Downunderflyer From Australia, joined Feb 2007, 15 posts, RR: 0 Posted (6 years 1 month 3 weeks 1 day ago) and read 9273 times:
Jumbos in fuel-saving trial
Big passenger jets are set to glide into Auckland International Airport from next month in a trial to save fuel and reduce air pollution.
Airways New Zealand said it had been working with Air New Zealand and Qantas for jumbo jets to reduce fuel use and emissions as the aircraft came into land.
The procedure was safe and flights into Auckland would be spaced to allow a glide descent into the airport from their top of descent point, Airways New Zealand main trunk manager Lew Jenkins said.
"These glide descent profiles will be flown with the aircraft engines set at idle, thereby significantly reducing fuel burn and emissions," he said.
The trial is to establish what the actual fuel burn was for an arriving flight and to gauge the potential fuel savings and associated emission reductions.
"This is a perfectly safe procedure, and other flights will be controlled by Airways New Zealand's air traffic controllers to remain clear of the trial flight paths," he said.
He said all commercial airlines wanted to be safe but they also needed to be profitable, fuel efficient, and environmentally friendly.
"A key component in this equation is fuel. The airlines have plenty of detail on how their aircraft need to fly in order to burn the minimum amount of fuel, especially on the arrival segment, but traditionally this has been balanced by an air traffic control imperative, driven primarily by on-time performance and runway capacity."
He said that had meant that the way an aircraft needed to fly to use minimum fuel was often at odds with requirements to arrive on time or to ensure best runway utilisation.
He said Auckland was chosen for the trial because it had more traffic than other airports.
The trial would target Air New Zealand and Qantas 747 Jumbo jets which typically arrived when other traffic was light, meaning minimum disruption to other aircraft.
CBPhoto From United States of America, joined Dec 2003, 1508 posts, RR: 6 Reply 1, posted (6 years 1 month 3 weeks 23 hours ago) and read 9214 times:
I see one very big problem with this!! Suppose you need to Go Around on very short final, by the time you push the throttles to full, and the engines spool up you will already be on the ground, and could cause a big problem or accident. On a normal approach (with engines operating normally) you would usually keep the engines at a pretty high RPM, for an increased response time should more power or a go around be needed. As great as an idea this is, this isn't the shuttle using only one runway and it being the only traffic in the airspace, we are talking about a 747 landing at a busy international airport.
Flyboy_se From Switzerland, joined Feb 2000, 745 posts, RR: 6 Reply 2, posted (6 years 1 month 3 weeks 23 hours ago) and read 9198 times:
Well the idea comes from SAS and they call it Green Approaches. They have been doing it for some time now and is proven to be very succesfull.Hence the interests from other airlines.
777DEN From United States of America, joined Dec 2006, 124 posts, RR: 0 Reply 3, posted (6 years 1 month 3 weeks 20 hours ago) and read 8959 times:
the idea is engines at idle from cruise till final approach, once the flaps are out you have the spool up the engines. This is what the FAA is working on with UAL at SFO in " Tailored Approaches"
Revelation From United States of America, joined Feb 2005, 10471 posts, RR: 20 Reply 4, posted (6 years 1 month 3 weeks 20 hours ago) and read 8884 times:
Quoting CBPhoto (Reply 1): I see one very big problem with this!! Suppose you need to Go Around on very short final, by the time you push the throttles to full, and the engines spool up you will already be on the ground, and could cause a big problem or accident. On a normal approach (with engines operating normally) you would usually keep the engines at a pretty high RPM, for an increased response time should more power or a go around be needed. As great as an idea this is, this isn't the shuttle using only one runway and it being the only traffic in the airspace, we are talking about a 747 landing at a busy international airport.
I'm certainly not an expert in how to operate a large jet transport, but nothing says they can't glide to pattern entry and then use the current procedures.
BA787 From United Kingdom, joined Jun 2006, 2596 posts, RR: 8 Reply 6, posted (6 years 1 month 3 weeks 20 hours ago) and read 8848 times:
Pretty good idea if it works.
But..
The better way to make air transport more environmentally friendly for the moment is to focus on ground movements, i.e. listen, mucyh as it wil pain them, to Sir Richard Branson, his team have come up with some good ideas, and I think they should be intorduced across the world.
