Van's Air Force
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Blade Pitot Input
- Thread starter ww2planes
- Start date
Works Great!
I am using a Piper blade-style pitot on my RV-8, and love it! It's been knocking about in my box-o-airplane-parts for years, ever since I rented my first hangar, and found that the last guy had left a bunch of stuf in the shelves. When I started the RV-8, I priced heated pitots and nearly fainted! For what I was going to have to pay for a new one, I figured I'd risk the pitot ice! Then I remembered that blade...I dug it out, connected it to 12 volts, and sure enough, it got hot! OK...first piece of extra equipment checked off the list!
Based on what I heard from numerous folks, you don't want to use the static ports on the blade - they lead to significant errors. Use the pitot only, and the standard van's static locations on the fuselage. I have excellent airspeed calibration, and in my opinion, it does look cool...
One caveat - I think I have read that there are several different Piper blade pitots, but I think one type is the most common, and that is what I appear to have. Not sure if they all work as well.
Paul
I am using a Piper blade-style pitot on my RV-8, and love it! It's been knocking about in my box-o-airplane-parts for years, ever since I rented my first hangar, and found that the last guy had left a bunch of stuf in the shelves. When I started the RV-8, I priced heated pitots and nearly fainted! For what I was going to have to pay for a new one, I figured I'd risk the pitot ice! Then I remembered that blade...I dug it out, connected it to 12 volts, and sure enough, it got hot! OK...first piece of extra equipment checked off the list!
Based on what I heard from numerous folks, you don't want to use the static ports on the blade - they lead to significant errors. Use the pitot only, and the standard van's static locations on the fuselage. I have excellent airspeed calibration, and in my opinion, it does look cool...
One caveat - I think I have read that there are several different Piper blade pitots, but I think one type is the most common, and that is what I appear to have. Not sure if they all work as well.
Paul
vlittle
Well Known Member
ww2planes said:
I have a Dynon Pitot/AOA mounted on my -9A. I'm having some airspeed calibration errors.
Today, I calibrated my static system/altimeter, and my airspeed (through the static system with the pitot at ambient pressure). On the ground, everything is within 1% or so after fixing a math error (blush).
In the air, however, I'm getting an indicated stall speed about 5 knots high, and an indicated cruise speed 5 knots low. I suspect a pitot system leak (not likely) or a pitot position error (may be too close to the wing pressure wave?). I don't think it's a static position error because I'm using the Van's stock locations.
Anyone else with a Dynon in a -9A that has calibrated their system on the ground and in the air, please let me know your experiences.
Vern
gmcjetpilot
Well Known Member
Why?
I don't begrudge people building what they want, but I wounder sometimes why so many want a heated pitot. I really don't get a VFR pilot needing a heated pitot on their plane. Even IFR, ice should be a rare event, at least if you plan your flights right, i.e. safe and legal.
They are expensive, draw copious current add weight and the amount of time you might use it, is......well questionable. I relize many are drawn to them because they like the looks, since the standard "TUBE" is plan, although arguable very functional, light and inexpensive. Make a fake one out of fiberglass or metal of any cool shape you want for a few bucks.
Lets go out on a limb (and you would be). You find yourself in icing conditions. Some how it gets so bad your pitot is blocked and thus your airspeed indicator is dead. You still have approximate speed from GPS ground speed. Of course you're solid IMC now, on instruments. You need to get out of it NOW, both from a common sense and legal stand point, right. In my opinion (and the FAA's) if you're getting airframe ice you are not only illegal you are in a dangerous condition, even with pitot heat. Once you see ice it is "KNOWN ICE", at least now.
How do you get ICE? Any takers?
Ans: Visible moisture and temp below 0 C. Period end of story. Stay out of clouds or temps below 0 C (and above -40 C) no ice. If there is no clouds, mist, fog (defined as visibility of say less than 1 miles) no ice. If temp is above 0C no ice. It is that simple. NO ICE. You can't form ice unless you are in a cloud below 0C. (Below -40C there's not enough moisture to cause icing.)
Someone might say "freezing rain" (I coverd it with visible mosture). If you are in freezing rain, you're in trouble. Don't worry about the pitot. You'll have no lift or thrust when the wings and prop ice over. In this case heated pitot will only help you to see indicated airspeed on the way to the scene of your crash.
