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Topic: Ryanair Flying Slower To Save Fuel
Username: fcogafa
Posted 2013-07-29 08:03:32 and read 13398 times.

A Guardian article says that Ryanair are having a bad summer as pax are staying in the UK due to the good weather and that they are flying slower to save fuel.

Is this true, I thought speed helped efficiency?

http://www.guardian.co.uk/business/2...29/ryanair-profits-hit-uk-heatwave

Topic: RE: Ryanair Flying Slower To Save Fuel
Username: richcandy
Posted 2013-07-29 08:12:58 and read 13280 times.

In the distant past I remember reading something about Ryanair or it could of been Easyjet limiting the speed that their aircraft could operate at. This was to keep the aircraft operating at a more fuel efficient speed.

Sorry can't remember the details, but I don't think this is new.

Alex

Topic: RE: Ryanair Flying Slower To Save Fuel
Username: SANFan
Posted 2013-07-29 08:44:32 and read 12965 times.

I'm sure this particular carrier would operate its flights using only one engine if they thought they could get away with it!
 

bb

Topic: RE: Ryanair Flying Slower To Save Fuel
Username: olliejolly
Posted 2013-07-29 08:54:56 and read 12834 times.

Quoting fcogafa (Thread starter):
Is this true, I thought speed helped efficiency?

IIRC, I read only yesterday about a business jet(?) flying slower to conserve fuel and get more miles out of the tanks.
How that might scale up to a larger twinjet such as a 738 full of passengers, I don't know.

Topic: RE: Ryanair Flying Slower To Save Fuel
Username: Boeing77w
Posted 2013-07-29 08:58:00 and read 12814 times.

Ryanair introduced changes to the speeds through the use of a lower Cost Index last year. Fly slower, get there later but burn less fuel. Scheduled flight times were adjusted accordingly.

I believe they're currently in the process of implementing a new flight planning system which will use a variable Cost Index (a function of the FMC) depending on what is most efficient. So one day a high Cost Index may be required due to unfavourable winds, therefore they fly faster to arrive on time but burn more fuel. A few days later on the same route there might be significant tailwinds meaning they can fly a lower Cost Index, with slower speeds, and still arrive on time.

Topic: RE: Ryanair Flying Slower To Save Fuel
Username: peterinlisbon
Posted 2013-07-29 09:02:12 and read 12760 times.

Airliners fly at a cruising speed based on a cost index. This takes into account not only the cost of fuel but also other factors such as crew wages, aircraft lease rates etc. This optimal cruising speed varies depending on the load factor and the distance flown etc, and may actually change during the flight as the aircraft's weight changes as it consumes fuel over a long flight. As a plane slows down it has less aerodynamic drag, but more induced drag from the wings due to the increased angle of attack so the most economical speed is not necessarily a slow speed, and it varies depending on factors such as weight height, wind speed etc. For example, if you have a big headwind you'll want to fly fast to get spend as less time being carried backwards as possible, and with a tailwind you might as well slow down and enjoy the free ride. Obviously, Ryanair or any other airline does not want to spend any more on fuel than they absolutely have to, so they will try to minimise it's consumption by having operating procedures that minimise the use of fuel (flying at the most economical speed whenever possible, not starting descent too late, avoiding congested airspace and airports etc). The lengths to which airlines go to save money are amazing - I've heard that some airlines calculate which exit an aircraft should turn off at from the runway based on the cost of wear on the brakes vs. the cost (in both time and fuel) of taxiing back a bit further. And in the end the airlines that are most sucessful at this are the ones that survive!

Topic: RE: Ryanair Flying Slower To Save Fuel
Username: dazbo5
Posted 2013-07-29 09:07:17 and read 12692 times.

This is old news really. Given the cost of fuel, airlines don't go out of their way to burn fuel needlessly. Some airlines have reviewed cruise speeds and adjusted them to get better fuel economy long before now, it's nothing new.

Darren

Topic: RE: Ryanair Flying Slower To Save Fuel
Username: AerostarUK
Posted 2013-07-29 09:34:57 and read 12516 times.

Quoting dazbo5 (Reply 6):
airlines don't go out of their way to burn fuel needlessly

No, but pilots do........especially if they want to knock off early..... !

Topic: RE: Ryanair Flying Slower To Save Fuel
Username: BA777
Posted 2013-07-29 09:39:11 and read 12458 times.

