Avid Flyer is flying (videos to prove it) :-)

[1avidflyer 1983]

Hi guys,  finally  got a couple of videos up on youtube of the Avid test flights last evening.  ASI reads a good bit high, alarm flashing on the engine monitor is a false alarm from the tach.  Got that fixed today.  Got a few more things I want to tweak before the next flights, maybe more flying tomorrow evening.  Anyway, videos aren't great, mostly shows the panel, not much of a view out side.  But it flys!!!  JImChuk

[BryceKat 125]

Jim,

Congrats! I like your Tinytach mount, how'd you do it? What engine monitoring system is that? I've been thinking I might replace my Westach egt as I question its accuracy because of the inaccuracy of their tachometer. Thanks, Bryce

[1avidflyer 1983]

The instrument panel is a flat piece of  aluminum.  It is screwed to the glare shield with 5 or 6 screws.  ( I epoxied in some backer aluminum in the glare shield where the screws are)  For  the tiny  tach mount, I just cut out a piece of 29  ga. steel I had handy with the bottom corner going in between the instrument panel and the glare shield where a screw was.  Holds nice.  It's just temporary, once I'm  sure the other tach is right the tiny tach will go away.  The engine monitor is an MGL E1.  I bought it from an outfit in England.  Here is a link to their site.  http://www.parts4aircraft.com/  Very good to work with, and I saved about $150 buying it from there verses a US distributor.  I think they have raised their prices a bit, when I bought mine last year, it cost me $237 shipped to my door.  All the US  sellers price was $345 before shipping.  The MGL can do 2 egts, 2 chts, oil temp oil pressure, volts, tach, hobbs meter, flight log, and maybe other things as well.  I like it for clearing up the panel with one gauge rather than a bunch of them.  They also make it in a 2 1/4" version, but I like the larger display.   You can send your Westach gauges in to the company and they will recalibrate them. When I did it, it cost $25 for a dual EGT.  JImChuk

[BryceKat 125]

Cool, thanks Jim!  Do you remember if your egt was very far out of whack?

[lv2plyguitar 172]

What engine you flying behind?  Sounds good.

[wypaul 448]

I have the 2.25 version and would recommend the larger one as well,  the small one is very hard to read the oil pressure due to the display setup.

[1avidflyer 1983]

Cool, thanks Jim!  Do you remember if your egt was very far out of whack?

Don't remember for sure, but it seems like my readings are lower now then they  used to be.  Didn't really study them much though.  Busy with other things you know. :-)   JImChuk

[1avidflyer 1983]

What engine you flying behind?  Sounds good.

Jabiru 80 HP engine.  JImChuk

[marksires 484]

Congrats Jim!

[1avidflyer 1983]

Did a little more flying this evening.  Thought I was running my go pro, but  I guess not.  Addressed some of the glitches I've come across.   Adjusted the rigging on the left wind one turn.  Now I don't have a slightly heavy left wing.  Have to repitch the prop.  Great cruise speeds, but not so great climb out.  I'll take out some pitch.  Running a 66" taper tip warp drive prop.  At about 2800 rpm, I'm showing about  95  MPH airspeed.  Didn't try any full throttle runs to see what I would run up to for rpm, but red line is supposed to be 3300 and I doubt I would get anywhere near that.  Climb out at 60 I'm showing only 2830 or so, used to be up around 3150 on climb out.  Oh well it's just a matter of sorting it out.  I used a digital manometer to calibrate the ASI today as well.  I have 4 or 5 ASIs and all of them read way high.  Used my label maker to put numbers on the face of the ASI that should be fairly close.  They ended up agreeing  with the GPS  Here is a shot of the panel tonight.  JImChuk

PS, the white and green lines on the ASI were just guesses with a different ASI before I flew the plane..  I will have to do some stalls and such to see where I'm really at. 

Edited 15 Aug 2017 by 1avidflyer

[flywise 169]

Hey Jim, could your static port location give you the false indicated airspeed?? Is your static port in the cabin?

I had the same high airspeed reading and found the cause to be my static port...

