Fuel Flow Gauge

[jwilkins]

1980 M20K s/n 25-0313.

The factory fuel flow gauge is inop. (analog type with the MP gauge)

The EDM-800 works fine. The shop AP/IA said this is a required factory gauge and should be fixed.

I searched for fuel flow trouble shooting but am a tad confused about the different factory systems.

Any suggestions on a logical approach to troubleshooting? The factory service manual is not helpfull.

Thanks,

Jim

[jetdriven]

I can't help much except many factory fuel flow guages are actually fuel pressure guages and instead of reading PSI it is calibrated in GPH.  When diagnosing a high FF indication, it is often a clogged injector and its reading higher PSI.  It indicates backwards.  If it has a transducer mounted inline, it is not like that.  Start there.

Anyways, our 201 has no fuel flow from factory and neither do most GA planes, and its not listed under the GRABCARD list found in FAR 91.205(d).  So why couldn't you placard it INOP under FAR 91.213?

[pjsny78]

this is pure speculation but unless your plane is equiped with a MEL everything has to work. i highly doubt any mooney has a MEL. this is what your mechanic may be referring to.

[jetdriven]

Not so.  An MEL is not required on a small nonturbine airplane not for hire. It may be deactivated and placarded INOP, or removed per FAR 91.213.

from:   http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgFar.nsf/FARSBySectLookup/91.213

----------------------

(d) Except for operations conducted in accordance with paragraph (a) or © of this section, a person may takeoff an aircraft in operations conducted under this part with inoperative instruments and equipment without an approved Minimum Equipment List provided--
(1) The flight operation is conducted in a--
[(i) Rotorcraft, nonturbine-powered airplane, glider, or lighter-than-air aircraft, powered parachute, or weight-shift-control aircraft, for which a master minimum equipment list has not been developed; or]
(ii) Small rotorcraft, nonturbine-powered small airplane, glider, or lighter-than-air aircraft for which a Master Minimum Equipment List has been developed; and
(2) The inoperative instruments and equipment are not--
(i) Part of the VFR-day type certification instruments and equipment prescribed in the applicable airworthiness regulations under which the aircraft was type certificated;
(ii) Indicated as required on the aircraft's equipment list, or on the Kinds of Operations Equipment List for the kind of flight operation being conducted;
(iii) Required by Sec. 91.205 or any other rule of this part for the specific kind of flight operation being conducted; or
(iv) Required to be operational by an airworthiness directive; and
(3) The inoperative instruments and equipment are--
(i) Removed from the aircraft, the cockpit control placarded, and the maintenance recorded in accordance with Sec. 43.9 of this chapter; or
(ii) Deactivated and placarded "Inoperative." If deactivation of the inoperative instrument or equipment involves maintenance, it must be accomplished and recorded in accordance with part 43 of this chapter; and

[pjsny78]

as always i learn something new from jetdriven.  thank you for that i was always under the impression everything had to work.

 thank you.

[jetdriven]

If that were so I would have to carry a scooter in the bag compartment to get home several times a year!

[Cruiser]

I was taught that those instruments required to monitor the settings/ranges defined in the POH Limitations section are required for flight and as such cannot be placarded.

[jwilkins]

From what I have read the early M20K's had a pressure transducer for fuel flow. Most of these were converted to the turbine type fuel flow indicators under a Mooney SB. Planes newer than mine had a digital totalizer as OE.

According to the s/n in the SB mine should have a turbine sender. The indicator is the analog combined MP / Fuel flow.

I do not have a MEL list for the plane. It used to be possible to get an MEL approved by your local FSDO. We looked into doing this for the flying club once and decided it was less work to keep all the instruments working.

The shop IA said the fuel flow is listed on the original installed equipment list. The JPI is not an approved replacement. 

The only trouble shooting hint I've seen is to take the turbine out of the fuel line and make sure it is moving freely. I was hoping there was a trouble shooting process such as checking the turbine output with a VOM or scope before we start disconnecting fuel lines. If there aren't, I'll ask them to pull the transducer the next time we have the cowl off.

Thanks, Jim

 

[201er]

I had a fuel pressure gauge go inop on me. I was told different stories from it being a must to being entirely non-essential. I did my own research and determined that:

A) It is required to be installed and operative fromt the factory as stated on the type certificate

It is not required for VFR or IFR Part 91 flight

C) It can be placarded inop indefinitely

D) It's a good idea to fix at the next scheduled maintenance which I did (turned out to be nothing more than a bad contact)

[jwilkins]

Mike,

Thanks.

Where was your bad contact? How did you find it?

I have a placard for the meter, and thanks for the rundown on legalities. I did check the FAA M20 type certificate and did not find a fuel flow meter listed.

Jim

 

 

 

[201er]

I'm not sure where the bad contact was cause it was mechanic that handled it. But it had to be either at the gauge or the transducer. Now this is a fuel pressure gauge I'm talking about. But I suspect it should be the same case for fuel flow. Mine doesn't even have a factory fuel flow, just the digital one I added. This is why if you're comfortable with it, I don't see a reason you can't wait till next annual or maintenance to have it taken care of.

I didn't placard mine because I was "diagnosing it" to see if it would come back on. Mine was actually reading maximum psi rather than not reading anything. So I left it open to see if it shakes itself back. No luck. Flew like that for 2 months until I got it fixed at an oil change.