The International Cessna^® 170 Association

I have a "stick" I picked up somewhere and marked it with a ball point pen as George suggested( I have had this for 10 + yrs). It seems to work quite well although I rarely use it. I may be "cruising for a brusing" , but I have found my fuel indicators to be pretty darn accurate. I have one of those early model 172's as many of you know and since it has a tailwheel conversion I don't think the tanks will hold as much fuel as they normally (for a 172) would in the trike position. I have filled my left (port to you sailor types) on two occasions from the same pump after pulling the sump valve out to make sure the tank was empty and on what I preceived as level ground (no spirit level used). Both times (fuel selector in "off" position, I got 19.6 gallons each time. Sometime I would like to try again at a different pump and use a level to make sure everything is so-so. Doubt it would make much difference. By the way the first time I did the fill up thing I flew (over the airport) until the engine sputtered, then kept wagging the wing up until the engine would not catch any more and I used about all of the fuel. I wouldn't want to have to do that in order to get to a runway or safe landing area, but I believe you can coax almost all of the 19.6 (in my case) gallons into usable fuel---of course not in an assending or desending attitude. I would be curious if anyone else has checked their 170's for how much fuel the tank (s) would hold if they were totally empty?

A war story of sorts----------I used to almost always fly on one tank until it ran dry, then switch to the other one so I would know I still had most of a full tank of fuel left. I will still fly until the needle on the indicator won't move with the waggle of the wing if I am on a long trip & have good altitude + acceptable landing areas nearby. Once while taking a friend for a prolonged flight we were flying pretty darn low over an area lake when the engine sputtered! Guess what----the fuel in the right tank was gone and I had just made a turn to the right. That cured me from doing that even though a quick change to the full tank quickly allowed the engine to restart, but it was a dumb thing to do. As they say "Never Again"

I like to fill up with the fuel selector on the left or right tank to minimize the possibility of forgetting to move the selector from the off position. The only time I select off is when maintenance requires it.

George can chime in here about leaving the selector on in the hangar. He could have a point there.

Dave Clark wrote:I like to fill up with the fuel selector on the left or right tank to minimize the possibility of forgetting to move the selector from the off position. The only time I select off is when maintenance requires it.

My personal experience is that there is not enough fuel ahead of the valve to get the airplane off the ground with the selector in the OFF position. The couple of times I've left it off after maintenance, I've only been able to taxi a couple hundred feet before the engine begins to stumble. (If you're quick, you can recognize the problem and get the fuel selector switched before it quits. )

'98C has never sat quite wings level on the ground, so I've developed the habit of switching from BOTH to one tank or the other as I'm taxiing in after landing to prevent crossfeeding into the low tank. This also prevents crossfeed during refueling, which helps to maximize the amount of fuel on board. I've also developed the habit of putting the selector in BOTH before starting the engine, then checking it as soon as I start to taxi, and check it again as one of the last items before takeoff.

Miles

All the fuel between the carb and the fuel valve is below the carb, so all you have to burn is whats left carb bowl.

lowNslow wrote:All the fuel between the carb and the fuel valve is below the carb, so all you have to burn is whats left carb bowl.

You can't even burn all of that, since as the level drops in the bowl, the mixture leans and the engine quits.

Miles

I use my finger. If the fuel doesn't come up to the second knuckle I call the fuel truck.



tye

n3437d wrote:...He decied to "fly-off" most of the remaining fuel by doing Touch and Goes in the pattern. It seems that on the last T/O the engine sputtered, caught, sputtered and then quit with no reserve alt. to do a 180. The owner escaped injury but now has more problems than just the quirky fuel guages.

If this idiot bought the farm, the collective IQ of this country would have gone up a whopping 10 points. I don't think I've flown a plane that didn't have some sort of limitation about taking off with low fuel be it quarter tank, 10 gals, 500 lbs/side. I guess he thought "touch and goes" weren't takeoffs. Sheesh.

Notice that the 1/4 tank "no take off" placard on our fuel gauges is not an actual aircraft limitation. The limitations are listed in the type certificate, and in the AFM,...and no mention is made of the "not take off range" of our fuel gauges. (Therefore, it seems to be merely good operating practice.)
BTW, FAR 91.151 specifies a 30 minute reserve of fuel for day, VFR operations. Beginning a flight, for the purposes of operating until the aircraft "flames out" of fuel (even as a test) is technically a violation.

gahorn wrote:Notice that the 1/4 tank "no take off" placard on our fuel gauges is not an actual aircraft limitation. The limitations are listed in the type certificate, and in the AFM,...and no mention is made of the "not take off range" of our fuel gauges. (Therefore, it seems to be merely good operating practice.)
BTW, FAR 91.151 specifies a 30 minute reserve of fuel for day, VFR operations. Beginning a flight, for the purposes of operating until the aircraft "flames out" of fuel (even as a test) is technically a violation.

