I'm all verklempt. Talk amongst yourselves, I'll give you a topic...

[orionflt]

Carrying what kind of load? The Gs I've seen have significantly less useful load. I would think that at gross, the G would be quite slow compared to the F carrying the same load.

Sorry, I was not clear in my post, I fly a C model not a G.

Brian

[Shadrach]

Sorry, I was not clear in my post, I fly a C model not a G.

Brian

Perhaps someday we will "line them up" and add another data point!

[Bob_Belville]

Somehow, all else being equal, since speed increases at the cube rube of the power increase, if we did I doubt that the cruise speed delta between the various vintage Mooney models would be as great as some want to believe. The greater excess power of the E and F would be expected to have a larger impact on rate of climb than it does on speed. But even this is mitigated to some degree by lower gross weights. The G model, in particular.

I think drag (one kind of) is proportional to the square of speed, not the cube?

 

My old M20E trues 158k @ 70% @ 9500'. See pic. (Caveat, that pic was not taken at GW.) I assume that's faster than a C or G.

[Shadrach]

Somehow, all else being equal, since speed increases at the cube rube of the power increase, if we did I doubt that the cruise speed delta between the various vintage Mooney models would be as great as some want to believe. The greater excess power of the E and F would be expected to have a larger impact on rate of climb than it does on speed. But even this is mitigated to some degree by lower gross weights of the lowered powered models. With respect to the G model (2525 pound gross) when compared to the F model (2740 pound gross), in particular. The fact is, though, that at 50 years of age all else is definitely not equal. I think that this has more to do with the different performance numbers that we experience as a group than do some of the model distinctions.

 

Yes, but why compare at gross? I can say with relative certainty that my plane has spent less than 15% of its flying life at weights within 100lbs of gross.  It's nice to have 1050lbs useful if needed, but a common XC weights for us is <2500lbs (~800lbs of useful load used). When I'm just poking holes in the sky by myself, the whole kaboodle weighs in at <2100lbs and I'm not taking drastic weight reduction measures. I weigh ~190lbs,  30gals of gas and some junk in the baggage compartment.  At around 10lbs per horspower, the plane performs spiritedly.   

[MyNameIsNobody]

What is the ramp check to make the analysis based on? I want to play too...

[Hank]

I think drag (one kind of) is proportional to the square of speed, not the cube?

 

My old M20E trues 158k @ 70% @ 9500'. See pic. (Caveat, that pic was not taken at GW.) I assume that's faster than a C or G.[/QOUTE]

Bob, here's my 3-bladed, therefore "slow", C from 2 weeks ago. Level cruise, 9500 msl, 20"/2500. There's no TAS readout, but for 9500' just add 19% (2% per thousand feet), right? So 144 mph becomes 171 mph, or 149 KTAS. Solo, full tanks, some baggage. My Performance Tables call for 164 mph at 10,000 msl, 20" / 2500 and 2100 lbs.

So your 20 hp is good for 9 knots if I did the math right. I imagine our climbs would be similar. Still not sure how I got the extra 7 mph; I was running 25° ROP.

[Shadrach]

Hi, Ross. All true. I chose gross because it is the great equalizer in order to make my greater point that perhaps condition is getting to be as important as are model distinctions, even from a performance perspective, for much of our aging fleet. We here at MooneySpace are for the most part enthusiasts who invest in and maintain our birds. From what I see on ramps all over the country, however, that is not necessarily the case universally. Boy are there a lot of dogs out there.

I might resemble that remark! I've always focused a great deal on how well the airplane flies and performs. I'm not hugely concerned about aesthetics. With original paint, I am sure that there are many that think my old F looks like a dog!

[Andy95W]

Ross- nice original paint.

Not sarcasm. I actually appreciate the original paint jobs.

[Bob_Belville]

Hi Hank, You really need OAT to get to TAS from IAS. (actually CAS). This calculator:

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

• says your 144 cas is 170 tas, (148k) I suppose at standard temp.
• Your 20/2500 should be close to 70% at 10,000'.  
• I have a OM for a '66 M20C which shows 176 mph (153k) TAS cruise @ 10,000'; 2200#; 20.25/2500. (Best Power & 10.6 gph) Owners Manuals from that era might be a little "optimistic".

 

FWIW, I seldom spend more than 45 seconds at Vy after take off. When I get to about pattern altitude I drop the nose to about 120k (135-140 mph) for engine cooling and visibility. So real world for me is about 500 fpm in cruise/climb mode. But if I had a more efficient cowl (M20J or Lopresti) I could climb at over 1000 fpm.

[Shadrach]

Ross- nice original paint.

Not sarcasm. I actually appreciate the original paint jobs.

My take is that most of no one really sees the paint when I'm using the plane. The paint is in ok shape, but the factory put it on super thin in the 60s. I can actually see the primer through it on the aft part of the belly. We've all heard of a 20/20 paint job (looks good from 20 feet at 20mph). We'll call mine 200/200...

https://m.youtube.com/watch?v=pNvAMe1i7jE

[bonal]

Shad it happened so fast I had to watch it twice. Mine gets 149 knots on a 3 heading gps. I think our vintage birds do pretty darn good.

[Shadrach]

If you watch in HD you can see me in steep descending left turn before lining up for the pass.  Winds were at my back; as I recall I was seeing about 175kts on the GPS as I gently initiated the climb.  

 

The sound makes me chuckle; I think the combination of echo off the building and doppler effect make it sound mean for a 4 banger...

