noise reduction take-off

[crazyaviator]

There is a C-185 that takes off in the morning at our small airport in the middle of town. I'm ok with its noise but i am a little concerned with others wanting to shut the airport down. We all know airlines do part power take-offs for noise, efficiency, wear and tear etc.
The runway is 3200 feet, downsloping. The A/C takes off with only 1 person (light)
I have never tried this but what if the owner turned out the prop control to a specific point, applied full throttle and adjusted prop control to stay just below sonic range and proceeded to take-off ? What is the legal/CARS issues with GA part power takeoff? Insurance? What is the power loss at this setting?

[co-joe]

If it has the 2 blade prop that is one loud airplane! The 3 blade-er is way way less piercing of a noise, but doesn't have the STOL performance I believe. That 2 bladed wind shovel, I believe the prop tips are supersonic. It vibrates windows, loosens floor boards, and you feel it in your teeth!

[andy_mtl]

Well remember :
By lowering your rpm even tho you get max manifold wich should be 28.5 29 inches on a standard day on a non turbo charged engine, you will not be achieving take off power. And in my opinion a de rated take off in a piston engine is simply simply a no go.
Also
Best acceleration is achieve with the finer pitch on your prop. By lowering your rpm your prop now is in a coarse angle too.

So you have two things going against you.

Will the 182 take off .... yes
Is it good airmanship. .... not really.

Andy

[SuperchargedRS]

I've heard of the AK prop governor, where you put a clothes in the prop control knob shaft.

I've never done this in my 185 (IO520 with the three blade), I also land it on the river by my house, never had a complaint.

Personally, yeah the 2 blade is loud, but it's a airport, don't like airport noise, don't live by a airport, there was a reason your house wasn't as expensive as it could have been.

I wouldn't reduce my takeof power for the sake of "noise pollution" LMAO!

[Rockie]

We all know airlines do part power take-offs for noise, efficiency, wear and tear etc.

The primary reason jet operators use reduced thrust takeoffs is because it greatly extends the life of the engine thereby reducing cost, and it is not done arbitrarily. It is a manufacturer approved procedure and the takeoff thrust is calculated for each specific runway, runway condition and current environmental conditions to permit a reduced power setting yet still meet all the required performance criteria from brake release to 1500 feet with an engine loss at V1.

It's been a very long time since I've flown a 185 but I don't remember a procedure in the POH regarding reduced power takeoffs. If something were to go wrong while operating the aircraft contrary to the POH recommendations that would put the pilot in a very bad position.

[SuperchargedRS]

We all know airlines do part power take-offs for noise, efficiency, wear and tear etc.

The primary reason jet operators use reduced thrust takeoffs is because it greatly extends the life of the engine thereby reducing cost, and it is not done arbitrarily. It is a manufacturer approved procedure and the takeoff thrust is calculated for each specific runway, runway condition and current environmental conditions to permit a reduced power setting yet still meet all the required performance criteria from brake release to 1500 feet with an engine loss at V1.

It's been a very long time since I've flown a 185 but I don't remember a procedure in the POH regarding reduced power takeoffs. If something were to go wrong while operating the aircraft contrary to the POH recommendations that would put the pilot in a very bad position.

Agreed 90%

To the 10%, no one would ever know, doubt anyone flying a 185 would be dumb enough to admit to operating outside of the POH.

[springlocked]

We all know airlines do part power take-offs for noise

-- not really -- reduced thrust is for engine over haul costs -- noise is reduced by t/o profile -- reduced thrust is optional -- noise abatement procedures at airport that call for it are not and not applicable to propeller driven a/c

[Redneck_pilot86]

The BN2 POH (if you can call it that) has a section regarding reduced noise takeoff. I've never done it, but if I remember correctly it requires a full power run up at the threshold, reducing prop rpm to 2500, then releasing brakes. I operate almost exclusively off of gravel, so it's a no go, but I do reduce power as soon as practical after lift off.