This is a very sensible decision and saves a huge amount of money. It's just the same as driving your car more efficiently to get further range out of the tanks (eg accelerating more smoothly)

Topic: RE: Ryanair Flying Slower To Save Fuel
Username: LAXintl
Posted 2013-07-29 09:53:18 and read 12316 times.

Most carriers with modern aircraft utilize cost-index flight planning these days, which balances the cost of time with the cost fuel burn to come up with an optimal lowest cost solution. Virtually entire industry is flying slower these days.

Its can indeed often cheaper to fly slower, saving the fuel, as long as added time related cost (crew, maintenance, etc) are not greater.

Topic: RE: Ryanair Flying Slower To Save Fuel
Username: Boeing74741R
Posted 2013-07-29 09:55:52 and read 12296 times.

Considering the amount of padding in the schedules of a number of Ryanair flight, does it make much of a difference in a lot of cases?

Topic: RE: Ryanair Flying Slower To Save Fuel
Username: oly720man
Posted 2013-07-29 09:58:37 and read 12254 times.

Transonic drag rise, or drag divergence is the technical term. As you approach Mach 1 there is a fairly rapid rise in drag (discounting suitably designed wings) that happens around M0.75 due to the development of areas of supersonic flow over the wings and fuselage, due to the flow acceleration around these surfaces. By flying slower, this is avoided.

Topic: RE: Ryanair Flying Slower To Save Fuel
Username: bueb0g
Posted 2013-07-30 03:03:18 and read 8282 times.

Pretty much every low cost, low fare or charter airline has been doing this pretty much forever via a low cost index in the FMS. Not exactly news.

Topic: RE: Ryanair Flying Slower To Save Fuel
Username: 1400mph
Posted 2013-07-30 03:22:42 and read 7999 times.

Coinciding with a collapse in profit this particular bubble is showing signs of bursting.

This has been predicted but they had a good innings while it lasted !

Topic: RE: Ryanair Flying Slower To Save Fuel
Username: bongodog1964
Posted 2013-07-30 04:57:13 and read 6653 times.

Quoting 1400mph (Reply 13):
Coinciding with a collapse in profit this particular bubble is showing signs of bursting.

I wouldn't use the word "collapse" to describe a 20% fall in profits. Yes its a fall, perhaps a "sharp fall" as the BBC described it, though I would ever say thats over dramatic.
To me a "profit collapse" is when they fall by 50% or more, or even into the red.

Topic: RE: Ryanair Flying Slower To Save Fuel
Username: LonghornDC9
Posted 2013-07-30 05:23:34 and read 6244 times.

Quoting fcogafa (Thread starter):
Is this true, I thought speed helped efficiency?

Actually, for aircraft, speed vs fuel consumption is not a linear problem. There comes a point where if you start flying too slow, your fuel efficiency will start to get worse again due to the drag characteristics of the airplane as well as the efficiency characteristics of the engines. However, it is my impression that for most aircraft flying today, the speed where this happens is quite a bit slower than the speeds the aircraft typically cruise at. So, there's kind of a "sweet spot" of fuel efficiency - go to fast and your efficiency gets worse, go too slow and your efficiency gets worse. That's why most jetliners today cruise between approximatly Mach 0.75 - Mach 0.85

From the article, sounds like Ryanair is just slowing down a few knots from some "normal" cruise speed to some "long-range" cruise sepeed.

Didn't know about all that cost-index flight planning stuff, but it's interesting and makes a whole lot of sense!

Topic: RE: Ryanair Flying Slower To Save Fuel
Username: BlueShamu330s
Posted 2013-07-30 05:41:20 and read 5957 times.

Quoting BA777 (Reply 8):
This is a very sensible decision and saves a huge amount of money. It's just the same as driving your car more efficiently to get further range out of the tanks (eg accelerating more smoothly)

Not necessarily.    In isolation, perhaps, but in a dynamic Air Traffic scenario, very rarely so.

In one of my past employs, we were mandated to fly cost index speeds through the entire flight, including descent, in an attempt to lower fuel burn.

