isn't well behind the crowd, which is reassuring. Was concerned about its health given the large gap from the book data.

 

3 hours ago, gmonnig said:

Still don't use the powerboost in climb until 6k feet too.

2 hours ago, Marauder said:

I think you point a really good point. The “power boost” on my plane is good for 1.5 inches of manifold pressure on an F model. I would never open that door in the lower altitudes.

2 hours ago, Igor_U said:

I also do not use RAM air below 4000'.

Agree on all points here. I've not been using it below around 5,000ft which seems to be pretty close to consensus.

 

[802flyer]

2 hours ago, Igor_U said:

My modified 67 F (201 Windshield, gaps, LASAR cowl) matches the book speeds but not really the VS, especially in the summer.

Mine has modded gaps, windshield, and cowl as well. With a density altitude in the 3000ft range, do you have a guess as to what you expect to see for the first few thousand AGL? I'll certainly do more testing of my own plane since they're all going to be a bit different after 50+ years of varying upgrades/upkeep, but I'm just trying to understand if I'm near par or not.

[Shadrach]

Is your ignition timed to 20 or 25°? Both are legal per TCDS. Lycoming made 20° optional at a later date and deliver all factory engines set to 20°. The performance numbers in you POH we’re based on a stock aircraft with ignition timing set at 25° which was the only setting approved when the aircraft and the engine were originally certified.  Many will say does not matter but that has not been my experience. 
 

FWIW, I fly a stock 67F and find that book numbers are pretty close. I would have no problems exceeding 1000fpm at the DAs you mentioned. 

[Ragsf15e]

13 hours ago, 802flyer said:

Mine has modded gaps, windshield, and cowl as well. With a density altitude in the 3000ft range, do you have a guess as to what you expect to see for the first few thousand AGL? I'll certainly do more testing of my own plane since they're all going to be a bit different after 50+ years of varying upgrades/upkeep, but I'm just trying to understand if I'm near par or not.

My ‘68 F can get to ~1000 fpm only at sea level, cool conditions, and “middle” weight.  Typically the DA is ~3000’ where i fly and your numbers seem normal.  When I fly at ~2600lbs, 3000’ DA, I’m looking at 600-700fpm.

Here’s something though, weight is going to be a huge factor in climb.  You said 2300lbs in your initial post… that’s 440lbs below gross.  There will be a significant difference between 2200 and 2600lbs.  You will find weight is a huge factor in speed as well.  100lbs will change your TAS by a couple knots.
 

I also didn’t see if you leave 2700rpm.  That helps a lot.

[EricJ]

15 hours ago, M20Doc said:

Imagine how poor the climb performance would be if the earth were actually flat.  The curve does improve it somewhat.

It's not flat!   This guy proved it with scripture.

[DCarlton]

One of the things I really enjoy about my 67F (with the three blade) is climb performance.  Seeing over a 1000 fpm always makes me "happy".  With that said, I've gotten lazy.  I never closely watch or compare climb performance numbers.  Whatever I need seems to always be there (with necessary adjustments when it's hot or high).  I'm going to take a closer look now (it's been a long time) and record some data.  

[Shadrach]

11 hours ago, Ragsf15e said:

My ‘68 F can get to ~1000 fpm only at sea level, cool conditions, and “middle” weight.  Typically the DA is ~3000’ where i fly and your numbers seem normal.  When I fly at ~2600lbs, 3000’ DA, I’m looking at 600-700fpm.

Here’s something though, weight is going to be a huge factor in climb.  You said 2300lbs in your initial post… that’s 440lbs below gross.  There will be a significant difference between 2200 and 2600lbs.  You will find weight is a huge factor in speed as well.  100lbs will change your TAS by a couple knots.
 

I also didn’t see if you leave 2700rpm.  That helps a lot.

I did a time to climb last fall in my airplane from 1000 feet to 10,000 MSL. I was probably around 2200lbs. The long and short of it is that I averaged over 1000 ft./min. I wish I had saved the flightawear history. I did have this screenshot from another flight. I was also solo, but averaged over 1400fpm to 5200ft.
The only observation I can factually make is that there is a large delta in climb performance from plane to plane within the same model.  I should also add that I’m only getting 2650 at max rpm. Someday I’ll some of the motivation to re-clock the governor but for now I find the performance acceptable.

[David Lloyd]

Good suggestions above, but if you are really curious about your airplane's performance, test it yourself.  Make a couple charts similar to those in your POH, load the airplane to the appropriate weight and fill in the blanks.  Gear up, flaps up, full throttle, 2700 RPM, cowl flaps open, power boost on, mixture rich (by 6 or 7k, start leaning) and at Vy based on pressure altitude. Don't try this on a hot, bumpy day, go instead on a cool day, no winds or turbulence.  Write down the time for each cardinal altitude.  Repeat at least once. Average those times.  How do they compare to the POH?  Then, if you want to try with the power boost off, a lesser RPM or faster airspeed, make another chart.

My old C is slow but does seem to climb near what it should. Seldom I climb at Vy, always faster, less climb rate.

[Hank]

When I moved back South, the first summer I thought my engine was dying and in need of overhaul . . . It was very different from WV performance, where it's hot down low but not up high.

Coming home yesterday at 8000 msl, temps were 68ºF = 20ºC; descending to 4000 msl, they only rose to 72ºF = 22ºC, but at 2500 it was 82ºF = 28ºC. I forget what it was on the ground, but today is supposed to be 97º and tomorrow's forecast is 101.

On the other hand, every few years we will get a dusting of snow, and I just stay home . . . . There's nowhere to go with everything closed!

[Ragsf15e]

Many of us are going to climb faster ias than Vy for cooling which reduces the fpm.

