Downunderflyer
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Jumbos In Fuel-saving Trial - Glide Into Airport

Wed Apr 04, 2007 4:16 pm

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.

NZPA
 
cbphoto
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RE: Jumbos In Fuel-saving Trial - Glide Into Airport

Wed Apr 04, 2007 4:45 pm

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.
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flyboy_se
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RE: Jumbos In Fuel-saving Trial - Glide Into Airport

Wed Apr 04, 2007 4:50 pm

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.
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777den
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RE: Jumbos In Fuel-saving Trial - Glide Into Airport

Wed Apr 04, 2007 7:23 pm

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"
 
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RE: Jumbos In Fuel-saving Trial - Glide Into Airport

Wed Apr 04, 2007 7:45 pm

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.

PS: I like your space shuttle analogy!  Smile
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zeke
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RE: Jumbos In Fuel-saving Trial - Glide Into Airport

Wed Apr 04, 2007 7:47 pm

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BA787
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RE: Jumbos In Fuel-saving Trial - Glide Into Airport

Wed Apr 04, 2007 7:55 pm

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
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RE: Jumbos In Fuel-saving Trial - Glide Into Airport

Wed Apr 04, 2007 8:00 pm

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.
 
Max777geek
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RE: Jumbos In Fuel-saving Trial - Glide Into Airport

Wed Apr 04, 2007 8:20 pm

Quoting Max777geek (Reply 7):
Engines are almost at idle during landing,

before the mess start, Id like to outline that I was meaning "at the last moments before
touching the ground".
 
chuchoteur
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RE: Jumbos In Fuel-saving Trial - Glide Into Airport

Wed Apr 04, 2007 8:26 pm

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
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RE: Jumbos In Fuel-saving Trial - Glide Into Airport

Wed Apr 04, 2007 8:32 pm

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.
 
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RE: Jumbos In Fuel-saving Trial - Glide Into Airport

Wed Apr 04, 2007 8:34 pm

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
 
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zeke
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RE: Jumbos In Fuel-saving Trial - Glide Into Airport

Wed Apr 04, 2007 8:40 pm

Quoting EI321 (Reply 11):

Perhaps they will set the engines at normal landing power just before landing

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.

Engine spool up by no later than 1000-1500' before landing.
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airfoilsguy
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RE: Jumbos In Fuel-saving Trial - Glide Into Airport

Wed Apr 04, 2007 8:54 pm

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.

[Edited 2007-04-04 13:55:41]
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georgiaame
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RE: Jumbos In Fuel-saving Trial - Glide Into Airport

Wed Apr 04, 2007 9:00 pm

Do I get a partial refund on my $150 "fuel surcharge" if we do a glide approach?
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airfoilsguy
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RE: Jumbos In Fuel-saving Trial - Glide Into Airport

Wed Apr 04, 2007 9:04 pm

Quoting GeorgiaAME (Reply 14):
Do I get a partial refund on my $150 "fuel surcharge" if we do a glide approach?

No, but you will get one extra pretzel or two peanuts, you choice.
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georgiaame
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RE: Jumbos In Fuel-saving Trial - Glide Into Airport

Wed Apr 04, 2007 11:00 pm

Given the circumstances, I think a free drink (or perhaps a double) might be in order.
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777ER
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RE: Jumbos In Fuel-saving Trial - Glide Into Airport

Thu Apr 05, 2007 4:35 am

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
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RE: Jumbos In Fuel-saving Trial - Glide Into Airport

Thu Apr 05, 2007 5:41 am

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....
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jafa39
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RE: Jumbos In Fuel-saving Trial - Glide Into Airport

Thu Apr 05, 2007 6:43 am

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?
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Braybuddy
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RE: Jumbos In Fuel-saving Trial - Glide Into Airport

Thu Apr 05, 2007 7:01 am

This article appeared in the Sunday Times travel section last Sunday.

1 April 2007.
 
airfoilsguy
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RE: Jumbos In Fuel-saving Trial - Glide Into Airport

Thu Apr 05, 2007 7:37 am

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.
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SABE
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RE: Jumbos In Fuel-saving Trial - Glide Into Airport

Thu Apr 05, 2007 10:57 am

Quoting Chuchoteur (Reply 9):
It is known as Continuous Descent Approach (CDA).

