Vacuum issue

[cowtowner]

So on the way back from KOSH I noticed my autopilot turning me to the right, adjusted the DG and it wouldn't stay, looked over at the suction gauge and it read zero.

No big deal I thought, hit the electric backup pump. It charged the lines for a second then nothing.

Got to hand fly the last 5 hours home.

I'm guessing it's a hose blown, going to the shop tomorrow.

Anybody else blow a hose? It is a 57 year old aircraft....

 

[Stewartb]

More likely a nylon fitting broke. Been there.

 

[Silvaire]

Unlikely that a vacuum hose would "blow" but could become disconnected or, as noted a cracked or broken fitting. Did you get much rain at Oshkosh? Because we once lost vacuum and it turned out the main filter was completely water logged. (leak at base of windscreen just above it)

 

[cowtowner]

Unlikely that a vacuum hose would "blow" but could become disconnected or, as noted a cracked or broken fitting. Did you get much rain at Oshkosh? Because we once lost vacuum and it turned out the main filter was completely water logged. (leak at base of windscreen just above it)

The plane and I survived the Saturday night storms, the cockpit cover was on but it was heavy enough it could have leaked, at one point in the tent I was chanting "there's no place like home" and clicking my heals. Nothing on the floor of the plane though.

 

[Dan Thomas]

Old airplanes often used aluminum tubing behind the panel for some of the vacuum plumbing. The aluminum corrodes and gets thin and implodes. All the vac stuff quits.

Or it could be that a hose fell off an instrument or the regulator.

 

[Albany Tom]

I want to make a joke here, about being careful that vacuum doesn't leak everywhere and mess up the plane, but I won't.

 

[Clip4]

Failed regulator

 

[danhagan]

So on the way back from KOSH I noticed my autopilot turning me to the right, adjusted the DG and it wouldn't stay, looked over at the suction gauge and it read zero

One of the top reasons I changed from the Tiger to an RV ... avionics better, cheaper and no more vacuum

 

[cowtowner]

So the A&P called yesterday

Both pumps are FUBAR'd

Going to replace the main pump and mark the standby INOP

Either I upgrade plane this winter or the panel

 

[Gary Ward]

So the A&P called yesterday

Both pumps are FUBAR'd

Going to replace the main pump and mark the standby INOP

Either I upgrade plane this winter or the panel

Do you know how many hours were on the pumps?

 

[Magman]

Word of warning here.

I met an aircraft that had a gyro failure that also took out the AP. At night; 4 tanks full and the AP is chasing the failing gyro and trying to roll the aircraft. Scary.

Fast Fwd. The pump had failed. The reason for this is an internal failure of one
of the gyros. A screw( ?) had left the unit and migrated to the pump. Good- bye pump! Since you really don’t know what failed first you will want to have hoses cleaned or replaced and the gyro operation verified. It is possible there is “stuff” hiding just waiting to take out your new pump.

Most systems only have a filter for the air entering the gyro. Air travels from the gyros to the pump. FOD can go along for the ride too. Some aircraft have a filter between the gyros and the pump to protect against failures like this. Why not ALL?

 

[cowtowner]

Do you know how many hours were on the pumps?

Looks like 450 hours on the main pump and still looking for the backup

375 hours have been put on the plane in the last 28 months since I purchased it.

The replacement was done in 2010

 

[cowtowner]

My plane has both filters that we are replacing and will blow out the lines

Word of warning here.

I met an aircraft that had a gyro failure that also took out the AP. At night; 4 tanks full and the AP is chasing the failing gyro and trying to roll the aircraft. Scary.

Fast Fwd. The pump had failed. The reason for this is an internal failure of one
of the gyros. A screw( ?) had left the unit and migrated to the pump. Good- bye pump! Since you really don’t know what failed first you will want to have hoses cleaned or replaced and the gyro operation verified. It is possible there is “stuff” hiding just waiting to take out your new pump.

Most systems only have a filter for the air entering the gyro. Air travels from the gyros to the pump. FOD can go along for the ride too. Some aircraft have a filter between the gyros and the pump to protect against failures like this. Why not ALL?

 

[Dan Thomas]

Word of warning here.

I met an aircraft that had a gyro failure that also took out the AP. At night; 4 tanks full and the AP is chasing the failing gyro and trying to roll the aircraft. Scary.

Fast Fwd. The pump had failed. The reason for this is an internal failure of one
of the gyros. A screw( ?) had left the unit and migrated to the pump. Good- bye pump! Since you really don’t know what failed first you will want to have hoses cleaned or replaced and the gyro operation verified. It is possible there is “stuff” hiding just waiting to take out your new pump.

Most systems only have a filter for the air entering the gyro. Air travels from the gyros to the pump. FOD can go along for the ride too. Some aircraft have a filter between the gyros and the pump to protect against failures like this. Why not ALL?

My plane has both filters that we are replacing and will blow out the lines

Those two filters won't protect the pump from stuff out of the gyros. The main filter cleans the air from the cabin being drawn into the gyros. The regulator filter cleans the air from the cabin being let into the pump to govern the vacuum pressure. I have not seen filters for the overall airflow going into the pump, other than a screen, in some.

Now, a pump that suddenly craters generates a lot of carbon dust and tiny fragments. There is vacuum in the cases of the heading and attitude indicators. They act as little vacuum tanks. That vacuum can suck the carbon debris out of the busted pump all the way up those lines and into the gyros, where it not only creates gyro problems, but also gets sucked into the new pump, sometimes busting it, but at least shortening its life. Those hoses need to be checked for debris, at the very least.

 

[Magman]

The aircraft that I described the failure on was a 75( ?) Pathfinder ( PA-28 -235).
Following that episode I saw a “ similar “ aircraft ( maybe a Six) with a filter protecting the Pump. It’s unknown to me whether it was a factory item or a mod. Sure looks like a good way to spend a few bucks in return for added safety and possibly saving BIG bucks.

Pump swap time could be a good time to change hoses rather than blow out. I’ve seen really ancient hose that are crumbling internally. That goes to the Pump also. What is the recommendation regards gyros after a Pump failure?

btw- There are still a couple Wet Pumps from 1966 & 67 that are doing just fine.