Andair fuel pump blows fuse. RV-9A

[ron sterba]

Hi Bevan, good point, I think I'll leave the 4th party and head to the airport. Be back in 30 minutes.

Ron in Oregon

[ron sterba]

Ok one hour 3 minutes iam back. I checked and have 4feet of 16 gauge wire. FAA 43:13 book says 6amps continuous at 16 gauge would be max length 17 feet. Intermittent usage of AWG 16 @ 6 amps is 30 feet. Andair General Specification says 11-16.6 VDC 6 max amps/ 4.5 AMPS NORMAL NOW IN THE Andair Operational Manual it states to use a 5 AMP ,,,,,BREAKER,,,,,,,.. SO MY FUSE IS OUT! I learned something-here from you guys and that's a good thing!!!!! Now In the GENERAL OPERATION - Pump ( info sheet from Andair) "Once power is applied the pump will initially pump at 100% power then settle back to 75% power after 2 seconds. This is so that pressure in the line is built up quickly". As I explained earlier of my experience in pump noise sequences this would be right on the 100% and 75% cycles. I'm a little gray in the area of how long to I apply the boost pump switch, do I look at the fuel pressure gauge on the Dynon EFIS ? ( what should I be looking for in the fuel pressure reading, climbing, steady,??). At what point should consider switching off boost pump and then attempting to start my XIO-320?

My next question would be,,,,,,,,,,, if I'm flying and want to which tanks,,,how long before I move the selector knob to I turn on the boost pump, and how long after the selector to the new tank should I continue operating the pump? I know the engine has a engine driven pump. But can you explain how you do the switchover.

Thanks Ron in Oregon

Ron in Oregon

[ron sterba]

Charlie you say 6amp circuit breaker, my spec sheet shows 5 amp breaker. Maybe Andair changed the operating circuit breaker value. I'm thinking a search here might reveal somethingfromthe past,somethingishould have checked first. Thanks Charlie

[Captain_John]

My Andair pump went Tango Uniform in the first 5 hours also.

Maybe this should be another poll thread like the alternator thread?

Anyways, what Andair told me was that the vanes need to be fitted properly in order to determine how much current this little bugger will draw. The more friction and closer tolerance on the vanes, the more current it will pull in order to spin the motor.

So, I have the VPX system and can see the actual current draw. In normal operation it is 4.5 amperes. When I was having the problem, I got an alert in the vicinity of 14 amperes. That tripped out the circuit on the VPX and I landed uneventfully on my mechanical pump. When I removed it from the plane and retested it on the bench, I saw a short circuit according to the VPX (which I used to power the unit while it was on the bench so I could monitor the current and switch it on and off effectively). Current was over 20 amperes on subsequent tests and the rotor did not spin.

Andair took it back, gave it some TLC and it has now been working fine for 1.5 years and 420 hours (yes, you read that correctly... 420 hours in a year and a half)!

With regard to your fuse size... 5 or 6 amperes is fine. If you pull over that you have a problem and need to send it back. The surge current on start should not blow a 5 ampere fuse. It is an AC brushless motor and in my observations it really doesn't spike the current on start.

When mine went back to merry old England I was fortunate to borrow a pump from another fellow builder and fly on until it was returned. It did take about one month for post and bench time.

Sorry for the bad news. You must send it back to be repaired.

You will be glad when it comes back. It is a good little pump and the filter is very effective! In operation I see 29-32 PSI and current is always stable at 4.5 amperes.

Good luck!

CJ

[Captain_John]

Originally Posted by ron sterba

Ok one hour 3 minutes iam back. I checked and have 4feet of 16 gauge wire. FAA 43:13 book says 6amps continuous at 16 gauge would be max length 17 feet. Intermittent usage of AWG 16 @ 6 amps is 30 feet. Andair General Specification says 11-16.6 VDC 6 max amps/ 4.5 AMPS NORMAL NOW IN THE Andair Operational Manual it states to use a 5 AMP ,,,,,BREAKER,,,,,,,.. SO MY FUSE IS OUT! I learned something-here from you guys and that's a good thing!!!!! Now In the GENERAL OPERATION - Pump ( info sheet from Andair) "Once power is applied the pump will initially pump at 100% power then settle back to 75% power after 2 seconds. This is so that pressure in the line is built up quickly". As I explained earlier of my experience in pump noise sequences this would be right on the 100% and 75% cycles. I'm a little gray in the area of how long to I apply the boost pump switch, do I look at the fuel pressure gauge on the Dynon EFIS ? ( what should I be looking for in the fuel pressure reading, climbing, steady,??). At what point should consider switching off boost pump and then attempting to start my XIO-320?