If you plan on flying IFR routinly than the value of a heated pitot is better justified, but its not required IFR equip! I am surprised how much effort and expense builders put into a heated pitot for VFR RV. If you are a VFR pilot and wondering into clouds in freezing conditions, you have more troubles than pitot ice.
Suggest builders evaluate if they really (really) NEED a heated pitot. If not sure, run some wires out the wing and put in one of those fake heated pitot ( http://www.gretzaero.com/ga500.html ). You can replace it later with a hot one, if you so decide. Just a suggestion but if you have to have a heated pitot you have to have it. However weight on RV's is important and the lighter the better. Its just a thought.
George
I hate asking the obvious (may be not so obvious), but I can't stand it, why do you want a heated pitot tube at all? I know it sounds stupid, especially from a CFI-I-ME, ATP with a few type ratings, but why do you want a heated pitot on a single engine sport plane that is prohibited from being in icing conditions. Do you plan on flying in icing?ww2planes said:
I don't begrudge people building what they want, but I wounder sometimes why so many want a heated pitot. I really don't get a VFR pilot needing a heated pitot on their plane. Even IFR, ice should be a rare event, at least if you plan your flights right, i.e. safe and legal.
They are expensive, draw copious current add weight and the amount of time you might use it, is......well questionable. I relize many are drawn to them because they like the looks, since the standard "TUBE" is plan, although arguable very functional, light and inexpensive. Make a fake one out of fiberglass or metal of any cool shape you want for a few bucks.
Lets go out on a limb (and you would be). You find yourself in icing conditions.
Some how it gets so bad your pitot is blocked and thus your airspeed indicator is dead. You still have approximate speed from GPS ground speed. Of course you're solid IMC now, on instruments. You need to get out of it NOW, both from a common sense and legal stand point, right. In my opinion (and the FAA's) if you're getting airframe ice you are not only illegal you are in a dangerous condition, even with pitot heat. Once you see ice it is "KNOWN ICE", at least now. How do you get ICE? Any takers?
Ans: Visible moisture and temp below 0 C. Period end of story. Stay out of clouds or temps below 0 C (and above -40 C) no ice. If there is no clouds, mist, fog (defined as visibility of say less than 1 miles) no ice. If temp is above 0C no ice. It is that simple. NO ICE. You can't form ice unless you are in a cloud below 0C. (Below -40C there's not enough moisture to cause icing.)
Someone might say "freezing rain" (I coverd it with visible mosture). If you are in freezing rain, you're in trouble. Don't worry about the pitot. You'll have no lift or thrust when the wings and prop ice over. In this case heated pitot will only help you to see indicated airspeed on the way to the scene of your crash.
If you plan on flying IFR routinly than the value of a heated pitot is better justified, but its not required IFR equip! I am surprised how much effort and expense builders put into a heated pitot for VFR RV. If you are a VFR pilot and wondering into clouds in freezing conditions, you have more troubles than pitot ice.
Suggest builders evaluate if they really (really) NEED a heated pitot. If not sure, run some wires out the wing and put in one of those fake heated pitot ( http://www.gretzaero.com/ga500.html ). You can replace it later with a hot one, if you so decide. Just a suggestion but if you have to have a heated pitot you have to have it. However weight on RV's is important and the lighter the better. Its just a thought.
George
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n468ac
Well Known Member
1. Dynon issue ... we had your Dynon off 10 to 15 kts off with full flaps down ... found a pintched pitot tube going to the unit ... after replacing the tube everything worked on the mark.
2. Heated pitot ... We currently don't have a heated pitot, but are now going to install one. After flying in very light rain, we put her away. During the next week it got below frezzing ... the next time, i started my take off roll the air speed was dead! After taxing back to the hanger and three days of heating different parts of the plane ... i heated the pitot over night and it drained. If i had been off my home field this could have really put a damper on getting home. If we had a heated pitot this may not have happened.
2. Heated pitot ... We currently don't have a heated pitot, but are now going to install one. After flying in very light rain, we put her away. During the next week it got below frezzing ... the next time, i started my take off roll the air speed was dead! After taxing back to the hanger and three days of heating different parts of the plane ... i heated the pitot over night and it drained. If i had been off my home field this could have really put a damper on getting home. If we had a heated pitot this may not have happened.
gmcjetpilot said:I hate asking the obvious (may be not so obvious), but I can't stand it, why do you want a heated pitot tube at all? I know it sounds stupid, especially from a CFI-I-ME, ATP with a few type ratings, but why do you want a heated pitot on a single engine sport plane that is prohibited from being in icing conditions. Do you plan on flying in icing?
