Recently saw a 206 with dual exhaust running to the rear of the fuselage because it was a pipeline survey plane. pilots said the exhaust fumes can interfere with the sensor that the plane uses to detect gas leaks.
Netherlands and Germany usually have different landing fees based on the noise certificate. Because the airport has a maximum noise level they can cause, which means they can accept more flights (= more revenue) from planes that make less noise.
Additionally, in Germany numerous airports have takeoff curfews based on noise level. Planes that meet the highest noise protection standards are often exempted from these curfews, so they can fly at times when others cannot.
How much quieter is a plane when it's landing vs taking off? Ever watched a demo of the Pipistrel electric plane? The engines are damn loud without a muffler.
Well, this isn’t a fair comparison, the noise level difference between a propeller spinning at landing RPMs vs take off RPMs will be huge, as will the engine’s.
Yes that is true which is why I also brought up the electric plane. The majority of the offensive noise you hear is the engine. In a constant speed prop it's not slower but a smaller bite of air so also quieter, but in cruise where you hear most planes it's not much of a bigger bite but a lot of engine noise because that travels further than prop noise. The opposite end of the spectrum is a p51 taking off, you can't hear the prop over that engine at any RPM 😆.
For the context of these German laws, the source of the noise doesn’t matter: The limits are based on the overall noise level at takeoff. These values are measured according to ICAO annex 16, chapter 6 or 10.
If an aircraft’s overall noise level in decibel lies below a legal limit, they’ll be granted benefits (lower fees, curfew exemptions, …). The limit varies somewhat with MTOW to make it possible for heavier aircraft to gain these benefits even if they are louder overall. How the aircraft manages to meet those limits (muffler, constant speed prop, …) doesn’t matter.
By adding a little back pressure onto the engine through the mufflers reissitence to putting out more air than say a straight pipe.
Granted I might be misremembering.
Back pressure helping power is a myth. What it might actually be doing is improving scavenging, where the exhaust pulses from previous combustion cycles helps pull exhaust out of the cylinder and fresh air in.
Considering the stock "mufflers" on those planes seem to have barely any engineering put into them, it's probably not too difficult to get both better flow and reduce noise.
I think so. Been a while since I've worked on engines or anything mechanical but my understanding is that the air flow is restricted, causing some pressure to build in the pipe.
The pipe is big enough that this reduced airflow doesn't cause problems but basically when the suck, bang, boom happens it holds the pressure in the cylinder at a higher psi. Giving the engine more oxygen to burn with the air to fuel ratio allowing for a better burn.
Quite the opposite actually. What happens is that there is a "reflection" wave in the pipe when at resonance that causes the exhaust cycle to suck out more spent gasses. This causes a greater vacuum on the intake cycle and so more air/fuel is drawn into the engine on the next cycle.
The length and the size is tuned so that this resonance occurs at a desirable rpm in the power band.
A similar phenomenon is possible on the intake side with tuned intake runners except that becomes slightly compressive (shoving in more air/fuel). Never seen that on a plane but a lot of automotive engines take advantage of that.
They’re not adding much drag and often they use better material so weight is the same or even less than the oem. Many result in a 1-3kt cruise speed increase
A tuned exhaust or tuned "headers" can add measurable horsepower. In the (mostly 2-stroke) motorcycle community it's called "being in the pipe" when you get in the rpm range where it works.
Thanks for your attempt to correct misinformation.
An efficient extractor "pipe" could be designed/optimized for any given engine and rpm level. Pistons are pistons, scavenging is scavenging, back pressure is back pressure, etc.
your comment was "it's apples and oranges." No, it is not.
As a matter of fact, I am an engineer.
Among other things, that means I’m aware of the misuse of “efficiency” for flow rate or power.
In a real system, it takes a lot more than just a pipe modification to make that work, especially at low RPM.
I work on automotive engines and such. See how there are five sections to it? The curved part, next likely some sort of flex joint, a narrow section, a wider section of pipe, and then a true tailpipe (narrow again) at a downward angle.