Max777geek From Italy, joined Mar 2007, 538 posts, RR: 0 Reply 7, posted (6 years 1 month 3 weeks 20 hours ago) and read 8817 times:
Quoting CBPhoto (Reply 1): I see one very big problem with this!! Suppose you need to Go Around on very short final, by the time you push the throttles to full, and the engines spool up you will already be on the ground
As long as my experience in jumpseat and passenger seat rider, this is not corresponding to the truth.
Engines are almost at idle during landing, if Im not wrong it's a condition for the reverser to deploy,
while touch the ground during a go around may always occur. So, where's the problem ?
I hop you didn't get that the engines are turned off completely.
Chuchoteur From France, joined Sep 2006, 700 posts, RR: 0 Reply 9, posted (6 years 1 month 3 weeks 19 hours ago) and read 8710 times:
Quoting CBPhoto (Reply 1): I see one very big problem with this!! Suppose you need to Go Around on very short final, by the time you push the throttles to full, and the engines spool up you will already be on the ground, and could cause a big problem or accident. On a normal approach (with engines operating normally) you would usually keep the engines at a pretty high RPM, for an increased response time should more power or a go around be needed. As great as an idea this is, this isn't the shuttle using only one runway and it being the only traffic in the airspace, we are talking about a 747 landing at a busy international airport.
It is known as Continuous Descent Approach (CDA).
The concept is that you save fuel compared to an approach where you descend/stabilise/increase thrust than descend again etc.
From Top of descent to ILS intercept you are at flight idle, obviously spooling up the engines when you drop the gears and the flaps prior to final approach.
It's pretty much like your car, if you are constantly changing your throttle setting, you will be burning more than just maintaining one smooth and constant setting.
Also, you make less noise, as engine pitch variations can be a nuisance for residents on the approach.
The problem you have is that today, if an ATC tells you to maintain altitude etc, you have to apply power, negating the benefits of a CDA.
Auckland are basically giving instructions to ATC to facilitate CDA's and wherever possible try not to instruct an aircraft to re-apply power.
Theginge From United Kingdom, joined Oct 2006, 1110 posts, RR: 0 Reply 10, posted (6 years 1 month 3 weeks 19 hours ago) and read 8688 times:
They are doing continuous descent approaches into Heathrow for some arrivals in the early hours of the morning. . The aircraft do not glide all the way to the runway as once they are established on the ILS they will be using the normal descent profile into LHR.
EI321 From Iraq, joined Jul 2009, 0 posts, RR: 0 Reply 11, posted (6 years 1 month 3 weeks 19 hours ago) and read 8667 times:
Quoting CBPhoto (Reply 1): I see one very big problem with this!! Suppose you need to Go Around on very short final, by the time you push the throttles to full, and the engines spool up you will already be on the ground, and could cause a big problem or accident
Perhaps they will set the engines at normal landing power just before landing
Airfoilsguy From , joined Dec 1969, posts, RR: Reply 13, posted (6 years 1 month 3 weeks 19 hours ago) and read 8554 times:
Quoting Zeke (Reply 12): Idle descents is something we do all the time, part of the game is to out guess the controller to pick the top of descent.
True. Good pilots already do this. This study is more of a synchronizing of ATC with the pilots so that ATC clears the aircraft on the most favorable glide slope.
Now if they start shutting off engines during descent I can see a problem, but I don't think that will happen.
GeorgiaAME From United States of America, joined Aug 2005, 868 posts, RR: 6 Reply 14, posted (6 years 1 month 3 weeks 19 hours ago) and read 8519 times:
Do I get a partial refund on my $150 "fuel surcharge" if we do a glide approach?
"Trust, but verify!" An old Russian proverb, quoted often by a modern American hero
GeorgiaAME From United States of America, joined Aug 2005, 868 posts, RR: 6 Reply 16, posted (6 years 1 month 3 weeks 17 hours ago) and read 8252 times:
Given the circumstances, I think a free drink (or perhaps a double) might be in order.
