Why it can sometimes get alarmingly quiet onboard

Question: I live in Orange County, Calif., and use John Wayne Airport (SNA) as my primary airport. Noiseabatement procedures require a rapid climb out with reduced power, which results in an alarming reduction of cabin noise. Which other airports require these departure tactics? Also, what does it mean to “spool” the engines?

— Drake, Irvine, Calif. Answer:

I have flown the SNA noise-abatement procedure many times. If the passengers are briefed before takeoff, the noise reduction when the thrust is reduced is not so concerning. SNA is the most widely known for its noise-abatement requirements, but many others such as New York LaGuardia require immediate turns after takeoff. Many of the larger airports have noise-abatement requirements.

“Spool” is a term that refers to the acceleration time a jet engine requires. Jet engines, unlike automobile engines, require several seconds to accelerate from idle to high thrust.

Q: Why do pilots throttle up when landing?

— Goran Jelenic, California

A:

As a jet descends toward the runway, the pilot increases the power to maintain a specific descent rate (usually around 700 feet per minute). Jet engines require time to accelerate, so the increase in thrust (known as spooling up) improves the ability to go around should it be necessary.

Jet engines (U.S.-certified) can require up to eight seconds to accelerate from idle to maximum thrust. That can be a long time; having the engines already accelerated helps provide needed thrust quickly in the event it is needed to abort a landing.