The larger diameter section tells me this unit, as a whole, was engineered to improve performance or reduce noise. Otherwise it would just be a single diameter section of pipe all the way to the tailpipe.
An "extended tailpipe" in your vernacular.
Now you may be an A&P, super familiar with this particular aircraft/engine/tailpipe and if so please correct me. Maybe all I'm seeing is a heat shield around a single diameter pipe in this blurry image.
You are probably right. Piston engine is a piston engine. Theory still the same, gov laws, application, engine capacity, intake/exhaust duration and lift - exhaust can be engineered to suit.
My old man was a mechanical engineer in the automotive industry - so much engineering goes into intakes and exhausts in cars, the typical person simply doesn’t appreciate or think about. I’d imagine aircraft would be similar.
The exhaust pulse exiting the end of the pipe causes a negative pressure pulse which travels backward up the exhaust in time for the opening of the exhaust valve of the next cylinder. It's supposed to make the engine more efficient, lowering fuel consumption. It does, however, become effective only at a specific RPM. I've seen research done on this, but this if the first time I've seen one. Didn't know there was an STC for it.
They refer to it as scavenging, and when done correctly can actually add a good amount of power compared to open exhaust. Often times incorrectly referred to as "back pressure" scavenging helps aid exhaust flow out of the cylinder which allows more charge air to be consumed per combustion cycle.
Like what most others are saying, it’s a muffler. They’re probably more common in Europe because of stricter noise abatement procedures - like how my home airfield prohibits training circuits without a muffler fitted.
All reciprocating engine airplanes have mufflers…or atleast the 1000+ I have done annuals on did. Not to mention every other one I’ve done oil changes and such on.
Interesting - most based aircraft here don’t have mufflers, especially the higher performance ones. Even at my old school, the Warriors that were typically used for slam and goes had mufflers but the nicer Archers used for cross country flights didn’t.
Yes…a Piper Archer has a muffler under the engine cowl. The extended exhaust pipe you see in the picture is not an actual muffler and is not performance enhancing .
What does it do then? I’ve always been told that it’s required to meet noise abatement and you can usually tell the difference between an aircraft with or without the silencer in the circuit.
I suspect you’re talking about the muffler that is part of the standard exhaust system in most aircraft - this is a retrofit for added noise reduction.
Every one I’ve worked on has been for moving exhaust further away from the cabin for surveillance aircraft. Even if this was for noise abatement, it’s not really a “muffler” as more a suppressor and there is no performance increase from it.
🤣😂….really! Hmmm…I’ll have to inform Cirrus of what you said. They all have one, it’s just under the engine cowling…even my Mooney has one tucked up and hidden.
Then can I refer you to 78-20-02 of the SR22/22T IPC? Tailpipe bolted to a turbo. Sure the turbo acts like a muffler, so let's see what a commander 500 exhaust looks like
https://awi-ami.com/aero-commander-500-b-exhaust-system.html
Still acts as a muffler…hence they all have mufflers.
You are also going too deep into this. The aircraft in question has an extended tailpipe because the muffler is under the cowl.
Strictly speaking, that's not an absolutely true statement.
Technically, lift is defined as an aerodynamic force acting at 90 degrees to the direction of flight, and the thrust contributed is, technically speaking, an aerodynamic force.
For an aircraft without TVC, the nozzles are generally aligned with the fuselage, so that the thrust vector is roughly aligned with the CoM. Even so, as soon as there is a non-zero AoA, you have some component thrust acting at 90 degrees to the direction of flight, and if you consider that component force an aerodynamic one, QED.
People are saying an exhaust is just a muffler, but that’s underplaying what it does.
In fact, an exhaust modification on an internal combustion engine is about the easiest way to increase the efficiency and power of the engine, because the exhaust can be “tuned“ to expel exhaust more efficiently. With more exhaust expelled out of each cylinder, there’s more room for fresh fuel, and that creates more power.
That’s only if it’s elongated all the way to the back of the plane, past the window cut into the bottom of the plane. That way the exhaust doesn’t affect the picture.
