Your fuel flow on takeoff versus the redline

[woxof]

Of course, I am talking about the bigger engines with fuel flow guages.

What is your FF as compared to the redline and how important is it to you. According to an article I am reading......

"fuel flow is vital for cooling, and that redline is a minimum, not a maximum. The vast majority of all these engines are set too lean by the manufacturer's recommendation! Almost all mechanics will resist this idea, and they seem to think that if the book specifies a fuel flow redline, then a little less than redline is somehow "better." If you cannot get your mechanic to set this up properly, find a mechanic who will. If your full-power fuel flow is a bit over redline, so much the better! You can always manually lean it back to redline if you wish, but you can't do much with a fuel flow that is less than redline. Even half a gallon per hour can make a large difference in CHTs right after takeoff, and during climb."

 

[denverpilot]

Couldn’t tell you what my fuel flow is on takeoff in most things I fly. No gauge, no limits, no measurement.

 

[simtech]

I had read that typically your fuel flow at full power takeoff will be the first 2 numbers in your horse power. So 180 hp would be 18gph in take off and full power climb out. My 180 actually burns about 16 gph on take off. I think I read that in an EAA mag once. I noticed mine was less but never thought anything else about it.

With all these gadgets I wonder how much info is too much. My mechanic said if I got an engine analyzer then I would find all sorts of problems with my plane. hahaha I mean planes have flown for over 50 years and some with no fancy digital numbers. But I will admit my FS450 is down right awesome! so..Im not sure I how really lean in that aspect. haha

 

[Stewartb]

Constant speed prop.... take off is redline.

 

[BigBadLou]

According to an article I am reading......

Is the article author from Alaska or Canada? Then I understand his worry.
Otherwise, down here in hot TX, I am fine with my fuel flow being below redline, seeing how I do majority of my flying above ISA in high-DA environment.
I'll inquire with my mechanic, he's a smart guy and will have an opinion on this. Curious what he says.

 

[Clark1961]

Continental has a SB which explains the fuel trim setting procedure and lists the target flows/pressures for their fuel injected engines. The Term “Red Line” is not used in the service bulletin. Anyway, I’d go with the manufacturer’s recommendation.

 

[Clip4]

Of course, I am talking about the bigger engines with fuel flow guages.

What is your FF as compared to the redline and how important is it to you. According to an article I am reading......

"fuel flow is vital for cooling, and that redline is a minimum, not a maximum. The vast majority of all these engines are set too lean by the manufacturer's recommendation! Almost all mechanics will resist this idea, and they seem to think that if the book specifies a fuel flow redline, then a little less than redline is somehow "better." If you cannot get your mechanic to set this up properly, find a mechanic who will. If your full-power fuel flow is a bit over redline, so much the better! You can always manually lean it back to redline if you wish, but you can't do much with a fuel flow that is less than redline. Even half a gallon per hour can make a large difference in CHTs right after takeoff, and during climb."

I would quit reading who ever the author of that junk is.

 

[unsafervguy]

An engine needs a certain weight of fuel and air to produce a certain power output at current conditions. It's all math. The manufacture states a minimum fuel flow at std conditions. Anything above that is waste. Yes it will cool the engine, mostly because you are not making rated power so the heat output is less, again physics and math.
These are air cooled engines, not fuel cooled. The proper way to operate an engine is at proper fuel flow, and get the cooling system right. To many manufactures use a higher flowing carb to make up for crappy cooling systems. The new management systems are just showing how bad the cooling systems are. There are some great articles in the EAB world about setting up properly jetted carbs and cooling systems.

 

[JAWS]

The airframe manufacturer maintenance manual is the first place to check. They certified the airframe and engine combination. If nothing is there, or if they make a reference, then the engine manufacturer would be next.

The specific aircraft and engine would be nice to know.

 

[Tarheelpilot]

Of course, I am talking about the bigger engines with fuel flow guages.

What is your FF as compared to the redline and how important is it to you. According to an article I am reading......

"fuel flow is vital for cooling, and that redline is a minimum, not a maximum. The vast majority of all these engines are set too lean by the manufacturer's recommendation! Almost all mechanics will resist this idea, and they seem to think that if the book specifies a fuel flow redline, then a little less than redline is somehow "better." If you cannot get your mechanic to set this up properly, find a mechanic who will. If your full-power fuel flow is a bit over redline, so much the better! You can always manually lean it back to redline if you wish, but you can't do much with a fuel flow that is less than redline. Even half a gallon per hour can make a large difference in CHTs right after takeoff, and during climb."

That sounds like some mike Busch

 

[Radar Contact]

Of course, I am talking about the bigger engines with fuel flow guages.

What is your FF as compared to the redline and how important is it to you. According to an article I am reading......

