Fuel flow

[N4027v]

WOW! Thanks Dan; will try the flow test today and check/install cotter pin in lever.

I believe, of all the investment into my 170, joining this organization has been the best decision made. The information on the forum is priceless and the quick response of members with such detailed suggestions and solutions is like having my hanger full of 170 experts ready to help with any problem!

I hope to have my license by July so I can meet my new friends at convention, if not, see ya in Gulf Shores next year!

Pic of yesterdays destination on first x-country with instructor. Claims to be the starting location for Delta airlines. Tullulah Scott field (M80).

[N4027v]

M80 Scott Field

[DWood]

check/install cotter pin in lever

The cotter pin in the lever will assure that the valve is in the proper position. It should only go in with the lever and valve in the proper orientation. Otherwise you could be on left when you think you are on both (as an example).

Please let us know what you find.

Dan

[GAHorn]

Sometimes what will occur in the Both position ... is that fuel will appear to flow from one tank much faster than the other.... when in-fact what occurs is...one tank has developed a fuel-flow to the engine while simultaneously siphoning fuel across the vent-line from the opposite tank. This gives the appearance of one tank supplying ALL the fuel, when in-fact the tank remaining fullest is actually supplying the fuel but being re-plenished from the opposite tank via siphon action across the vent line.

The early "weatherhead" and "imperial" and "kohler" valve did not have check valves. This allows the two tanks to "level out" their fuel contents when in either "off" or "both" positions,... although while in the "off" position no fuel goes to the engine.

[N4027v]

We did a few tests today on fuel flow. Timed the flow at Gascolator in left, right, and both and then repeated the test with the fuel caps off. Right and left were within one second of each other to catch one liter with caps on and off. Both position was faster by two seconds. Off position - no flow at Gascolator. I believe the test proves no restriction and maybe no problem just unequal flow in flight?

I checked the selector lever and found there is not a hole for cotter pin but appears to have a set screw on one side.

[N4027v]

No cotter pin hole

[DWood]

Will the lever come off? I have only seen cotter pins.

When at safe altitude and over airport, we switched to right only tank but continued to draw from left tank and maybe some from right but clearly used more from left.

I think you still need to visually assure that the valve or plumbing hasn't been changed.

It sounds like the fuel valve positions are correct but not sure if the right is draining or if it is all coming from the left tank. The only way to be sure the right tank is draining would be to run enough out of the right thru the valve and gascolator. You could use a paint stick (vertical in the tank) to mark the fuel height in the right tank, drain 5 gallons thru the gascolator into a fuel can, then restick and remark it. The difference will tell if the right is draining. I will be able to tell you if the difference in measurements is close to 5 gallons based on my "calibrated" fuel stick.

PS: Also stick the left tank before and after to make sure no fuel is coming from that tank with the valve in right position.

I am also assuming that your fuel gauges are working correctly.

Dan

[KAP54]

have to agree with Dan my 48 sn 18619-valve on firewall, has off-left-both-right, Normally fly on both and left GAUGE goes down faster than right , but since left holds 12.5 gal and right holds 25, seems that the flow from each would be about equal.

Keith

[GAHorn]

Dan, the fuel valve lever is ordinarily secured using a "roll" pin. Sometimes owners have substituted a cotter for the roll pin.
(PS: Roll pins should also be secured with safety wire, according to some literature.)

[DWood]

George:

I did not know that and it would certainly look cleaner (without the safety wire).

However, the IPC 38-23 pages 72 and 73 does call for an AN380-2-3 cotter pin for the shaft and handle (I wish I knew how to paste from a PDF to the forum as I did take a snapshot)

The later 48 does call for a different handle IPC figure 39 and I do not find a cotter pin called out. Both of my 48's have the older handle with cotter pins.

Thx,
Dan

[GAHorn]

Item 36 is indeed identified as a cotter, however that item is located at the BOTTOM of the shaft. (I admit that there is also a cotter illustrated, but not identified, as a cotter at the handle, however... modern assemblies do not use a cotter, they use a roll pin. At one time, it was suggested in an FAA advisory that a length of safety wire be threaded thru the hole in the roll pin and then looped beneath the handle and twisted to secure it. That way the roll pin cannot drift out and the wire will not snag your fingers like a cotter will.)

[DWood]

Item 36 is indeed identified as a cotter, however that item is located at the BOTTOM of the shaft.

The description for the cotter pin in the IPC says "(Attach Handle and Shaft Assembly)" and the quantity is 2

[GAHorn]

That might be a revision issue. My Sept 1, 1956 electronic version does not state that and indicates only one cotter. (I'd post a copy but I haven't yet figured out how to do that in this &^%#^%# Windows 8 new laptop.)

In any case, we've all learned the IPC is not an approved doc and has many errors (tho' I'm not suggesting that in this case.) The IPCs should not be used for assembly-guidance except as a last-resource, especially as regards this fuel valve.

[DWood]

The revision I am referencing has an 11-58 date on the revision page.

Early 48 Fuel Valve.pdf

If there is a revision out there that has different information, I would really appreciate seeing it. Perhaps you can you post it in the Mx section.

Also if there is any other data that you are aware of with these details, that would also be appreciated.

Thx,
Dan

[GAHorn]

Dan, that page is a revision page, not the published date of the IPC.
In any case, I wouldn't be worried about whether or not it was a roll pin or a cotter. Either would work. I was just wishing to mention the use of safety wire when a roll pin is found or used.
Also, re-reading this thread I see why this mention has become the focus. It is because of my prior post in which I failed to also mention that some valves have the lever secured with a screw rather than either pin or cotter. There clearly are differences in the field. (Perhaps due to change of sources for parts.)