Switching fuel tanks in route?

[AR Dave]

I think I'll get the paint mixer sticks out for awhile then. Been about 4yrs since I used my stick, can't remember if soaking the wood on the first dip caused difficulties finding the wet mark on the second dip.

Anyway Eric you made me think of another quick question - during climb. For some reason I was taught to cruise at 2350 rpm, which I did for years. Great gas mileage. George got me up to 2450 before flying to America. On take off, I'm full power, but after clearing the trees, my instinct wants me to cut the rpm's back, fearing I'm being too hard on the engine. What max rpm should we climb at and for how long? Now that I'm a jet setter, sometimes I'll look down and see that I've been cruising at 2550, I start worrying that I've hurt the engine. Could one stay at full throttle, max climb angle, all the way to say 8000 ft.?
What was the subject of this chat? Oh yes, then switch fuel tanks -
Dave

[N1478D]

For me, almost always the throttle is set to full during climbs at any altitude, unless flying in formation. The extra fuel helps to cool the cylinders and the engine is not laboring, like going too slow in third gear in your truck. I cruise at 2450 too, feeling that higher RPM's are introducing more heat, friction, and more wear.

[GAHorn]

Guess what maximum rated power is with this engine? Answer: 2700 rpm/145 hp.
Guess what maximum continuous power is with this engine? Answer: 2700 rpm/145 hp.
You are not hurting this engine by using full throttle for takeoff and climb. In fact, you'd be following the operation recommendations by the mfr.
I use full throttle for takeoff, climb to cruising altitude, and also for cruising rpm if the performance charts show the altitude performance to equal 65% or less. (But there's no harm in running it at 75% or greater power, according to the mfr.)
Above 3,000 ASL I lean "gently/slightly" for the remainder of the climb. (Above 3K full throttle climb yields about 2300-2400 rpm which is less than 65% power, a setting that cannot hurt the engine despite leaning.) I lean aggressively at cruise. (I cruise at 2450 rpm and use the Owner's Manual leaning technique: Lean for max rpm, then continue to lean until first sign of rpm loss, then enrichen back to max rpm.) I leave it leaned during descent, approach and landing and taxi in. I would use full rich in case of go-around.

The paint sticks are an excellent tool, available free from paint stores/WalMart. I also found that a "Fuel Hawk" brand, clear dipstick tube (as sold by Spruce) works perfectly on the A and B models. Purchase the C-172 model for 19 gallon tanks. Notice that the calibrations include 2 hash-marks below "0". Use a tubing cutter to cut it off at the "0". Use a wire wheel or file to remove the sharp edge and bevell it as it was prior to cutting.
The correct method to use the re-calibrated Fuel Hawk, is to place it at the rear of the fuel filler opening, keeping it vertical, and placing the bottom of the tube against the interior "baffle" found just below the fuel filler. This gives you a consistently accurate placement of the tube.
I've deliberately run one tank dry and landed on the opposite tank. I've repeated this on each side. It is exactly accurate.
(I shouldn't share this info. I should just make the things and sell them to all my buddies.)
(Please, Let's not let this deteriorate into a discussion of "what if I've got 180 gear legs?" or "what if my tires are 8:00 X 6:00?" etc. You can figure it out yourself. My airplane is a stock B-model.)

Edited Fuel Hawk 21 to 19 gal

[Dave Clark]

At the risk of opening this up to a debate on if there is such a thing as a "step" I noticed with the C-145 on my plane that 2450 would seem laborous with the plane sitting a little tail low, whereas 2500 would feel much much better. The airplane would be flying.

It gets even better at the higher speeds the Lycoming provides. It will cruise along at 7500ft and not be affected as much by lifts and sink. Or at least you don't notice it as much. Much more stable.

[N1478D]

Mine seems slightly laborious at 2350, and at 2250 the engine seems to be trying to say "speed it up, I'm outta balance". 2450 really seems to be where everything is really working well. Of course, if I need to get in the passing lane, 2600 or higher is there waiting.

[Romeo Tango]

I've had my C170 for 3 weeks now, and the first experiment was to get both tanks emptied and calibrated on a pipette so I have precise fuel burn rates to go from. I found that with the fuel selector in the 'right' position the left tank will happily empty out during flight, presumably into the right tank through some siphoning action.

To make sure it was not something goofy in the selector switch I drained the right tank completely at the gascolator with the selector on right, and then confirmed that with the selector back to both or left I again got a fuel flow.

As an original C170 there is a single vent/pressure vent, shared by both sides. I need to check continuity/blockage. The caps are unvented (and destined to be replaced soon since the gaskets are showing age.