My next question would be,,,,,,,,,,, if I'm flying and want to which tanks,,,how long before I move the selector knob to I turn on the boost pump, and how long after the selector to the new tank should I continue operating the pump? I know the engine has a engine driven pump. But can you explain how you do the switchover.

Thanks Ron in Oregon

Ron in Oregon

Your wire size and length is fine. Try the 5 ampere FUSE for now. I bet that you would be fine there as well.

Run your engine like it is a Piper Arrow.

Cold start = Full power and full mixture and hit the boost pump for 3 seconds to develop 18 or so PSI on the system. Pull power to idle and crank the engine. It will start up just fine.

Lycoming says that the boost pump must be operated while switching tanks and Piper has put that into their manuals as well.

In practice... meh

The engine needs an uninterrupted fuel supply and the mechanical one does just fine. Me??? I follow the Lycoming instructions and turn the boost pump on, watch for a climb in pressure, switch tanks and then shut boost pump off.

Have fun in Phase 1!!! It is what you have worked so hard for! Enjoy the testing!

CJ

[rv7charlie]

Originally Posted by ron sterba

Charlie you say 6amp circuit breaker, my spec sheet shows 5 amp breaker. Maybe Andair changed the operating circuit breaker value. I'm thinking a search here might reveal somethingfromthe past,somethingishould have checked first. Thanks Charlie

I just googled it; I think this was the page I looked at; found through a/c spruce:
http://www.aircraftspruce.com/catalog/pdf/PX375-TC.pdf

An interesting data point: The 28 Volt version's data sheet, from Andair's web page:
http://www.andair.co.uk/wp-content/p...375-TC-28V.pdf

Note that the current demand is only 3 amps (reasonable, given the higher supply voltage), but the recommended CB size is still 6 amps.

Lots of seeming inconsistencies in their docs.

Edit (was in a hurry this morning): The 28V product's circuit protection vs. demand is a lot more 'sensible' than the 14V product. Panel mounted circuit protection should be there to protect *the circuit* (the wires); not the device. A lot of mfgrs have started to spec circuit protection values to protect their device, instead of building the device protection *into* the device (much cheaper for them, and provides deniability if there's a failure). But.... Does anyone really want the potential for a nuisance trip on a flight critical component like the boost pump? Consider how you'd have felt if your 1st discovery of an issue was when the mech pump had just failed & the fuse (or breaker) popped when you hit the boost pump switch.

Charlie

[ron sterba]

Good points Charlie,
The good news is that Mr Owen Phillips ( President ) asked me to send it back. So today I sent it FEDEX to England. I saw the plane lift off here this afternoon for Portland Oregon, then to Memphis Tennessee processing center,then to England. To be delivered Thursday by 4:30 their time. I asked Owen if he could give me a time frame for the return. I appreciated his acknowledgement.

Question, Circuit breaker, If I install a circuit breaker on the left side of my panel just above my boost switch,( I have a hole there for one ) ,then I have 4 feet of 16AWG wire back to my fuse block on the right side of my panel,and my thinking this 4 feet of 16 AWG becomes a fuseable link. Since the 16 AWG wire is still hooked up on the fuse block pos 15, can I put in a 10 amp fuse at the fuse block and still use the the 6 amp circuit breaker at the switch??

Thanks Ron in Oregon
RV9A XIO 320

[swisseagle]

Hi Ron

Your "clicking sound" is something that I had too! Does it sould like this:
https://vimeo.com/160658922
It start with high RPM then slow down (it is programmed that way) but then is should run continously, but it does not and interrupt. This only when the line is closed, engine not running or engine in idle.

