The Need For Speed

[Smroot]

I am a new Mooney owner and new Mooney pilot.  I just returned to CO from NJ where I purchased my plane.  The first question I have is about speed.  Running 75% power (28" 2600) at 10,500' the hightest KIAS I saw was 135 and TAS 155.  Seems slow and things I have read say it should true 170kts or better at that altitude.  It has TKS but I also talked with the original owner (JZ) and he confirmed that he would see 170 KTAS.  An MTV-12 propeller was added since but that should only account for loss of about a knot from what I read. 

 

Does anyone have any thoughts on this? 

 

Tim

[aviatoreb]

Which model mooney and which engine is it?

[Bob_Belville]

Sounds like the gear was down. 

My old E model trues @ 158 k @ 75% on about 10.5 gph ROP.

 

FWIW The e6b says 135 ias @ 10,500 = 162 at std conditions. 142 ias would be 170. 

[Joe Zuffoletto]

Which model mooney and which engine is it?

 

It's my previous bird: 1998 Encore (M20K). It has the Continental TSIO-360-SB engine.

[jackn]

I have the -SB2 engine & TKS. While flying with my instructor, went to 10.5k and did the 4 compass points GPS test. at 29" & 2500 I was at 170 KTS. That's 2 large guys, 4 gallons tks, & 50 gallons fuel. I suggest you try the GPS method to see if your ASI is accurate. BTW, double check that in cruise you flully closed the cowl flap and TO flaps(don't ask me how I know).

[LANCECASPER]

Yours is an Encore, serial number 25-2029 with TKS, mine is serial number 25-2012, also with TKS. Even with TKS I come within 3 knots of what the POH says without TKS.

 

I think part of your lower speed is your prop. Below is an article from AOPA when the Encore was introduced in 1997. But here is what they found in testing:

 

"Out front, the Encore uses the same McCauley two-blade propeller found on the 252 — much to the surprise of the engineering

staff. After 3 months of testing four other propeller designs from a total of three manufacturers, the engineers concluded that the

original prop delivered the best performance.

 

When I flew the Encore prototype in March, engineer Bowen was testing the three-blade MT composite propeller from Germany

(see " Waypoints: Mooney Gets an Encore," May Pilot). All white, the prop looked great and undoubtedly had the nod from the

marketing staff. However, it delivered the worst cruise performance and had the lowest TBO and highest price. A Hartzell two-blade

and two other McCauley two-blade variants all turned in respectable performance, but the original McCauley design won the heat."

Mooney Encore ARTICLE- AOPA.pdf

[kortopates]

Concur with Bob your TAS cal is low and being above standard probably more like 165 ktas. But that still below expected. My 252 POH value calls for 174 with 1" less MP (78.6%) and really faster if I could determine your DA. I also concur with checking more accurately with GPS tracks and if really off (compared to the other 2 folks with TKS) would look for sources of extra drag i.e., besides cowl flaps, jack it up and see if the gear doors are fully closing (easy to fix) and verify the ball is centered in cruise when you collect data.

Sent from my iPhone using Tapatalk

[Smroot]

Thanks all.  I had read that article about the MT prop and suspect that accounts for some speed loss of it but not 15kts slower.  The MSC that just did the annual assures me the gear doors are fully closed.  They also assured me they fixed the cowl flap indicator but that doesn't work (they do function on the ground though). 

 

I noticed there is about a 1/4" gap between the cowling and the cowl flap door when closed.  Should that be tighter?  I suspect it opens more in a 200mph wind. 

 

I'll gather some more data and report back.

 

Tim

[carqwik]

Perhaps your not running at the proper power setting - meaning that your MP indicator is not accurate?  What kind of fuel flow were you seeing?  IIRC, that engine should run around 12.7 to 13+ gph in normal cruise settings at around 75% power.

[Guest]

I have a two blade prop with logs for the 252 available.

Clarence

[N9405V]

Did you pull the step up?

[Smroot]

The step seems to be stuck in the down position.

[Guest]

The step seems to be stuck in the down position.

A gear up landing will remove it quite nicely!!

Clarence

[aviatoreb]

Bite your tongue m20doc!!!

[jetdriven]

Optimize what you got.  Look at everything. Gear doors closing, number of antennas, aileron, flap, rudder, and elevator rigging.  Door seals. true and correct MP, RPM, and FF readings. Tachs often read 100 RPM high and thats a few knots right there.

 

Another thing, IAS can vary with instrument accuracy, and corrected with that little window thing on the ASI it isnt accurate either. For example the M20J POH shows CAS 3 MPH lower in the cruise range than IAS.  Neither is the 4-heading GPS method people often recommend. Winds aloft bias it low. The NTPS 3-track GPS method entered into the spreadsheet is accurate to 1 knot.

[Smroot]

Cowl flap open and closed. Should there be this much gap when closed? I see a 4-5 knot difference from closed to open.

[jackn]

That really doesn't look right. Here's a photo of mine. When open, the front of the flap is up,inside the cowl.

[aviatoreb]

Cowl flap open and closed. Should there be this much gap when closed? I see a 4-5 knot difference from closed to open.

 

Do you have a picture of the doors closed?

[Piloto]

Tim 

 

You do not mention ground speed. Check the static alternate knob. Cross check with GPS ground speed. This could be related to an air leak either on the static or pitot hoses connection. Also verify flaps retracted position visually, they should line up with the ailerons. It takes about three minutes in level flight to accelerate to final speed.

 

José 

[Smroot]

Do you have a picture of the doors closed?

 

No picture of cowl flap with gear up and doors closed. 

Piloto, I'll post a couple pictures of the G500 in flight.  The numbers all seem to check out according to my calculations.  KTAS plus headwind/tailwind equals GPS Ground speed.  Seems right on. 

[Smroot]

That really doesn't look right. Here's a photo of mine. When open, the front of the flap is up,inside the cowl.

Cowl Flap.jpg

 

Jack,  That looks very clean.  What kind of numbers do you see? 

[jackn]

As I've mentioned. 170Kts at 10,000 at 75% and around 160Kts at 10,000 at 65% that's burning about 12.5 gph. Also, about 2Kts for every 1000 ft increase in altitude.

[aviatoreb]

As I've mentioned. 170Kts at 10,000 at 75% and around 160Kts at 10,000 at 65% that's burning about 12.5 gph. Also, about 2Kts for every 1000 ft increase in altitude.

 

Which is burning 12.5?  170 or 160 kts at 10k?

[Piloto]

If you are using the autopilot when measuring speed it may be inducing an elevator/stabilator divergence. Does the plane pitch up or down when  A/P is disconected? If so try measuring speed in level flight without the A/P.

 

José 

[jackn]

12.5 gph is at 65%. That is the power i use most of the time. LoP doesn't really work on my plane at 20 degrees BTC.