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Noise Abatement

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If you were flying a C172SP out of a noise sensitive field like KSNA in the States, how would you take-off as quietly as possible. Would you go for Best-Angle-of-Climb or Best-Rate-of-Climb, or would you not bother in a 172? Obviously you would do it at full throttle. I assume the difference is that one gets you highest in the shortest horizontal distance, whereas the other gets you highest in the shortest possible time, is this correct, and if so which is better for noise? Presumably you would do a no flap landing (for minimum throttle settings), or would you not bother about this as well? Regards HK

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Henry,Not all airports have noise Abatement procedures. The ones that do, usually will have a sign at the runup area describing the particular procedure for that airport. Also, the noise abatement procedure is usually list in the airport facilities directory (AFD). Anyhow, alot of it is common sense and the procedure will be very visible. You just want to be as quiet as possible. Full power will obviously be used for safety. Best angle of climb should be used to provide the quickest accent possible for the given aircraft. Noise abatement procedures usually will not define speeds our power setting. The precures will usually dictate departure route and altitudes. This provides local residential houses near airports with minimum noise pollution. In some cases FAA officials actualy are onsite, airports without towers, and will write up a violation of the procedure if it is not followed correctly. This violation will be on your pilots license and will have some kind of action. Nothing drastic, but they may require you to have instructor training on the procedure or do it with a FAA DE (Designated Examiner) or possible with someone from the local FAA FSDO (Flight Standards Distict Office).Hope this help..CB :-wave

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Thanks CB,You have cleared up something that was bothering me with the John Wayne Noise brochure for GA pilots, available at www.ocair.com . I couldn't understand why the pattern altitude is so low (just under 900 feet) if it is so noise sensitive, as a higher approach/steep descent rate with flaps would appear to be the quietest way to land. They recommend minimum flap approach/landings as well, to reduce power settings.But on the brochure they are very particular about departure and arrival routes into and out of KSNA. It would seem that the horizontal flight path is their primary concern for noise complaints (ie to avoid built-up areas around the airport).Thanks for your help. It sounds pretty complicated. Bankstown Sydney is alot simpler - providing you don't bump into somebody on finals (We just had a fatal at YSBK this week).HK

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I fly out of KMOD and we have noise abatement procedures which require a straight out climb to 600 feet AGL prior to making a turn. The rationale is that we keep the noise over the folks that are in the corridor under the takeoff pathway. We always use full power for takeoff.For approaches we always follow the AOM procedures that is full flaps because you can come down offthe perch at a steeper angle at idle speed. Its noisier to drag it in with power on in a low approach.RegardsTony

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Oh....I forgot...the most annoying thing about props are that at high RPM....takeoffs the prop tips tend to go supersonic...and make that really annoying sound check it out sometime when you are plane watching not audible from the cockpit!!! Trivia is always fun!!! I currently fly Cherokee and Traumahawk.RegardsTony

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tascasoRN,I noticed that you stated the AOM calls for a full flap no power approach. This is fairly unsafe. All airlines major and/or regional require what is called a "stabalized approach", the aircraft must be stabalized in order to proceed with the final approach. A Stabilized approach is defined as follows:Appropriate altitudeAppropriate airspeed Appropriate power settingON the localizer and glideslopeetc.The point being all airline proceedures require a "POWER ON" approach. Never is a transport category aircraft 1000 feet about the ground with out power. The only time power is removed substantialy or completely is in the flare when landing is guarenteed. The reason the power is always on in an approach is, anything can happen. You pay encounter wake turbulence, a microburst, wave front (wind), wind shear, etc. Power already being in saves several crutial seconds for the time it takes to physicaly apply the power and for the engine to produce the power. I was doing an intrument approach into Prescott,AZ about a year ago in instrument conditions. I was on an instrument proficeny check with a CFII in a piper arrow. Anyhow the approach consisted of a clockwise DME arc, procedure turn, followed by and ILS. About 2 miles out on the ILS needles pegged in a cross of course, we hit wind shear. My airspeed droped INSTANTANEOUSLY from 100 kts to 55 kts and the stall warning horn was on. My power was set at 2,200 RPM of the max 2,500 RPM. We were approximetly 1,200' AGL when it occured. Full power was applied immediately and flaps were brought up one stage at a time. It took us about 20 seconds to get above 65 kts, and we were about 800' AGL before we were able to reverse our decent. The missed approach procedure was immedietly followed. He requested a holding pattern for 15 minutes to allow the adrenahlin decrease a little before trying the approach again. The next approach went well and was uneventful. Very close call, i prefer the uneventful approaches. Anyhow, more of the story ALWAYS keep power in on an approach regardless of the noise procedure. You are the final authority to the safety of the aircrafts operation. If you look in the NTSB accident database you will find many accidents relating to low powers setting. The aircraft can get into a stall, spin, cross-controled stall in a HEARTBEAT. The added protection will save your life. Anyhow, more of the story ALWAYS keep power in on an approach regardless of the noise procedure. You are the final authority to the safety of the aircrafts operation, FAR definition of PIC. (not exactly for my critics)Hope this was insightfulYours Truly,CB :-wave

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As has been mentioned, most airports have specific noise abatement procedures that are desgined to create the smallest noise footprint. These procedures should always be followed, assuming they're practical for you to apply. (Practical meaning safe, not convenient) For example, at my home airport, 4B8 (RobertsonField, Plainville, CT) there are signs at the runup areas telling us to turn our aircraft to a heading of 060 prior to applying power on the runup. This directs the noise out over an industrial complex rather than a neighborhood. On takeoff we are then directed to climb straight out to pattern altitude before turning crosswind or on course, this also minimizes time spent over a residential area. If you fly about 10 miles east to Hartford- Brainard, the tower there will direct you to fly a right hand pattern for runway 02 so as to avoid noise impact. (Runway 20 opeartes with standard left hand patterns.)The important thing to remember is that safety comes first. While there is usually no reason not to comply with such procedures as straight out climbs, turns to a heading or right hand traffic patterns, altering your appraoch or departure checklists so as to reduce noise can be quite dangerous. One poster spoke of his personal encounter with windshear. Other problems such as engine failure, carb ice, go arounds, stalls, and many others can occur as a result of deviating from normal procedures. In most GA aircraft (exluding turbine aircraft) you're not going to produce a substantial ammount of noise anyhow. As a pilot your first priority is safety, not appeasing the people who live off the runway's end. Besides, everyone should enjoy airplane noise! I'd kill to live next to an airport!-Rob

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I feel the same way about aircraft noise. I am always running outside to get a view whenever a plane goes over the house.I am still puzzled though, by the John Wayne noise brochure refering to minimum flap settings for takeoff - as I would have thought that even large jets like a 737 can achieve higher climb rates with more flaps than without? The C172SP seems to be able to. High flap settings in a circuit would obviously result in a higher power setting, but for take-off and landings I am not so sure that this is so undesirable - since I would have thought that a high climb rate/descent rate would be desirable?Thanks for the information about noise everyone. It seems like an issue that is becoming more and more important now.HK

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