I don't begrudge people building what they want, but I wounder sometimes why so many want a heated pitot. I really don't get a VFR pilot needing a heated pitot on their plane. Even IFR, ice should be a rare event, at least if you plan your flights right, i.e. safe and legal.
They are expensive, draw copious current add weight and the amount of time you might use it, is......well questionable. I relize many are drawn to them because they like the looks, since the standard "TUBE" is plan, although arguable very functional, light and inexpensive. Make a fake one out of fiberglass or metal of any cool shape you want for a few bucks.
Lets go out on a limb (and you would be). You find yourself in icing conditions.
How do you get ICE? Any takers?
Ans: Visible moisture and temp below 0 C. Period end of story. Stay out of clouds or temps below 0 C (and above -40 C) no ice. If there is no clouds, mist, fog (defined as visibility of say less than 1 miles) no ice. If temp is above 0C no ice. It is that simple. NO ICE. You can't form ice unless you are in a cloud below 0C. (Below -40C there's not enough moisture to cause icing.)
Someone might say "freezing rain" (I coverd it with visible mosture). If you are in freezing rain, you're in trouble. Don't worry about the pitot. You'll have no lift or thrust when the wings and prop ice over. In this case heated pitot will only help you to see indicated airspeed on the way to the scene of your crash.
If you plan on flying IFR routinly than the value of a heated pitot is better justified, but its not required IFR equip! I am surprised how much effort and expense builders put into a heated pitot for VFR RV. If you are a VFR pilot and wondering into clouds in freezing conditions, you have more troubles than pitot ice.
Suggest builders evaluate if they really (really) NEED a heated pitot. If not sure, run some wires out the wing and put in one of those fake heated pitot ( http://www.gretzaero.com/ga500.html ). You can replace it later with a hot one, if you so decide. Just a suggestion but if you have to have a heated pitot you have to have it. However weight on RV's is important and the lighter the better. Its just a thought.
George
Wow George - your next post is 1K....
I haven't read nearly all of them but those I have are always welcome. Thank you and all the other experienced posters here that make learning a joy.
John
Heated pitot
I do not want to get into a tit for tat here with George, but I would encourage the installation of heated pitot tubes for anyone who is going to fly IFR. Yes, it's nice to say we'll just avoid icing. The distances which we can cover at RV speeds will almost always allow for changing weather conditions along the route, especially unforecast ones in the middle of winter in the Great Lakes. A number of the glass cockpits we are installing require Pitot and static to the AHRS. Why risk everything going South when it is probably needed the most? I'd rather be on the ground in one piece explaining why I was in "known" icing (unforecast known icing to be exact) than have my heirs explaining it. Accidents are usually the result of a number of things piling up on the pilot.
For the record, I've used my pitot heat 3 times in 230 hours in the RV-10. Once at 16K' over the Sierras because a thin scattered unforecast layer had formed and I was picking up light rime and needed to climb out of it, once for a thin fog layer that moved onto the runway at Vail as I was taxiing out, and once because I was climbing through a layer at 40 degrees F. I probably didn't need it, but was glad it was there.
Yes, the prices of these things make a blind man want to see, but when it's needed, it's needed.
I hate ice more than thunderstorms, and I do my best to avoid it. As a matter of fact, we fly very little IFR in the RV-10 because we like to enjoy the trip and see the scenery. But the times the pitot heat has been needed, it was there, and instead of being a crisis, it was just another operational item, and another weather lesson, which we always seem to get.
The neat thing about these airplanes is that we all get to build them to best suit the way we as individuals will utilize them.
Vic
I do not want to get into a tit for tat here with George, but I would encourage the installation of heated pitot tubes for anyone who is going to fly IFR. Yes, it's nice to say we'll just avoid icing. The distances which we can cover at RV speeds will almost always allow for changing weather conditions along the route, especially unforecast ones in the middle of winter in the Great Lakes. A number of the glass cockpits we are installing require Pitot and static to the AHRS. Why risk everything going South when it is probably needed the most? I'd rather be on the ground in one piece explaining why I was in "known" icing (unforecast known icing to be exact) than have my heirs explaining it. Accidents are usually the result of a number of things piling up on the pilot.
