Improved speed documented

[Hank]

dp

Edited August 16, 2018 by Hank

[Mooneymite]

3 hours ago, bluehighwayflyer said:

Oh, I almost forgot. It doesn't "make book" either. 

If it doesn't make book, Mooney should have to make up the fuel burn difference to you like the big aircraft manufacturers do.

It's only fair.  

[mike_elliott]

4 hours ago, teejayevans said:

But it will now be slower, might explain some of your past performance.

Nope, not at all, it now directs flow over the cylinders instead of back to the accessory case area where the seal was drooping. Air can now exit properly instead of damming up.

Its a few knots quicker now, but not because of that, because of the new paint most likely. 

 

 

[Boilermonkey]

My datapoint w/ detailed info.  
Aircraft: 1968 C model
Cruise speed: 147 kts, most typical speed observed over 500hrs of flying (not transient best speed seen during atmospheric phenomena)
Method for determining airspeed: TAS on Aspen PFD, minus 2-3 kts (Aspen doesn't account for CAS correction)
Altitude: 7000-10,000ft
Power settings: 25k rpm, just shy of WOT, carb heat cracked slightly open
Fuel flow: 9-10gph
Mod from stock - potential speed benefit:   (1) flap gap seals - slight (2) brake reversal - slight (3) Lasar cowl closure - likely none (4) LASAR 201 wing tips - likely none (5) Hartzell Top Prop - dunno (6) Knisley Exhaust -dunno (7) Millennium cylinders - likely none
Comments
-I listed mods that the plane came with above.  I added the LASAR 201 type windshield after flying it for 200 hours and honestly didn't see a clear increase in speed, though the cabin is noticeably quieter and the extra visibility is nice.  
-My C seems conclusively faster than a typical stock one by 3-4kts, but it is not among the fastest.  I've no clue which if any of the mods account for the improvement. 
-I hope to get the illusive 150kt with the Sabremech cowl.

Why the partial carb heat?

Sent from my SM-G960U using Tapatalk

[ArtVandelay]

Power settings: 25k rpm, just shy of WOT, carb heat cracked slightly open

25,000 RPM! Not going to make TBO at that RPM.

[Hank]

1 hour ago, Boilermonkey said:

Why the partial carb heat?

Sent from my SM-G960U using Tapatalk
 

Partial carb heat, like the slightly cocked throttle plate, is to improve atomization of the fuel for more even burn. It can help the carbed engine run LOP sometimes, too.

[DXB]

1 hour ago, Boilermonkey said:

Why the partial carb heat?

Sent from my SM-G960U using Tapatalk
 

what Hank said above - though I can't say I've ever noticed much difference in mixture distribution

54 minutes ago, teejayevans said:

25,000 RPM! Not going to make TBO at that RPM.

Problem lies in my poor math education, not my prop governor 

[ArtVandelay]

Nope, not at all, it now directs flow over the cylinders instead of back to the accessory case area where the seal was drooping. Air can now exit properly instead of damming up.

I’m not sure that’s how it works. When you close the cowl flaps you are damming up the airflow, but you go faster.
I think the dam results in air backing up, then essentially pushing airflow aside and flowing unrestricted past the aerodynamic fuselage, instead of past all the unaerodynamic parts of the engine.

[MBDiagMan]

9 hours ago, Marauder said:

 

The Aspen uses the winds, ground speed from the GTN, its own airspeed and altimeter to come up with the TAS.

I have been flying behind the Aspen for 6 years. The TAS has always been within a knot of any multi-leg speed checks I have done.


Sent from my iPad using Tapatalk Pro

 

Outstanding.  There is no reason the 430W couldn’t do that.  The information is available for them to provide that functionality if they would add the code to do and present the calculation results.

[M016576]

23 hours ago, jetdriven said:

Just remember the Aspen calculates true airspeed from the IAS which if you look in the POH reads about 2 to 3kt  high at cruise. CAS is less. 

True- but is the note in the POH related to the mechanical airspeed indicator, or the pitot tube/pitot system itself.  The aspen just pulls off a t in the system- it’s not in “series” with the airspeed indicator.

i don’t have pictures- but anecdotally- my aspen reads spot on with my IFD-440 calculator (you have to manually enter parameters for that- it’s truely a calculator).

