Off the throttle......On the throttle

[scottcolbath]

I hear it all the time here with the windows open now. Everything coming into Sky Harbor seems to put the brakes on right over my house, then crank it back up again. I'm not sure why they just don't turn it down to just the right spot, rather than playing with the throttle, but I'm not a pilot, and I don't play one on TV. I enjoy the music.

S.C.

[Joe Copalman]

Adjusting speed to maintain separation?  Noise abatement regs? 

[Paul Dumm]

Throttles control altitude in the aviation world not speed. steeping down to a altitude shelf then adding throttle to maintain it.

[Dave S.]

Could also be that they're adding in some drag (i.e. flaps or lowering the landing gear) and need additional thrust to maintain their approach speed.

[Jeff D. Welker]

It may be the new flux capacitor APU that Scott "DeLorean" Youmans designed. While highly efficient, it does emit a loud flatulent-like sound periodically on approach.

[Scott Youmans]

In regard to to the flatulent-like sound of the new flux capacitor APU.  This unique sound was achieved only after years of R&D.  Microphones were placed throughout the engineering office each Tuesday afternoon after Navy Bean soup (a long standing tradition) was served in the cafeteria.  The sound profile of the resulting flatulence was then duplicated by a computer modeled exhaust duct constructed of high-temperature polymeres that mimic a specific part of the human anatomy.  The goal was to lend an "air" of humor to airline travel, thus relieving stress levels among the flying public.  Due to nature of the flux capacitor power generation system there is no foul smelling exhaust, the exhaust being only cooling air.

[bilwor]

You Nailed it Scott, well done

[scottcolbath]

Throttles control altitude in the aviation world not speed. steeping down to a altitude shelf then adding throttle to maintain it.

I need this explained.

S.C.

[Jay Beckman]

Throttles control altitude in the aviation world not speed. steeping down to a altitude shelf then adding throttle to maintain it.

I need this explained.

S.C.

You don't "point the nose down" to descend in a commercial jet.  You retard the power and trim to hit a specific number of feet per minute at a specific distance to cross waypoints as instructed by ATC.  Once you reach your target altitude, you have to come back in with power and re-trim to hold that altitude.  Sounds like you live near a descent "catch point" and you're hearing the power come back up.  I hear similar in Chandler from jets on the downwind for the south side when PHX is landing jets from the west.

[BillOz]

Maybe like me, the Pilot just likes to hear the engines, to be sure they are still running, so I floor it every now and then, just because I like the sound.
Actually, it's what Paul and Jay explained.

P.S. Glad I never visit Honeywell for Tuesday lunch.

[scottcolbath]

You don't "point the nose down" to descend in a commercial jet.

Right. That sort of thing is just for Fat Albert. 

You retard the power and trim to hit a specific number of feet per minute at a specific distance to cross waypoints as instructed by ATC.  Once you reach your target altitude, you have to come back in with power and re-trim to hold that altitude.  Sounds like you live near a descent "catch point" and you're hearing the power come back up.  I hear similar in Chandler from jets on the downwind for the south side when PHX is landing jets from the west.

Interesting. Thanks. And yes, I'm apparently directly below a catch point for Sky Harbor, and I also get traffic approaching DVT at lower altitudes.

S.C.

[scottcolbath]

P.S. Glad I never visit Honeywell for Tuesday lunch.

Is this some pilot insider joke? I don't get it.

S.C.

[Mike Margolis]

It's all about the flow of both civilian and military traffic, the way the airspace is divided up for departures and arrivals, areas to avoid - some are more noise sensitive than others, and how the local and regional ATC controllers like to control traffic. Given our druthers, we would make one power reduction at altitude to initiate our decent and not touch the throttles again until the need arises to spool the engines up for landing - in the event of a go around - the lag from idle feels like a lifetime. LAX and others are getting pretty good at "programmed rate descents" where we and/or the FMS/VNAV can make small adjustments to hit certain sensible "gates" along the way vs. the idle-to-cruise power "dive-and-drive" level off you're hearing over your head. A smooth decent is much more fuel efficient, more comfortable for the passengers and more noise compliant than the hurry up to get down only to drone along at some seemingly arbitrary step-down altitude. That said, there are likely other aircraft crossing over a little higher, or maybe lower, which demands the sort of stacking effect. You may notice late at night it might be a little better since the different altitudes are no longer "reserved" for others and the flow into PHX can be smoother. Or, sometimes controllers stick with the step-down altitudes 24/7.
~ My favorite decent of all time was returning to Willie short on gas - of course, we were always short on gas in the T-38. I did the math and asked ABQ Center to let me stay higher than normal for longer than normal to get closer to the field while burning less gas. At exactly the right point - that was previously calculated (taking into account the winds aloft of course), I pulled the power back to idle at 39,000 feet and the T-38 became a glider. Well, a brick with tiny wings sort of glider, but a glider none-the-less. The next time I touched the throttles was on very short final to 30C just to make sure the engines were still working. It was smooth, easy (once the math was done), quiet, and extremely fuel efficient. But there was nobody else in the airspace on that Sunday afternoon. Just the humble opinion and perspective of this international 757/767 pilot.