Is cruising at lower power bad for the engine?

[Bolter]

5 hours ago, Pinecone said:

Carson speed is not the best economy.  It is the least bad economy.  Or it is the fastest, where the fuel burn is not excessive over best economy.

Best economy is least drag, which is the same as best glide.  But no one wants to cruise at 80 knots in a Mooney.

Thanks for the clarification.  So then he is going too fast for the max flight time with least fuel goal?

[Pinecone]

Yes.

But, I still stand by that he bought the wrong airplane.

A Cub would give him time with half the fuel burn.

[TStepp]

The Mooney is a beautiful machine.  It has proven versatility.

One must choose which variable is to be optimized.  It all depends upon your mission.
   If you want to get there faster, optimize distance / time (nm/hr).
   If you want to get there cheaper, optimize cost / distance ($/nm).
   If you want to log time, optimize cost (fuel burn) / time ($/hr).

As missions vary, one can choose which knob to tweak.

The OP wrote "I'm trying to burn as little fuel as possible so I can prolong my flights for time building."
In that case, it doesn't matter how far you go or how fast.  The whole goal is to log time for as little $ as possible.

I've owned my '67 F for >20 years and have ~1500 hrs. in it.   

At 17" MP / 2000 rpm level flight, 105 mph (91 kts), I can lean the IO-360-A1A until she barely maintains altitude @ 5.4 gph.   I've built ~500 hours over the past 5 years flying around southern CA in this configuration.  My purpose was to build time towards my CSEL & ATP.   I didn't need to go fast - just needed to log time.  With avg. fuel prices ~$6 / gal., this configuration has saved me several $k vs. flying faster.

Note:  One can also log time while taxiing.  You don't have to be burning 5-6 gph.  Land long at larger airport runways and extend your taxi-back.  15-20 minutes on the ground at 1.3 gph. makes the average even lower.

Of course, when I want to get there faster, I push the "Go" knob and get there at ~170 mph (148 kts).   That's ~60% faster for twice the fuel burn rate.   I don't think a Cub can do that.

It's really nice to have the option.    

[A64Pilot]

On 2/6/2024 at 2:54 PM, Pinecone said:

Yes.

But, I still stand by that he bought the wrong airplane.

A Cub would give him time with half the fuel burn.

No it won’t.

Neighbors Legend cub burns 6 GPH and cruises at 80 kts I think which gives it 13.3 MPG.

My J at 21 squared and LOP burns 6 GPH also, but is at 120 kts, giving it 20 MPG.

The Mooney can fly slower of course but even 120 Kts just feels to slow to me, but if you really needed for some reason to extend time aloft it will I’m sure fly at 5 GPH, maybe less, I don’t really know, whatever gives you 90 kts I believe that’s best glide speed? We would be looking for max endurance speed, but is that published for our aircraft?

Sometimes on a lazy Summer afternoon when there is no destination, the mission is just to fly I’ll fly at 120 Kts, but I usually drag the 140 out on those days and fly it instead.

Point is if you want to you can fly at 6 GPH in a J model and get 20 MPG, or you can fly faster and burn more fuel, while the Cub you can’t fly much faster than 80 kts. I’m it sure about the 80 kts, but think that’s about right, but it’s not breaking 100 kts in level flight I’m sure of that. I’m faster in my C-140 than the Cubs and it’s only a 90 kt airplane.

Point is, is it’s their airplane and if they choose to fly a Mooney slow why not? Just keep the temps in the green

[Pinecone]

I meant J-3

 

[A64Pilot]

J-3 is even worse, by worse I mean realistically you can’t go anywhere.

Can’t is a strong word because there is no where in the US that you can’t walk to, so by can’t I mean people don’t because they are so slow, get there faster by driving, and their fuel burn over distance travelled sux. Yeah people go places in a Cub, but they do so so they can talk about doing it.

It’s a 15 min flight for me pulled back to 135 kts to fly to breakfast Sun morning, the Cubs it takes over a half hour.

My C-140 with the same engine will cruise at 110 MPH, but 105 is a relaxed 2400 RPM with the C-85, a J-3 70 mph or so?

Many J-3’s have been converted to 0-200’s due to unavailability of engine parts, the C-85’s except for crankshafts aren’t so bad but cranks are like unicorn horns, A series engines the Jugs I believe don’t exist anymore.

So if you looking at any of the old Continental powered airplanes it would behoove you to find one either that has the 0-200 conversion, or the 0-200 crank in a C-85 case as parts are drying up and conversions can run the value of the airplane or higher.

The Cubs for some to me illogical reason have a cult following, maybe it’s the cute name or some think a yellow Cub is cute, but they are slow as dogs, don’t really fly very well, can’t carry anything and aren’t comfortable, they don’t even have a heater and the engines are over cooled which doesn't help life, especially cylinder.

I got my seaplane rating in one as have thousands I’m sure.

If you want a Cubish airplane made by Piper look hard at the PA-12 Super Cruiser, a Super Cub is most probably higher priced than many want to pay. The Super Cruiser especially if it has either a 150 or 160 engine is usable.

To build time cheaply means buying something that you can sell easily, but more importantly something that can burn auto fuel as most can, burning car gas is where you save money.

I’m not a Cub fan, WAY overpriced for what you get.

[A64Pilot]

I just had a thought ref “is flying at low power bad on the engine”

Now you guys check my numbers because they may be wrong.

A Carbon Cub has a 180 HP Lycoming I believe?

I also believe it’s limited to 5 min at 180 HP, after the 5 min your restricted to 80 HP continuous.

Then if that’s correct and my math is right then the 180 HP Lycoming in the Carbon Cub is restricted to a maximum cruise power of 45%.

Surely it stands to reason that if that were bad for the motor then Lycoming wouldn’t allow it, or there would be reports of engine problems in Carbon Cubs by now? I’m sure many don’t follow the limitation but think quite a few likely do.