[MyNameIsNobody]

Definitely better in HD. +1 on Sound. Yummy.

[Bob_Belville]

I have always read cube, Bob, but will gladly defer to you. 

More than you want to know:

R ∝ v²  (Resistive Force is proportion to velocity squared.) 

The full explanation provides more subtle factors. 

http://physics.info/drag/

[Bob_Belville]

Ha! Thanks, Bob. You are right, though. This is more Erik's speed and way over my head. This one is more manageable. There are others if you search on "speed increases at the cube root of power".

http://www.experimentalaircraft.info/articles/aircraft-drag-reduction.php

Yeah drag is proportions to the square of the speed but delta speed is proportional to the cube root of delta hp.

[Guitarmaster]

Yeah drag is proportions to the square of the speed but delta speed is proportional to the cube root of delta hp.

 

 

IS this discussion in Latin??  Because I understand very little of what you are saying!  LOL!  

[MyNameIsNobody]

No, it is engineer speak. To the unknowing it sounds like adults talking on Charlie Brown cartoons...

[Guitarmaster]

Push throttle forward, go faster and make more noise.  Pull throttle back, go slower and make less noise.

 

[Hank]

Yeah drag is proportions to the square of the speed but delta speed is proportional to the cube root of delta hp.

Here you go, Guitar, my best Engineer-to-English translation:

At any particular speed, there is a certain amount of drag. Increase speed, drag will increase. The drag equation uses (speed squared), so if you double your airspeed, drag will increase by four times; triple your speed, drag will increase nine times.

There is a similar relationship between horsepower and speed. One amount of horsepower gives a certain speed. To increase speed requires more horsepower. To double the speed, you must cube the power--two cubed is (2 x 2 x 2) = 8 times the power. The equation works in reverse, too, but you must take a cube root (similar to a square root, but one more time). If you double the power, the expected speed increase is (cube root of 2 = 1.26), so 100% more power will give you 26% more speed.

The kicker is how much more fuel is required to reach double the power . . . And increase speed by one quarter.

--an Engineer with two Degrees

[Bob_Belville]

Here you go, Guitar, my best Engineer-to-English translation:

At any particular speed, there is a certain amount of drag. Increase speed, drag will increase. The drag equation uses (speed squared), so if you double your airspeed, drag will increase by four times; triple your speed, drag will increase nine times.

There is a similar relationship between horsepower and speed. One amount of horsepower gives a certain speed. To increase speed requires more horsepower. To double the speed, you must cube the power--two cubed is (2 x 2 x 2) = 8 times the power. The equation works in reverse, too, but you must take a cube root (similar to a square root, but one more time). If you double the power, the expected speed increase is (cube root of 2 = 1.26), so 100% more power will give you 26% more speed.

The kicker is how much more fuel is required to reach double the power . . . And increase speed by one quarter.

--an Engineer with two Degrees

In even simpler words: it is expensive to cruise @ over 200 kts and really expensive to cruise at 300 kts.

[Hank]

Let's see, I generally cruise at 140 kts. So (200 - 140) / 140 = 43% increase. That's (1.43)^2 = 2.04 times the drag, and additional required power would be (cube root extra HP) = 60 or my brain hurts, I've done something wrong, it can be 216,000 hp to get 60 more knots from my plane.

But let's look at Rockets, they can run 200 knots using 310 hp and 20+ gph. Think I'll stick with my 180 hp, 9 gph and no-turbo plane for now. (310 - 180) = 130 more hp; cube root of 130 = 5? Yep, 5 x 5 x 5 = 125. Something ain't right here, Bob!

Ah, it's proportional! Not the raw number! Dummy . . .

To go 200 knots is 60 more hp, so 60 / 180 = 33.333%. Now the cube root of 0.33333 = 0.69, or 69% more power. Rockets, however, are Mooneys, and get a partial pass on drag, so they can do it with only 60% more power but more than double the fuel.

Unless I need to dig through the Performance Tables and find the actual percent power used in each situation. I'm not up for that right now.

[carusoam]

Partial pass X 3 for Rockets...

1) Their inherent drag is minimized because they are Mooneys with low cross sectional area and enhanced aerodynamics.

2) Their power is maintained at altitude because they are FI and turbocharged.

3) Their real drag is really minimized by flying deep into the low density flight levels.

Don the O2 masks and find some tail winds. No math required.

Go Engineers!

-a-

[eman1200]

I had to fly to N Myrtle in a Cherokee. Now THATS a drag.

Actually it's not, it was still a blast.

[MyNameIsNobody]

Here you go, Guitar, my best Engineer-to-English translation:

At any particular speed, there is a certain amount of drag. Increase speed, drag will increase. The drag equation uses (speed squared), so if you double your airspeed, drag will increase by four times; triple your speed, drag will increase nine times.

There is a similar relationship between horsepower and speed. One amount of horsepower gives a certain speed. To increase speed requires more horsepower. To double the speed, you must cube the power--two cubed is (2 x 2 x 2) = 8 times the power. The equation works in reverse, too, but you must take a cube root (similar to a square root, but one more time). If you double the power, the expected speed increase is (cube root of 2 = 1.26), so 100% more power will give you 26% more speed.

The kicker is how much more fuel is required to reach double the power . . . And increase speed by one quarter.

--an Engineer with two Degrees

Wa Wa Wa Wa Wa Wa....

What?-Lucy, Snoopy, Linus, Charlie, PigPen, Schroeder...and me.

[MyNameIsNobody]

Mooney's RULE.

Engineer's...drool.