[crazyaviator]

If the Pilot felt he/she needed more thrust, they could move the prop control full forward,,,,, If a pilot is taking off of a 1500 ft strip at gross,,, their profile ( point of becoming airborne, climb out profile ) may be the same or worse than a reduced power take-off on a 4000 ft strip with 1 person and half fuel aboard,,,, which is legal ? Both? Is the loaded TO from a small strip foolish compared to 90% power take-off from a 10000 ft runway or the other way around ,,,,mindset? brainwashing ?? code?

[crazyaviator]

I have experienced pilots reduce throttle IMMEDIATELY after take-off ( to set TO thrust/rpm etc) meanwhile, the A/C is wallowing and the pilot is not concentrating on the climb rate!! What is more wise,,,, do that , OR leave the frigging engine alone till you have positive climb, cleared obstacles AND are in a position to glide to a landing . ( remember, touching the throttle etc INCREASES risks at low altitude) As an option, i would rather set TO rpm in a C-185 for a quiet take-off than to do the above mentioned procedure !!!
There are MANY de-rated, quiet engines out there that are quite happy to stay at full power till 500 feet above rwy altitude

[Rockie]

Correct me if I'm wrong please because it's been a while, but POH's contain takeoff distance information which is based on full takeoff power. So if someone is taking off a 1500 foot strip when the POH says they can't that's bad. Arbitrarily reducing power with no guidance on how to do it, or whether or not it is the correct amount given the runway and conditions puts you in test pilot territory.

Also bad.

[photofly]

On the other hand... take off at a DA of 4000' and presto hey - you have an arbitrary power reduction compared to sea level.

Lots of people - me included- dial back the rpm immediately from the yellow to the green rpm arc after takeoff to reduce the noise, without a significant power reduction. I don't really see the problem with starting the takeoff with the rpm thusly reduced, as long as you have the runway length to accelerate to a regular flying speed.

I would not make a power reduction by reducing the throttle though, because I want the extra extra rich mixture associated with a wide open throttle in at least some engines.

[PilotDAR]

I am strongly in favour of efforts to reduce noise percieved by those who might be sensitive on the ground, when approved information, or experience allows the pilot to be confident about safety in doing so. I always reduce power ASAP after breaking ground at home in the amphib, to reduce noise - I respect the privilege of complaint free flying at home, so I intend to do my part to earn that with my neighbours on an ongoing basis.

In a few cases, the same propeller is approved on the same engine on the same plane, at different maximum RPM - solely for noise. I have actually done the TC witnessed noise testing to validate this data, and it is correct. 39 overflights in the 182 amphib at varying power settings during a one morning test. The test procedure was suggested to me by EASA noise engineers in Germany and approved by TC. Interestingly, during that testing, I observed that all other things being precisely equal, the difference in crossing altitude in a best rate climb, 8200 feet from the brake release point, was less than 50 feet between 2700 RPM and 2500 RPM. Pilot technique will create more variation than that! The reduction in RPM was not a big deal afterall.

As Crazyaviator correctly states, if you feel comfortable doing a partial power takeoff, and thereafter feel the need to have more power, push the engine controls forward. There are some times when a STOL technique is needed, but really, not that often for most of us. There are foolhardy pilots who drag a plane an airplane up at best angle speeds for no good reason, and that as more risky behavior, when not required, than a partial power takeoff.

I delight in challenging myself by doing partial power water takeoffs when the lake size permits, just to maintain my skills of finessing the plane off rather than thrusting it off with poor technique. I can get off the water and climb away slowly at 19'' MP. I purposefully turn away from overflying built up areas when I can, or reduce power as I go over, just to reduce my noise footprint.

Some of our BC contributors will know that some BC harbours forbid two blade prop equipped floatplanes. So spend the money on a three blade prop, and tolerate possible reduced performance, because those who went before failed to appease the noise sensitive built up areas. Like it or not, we all have to get along, it's worth the effort. We in Canada are highly privileged to fly as freely as we do. The more we thumb our collective noses at those who don't fly, the more they will pick away at our privileges.