Rather than allow us to fly the aircraft, appreciate the traffic around us and the sequence we were in, Ops made it SOP that we had to follow the Cost Index. Rather than save fuel, it hacked off ATC, hacked off other traffic and hacked off our customers as, invariably, we were sent off to the hold at 230kts or vectored around the sky whilst our competitors sailed past us in the descent at 300+kts, much to the delight of the yellow flying harps.

Once management realised that block fuel was actually increasing, the SOP soon became an advisory in which it did not prevent the commander from using his own discretion or from complying with ATC speed requests. We went back to flying and aviating, and fuel burn went back down to prior levels.

The problem with flying slower is that it only works if everyone around you is doing the same. If not, the slower one runs the risk of extended routings and holding, which increases fuel burn, which defeats the object of it all.

Quoting LAXintl (Reply 9):
Virtually entire industry is flying slower these days.

   Except Iberia !!  
Quoting 1400mph (Reply 13):
Coinciding with a collapse in profit this particular bubble is showing signs of bursting.

Don't be ridiculous. It's a procedure which has been tried, tested and matured over some years now.

Rgds

Topic: RE: Ryanair Flying Slower To Save Fuel
Username: AirPacific747
Posted 2013-07-30 06:06:30 and read 5553 times.

Ryanair uses cost index 6 as far as I know.

Topic: RE: Ryanair Flying Slower To Save Fuel
Username: brilondon
Posted 2013-07-30 06:42:20 and read 4929 times.

Quoting AerostarUK (Reply 7):
No, but pilots do........especially if they want to knock off early.....

There are wayyyyyyyyy too many people watching you and monitoring the flight, fuel burn and traffic as you approach the airports...oh wait this is Ryanair. They fly into airports no where near to any major metropolitan areas.   

Quoting BA777 (Reply 8):
This is a very sensible decision and saves a huge amount of money. It's just the same as driving your car more efficiently to get further range out of the tanks (eg accelerating more smoothly)



This is not always true. You may be driving slower to save fuel but there is a point where driving faster you use less fuel to travel over the same distance because of going faster, you run your car less and save fuel that way.

Topic: RE: Ryanair Flying Slower To Save Fuel
Username: JAAlbert
Posted 2013-07-30 06:57:15 and read 4621 times.

Quoting AirPacific747 (Reply 17):
Ryanair uses cost index 6 as far as I know.

What is cost index 6 and how does it differ from cost indexes 1-5? (are there indexes 1 thru 5?)

Topic: RE: Ryanair Flying Slower To Save Fuel
Username: BA777
Posted 2013-07-30 08:03:19 and read 3548 times.

6 is just a number, from the 737NG manual:

"Valid entries are 0 to 500. 0 causes the ECON speed to be MAX RANGE; 500
results in a minimum time flight."

500 is an extreme number, I don't know of any operators who would use more than 100. I would imagine if ATC assign a speed, you follow it and accept it as they're doing it for a reason - otherwise don't complain when you get sent into a hold.

Topic: RE: Ryanair Flying Slower To Save Fuel
Username: BlueShamu330s
Posted 2013-07-30 08:07:34 and read 3480 times.

Hope this helps to understand Cost Index:


http://www.skybrary.aero/bookshelf/books/1956.pdf

Rgds

Topic: RE: Ryanair Flying Slower To Save Fuel
Username: Dogbreath
Posted 2013-07-30 08:30:56 and read 3324 times.

Quoting 1400mph (Reply 13):
Coinciding with a collapse in profit this particular bubble is showing signs of bursting.

Oh really! This drop in profit for the first quarter was predicted by FR and they were right. Pax up 3 % and revenue up 5%, higher fuel costs, and the placement of Easter holidays pre Q1 but still on target for an overall profit of €570 - €600million for the FY. What bubble?

Quoting 1400mph (Reply 13):
This has been predicted but they had a good innings while it lasted !

Mate. Join the queue of the many disappointed FR haters predicting the fall of Ryanair. The queue has been growing for over 10 years plus. You might be waiting a while. Good luck to ya.

Topic: RE: Ryanair Flying Slower To Save Fuel
Username: babybus
Posted 2013-07-30 08:56:17 and read 3226 times.

I suspect a lot of airlines are flying slower to save money. Just recently I took a CPH flight that used to take only 1.20mins. The last 2 flights were 1.40. Nothing to do with runway or ATC.

British Airways also admitted to flying slower to save money. I think that was in one of their in-flight magazines.


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