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Tip: Mounting a Piper Blade Pitot

Ironflight

VAF Moderator / Line Boy
Mentor
I got a Private Message asking about how I mounted the Piper Blade-style Pitot on the Valkyrie, and as this was not the first time I had been asked, I figured that I might as well answer where it can be seen by others. The bottom line was that this was really easy to do. The blade is designed to mount on a flat surface, so all I needed to do was pick the surface and make sure it was stable. I decided that I wanted to keep it close to Van's design pitot position, and the best place I could find was just outboard of the rib that is just outboard of the aileron bellcrank access. I simple made a doubler for the skin (before the skin was mounted), and test-fit the pitot. I added nut plates (not in these photos), and the structural part was done. (You can see the doubler plate and hole for the pitot.)

pc200016lb1.jpg


Since this was a heated pitot, I was a little concerned about hooking up a nylon or plastic line to the metal assembly, so I rigged a test by putting on a short segment of line and hooking the pitot up to the power supply (with the resistor I planned to use to control the current. In a few seconds, it got hot enough to smell. In thirty seconds, the nylon melted off. I decided to use a metal tube all the way to the wing root! This photo shows the roughed in connection I made. I ran the line next to the spar, under the bellcrank pivot to make sure there was no danger of interfering with the controls. At the first Condition Inspection, everything was still in good shape.

pc160011ju5.jpg


Like I said up front - pretty simple!

Paul
 
Did you try to use the static port?

I also used a Piper pitot blade. It was a heck of a lot cheaper than any other heated pitot and it even includes static port heat.

Which brings me to my point. I used the static port on the blade and it worked fine, or at least good enough for me. It's accurate in level flight but in a power-on stall or full flap stall it indicates 45 MPH at the break instead of 50. Power-off, clean, it stalls at 55 like any other RV6.

However, I've read of other people using a Piper blade who had an error of as much as 20 mph even in level flight and had to switch to the standard static ports. The difference seems to be the angle at the bottom of the blade. I have no idea which one I've got or what model it came off of.

It looks like you didn't use the static port. Did you try and it didn't work in your case? We could compare the angles.
 
thanks Paul!

Paul, Thanks for posting this - it helps a LOT! :D

I bought a Piper heated pitot tube from ebay (supposedly from a Lance). It has 2 elements - I thought they were "Low" and "High" not heated pitot and heated static? I measured the resistance (don't have the numbers handy) and it looked to me like it was low/high. I haven't yet turned it on.

Two questions:
Why are you using a dropping resistor (it must get hot too)?

Would it be better if the doubler plate extended up under the the spar or rib and picked up those rivets? That would make it sturdier but perhaps it is OK just on this skin? I'm just wondering since the bottom skins are so thin.

To all you experienced builders - keep posting these tips. It makes it easier on those who come behind and will push that Vans Hobbs meter up even higher!
 
Jon - I didn't even try using the static port because I had heard a number of folks say that they didn't have good luck with it. It's good to hear that it is fairly accurate for you - I just decided not to gamble on it, and might have been over conservative. I had enough exposure to the potential horrors of finding good pitot and static locations over the years that I figured I'd use the tried and true for this plane.

Dave - I used the dropping resistor because when I first hooked the thing up it drew a lot more current than I wanted. I seem to remember doing some research on what Piper did, and decided to current limit it with an appropriate series resistor.

It certainly wouldn't hurt to extend the doubler plate to pick up stronger attach points, but since I had a QB kit, I really didn't have an easy way to do that. In any case, I've got 380 hours on the installation, and no signs of deformation or fatigue. I think it's sufficient.

Paul
 
One thing RV builders should be aware of is that there is many different part #'s for the piper blade style pitot.
At least one of the differences is the angle on the bottom of the blade which contains the static port.
All of the blade pitot installations on RV's that I am aware of, have erroneous airspeed readings at the low end. It is possible that one of the specific part #'s works correctly on an RV but I am not aware of one.
 
rvbuilder2002 said:
One thing RV builders should be aware of is that there is many different part #'s for the piper blade style pitot.
At least one of the differences is the angle on the bottom of the blade which contains the static port.
All of the blade pitot installations on RV's that I am aware of, have erroneous airspeed readings at the low end. It is possible that one of the specific part #'s works correctly on an RV but I am not aware of one.