This may be a conservative interpretation of CAR-3 (under which the 170 is certified) section "Instrument Markings" which state:

§ 3.761 Fuel quantity indicator. When the
unusable fuel supply for any tank exceeds 1
gallon or 5 percent of the tank capacity,
whichever is greater, a red band shall be placed
on the indicator extending from the calibrated
zero reading (see § 3.437) to the lowest reading
obtainable in the level flight attitude, and a
suitable notation in the Airplane Flight Manual
shall be provided to indicate the flight personnel
that the fuel remaining in the tank when the
quantity indicator reaches zero cannot be used
safely in flight.

Remember that the placards mentioned in the 170 type cert. are only those particular to the 170, there are general markings and placards required for ALL aircraft certified under CAR-3.
I noticed that all engine instruments are required to have green arcs and red radials, my Scott oil temp is not legal so I guess I'll have to get out the magic marker.

As a matter of discussion, regarding CAR 3,... the AFM does not contain such notation. The only mention made in the AFM regarding fuel quantity indicators is under "Instrument Limitations" in which it is noted that: "Approximately 2 1/2 gallons of fuel unuseable in normal flight manuevers remains in each tank when the gauge registers empty."

I guess that must be an attempt to meet the "suitable notation in the Airplane Flight Manual"... ." to indicate the flight personnel that the fuel remaining in the tank when the quantity indicator reaches zero cannot be used safely in flight."
That wording has never been found on any fuel gauge in any 170 that I know of.
Of course the "greater" of 1 gallon or 5% of capacity is about 1 gallon in our airplanes, and the lowest reading obtainable in flight IS at the empty mark.
I guess we're all illegal.

gahorn wrote: Of course the "greater" of 1 gallon or 5% of capacity is about 1 gallon in our airplanes, and the lowest reading obtainable in flight IS at the empty mark.
I guess we're all illegal.

Like I said, a CONSERVATIVE interpretation.

I had an old Universal Fuel Hawk laying around and calibrated it to my hangar neighbor's early 172 stick (as has been previously mentioned.) Come to find out, the Universal stick markings are exactly 1/2 of the 172 values. So I can just double the number read to find the useable fuel qty. No cutting, polishing or calibrating required!

My two cents on this subject: I use two paint stirrer sticks to measure fuel amount. Fill the tanks, shove in a stick and pull it back out. Before the fuel evaporates, mark the top of the fuel level on the stick with a pencil. Repeat for a second stick. You'll need two, as it takes a few minutes for the fuel to evaporate from the first stick while you are checking the other tank. I have checked the levels against the fuel gauges (as they appear in level flight just before landing) and it is cerainly accurate within 1/8th of a tank, which is good enough for me. My watch and knowledge of typical fuel burn rates (easily calculated from your next fuel purchase receipt) is the only safe means to prevent fuel exhaustion in planes with float type gauges. A word also on fuel totalizers that seem to be popular these days. They sure are accurate, but only if used correctly. A local USAF Reserve F-16 pilot jumped into his brand new RV-4 here a while back, reset the totalizer incorrectly, then managed to get just high enough to kill himself and his nephew when the engine quit. I'm going to stick to my paint stirrer.
On water in fuel tanks - my otherwise pristine 1966 C-150 had very leaky fuel filler necks until I replaced them. After a heavy rainstorm (plane was tied down outside), I checked the fuel. The contents of the cup was wonderfully clean with a sight tint of blue. However - it was pure water. I drained about 20 cup fulls before the fuel appeared. Thus make sure you do the triple test when draining - sight, smell and touch (fuel feels cooler as it evaporates quicker).

Another method to calibrate such a stick is: Empty a tank, then put in 5 gallons and dip it, mark the stick. Put in another 5 gallon,...etc. etc. ... 'til full.
Also.... if you pour a quart of water into your fuel tank..... it will take about 30 minutes and draining of almost a quart of fuel....before you even see a trace of water at the gascolator..... and EVEN THEN...only if you've somehow LEVELLED the airplane!!! (The 170 fuel tanks drain fuel from the center of the tank...not the rear, where the wing sumps are located.) The wing sumps may not show water for several minutes, and the gascolator will not show water until the airplane is levelled sufficiently to allow the water to find the fuel line leading to the gascolator.

gahorn,

I took your advice picked up the Fuel Hawk stick, wacked off the bottom two indicators and tested it on a flight to Pal Springs this weekend. The modified Fuel Hawk stick is a very accurate indicator of useable fuel.

Great tip!

Thanks