[Raptor05121]

On 8/15/2018 at 10:58 PM, gsxrpilot said:

N6XM (may she rest in peace) was a 150+ knot TAS M20C. She had all the 201 mods including cowl, windshield, wingtips, etc, etc, etc. Very few antennas and nothing poking out through the glass, wings, etc. She was light for a C, with 1015 lbs useful load.

 

My plane is very light compared to others, just like N6XM, my useful load is 1,016lbs. Mine can and will cruise 145KTAS all day every day. I've seen as high as 147KTAS according to my E6B when solo. I have zero speed mods, and even sports a slower 3-blade prop.

21 hours ago, David Lloyd said:

The owner's manual for the '65 C Model I had, the performance numbers were wishful thinking at best.  The older books are on this site.  Don't read with a mouthful of coffee. 

 

Not at all. I'm within 1-2mph of my cruise charts given variations of weight.

It seems a lot of people discount weight with speed. Mooney even says in their 1960s owners manual that "Each 100lbs variation of weight will affect TAS by 1.2mph". My plane is pretty well stock. No fancy avionics, no added stuff over the years other than a 3-blade. Mooney's numbers are damned well spot on. Everyone touting they were being liberal with their claims needs to compare their empty weight to when the plane was new. 

[David Lloyd]

Performance charts in the old book list conditions as 2200 weight, standard conditions, best power, full fuel.  That pretty much is one heavy person (210), full fuel (300), 40 pounds of headsets, oil, charts, approach books, a change of underwear and an old Mooney (1650). One point, 7500', full throttle, the chart shows 182 mph (158 knots).

Under those conditions I used to see 140-144 knots.  You, 145-147.  That seems like ways off when we are interested in accuracy.

[ArtVandelay]

Outstanding.  There is no reason the 430W couldn’t do that.  The information is available for them to provide that functionality if they would add the code to do and present the calculation results.

They are looking at adding that to the GTNs.
It needs the outside temperature which it can get from an engine monitor, the IAS from the G5.

[Hank]

14 hours ago, MBDiagMan said:

Outstanding.  There is no reason the 430W couldn’t do that.  The information is available for them to provide that functionality if they would add the code to do and present the calculation results.

The 430 WILL do this, you only have to enter CAS, altimeter setting and OAT. How is this for a 3-bladed C model?

There's just no way for it to get this data from my steam gages . . . .

[Raptor05121]

3 hours ago, David Lloyd said:

Performance charts in the old book list conditions as 2200 weight, standard conditions, best power, full fuel.  That pretty much is one heavy person (210), full fuel (300), 40 pounds of headsets, oil, charts, approach books, a change of underwear and an old Mooney (1650). One point, 7500', full throttle, the chart shows 182 mph (158 knots).

Under those conditions I used to see 140-144 knots.  You, 145-147.  That seems like ways off when we are interested in accuracy.

I see what you are quoting. Look over to the fuel flow- 11.4gph. I'm not sure how you flew your Mooney but I bought mine to save fuel. 11gph on a 180hp engine is quite a lot of power considering they should be burning around 18gph on takeoff from sea level. I pull back and lean very aggressively <75% power to get <9gph. I've never tried pushing knobs forward to see what I could get. Someone here with an engine monitor might be able to verify fuel flow and speeds on that.

But that same chart- (10k) they claim WOT/2300rpm is 168mph TAS (146KTAS) and 9.7gph at ROP. With that same power setting, I routinely pull 143-144KTAS and <9gph LOP (can only calculate block-to-block, no fuel flow onboard).

[Raptor05121]

Just now, Hank said:

The 430 WILL do this, you only have to enter CAS, altimeter setting and OAT. How is this for a 3-bladed C model?

There's just no way for it to get this data from my steam gages . . . .

1

Any EFB will have a E6B function that does the same as well.

