Headwinds

[paweas]

Hi all first post here im student pilot,i have a question for any current CPL/ATPL pilots,
On a flight from Tokyo nrt to hkg crusing @ fl370 (A330-300 )with a headwind of 181kt / gs 308 /@ m0,74 and a fuel burn of 3460ph
would it be better to decend to
fl 240 with a headwind component of 73kt /gs 371/@ m0,74 and a 3824ph fuelburn presuming atc cleared.

Would the increase in groundspeed justify the increased fuelburn, and also would company SOP/ICAO allow this.

any help would be great.
thanks

[Fullblast]

No problem for ICAO if you choose a lower level (if not limited by other factors); any company has his own SOP, but normally no problem.
Usually, planning for FL370 and then flying at FL240 would need too much more fuel, so probably you also need a replanning to stay inside the minimum block, or at least have reserve fuel intact upon landing.
By the way, going back to the question, the cost difference in fuel burned vs flight time is different for each plane and for each company (you can see that any company has a different cost index), that means that there isn't an absolut answer to the question....but if it was up to me...at least with the oil price of few months ago...i'd go for high level, no question.

FB

[TopBunk]

Punching in some quick numbers:

NRT-HKG is about 1650nm. For a cruise segment of say 1500nm.

1. At FL370, you burn16850kgs of fuel,
2. At FL240 you burn 15460kgs of fuel.

So simplistically, for fuel alone, it is better to fly lower in this case. The will be time related savings as well due to shorter flight time at the lower level. As I say it is simplistic, in that extra fuel will be used to climb to 370, but less fuel used in the (longer) descent.

[farefield]

well it seems to me that in rough terms you are getting 20% increase in groundspeed for a 15% increase in fuel burn if you go down, so it's worth doing.For every hour at altitude you could cover the same distance in 50 mins at the lower level and would burn appx 92% of the fuel

There are,of course other issues to consider but you didn't ask about those.

[bfisk]

Fuel wise, what you need to calculate is specific consumption in terms of fuel used / nautical mile. As 1 kt is 1 nm/hr, the equation would simply be Fuel burn rate/ground speed, which when multiplied with time, yields fuel burn/nautical mile. In your example:

3460pph/308kt = 11.23 lbs/nm
3824pph/371kt = 10.31 lbs/nm

So to go lower would be better in your case, looking only at this factor. The time saving is also beneficial in terms of maintenance and time related costs.

[paweas]

Cheers folks some fantastic replys on this topic!!!!!
i Guess i didn't provide enough information to be precise,
here is the real world weather along some of the route and winds aloft to see if it changes the outcome of the answer from an operational standpoint.

RJAA 081800Z 00000KT 7000 NSC 01/00 Q1025 NOSIG
RJAA 081442Z 0815/0918 33004KT 7000 SCT030 BECMG 0906/0909 4000 -RA BR BKN008 BKN015 TEMPO 0915/0918 3000 SHRA BR BKN005
FL030: 211/08 (6.80) FL060: 217/16 (3.80) FL090: 217/20 (0.80)
FL120: 240/46 (-7.90) FL180: 238/73 (-21.10) FL240: 238/82 (-32.20)
FL300: 238/145 (-41.50) FL340: 242/172 (-45.10) FL390: 246/189 (-51.10)

RJNH 080917Z 35005KT 9999 FEW030 BKN130 10/03 Q1026 RMK 1CU030 5AC130 A3032
RJOO 081441Z 0815/0918 07004KT 9999 -SHRA FEW025 SCT040 TEMPO 0906/0909 4000 SHRA BR BECMG 0909/0912 32005KT
FL030: 181/14 (7.70) FL060: 207/26 (3.00) FL090: 229/26 (0.70)
FL120: 225/44 (-7.40) FL180: 236/59 (-20.80) FL240: 232/66 (-33.30)
FL300: 230/138 (-41.70) FL340: 235/169 (-45.10) FL390: 238/190 (-52.10)



RCSS 081700Z VRB02KT 9999 FEW018 BKN050 BKN120 17/15 Q1019 NOSIG
RCSS 081700Z 0818/0918 10005KT 9999 FEW018 SCT035 BKN060 TEMPO 0818/0901 6000 RA FEW014 BKN025 BKN050 BECMG 0901/0903 09010KT
FL030: 045/23 (13.40) FL060: 039/11 (8.90) FL090: 342/03 (6.00)
FL120: 299/13 (-3.70) FL180: 237/35 (-18.30) FL240: 240/54 (-25.60)
FL300: 234/107 (-29.10) FL340: 236/136 (-35.40) FL390: 240/136 (-49.90)

