TKS speed by the numbers....something going on, and it isn’t the good kind.

[Schllc]

I flew back to the birthplace of my baby last week to have the flap issue the ultra’s have been plagued with rectified...The Mooney factory has figured out a fix for any of you still struggling, and I’d advise you to contact them if you need if fixed...

now to the real issue....

I had to manually move the flaps from the down position on my first flight in the plane to get to the factory and I noticed that the speeds were way off of all the other acclaims I have flown. 
I attributed it to the fact that the flaps may have been a bit draggy, and was expecting the flight home to be a joyous occasion.

However, the return flight it is still WAY below what I would expect.  I know that tks birds are a bit slower than AC birds and yet a bit slower compared to to AC acclaims, I’ve owned them all....
It is about 15-20 knots off at all altitudes from my previous experience. 
Fuel flows, MP, and rpms are all where they should be, just not getting the speed I should be and I am at a loss at where to start for something this large. 
No dramatic tendencies when I go hands off in level flight. Slight roll to the right, but nothing alarming. 
I also tried laying into the rudder each way in cruise to see if I picked up a little speed there either way and no joy. 
I did switch from pitot to static and saw a 10 knot jump but there is always a noticeable delta there...

i am really perplexed at where to look.

[exM20K]

Easiest thing to test is instrumentation.

I'd start with a three leg GPS test.  There are several spreadsheets published. One is here.

Next, I'd check that the FF, MAP, and RPM are recording accurately.  Best way I know is via FF against the power charts.  Fill, Run a known setting for an hour, re-fill.  If FF is not right, everything is wrong.  I've had a major FF errors due to dirty connectors.

Next step should be to check rigging.  even if the plane flies straight, there could be offsetting mis-rigging maybe.

 

Mine flies 8-10 ish knots off book speed as best as I can tell, but I don't run a book power setting.  at 16,000 - 17,000 I typically see 200-205 TAS at 16.5 GPH.

-dan

 

[BravoWhiskey]

15 hours ago, Schllc said:

i am really perplexed at where to look.

I recently swapped plugs (mine were new but just bad) after a bad runup... the result was I ended up with a significant increase in speed.  At the same FF, MP, RPM I picked up about 12kts.  It was only a 30min maintenance flight so I didnt have time to research the performance delta any further but will do so in a week or so when I get the plane back.  Just a thought... and I believe this is in that TKS Bravo you didn't buy about a year ago.

[Schllc]

2 hours ago, BravoWhiskey said:

I recently swapped plugs (mine were new but just bad) after a bad runup... the result was I ended up with a significant increase in speed.  At the same FF, MP, RPM I picked up about 12kts.  It was only a 30min maintenance flight so I didnt have time to research the performance delta any further but will do so in a week or so when I get the plane back.  Just a thought... and I believe this is in that TKS Bravo you didn't buy about a year ago.

Yes, I went and looked at that one at air mart in Kentucky. 
it was a really nice looking bird.

You obviously had bad plugs, did you have any issue with starting?

[BravoWhiskey]

Took a few spins but it started up just fine.  And ran fine except for the run up / mag check.  I was suspicious of the speed and climb rate at first too.  The last mag check was atrocious and thats when we finally swapped plugs.  When i brought it home it was winter and after overhaul was done it was summer... so i assumed performane difference was weather associated.  When i put the new plugs in it started on first rotation, 100rpm mag drop with about 10rpm difference.  Climbed much better and got more speed out of it. 

[mike_elliott]

17 hours ago, exM20K said:

Easiest thing to test is instrumentation.

I'd start with a three leg GPS test.  There are several spreadsheets published. One is here.

Next, I'd check that the FF, MAP, and RPM are recording accurately.  Best way I know is via FF against the power charts.  Fill, Run a known setting for an hour, re-fill.  If FF is not right, everything is wrong.  I've had a major FF errors due to dirty connectors.

Next step should be to check rigging.  even if the plane flies straight, there could be offsetting mis-rigging maybe.

 

Mine flies 8-10 ish knots off book speed as best as I can tell, but I don't run a book power setting.  at 16,000 - 17,000 I typically see 200-205 TAS at 16.5 GPH.

-dan

 

open the alt static, Dan

 

[carusoam]

One thing MSers do when looking for speed….

Get out the travel boards and check the rigging…

Some people have unknowingly had their rigging changed over the years, or by prior owners…

 

If you can get that done at the factory… or by somebody with the tools and the skill set…. That would be cool.

Best regards,

-a-

[Mcstealth]

On 1/15/2022 at 3:51 PM, Schllc said:

 

What was the outcome?

[Schllc]

Nothing new to report.  I haven’t had an opportunity for another ,one flight. 
I did check my speeds with the stratus and it checks out so I don’t believe  it’s instrumentation. 
Hoping to fly formation with a friend to see if they can see something hanging out there...

[exM20K]

54 minutes ago, Schllc said:

Nothing new to report.  I haven’t had an opportunity for another ,one flight. 
I did check my speeds with the stratus and it checks out so I don’t believe  it’s instrumentation. 
Hoping to fly formation with a friend to see if they can see something hanging out there...

I’ll be at F47 tomorrow.  Come on over, and we can do some air work.

-dan

Edited February 7, 2022 by exM20K

[carusoam]

MSers are sooo capable!

Go MS!

-a-

[Schllc]

I’m at Kapf so it may be a little far for me to do right now, but thanks for the generous offer. 

[M20TN_Driver]

Did you ever get this issue sorted?  Mine is a TKS model (much needed out here near lake tahoe).  I think my acclaim is def slower than book numbers, but how far off I have not tried to quantify.  I just flew back from Park City and I was at 13k flying LOP 14.7gph and 2400 getting 180kts ground speed.  Zero wind component.  I don't think I took note of TAS.

[LANCECASPER]

1 minute ago, M20TN_Driver said:

Did you ever get this issue sorted?  Mine is a TKS model (much needed out here near lake tahoe).  I think my acclaim is def slower than book numbers, but how far off I have not tried to quantify.  I just flew back from Park City and I was at 13k flying LOP 14.7gph and 2400 getting 180kts ground speed.  Zero wind component.  I don't think I took note of TAS.

What was your Manifold Pressure?