For the record, I've used my pitot heat 3 times in 230 hours in the RV-10. Once at 16K' over the Sierras because a thin scattered unforecast layer had formed and I was picking up light rime and needed to climb out of it, once for a thin fog layer that moved onto the runway at Vail as I was taxiing out, and once because I was climbing through a layer at 40 degrees F. I probably didn't need it, but was glad it was there.
Yes, the prices of these things make a blind man want to see, but when it's needed, it's needed.
I hate ice more than thunderstorms, and I do my best to avoid it. As a matter of fact, we fly very little IFR in the RV-10 because we like to enjoy the trip and see the scenery. But the times the pitot heat has been needed, it was there, and instead of being a crisis, it was just another operational item, and another weather lesson, which we always seem to get.
The neat thing about these airplanes is that we all get to build them to best suit the way we as individuals will utilize them.
Vic
Why?
Very good question George, and the answer for me is simple....
Becasue I had one, it worked, it was free, and so...why not?
I seriously doubt that anyone is going to go buy a new one from a Piper dealer (once they find out the price) just to make their RV's pitot look cool...my guess is that the questioner had found one like I did, and just wanted to know if it would work.
I am not advocating that they are required or necessary for our airplanes, but under my situation, it was simple. Same logic as the Wig-Wag flap...it cost next to nothing, it MIGHT save you're life (if you were being inatentive in the first place), so how could you possibly argue against it?
But if I had to go spend $1000 for a new one? Well, I think it would be a lot lower on my list.... So in the logic of "necessity", we essentially agree.
Paul
Very good question George, and the answer for me is simple....
Becasue I had one, it worked, it was free, and so...why not?
I seriously doubt that anyone is going to go buy a new one from a Piper dealer (once they find out the price) just to make their RV's pitot look cool...my guess is that the questioner had found one like I did, and just wanted to know if it would work.
I am not advocating that they are required or necessary for our airplanes, but under my situation, it was simple. Same logic as the Wig-Wag flap...it cost next to nothing, it MIGHT save you're life (if you were being inatentive in the first place), so how could you possibly argue against it?
But if I had to go spend $1000 for a new one? Well, I think it would be a lot lower on my list.... So in the logic of "necessity", we essentially agree.
Paul
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Clarification
Thanks everyone for the input. Most of it is not applicable as I never mentioned anything about a heated tube. I just want to know if anyone has any experience with the Piper Blade Style Pitot. Non-heated, non-dynon, just plain blade style pitot. If anyone has any input on this specific question I would love to hear it. Thanks everyone.
Thanks everyone for the input. Most of it is not applicable as I never mentioned anything about a heated tube. I just want to know if anyone has any experience with the Piper Blade Style Pitot. Non-heated, non-dynon, just plain blade style pitot. If anyone has any input on this specific question I would love to hear it. Thanks everyone.
f1rocket
Well Known Member
The guy who bought my RV-6 (non-heated pitot) used it as an IFR platform. He told me that occasionally, he used to get moisture in the tube and it would freeze.
I put a heated tube in the Rocket because I plan to get my IFR ticket, and I'd rather have it installed and not use it, rather than need it and can't install it.
I can't argue with George's arguments. He has far more experience flying than I ever will have. I usually side with the KISS principle. In this case, I didn't see it as much added complexity. Just another switch, which I had room for, and since I have adequate alternator capacity, that wasn't a concern either.
I put a heated tube in the Rocket because I plan to get my IFR ticket, and I'd rather have it installed and not use it, rather than need it and can't install it.
I can't argue with George's arguments. He has far more experience flying than I ever will have. I usually side with the KISS principle. In this case, I didn't see it as much added complexity. Just another switch, which I had room for, and since I have adequate alternator capacity, that wasn't a concern either.
Kevin Horton
Well Known Member
There are a lot of RVs flying with one of the various Piper blade pitots. The pitot part works just fine. The static source will probably give errors, so don't bother using it.ww2planes said:
Note: I have seen reports from one or two guys who did use the static source and were happy with it, but many more reports from guys who found significant errors. The difference in results probably has to do with the fact that there are several different Piper pitot blade part numbers, with different angles on the bottom. Each different angle gives a slightly different static source error - I think Piper used that fact to tune the static source accuracy to the various aircraft models.