Correct, and it was developed by MIT & Georgia Tech and tested extensively with 5X at SDF back in '02 & '04. Here's a link with more information:

http://web.mit.edu/aeroastro/partner/projects/project4.html

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kaddyuk
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RE: Jumbos In Fuel-saving Trial - Glide Into Airport

Thu Apr 05, 2007 3:31 pm

I'm guessing this is the same as Continuous Descent Approach which has been in Trial at LHR for quite some time now...
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chuchoteur
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RE: Jumbos In Fuel-saving Trial - Glide Into Airport

Thu Apr 05, 2007 4:14 pm

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)
 
cobra27
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RE: Jumbos In Fuel-saving Trial - Glide Into Airport

Thu Apr 05, 2007 4:56 pm

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. I recommend tow trucks for starters
 
Max777geek
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RE: Jumbos In Fuel-saving Trial - Glide Into Airport

Thu Apr 05, 2007 5:10 pm

Quoting Cbphoto (Reply 18):
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.

this is impossible because ( I think ) the idle trust may allow an acceptable descent rate for a landing, not possible with engines totally turned off. Plus, the most source of noise I think it comes from the flaps after a certain angle (compared to idle trust).

Quoting Cbphoto (Reply 18):

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.

I don't get the difference, if they're turned on  Smile

Quoting Cbphoto (Reply 18):

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,

I think that such an airplane descent rate would depend on the speed, and the altitude, thinking to the time is flying with no power. It all depends by the speed, in the end of the hypotesis. Assuming you have the apu turned on yes, you can land in 1 second (touching the ground) and turning off the engines but how much fuel would it save ? (and then,
how do you reach the gate ? turning on again ?)

Quoting Cbphoto (Reply 18):

or B. need to add considerable amount of power to continue a normal approach to landing.

the trust needed to keep the airplane at Vflight idle doesn't seems to me that "considerable amount",
but Im talking with my eyes.
 
9V-SPJ
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RE: Jumbos In Fuel-saving Trial - Glide Into Airport

Thu Apr 05, 2007 8:53 pm

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 Go Around mention, that shouldn't be too much of a problem because to maintain the glideslope, thrust will increase.
I have worked on some profiles for LAX here at GT and hopefully, they will be placed into operation sometime after 7R/25L reopens. We have also done some work for PHL, EWR, JFK and ATL is our big project right now.

By the way, at SDF, we noticed that a/c were about 1000lbs of fuel while flying a CDA and yes it does reduce noise. If anyone wants more info on CDA research here at Tech, send me a message.

Cheers!

9V-SPJ
 
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RE: Jumbos In Fuel-saving Trial - Glide Into Airport

Thu Apr 05, 2007 10:21 pm

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.

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 engines partially spooled, at no time would the engines ever be off, it just makes sense to glide down from TOD on a more glide approach than it does to descent down and then need to burn fuel slowing rate of descent or maintaining altitude.

Quoting 777DEN (Reply 3):
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"
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baroque
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RE: Jumbos In Fuel-saving Trial - Glide Into Airport

Thu Apr 05, 2007 10:43 pm

Quoting Downunderflyer (Thread starter):

"These glide descent profiles will be flown with the aircraft engines set at idle, thereby significantly reducing fuel burn and emissions," he said.

This seems like a development of "M**** overdrive" a profile/gear well known in cars.  Smile
 
jafa39
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RE: Jumbos In Fuel-saving Trial - Glide Into Airport

Mon Apr 09, 2007 2:30 pm

Quoting Chuchoteur (Reply 24):
In my TB20, I'd have to be stacking for a long time to burn through that quantity of fuel...

True, but what about 737's A320's and ATR's???
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Analog
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RE: Jumbos In Fuel-saving Trial - Glide Into Airport

Mon Apr 09, 2007 2:52 pm

Quoting GeorgiaAME (Reply 14):
Do I get a partial refund on my $150 "fuel surcharge" if we do a glide approach?

No, you'll have to pay an extra $10 "Glide Approach Development surcharge".
 
COSPN
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RE: Jumbos In Fuel-saving Trial - Glide Into Airport

Mon Apr 09, 2007 5:06 pm

If they really cared about the enviroment they would go all twin like CO

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