Airspeed errors, and flying on AOA..

[FW Dave]

This has been touched on, but I saw this first hand today doing grass field approaches. It was calm, and about 5 knots from the east at Pattern altitude, right down the runway.

scratching my head as to why i really coudn't get it on the back side without getting really slow airspeed readings.. I had been flying with the static port open, and noticed that during short field pop offs, no airspeed was showing at times then it would jump over 40.. Figured it was AOA related, so I did a 30 flap fly off, and it did the same thing, at small AOA.. went up high, slowed down and tried to find the Stall and High AOA steep decent mode.. in order to find it, I had to have Zero airspeed showing.. LOL.. and the Garmin AOA was showing me on the backside slightly.. so.. I conclude the static alt source is screwing things up slow..

Close it: Wallah.. now its showing me 50mph, and the AOA seem to match.. on the donut... slow to 45, and in the beep beep, orange, slow to 42, and there it is.. the 500 fpm descent, the stable, behind the wing drag, and solid as a rock, I make turn after turn, to validate the airspeed.. I end up cracking the static open a tiny bit and calibrate it to the GPS minus density alt.. and then from 3500 AGL, I fly just above the donut, all the way around the pattern, and land over the trees with that nose high stable approach.. bump the power barely and roll it on in a 3 point, smooth as butter..

I conclude I was never getting it slow enough because having the static port open was screwing things up and making me fast.. Today, time after time, good tail wheel landings.. then added a few knots, and did wheel landings.. every landing was over my 50 ft trees and roll was under 500 ft. even with full fuel, it was just a little longer. I wasn't hitting the brakes hardly as well.. Now that I got it slow enough, when its done, it is done.. LOL.. close the static port!.. I forgot all about it.. until today..

But with it closed, it seems that at slow speed, it still seems off to me, .. but I can live with that, as long as pattern speeds are stable and my Garmin AOA system is giving me valid data . I found that at least.. now Im slowing it down more and more.. this thing is every bit as stable as a cub at slow speeds.. maybe more.. since the elevator is limited.. I never felt it begin to tickle or shudder. Granted, i didn't flirt with super slow speeds, just moderately slow speeds.. I am even more impressed with the stability. I did several aileron effectiveness tests, at various speeds up high, during HIGH AOA flying, as well as rudder effectiveness..

edit: I took the extra rudder spring off, and it feels more balanced too., and I did the 1.5 inch chain link mod.. I really like the way it handles now.. I can glue the tail down with a tiny burst o power. I flew today with 25 pounds of lead shot in the way back of the aft cargo, bungee'd down, and 18 gal fuel doing this today..fyi

 

[Snowbirdxx]

Dave,

Next time you fly please do the static check.
Go to a long flat runway.
Set your altimeter to an even number. Best the closest thousand to field elevation.
Takeoff with full power and stay low. 20 ft max.
Accelerate and retract flaps.
Near the end of the runway you should be doing 120 mph or so.
Now check your altitude. It should read the value set before.
Remember the difference. Pull up.
Do not fly into the ground while looking for the altimeter.

If your static pressure is screwed up you get incorrect youaltitude indications. You then need to adjust it with ap ring at the pitot tube.

 

[FW Dave]

thank you Thomas I was hoping you would offer some advice.. will do this today sometime.

 

[FW Dave]

Thomas, Ok, I did the test, the altimeter lost 80 ft during the acceleration.. I did some more race tracks trying to determine a true average TAS, and then come up with an error.. there is about 5-8 knots high with the valve slow, and 5=8 knots slow when above 70 or so..

if I open the side vent, with he alt static open, it changes the airspeed.. when I alternatively open and close the valve at 2000 ft and 100 kt, the speed and altitude vary by 100 ft, and 8 knots..

My IA said today to try the buffer ring, and see if I could trim it out.. he said that sounded like a good idea to him..

 

[MTV]

Nothing wrong with having an accurate airspeed indicator. That said, it wasn't the static port that was making you too fast on approach......

I can't remember the last time I actually looked at an airspeed indicator while landing, frankly. Too much of a distraction. And my current airplane has one of the current vogue "Angle of Attack" indicators. I couldn't land this thing to save my soul by reference to that POS.

Go out and do a LOT of slow flight, as you described in your first post. Then a lot of stalls in all sorts of configurations. Your landings will sort themselves out.

Almost everyone flies these things too fast initially. Part of that is referencing the airspeed indicator. But, again, it's not the gauge making you fast, you're not feeling what the airplane is telling you via your butt.....

MTV

 

[johnaz]

Nothing wrong with having an accurate airspeed indicator. That said, it wasn't the static port that was making you too fast on approach......

I can't remember the last time I actually looked at an airspeed indicator while landing, frankly. Too much of a distraction. And my current airplane has one of the current vogue "Angle of Attack" indicators. I couldn't land this thing to save my soul by reference to that POS.

Go out and do a LOT of slow flight, as you described in your first post. Then a lot of stalls in all sorts of configurations. Your landings will sort themselves out.

Almost everyone flies these things too fast initially. Part of that is referencing the airspeed indicator. But, again, it's not the gauge making you fast, you're not feeling what the airplane is telling you via your butt.....