You'e correct Scott - there are quite a few differnt models. I actually figured out which one I have one time, but can't find that particular scrap of paper right now - I'll have to try and dig it out some time. I can tell you that whichever one I have, my airspeed is very accurate throughout the range, with a stall right where the specs say it will be (about 53 knots at gross). Just lucky I guess.

Paul
 
Ironflight said:
You'e correct Scott - there are quite a few differnt models. I actually figured out which one I have one time, but can't find that particular scrap of paper right now - I'll have to try and dig it out some time. I can tell you that whichever one I have, my airspeed is very accurate throughout the range, with a stall right where the specs say it will be (about 53 knots at gross). Just lucky I guess.
The different angles on the bottoms of the various Piper pitots will affect the static pressure from them, but it shouldn't affect the Pitot pressure.

Pitot tubes are pretty hard to mess up, as the laws of physics are working in our favour. They measure the total pressure, and Bernoulli's Law tells us that the total pressure stays the same, even as the local velocity and local static pressure change. As long as a pitot tube is mounted well clear of the boundary layer, out of the prop wash, not in the wake of anything else, and roughly aligned with the air flow it should work properly, and give the expected accuracy. It doesn't matter whether it is a Piper pitot, a Dynon pitot, or a bent piece of aluminum tube, etc.

Static ports are a whole different problem. Now Bernoulli's Law is working against us, as it tells us that the local static pressure changes as the air accelerates and decelerates around the aircraft.

So, given that Paul used Van's standard static source, the fact that he has good airspeed accuracy with a Piper pitot should not be a surprise.
 
jonbakerok said:
Which brings me to my point. I used the static port on the blade and it worked fine, or at least good enough for me. It's accurate in level flight but in a power-on stall or full flap stall it indicates 45 MPH at the break instead of 50. Power-off, clean, it stalls at 55 like any other RV6.

However, I've read of other people using a Piper blade who had an error of as much as 20 mph even in level flight and had to switch to the standard static ports. The difference seems to be the angle at the bottom of the blade. I have no idea which one I've got or what model it came off of.

Ah Yes...
I should have been more specific.
I was primarily relating to Jon's post (above) about airspeed indications being incorrect at the low end.
What I should have said was "All of the blade pitot installations on RV's that I am aware of, that have used the internal static port, have erroneous airspeed readings at the low end."
I agree with Kevin. Pitot is pitot. As long as you stay out of accelerated or disturbed airflow (prop. slip streem, etc.)

Now there may be a specific part # Piper blade that will work using the internal static port but I am not aware of one.

The best way to be sure that your system will be accurate, is to use the blind rivet ports supplied by Van's.
 
Last edited:
Wires along pitot in Paul's RV-8

Paul: I would like to know if the wire bundle that is shown in the picture of your pitot setup carries enough wiring to power your nav lights, landing lights, and strobes. My wing is also QB, and I don't feel compelled to install a conduit, as the grommets are already installed.
TN
 
Tom Navar said:
Paul: I would like to know if the wire bundle that is shown in the picture of your pitot setup carries enough wiring to power your nav lights, landing lights, and strobes. My wing is also QB, and I don't feel compelled to install a conduit, as the grommets are already installed.
TN


Tom,

Sorry - that wire you see in the photo is only the strobe cable. I wanted that separate from the rest of the wing wiring (like antenna Coax), so I ran the strobe through the grommets that Van had already installed in my QB wing, and ran a separate wire tray for everything else.

Paul
 
jonbakerok said:
I also used a Piper pitot blade. It was a heck of a lot cheaper than any other heated pitot and it even includes static port heat.

Which brings me to my point. I used the static port on the blade and it worked fine, or at least good enough for me. It's accurate in level flight but in a power-on stall or full flap stall it indicates 45 MPH at the break instead of 50. Power-off, clean, it stalls at 55 like any other RV6.

However, I've read of other people using a Piper blade who had an error of as much as 20 mph even in level flight and had to switch to the standard static ports. The difference seems to be the angle at the bottom of the blade. I have no idea which one I've got or what model it came off of.

It looks like you didn't use the static port. Did you try and it didn't work in your case? We could compare the angles.

