Static Blockage

NealRomeoGolf

NealRomeoGolf

Final Approach
Joined
Apr 12, 2016
Messages
5,640
Location
Illinois
Display Name
NRG
Learned a lot from this but am also still befuddled by it. Here's my story.

I own a 1975 Seneca II. Sometimes I use it to travel for work. Last week I needed a multi leg trip and it was much easier to do it myself instead of let United fly me.

While parked in Pittsburgh, Atlantic failed to heed my request for a hangar and my poor bird sat out in storms for two days. This was verified by sumping water out of my left tank during preflight. How water gets in is for another time.

I took off and bumped along for an hour until my fuel stop. Gassed up and took off for home. The headwind going west was awful so I had stayed down at 6k in the bumps. I had enough and asked to try 8k. As I passed through 7k, my airspeed started to roll back and back and back. My angle of attack was not severe enough to get to stall speed but the G500 Txi in front of me said so. I leveled off and watched my airspeed go to zero. A quick check of my traditional gauge also had it at zero. Crap.

Fly the plane. Pitch and power are your friend. I told ATC I was having an issue and needed some leeway on my climb. Started thinking through things. Pitot heat was on. Now which one is which. Pitot blockage means airspeed becomes an altimeter? Static blockage is airspeed goes to zero? Of course sadly I didn't quite remember. I pulled my emergency checklists to see if they had anything. Nope. Well, pitot heat was on. What else could I do?

Some of you are screaming alternate static source at this point. Well, my plane is old enough it doesn't have one. So then break the ASI? Don't have that either. The odd thing is that the G500 would go from a red X over the airspeed and then it would come back to some speed and then go back down.

Eventually my traditional ASI came back but the G500 didn't. That was confusing and disorienting. Why would one be ok and not the other. Same static source. The big learning came from my altimeter. The G500 said 8000 and when I asked ATC for verification, they agreed. My traditional altimeter would go up and down and did not match the G500. But the agreement with ATC made me trust the G500. Mistake on my part.

The G500 feeds the altitude encoder for the transponder which feeds ATC. They all conspire to make you think the G500 is accurate. In my case, the old altimeter was accurate and I should have trusted it. This made even more sense in hindsight when I got to Illinois and all the sudden I was in the soup. That wasn't supposed to be at 8k. Only 10k. Low and behold I had climbed up to 10k.

When I started my descent to home, I was so confused as to which gauge to trust. I powered back and pitched down and the G500 did nothing. So I knew I had to start trusting my traditional gauge. Got out of the soup and could see the ground getting closer despite the G500 disagreeing. Finally around 3300 the G500 snapped into place and wound quickly down from 8000 to 3300. ATC even noticed it. :cool:

I diverted to the big airport in town since our smaller field no longer has a mechanic. I needed two 100 hour ADs done anyway. Landed without incident.

Shop tested my pitot-static system and found nothing wrong. My static ports are on the sides of the fuselage back by the tail and not on the pitot tube. So I still dont understand how any blockage occurred in the first place. I also dont understand how the traditional gauges came back way earlier than the G500 ever did.

Lessons learned: my plane doesn't have an alternate static source. Didn't know that before this incident. Don't trust shiny glass over old gauges. And, if your shiny glass is wrong, your transponder is wrong too and ATC thinks you're somewhere else.

I also learned how disorienting it is to have conflicting instruments. They teach you that in training but it is mind blowing in reality.

Should I have declared an emergency? I still dont think so. ATC assisted me with what I needed and passed it along to the next controller. I wasn't in IMC at the onset and I knew I wouldn't need an approach at home.

So there's my almost emergency story.
 
Yowch. I had an alternate static installed, it's like a fuel drain just above the copilot's left knee...
The bad part is your moisture froze at a low point. You really did need that hangar....
 
bbchien said:
Yowch. I had an alternate static installed, it's like a fuel drain just above the copilot's left knee...
The bad part is your moisture froze at a low point. You really did need that hangar....
Click to expand...
The other thing I've been unable to find is my static drain. There's supposed to be something on the pilot side but I can't find it.
 
Thank you for sharing. Textbook...in that the textbook tries to warn us that we will become disoriented while we sort out the problem.

A question for any controllers that might read this one...when you have an aircraft experiencing altimeter/encoder issues (or the data is suspect) do you provide more space above and below that aircraft?
 
I agree that you didn't need to declare, since ATC didn't need to do anything special for you. Sounds like you handled it appropriately.

It sounds like the blockage was either at the tee where the static line splits to the G500 and the analog instruments, or in two places on either side of the tee, and the analog side cleared first. At the tee makes sense as there's usually some diameter change that could trap water.

What was the freezing level?
 
I have had two static blockages and two pitot blockages over the years. The first static was in a club Piper Arrow. It did have an alternate static and when I flew it up to the maintainance shop, I closed it on final so I could taxi up to the shop and show them the incorrect readings.

The second came when I was evacuating my plane from VKX after 9/11. Shortly after takeoff, I realized that the altimeter and airspeed were wonky. Told ATC and they essentially told me to stop altitude squawk and get out of their airspace. Landing at OKV, my only concern was figuring out if I was below the gear speed. This I figured out with the GPS groundspeed and the AWOS-reported wind. Amusingly, the mechanic wrote that he removed a "doober" from the static line. I'm not sure what pot head left it there (I believe it was supposed to be dauber).

