Jayhawk_aviator

M20J Speed Improvement?

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Have a relatively new to me M20J.  Engine is strong with high 70s compression, and prop was just overhauled.  Extensive annual where gear doors / cowl flaps were rigged, and all flight control rigging was checked.
The inner gear doors were not installed when we bought the plane (and the fairing that go in front under the wing are missing as well).  As part o the annual we peformed the SB (forget the number) which removes the ram air (since it doesn't really really do anything on the Js).  The brake calipers are installed in front of the axle...not sure if that is an STC or something else.
Question is this...not seeing near the speeds expected.  I haven't done a true 4 way TAS test yet, but at 9500' (10 deg C) flat out (21ish inches MAP, 2600+ RPM, 10.2 GPH, one on board, 3/4 fuel) I was seeing around 152ish knots.  Book says we should be around 15 knots higher in that configuration.   
Other than the inner gear doors which I understand adds about 5ish knots (?), anyone have any suggestions on what may be happenning and why the numbers are so far off?

Sounds about like a 201 at 9500 + or - a little


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      1 hour ago, Shadrach said:

Here in the lowlands, cruising at anything under 6000' the two 231s I am familiar with run <150kts. 

21 minutes ago, peevee said:

Mmmmno, they run quicker than that down low.

Yeah I don't know how these rumors spread...   My 231 around 6k at full gross is pushing 160 kts (Maybe 158), running lighter and I'm over 160.

Edited by jrwilson

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2 hours ago, jrwilson said:

      1 hour ago, Shadrach said:

Here in the lowlands, cruising at anything under 6000' the two 231s I am familiar with run <150kts. 

Yeah I don't know how these rumors spread...   My 231 around 6k at full gross is pushing 160 kts (Maybe 158), running lighter and I'm over 160.

Not a rumor, but certainly anecdotal.  Directly stated firsthand to me at a Mooneyspace breakfast fly in by a a 231 owner.

I knew of one other 231 owner casually and he has since sold his plane. He had cooling issues he was never really comfortable running over 65% at any altitude.

Certaily the airframe is capable of J speeds at any altitude a J flys but is it prudent t run it that way?

 Would you run 160 at 6000 as a cruise setting? 

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Alright back to J speed improvements.  Haven't done a 3 or four way GPS run after all this as some of these items are being done in the shop now. I'll post when I get accurate data.

1.  Gear doors flush

2.  Moved temperature sensor probe to vent cutout.

3. Remove tie down rings

4. No step

5. No belly strobe, not sure if it ever had one

6. Tightened up and sealed all engine baffling

7.  New inner gear doors with fairings

8.  Donaldson air filter to replace Bracket(currently making this change)

9.  New ignition harness

10.  Replaced champions plugs with Tempest

11. Reworked fuel spider and installed all new fuel injector nozzles.

12. JPI 900 to help better determine %power with fuel flow.

13.  Polished, sealed, and waxed the paint.

14. Going to get rigging checked. Flies straight with ball centered but I have heard stories.....

15. Will get engine mount adjusted to bring up engine about 1/2". It's a little off. 

16.  Removing old Loran antennae and another mystery antennae on the belly.(currently in the shop)

17. Taking off reverse seven antennae and installing new comant antennaes.(modern ones). Looks like they will have less drag but not sure. The reverse sevens look like they would create some turbulence compared to the shark fins.

18. Out weight into the baggage area to move CG rearward.

Im not going to move the VOR antennae from the vertical stab at this point but that is an option.

I'm probably missing something.  

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13 hours ago, Shadrach said:

Not a rumor, but certainly anecdotal.  Directly stated firsthand to me at a Mooneyspace breakfast fly in by a a 231 owner.

I knew of one other 231 owner casually and he has since sold his plane. He had cooling issues he was never really comfortable running over 65% at any altitude.

Certaily the airframe is capable of J speeds at any altitude a J flys but is it prudent t run it that way?

 Would you run 160 at 6000 as a cruise setting? 

Mine has an inter cooler so temps aren’t a problem, especially at 6000.  In fact, in the winter (even in California) I have to keep the cowl flaps closed at 6,000 to keep the cylinder temps (#5 and 6 in the front) up in the green arc. The idea of temperature issues is really related to the GB engine.  Most are LB engines now, which run much cooler, and many 231's have intercoolers, which improve temperatures even further.  So that is a pretty old criticism of 231's, being hot running.    Yes, I do cruise settings 28/25 at 6,000 and that gets close to 160, which is certainly prudent, as my cylinder temps are about 350 or less and TIT is well under 1500...

So you can add that to your anecdotal data set.

 

Edited by jrwilson
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13 hours ago, INA201 said:

Alright back to J speed improvements.  Haven't done a 3 or four way GPS run after all this as some of these items are being done in the shop now. I'll post when I get accurate data.