"fuel flow is vital for cooling, and that redline is a minimum, not a maximum. The vast majority of all these engines are set too lean by the manufacturer's recommendation! Almost all mechanics will resist this idea, and they seem to think that if the book specifies a fuel flow redline, then a little less than redline is somehow "better." If you cannot get your mechanic to set this up properly, find a mechanic who will. If your full-power fuel flow is a bit over redline, so much the better! You can always manually lean it back to redline if you wish, but you can't do much with a fuel flow that is less than redline. Even half a gallon per hour can make a large difference in CHTs right after takeoff, and during climb."

As you've already seen, like most things you will get several different opinions.

My feeling is what you quoted has value. Most smaller GA engines, this won't be a big factor. According to people more knowledgeable than me that operate and maintain big-bore Continental engines, this has merit. I subscribe to the 10% rule that @simtech mentioned. When I bought my plane, the fuel flows were already set up accordingly. I have IO-470's that are rated at 260 HP. My factory fuel flow gauge has a red-line of 23.3 gph. Before I got my engine monitor with FF all I knew was that both needles exceeded red-line during takeoff. After getting my monitor, my engines are real close to 26 gph at takeoff. My mechanics and I are good with this.

Maybe @Ted DuPuis can chime in with his thoughts?

 

[Let'sgoflying!]

For Continental engines this is the current document (SID 97-3g) to refer to. (its changed 6 or 7 times in the past few years so keep checking for the -3h version)
Keep in mind there are plenty of folks who take to studying these engines way more than me who say that the full power takeoff fuel flow on the larger Continental engines is a few gph low. I would start out by reading on the Beechtalk board. I think they have the largest single group of IO-520/550 owners all in one place, where engine talk such as this is a daily thing.

 

[Fearless Tower]

That sounds like some mike Busch

It actually comes from Deakin.

Here is the problem I have with his statement: red line on the fuel flow gauge is published by the manufacturer as a ‘Limitation’.

So, what is the legal basis for an A&P to adjust the fuel flow to exceed that published limitation?


Sent from my iPad using Tapatalk

 

[Radar Contact]

It actually comes from Deakin.

Here is the problem I have with his statement: red line on the fuel flow gauge is published by the manufacturer as a ‘Limitation’.

So, what is the legal basis for an A&P to adjust the fuel flow to exceed that published limitation?


Sent from my iPad using Tapatalk

Understand your statement. All I can offer is that in my case, my published limitation was from 1973. We've learned a tremendous amount of information since then. You can always control the flow down with the red levers but can't go the other way. I've never flown a new Baron but I wonder if it's the same limitation as the 70's?

 

[Clark1961]

It actually comes from Deakin.

Here is the problem I have with his statement: red line on the fuel flow gauge is published by the manufacturer as a ‘Limitation’.

So, what is the legal basis for an A&P to adjust the fuel flow to exceed that published limitation?


Sent from my iPad using Tapatalk

The fuel flow specified by Continental is a small (~5%) range, not a target. The mechanic can adjust to the top of the range.

The fuel flow gauge is actually a pressure gauge and is subject to some error in terms of flow unless calibrated.

I check fuel flow once max power is set. I also watch temperatures since they are the only instrument which will indicate detonation.

Understand your statement. All I can offer is that in my case, my published limitation was from 1973. We've learned a tremendous amount of information since then. You can always control the flow down with the red levers but can't go the other way. I've never flown a new Baron but I wonder if it's the same limitation as the 70's?

The detonation margin required by certification should be adequate when the manufacturer specified flow rate (not 30 year old pressure gauge reading) is set. The detonation margin hasn't changed since the 60s, 70s, 80s, or even 90s. What does happen is gauges lose calibration and some mechanics get a little sloppy.

 

[Radar Contact]

The detonation margin required by certification should be adequate when the manufacturer specified flow rate (not 30 year old pressure gauge reading) is set. The detonation margin hasn't changed since the 60s, 70s, 80s, or even 90s. What does happen is gauges lose calibration and some mechanics get a little sloppy.

That makes good sense to me. In my case, the "red-line" is 23.3 gph and I have it set at 26. The marginal decrease down to 23.3 would have no impact on detonation but would have an impact on CHT's and potential longevity health of the engine. Would you agree?

 

[Ted]

Need to know which engine this is on.

Lycoming has the manufacturer settings set pretty well. Continental typically does not on turbo engines, but N/A ones are typically fine. You want to be on the rich side of the range.

 

[Clark1961]

That makes good sense to me. In my case, the "red-line" is 23.3 gph and I have it set at 26. The marginal decrease down to 23.3 would have no impact on detonation but would have an impact on CHT's and potential longevity health of the engine. Would you agree?

Which 470 do you have? Most of the carb'd versions have a max flow of a little over 22 gph. The injected, geared, and turbo'd versions have higher flow.