Given a choice of what instrument to break in an emergency, most students pick the hobbs meter.
 
The concern is that you weren't at the altitude you & ATC thought you were. That could have led to you sharing airspace with another aircraft in the biblical sense. I would say it was probably worth declaring so that subsequent controllers would know to watch out for you. OTOH, that might've led to questions later about why you didn't land "as soon as practible". I don't think continuing to fly home was unreasonable at all. At the least, the difficulty should've been mentioned at each check in. The bit about the encoder is a good lesson for everyone that ATC doesn't know anything more about your altitude than what you (and your airplane) are telling them. I wouldn't have thought of that in the moment, either.

One thing you didn't mention, but Ron touched on it....GPS speed & altitude. My primary CFI had me practice landings with the airspeed covered, using pitch, power, and feel. After a few reps he also showed me that the GPS speed was also useful, taking winds into account. I have GPS speed and altitude displayed on my ipad as a "just-in-case" kind of thing. I also like GPS altitude above ground so in case the engine quits, I have a better reference than the nearest airport or tower as to when I'm going to be done flying.

I hadn't thought about water freezing in the static line, but that makes sense. I need to check if I have alternate static in the Lance. I think I do. A lot harder to get water in that mast under the wing. The RV14 factory configuration doesn't have a drain or an alternate source. I need to think about that. Alternate static valve probably worth adding. The tubing goes up before it goes down, making the port the drain. It would take a pressure washer to push water up and over the hump. I assume Piper did the same?
 
Dana said:
I agree that you didn't need to declare, since ATC didn't need to do anything special for you. Sounds like you handled it appropriately.

It sounds like the blockage was either at the tee where the static line splits to the G500 and the analog instruments, or in two places on either side of the tee, and the analog side cleared first. At the tee makes sense as there's usually some diameter change that could trap water.

What was the freezing level?
Click to expand...
What I failed to mention was it was the second flight of the day. Was completely fine during the first flight. Freezing levels were almost at the ground. If i remember correctly, 6,000 feet was in the teens and 8,000 wasn't much different.

I almost wonder if the water kept from freezing (since that is the theory) down in the bumps and once I hit smooth air it was able to freeze up. We'll never know unfortunately.
 
Glad you made it. I wonder if you should find the tubing low points and try to disconnect lines to drain. Maybe use a suction tube.
 
Jim K said:
One thing you didn't mention, but Ron touched on it....GPS speed & altitude.
Click to expand...
I always had GPS speed and that helped in the beginning. The issue was knowing what the headwind component was. Once you lose the G500 airspeed, you lose the wind component of the display as well. You also lose your VSI. My watch also has GPS altitude and maybe speed. But the conflicting altitudes really had me confused. And not putting two and two together about ATC seeing me at whatever the G500 said put bias towards just going with the altitude on the G500. Shouldn't have done that. My watch was saying different altitudes than that. I should have connected the dots faster, but your head does funny things when you're in the moment.
 
NealRomeoGolf said:
What I failed to mention was it was the second flight of the day. Was completely fine during the first flight. Freezing levels were almost at the ground. If i remember correctly, 6,000 feet was in the teens and 8,000 wasn't much different.

I almost wonder if the water kept from freezing (since that is the theory) down in the bumps and once I hit smooth air it was able to freeze up. We'll never know unfortunately.
Click to expand...
It may be that initially it froze somewhere that didn't completely block the line so it still worked. The on the second flight in the bumps it moved somewhere else before refreezing. It may be that the place where it froze was partially heated by the cabin heat so the water in the line was above freezing even while the OAT was at or below freezing.

Water freezes at 32° regardless of whether it's moving or not. The motion just changes the temperature distribution and thus where it freezes first.
 
Been there. While not perfect using your GPS altitude above the ground can get you in the ballpark and turned out to be a great tool. For sure enough to know the difference between being at 10k or 12k.
 
Wow. First, you handled it. Good. What comes next is NOT an indictment. Just observations…

1. Continuing flight whilst confused is not the best idea. I don’t care much for legalities, rules, what ever, that’s why I phrased it like that. Continuing flight IMC when you don’t gotta AND not sure of something… prolly not the greatest idea.

2. You should have declared. If nothing else, it puts YOU in the right frame of mind. I can’t even tell you how many times I’ve declared an emergency, ZERO paperwork. No body comes asking “was that REALLY an emergency?” My question to you, why not? Again, no rule says ya gotta blah blah blah, but why not? If there’s a compelling to NOT, I’m all ears.

3. Troubleshooting is HARD. You really gotta get back to basics and know the system COLD. The question isn’t how can this happen? What exactly HAS happened? Rather, what do I KNOW to be true. That isn’t troubleshooting. You were exactly right, pitch and power. You KNOW that to be true. If that was enough to get you in the clear and a place to land, that’s as far as it should go. Troubleshoot on deck.

THANK YOU for sharing! Congratulations on a successful outcome!
 
Yeah, been there too. After that I added mods to my plane (experimental...) to help: Cessna style static bulbs where the static lines come into the fuselage, alternate static source within reach of the pilot to select as needed, and a Dynon D3.
The thing I like about a D3 is it is entirely a GPS derived EFIS. It won't be exact for airspeed or altitude like pitot and static derived data, but it will remain completely unaffected by those failures.
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