If you are actually using the performance tables of your flight manual to determine that you need full power, then use full power. If you are holding at the threshold of twice the runway length that your experience tells that you need, be a good person, and use a lesser RPM for takeoff if the area could be noise sensitive, if you feel confident to fly that way. I do.

[Rockie]

PilotDar

Respecting your experience and knowledge in these matters, how do you delineate that advice between pilots with the knowledge and experience (overall and aircraft specific) and those that don't?

[crazyaviator]

Photofly and PilotDar, EXCELLENT posts which i fully agree with,,,, This thread is going in a wise and positive direction

[PilotDAR]

how do you delineate that advice between pilots with the knowledge and experience (overall and aircraft specific) and those that don't?

If your experience tells you to use full RPM for departure, then you should do that. If your knowledge and experience tells you that you can operate in given circumstances at lower RPM (knowing that full RPM is still available upon command), then do that.

I have no criticism for a pilot who safely operates their aircraft with consideration to the general public too.

[Rockie]

What about a pilot who lacks the experience and doesn't know when reducing power is inappropriate or by how much, and does it anyway because he read here that he could?

[Chris M]

Be smart about it. Take the plane to an 8000' runway and do a bunch of stop and go takeoffs, backing off the prop a little each time and noting the change in performance. Bonus points for having an observer on the ground tell you if/when there is a noticeable reduction in noise. After some practice if you feel the plane can perform comfortably at your home field head on back and use your modified settings. Again, be smart about aircraft loading and configuration. If you only practiced with one person on board and half fuel, don't go using reduced power settings when loaded to gross for the first time.

[photofly]

What about a pilot who lacks the experience and doesn't know when reducing power is inappropriate or by how much, and does it anyway because he read here that he could?

I am so bored by the "someone read that they should try shaving with their garden shears and accidentally cut their head off and it's all the interweb's fault" theme.

If dumb people want to do dumb stuff because someone else wrote that it would just fine, then too bad: they deserve to die.

[PilotDAR]

Easy Photofly, we don't want people dying in planes, it makes aviation look bad!

It's wise to be cautious and inquisitive before doing something in a plane which is a little different. When most of the GA fleet was built and certified, noise compliance was way down the list of considerations. In fairness to the public, it has come way up in importance, and if you think it's troublesome here, try flying in Europe!

As I said, I have done the testing in a 182 amphib (at 3350 gross weight, by the way) and the difference in altitude achieved between 2500 RPM and 2700 RPM was about 50 feet at around 500 feet up. That was averaged over 39 runs, so it's decent data. In most cases, the precision of the pilot's flying will be a greater altitude variation than that.

Remind yourselves that aircraft get certified because they have demonstrated compliance with takeoff and climb requirements. Read your flight manual, if the aircraft is marginal in any circumstances, the flight manual will say so (certain passages for certain Navajos come to mind). If you have chosen to carefully calculate performance from flight manual data because you felt you needed to, and the data shows that you're close, best make the noise, and use full power. But honestly, how often is your takeoff so close to the performance limits that "making it" is a concern?

Don't use anonymous information from the internet to form the basis of your decisions about flying. But, consider using information on the internet to inspire you to learn and understand more from the authoritative sources of information.

In the mean time, I really consider the public perception of GA, so I can maintain the privilege to fly my planes as long as possible. In a world of noise and pollutant emission concerns for everything, it's only a matter of time before the general public turns its sights on us. Once all the cars are electric, and other forms of recreational equipment is environmentally friendly, GA is in for big uphill battles! I remarked to my 12 year old daughter the other day that she should enjoy flying around with me now, because when she is my age, just flying around for fun will be subject to society's ridicule for environmental excess. If you don't believe me, fly GA in Europe right now!

