Happy Monday!

I've been debating on an aircraft to purchase for a while. Wrestling between what my needs are now, vs what they will be in a few years.

Ultimately I want to travel/build hours/instruct in a tailwheel. No aspirations of becoming an airline pilot, the end goal is instructing. I looked into a Champ, and they are probably the best trainer, but they certainly don't travel well with a wife and dog and baggage for a week or so. That led me to either a Cessna 170/Stinson 108. I actually lean more towards the Stinson in all aspects except fuel burn.

All the research i've done shows that Stinsons very rarely get less than 10GPH, almost regardless of the powerplant. Whereas the 170 i've seen multiple reports of sub 7 throttled back.

I couldn't care less about speed, but it seems that it's either not good for the Franklins to be throttled back (which I don't quite understand), or it doesn't affect the fuel burn (which would seem even weirder).

Can anyone expand on the fuel burn of the Stinson and why it seems to be 10gph no matter what?

The Stinson is a good deal cheaper than a 170, takes off shorter, carries a bit more...I just find the fuel economy to be a big downfall. Thanks for any insight!

That 10gph for Stinson's is for Franklin engines. It's not because they can't run on less gph, but those engines like to be ran full power all the time for their health. It's not advised to pull them back. The engine supposedly lasts longer and runs better at full power. And most of us that fly them do so, and have 10gph all the time.

If you find one with something other than an Franklin, then that doesn't apply. But the difference of cost for 3gph, is negligible to overall costs of aircraft ownership and operation.

Tadpole wrote:That 10gph for Stinson's is for Franklin engines. It's not because they can't run on less gph, but those engines like to be ran full power all the time for their health. It's not advised to pull them back. The engine supposedly lasts longer and runs better at full power. And most of us that fly them do so, and have 10gph all the time.

It's really interesting to hear about this. Is this the case using any type of fuel? I know about the issues Franklins have using leaded fuel and fouling plugs and gunking up valves. I'm wondering if the problems from running 100LL led to the belief that they needed to be ran hard all the time to blow out the lead deposits, and with ethanol free avgas you might not have any issues? Or maybe it's something completely different! Either way, i'm interested.

Tadpole wrote:But the difference of cost for 3gph, is negligible to overall costs of aircraft ownership and operation.

I've never owned an aircraft before, so I am purely going by math here. But if I estimate 100 hours/yr, fuel costs would be $3000 for 10gph and 2100 for 7gph. I just used $3/gal to keep the math simple. $900 seems like a pretty good chunk to me. Definitely doesn't offset the (sometimes) $10k difference in purchase price, but over time it certainly could.

Any fuel, even those running mogas run them hard.

$900/yr, IMO, is negligible in your yearly costs to own / operate. I wouldn't let 3gph be what makes / breaks your decision.

AP2Pilot wrote:

Tadpole wrote:That 10gph for Stinson's is for Franklin engines. It's not because they can't run on less gph, but those engines like to be ran full power all the time for their health. It's not advised to pull them back. The engine supposedly lasts longer and runs better at full power. And most of us that fly them do so, and have 10gph all the time.

It's really interesting to hear about this. Is this the case using any type of fuel? I know about the issues Franklins have using leaded fuel and fouling plugs and gunking up valves. I'm wondering if the problems from running 100LL led to the belief that they needed to be ran hard all the time to blow out the lead deposits, and with ethanol free avgas you might not have any issues? Or maybe it's something completely different! Either way, i'm interested.

Tadpole wrote:But the difference of cost for 3gph, is negligible to overall costs of aircraft ownership and operation.

I've never owned an aircraft before, so I am purely going by math here. But if I estimate 100 hours/yr, fuel costs would be $3000 for 10gph and 2100 for 7gph. I just used $3/gal to keep the math simple. $900 seems like a pretty good chunk to me. Definitely doesn't offset the (sometimes) $10k difference in purchase price, but over time it certainly could.

Even if you don't care about the speed it is part of the equation. My 180 burns less fuel over distance than my Sedan because of the 40mph increase in cruise speed.

akaviator wrote:Even if you don't care about the speed it is part of the equation. My 180 burns less fuel over distance than my Sedan because of the 40mph increase in cruise speed.

Very true. I should have mentioned, it just doesn't affect my mission enough to worry about. I'm not going for distance, I am going for building time and experience, with a side benefit of leisure travel. If I am going 80 or 110, I am happy either way. Just seems weird that I would have to go full throttle in the Stinson...I am really curious about the 'why' behind that.

It isn’t about speed, its about miles per gallon. Keep that in mind. An airplane that has poor MPG may not be able to accomplish the mission. Consider flying the back country with few places for fuel. The trench comes to mind, hard for some airplanes to fly the trench so they have to fly the other route which requires fuel stops. Carrying fuel cans reduces the cargo you can carry and so on. How far does that 108 go on 10GPH, that is the important question.

Kurt

G44 wrote:....Consider flying the back country with few places for fuel. The trench comes to mind, hard for some airplanes to fly the trench so they have to fly the other route which requires fuel stops....
Kurt

I've heard people talk about "the trench" several times, but have no idea to what it's referring. Can you enlighten me?

