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1969+ M20F speeds


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3 hours ago, Shadrach said:

4 way runs are optimistic.  The most recent I did yielded an average of 156kts at 6500ft.  I don't think my bird will actually do that at 6500.  I think  Dr. Rogers's 3 way run does a better job of minimizing error.

BINGO!

Dr. Rogers 'horseshoe' (3 way) method is the way to measure speed accurately.

His paper is excellent but you do need to ok with basic algebra to appreciate it.

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53 minutes ago, MikeOH said:

BINGO!

Dr. Rogers 'horseshoe' (3 way) method is the way to measure speed accurately.

His paper is excellent but you do need to ok with basic algebra to appreciate it.

Is there a copy of the paper around somewhere?  Would love to read it.

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14 hours ago, Hank said:

I'm shocked at the low speeds some of these Fs are making! A friend used to have a 75 F with no step, and he walked away from my C; but I would walk away from some of these Fs while some I would run away from.

My C gets ~147-148 KTAS at altitude (7500-10,000 msl], WOT- / 2500. And I have a 3-blade Hartzell speed brake on the nose, guppy mouth closure and 201 windshield. AND a fixed step.

I generally indicate ~145mph like this, with groundspeed envelope of 68-186 knots. When I get it back from the shop, hopefully next week, I will do a 3-leg GPS groundspeed check.

Can't believe I'm that much faster than so many F models . . . . .

Holy cow.  doesn't that make half a year of your plane being in the shop?    I would say something like your plane can only go zero because it is in the shop, but that would be mean.   I thought my month and half long annual was bad.  Mostly my feet dragging. Some of it the fuel servo shop.

Edited by Yetti
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3 hours ago, Yetti said:

Holy cow.  doesn't that make half a year of your plane being in the shop?    I would say something like your plane can only go zero because it is in the shop, but that would be mean.   I thought my month and half long annual was bad.  Mostly my feet dragging. Some of it the fuel servo shop.

Let's not talk about time delays . . . 10 freaking weeks for an annual, then a month wait to get into an MSC to correct things they buggered up and/or did wrong . . . Only been at Cole's for three weeks, not too bad at all. Catching up on an AD or two also, a benefit of experienced people seeing the plane. 

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15 hours ago, Shadrach said:

4 way runs are optimistic.  The most recent I did yielded an average of 156kts at 6500ft.  I don't think my bird will actually do that at 6500.  I think  Dr. Rogers's 3 way run does a better job of minimizing error.

Definitely agree, but nobody else seems to understand this!  The 4 way runs are close if there isn’t a real strong wind.  I usually do both and find them within 1 knot so the 4 way is probably close enough if it’s easier to understand.

The 4 way will always give a slightly higher speed because the wind drift is being added to your forward speed.  It’s slight, but it’s there.

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9 minutes ago, Ragsf15e said:

Definitely agree, but nobody else seems to understand this!  The 4 way runs are close if there isn’t a real strong wind.  I usually do both and find them within 1 knot so the 4 way is probably close enough if it’s easier to understand.

The 4 way will always give a slightly higher speed because the wind drift is being added to your forward speed.  It’s slight, but it’s there.

It is close but people really like to split hairs over a few knots. I’ve ceased to obsess over it. I know my bird is a 150kt+ bird because I often top 150 westbound into known headwinds (admittedly very light). That’s good enough for now.

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On 6/19/2019 at 7:55 PM, Shadrach said:

My bird is a box stock 67F.

What part of "Folks with a '69 or newer M20F" and "later, 'cost-cutting' Fs" was confusing to you? ;) The '67 had a different wing, retractable step, more flush rivets and inspection plates, etc. Hard to get a baseline for a '69 or later with data from just-different-enough-to-be-significant earlier models polluting the sample... :D

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22 hours ago, TTaylor said:

It is hard to get the O-360 under about 69% power with WOT.

Not where I'm flying: "Usual cruising altitudes are in the 9,000-12,000' range (SoCal, almost all the MEAs around here are 10,000+)..."

For most of the flight from Goodyear to Lompoc Monday, I was seeing between 57-59% power on the JPI (and yes, it's calibrated).

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14 minutes ago, chrixxer said:

What part of "Folks with a '69 or newer M20F" and "later, 'cost-cutting' Fs" was confusing to you? ;) The '67 had a different wing, retractable step, more flush rivets and inspection plates, etc. Hard to get a baseline for a '69 or later with data from just-different-enough-to-be-significant earlier models polluting the sample... :D

I'm sorry, I missed that. Most guys that own the later birds scoff at the idea that there is much if any difference in speed. I tend to agree. It's mostly the fit and finish that looks a bit better (though there a certainly signs that all of them are hand made).  I thought is would be an additional data point.  I seriously doubt that flush rivets are cause of of my birds slight speed advantage.

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16 minutes ago, chrixxer said:

Not where I'm flying: "Usual cruising altitudes are in the 9,000-12,000' range (SoCal, almost all the MEAs around here are 10,000+)..."

For most of the flight from Goodyear to Lompoc Monday, I was seeing between 57-59% power on the JPI (and yes, it's calibrated).

yup and the DA's you're flying are probably significantly higher yet...

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4 minutes ago, Shadrach said:

I'm sorry, I missed that. Most guys that own the later birds scoff at the idea that there is much if any difference in speed. I tend to agree. It's mostly the fit and finish that looks a bit better (though there a certainly signs that all of them are hand made).  I thought is would be an additional data point.  I seriously doubt that flush rivets are cause of of my birds slight speed advantage.