Let's make ourselves the least offensive as the public perceives us, okay?

[ScottS]

We have a new 180 owner that seems to keep it all to the firewall right up to his cruising altitude. I have been wanting to say something about reducing rpm at least once he gets over 1000 AGL. I live right near our airport and love the sound of aircraft, but it was even bothersome to me and my girlfriend actually swore "What the F*&% is that plane? That is brutal". I can only imagine what non pilots were thinking and we have gone down the road of residents trying to shut the airport down before.

[co-joe]

There is a C-185 that takes off in the morning at our small airport in the middle of town. I'm ok with its noise but i am a little concerned with others wanting to shut the airport down. We all know airlines do part power take-offs for noise, efficiency, wear and tear etc.
The runway is 3200 feet, downsloping. The A/C takes off with only 1 person (light)
I have never tried this but what if the owner turned out the prop control to a specific point, applied full throttle and adjusted prop control to stay just below sonic range and proceeded to take-off ? What is the legal/CARS issues with GA part power takeoff? Insurance? What is the power loss at this setting?

So in the OP's case, C-185, unknown number of blades, and a 3200' paved down hill dry runway, let's say average skill, what else do we need to know?

Crazy, what density altitude are we talking about here. It matters when we're talking reduced thrust take off. One pax.

Would you do a reduced thrust take off? I've never flown the 185 so can't give an educated comment.

[SuperchargedRS]

.....

[SuperchargedRS]

What about a pilot who lacks the experience and doesn't know when reducing power is inappropriate or by how much, and does it anyway because he read here that he could?

I am so bored by the "someone read that they should try shaving with their garden shears and accidentally cut their head off and it's all the interweb's fault" theme.

If dumb people want to do dumb stuff because someone else wrote that it would just fine, then too bad: they deserve to die.

Experience is a hard teacher because she gives the test first, the lesson afterwards.

But....we're talking a 185 here, don't know any schools who will just rent one to any dodo bird off the street, don't know any operators who will let a mental midget loose in one, and most people with the bank roll to buy a six figure bush airplane didn't get that type of money by taking chit the read on the internet as gospel.

We have a new 180 owner that seems to keep it all to the firewall right up to his cruising altitude. I have been wanting to say something about reducing rpm at least once he gets over 1000 AGL. I live right near our airport and love the sound of aircraft, but it was even bothersome to me and my girlfriend actually swore "What the F*&% is that plane? That is brutal". I can only imagine what non pilots were thinking and we have gone down the road of residents trying to shut the airport down before.

Not 100% sure about the 180, but we have a limit on full prop in the 185.

So in the OP's case, C-185, unknown number of blades, and a 3200' paved down hill dry runway, let's say average skill, what else do we need to know?

Crazy, what density altitude are we talking about here. It matters when we're talking reduced thrust take off. One pax.

Would you do a reduced thrust take off? I've never flown the 185 so can't give an educated comment.

Think this was all covered.

But here's a little snippet on what some folks do.

....The engine is the normal Continental IO-520D, rated at 300 hp for five minutes and 285 hp continuous. Tom, however, restricts his horsepower for increased engine longevity by keeping the rpm down on take off via what he calls an "Alaskan Prop Limiter"; that's a wooden clothes pin clipped on the prop control shaft that stops it at 2650 rpm, holding the power to 285 hp. I didn't ask if the clothes pin was STC'd.

Yes, in most cases a A185F will have no issue operating out of most strips at 285hp, but why would I? It's a airport, you're going to have airplane noise!

Full power on takeoff, clear of any obstacles I'll bring her back to 25 squared, if that bothers anyone they are free to call a realtor, rent a moving van and find a house that's not next to a airport.

[xsbank]

If you operate outside the Limitations or the procedures in the POH, you are illegal. If you have an accident or incident, your insurance will not cover you. If your boss asks you to operate a way that contradicts the manuals, get it in writing. Ass License Job.