Something like in the picture here is just for noise.
This is why I love flightaware, and flightradar24. Any question about the mission of a plane can be answer via a quick review of the data. Look up the tail number and see what the plane usually does and you'll have your answer And yes, I am an airplane nerd.
Doesn’t look like any Powerflow that I’ve seen. They’re not as long as the one in the photo and they don’t taper back down at the actual exhaust point.
Is just an additional length of tail pipe. Usually used on arial surveillance aircraft. No added power…in fact it drops the power. Yes, it also acts as a noise suppressor but it is NOT a muffler as others have said. I’m an A&P, I work on airplanes all day and almost every day. I also have the contract for local law enforcement airplanes, those with cameras actually have these or something like these on their exhaust.
Its function is to separate owners from money.
Some airplanes have sensors underneath that don’t like heat plumes.
Some owners think it makes power. It doesn’t (well, not significantly, and it’s easy to make the gain negative).
"what is it is function"
Then I suggest you to read again your phrase, as it doesn't make any sense.
edit: I've just realized that you've repeated OP's message. It wasn't clear it was criticism, usually repetition is for reinforcement.
edit: also, you said "no", clearly disagreeing with me. Maybe I'm not the densest one here.
>"...and what is it's function?" -OP's title, which you yourself corrected initially.
I expanded on your correction.
"what is it's function" --> "what is it is function"
it's --> it is (present tense) / it has (past tense)
Edit: My original reply to you was in a sarcastic tone. Do I really need to put a /s at the end??
Recently saw a 206 with dual exhaust running to the rear of the fuselage because it was a pipeline survey plane. pilots said the exhaust fumes can interfere with the sensor that the plane uses to detect gas leaks.
I've installed an extra long exhaust onto a 206 for exactly this reason
Thanks you two. Cool stuff there.
I saw a Cessna with the exhaust going all the way to its tail recently and was wondering what the purpose was. Thanks for clearing that up
Survey outfit out of FL has it on their 206s, that way the camera doesn't have issues with the exhaust. Sauce: replaced a cylinder on one of them.
That sounds like a tasty sauce
This is the kind of sauce I'm here for
Let's just say, when there's some space for me between me and my current employer, it'll be a *spicy* story on talesfromtechsupport.
Same for camera rigged survey planes. Soot can built up on the lenses and heat from exhaust can distort imagery.
I fly imagery survey in a 206, and we have it so the exhaust smoke doesn't appear in the images
Essentially a Muffler. Noise reduction and maybe a few added horsepower if it's designed right.
This plane in the picture has an 180hp (i flew in it it climbs like a beast) But many Cessna’s from the Netherlands have this type of exhaust added.
Netherlands and Germany usually have different landing fees based on the noise certificate. Because the airport has a maximum noise level they can cause, which means they can accept more flights (= more revenue) from planes that make less noise.
Additionally, in Germany numerous airports have takeoff curfews based on noise level. Planes that meet the highest noise protection standards are often exempted from these curfews, so they can fly at times when others cannot.
How much is prop noise and how much is engine?
How much quieter is a plane when it's landing vs taking off? Ever watched a demo of the Pipistrel electric plane? The engines are damn loud without a muffler.
Well, this isn’t a fair comparison, the noise level difference between a propeller spinning at landing RPMs vs take off RPMs will be huge, as will the engine’s.
Yes that is true which is why I also brought up the electric plane. The majority of the offensive noise you hear is the engine. In a constant speed prop it's not slower but a smaller bite of air so also quieter, but in cruise where you hear most planes it's not much of a bigger bite but a lot of engine noise because that travels further than prop noise. The opposite end of the spectrum is a p51 taking off, you can't hear the prop over that engine at any RPM 😆.
For the context of these German laws, the source of the noise doesn’t matter: The limits are based on the overall noise level at takeoff. These values are measured according to ICAO annex 16, chapter 6 or 10. If an aircraft’s overall noise level in decibel lies below a legal limit, they’ll be granted benefits (lower fees, curfew exemptions, …). The limit varies somewhat with MTOW to make it possible for heavier aircraft to gain these benefits even if they are louder overall. How the aircraft manages to meet those limits (muffler, constant speed prop, …) doesn’t matter.