The problem with going overly rich is some power is actually lost. At least that's how I understand the term "best power rich of peak". I'd have to dig up some power curves to see how much power is lost. Overly rich also puts more lead (and fuel though that goes away) in the oil.

Obviously power output and engine temperatures are things we have to manage and you've chosen one approach to help you with that task. I try to keep my fuel flows set by the book and end up managing temperature using airspeed in the climb and LOP in cruise.

One nice thing about ownership is no one yells at us about engine management or tries to make us do stupid stuff like: 'enrichen a little bit on the take-off roll'. We get to make our own choices and adjust them as we learn more about our engines and their operation.

 

[Stewartb]

Continental factory FI setups are notoriously bad. A good mechanic will make setting the FI a priority when installing a Continental FI engine.

 

[Tarheelpilot]

It actually comes from Deakin.

Here is the problem I have with his statement: red line on the fuel flow gauge is published by the manufacturer as a ‘Limitation’.

So, what is the legal basis for an A&P to adjust the fuel flow to exceed that published limitation?


Sent from my iPad using Tapatalk

If the fuel flow is listed in the limitations section there is no basis for exceeding the limitation other than pic emergency authority to my knowledge.

The Mike Busch statement was a joke just in case anyone didn’t see that.....

 

[Ted]

If the fuel flow is listed in the limitations section there is no basis for exceeding the limitation other than pic emergency authority to my knowledge.

I think technically that's true. With that said, the biggest Twin Cessna shops all use max fuel flow settings from Continental as the minimum they'll set to.

 

[Tarheelpilot]

I think technically that's true. With that said, the biggest Twin Cessna shops all use max fuel flow settings from Continental as the minimum they'll set to.

Is that above the redline published in the limitations section? I ask because I really don’t know.

Whenever I setup big continentals I hookup gauges to the metered and unmetered fuel and set it according to the continental guidance. Makes for happy pilots and happy checking accounts. Frankly I never looked at a ff limit in the poh when setting up a continental.

 

[Ted]

Is that above the redline published in the limitations section? I ask because I really don’t know.

Whenever I setup big continentals I hookup gauges to the metered and unmetered fuel and set it according to the continental guidance. Makes for happy pilots and happy checking accounts. Frankly I never looked at a ff limit in the poh when setting up a continental.

Continental M-0 has the fuel flow limits that are specified from the factory. First off your injectors need to be clean when the calibration is performed or else the pressures will be incorrect and the fuel flows will be low. However, on the big bore engines (no experience with the (TS)IO-360s) they'll tend to run warm in the climb if you don't have the takeoff fuel flow cranked up at the max setting or in some cases over. The 340s and 414s are especially known for this.

Basically, you can always pull the mixture knob back, but you can't push it further forward than full rich. Obviously too rich would be an issue, but it takes a lot to get there.

 

[Tarheelpilot]

Continental M-0 has the fuel flow limits that are specified from the factory. First off your injectors need to be clean when the calibration is performed or else the pressures will be incorrect and the fuel flows will be low. However, on the big bore engines (no experience with the (TS)IO-360s) they'll tend to run warm in the climb if you don't have the takeoff fuel flow cranked up at the max setting or in some cases over. The 340s and 414s are especially known for this.

Basically, you can always pull the mixture knob back, but you can't push it further forward than full rich. Obviously too rich would be an issue, but it takes a lot to get there.

I agree. If using proper gauges and following the manufacturers guidance the result is a very rich full forward mixture and a good running engine. I guess my only nit to pick, which I’m sure you didn’t really mean, is to say you just crank it to full on roll with it. As I said with proper equipment and a proper fuel trim the resulting mixture at full forward on the cockpit control is very rich.

 

[Grum.Man]

I set my IO-550G to the recommended settings. One of the last things you do in the procedure is to slowly pull the mixture out and look for a 50-75 rpm rise before the engine cuts. This is to make sure the engine is running a little rich as the rpm increase the engine is going lean. I see around 23 gph on takeoff with 285 rated hp. Having the pressures and fuel flow off by just a little bit on the 550 really makes a difference in how it runs.

 

[Ted]

I agree. If using proper gauges and following the manufacturers guidance the result is a very rich full forward mixture and a good running engine. I guess my only nit to pick, which I’m sure you didn’t really mean, is to say you just crank it to full on roll with it. As I said with proper equipment and a proper fuel trim the resulting mixture at full forward on the cockpit control is very rich.

No, you definitely don't crank any of the fuel adjustments all the way forward. That would result in a bad running engine.