The pump is one of the first production batches, lay much to long on the shelf. Needed to replace it for first flight, send mine to Andair for a refurbishing/warranty/update to the latest status.

No result yet, it is on the way back to me. Still flying with my buddy's pump.

[rv7charlie]

Originally Posted by ron sterba

Good points Charlie,
The good news is that Mr Owen Phillips ( Pesident ) asked me to send it back. So today I sent it FEDEX to England. I saw the plane lift off here this afternoon for Portland Oregon, then to Memphis Tennessee processing center,then to England. To be delivered Thursday by 4:30 their time. I asked Owen if he could give me a time frame for the return. I appreciated his acknowledgement.

Question, Circuit breaker, If I install a circuit breaker on the left side of my panel just above my boost switch,( I have a hole there for one ) ,then I have 4 feet of 16AWG wire back to my fuse block on the right side of my panel,and my thinking this 4 feet of 16 AWG becomes a fuseable link. Since the 16 AWG wire is still hooked up on the fuse block pos 15, can I put in a 10 amp fuse at the fuse block and still use the the 6 amp circuit breaker at the switch??

Thanks Ron in Oregon
RV9A XIO 320

The only way that the 16awg wire would become a fuseable link is if there were no protection at the source. Amp ratings for wire are almost always given 1st for voltage drop (resistance), and then for insulation integrity. There are charts showing different amp capacities for the same conductor, depending on which insulation is used (and I'm talking about certified aircraft wire), and whether the wire is in a bundle or free air. 16awg can carry *much* more current than the charts suggest, before becoming a 'fuse' (melting the copper). There are charts (google it) showing that 16awg can be run up to 20 feet with a 10 amp continuous load at a 10% voltage drop. This is nowhere near the capacity of the wire before even insulation failure; it's just the limit for practical resistance losses in the circuit.

Why not just use the 10 amp fuse at the fuse panel, and call it done? The pump has an internal bypass to limit pressure, and based on the descriptions given here and the video just posted, it as some internal 'intelligence' that governs its speed based on pressure and demand. So, if the pump has a fault that would blow a 10 amp fuse, what good can come from resetting a CB repeatedly? Size the wire to handle max no-fault load, fuse to protect the wire, and done.

If it will help you get more comfortable with the idea, note that since there are electronics *in* the pump, there are failure modes that can let the smoke out *without tripping Andair's recommended protection*. It's just something we live with every day, in most, if not all electronic devices, even in airplanes. Let me rephrase that; things can burn inside the device; if Andair did their job right, you probably wouldn't actually see the smoke until you opened the pump. Anyway, the point is, that's why you hear the phrase, "The fuse protects the wire; not the device."

Charlie

[ron sterba]

Thanks Charlie, I learned a lot in your letter. Makes sense. I'm just rounding my edges here as a novice and found myself " don't do this and don't do that" ohh can't go over what the manufacturer says. Well My friend said lets hook up a meter in in amps and check the load that is being carried. Actually pretty easy. Knowledge, from reading your post and applying I better understand the bridge carrying capacity of wire out of the bundle. Did read about bundled wires but I think that would be maybe like a airliner with LONG runs of wire. Sorta like a workout gym with partcipants and having no fans to chill the heat and sweat generated. Thanks Charlie!

Now what I have learned is, Don't buy by your electric fuel boost pump unless you plan to use it in the next 6-9 months, or follow manufacturers recommendation for storage. I think that's safe to say. My engine is new from lycoming and it came with long time storage Several years back. Price went up $7500 since then. Now avionics well that's a different story. Changing all the time, I think the manufacturers got the hardware standardized. I bought a Dynon " low powered transponder just before the 2020 mandate, yep bought the new one and sold the other to a very happy builder who knew what he was getting.

Now on the Andair pump, sending it back to the factory was $117. It should be there as we speak. That's what FEDEX said, we'll see. I'll keep you all updated on the progress.

Ron in Oreon. RV 9A