[wcb]

On ‎8‎/‎16‎/‎2018 at 7:55 AM, steingar said:

A couple of my pals are touting the LASAR cowl closure mod.  Closes off the bottom of the cowl, improves airflow.  They're claiming several knots for 0.5 AMUs, and I have to admit one of the guys who did this easily keeps up with Js in his E, and I don't think it had that much more done to it.  Any other experiences?

I wish I could say I was flying the fastest C, it just isn't so.  I might have been able to say I flew the prettiest, but Bob Belville has me pretty badly beaten in that category as well.

I would like to see pics or yours.  Why not post in albums?  I know mine is not the "prettiest" but I put some in the album for posterity sake.  I do enjoy seeing the restored ones that I will one day compete with.

 

[FloridaMan]

My M20F is a 158ktas airplane. On cold days, it will cruise in level flight at 5000ft in the yellow arc. It was faster after the engine overhaul than it ever was for the 1000 or so hours I put on the factory engine that came with it. The overhaul shop flow matched the cylinders; I'm not sure if that affected it, but the fuel burn went up slightly and she picked up some speed. It has the LoPresti cowl, 201 glass, GAMIjectors and a powerflow exhaust. 

My rocket will do 158ktas while climbing at 1000fpm. 

[aviatoreb]

6 hours ago, Hank said:

The 430 WILL do this, you only have to enter CAS, altimeter setting and OAT. How is this for a 3-bladed C model?

There's just no way for it to get this data from my steam gages . . . .

How do you get CAS vs IAS for your Mooney?

[aviatoreb]

8 minutes ago, Antares said:

My M20F is a 158ktas airplane. On cold days, it will cruise in level flight at 5000ft in the yellow arc. It was faster after the engine overhaul than it ever was for the 1000 or so hours I put on the factory engine that came with it. The overhaul shop flow matched the cylinders; I'm not sure if that affected it, but the fuel burn went up slightly and she picked up some speed. It has the LoPresti cowl, 201 glass, GAMIjectors and a powerflow exhaust. 

My rocket will do 158ktas while climbing at 1000fpm. 

Show off!

Now my favorite part - no one is talking about - in a rocket (and probably other turbo charged?) it is no problem to climb up to 15 or 17 for a short flight.  On a cold day and a good wind I may to climb to17 for even just a 1hr flight - eg going to Boston or to Hartford over the adirondacks in the winter I consider to be hostile terrain in the winter just because it can be frigid cold in the mountains so I go high to give myself options and I enjoy the atmospherics up high...anyway I have timed climbs to 17 in under 13 minutes.

Edited August 17, 2018 by aviatoreb

[bonal]

I think what matters most is how we fly them, I know I can run harder in winter than on hot summer days and I know my real flight performance is slower than if I'm doing some kind of speed run. We calculate based on known performance but when it comes to actual real world speed the only one that really matters is ground speed. Once you have it then you start making sure your fuel planning is going to work out. For our D/C I plan for 140 to 145 knots and usually get that. Also to consider is how fresh is your engine. Something close to TBO is not likely making book HP.  There are so many variables with these old airplanes anything close to book speeds and you should be happy.

[Hank]

25 minutes ago, aviatoreb said:

How do you get CAS vs IAS for your Mooney?

I do the best I can:  my ASI has knots on the inner ring, plus this page from my Owners Manual:

It ain't perfect, but it's all I got.

[takair]

22 hours ago, MBDiagMan said:

Outstanding.  There is no reason the 430W couldn’t do that.  The information is available for them to provide that functionality if they would add the code to do and present the calculation results.

I’m pretty sure that all of this is available in the existing code.  You just need to add a compatible air data computer.  I think, both  Shadin and Insight used to make compatible air data computers.  Add heading and you have all pieces required.   Often, many of the capabilities of these navigators are not wired during installation.  This can often be part of the difference in quoted installs.

Edited August 18, 2018 by takair
Corrected EI to Insight

[EricJ]

FWIW, an IFD540 and a G5 will do this nicely, too.   I hope folks can zoom on this pic sufficiently to see, but it is computing TAS as well as the current wind aloft and headwind/tailwind component.   It's pretty cool. 

 

[J0nathan225]

semi related question: does the Lasar cowl closure require repositioning the oil cooler?