Piper Pitot/static mast

Areeda

Areeda

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Areeda
I am wondering about the 3 holes in the mast, the one facing forward is obviously the pitot but we're having a discussion about which one is the drain and which one is the static port. I think the drain is on the bottom and the static port faces aft, my friend says I have them backwards.

Does anyone have a drawing they can upload?

Joe
 
Joe I'll check my POH and see if they have one there.
Dave G
 
Dave,

We've searched the POH but it's not that specific. I think it requires the maintenance manual which I don't have.

Joe
 
Areeda said:
Dave,

We've searched the POH but it's not that specific. I think it requires the maintenance manual which I don't have.

Joe
Click to expand...

I just sent you a PM with a link to the parts and maint manuals for a Warrior.

Allan
 
According to my copy of the Parts & Maintenance manuals, you are correct.
 
alindsay said:
I just sent you a PM with a link to the parts and maint manuals for a Warrior.

Allan
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Thank you Allan.

Actually it seems we were both correct

pg 2H13 Maintenance Manual said:
The static air system consists of interconnected static ports on the underside and aft side of the (pitot) static mast. The ports are connected to the airspeed indicator, altimeter, and vertical speed indicator by hoseing and tubing routed through the wing.
Click to expand...
 
Ok so the two holes are connected - they have to be if one of them is a drain. I stick by my contention that the primary function of the bottom hole is a drain, but when the drain isn't "draining" it's clearly a static port like the one to the aft.
 
TMetzinger said:
Ok so the two holes are connected - they have to be if one of them is a drain. I stick by my contention that the primary function of the bottom hole is a drain, but when the drain isn't "draining" it's clearly a static port like the one to the aft.
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You're both right, ya know. If you want to put in a drain on the static line it's going to be open to the static line.

Now, how do they keep water out of the pitot line?
 
smigaldi said:
There is a drain in the cockpit that is to be drained each annual.
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Actually that is on our checklist to be drained before each flight.

I may add it to the in flight checklist if weird pitot/static instrument indications happen.
 
smigaldi said:
There is a drain in the cockpit that is to be drained each annual.
Click to expand...

Areeda said:
Actually that is on our checklist to be drained before each flight.

I may add it to the in flight checklist if weird pitot/static instrument indications happen.
Click to expand...

Old ones like mine don't have the user actuated drain. I don't even have alternate air.
 
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mikea said:
Old Ones like mine don't have the user actuated drain. I don't even have alternate air.
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How old is yours?

I don't have an alternate air source either. I *think* Piper did not do that is that our static sources are on the pitot/static mast and that is heated so the feeling was that it would not freeze up.
 
smigaldi said:
How old is yours?

I don't have an alternate air source either. I *think* Piper did not do that is that our static sources are on the pitot/static mast and that is heated so the feeling was that it would not freeze up.
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1968. I have alternate air if I break the glass on an instrument. :sosp:
 
I'm having a hard time seeing how an opening on the rear side of a pitot mast wouldn't see a lower pressure than ambient when the airplane was flying.
 
Had my first blocked static system event in flight last week. Took off after heavy rain storm, flew through more rain, and started getting weird indications on airspeed, altimeter, and VSI. Switched to alternate source, all returned to normal. It cleared up after getting on the ground - apparently got water in the system.

Odd, never had an issue in rain before.

Plane is due for static system check in Sept, so it'll be on the list for extra-close review.
 
gismo said:
I'm having a hard time seeing how an opening on the rear side of a pitot mast wouldn't see a lower pressure than ambient when the airplane was flying.
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Same here. When i took my fluid mechanics class in college, my professor had experience with aircraft design, and explained that the static hole is typically on a surface parallel to the air flow. Based on that, i would guess that the bottom hole is for the static, and the rear for drain. But if they are both connected, then its 6 of one, half a dozen of the other.
 
I hadn't really thought about it before. I always figured the back one was the static and the bottom was the drain. But if I had thought about it I would have reallized the back one would act like a the total energy port we use on sailplanes. So to be a true static it just about has to use both.

Brian
 
Actually the 2 openings one on the bottom and the one on the back of the mast combine to comprise the static source. Piper discovered that they could get a more consistent Pitot source under the wing than out in total free stream air and angle of attack changes. Normal Pitot tubes tend to close of the opening as the air enters at a oblique angle making the airspeed indicator less accurate in slow speed flight. A similar effect is achieved with the static port located on the same mast. Note how the bottom of the mast is slanted slightly away from the bottom of the wing this is the net airflow under the wing and combined with vent in back again makes a more true static source than many other options. The fact that an downward facing opening could allow moisture above to drain is mostly irrelevant to the design. Some Piper aircraft have drains inside the cockpit which are only open when activated by the pilot.
 
Cubpilot7 said:
Actually the 2 openings one on the bottom and the one on the back of the mast combine to comprise the static source. Piper discovered that they could get a more consistent Pitot source under the wing than out in total free stream air and angle of attack changes. Normal Pitot tubes tend to close of the opening as the air enters at a oblique angle making the airspeed indicator less accurate in slow speed flight. A similar effect is achieved with the static port located on the same mast. Note how the bottom of the mast is slanted slightly away from the bottom of the wing this is the net airflow under the wing and combined with vent in back again makes a more true static source than many other options. The fact that an downward facing opening could allow moisture above to drain is mostly irrelevant to the design. Some Piper aircraft have drains inside the cockpit which are only open when activated by the pilot.
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Now that's a helluva 1st post...... Welcome aboard!
 
Welcome. "Normal pitot tube" .... There are more pitot tube designs than aircraft types, what's normal? Ones with no static hole (s)/ ports, heated ones that have static holes/ports to vent the heated cavity, ones that have static holes/ports that provide input to instruments?
 
GlennAB1 said:
Welcome. "Normal pitot tube" .... There are more pitot tube designs than aircraft types, what's normal? Ones with no static hole (s)/ ports, heated ones that have static holes/ports to vent the heated cavity, ones that have static holes/ports that provide input to instruments?
Click to expand...
You know... If you had a nickel for every nit you picked...
 
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