MTV

I agree with Mike, never look at the airspeed when close to the ground. One can feel the airplane once you know it.
Try flying down a long runway, as slow as possible, maintain about 5' off the ground but do not let it touch or land. You will get the feel of what it takes to fly slow in landing configuration after getting comfortable in slow flight near the ground.
Most Husky pilots fly too fast on landing.
John

 

[FW Dave]

Mike, John, Of course!..Yes have been doing so, and will continue.. I fly slow alot, but did not do alot of it behind the wing until lately.. slipping it, maneuvering it, etc....

Mike, I was the guy on the other forum with the Sedan operating out of my 1400 ft strip, over 50-60 ft trees at both end.. had to really slow that thing down and slip it, low and slow, love it. This plane is far easier to handle.. This airspeed thing started bugging me when the airspeed would intermittently drop to zero.. So I was practicing behind the wing High AOA approaches when this really told me something was off.

I actually like the Garmin AOA.. but I have years and years of flying on AOA in my past, so it tells me alot.. it was conflicting with what the airspeed should be in my mind..

the cure to most diseases is flymor

 

[johnaz]

Mike, John, Of course!..Yes have been doing so, and will continue.. I fly slow alot, but did not do alot of it behind the wing until lately.. slipping it, maneuvering it, etc....

Mike, I was the guy on the other forum with the Sedan operating out of my 1400 ft strip, over 50-60 ft trees at both end.. had to really slow that thing down and slip it, low and slow, love it. This plane is far easier to handle.. This airspeed thing started bugging me when the airspeed would intermittently drop to zero.. So I was practicing behind the wing High AOA approaches when this really told me something was off.

I actually like the Garmin AOA.. but I have years and years of flying on AOA in my past, so it tells me alot.. it was conflicting with what the airspeed should be in my mind..

the cure to most diseases is flymor

Dave, Learn the feel by seat of the pants by what I had described doing. Do it up high first if any concern. Once you really have the feel of the Husky you will not need to look at airspeed when close to landing. Slight power on or off controls it all.
When flying 5' off runway, just do slight power reduction from holding position and it will land, slow as possible, three point, maybe tailwheel first.
John

 

[Snowbirdxx]

I doubt that Dave needs feeling the plane by his pants, I am pretty sure he can do that. But that said it bothers me to have inaccurate readings in the cockpit. Better none than wrong ones.
Dave
Measure the diameter of the parallel part of the tip of the pitot probe.
take a 1/2 inch wide roll of isolation tape and wrap it around the conical part of the pitot tube with a thread backwards towards the parallel part. Once there make the thread finer till you at the end of the parallel part and have a thickness there of 1.7 mm.

What you are doing is increasing the diameter just before the static pickup holes, by keeping the shape conical. This changes the pressure at the tube to Static

Do the runway race test again and look on the altimeter. It should stay now static. If there is still a drop add more tape at the parallel part.
When satisfied, cover the whole setup with a thin shrinktube. Try again and if satisfied measure thickness of the setup.
Now you can machine a ring made out of Delrin or Aluminum and install it permanently with super glue.

 

[FW Dave]

thank you guys..THomas, Im on it.. I found a pic of the mods, and of Bumpers ring.. I see how it works. thank you.

 

[jkalus]

Dave, you might want to have your plane checked for pitot or static leaks. It can happen, and it would cause you to chase your tail. A pinched line would also drive you crazy as in stable flight it will catch up and then get wild during transitions (alt or airspeed).

 

[Snowbirdxx]

Dave, like Joe says, that might be , but the most likely location would be in the wing root, which you will see after removing the Front wingroot panel inside the cabin. There you will find the plastic hose slid on the aluminum tube running down. And a safety wire wrapped around to secure it instead of a clamp. The wire is usually cutting through the plastic line creating a P tot or P stat leak.

Easy and cheap to fix.

 

[FW Dave]

will look at it.. I couldn't find any leaks thus far. The tape test took me in the right direction. I am 3D printing some rings for testing soon. various thicknesses from 1.7mm to 1/8th inch. will keep looking.

 

[newhuskyflyer]

will look at it.. I couldn't find any leaks thus far. The tape test took me in the right direction. I am 3D printing some rings for testing soon. various thicknesses from 1.7mm to 1/8th inch. will keep looking.

3D printing of these - great IDEA - keep me posted -

 

[tbienz]

Something to consider: if your ASI goes to zero during landing, it’s an abnormality that must be addressed, but if the ASI reads well off actual, that’s pretty normal and for most aircraft, the flight behavior will be consistent (stalling at a given indicated speed for a given weight in a specific plane). As long as you know the indicated airspeed at which YOUR plane behaves in a specific manner, you’re good. Even with a custom fitted/tested 3-D printed pinky ring equivalent, as soon as you fly to a different altitude, it will be “wrong” again. The ASI is almost always “wrong” but it still gives you what you need to know.