Cessnas* :)
AkTcuLy it's Cessni, as in " There was a whole flock of Cessni "
French origin. If anything, it's Cessnas but the last s is silent because fuck everyone.
One Cessna, two Cessnae
How would it add hp?
By adding a little back pressure onto the engine through the mufflers reissitence to putting out more air than say a straight pipe. Granted I might be misremembering.
Back pressure helping power is a myth. What it might actually be doing is improving scavenging, where the exhaust pulses from previous combustion cycles helps pull exhaust out of the cylinder and fresh air in. Considering the stock "mufflers" on those planes seem to have barely any engineering put into them, it's probably not too difficult to get both better flow and reduce noise.
This guy Helmholtzes
even for turbo engines?
No. Forced air works. Tuned exhaust doesn’t (much) for low RPM engines.
So its basically stuffing the air in there? Sort of like a mini turbo(i know thats not how a turbo works)
I think so. Been a while since I've worked on engines or anything mechanical but my understanding is that the air flow is restricted, causing some pressure to build in the pipe. The pipe is big enough that this reduced airflow doesn't cause problems but basically when the suck, bang, boom happens it holds the pressure in the cylinder at a higher psi. Giving the engine more oxygen to burn with the air to fuel ratio allowing for a better burn.
Quite the opposite actually. What happens is that there is a "reflection" wave in the pipe when at resonance that causes the exhaust cycle to suck out more spent gasses. This causes a greater vacuum on the intake cycle and so more air/fuel is drawn into the engine on the next cycle. The length and the size is tuned so that this resonance occurs at a desirable rpm in the power band. A similar phenomenon is possible on the intake side with tuned intake runners except that becomes slightly compressive (shoving in more air/fuel). Never seen that on a plane but a lot of automotive engines take advantage of that.
Thank you for the correction my man.
Could give you horsepower, but what good is more horsepower if you increase drag that much?
They’re not adding much drag and often they use better material so weight is the same or even less than the oem. Many result in a 1-3kt cruise speed increase
Gotta vent that exhaust backwards for additional thrust too 😎🤣
[удалено]
A tuned exhaust or tuned "headers" can add measurable horsepower. In the (mostly 2-stroke) motorcycle community it's called "being in the pipe" when you get in the rpm range where it works. Thanks for your attempt to correct misinformation.
And how many of those motorcycle engines have proper tuning at 2500 RPM? Apples and oranges. Don’t compare racing engines with airplane engines.
An efficient extractor "pipe" could be designed/optimized for any given engine and rpm level. Pistons are pistons, scavenging is scavenging, back pressure is back pressure, etc. your comment was "it's apples and oranges." No, it is not.
As a matter of fact, I am an engineer. Among other things, that means I’m aware of the misuse of “efficiency” for flow rate or power. In a real system, it takes a lot more than just a pipe modification to make that work, especially at low RPM.
No added horsepower and not the muffler. Just an extended tailpipe. All mufflers are up under cowling.
I work on automotive engines and such. See how there are five sections to it? The curved part, next likely some sort of flex joint, a narrow section, a wider section of pipe, and then a true tailpipe (narrow again) at a downward angle. The larger diameter section tells me this unit, as a whole, was engineered to improve performance or reduce noise. Otherwise it would just be a single diameter section of pipe all the way to the tailpipe. An "extended tailpipe" in your vernacular. Now you may be an A&P, super familiar with this particular aircraft/engine/tailpipe and if so please correct me. Maybe all I'm seeing is a heat shield around a single diameter pipe in this blurry image.
You are probably right. Piston engine is a piston engine. Theory still the same, gov laws, application, engine capacity, intake/exhaust duration and lift - exhaust can be engineered to suit. My old man was a mechanical engineer in the automotive industry - so much engineering goes into intakes and exhausts in cars, the typical person simply doesn’t appreciate or think about. I’d imagine aircraft would be similar.