"Trust, but verify!" An old Russian proverb, quoted often by a modern American hero
777ER From New Zealand, joined Dec 2003, 11318 posts, RR: 17 Reply 17, posted (6 years 1 month 3 weeks 11 hours ago) and read 7919 times:
AIRLINERS.NET CREW FORUM MODERATOR
This was discussed a few weeks back when it was first announced, its also talked about in New Zealand Aviation Thread Part 2, and was discussed in another thread, but forgot what that thread was called. Media reports latly have said that if the trial with the NZ and QF B744s is good then WLG could be used to trail B737s/A320s
Cbphoto From United States of America, joined Dec 2003, 1508 posts, RR: 6 Reply 18, posted (6 years 1 month 3 weeks 10 hours ago) and read 7764 times:
Alright.....I guess I miss understood the article, from what I thought it meant was that the experiment would be to cut the engines to idle from a certain altitude, and glide the aircraft all the way to touchdown, thus reducing noise all the way down to the ground. But after some explanations I see that they just want to use it for the decent and not all the way until the touchdown point, thats what I was getting at in the spool up time.
Quoting Max777geek (Reply 8): at the last moments before
touching the ground".
Yes, I understood what you meant, and yes at the very last moment before any landing the engines are close if not at idle. What I was getting at was during the last couple miles of the approach, with a large aircraft like the 747, that has large triple slotted flaps, and large heavy landing gear, you would either A. Need a very steep approach to not add any power, or B. need to add considerable amount of power to continue a normal approach to landing. Part of the reason that the flaps create so much drag, is to run the turbines at a higher RPM setting, where the engine is more responsive to throttle inputs, and if a go-around is needed, then there is a less spool up time needed to get max power out of the engines. Thats what I was getting at, but it has all been cleared up now....
Jafa39 From , joined Dec 1969, posts, RR: Reply 19, posted (6 years 1 month 3 weeks 9 hours ago) and read 7451 times:
My understanding is that this is basically what occurs anyway, the difference being that the approach will no longer be interuppted by ATC to allow smaller a/c to land.
I would have thought that marine rules already applied (big stuff has right of way) but it is not the case, holding patterns and levellling off do occur in jumbo descents because the descent is long and slow.
So now the minnows will be the one's getting out of the way....does the extra fuel burn caused by smaller a/c doing holding patterns and other manouvers outweigh the "jumbo savings" I wonder.
Not wanting to be critical of the CAA or ANZ here but it seems to me that most "green measures" are outwieghed by other factors (such as the extra emissions caused by generating the electricity need to charge electric cars or manufacture hydrogen)
Anybody in a position to comment on the fuel saving/loss issue?
Airfoilsguy From , joined Dec 1969, posts, RR: Reply 21, posted (6 years 1 month 3 weeks 8 hours ago) and read 6582 times:
Quoting Jafa39 (Reply 19): Not wanting to be critical of the CAA or ANZ here but it seems to me that most "green measures" are outwieghed by other factors (such as the extra emissions caused by generating the electricity need to charge electric cars or manufacture hydrogen)
I wounder how many Cessna's on hold would equal one 747 on hold. I bet its a lot.
Chuchoteur From France, joined Sep 2006, 700 posts, RR: 0 Reply 24, posted (6 years 1 month 3 weeks ago) and read 2543 times:
Quoting Jafa39 (Reply 19): So now the minnows will be the one's getting out of the way....does the extra fuel burn caused by smaller a/c doing holding patterns and other manouvers outweigh the "jumbo savings" I wonder.
For a widebody aircraft, CDA benefits are generally around 200kgs of fuel saved I believe. Or 630kgs of CO2 for the nevironmentally minded. (These figures obviously vary depending on individual aircraft performance, but it gives you an idea!).
In my TB20, I'd have to be stacking for a long time to burn through that quantity of fuel...
Quoting Kaddyuk (Reply 23): I'm guessing this is the same as Continuous Descent Approach which has been in Trial at LHR for quite some time now...
Indeed
:o)
25 Cobra27: Considering that 747 burn around 2 tonnes of fuel yust for taxying I d0n't think we will not start to conserve fuel yet. Maybe some time in the future
26 Max777geek: this is impossible because ( I think ) the idle trust may allow an acceptable descent rate for a landing, not possible with engines totally turned of
27 9V-SPJ: Haha, great to see that some our our research here at GT made it onto airliners.net! Yes, what has been described above is a CDA. With regards to the
28 Zkpilot: as said by 777DEN below, but it wouldn't be a glide finals approach, the aircraft would glide onto finals and then resume normal approach with engine
29 Baroque: This seems like a development of "M**** overdrive" a profile/gear well known in cars.
30 Jafa39: True, but what about 737's A320's and ATR's???
31 Analog: No, you'll have to pay an extra $10 "Glide Approach Development surcharge".
32 COSPN: If they really cared about the enviroment they would go all twin like CO
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