1.  Gear doors flush

2.  Moved temperature sensor probe to vent cutout.

3. Remove tie down rings

4. No step

5. No belly strobe, not sure if it ever had one

6. Tightened up and sealed all engine baffling

7.  New inner gear doors with fairings

8.  Donaldson air filter to replace Bracket(currently making this change)

9.  New ignition harness

10.  Replaced champions plugs with Tempest

11. Reworked fuel spider and installed all new fuel injector nozzles.

12. JPI 900 to help better determine %power with fuel flow.

13.  Polished, sealed, and waxed the paint.

14. Going to get rigging checked. Flies straight with ball centered but I have heard stories.....

15. Will get engine mount adjusted to bring up engine about 1/2". It's a little off. 

16.  Removing old Loran antennae and another mystery antennae on the belly.(currently in the shop)

17. Taking off reverse seven antennae and installing new comant antennaes.(modern ones). Looks like they will have less drag but not sure. The reverse sevens look like they would create some turbulence compared to the shark fins.

18. Out weight into the baggage area to move CG rearward.

Im not going to move the VOR antennae from the vertical stab at this point but that is an option.

I'm probably missing something.  

You can also have your airspeed indicator calibrated.  Ours was off by as much as 5 or 6 KIAS depending on the speed.  You may be going faster than you think.

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On 9/12/2016 at 2:35 PM, bradp said:

Low hanging speed fruit includes ensuring the gear doors are flush to the lower wing skin and ensure that you are rigged.  

Everyone has their own prerogative but I would advise throwing $$ at avgas or training instead of the elusive 1-2k (or 38kts) speed mod.  

I second the motion.  Getting the gear doors flush adds quite a bit of speed.  Since you are in the airplane, flying at that point, everyone just assumes their doors are good.  I have to nag my mechanic often to check the doors, it makes a difference.

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2 hours ago, Bob - S50 said:

You can also have your airspeed indicator calibrated.  Ours was off by as much as 5 or 6 KIAS depending on the speed.  You may be going faster than you think.

Also manifold pressure and tachometer should be checked.

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On 1/23/2018 at 10:55 PM, Andy95W said:

There is absolutely no way I believe you are getting 140-145 knots in a fixed gear Piper Archer unless you are turbocharged at FL200 or in a dive.

But yes, a 201 will nicely cruise at 155-160 knots which is about 40 knots faster than any Piper Archer that I've ever flown.

I apologize..................I was wondering why you guys were saying Archer so I went back to my post.  I meant Arrow (200 hp, RG). 

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6 minutes ago, Curtis said:

I apologize..................I was wondering why you guys were saying Archer so I went back to my post.  I meant Arrow (200 hp, RG). 

even then it's a stretch for a NA arrow.

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My son and I flew a friend's M20C yesterday to 9500 to see how well it does based on this conversation. Well at 9500 TAS per the Garmin computation (temp and press etc.) was 156..kts leaned to 9.2 Gal/h with 3 people on board and full fuel. This one is about 10 kts faster than the C we used to have.... Hmmm now I know why I should have kept my C back then... From my perspective the small details make the differences in aggregate and this particular airplane has everything (speed mods) and is rigged perfectly (as it should being maintained by its 86 year old owner that used to be in charge of half of all 747s in the PanAm fleet). 

N9738M at 9500 performance run.JPG

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looking at IAS and determining TAS is not accurate at all. For starters, the book shows CAS as ~2 MPH less than IAS at normal cruise speeds.  Then  theres the issue of the accuracy of the airspeed indicator. And winds aloft, and 4-headings added together and divided by 4 doesnt eliminate that error.

(taking the pressure altitude and the temp on the airspeed indicator and lining them up is even worse. I mean, its accurate to 5-10 knots true, but thats the range between a crappy slow airplane and the fastest in the fleet.)

 

fly 3 tracks and put that into the NTPS excel spreadsheet. then take your PA and OAT and figure out your IAS error. Then you'll have a reliable WAG for TAS because your true IAS known.  3-track spreadsheet to quantify speed improvements from mods etc.

 

Edited by jetdriven

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2 minutes ago, jetdriven said:

looking at IAS and determining TAS is not accurate at all. For starters, the book shows CAS as ~2 MPH less than IAS at normal cruise speeds.  Then  theres the issue of the accuracy of the airspeed indicator. And winds aloft, and 4-headings added together and divided by 4 doesnt eliminate that error.

(taking the pressure altitude and the temp on the airspeed indicator and lining them up is even worse. I mean, its accurate to 5-10 knots true, but thats the range between a crappy slow airplane and the fastest in the fleet.)

 

Using GPS on a 4 heading run and averaging the speeds is about as accurate as you can do, is my guess. Even then, turbulence(thermal activity), wind changes, temps, and pressure will effect performance.  I'm just thinking here but flying on the calmest day close to standard conditions will probably yield the best results.

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4 hours ago, INA201 said:

Using GPS on a 4 heading run and averaging the speeds is about as accurate as you can do, is my guess. Even then, turbulence(thermal activity), wind changes, temps, and pressure will effect performance.  I'm just thinking here but flying on the calmest day close to standard conditions will probably yield the best results.

Yep, I plan to do this soon (would have last Friday but was late coming home . . . ) and compare it to the back screen on my 430W.

