Question for 180hp 170 owners or folks familiar w/AVCON conv

[Bruce Fenstermacher]

I'm having a off forum exchange with a fellow with a latter '67 172 and he has the AVCON conversion. Like many of us he has incomplete paperwork for the STC's installation which is STC #777CE and of course the Williams aren't to be found.

He's trying to find out if his installation has or is suppose to have an electric fuel pump and if the STC paperwork specifically forbids the use of 91 Octane MOGAS.

So my first question is does anyone know anything about this STC.

That got me to wondering about the AVCON STC for the 170. Does it require an electric fuel pump or specifically restrict the use of 91 Octane MOGAS.

This thread is not about whether a electric fuel pump is actually needed or whether it is smart to burn any kind of MOGAS. Just curious what if anything the paperworks actually says. From what I've seen it does not require a electric fuel pump in the install instructions and I didn't see any restriction to the use of any MOGAS let alone 91 Octane MOGAS but I might have missed something.

[Roesbery]

Don't have the paperwork in front of me, but, the stc requires the electric fuel pump ( in addition to the engine driven pump ) and it is to be turned on for takeoff and landing. Probbly one of those cya required by the FAA. In actual practice the engine functions fine without any pump.
The engine requires a minium of 90 octane per Lycoming, don't recall anything in the stc about it.

[cmsusllc]

I also don't have my paperwork in front of me ( too damn cold and slick outside ) but if my memory is right 92 octane is the minimum and the electric fuel pump is required in case of a failure of the engine driven pump as gravity feed is not enough. I also found specific written info in the paperwork somewhere that the electric pump is NOT to be used except to assist after a failure of the engine driven pump. I use to think you were suppose to use the electric pump on takeoff but an A&P showed me in the paperwork where that is incorrect. Also there is a tag on the engine requiring a minimum of 92 octane. ( o-360 A1A. ) Scott.....53B

[c170b53]

I think that during the pre-start process a check of fuel pump px is done (selecting electric pump on then off) then its only turned on if all else fails. So not only do you need a electric pump, the mechanical pump but you also need a 0-5 psi fuel gauge.

[tweiss]

Bruce,
I have copies of a couple Avcon STC's for the 170A & B:
SA806CE
SA749CE
Both mention fuel as "91/96min. grade aviation gasoline." and nothing more in the entire 4 page STC.
The SA806CE only talks about the electric fuel pump in regards to where the switch placard is to be mounted on the panel.
The SA749CE states under procedures:
Note: Turn Auxiliary fuel pump on in the event of an engine-driven fuel pump failure. and nothing more.

Curious post and responses. I've been turning the pump on every t/o and landing for almost 30yrs. I was told that somebody (probably Cessna or the FAA) feared that with the extra power, the nose could be raised high enough to overcome the gravity feed. I don't know.
But now that the question has been asked, and I can't find it in writing, I'll have to keep looking. Maybe it's in the drawings, but I don't have them handy right now.
I'll post further if I come up with something.
Tom

[Jr.CubBuilder]

The AvCon converted C172 with an O360 Lyc failed the Peterson vapor lock test with mogas, that can be verified on his website. This setup is the same as the C170 conversion. The conversion should have an electric fuel pump for redundancy as part of the STC, and that was a requirement due to the size of fuel line from the gascolator to the carb.

[Bruce Fenstermacher]

Thanks for the responses you've confirmed what I already figured.

Can't speak for the 170 with regard to the AVCON conversion and this is a completely different animal but the Cherokee 140 has an electric as well as engine driven fuel pump. The electric pump was to be used for take off and landing. On landing only in case of a bulked landing and consequent departure.

[blueldr]

One must be cognizant of the fact that cherokee is unable to gravity fuel feed under any circumstance.

[flyguy]

One must be cognizant of the fact that cherokee is unable to gravity fuel feed under any circumstance.

JES WUNDER IFA CHEROKE CIN OVERCUM GRAVETY EENY TYME?

[Blue4]

I check mine during preflight operations, but seldom use it for takeoff/landing.

A seasoned bush flyer here in town recommended that I use it during very critical takeoffs (i.e., short field / off airport).

The engine-driven pump works great (knock on wood) which of course is verified by the fuel pressure. Honestly, I think the electric pump is a back up to the back up.

-S

[DaveF]

My Avcon SA806CE STC calls out 91/96 but doesn't prohibit autogas. It does specify an electric fuel pump.

The O-360-A series engine TCDS E-286 specified 100LL, and Lycoming service instruction SI1070P says that 91/96 is acceptable.

[GAHorn]

This probably doesn't need saying but... unless a particular fuel is "specified" as approved...then it's not approved. (Meaning of course that just because autofuel isn't specifically prohibited, ...does not authorize/approve it.)

[marathonrunner]

I spoke with Bob Williams about the fuel pump and he told me that when they tested the aircraft in a climb, it was an extremely hot day and it somehow failed the test. That is why his STC has the fuel pump. I believe there are others that do not and I will look at my paperwork but I believe it states that the fuel pump is to be used for take off and landing. I have had my engine driven pump fail and it worked fine with gravity flow BUT, not all fuel pumps allow for gravity feed to flow through. Do not depend on that and do at least make sure your electric pump is working as a back up.

[canav8]

Bruce,
I have copies of a couple Avcon STC's for the 170A & B:
SA806CE
SA749CE
Both mention fuel as "91/96min. grade aviation gasoline." and nothing more in the entire 4 page STC.
The SA806CE only talks about the electric fuel pump in regards to where the switch placard is to be mounted on the panel.
The SA749CE states under procedures:
Note: Turn Auxiliary fuel pump on in the event of an engine-driven fuel pump failure. and nothing more.

Curious post and responses. I've been turning the pump on every t/o and landing for almost 30yrs. I was told that somebody (probably Cessna or the FAA) feared that with the extra power, the nose could be raised high enough to overcome the gravity feed. I don't know.
But now that the question has been asked, and I can't find it in writing, I'll have to keep looking. Maybe it's in the drawings, but I don't have them handy right now.
I'll post further if I come up with something.
Tom

Tom, the Cessna 175 has a placard that says that fuel pump must be on for full power t/o's.Gravity feed may not be sufficient for full power operation FYI. All low wings have that procedure as well. Call it simple insurance policy. D