 I do agree with @Shadrach that starting from a SL standard day at light weight and 2700 rpm, >1000fpm is achievable through at least 5000’ at Vy.

[Shadrach]

4 minutes ago, Ragsf15e said:

Many of us are going to climb faster ias than Vy for cooling which reduces the fpm.

 I do agree with @Shadrach that starting from a SL standard day at light weight and 2700 rpm, >1000fpm is achievable through at least 5000’ at Vy.

I’m usually well under max gross. My family of four with 60lbs of luggage and 50gal puts us around 2500lbs. It’s my experience that cruise climb of 120mph usually gives 1000fpm or better through 3000ft (DA).

[Ragsf15e]

5 hours ago, Shadrach said:

I’m usually well under max gross. My family of four with 60lbs of luggage and 50gal puts us around 2500lbs. It’s my experience that cruise climb of 120mph usually gives 1000fpm or better through 3000ft (DA).

You guys are light and pack well!

[Shadrach]

58 minutes ago, Ragsf15e said:

You guys are light and pack well!

More importantly, the Plane is light (1681lbs) and kids are young (5 and 6).

[Hank]

8 hours ago, Shadrach said:

I’m usually well under max gross. My family of four with 60lbs of luggage and 50gal puts us around 2500lbs. It’s my experience that cruise climb of 120mph usually gives 1000fpm or better through 3000ft (DA).

My wife can pack her weight in luggage! When we travel for 4-5 days, I'm generally near gross with an aft CG. My C climbs poorly above 5-6K in the summer when loaded like that.

But solo with half tanks is a whole different story!!

[802flyer]

Ok so I may have been seeing some overly gloomy data based on factors that a number of you have pointed out, for which I'm super grateful. I went out flying after work today, right around sunset. OAT was 73F on the ground, winds calm with smooth air, density altitude 2400 when I started flying and 1900 when I put it in the hanger. Weight right around 2300lbs.

First takeoff I got the gear up, climb at 95 with flaps 15deg all the way to pattern altitude, climbing at 95mph and seeing between 1000-1200fpm with WOT and RPM around 2680-2700.

Second takeoff was same power settings and gear retract point, however I retracted flaps pretty much as soon as I cleared the trees and then pitched for 110mph (pretty close approximation of Vy at my DA tonight). Definitely sat in the 500-600fpm zone for maybe 10-15seconds while accelerating to Vy as the flaps came up, and eventually crept back up to back over 1000fpm. This is pretty much the workflow I've been using lately.

My home airport sits in a bowl between two lines of mountains (or "mountains" for those of you out west... my peaks are around 4-5k above runway elevation). In scenario #2, I definitely notice that period of time during climbout where flaps have just come up and I'm wallowing at only 500fpm for what feels like quite a while as I look at the hills. This is probably where I had spent most of my recent time glancing at the VSI and wondering if my performance was up to spec.

I had also tried looking at my track log data recently to extrapolate some average FPM numbers for my recent cruise climbs. It seemed like those were also showing around the 650fpm I had quoted previously. That said, my Savvy data shows that those days were definitely warmer/bumpier which would hurt performance a bit, especially if I lower the nose to 120mph for cooling/cruise climb. And things will fall off as I get up above 5k, bringing the overall average lower.

This evening I made a climb up to 6500 feet while holding 110-105mph, and was seeing around 1000fpm for the first half and not less than 750 for the rest. Turning power boost on at 5000ft brought me right back up near 1000fpm. Again, cooler and smoother air probably helped as well.

So in summary, things seem better than I had thought and much closer to book values. Everyone's input was super valuable in coming up with some real-world expectations and then getting out and testing. I think a huge contributing factor was the perceived/real loss of climb performance at relatively low altitude as I retract flaps. For my home airport and those with surrounding hills, I'm going to keep flaps in longer for a better angle-of-climb until I'm in downwind pointed down the valley. Seems I still get a reasonable rate-of-climb in that configuration to make it worthwhile....At least as a preliminary plan; I'll probably do some more testing with flap settings a few degrees more/less than 15deg to see if I can optimize a bit. And repeat testing with more loading and weather variation. Plenty of reasons to go flying, it seems.

Was feeling a bit despondent about potentially being limited to the Yankee versions of the approaches due to inadequate ft/nm performance on the missed, but seems there's hope for the Zulu minimums at this point (pending testing in hotter weather, of course).

Again, big thanks to everyone that chimed in with their own observations, as well as those that pushed me to be a bit more deliberate about assessing my performance data.

 

[802flyer]

15 hours ago, Shadrach said:

Is your ignition timed to 20 or 25°? Both are legal per TCDS. Lycoming made 20° optional at a later date and deliver all factory engines set to 20°. The performance numbers in you POH we’re based on a stock aircraft with ignition timing set at 25° which was the only setting approved when the aircraft and the engine were originally certified.  Many will say does not matter but that has not been my experience. 
 

FWIW, I fly a stock 67F and find that book numbers are pretty close. I would have no problems exceeding 1000fpm at the DAs you mentioned. 

This is likely another factor. I had recently done a bunch of reading on this and popped the cowl to check the mag part numbers (and retard breaker timing) vs. the nameplate. Turns out the prebuy/annual shop had set the timing at 20, although the mags part numbers would have been more appropriate for 25BTDC. I worked with my mechanic recently to check the timing (20deg confirmed), and then re-time them to 25deg (with appropriate paperwork as recommended by other threads on this topic.

I'm guessing this did help my performance a bit although I didn't do the methodical testing I should have on flights prior to this adjustment, so it's hard to say exactly how much it helped. Either way, your point about the book numbers assuming 25BTDC is definitely a good one.

Edited August 4, 2022 by 802flyer