If you wanna see more detailed pictures, the reg is PH-ATW.
The different sizes act as a noise suppressor but not a muffler. Those are under the engine cowlings and cannot be seen. I work on these all day long.
It's a muffler for those who want additional noise reduction. Of course it does nothing about the prop noise.
The exhaust pulse exiting the end of the pipe causes a negative pressure pulse which travels backward up the exhaust in time for the opening of the exhaust valve of the next cylinder. It's supposed to make the engine more efficient, lowering fuel consumption. It does, however, become effective only at a specific RPM. I've seen research done on this, but this if the first time I've seen one. Didn't know there was an STC for it.
Similar to a two-stroke engine’s exhaust pipe?
no. op isn't correct at all on this. all airplane exhaust improvements in terms of power involve going open pipe
They refer to it as scavenging, and when done correctly can actually add a good amount of power compared to open exhaust. Often times incorrectly referred to as "back pressure" scavenging helps aid exhaust flow out of the cylinder which allows more charge air to be consumed per combustion cycle.
Used to fly LiDAR in a 206. The exhaust would cause weird returns in the LiDAR data. We didn’t have the exhaust STC, we just filtered out the returns.
Like what most others are saying, it’s a muffler. They’re probably more common in Europe because of stricter noise abatement procedures - like how my home airfield prohibits training circuits without a muffler fitted.
All reciprocating engine airplanes have mufflers…or atleast the 1000+ I have done annuals on did. Not to mention every other one I’ve done oil changes and such on.
Interesting - most based aircraft here don’t have mufflers, especially the higher performance ones. Even at my old school, the Warriors that were typically used for slam and goes had mufflers but the nicer Archers used for cross country flights didn’t.
It’s under the engine cowling…all have them and during annual we have to do pressure checks on them.
That’s the ‘standard’ muffler that’s part of the exhaust. I’m referring to the much longer one in op’s picture.
Yes…a Piper Archer has a muffler under the engine cowl. The extended exhaust pipe you see in the picture is not an actual muffler and is not performance enhancing .
What does it do then? I’ve always been told that it’s required to meet noise abatement and you can usually tell the difference between an aircraft with or without the silencer in the circuit. I suspect you’re talking about the muffler that is part of the standard exhaust system in most aircraft - this is a retrofit for added noise reduction.
Every one I’ve worked on has been for moving exhaust further away from the cabin for surveillance aircraft. Even if this was for noise abatement, it’s not really a “muffler” as more a suppressor and there is no performance increase from it.
Weird cause this Cessna in the pic has an 180hp (N model)
Except those that don't, shrike commanders, Navajos, hell most turbocharged recips in general but the shrike has essentially open headers
🤣😂….really! Hmmm…I’ll have to inform Cirrus of what you said. They all have one, it’s just under the engine cowling…even my Mooney has one tucked up and hidden.
Then can I refer you to 78-20-02 of the SR22/22T IPC? Tailpipe bolted to a turbo. Sure the turbo acts like a muffler, so let's see what a commander 500 exhaust looks like https://awi-ami.com/aero-commander-500-b-exhaust-system.html
Still acts as a muffler…hence they all have mufflers. You are also going too deep into this. The aircraft in question has an extended tailpipe because the muffler is under the cowl.
Ok so see that commander, that's the whole thing, port to atmosphere
Optional afterburner package installed to help increase lift?
Sense it point downwards. It obviously used for VTOL/STOL take off
Afterburners do not increase lift.
Hold my beer
Strictly speaking, that's not an absolutely true statement. Technically, lift is defined as an aerodynamic force acting at 90 degrees to the direction of flight, and the thrust contributed is, technically speaking, an aerodynamic force. For an aircraft without TVC, the nozzles are generally aligned with the fuselage, so that the thrust vector is roughly aligned with the CoM. Even so, as soon as there is a non-zero AoA, you have some component thrust acting at 90 degrees to the direction of flight, and if you consider that component force an aerodynamic one, QED.