20170909_092123.thumb.jpg.a227847681a45a9502c0a21343f5d8bb.jpg

Not bad for 180 carburetor ponies . . . .  ^_^

Edited by Hank

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All of these computations are only as accurate as the instruments involved and the accuracy of the airframe systems they’re connected to and in the end TAS makes little difference.

Clarence

Edited by M20Doc

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23 minutes ago, M20Doc said:

. . . in the end TAS makes little difference.

Clarence

But . . . But . . . But as TAS goes up, the headwind leaves you with a higher groundspeed . . . . .

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How about this.....You file a flight plan or maybe just flight following and do the GPS four way method.  You then interpolate your cockpit data including GPS with data from Flight Aware.  If both GPS and Flight Aware are consistent then maybe it is accurate data.  Ive never taken the time to cross check data with Flight Aware and see how it compares frankly.  Nonetheless, if a few of us did this it would certainly add up to some interesting discussions. My plane is still stuck in the shop so hopefully I can provide some "field work data," here soon. 

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flight aware shows 174kt on my plane heading south and the NWS shows a 15 know wind from 330 degrees. point is you cant accurately determine the TAS with that info.  https://flightaware.com/live/flight/N201EQ

its like taking off today, 49 degrees OAT and leveling off at 2500' and setting the power exactly at 25 square.. gosh this week I waxed my plane and took some stuff out the cabin and sprayed WD-40 all over the leading edge like Jose said to, and I'll be....Its showing ten knots faster.  And my GPS is showing 165 knots too, therefore, it must be...

Edited by jetdriven

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On 1/24/2018 at 8:35 PM, INA201 said:

Alright back to J speed improvements.  Haven't done a 3 or four way GPS run after all this as some of these items are being done in the shop now. I'll post when I get accurate data.

1.  Gear doors flush

2.  Moved temperature sensor probe to vent cutout.

3. Remove tie down rings

4. No step

5. No belly strobe, not sure if it ever had one

6. Tightened up and sealed all engine baffling

7.  New inner gear doors with fairings

8.  Donaldson air filter to replace Bracket(currently making this change)

9.  New ignition harness

10.  Replaced champions plugs with Tempest

11. Reworked fuel spider and installed all new fuel injector nozzles.

12. JPI 900 to help better determine %power with fuel flow.

13.  Polished, sealed, and waxed the paint.

14. Going to get rigging checked. Flies straight with ball centered but I have heard stories.....

15. Will get engine mount adjusted to bring up engine about 1/2". It's a little off. 

16.  Removing old Loran antennae and another mystery antennae on the belly.(currently in the shop)

17. Taking off reverse seven antennae and installing new comant antennaes.(modern ones). Looks like they will have less drag but not sure. The reverse sevens look like they would create some turbulence compared to the shark fins.

18. Out weight into the baggage area to move CG rearward.

Im not going to move the VOR antennae from the vertical stab at this point but that is an option.

I'm probably missing something.  

This is a well thought out, robust list. Please let us know what the results are when you get yours back in the air. I flew a great working C for several months recently and with the four headings referencing the gps and cross checking with FlightAware, I determined my TAS at 9000’, 2400 rpms and 21” was about 138 KTAS. A good 10-15 knots slower than the 145-150 crowd. 

When you mention rerigging, what exactly does that mean and entail? Had I known I could’ve turned that C into a 150-155 KTAS airplane I would’ve bought it for myself and done the same thing as you’re doing. 

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On 1/29/2018 at 1:08 PM, Chessieretriever said:

My son and I flew a friend's M20C yesterday to 9500 to see how well it does based on this conversation. Well at 9500 TAS per the Garmin computation (temp and press etc.) was 156..kts leaned to 9.2 Gal/h with 3 people on board and full fuel. This one is about 10 kts faster than the C we used to have.... Hmmm now I know why I should have kept my C back then... From my perspective the small details make the differences in aggregate and this particular airplane has everything (speed mods) and is rigged perfectly (as it should being maintained by its 86 year old owner that used to be in charge of half of all 747s in the PanAm fleet). 

N9738M at 9500 performance run.JPG

This is awesome, what a feat in a C. When you say all the speed mods, what exactly are you talking about? No doubt best bang for the buck in general aviation.

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4 hours ago, Tx_Aggie said:

This is a well thought out, robust list. Please let us know what the results are when you get yours back in the air. I flew a great working C for several months recently and with the four headings referencing the gps and cross checking with FlightAware, I determined my TAS at 9000’, 2400 rpms and 21” was about 138 KTAS. A good 10-15 knots slower than the 145-150 crowd. 

When you mention rerigging, what exactly does that mean and entail? Had I known I could’ve turned that C into a 150-155 KTAS airplane I would’ve bought it for myself and done the same thing as you’re doing. 

Rigging is where the mechanic will put "Travel Boards," or "Rigging Boards," on all the control surfaces which determine if they are within specs.  For example, your flaps could be 1/4" down below spec while your elevator could be a little off to compensate for the flap being down.  This alone could reduce speed but would be unnoticeable in flight because the ball is centered and the plane flies straight.  There are some threads available on rigging.  

 

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