Fuel Pressure Gauge PA-28R - required?

[killbilly]

This is driving me nuts.

I've got a fuel pressure gauge which vibrates/fluctuates consistently to either end of the range, and the frequency increases with RPM. Fuel boost pump doesn't change the frequency.

I've got a checkride scheduled in this airplane and I'm going nuts trying to figure out if it's required.

There is no MEL for the airplane, and 91.213 indicates that if it's required by the type certificate, then it has to be operative, or at least determined to be safe with proper deactivation and placarding by a mech if it's not required by the sheet.

The POH doesn't contain a Type Sheet. The Limitations section of the POH lists all of the equipment, but a) the fuel pressure gauge isn't listed, and b) nothing in that section lists required vs. optional.

Google is failing me.

The engine is running perfectly fine. I am concerned that the DPE is going to look at this and say, "that's broken, and this airplane isn't airworthy."

He might also shrug and say, "eh - you have fuel flow on the other gauge, so you're okay."

Neither mech I spoke to this morning knows the answer off the top of their heads.

Thoughts?

 

[trafficinsight]

This is driving me nuts.

I've got a fuel pressure gauge which vibrates/fluctuates consistently to either end of the range, and the frequency increases with RPM. Fuel boost pump doesn't change the frequency.

I've got a checkride scheduled in this airplane and I'm going nuts trying to figure out if it's required.

There is no MEL for the airplane, and 91.213 indicates that if it's required by the type certificate, then it has to be operative, or at least determined to be safe with proper deactivation and placarding by a mech if it's not required by the sheet.

The POH doesn't contain a Type Sheet. The Limitations section of the POH lists all of the equipment, but a) the fuel pressure gauge isn't listed, and b) nothing in that section lists required vs. optional.

Google is failing me.

The engine is running perfectly fine. I am concerned that the DPE is going to look at this and say, "that's broken, and this airplane isn't airworthy."

He might also shrug and say, "eh - you have fuel flow on the other gauge, so you're okay."

Neither mech I spoke to this morning knows the answer off the top of their heads.

Thoughts?

1.) AFM - not listed
2.) TCDS - not listed
3.) AD's - none
4.) 91.205 - not listed
5.) Any other regulation - here's where it gets fun!

14 CFR part 23.1305(b)(4)(i) says for each pump fed engine... a means to continuously show fuel pressure or fuel flow.

But unfortunately your Cherokee was most likely certified under CAR 3, which simply stated a fuel pressure gauge for any pump fed engine was required.

Unfortunately in my opinion the fuel pressure gauge is required by the regulations the airplane was certified under.

Now, there may be a loophole as manufacturers often certified later models under CAR 3 as amendments to the original type certificate but used sections of part 23 as equivalent means of compliance, and the TCDS lists the certification basis for each model.

I would need to know the model number and possibly serial number to determine that.

I know this isn't the answer you're looking for, the Piper pressure gauges are notoriously unreliable

If it helps, the first thing I would check on your gauge is the fittings on the lines, one should have a metered orifice in it which would serve to dampen the pump pulses, which is what youre seeing... it's very common for some well meaning mechanic to discard that special fitting during an engine overhaul.

Sent from my XT1254 using Tapatalk

 

[Roger Roger]

If it helps, the first thing I would check on your gauge is the fittings on the lines, one should have a metered orifice in it which would serve to dampen the pump pulses, which is what youre seeing... it's very common for some well meaning mechanic to discard that special fitting during an engine overhaul.

Sent from my XT1254 using Tapatalk

Ding ding ding.

 

[uncreative]

Here's my anecdote- l took my commercial checkride in an Arrow with the same issue. DPE made an issue of the laminated Airworthiness cert but didn't bat an eye at the fuel pressure gauge.

 

[drunkenbeagle]

If it helps, the first thing I would check on your gauge is the fittings on the lines, one should have a metered orifice in it which would serve to dampen the pump pulses, which is what youre seeing... it's very common for some well meaning mechanic to discard that special fitting during an engine overhaul.

Most Cherokees I have flown do exactly the same thing. The fact that it is moving indicates there is fuel pressure. Come to think of it, I can't remember a Cherokee not doing that on the fuel flow gauge.

 

[trafficinsight]

Most Cherokees I have flown do exactly the same thing. The fact that it is moving indicates there is fuel pressure. Come to think of it, I can't remember a Cherokee not doing that on the fuel flow gauge.

Small pulses are common, large pulses are an indicator of a problem.