Speed for an E Model

[KSMooniac]

Brian, I'm just down the road from you in Wichita and would be happy to help/fly just about anytime.  Another Mooney buddy here and I are even talking about a BBQ run to Paola (K81) very soon...possibly this weekend.

Even if your ASI bench-checks OK, you could still have something amiss with the rest of the system.  You might have to simply trace the pitot and static lines all the way thru the airframe and look for a problem.

[flight2000]

Would love to go and meet you guys, but my aircraft will be captive for about two more weeks.  I'm excited to see the new panel instead of the old shotgun.  I'll take you up on that offer once the dust settles after the paint shop does their thing in February.

Brian

[Piloto]

Quote: eaglebkh

I'll have to say, though, in the picture the IAS appears to be very high in the yellow arc and I never see that at 3500' - maybe with everything firewalled.

 

 

[Immelman]

I have a 66E

+cowl closure, 1-pc belly (I don't believe the latter should add any speed)

- a bunch of antennae, and my LMG hangs down just a hair into the slip stream, probably costing me speed

THe speed tests I have done have been at higher altitude -- the first test @ 7500 was on a warm day and thus I think about 2000' above the optimal speed altitude

Speed test 1:

Pressure altitude    7500       
OAT    17C       
MP    23.75       
RPM    2500       
Density altitude    9428       
           
Headings    Ground speed KT    IAS mph    IAS KT
N    153    151   
W    143    150    130.25
S    142    150    130.25
E    151    150    130.25
           
TAS (calculated on IAS)    149.7       
TAS (calculated on gnd speed)    147

Solo weight, full fuel
Smooth air (consistent IAS)
Ram air on
Indicated RPM = 2450 (tach reads 50 low)
Mixture leaned to 100+ ROP

---

Speed test 2: I was crossing the Sierra and had leaned TO peak and wondered what my economy was, so I did a 4-way speed test run and noted the numbers. This, I think, is where our airplanes do well in terms of efficiency

Date    11/1/2009       
Conditions:           
Pressure altitude    13111       
OAT    0C       
MP    19       
RPM    2500       
Density altitude    14400       
Fuel flow    7.5-7.8gph       
           
Headings    Ground speed KT    IAS mph    IAS KT
N    134    131    113.75
W    123       
S    147       
E    152       
           
TAS (calculated on IAS)    141.5       
TAS (calculated on gnd speed)    139       
           
Notes           
Solo weight + 30 lb, 14 gallons off of full fuel           
Smooth air (consistent IAS)           
Ram air on           
Indicated RPM = 2450 (tach reads 50 low)           
Mixture leaned to peak           

[Cruiser]

I might have misread something in your picture. My comments are based on the information you have there. I looks like you indeed were very straight and level at the time the picture was taken. AI and T&B are perfect. If your DG was set correctly you are on a heading of 100° and it looks like the CMG on the Garmin is 124° (hard to see)  I can make out the 183 assuming that it is in kts. and the 160 kts on your inner ring of the ASI. Also your Alt shows 3500'. With that info using an E6B your wind speed and direction should have been from 11° @ 74kts.

I would agree with others here ...... take a good look at the static system and the ASI.

 

TomK

[HRM]

Quote: flight2000

Question for my fellow E owners.

Is my bird that much more different in the fact that I can routinely get 155 kts indicated at 3500 ft and 25 squared?  I haven't had the opportunity to go higher yet because of the shorter trips I've been taking and the class B that sits over my airport. 

The ferry pilot that brought up my plane from Texas in December told me he was seeing 160 kts indicated at 7,000 ft (he's a 201 owner).  The only mods I have on the plane are the 201 windshield and the lower cowl enclosure (unless you count the GAMIs that are installed as a mod as well).  I'm only seeing fuel burn around 9-10 gph so I'm not burning the tanks up seeing these speeds.

Thoughts?

Thanks,

Brian

'67 E Model

[eaglebkh]

Quote: HRM

I am counting on the fact that the Mooney engineers allowed for at least 10% on Vne.

[Immelman]

Regarding Vne...here is a little bit of extra information:

I remember reading somewhere that control surface flutter phenomena are based on true, not indicated airspeed. At a certain true airspeed, flutter can start to occur and that would impose forces on the airframe which might ruin your day quickly.

The take-home I got from this was that while Vne should always be respected, your margin of safety when descending from a high altitude at airspeeds close to Vne might be much less than when close to sea level density altitudes.

With all this said -- one more speed experiment, in addiiton to the ones I posted above: Down low near sea level with everything wide open I can see somewhere between 180-185mph indicated, Vne=189. However, I regard this as pretty useless since its at close to 100% power, full rich, and thus close to 18gph!

Fly safe!

 

[scottfromiowa]

Has anyone read the MAPA article n the M20E by Kromer?  I always fly at 25 squared and lean to 50 degrees rich of peak...I have NO cooling issues and fuel burn is fine...and as Jack says plane was designed for full throttle all the way to TBO and you get better cooling in the climb, so why sacrifice airspeed?

[Guest Anonymous]

Quote: Cruiser

I might have misread something in your picture. My comments are based on the information you have there. I looks like you indeed were very straight and level at the time the picture was taken. AI and T&B are perfect. If your DG was set correctly you are on a heading of 100° and it looks like the CMG on the Garmin is 124° (hard to see)  I can make out the 183 assuming that it is in kts. and the 160 kts on your inner ring of the ASI. Also your Alt shows 3500'. With that info using an E6B your wind speed and direction should have been from 11° @ 74kts.

I would agree with others here ...... take a good look at the static system and the ASI.

TomK

[flight2000]

Static system is fine.  They traced all of the lines while they had the interior apart and found no leaks or issues.  All of the tubes are perfect and no crimps anywhere. 

The AI and ASI were sent out for rebuild and recalibration.  The ASI was reading 7kts high, so the instrument shop redid the calibration.  The AI was getting ready to fail from worn parts, so I had them overhaul it as well.  Basically a brand new AI at 1/3 the cost of a new one.

I should get her back next Friday finally.  I'm looking forward to seeing the final product after several long weeks while getting the instrument panel facelift and new radios installed.

Brian

[airkraft]

HRM,

Maybe I missed something, but ground speeds are completely irrelevant to this discussion.  Your GPS and the tracking services only know speed over the ground;  not indicated or true airspeed.

[HRM]

Quote: airkraft

HRM,

Maybe I missed something, but ground speeds are completely irrelevant to this discussion.  Your GPS and the tracking services only know speed over the ground;  not indicated or true airspeed.

[airkraft]

HRM,

Uh, yes, as I agreed with Magnus earlier in this discussion, an average of the four cardinal ground speeds is one of the best ways to establish true airspeed. 

[HRM]

Quote: airkraft

HRM,

Uh, yes, as I agreed with Magnus earlier in this discussion, an average of the four cardinal ground speeds is one of the best ways to establish true airspeed. 

[airkraft]

HRM,

I should have re-specified averaging GPS ( or radar) groundspeeds.  This WILL provide a very accurate measure for true airspeed at the particular power setting and density altitude.    

[rob]

The 4 cardinal direction groundspeed average will not be as accurate as a little simple trig (the formulas are well published and easy to locate) on the same four course run. Do yourself a favor and do the real math.

[Magnum]

Quote: rob

The 4 cardinal direction groundspeed average will not be as accurate as a little simple trig (the formulas are well published and easy to locate) on the same four course run. Do yourself a favor and do the real math.