201 not meeting performance expectations

[Jeff_S]

That's a lot of freakin' math! I have to admit I calculate TAS the easy way: the Shadin air-data computer readout on my Garmin 480. Although even that is subject to instrument errors, I'm sure, so it's just a good estimate. I was flying in Colorado this summer with a CFI and the air-data was showing a 15 knot cross-wind, and the CFI just swore up one side and down the other that there was no way we were in that much wind because he wasn't seeing the drift. I've thought about getting it recalibrated but decided whatever money that would cost wasn't worth the few knots I'd likely pick up in precision.

[Hank]

As an engineer, that's neither "a lot of math" nor is it even difficult math.

However, I found an easy, simple spreadsheet a year or two ago that does all of this for you. It requires three GPS groundspeeds and tracks, and spits out your actual airspeed and the wind speed and direction. Don't know if I can post it here or not; it's a whopping 5K file size, and the whole thing is visible even on a phone-sized screen

Nope, attachments don't work. I can email it if you want it. Sign up now, and I'll send it out to everyone in a few days.

[John Pleisse]

I was going to also suggest, conduct your test with the AP and not handflown.

[KSMooniac]

After reading the latest posts, I should have clarified in my 3-way method (that Jetdriven posted as well) that 3 TRACKS must be flown 120 degrees apart, not 3 HEADINGS.  To do this, I used OBS mode on my 530W and created waypoints in space and used the OBS knob to make a course of 0, 120, 240 as necessary and then had the A/P fly those tracks.

[jetdriven]

You can also watch your track on the GPS screen, on the aera its even displayes as a compass arc.  But that is ground track.

[Jeff_S]

Quote: Hank

As an engineer, that's neither "a lot of math" nor is it even difficult math.

[Hank]

Quote: Jeff_S

As a French major I can tell you "that's a lot of freakin' math."

Or, I could tell you "c'est con ces maths!"

[Parker_Woodruff]

Quote: 74657

[dsking001]

Again, thanks for all the helpful suggestions.  After examining my aircraft again, I noticed "engine droop" might be another causal factor for my decreased performance.  Looking at the top of the spinner and the upper engine cowl, there is about a 1/2" mismatch.  The spinner is slightly lower than the cowl.  From a profile view, the gap between the spinner and the cowling decrease from top to bottom, and the bottom of the spinner is lower than the adjacent radius of the lower cowling.  The lower engine mount bushings don't seem to be in as good of shape at the upper ones.  They just look a little aged.  This may not be the culprit for the speed loss, but I'm sure it does not help with engine droop and vibration.

I'll keep everyone posted.

Dan

[KSMooniac]

Dan, one thing to consider before you change engine mounts...the cowls will wear in the camloc holes, and this can cause the cowl to "ride up" after an air load is on it.  Examine the gap at the back of the cowl, and see if it is even or not after a flight.  My '77 likely has a larger gap than your '84 (I think tolerances and workmanship improved quite a bit as the line matured) so you might not have such a problem, but I know my cowl would lift and end up sitting proud behind the spinner because the holes got loose and the gap allowed the whole assembly to tilt/shift.

BTW, one of my classmates is in your Squadron... Maj Alcorn.  Small world!  I took him for a ride in my J a few years ago when I came down for a visit and he about cried after seeing what a WAAS GPS + A/P + GPSS could do compared to the B-1, not to mention in-cockpit weather.

[xftrplt]

Dan, as an AF pilot, have you considered simply getting a wingman with a TAS readout?  Forget the math and flying triangles/squares.

[dsking001]

I think a formation cross-country is in order soon.  My father's Comanche has an Aspen PFD with TAS indicator.  I just haven't decided where to fly to yet.

[M016576]

I know this sounds silly... but if you've got a dead cylinder, you'd probably only be making about 140 knots.  I would hope you'd feel it though....

 

Found that out the hard way this past weekend, when I lost a cylinder about 30 miles from the field (plugged injector, I think... being looked at right now).  As a data point... with all 4 I was making 156kts, with 3 I was making 138 kts in level flight at 6500'.