Piper Blade input
I have a heated Piper blade on my RV-6. I have no issues with either the pitot or static function. Every 2 years it gets a IFR Pitot/Static check. Maybe I'm a lucky one. For my -8A I bought a Gretz Aero Heated Pitot. Would have liked another blade but couldn't find one at a decent price.
I have a heated Piper blade on my RV-6. I have no issues with either the pitot or static function. Every 2 years it gets a IFR Pitot/Static check. Maybe I'm a lucky one. For my -8A I bought a Gretz Aero Heated Pitot. Would have liked another blade but couldn't find one at a decent price.
gmcjetpilot
Well Known Member
You said that so well
That was the most Bombastic POST i could possibly make and that is all I got. You guys are going easy on me. I am so LOL. I thought I was going to get flamed. I had the my Nomex asbestos underwear on and every thing.
Hey it was just an opinion (very opinionated opinion). Good replies. When I was building my first RV, a RV-6 in the late 80's, I was killing myself trying to put a heated pitot on. I HAD TO HAVE ONE. Than years later I realized that I did not needed it. I was IFR rated but the plane never was. Hell some C-152's have heated pitots.
I am just trying to help, and the compliment was very nice. I thank you. I totally get it for some, and I guess you can find that day some rain might freeze and blaaaa blaaa blaaaa It's all good.
George
That was the most Bombastic POST i could possibly make and that is all I got.
You guys are going easy on me. I am so LOL. I thought I was going to get flamed. I had the my Nomex asbestos underwear on and every thing.Hey it was just an opinion (very opinionated opinion). Good replies. When I was building my first RV, a RV-6 in the late 80's, I was killing myself trying to put a heated pitot on. I HAD TO HAVE ONE. Than years later I realized that I did not needed it. I was IFR rated but the plane never was. Hell some C-152's have heated pitots.
I am just trying to help, and the compliment was very nice. I thank you. I totally get it for some, and I guess you can find that day some rain might freeze and blaaaa blaaa blaaaa
It's all good. George
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jonbakerok
Well Known Member
My Piper pitot works pretty good
Like others have said, it's a matter of luck with which model you get. One of these days, I'll remember to trace the angle on mine and post it.
However, even if you get lucky with the static port, it's still not all that accurate at the extremes. Mine reads 5 MPH low at stall and 5 MPH high at the top end. No big deal -- its not enough to change the way you fly it, and it's spot on even down to 60 MPH and up to 190 MPH. To me it was worth it for the simpler plumbing and the cheap pitot heat (I only paid $100 for it, rebuilt).
Like others have said, it's a matter of luck with which model you get. One of these days, I'll remember to trace the angle on mine and post it.
However, even if you get lucky with the static port, it's still not all that accurate at the extremes. Mine reads 5 MPH low at stall and 5 MPH high at the top end. No big deal -- its not enough to change the way you fly it, and it's spot on even down to 60 MPH and up to 190 MPH. To me it was worth it for the simpler plumbing and the cheap pitot heat (I only paid $100 for it, rebuilt).
Kevin Horton
Well Known Member
The type of error that static source position error gives is not detectable by a static check on the ground. The check on the ground checks the accuracy of the altimeter and altitude encoder. Static source position error is caused by the air pressure at the static source differing from the free stream air pressure. This happens because the air accelerates and decelerates as it wends its way over the curves of the airframe, and Bernoulli tells us that the air pressure changes as the air's velocity changes. But this error is not present if the airspeed is zero.Chino Tom said:
A static source needs to sense the free stream static pressure. The air pressure below the wing is higher than the free stream pressure, and the air pressure above the wing is lower than the free stream pressure. No pressure change from free stream = no lift.
It is a real trick to put a static source near a wing and find a place where you can measure the free stream pressure. Piper does it by putting an angle ahead of the static port. That angle causes the air to accelerate a bit, lowering its pressure, which cancels out the pressure increase caused by the wing. But that will work over a certain range of conditions.
I suspect many people flying amateur-built aircraft have not gone to the trouble to determine how much static source position error they have. It is a fair bit of work. It really isn't important if you fly VFR without an altitude encoder. But it can be important if you have an altitude encoder, as a static source position error affects the accuracy of the altitudes that your transponder reports. Big aircraft have Traffic Alert/Collision Avoidance System (TCAS), and TCAS uses the altitude it thinks you are at to provide commands for the big guys to avoid you. It works great, as long as your transponder is putting out accurate altitude data. And obviously if you fly IFR you would want to be sure your altitude indications were not in error due to static source position error.