 

[FW Dave]

Something to consider: if your ASI goes to zero during landing, it’s an abnormality that must be addressed, but if the ASI reads well off actual, that’s pretty normal and for most aircraft, the flight behavior will be consistent (stalling at a given indicated speed for a given weight in a specific plane). As long as you know the indicated airspeed at which YOUR plane behaves in a specific manner, you’re good. Even with a custom fitted/tested 3-D printed pinky ring equivalent, as soon as you fly to a different altitude, it will be “wrong” again. The ASI is almost always “wrong” but it still gives you what you need to know.

Tom, Yup, that sums it up.. because we dont have Calibrated A/S system..

Im not having any issues flying/compensating for it, don't really need airspeed or AOA, just wanted it to be accurate as I can make it But the AOA doesn't lie.. it is spot on.. My background is flight test, so Im being maybe a little anal about it.. Landings are fine. Can I do better, sure.. but that is good enough for around here.. I have also done a myriad of power off landings on the short strip, both with the prop flat and with it pitched, slips, no slips, wheel, and 3pt.., basically just trying to get everything dialed in properly, so it does't give me BAD information.. No information is better than Bad.. I operate daily out of a short stip, so we always focus on spot landings, stable, on the wing, feeling the plane, and short, less than half the strip, so 700 ft. Keeps you sharp.

Consequently I have it moving the right direction using tape, tested it today.. very little difference from Alt source to Normal at the low end, and the speeds were not that far off maybe 12mph at the big end.. and the airspeed does't go to zero anymore.. I chased down all the tubing, and everything is ok. Making progress..

Flew today behind the wing at High Alpha, on the beeper, stable, depending around 3-500 fpm, slow flight, and patterns, and its was indicating around 40mph.. That is progress, and that is about what it should be 40-45 mph weight depending.. My on speed /30 flap was around 52.. thats about good too. I get the rings printed next week and will pull the tape off and try them out..

Thomas D.. I love the chain link mod.. I did the small 1.5 inch stainless ring. what a difference in spring tension in the flare.

 

[johnaz]

Tom, Yup, that sums it up.. because we dont have Calibrated A/S system..

Im not having any issues flying/compensating for it, don't really need airspeed or AOA, just wanted it to be accurate as I can make it But the AOA doesn't lie.. it is spot on.. My background is flight test, so Im being maybe a little anal about it.. Landings are fine. Can I do better, sure.. but that is good enough for around here.. I have also done a myriad of power off landings on the short strip, both with the prop flat and with it pitched, slips, no slips, wheel, and 3pt.., basically just trying to get everything dialed in properly, so it does't give me BAD information.. No information is better than Bad.. I operate daily out of a short stip, so we always focus on spot landings, stable, on the wing, feeling the plane, and short, less than half the strip, so 700 ft. Keeps you sharp.

Consequently I have it moving the right direction using tape, tested it today.. very little difference from Alt source to Normal at the low end, and the speeds were not that far off maybe 12mph at the big end.. and the airspeed does't go to zero anymore.. I chased down all the tubing, and everything is ok. Making progress..

Flew today behind the wing at High Alpha, on the beeper, stable, depending around 3-500 fpm, slow flight, and patterns, and its was indicating around 40mph.. That is progress, and that is about what it should be 40-45 mph weight depending.. My on speed /30 flap was around 52.. thats about good too. I get the rings printed next week and will pull the tape off and try them out..

Dave,
Will you have extra rings for us if we need them?
Thanks,
John

 

[FW Dave]

Dave,
Will you have extra rings for us if we need them?
Thanks,
John

These rings are printed with plastic and only intended to be test units.. I have to further investigate how to get them printed with a durable material that will stand up to UV, and elements.. so not yet..but if we solve the details, it will be repeatable.. I will probably find that they are a little rough overall. and that machining or ABS press will be better.. too early to tell.

I shot Bumper a message to see if he still was making them too.. waiting to hear. His design looked pretty perfect to me.

 

[FW Dave]

did some more flying with the rings.. 40 gal gas, solo.. with 30 pounds in the back cargo.
I had 1.7mm through 1/8 inch made up, I started with the big one, nope, lots of variation, went to the 1.9, better, went to the 1.7 better.. the altimeter test was successful at 1.7mm. The airspeed indicator overall, with the alt source open or closed is dead on at 80mph.. at 70, its about 5 mph faster than the alt source, and at 60mph, full flap, its feeling slower, probably around 55, because the wing is feeling tired, nearing the stall, I went up higher, did the same, and although it never stalls, it still seems a little fast indicator wise, but.. thats ok, I can live with it, I found the sweet spots.. Flew a 30 flap approach in nice conditions, light winds, at 60mph indicated, and it felt slower but the sink rate was good, and the AOA was showing donut.. that approach, the wing was level with the horizon, and 3 point no problem less than 100 ft down the runway, stopped around 400-450 in a three point, didn't touch the flaps, very light braking.. so its about 5-7mph off..

So it seems to jive with what Im feeling, but its a little off, but consistent enough.. so now Im going to just fly the crap out of it and see how it goes.. Im having no problems stopping in under 500 ft consistently, without getting behind the wing, that was my goal, and that all the indications jive..

This was over high trees and spot land, and am hitting my target within 100 ft, over trees.. Im very happy with this airplane and my progress.. keep flying!