However saying that the proper gauges and manufacturer's guidelines for Continental results in a "very rich full forward mixture" I'll disagree with in some cases. Like I said, on the 340s/414s especially, you'll tend to have hot engines towards the top of climb because the fuel flow at your climb power settings will be too low. Sure, the engine will seem like it runs fine, but you'll have higher CHTs in climb. When the CHTs are hot in climb it can be hard to get them back down any in cruise and thus they end up running hotter for the entire flight. On naturally aspirated it's less critical, although the 310 would tend to get hot in the climb until I got to 8,000 ft.

With no offense intended, frequently A&Ps only see a small portion of how engines operate and don't necessarily see the full realms. That often applied to the engineers at the OEM, as well.

 

[Tarheelpilot]

No, you definitely don't crank any of the fuel adjustments all the way forward. That would result in a bad running engine.

However saying that the proper gauges and manufacturer's guidelines for Continental results in a "very rich full forward mixture" I'll disagree with in some cases. Like I said, on the 340s/414s especially, you'll tend to have hot engines towards the top of climb because the fuel flow at your climb power settings will be too low. Sure, the engine will seem like it runs fine, but you'll have higher CHTs in climb. When the CHTs are hot in climb it can be hard to get them back down any in cruise and thus they end up running hotter for the entire flight. On naturally aspirated it's less critical, although the 310 would tend to get hot in the climb until I got to 8,000 ft.

With no offense intended, frequently A&Ps only see a small portion of how engines operate and don't necessarily see the full realms. That often applied to the engineers at the OEM, as well.

Ted I don’t think most a&p’s use proper tooling or follow the TCM SB for setup. The Porta Test boxes are not cheap and they require reguarlar calibration. I also commonly found the cockpit gauges for fuel flow, manifold pressure and rpm to frequently be inaccurate to the point of limiting their usefulness. I do not doubt what you are saying. It’s just been my experience that when using the right tooling that’s properly calibrated in accordance with the SB, I haven’t had any issues like you describe.

Edit: I do recall one instance where there were issues doing the fuel setup. Two of the guys were working on setting up new engines on a turbo Cessna and the readings were all over the place. Turns out a new engine can run for quite a while with no oil.....yeah we had the pleasure of replacing that engine again.

 

[Ted]

Ted I don’t think most a&p’s use proper tooling or follow the TCM SB for setup. The Porta Test boxes are not cheap and they require reguarlar calibration. I also commonly found the cockpit gauges for fuel flow, manifold pressure and rpm to frequently be inaccurate to the point of limiting their usefulness. I do not doubt what you are saying. It’s just been my experience that when using the right tooling that’s properly calibrated in accordance with the SB, I haven’t had any issues like you describe.

You are correct that most A&Ps don't use the proper equipment or do it correctly. That's another issue and can cause all sorts of other problems. It also depends on the aircraft as some had much better cooling than others, and then the condition of the baffles (another area most A&Ps don't spend much focus on).

Then there's the question of how good a job Continental did on setting the numbers in the first place, which is another matter for debate. The OEM parameters didn't always take into account how the plane would be flown and usually looked at limits vs. goals.

I can tell you that if the 414 was set at the max values, the climb CHTs would've been hot getting to the flight levels, and that was with the baffles in very good shape. Same goes for any other 340/414 out there.

 

[Clip4]

An engine needs a certain weight of fuel and air to produce a certain power output at current conditions. It's all math. The manufacture states a minimum fuel flow at std conditions. Anything above that is waste. Yes it will cool the engine, mostly because you are not making rated power so the heat output is less, again physics and math.
These are air cooled engines, not fuel cooled. The proper way to operate an engine is at proper fuel flow, and get the cooling system right. To many manufactures use a higher flowing carb to make up for crappy cooling systems. The new management systems are just showing how bad the cooling systems are. There are some great articles in the EAB world about setting up properly jetted carbs and cooling systems.

You are partially correct, but a generally rich mixture accounts for a significant amount of cooling in an air cooled engines, especially at high power settings. Too lean of mixture can lead to high cylinder head temperatures and valve damage at high power settings.

 

[unsafervguy]

You are partially correct, but a generally rich mixture accounts for a significant amount of cooling in an air cooled engines, especially at high power settings. Too lean of mixture can lead to high cylinder head temperatures and valve damage at high power settings.[/QUOTE
sorry, that only applies if you are running below the manufactures stated BSFC number for the engine. engine manufactures state a BSFC for their engines. that number covers the detonation. anything more is wasting gas just to overcome a crappy cooling design. very common in production aircraft. the problem is you are stuck with it on a certified aircraft. continental is even worse because of the design of the fuel injection system they use. bottom line is flows should be set to manufactures numbers, if the chts are running high look at the cooling system. dumping gas at it is just a band aide to cover a bad cooling system. if you have time search vansairforce for posts by danh on fuel flows and cooling. he has done a lot of research on cooling and fuel mixtures.

bob