More Airports to Use Greener ‘Glide’ Approach to Landing -"(by having incoming planes turn off their engines"

https://www.scientificamerican.com ^ | February 1, 2023 | By Minho Kim, E&E News on

[RomanSoldier19]

Eleven more U.S. airports plan to adopt a new way of landing planes that reduces both emissions and noise — all by having incoming planes turn off their engines and glide down to the tarmac like a paraglider.

The Federal Aviation Administration announced Monday that planes heading to Orlando, Fla.; Kansas City, Mo.; Omaha, Neb.; Nebraska's Offutt Air Force Base; Reno, Nev.; and six airports in South Florida soon would make idle descents to runways. It's a method called “Optimized Profile Descent,” and more than 60 U.S. airports already have it in place.

[null and void]

Due to noise restrictions, aircraft departing John Wayne have a very steep climb as soon as they take off.

Then they cut power and more-or-less ballistically glide to the coast before powering back up.

That scares the crap out of the people who can’t be bothered to listen to the pilot’s pre-flight announcement of the program...

[Tom Tetroxide]

Turn off the engines and spool up the RAT just like the Gimli Glider.
https://en.wikipedia.org/wiki/Gimli_Glider

Air Transat Flight 236 (aka the Azores Glider) flew some 75 miles for the longest glide to an airport...over the Atlantic Ocean.
https://en.wikipedia.org/wiki/Air_Transat_Flight_236

Pitch, (no) power, and trim for best glide.

[Cinnamontea]

The approach does NOT involve turning off the engines. It involves setting them to idle. They’re still running and can be powered up if necessary.

Thank you for explaining that!

[The Antiyuppie]

“These enviro-whacko’s are just hell bent on getting everyone killed by every means possible. Eff them!!! “

Understand that this is actually the primary goal.

[Vaduz]

Clean up on runway #2

[momincombatboots]

Wind sheer with no power to correct… and that’s just one hazard. Surely they are just reducing power.. but then again how fast can you get it back when needed.

[steve86]

“Throttling engines back and “gliding” to “be greener” isn’t going to happen either since the amount of throttle needed is dependent on the altitude of the runway and thus the altitude of the plane that’s landing. The higher the altitude, the more power needed just to maintain lift and control.”

False.

[Hiddigeigei]

"The real title to the article, not the one shown here, does NOT include the parenthetic about “turning off” the engine."
True, but the first paragraph of the article does.

[steve86]

I think turbines generally have a 4 - 8 second spool-up time, but there may be exceptions. The FAA requires no more than 5 seconds to 95% power.

[KC Burke]

Thanks, finally a comment from a passenger aircraft pilot.

I have been on flights where a go-around had to be instituted on final approach — not fun but not the end of the world feeling either. Having the power that low will make it more iffy.

MCI in Kansas City is on a large flat plain well above the Missouri River valley. There are residential areas where a much lower approach, even at idle, will make home ownership very problematic.

I used to have a home that had been under the commercial flight path to the old downtown airport but I owned it after the commercial flights all moved to MCI. Once in a rare while we had a large plane still land downtown and when the old large prop planes came in they looked like they were level with my back patio door, LOL.

[TankerKC]

Where doe it say that they turn off their engines? Going to idle is not the same as shutting down.

[T.B. Yoits]

“Throttling engines back and “gliding” to “be greener” isn’t going to happen either since the amount of throttle needed is dependent on the altitude of the runway and thus the altitude of the plane that’s landing. The higher the altitude, the more power needed just to maintain lift and control.”

False.

False? Try dropping power before flaring at a high elevation airport. It gets real fun real fast. You need that power for lift and control of the aircraft.

On final, when you set your airspeed (lets say to 180 Knots Indicated Air Speed for a commercial jet), your engines are powered up higher if you're at 8,000 feet than if you were at 300 feet.

[TankerKC]

ah...I see it.

[cgbg]

“It is amazing this article got through editing.”

Affirmative action editor hiring has done its job.

[cgbg]

Years ago I used to fly in and out of John Wayne—it was terrifying to me—and the pilots calm explanation did nothing but get me even more panicked.

[steve86]

No, indicated airspeed corrects for all that.

Only if you have to maintain the same glideslope will more thrust be needed. The guideslopes in the ‘green” approach system are adjusted for that. Glideslope is steeper.

[GaryCrow]

This article is a classic example of why you should always take everything from the media with a grain of salt. Nobody is going to shut off engines and glide into the airport, that's just stupid. We're also not going to do the final approach at idle, you couldn't maintain the proper glideslope that way. What an optimum profile descent does is attempt to time the initial descent out of altitude where you can do an idle descent until you start configuring for the final approach (putting the flaps out and gear down). The point to start your descent can be approximated in most airliners by multiplying the altitude times 3, so if you're at 30,000' you'd start your initial descent at 90 miles. That changes depending upon winds so the flight management system (FMS) can calculate the point precisely, but the 3:1 rule will get you close.

At most airports the airspace is too busy to allow someone to do an uninterrupted descent out of altitude, they'll stop you to deconflict traffic so you end up doing a descent with multiple step downs. That's not very fuel efficient so they're trying to change routings and procedures to avoid all the level offs on the descent. That's a good thing. The approach is not going to be flown at idle so everyone panicking about spool up time can breathe. When configured for landing with flaps out and gear down there's a lot more drag on the airplane which requires the final approach to be flown using a mid range power setting. The typical glideslope is 3 degrees which equates to 300' of altitude loss per mile and a rate of descent of about 700 feet per minute in a typical airliner. If you pulled the power to idle while configured for landing you'd dramatically increase your rate of descent, you have to fly the final approach with a mid range power setting until you flare and reduce the power to idle before touchdown.

I'm an airline pilot and that's how it works. There's nothing remotely dangerous about an optimum profile descent, it's just timing the traffic coming into an airport so you're not constantly having to make adjustments for other traffic. Think of it as if a city timed all the stop lights on a major road so they continually changed green as you approached the next one, you'd never have to stop so you'd save gas instead of wasting time sitting at red lights.

That article has a lot of really dumb errors in it that obviously are causing panic over this for no reason.

[T.B. Yoits]

Glideslope is steeper.

Which increases airspeed unless they have more flaps, air brakes, or put it into a slip, not the things you want to do if you need power to adjust.

Airports will need longer runways to account for the increased risk of missing the touchdown zone due to the shorter window for adjustments in a steeper glideslope.

Elevation comes into play. There are already certain airlines that won't fly direct into high elevation airports such as Mexico City due to the runway distance needed for a high-elevation airport. They're not going to accept a steeper glideslope.

[steve86]

Agree

[RomanSoldier19]

sure

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