Jon,
The static port on the Piper "blade style" pitot tube works better if the pitot is mounted 8" rearward from the main spar. As noted by other listers, there are numerous differing part numbers for Piper blade pitot tubes. They differ in the angle on the bottom of the blade. This angle difference is to correct out, any static port error.
I plan to use the heated static port as a "heated back up" static source. I will correct any static error by changing the angle on the bottom of the blade. This will be simple to do by comparing the read out with the stock Vans static port readings. Changing the blade angle will correct any error.
FYI, RV-9A builder Peter Laurence discovered a source of reasonably priced replacement heating elements for these pitots.
Here is the info. Heaters are made by Hotwatt

;) Http://www.hotwatt.com/cartridg.htm

Hotwatt part #s


For Pitot: 13A7025 70 W 12V


Static 13A7026 100W 14V


Piper part #s


464-356 for the 70W 12V


464-357 for the 100W 14V


These are called cartridge heaters. They are 3"X 3/16" and 4"X 3/16"


Check the ceramic plug where the wire enters the cartidge. If there's any movement of the wire, it should be replaced.

Charlie Kuss
 
chaskuss said:
Jon,
The static port on the Piper "blade style" pitot tube works better if the pitot is mounted 8" rearward from the main spar.

Not sure I buy that. Since the RV airfoil is rounded on the bottom, it would cause the pitot tube to be angled downward instead of directly facing into the relative air. I guess that might reduce the static error if the wrong blade was used but it seems to me like it would increase the pitot error, especially if you found you needed to switch back to the fuselage static source. Better to use the correct blade to begin with.

Mine works fine and it's mounted almost on the spar, very close to where Paul's is in his pictures. I used that location because it approximated the location on the Cherokee I was flying at the time. I don't recall seeing any part number on it, but if someone could verify that it's there somewhere, I might be willing to remove mine to take another look. Or maybe it would be enough to just measure the angle on the bottom.

I bought mine from Wentworth salvage. It came "reconditioned", meaning they had already replaced the heater elements. I didn't specify a part number, but just asked for a Piper pitot mast and got lucky. I think I paid about $100 (5 years ago).
 
chaskuss said:
FYI, RV-9A builder Peter Laurence discovered a source of reasonably priced replacement heating elements for these pitots.
Here is the info. Heaters are made by Hotwatt
;) Http://www.hotwatt.com/cartridg.htm
Hotwatt part #s
For Pitot: 13A7025 70 W 12V
Static 13A7026 100W 14V
Piper part #s
464-356 for the 70W 12V
464-357 for the 100W 14V
These are called cartridge heaters. They are 3"X 3/16" and 4"X 3/16"

Check the ceramic plug where the wire enters the cartidge. If there's any movement of the wire, it should be replaced.

Charlie Kuss

Hi Charlie - thanks SO MUCH for posting this great info. I just got my piper heated pitot from ebay and I noticed some wire movement. I want to address this before I mount the pitot.

Looking at the hotwatt site, I couldn't find the part numbers you referenced. I did find the SC18-3 and SC18-4 which are 3/16 x 3" and 4" standard cartrigde heaters (70 & 90 W). I don't think those are the right ones because they are rated at 3.5 Amps (max) from 120V.

Also, how are the heating elements attached in the mast?

Thanks for any info,
 
Dave,
I purchased my heated pitot off of Barnstormers about 5 years ago for $75. I was lucky. Both heater elements work on my unit. My friend, Peter Laurence, purchased a used unit which was fully functional UNTIL he sent it to a vendor (initials PD) who wanted to inspect it. The vendor wanted to investigate copying this unit. For his kindness, Peter got his unit back damaged. :-( He did the research and repaired his unit. I suggest you contact him at [email protected] for more info.
Hotwatt does not have a search function that I could find on their web site. You might want to email them with the listed part numbers to see if they are valid.
Charlie
 
How to remove the elements in the piper mast?

Gents,

I searched on this thread and found it very useful. I need both elements replaced in my mast, but cannot figure out how to get them out of the mast? I've broken the wires off the elements trying to pry the cartridges out.

Any hints?