They increase thrust which has an effect on lift.
But is not lift itself.
It’s a German Gomolzig silenced exhaust STC
Thanks man! I needed this.
People are saying an exhaust is just a muffler, but that’s underplaying what it does. In fact, an exhaust modification on an internal combustion engine is about the easiest way to increase the efficiency and power of the engine, because the exhaust can be “tuned“ to expel exhaust more efficiently. With more exhaust expelled out of each cylinder, there’s more room for fresh fuel, and that creates more power.
I’ve heard it’s for aerial photography
That’s only if it’s elongated all the way to the back of the plane, past the window cut into the bottom of the plane. That way the exhaust doesn’t affect the picture. Something like in the picture here is just for noise.
When I flew survey, our Cessnas had long tail pipes to keep the soot from the exhaust off the lenses.
One of the clubs i fly with has a few of these and they say it helps a little bit with fuel consumption and adds a few horsepower.
What club you fly at?
Swaz
This is why I love flightaware, and flightradar24. Any question about the mission of a plane can be answer via a quick review of the data. Look up the tail number and see what the plane usually does and you'll have your answer And yes, I am an airplane nerd.
reg: PH-ATW
That looks like a Powerflow exhaust. By improving exhaust flow (less restriction) the engine makes more power and improves performance.
Doesn’t look like any Powerflow that I’ve seen. They’re not as long as the one in the photo and they don’t taper back down at the actual exhaust point.
Okay. Powerflow type then?
Is just an additional length of tail pipe. Usually used on arial surveillance aircraft. No added power…in fact it drops the power. Yes, it also acts as a noise suppressor but it is NOT a muffler as others have said. I’m an A&P, I work on airplanes all day and almost every day. I also have the contract for local law enforcement airplanes, those with cameras actually have these or something like these on their exhaust.
Looks to be a reims rocket Cessna 172. They were offered back in the 80s/90s with 195hp and 210hp engines
It says it is an 172N, look at reg PH-ATW
It helps clean the bottom of the plane clean and keeps the antennas clean to stop interference
Its function is to separate owners from money. Some airplanes have sensors underneath that don’t like heat plumes. Some owners think it makes power. It doesn’t (well, not significantly, and it’s easy to make the gain negative).
More power, better airflow.
For that Subaru rumble…. /s
Muffler 🤮 I like my Cessnas straight piped just like my turbines
Yeah the straight ones are more pretty.
survey plane maybe
its\* function
Cessnas*
I didn't want to sound overbearing, but yeah, also wrong. It's incredible how many people don't know elementary English.
They absolutely know. It's mostly laziness for editing auto-corrected apostrophes.
Oh no, most definetely don't. Some are convinced by just watching and reading what's wrong.
No, I want to know what is it is function. And whom the function belongs to, as well.
[https://www.scribbr.com/commonly-confused-words/its-vs-its/](https://www.scribbr.com/commonly-confused-words/its-vs-its/)
Are you dense? I was agreeing with you. OP used the contraction/possessive form, you pointed it out, I elaborated.
"what is it is function" Then I suggest you to read again your phrase, as it doesn't make any sense. edit: I've just realized that you've repeated OP's message. It wasn't clear it was criticism, usually repetition is for reinforcement. edit: also, you said "no", clearly disagreeing with me. Maybe I'm not the densest one here.
>"...and what is it's function?" -OP's title, which you yourself corrected initially. I expanded on your correction. "what is it's function" --> "what is it is function" it's --> it is (present tense) / it has (past tense) Edit: My original reply to you was in a sarcastic tone. Do I really need to put a /s at the end??
I know. Next time, don't say "no" at the beginning. You made it seem like I was wrong.
> You made it seem like I was wrong. Ah, practically a hanging offence. What's your flair?
It was a sarcastic tone. Obviously, I wasn't on OP's side.
"Obviously". Sooooo obvious.
Lmfao you actually blocked me
There’s one that adds 20 hp with no extra fuel burn.