[AR Dave]

Wow! I don't think my engine can turn over 2700 rpm. So if that is true, then techniquely I could fly full throttle all the time? Look out Joe, that might put me in the 100 mile-n-hour club! My plane has never talked to me at 2200 or 2700 rpm's, maybe I ought to read the directions on this plane sometime? I'll be recording some data when I get home.
I've been leaning all the tiime since I had the little fouling problem. But when I'm on downwind I put it back to full rich. Sometime's I get a little too slow on landings, I'd hate to floor it only to have the engine quit. It'd be hard enough for me to remember the Carb Heat on a go-around. George I'll have to try flying above 3000 again, it's just so hard to see deer and such from up there.
I really appreciate the mentoring on what I know is basic for some of you. Thanks!

[flyguy]

I have run out 3 Connies in the 30 plus years of flying our old '93D and having run them around 2600-2650 (I have seen 2700 rpm a few times when trying to beat the dark at our "daylite hours" home strip) I can attest that the higher rpms are able to produce pretty good "time to fuel burn" ratio. Indicated airspeeds at 2650 with that "Cal Twist" prop produced 135mph at 6500' and burns around 10gph. I have never had a cracked cylinder or stuck a valve. Knock On Wood!

The first (OEM) engine ran to 2000 hrs without a TOH. It was running ok but I had a chance to get another engine from a wind-damaged plane.

This second engine, from another '52 C170, had been majored in a shop in Kansas City and had 275 hours on the MOH. I ran it another 1600 hrs. (*This is the one that swallowed the valve! It had had a steady diet of 100LL and even though I am an agressive "leaner", it had considerable "lead" deposits on the back of the remaining 5 valves and lots of corrosion pits underneath that stuff.). It had been very reliable* before changing it out for another C145.

Engine #3. A friend found a Swift stored in the proverbial "Barn" and had an IO360 conversion set up for it so I got dibbs on the "LOW TIME" engine. Of the three Continentals I have used on '93D, this one has been the one that I have had headaches with. It was "pickled", with less than 200 hours, when they stored the Swift in the barn but it must have been broken in wrong or something. It has some of the strangest habits I have ever seen. Immediately after an oil change (8 quarts) it might run six hours without any noticable oil consumption then it may use two quarts the next hour! I am serious! This thing has "goosed" me more than once before I developed a permanent distrust of its habits! I began to carry at least 6 quarts of oil in the baggage compartment and paid much closer attention to the dipstick than the fuel quantity in planning trip legs.

I have sorta parked Ole Delta the last few years (too many other planes and projects) but plan to do a top overhaul with less than1400 hours on the OEM (from Swift) before going "flat-out!

IMHO 2600 - 2700 won't hurt the O-300 as much as doggin it!

[GAHorn]

I've heard several stories wherin the teller thought the C-145/O-300 just wasn't enough power for a 170. And I'm not sayin' that I'm any different than many pilots who think bigger is better. (Boat anchors, bilge pumps, engines, women's upper garments, etc....bigger is usually better.)
The C145/O300 is a very reliable old design that enjoys an excellent reliability reputaion (at least it did until folks tried to perform "new bearings and paint" overhauls, and scrimp on cylinders, pistons, cams, lifters, mags, carbs, etc.). If properly put together and given even a modicum of care, this engine will take a beating and still get you there in the dark.
But in order to really evaluate it's performance you've got to keep a couple things in mind:
Is the tachometer accurate? Many times a pilot thinks his Continental is worn out or sick when in reality he's just not running it at rated rpm. I've looked at a half dozen such complaints and the owner was amazed when we found out the tach was 100-200 rpm off on the low side, or their prop was different than that specified (and in one case was six inches too short in diameter!) There's just no way the airplane will perform well unless the engine/prop is correct and turning the specified rpm.
Sometimes the pilot forgets to take into account "parallax" when reading the tach. I've found that if I set the rpm to 2500, by the time I lean over at look at the tach from directly in front of it, I'm actually only turning 2450.
Remember that this engine only puts out 145 hp at 2700 rpm. So if you're experiencing 2250 indicated (with an accurate tach) on takeoff, you're actually only getting about 120 hp. Look at the TCM power charts and this can be easily seen.
So don't be afraid to turn up the rpm in cruise with this engine. This engine was designed to be run hard and it won't hurt it, and it'll certainly make your 170 perform again according to the book. Running this engine at slower rpms in the belief that it will make the engine last is false economy. 2350 rpm for 1800 hours vs. 2450 rpm for 1800 hours is 10,800 miles less distance travelled over the life of the engine.