It's only in the title of the post ... 1969+ M20F speeds ... ;) 

My understanding is, a combination of things (retractable step, twisted wing, more flush surfaces, etc) cumulate into a speed advantage, apples-to-apples. I only have about 6 hours in a couple of '67s, though, and one was heavily modified (IO-360-ES engine, 201-style fairing / windshield, etc). The other was mostly stock IIRC, but I spent most of the flight figuring out the PC system, the GTN650, dodging airspace (and getting a surprise Bravo clearance), etc. :) So I can't say for sure.

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1 minute ago, chrixxer said:

It's only in the title of the post ... 1969+ M20F speeds ... ;) 

My understanding is, a combination of things (retractable step, twisted wing, more flush surfaces, etc) cumulate into a speed advantage, apples-to-apples. I only have about 6 hours in a couple of '67s, though, and one was heavily modified (IO-360-ES engine, 201-style fairing / windshield, etc). The other was mostly stock IIRC, but I spent most of the flight figuring out the PC system, the GTN650, dodging airspace (and getting a surprise Bravo clearance), etc. :) So I can't say for sure.

I didn't take it as the exclusion it was meant to be...good luck getting yours sorted.

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On 6/20/2019 at 3:26 PM, Igor_U said:

I see, from your avatar, that your F is heavily modified. :D

What's your True speed?

140-145 down low and 160-170 up high.  Around FL190 is the sweet spot. 

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Hrm. Okay. So, just me and 40 gallons of fuel (a bit under 2200 lbs), at 12,500' (DA: 13,770'), 58% power (18.7 MAP with Power Boost on, 2500 RPM, 9.5 mph), ~136 ktas using GPS groundspeed. (Book says I should be at 169 mph TAS (147 ktas) at 2300 lbs at 12,500, 19", 2500 rpm; mine doesn't go past 12,500.) 

The air was bumpier lower, so I don't have as much confidence in the numbers, but here goes:

At 10,000' (DA 11,275'), 63% power (20.6 MAP w/ ram air, 2500 RPM, 10.3 mph), 132-134 ktas. (Book says I should be somewhere between 167-172 mph (10,000', 20"-21", 2500 rpm, 10.3 mph) and 169 mph (12,500', 19", 2500 rpm, 9.5 gph) TAS (145-149.6 ktas).)

At 7,500' (DA 8770'), 65% power (21.5" MAP w/ ram air, 2500 RPM, 10.9 gph), 137.9-138.7 ktas. (Book says 165-169 mph (21"-22", 2500 rpm, 10-10.5 gph, at 7,500') to 172 mph (21", 2500 rpm, 10.3 gph at 10,000') (143.5-149.6 ktas).)

That's way lower than it should be, no? (This was over KVCV and KAPV about 4 p.m. today. Pressure was 29.96" Hg., temperature ranged from 13°C OAT (7,500') to 8°C (10,000') to ... I didn't write it down at 12,500'. Meh.

Warm bump day, I'll re-run the test eventually. But it still appears to be really, really slow, compared to book numbers and what folks are reporting here. Like, ~10 knots slower than it should be, especially with all the 201 mods done to her.

 

Edited by chrixxer
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How did you measure speed?  Did you perform a careful 3 or 4 way check, or just looked at the GPS groundspeed?

Also, it looks like your book numbers for 10,000 wouldn't apply since you were at 11,275 DA.

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How did you measure speed?  Did you perform a careful 3 or 4 way check, or just looked at the GPS groundspeed?
Also, it looks like your book numbers for 10,000 wouldn't apply since you were at 11,275 DA.


As careful a check as I could, with the wind and mild turbulence. Waited until established, gave it a good 5+ minutes on each heading and noted the numbers when as stabilized as it was going to get. All three altitudes, 3-4 directions at each, took a little over an hour.

The difference between book numbers and DA are why I provided the ranges (i.e., 10 and 12.5 for the 11.3 ground speed check) - and even if you look at the higher altitude numbers, I’m still way off. :(


Sent from my iPad using Tapatalk
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5 hours ago, chrixxer said:

 


As careful a check as I could, with the wind and mild turbulence. Waited until established, gave it a good 5+ minutes on each heading and noted the numbers when as stabilized as it was going to get. All three altitudes, 3-4 directions at each, took a little over an hour.

The difference between book numbers and DA are why I provided the ranges (i.e., 10 and 12.5 for the 11.3 ground speed check) - and even if you look at the higher altitude numbers, I’m still way off. :(


Sent from my iPad using Tapatalk

 

You’re plane is definitely on the slow side for any 200hp Mooney.  Could be a number of factors contributing has the ignition timing been verified? If the data plate is stamped 20° you’re already at a disadvantage because the POH performance numbers were derived when the planes were spec’d to 25°. If the tech installing the mags was the slightest bit apathetic about precision you could be flying an engine that’s < 20°. You will feel that in climb but also disproportionately as cruising altitude increases. There is a reason road and drag racers run 8 to 10° of advance when racing at high-altitude tracks.

 

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1 hour ago, ArtVandelay said:

I’ve been told legally you can advance the timing to 22°, ie it’s within 2° .
Don’t forget warmer temperatures and humidity reduce engine horsepower.


Tom

I’ve also heard the timing tolerance is +/-2° but I’ve not seen it in writing.

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