Art Treff
N666AT RV-8 Fastback
Flying
 
Oh, one more thing....on the Piper mast

I notice that my piper mast came from the salvage company with brass NPT fittings into the mast with barb fittings on the aircraft side. What type of hose does Piper use to hookup the mast?! Mine (like Paul's) melted hi temp polyurethane LeGris tubing within minutes when I powered up both elements.

Since I"m using both the static as well as the pitot fittings, standard AN flared fittings do not fit well between the elements. What have you guys done?

Also, I still would like advice on how to remove the cartridge elements.

And, according to Hotwatts' website, I can't find 13A7025 and 13A7026 in cartridge elements.

Art Treff
 
Thought I'd posted this before, but...

I can't find it. You can get a rebuild kit from Air Parts of Lock Haven. Here is what you get for about $120:


As for removing the old heaters, I was able to pull mine out with pliers. They were held in by friction, dirt, and peened edges of the mast holes. The guy at Lock Haven told me to use the highest temperature silicone (Copper colored) to hold the new ones in. Just slide them in and goop the top. I recommend you do this after installing the tubing fittings, due to limited tool room.

I am using solid AN tube all the way from the wing root to the pitot tube. You can buy a fitting to go between AN and the tapered threads in the tube housing.


Hope this helps,
 
My Heated Pitot Mast rebuild

I checked Hotwatt and called them regarding their cartridge heaters. Lack of good information from them and fear of overheating/underheating the pitot/static mast, drove me to go the gen-u-wine piper replacement parts.

So, I called Airparts of Lockhaven and talked to their Pitot Mast rebuilding guy, who sez:

-Usually you cannot pull the elements out, he usually drills them out.
-Attachment backin the mast is staking on the outside of the element.
-The elements are rated up to 200C, so not many glues will hold it in.
-Standard aircraft rubber hose is all that is installed onto the barbed fittings screwed into the mast. (I confirmed this on a friend's Piper Arrow).
-Elements are wired in parallel, no high/low switch or resistors are used.
-The mast is designed to prevent ice while travelling at speed, do not power it up on the ground execpt for a few seconds, but it will not melt the hose
-Wires provided should not be shortened-they are 20AWG that is rated to 200C.-keep the 12" length provided onthe elements, at that length, standard butt splices/knife connectors can be used.

I did an experiment to confirm that the wires/hose will not overheat when powered up in flight. I immersed the bottom of the pitot mast in water and turned it on. To me, this simulates 200mph wind taking the heat away. Wiring stayed cool as did the hose and fittings.

As far as aftermarket elements, I'll tell you what was inked onto the cartridges in the Piper rebuild kit. Both are 3/16" diameter. One is 3" (3.25" if you include the part that sticks out of the mast when installed) the other is 4" (4.25").

3"
FastHeat JK
CS18545
70W 14V

4"
FastHeat JS
CS18543
100W 14V

I had no luck finding these part numbers on the Fast Heat website. I already have heaters working, so my research is done. If someone locates these Fast Heat pn's please pass them along to the rest of the group.

Art in Asheville
N666AT RV-8 Fastback
70+ hours.

The 3"
 
Piper Pitot tube

Hi Paul, did you figure out which model of blade style pitot tube you used. I would also like to use the blade style pitot tube that Piper uses but have not been able to find a correct part number and source yet. I am building an F1 Rocket so the one you used should be perfect.
I would appreciate any advice you can offer. Regards, Tony
 
Good Part Numbers for Piper Pitot Heater(s)

I broke off one of the leads screwing around with methods to connect the bare leads from one of the heaters. So I'm in the middle of digging out the old heaters. They do not want to come out easy.

Then I realized that I need 28V cartridges (DeltaHawk Diesel), so it may be good that I need to repair the unit. I've ordered a long #13 drill bit and a 3/16" reamer to finish the holes.

The problem is that both suppliers require three of each heater to ship. One of them will allow both the 24V cartridges to count toward the minimum order. Airparts of Lock Haven will sell a 28V system repair kit for $200.00. Seems like the price went way up over the past 7 years.

So, I think I will buy the minimum number of heaters and then try to sell the extra two sets. Is anyone interested in a set of heaters, especially if you need 28V units.

I plan to use the static port as alternate static air. As soon as I receive a #13 Drill Bit and a 3/16" reamer, I will report on the complete repair of the heating elements.
 
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