Kevin Horton
Well Known Member
Tom,tin man said:
Are you using the static source on the blade? If so, it would be interesting to get the part number of your blade pitot, and the exact location you have it mounted. Is it mounted sitting flat on the wing skin, or is it angled forward or aft at all? All those details are important if someone wanted to try to replicate your installation. Small differences in location or angle will affect the pressure sensed by the static port.
The pitot pressure is not sensitive to location or mounting angle, or probe part number. It just has to be mounted so it is clear of the prop wash, not in the wake of anything else, and so the pitot port is out of the boundary layer (you would have to recess the base of the probe into the wing to cause problems with the boundary layer).
heated pitot
i'm also going to disagree with george on this issue. i have experienced pitot ice in imc on three occassions (that i can distinctly recall) in the last 20 or so years -- only one of which was accompanied by any sign of airframe icing. it wasn't fatal in any of them (i think.)
but it is not inconceivable to me that one get a vacuum failure (or the modern day equivalent -- an efis failure) coincident with pitot icing -- which, of course, would be the worst possible time. all you really need to keep the greasy side down is needle/ball and airspeed, which are two of the simplest, cheapest instruments you can own. why would i not want to add something to help ensure i have the bare minimum in case of catastrophic failure of the other stuff?
i might go on to say that the probable reason i haven't had pitot icing more than those three times is that my checklist now includes "entering visible moisture -- pitot heat on". i don't have the studies to show it, but i believe that pitot icing can easily form in conditions that are not conducive to airframe icing, having experienced this twice myself.
i respect most of what george has to say, but i reserve the right to disagree with him on this.
mho,
i'm also going to disagree with george on this issue. i have experienced pitot ice in imc on three occassions (that i can distinctly recall) in the last 20 or so years -- only one of which was accompanied by any sign of airframe icing. it wasn't fatal in any of them (i think.)
but it is not inconceivable to me that one get a vacuum failure (or the modern day equivalent -- an efis failure) coincident with pitot icing -- which, of course, would be the worst possible time. all you really need to keep the greasy side down is needle/ball and airspeed, which are two of the simplest, cheapest instruments you can own. why would i not want to add something to help ensure i have the bare minimum in case of catastrophic failure of the other stuff?
i might go on to say that the probable reason i haven't had pitot icing more than those three times is that my checklist now includes "entering visible moisture -- pitot heat on". i don't have the studies to show it, but i believe that pitot icing can easily form in conditions that are not conducive to airframe icing, having experienced this twice myself.
i respect most of what george has to say, but i reserve the right to disagree with him on this.
mho,
gmcjetpilot
Well Known Member
Excellent point
My response to pitot ice is hell yea put it on if you NEED it. That is my point, do you (anyone) really NEED it. In your case mho you do.
IFR pilots know that ice forms on sharp or smaller objects first, such as a pitot tube, air temp mast sticking out the window or windshield wiper arm nut. Point taken. However I find when you are really in ice conditions you know it. Trace, nil ice is no big deal, a light frosting if you will. Ice is a fascinating phenomena. To categorize ice just as, clear, rime, mixed and trace, mod or severe does not do justice to it.
The scenario you stated, VAC failure AND in icing, pitot ice over, is bad. I would not want that. However I say its an unlikely multi failure (or failure at the worst time). However good point. Why not try to eliminate one issue. The next step is to have more safety margin, why not two: engines, alternators and Vac pumps.
You are making my point. A single engine (single pilot) platform is not the greatest thing to go bombing around in IMC. You assume some extra risk, and the heated pitot, although useful in some scenarios is not your biggest risk.
I am not accusing anyone, but reading the icing related accident reports and violations (for pilots who live thru it), there is either a cavalier attitude or ignorance how little pitot heat gives you in the way of real ice protection. Yes it keeps your pitot from freezing, but what about the rest of the plane. That was my point, but your point is very valid, why not?
To answer you question,
"Why would I not want to add something to help ensure I have the bare minimum in case of catastrophic failure of the other stuff?"