[Shadrach]

Quote: KSMooniac

After reading the latest posts, I should have clarified in my 3-way method (that Jetdriven posted as well) that 3 TRACKS must be flown 120 degrees apart, not 3 HEADINGS.  To do this, I used OBS mode on my 530W and created waypoints in space and used the OBS knob to make a course of 0, 120, 240 as necessary and then had the A/P fly those tracks.

[jetdriven]

Ross, I have been doing it all wrong. No wonder I get 155 TAS on calm days and 148 on windy days.   I just assumed the plane was faster on calm days.   Doesnt mix the MMO in the fuel up so much, and doesnt disturb the flame front in the combustion chamber.  :X

[Shadrach]

 

Byron - I get the sense that I'm being made fun of ...   The reason that you're faster when it's calm is that it's much harder, if not impossible to get on "the step" with almost any Xwind component. 

 

[jetdriven]

Yeah I forgot. I cant get on the step when its turbulent, too much swirly local flow interferes with the laminar flow, and plus the tail drops and hangs down too much. I should get VG's to solve that. Plus its safer it drops my stall speed one knot.   This causes drag too so I cant break through to the step.  Of course, I run the engine too lean, so it can't make enough power with the burned valves and the prop RPM is 2500 in cruise, which is too high to get a good "bite" on the air.  But hey, I also run rich of peak, book value plus 1.5 GPH on the 30 year old fuel flow meter, after all I want to be safe and make TBO.  EGT's too high burn cylinders.  Wait, its turning 12 years this month anyways, so I better pull it off and send it in to Lycoming.  Its "mandatory" I do so. Everyone knows factory overhauls are better anyways.  I want my insurance coverage not to cancel me. So I have to do it.

 

I might get myself an IO-390 STC.  Its only 70 grand and increases cruise speed 3 knots, while adding another GPH to the fuel flow.  Sweet deal, that 3 blade spinner is shiny.  And the IO-390 decal.  Of course I screwed up and got 54 gallon bladders, stupid me, so I only have 3 hours range now. But I better call it two, to be safe.  Dont want to run out of fuel. Only one stop between Houston and Kerrville for the homecoming.  Leave at 8, arrive at noon. My wife and I part ways that morning, she is waiting on me in Kerrville at noon. We save on a rental that way. 

 

I love Mooneys.

 

 

 

 

 

Flame suit on now.

[wolftimj]

Nothing that hasn't been said here already; just sold my 82 J. Always did 160 - 164 TAS at 6k to 11k (depending on local atmospherics). Something's not right, probably a few things for that big a miss. I'd start at a service center for a rigging adjustment. Don't assume things are as they appear. Just bought a 97 Bravo. The rig was off, as was the Aspen so the slip/skid was wrong. I was flying sideways. If you're anywhere near Texas give Don Maxwell a call, he'll straighten her out.

[M016576]

Quote: jetdriven

Yeah I forgot. I cant get on the step when its turbulent, too much swirly local flow interferes with the laminar flow, and plus the tail drops and hangs down too much. I should get VG's to solve that. Plus its safer it drops my stall speed one knot.   This causes drag too so I cant break through to the step.  Of course, I run the engine too lean, so it can't make enough power with the burned valves and the prop RPM is 2500 in cruise, which is too high to get a good "bite" on the air.  But hey, I also run rich of peak, book value plus 1.5 GPH on the 30 year old fuel flow meter, after all I want to be safe and make TBO.  EGT's too high burn cylinders.  Wait, its turning 12 years this month anyways, so I better pull it off and send it in to Lycoming.  Its "mandatory" I do so. Everyone knows factory overhauls are better anyways.  I want my insurance coverage not to cancel me. So I have to do it.

 

I might get myself an IO-390 STC.  Its only 70 grand and increases cruise speed 3 knots, while adding another GPH to the fuel flow.  Sweet deal, that 3 blade spinner is shiny.  And the IO-390 decal.  Of course I screwed up and got 54 gallon bladders, stupid me, so I only have 3 hours range now. But I better call it two, to be safe.  Dont want to run out of fuel. Only one stop between Houston and Kerrville for the homecoming.  Leave at 8, arrive at noon. My wife and I part ways that morning, she is waiting on me in Kerrville at noon. We save on a rental that way. 

 

Classic!  So true... LOL