My 1 cent, cheers, Laurent

[1avidflyer 1983]

I did the manometer test on the ground, and calibrated the ASI with the labels then.  They seem to agree with the GPS when I compared them.  There was virtually no wind to effect the GPS readings.  I do know what you're saying though.  My static port locations have always been just behind the instrumental panel.  When you open a door in flight, you will see the ASI change.  JImChuk

[flywise 169]

Ideally your static port has to be in a "zero" pressure area, no negative/positive air during flight (the two static port interconnected is to prevent asi change when you're crabbing or flying out of yaw) . If your static port is in a "low" pressure air your airspeed will read high, "high" press air will read too low...

If your static port is inside the cockpit the airspeed will read high as the cockpit is a low press area compared to the outside. The difficult trick is to find the right position on the fuselage....

Laurent

[1avidflyer 1983]

Where should the static port be if I'm testing the ASI with the manometer on the work bench?  :-)  Actually I  would bet that most of our Kitfoxes and Avids have the static port  behind the instrument  panel.  All 4 of my Avids and my Kitfox 1 were that way when I got them.  JImChuk

[EDMO 1078]

I can live with a plane that flies (ASI) 5 mph faster with the windows down.  My Ercoupe and Kitfox were both that way.  EDMO

[1avidflyer 1983]

I snapped a few pics of my  ASI manometer test outfit.   Very high teck!!  (not)  line comes from pitot port on back of ASI to a T.  One line of the T connects to the manometer, other line off the T goes to a coil of 1/4" ID tubing.   Hook it all up, pinch off the end of the coil of 1/4" tubing so it holds air.  If you start folding up that tubing in your hand, you will see the pressure (water column) rise in the manometer, and the ASI will go up.  There are known figures for the water column figures to correspond with a certain MPH shown on the ASI.  For instance, 1.70" on the manometer = 60 mph,  2.32" = 70 ect.  The manometer cost about $35 on ebay, and I bought it when I changed the gas valve on my furnace, so I had it already.  Here is a link to an article on that showing other # for other MPH readings.   Not sure if anyone is interested, but it's pretty quiet here lately so here goes.  The ASI that I relabeled this way on the ground was very accurate according to my GPS in the air.  JImChuk

http://www.jackbhart.com/firefly/firefly144.html

[Extrados 1]

I don't have a pressure gauge. Thank you very much, the video seems interesting. I'll try the GPS without wind.

[1avidflyer 1983]

If you use the GPS, maybe fly along a straight road, and record the ground speed and ASI reading.  Then right away, turn around and fly along that same road in the opposite direction, record the speeds and average  both readings for a more accurate idea of ASI error.  JImChuk

[109jb 181]

Your airspeed indicator looks like it is exactly right and the calibration was for knots and not for mph.  The formula for calculating this is:

V=a₀ * (5*((q_c/p₀ + 1)^2/7 - 1))^1/2  

where a₀ is the speed of sound (661.48 kts) or (761.22 mph)

q_c is the pitot pressure in inHg

p₀ is the sea level static pressure (29.92)

 

Taking your one picture showing an airspeed reading of 85 mph at 0.266 inHg, plugging the 0.266 into the equation using mph for speed of sound you get 85.6 mph or using knots you get 74.4 knots

[109jb 181]

0.166 inHg calculates out to 58.8 knots or 67.7 mph.

[1avidflyer 1983]

John,  did you look at the article I linked to?  I don't know if you are right or the guy writing the article is, but if you are, I have a very fast Avid.  Using the manometer, I remarked the ASI in my Avid, and here is a picture of me flying it showing the ASI.  Notice I'm climbing just a bit, and 2800 is a good cruise rpm for the Jabiru.  JImChuk

[Allen Sutphin 705]

The factory static port on my model 2 is pretty much under the lift handle on the left side of the fuselage.

[109jb 181]

Jim, I did see your link. His equation has been reduced down to simply a constant x v2 = water column height, which makes it hard to work back the units. That's why I posted that one with a little better dimensional verification. I'll have to first off my college aero books from 25 years ago to do a better dimensional analysis if I can find them.

Remember though that the indicator check is one part but the in-flight reading can still be of quite a bit depending on static and pitot locations. The pitot ideally should be way out in front of the wing, and choosing a static location is either hit or miss, or you have to do something like a trailing cone to get it really good.

[1avidflyer 1983]

I'm sure your right John about the many things that can affect the accuracy of the airspeed indicator.  I do know that in my case, my airspeed is very accurate according to the numbers I have added to my ASI.  Verified with a GPS.  JImChuk