You have basically hit the nail on the head and also made my point. VFR pilots and equipped RV's don't need heated pitots. I think we agree. IFR pilots, who equip their RV with IFR equip and actually plan of filing and flying IFR should make a heated pitot top on the option list. WHY NOT?
IFR pilots who plan on occasional IFR departures or IFR enroute let downs, no hard IMC, may very well choose not to have a heated pitot. Why not? A lot of times in GA I filed an IFR flight plan (in VFR conditions) to avail myself of ATC and simplifying IFR flight procedures into busy airspace and airports. Sometimes I filed IFR to allow departure thru a low stratus to get to VFR conditions on-top. Other times I would get a "Pop-up" clearance for a IFR let down thru a solid under-cast to VFR. I did never needed heated pitot.
If you fly enough continuous IMC, even in summer, you see the trace ice on the windscreen. When I was CFII'ing in Single engine Cessna's, it was nice to turn on the only anti-icing device, the heated pitot. On the Cessna you can see the struts, pitot, OAT mast for ice accretion. You're flying along happily at 32F and than go thru a particularly wet cloud, getting quick frost over the wind screen, but it would sublimate quickly. Did the heated pitot help? I don't know? I never turned it off to find out. I am guessing not really, but it made me feel better. If I ever got real ice, my plan was getting out of in NOW.
I've been in moderate ice in piston planes flying Freight in a Seneca II's with known icing equip (boots, hot prop and window). I never was real comfortable with 1/8 to 1/4 inch of ice hanging of the plane. The plane slowed down with ice and required massive re-trim to maintain level flight. You never knew if the tail boots worked for sure. As the windows iced over, except for a 10" strip it was a little scary. If I flew a RV into some of the stuff I few in with that twin, I don't think I would have stayed in the air. Just be careful.
So for the record, I am not Anti heated pitot's, just anti-useless stuff on RV's that will not be used for the realistic mission the plane and pilot will fly. A heated pitot should never be the make or break item for safe IMC operation. If it is, you are not doing it right. G
Thanks mho for such a tactful well thought out reply. Opposing opinions, especially such polite ones are alway nice.johnp said:i'm also going to disagree with george on this issue. i have experienced pitot ice in imc on three occasions (that i can distinctly recall) in the last 20 or so years -- only one of which was accompanied by any sign of airframe icing. it wasn't fatal in any of them (i think.)
why would i not want to add something to help ensure i have the bare minimum in case of catastrophic failure of the other stuff?
i might go on to say that the probable reason i haven't had pitot icing more than those three times is that my checklist now includes "entering visible moisture -- pitot heat on". i don't have the studies to show it, but i believe that pitot icing can easily form in conditions that are not conducive to airframe icing, having experienced this twice myself.
i respect most of what george has to say, but i reserve the right to disagree with him on this.
mho,
My response to pitot ice is hell yea put it on if you NEED it. That is my point, do you (anyone) really NEED it. In your case mho you do.
IFR pilots know that ice forms on sharp or smaller objects first, such as a pitot tube, air temp mast sticking out the window or windshield wiper arm nut. Point taken. However I find when you are really in ice conditions you know it. Trace, nil ice is no big deal, a light frosting if you will. Ice is a fascinating phenomena. To categorize ice just as, clear, rime, mixed and trace, mod or severe does not do justice to it.
The scenario you stated, VAC failure AND in icing, pitot ice over, is bad. I would not want that. However I say its an unlikely multi failure (or failure at the worst time). However good point. Why not try to eliminate one issue. The next step is to have more safety margin, why not two: engines, alternators and Vac pumps.
You are making my point. A single engine (single pilot) platform is not the greatest thing to go bombing around in IMC. You assume some extra risk, and the heated pitot, although useful in some scenarios is not your biggest risk.
I am not accusing anyone, but reading the icing related accident reports and violations (for pilots who live thru it), there is either a cavalier attitude or ignorance how little pitot heat gives you in the way of real ice protection. Yes it keeps your pitot from freezing, but what about the rest of the plane. That was my point, but your point is very valid, why not?
To answer you question,
"Why would I not want to add something to help ensure I have the bare minimum in case of catastrophic failure of the other stuff?"
You have basically hit the nail on the head and also made my point. VFR pilots and equipped RV's don't need heated pitots. I think we agree. IFR pilots, who equip their RV with IFR equip and actually plan of filing and flying IFR should make a heated pitot top on the option list. WHY NOT?
