Interesting fault

[Yenn]

I went flying today. pre flight all was normal, but we have had rain in the last two days.

 

Take off was normal except that at about 100' the ASI gradually descended to zero kts. Nothing on the scale on downwind and then in the approach at what I reckon was 70 kts and normal it suddenly started showing 100kts.

 

I havn't had time to track down the fault, but it has odd symptoms.

 

A very gentle blow into a loosely fitted plastic pipe on the pitot gave a good speed indication on both ASIs

 

Hopefully I will find time tomorrow to chase this down.

 

 

[crashley]

water in static or pitot tubes

 

 

[gandalph]

Water in the static air line?

 

 

[gandalph]

Well that's gotta be a dead heat for answering. eh Crashley?

 

 

[Ultralights]

water, or bugs.

 

 

[ben87r]

Had similar a while back but was on the ground roll not increasing till 60-70kn. Was water in the static.

 

 

[old man emu]

DON'T EVER BLOW INTO A CONNECTED PITOT TUBE unless you have the time and money to invest in replacing the pressure instruments. Disconnect the line from the instruments, and only then can you blow back towards the pitot tube.

 

Suggestion: If you leave your airplane in the open consider inserting an in-line joiner near the pitot tube. That way, you can pull the pitot tube off, plus a shortish length of tubing, to make blowing the pitot out easier.

 

Be on the lookout for insect activity in Spring. Mud-daubers and wasps are looking for places to set up their nurseries.

 

OME

 

 

[Yenn]

No water in the lines as far as I could tell. Pitot lines tested OK. Static line was completely blocked up. There are two static inlets, one each side of the fuse just ahead of the tail. Very hard to get at the inside of the vent, which is a pop rivet, throuh the skin and expanded inside the plastic pipe. I checked at every join, and guess what. The problem was right back in the rear of the fuse. Disconnect the elevator linkage and worm my way back there and the very last piece of tube on each side was blocked. I removed it all and found in the Tee connection, what looked like grease and after getting it on my lips it tasted like locktite, very sweet.

 

Now it is all cleaned up and I am modifying the vents to allow easier maintenance in the future. It was not funny getting in that skinny, rough edged aluminium tube.

 

I still cannot see how a blockage could cause the symptoms I had. Time will tell.

 

 

[old man emu]

Sometimes I try to be amusing, but when I'm talking about looking after an airplane, I am being serious. So how could my post (No 7 above) be called funny?

 

OME

 

Bloody Win 10. Now its changed the keys so that if I try <Shift> <hash> I get this: £

 

 

[Robbo]

Should just download the windows 7 iso :) I am buying a new lenova tomorrow for $340 its only a celeron but doesent matter, there is a higher model for $150 more that comes with Windows 7 and an i3 but Lenovo had a virus in there bloatware so all the recovery media is infected, so will save $150 and get the lower spec one with Windows 8.1 and just reinstall Windows 7 on it from a clean iso. I have an old windows 7 pc so can just use the product key from that.

 

That way by doing a clean install it will be completely free of bloatware and viruses.

 

 

[crashley]

If an aircraft begins to climb after a static port becomes blocked, the airspeed begins to show a decrease as the aircraft continues to climb. This is due to the decrease in static pressure on the pitot side, while the pressure on the static side is held constant.

 

A blockage of the static system also affects the altimeter and VSI. Trapped static pressure causes the altimeter to freeze at the altitude where the blockage occurred. In the case of the VSI, a blocked static system produces a continuous zero indication