JP256 wrote:

G44 wrote:....Consider flying the back country with few places for fuel. The trench comes to mind, hard for some airplanes to fly the trench so they have to fly the other route which requires fuel stops....
Kurt

I've heard people talk about "the trench" several times, but have no idea to what it's referring. Can you enlighten me?

It's a route from the lower 48 to Alaska and vice versa.


https://westcoastflyingadventures.com/2 ... he-trench/

Franklins are designed and built to much tighter tolerances than other engines. The piston to cylinder clearances in particular.

I have (actually had...his crankshaft broke in 2 so he's not flying anymore) a buddy with a 108 with a Franklin 165. I have a 170B with an O-300-A.

We both cruise just shy of redline in both planes. The 145 HP O-300-A burns 7.5-8 GPH at 2650 and his 165 HP Franklin burns 9.5-10 at 2750 cruise.

There is no magic here. The variables are the different airframes, with the Cessna being more efficient IMO.

Then you have the Franklin making more HP than the Continental.

The lbs of fuel burned to get the same bhp at a specific % of power and rpm is pretty consistent (varies a little of course) from the little A-65 all the way up to the O-470.

The Franklins are great engines but they're different. Preston Tucker liked them enough to make them water cooled and stick them in his famous car...which probably led to the demise of the Franklin being competitive.

JP256 wrote:

G44 wrote:....Consider flying the back country with few places for fuel. The trench comes to mind, hard for some airplanes to fly the trench so they have to fly the other route which requires fuel stops....
Kurt

I've heard people talk about "the trench" several times, but have no idea to what it's referring. Can you enlighten me?

Sorry JP256 I should have been more specific. The trench is a route between McKinzie, BC to Watson Lake. It follows Lake Williston. This is one option on flights between lower 48 states to Alaska. About 340nm between with no place to stop for fuel. There are some strips along the way one could fuel their plane using cans hauled in the baggage area but that is a pain and reduces your cargo carrying ability. Also, the locals around some of these strips can be a bit unwelcoming. Although 340nm doesn’t seem too far but if the winds are unfavorable or low ceilings make you turn around then fuel could be a real issue.

Kurt

If you add in the the Stinson’s limited fuel tank size - with the 10gph fuel burn combined with your VFR minimums for reserve - you don’t really have a great range for a hauler.

AP2Pilot wrote:

akaviator wrote:Even if you don't care about the speed it is part of the equation. My 180 burns less fuel over distance than my Sedan because of the 40mph increase in cruise speed.

Very true. I should have mentioned, it just doesn't affect my mission enough to worry about. I'm not going for distance, I am going for building time and experience, with a side benefit of leisure travel. If I am going 80 or 110, I am happy either way. Just seems weird that I would have to go full throttle in the Stinson...I am really curious about the 'why' behind that.

I can’t help you on the Stinson question but as also being new to aviation and having owned a slow plane and now a slower one. I think after a couple cross countries you will be wishing you had a little better cruise speed along with good range. Going from 115 mph down to 85 was a huge let down for me when planning leisure travel. Another thing was my new one only prefers mogas which adds to more planning.

Great response. Thanks for clarifying!

My 108-1 burned about 8.5 gph +/- .3 traveling around 8000', leaned and the throttle pulled back about 1/4". I don't remember the RPM, but I always flew it the same way, and thought the variation was pretty odd.

I had a -1 with the stock 150hp, what a great flying aircraft, yes it did kinda suck fuel, but it also did not like 100ll I kept getting stuck valves until I ran mogas. I guess the savings between the two fuels would make up for the fuel burn.

I always day dreamed of flying and traveling until it became a pain in the rear logistically and time, having to always have to find a rental car or stuck on the ground due to weather. Now I just hop on an airline or drive.

I own a J3 Cub now, low and slow with the door open.

corefile wrote:If you add in the the Stinson’s limited fuel tank size - with the 10gph fuel burn combined with your VFR minimums for reserve - you don’t really have a great range for a hauler.

That’s the nice thing about the -3. It has 10 more gallons of fuel than a -1 or -2 for 50 gallons total. ~4 hours of range isn’t too bad. Plus the gross weight is 170lbs higher.

robw56 wrote:

corefile wrote:If you add in the the Stinson’s limited fuel tank size - with the 10gph fuel burn combined with your VFR minimums for reserve - you don’t really have a great range for a hauler.

That’s the nice thing about the -3. It has 10 more gallons of fuel than a -1 or -2 for 50 gallons total. ~4 hours of range isn’t too bad. Plus the gross weight is 170lbs higher.

Correct and the dash 3 also has larger diameter fuel lines which is required in the bigger engine upgrades, and the larger vertical stabilizer and rudder.

Thank you for the replies!

After talking about it and thinking it over a ton, I think I am totally changing directions. At least for now, I am going to search for a small trainer, such as a champ. I am going to sacrifice the traveling aspect for cheaper entry price/operating costs/maintenance costs. I haven't come across a single post of someone regretting buying a champ. If nothing else, it will be a great way for me to experience aviation the way it was when those planes were built, hand propping a 65hp and learning to 'fly the wing' using nothing but the bare basic instruments and a handheld radio. Just seems like the right way to start airplane ownership to me, even if I step it up in a few years. I'll be sure to post when I finally score one. Thanks!