[Dave Clark]

"2350 rpm for 1800 hours vs. 2450 rpm for 1800 hours is 10,800 miles less distance travelled over the life of the engine."

Of course if you put a stopwatch to the Tach Time's one hour the 2400 "hour" will be shorter due to the tach calibration at 2350rpms if memory serves.

Another point and I know it's a little apples/oranges but the geared version turns much higher although it needed a cylinder beefup. However, I think all new aftermarket cylinders and maybe the new TCM ones are all the same ie, they are all beefed up and approved for all models.

[GAHorn]

Yes, the GO-300 series used the same cylinder as the later C145/O300 cylinders. The early cylinders were not approved for the GO-300. (In other words, GO-300 cyls could be used in C145/O300's, but not the reverse. So mfr's simplified things and started making only the later cyl style. The difference was in cyl barrel-to-head attachment in the threaded area. A visual check may be made which may at first seem reversed. The later cylinder appears to have a gap between the head and the cylinder cooling fins. The early cylinders appear to have more material between the cyl. cooling fins and the head cooling fins which might lead one to think it is the beefier cylinder. Not so.) Modern, newly-manufactured cylinders fit both engines, so I'm not sure how this side-discussion relates to the original topic, except perhaps as a point of interest.
The GO-300 engine is not approved for use in a 170*, and considering that geared engines were not especially popular in light planes, and that subsequently the GO-300 engine has fallen into virtual obsolescence due to lack of parts (no thrust bearings) I can't imagine anyone ever considering an airplane with that engine except with an engine-change in mind. The GO-300 should be considered a throw-away engine once run-out, in my view.

*-Imagine if you will someone going to the trouble/expense to STC that engine in a 170. The result would be: less time between overhauls, loss of the 170's excellent visibility over the nose (due to the required higher cowl profile to cover the reduction gearbox), even more noise, insufficient fuel capacity, a reduction of engine reliability, probable loss of utility category, and no practical increase in cruise speed. Meanwhile no one can overhaul it for lack of parts, and even if they did, it couldn't be done by an ordinary A&P without Inspection Authority. Boy, this really has gone off-topic.

[AR Dave]

Off topic, but a really good discussion...

[flyguy]

YER RTIE ARKIE. HESA OFN THE SUBJEK LOTS. I KIN HARLY BELEEV THAT HE SPEN SO MUCH TIME DREEMAN ABOUT SOMBUDY PUTTIN A GO3HUNERT IN A LIL OLE 170. BUT MAGINE IF YOU CAN TURNIN A O3HUNNERT 3150RPMS WITH A 80"X61" PROP! WEED GO BY OLE HAROLD LIK SIXTY

ONE MOR THAN GAYHORYN YER COUWL WOOD LOOK LAK A KINNER WITH SUM O URE ENGINE STIKIN OUT IFN YOU USE THE 170 ENG MOUNT CAUSE THAT OLE G HUNKERS GOTS A OIL COOLER ONA TOP

[Mike Smith]

George,
I'm just curious, does leaving the mixture at the "cruise lean setting" harm our engines in any way? ... or help them avoid the lead buildups? I thought most people moved the mixture back to a more rich setting for the descent. Besides having to remember to go "rich" on a go-around, are there any other considerations for a "lean" descent?

[GAHorn]

Mike, the assumption is that a descent and landing will always be a lesser power setting than the cruise power that was leaned for, in which case no harm is done to the engine and less lead deposits occur. (Of course, I use TCP so I could be accused of overkill.)
But,...the TCM recommendations on their fuel injected engines is to leave it in the cruise-leaned condition all the way to the chocks, and that's what I do with the C-414's and 421's I fly, with good results. I also leave the constant speed props in cruise all the way to touchdown (prevents pax concerns due to perceived engine speed increases), so any go around would require me to shove them all forward simultaneously, not a difficult memory item.
Leaving a carb equipped engine leaned for descent thru landing works just as well for the same reasons, and that's what I do with mine. Never had a problem, and can't see anything wrong with it. A go around just requires shoving both throttle and mixture forward. Pretty simple, since we're also remembering to do the carb heat also. (Truth being that I apply carb heat before final power reduction in the pattern, then after no carb ice is confirmed, I shove it back off for the rest of the approach/landing.)
But any go around is actually a planned manuever so it's never a surprise, right? Throttles/Props/Mixtures forward, flaps up, positive rate of climb--retract the gear.)