IFR pilots who plan on occasional IFR departures or IFR enroute let downs, no hard IMC, may very well choose not to have a heated pitot. Why not? A lot of times in GA I filed an IFR flight plan (in VFR conditions) to avail myself of ATC and simplifying IFR flight procedures into busy airspace and airports. Sometimes I filed IFR to allow departure thru a low stratus to get to VFR conditions on-top. Other times I would get a "Pop-up" clearance for a IFR let down thru a solid under-cast to VFR. I did never needed heated pitot.
If you fly enough continuous IMC, even in summer, you see the trace ice on the windscreen. When I was CFII'ing in Single engine Cessna's, it was nice to turn on the only anti-icing device, the heated pitot. On the Cessna you can see the struts, pitot, OAT mast for ice accretion. You're flying along happily at 32F and than go thru a particularly wet cloud, getting quick frost over the wind screen, but it would sublimate quickly. Did the heated pitot help? I don't know? I never turned it off to find out. I am guessing not really, but it made me feel better. If I ever got real ice, my plan was getting out of in NOW.
I've been in moderate ice in piston planes flying Freight in a Seneca II's with known icing equip (boots, hot prop and window). I never was real comfortable with 1/8 to 1/4 inch of ice hanging of the plane. The plane slowed down with ice and required massive re-trim to maintain level flight. You never knew if the tail boots worked for sure. As the windows iced over, except for a 10" strip it was a little scary. If I flew a RV into some of the stuff I few in with that twin, I don't think I would have stayed in the air. Just be careful.
So for the record, I am not Anti heated pitot's, just anti-useless stuff on RV's that will not be used for the realistic mission the plane and pilot will fly. A heated pitot should never be the make or break item for safe IMC operation. If it is, you are not doing it right. G
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Blade accuracy
Kevin,
I have a encoder in my -6. I have never been reported by ATC at an altitude other than what I was indicating on my altimeter. As posted earlier, my indicated airspeed does read 5 mph low at stall and 5 mph high at 190 but dead on where it counts (again verified at pitot static check).
Regards.
Kevin,
I have a encoder in my -6. I have never been reported by ATC at an altitude other than what I was indicating on my altimeter. As posted earlier, my indicated airspeed does read 5 mph low at stall and 5 mph high at 190 but dead on where it counts (again verified at pitot static check).
Regards.
4kilo
Well Known Member
Checking your altimeter against the output from your altitude encoder is not any kind of test for static position error. If they are both plumbed to the same static source, then they will both be affected by exactly the same error. If they are on seperate static sources, and you KNOW one of the sources is accurate, then you can make some sort of inference of the error ONLY if you know the relative accuracy of the instruments.
This is what Keven H. meant about accurate static checking being rather difficult to accomplish. You might be able to get a rough idea by doing low altitude fly-bys of a runway at various speeds and noting the indicated altitude, but this is neccessarily a rather imprecise method. To get any really decent data, you would probably need to trail some sort of static bomb (lots of work for a rather small return).
If you are not flying hard IFR, small static position errors are not that important, but serious IFR can be dangerous with any major error. Also, any airspeed indications will also be affected by static errors, which is one of the reasons indicated airspeeds are so suspect for comparing aircraft performance.
Pat
Kevin Horton
Well Known Member
Low altitude fly bys are a recognized flight test technique to determine static system error, but you need to couple them with some sort of photographic method to accurately determine the actual altitude on each run, and you need some method to accurate record the indicated altitude at the moment the photo is taken. All in all it is not practical to use this method unless you have access to resources that most of us don't have.4kilo said:
The most practical method for us amateurs is a speed course method. This involves first doing an ASI calibration with a water manometer to determine ASI instrument error. Then you fly a box pattern at a constant IAS at altitude in smooth air, using GPS data to get the TAS. Use the TAS, the indicated OAT (corrected for instrument error and ram temperature rise) and altitude to get CAS. Correct the IAS for instrument error, and the difference between that and the CAS has to be due to static source position error, if we assume that the pitot error is zero. This is actually a pretty good assumption, unless you have done something stupid with your pitot tube, as they are generally not at all affected by position error.
You need to spend a few hours doing the ASI and temperature calibration, a few more hours doing the flight testing, and then a bunch of time crunching the data.
I've got a set of detailed instructions and spreadsheets in the Flight Test Links section on my web site.
