FAA existing standards do not measure well Concentrated RNAV noise
The FAA NextGen Metroplex implementation programs have met with unexpected opposition. The FAA ATO management saw these local exercises as positive opportunities to reduce noise and reduce the aircraft consumption of fuel (reduction of CO2 emissions. Those macro impacts have been countered by micro problems, i.e. the greater precision of the air traffic routes have concentrated the noise corridors and thus the significant opposition.
What the DCA Airplane Noise Assessment Project did not have within its authority was to recommend that the FAA adopt a new metric to assess the concentrated impact of these NextGen routes.
Excerpts and Comments on the DC Department’ Noise Assessment Recommendations
The DC Government (its Department OF Energy & Environment) “initiated a study to investigate noise originating from Reagan National Airport (DCA) air traffic operations and to identify ways in which to minimize the noise effecting District residents in a manner acceptable to the Federal Aviation Administration (FAA) standards and criteria. The District’s ultimate goal is to assist FAA and the Metropolitan Washington Airports Authority (MWAA) in implementing the new Next Generation Air Transportation System (NextGen).
The result of this project would be specific recommendations to FAA and MWAA for changes in Air Traffic Control (ATC) procedures to minimize noise exposure and impact to District communities while not adversely affecting the FAA’s goals of air safety and promotion of air transportation.”
Comment- this statement of goals and objectives is perfectly articulated in that it recognizes that the difficulty of balancing of DC’s citizen’s noise impact against the FAA’s safety concern.
“The two year project concluded in September 2018 and the comprehensive report has been prepared. The DCA Airplane Noise Assessment project accomplished the following:
- Review of all published DCA approach and departure procedures, prior noise studies, previous noise measurement reports, noise complaint files, noise monitoring data and records.
- Modelling of past and current noise exposure from DCA operations over the District using FAA’s Aviation Environmental Design Tool (AEDT).
- Field monitoring and noise data analysis of aviation noise exposure at several locations in the District.
- Conducted sleep awakening analyses for District neighborhoods significantly affected by nighttime DCA flights.
- Assessed noise impact, per national standards for classroom disruption, at several schools in the District.
- Evaluated alternative ATC routes and modifications to existing routes.
- Conclusions and recommendations documented in a comprehensive assessment report.”
Comment– It is difficult to discern a big improvement from any of the alternative flight paths; because the NextGen’s precision makes them all too concentrated. Noise is a byproduct of powered flight; merely realigning the pattern from the old route to a new one just transfers the noise. Perhaps the new locus has fewer noise disruptions beneath it, but along the full length there likely will be incompatible uses.
The lesson of the Chicago ONCCs approach to sharing noise via a runway rotation program is that dispersing flights is preferred over isolating noise over the same populations. The big difference from pre Next Gen is the narrowing of the dispersion and concentrating the noise – the FAA loves it because the net effect shrinks the contour but the impacts to those beneath the acute path are not acceptable to the communities. The narrowing of dispersion hammers the same populations over and over within say 10 nm of the airport. Moving the flight procedure to pass it off to another community solves nothing. Rather than one departure corridor – define three and fan the departures. The three procedures could be on either edge and the middle of the 2010 flight track polygon and the difference on the ground would be noticed.
Rather than one departure corridor – utilize all three and alternate between them on departures. All communities benefit from the airport. It distributes the burden and the difference on the ground would be noticed.
Additionally is there an opportunity to define a departure procedure branching off to the East following the other river? The departure tracks from the OAPM give only a distant view but BWI is far enough away that may be possible and would likely be more efficient for traffic bound for the SE corridor.
The alternative to study North vs South flow appears to be most promising, but it also needs to include current patterns of use whether it is a function of prevailing winds or tower preference. The appropriate balance between North and South flow should be established considering wind conditions and balancing DNL impacts.
OAPM modeled lower use of North flow (based on actual radar data Table 5 above) than the wind data would predict. CSDA utilized (62.5% N/37.5%S) but did not elaborate how they determined that split.
If you look at the wind rose data May through August (when people are outdoors trying to enjoy summer) South winds prevail. Does the runway use follow this pattern? Or, are they just favoring North flow when they can?
DCA operations are steady (no summer peaks like most airports). But what this data does not tell you is time of day the winds are at speeds above 5kts – it may not coincide with peak ops of the airport and therefore may not drive a straight percentage of runway use as may be assumed.
Actual reported runway usage shows that North flow has increased since OAPM’s numbers above which were based on radar data.
The wind rose should be evaluated for percentage of time south flow is possible by hour of day and the # flight operations by hour of day and the airport should target N/S flow utilizations in their noise mitigation strategies accordingly.
Tampa is a good example of over utilization of North flow even when the wind data favors South flow.
- ~ 97% of flight operations take place on runway 1/19 – essentially making DCA a 1 runway operation
- ~ 65% of the runway 1/19 ops are departing runway 1 and 35% runway 19
- The other runways are too short for most of the aircraft operating in/out of DCA – especially heavy gross weight airplanes
- P56 is just north of DCA and it puts a noose around alternative departure procedures off runway 1 and east traffic (if it was used)
- Andrews AFB, home of AF-1,is east of DCA making east departures dicey.
- Potomac Tracon manages 4300 flights per day transitioning the DC area operating in/out of DCA, BWI and IAD as well as 8 GA and other small airports in the vicinity.
- Wind and weather are not the only factors driving rwy use at DCA – traffic in/out of BWI and IAD all must be coordinated and when 1 airport has an ops change in a runway it all has to be coordinated to ensure airplanes do not create conflicts on departures and arrivals.
- The noise impact for DC, MD and VA comunities on the north flow departure options is essentially the same for all.
It will be interesting to see how the FAA responds to the DOEE suggestions. The tone of the document and the care with which the alternatives are drafted. What may be most telling, as well as a most significant refinement of the FAA noise analysis, is whether the current methodology is amended to recognize the unusually concentrated impact of RNAV.
Coincidentally, but not directly relevant, recently two pictures of the airport were published:
And the Willard Hotel’s gingerbread recreation of the current Reagan National Airport facilities:
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