RCTP 081730Z 13003KT 9000 FEW015 BKN110 17/13 Q1019 NOSIG
RCTP 081700Z 0818/0924 08007KT 9999 FEW015 SCT040 BKN080 BECMG 0900/0902 05015KT
FL030: 043/18 (12.30) FL060: 064/08 (8.70) FL090: 045/03 (5.50)
FL120: 284/11 (-3.70) FL180: 253/29 (-18.70) FL240: 250/46 (-25.60)
FL300: 239/94 (-30.90) FL340: 237/133 (-35.50) FL390: 242/138 (-49.10)

RCKH 081700Z 36007KT 330V030 8000 FEW012 BKN100 19/15 Q1016 NOSIG
RCKH 081700Z 0818/0924 01007KT 8000 FEW012 SCT035 BKN070 TEMPO 0821/0901 4500 BR BECMG 0901/0903 33012KT BECMG 0914/0916 02007KT
FL030: 037/25 (14.50) FL060: 025/05 (10.50) FL090: 028/02 (7.80)
FL120: 242/23 (-2.30) FL180: 253/37 (-16.50) FL240: 253/64 (-19.90)
FL300: 244/106 (-24.60) FL340: 243/113 (-36.90) FL390: 244/116 (-50.90)

ZSAM 081800Z 00000MPS 4500 BR SKC 11/10 Q1019 NOSIG
ZSAM 081530Z 0818/0918 08004MPS 6000 SCT025
FL030: 039/08 (9.90) FL060: 041/03 (8.50) FL090: 335/02 (5.70)
FL120: 273/14 (-4.30) FL180: 305/18 (-16.80) FL240: 274/35 (-27.40)
FL300: 273/68 (-34.40) FL340: 263/81 (-39.30) FL390: 252/123 (-47.10)

ZGOW 081800Z AUTO 32003MPS 5000 NCD 12/10 Q1019
ZGOW 081529Z 0818/0918 08004MPS 2100 BR BKN040 TEMPO 0818/0824 1200 BR BECMG 0901/0902 6000
FL030: 053/13 (13.50) FL060: 076/07 (10.00) FL090: 035/05 (7.10)
FL120: 287/13 (-2.90) FL180: 291/22 (-13.30) FL240: 291/56 (-22.40)
FL300: 280/87 (-29.40) FL340: 258/106 (-35.00) FL390: 256/113 (-49.60)


Any BA pilots out there / i believe BA fly this route in cargo ops as BA3708B WITH THE 747-400F
What FL would you Pilots choose and why?
Presuming the flight is in an A330-300

CHEERS

[Intruder]

In practice, you would not dream of descending that far. The most I ever came down was 4000'. You cannot disregard setting off the eventual climb back up to altitude from your theoretical savings of descending.

It is not as uncommon a practice as you may think, westbound over the Pacific, approaching Japan. I have seen 200Kt+ headwinds at altitude with no significant drop-off until 6,000-8,000' below planned cruising altitude.

Personally I have used the tactic to "duck under" the jet stream a few times, and other pilots in the company have reported the same. The key is to use and understand the wind trade charts in your Performance Handbook (or wherever you find the charts for your operation), and have a good confidence level on the actual winds at the planned lower altitude.

[john_tullamarine]

Sometimes one is better off being innovative. The following tale is not wind related but still is pertinent to the discussion.

Years ago, MEL-CBR, I can recall a dreadful weather pattern with TS enroute all day. The majority of the burners were going to normalish levels and then diverting ridiculous track miles to avoid returns.

One DC9 crew took a more pragmatic approach, flew comparatively low, well under the cells, and trundled back and forth for their tour of duty .. no significant weather problems .. and kept easily to schedule.

Fortunately, CTA LL were compatible with the strategy.

[TopBunk]

I don' think that it is realistic to expect people to get airway charts out and plot a route and superimpose spot winds for airports not necessarily on the route and come back to you with a best vertical profile

What we have done is to give you the basic principles and the ammunition to do that youself.

So go and do it

[BTW: what has the aircraft type got to do with it - it is only a fuel burn number that plugs into the equation - furthermore, while BA aka GSS may fly the route, they certainly don't operate A330's]

[paweas]

Top Bunk thx for the reply i apologise, i am new to all this so i dont know much about the charts you mention i certainly dont expect folk to do any work for me ,however i though it was an interesting dilema for current pilots as personally i would choose to decend to FL 240 exchanging an extra 364 kgph of fuel over 1650nm for an increase in gs of 108kt just my two cents worth as a trainee pilot.

but hey i guess with todays fuel prices and robot metality of airlines you probably dont get to make that choice as pic any more.

Quote top bunk
[BTW: what has the aircraft type got to do with it - it is only a fuel burn number that plugs into the equation]

IMHO as a student i should think everything ! if im flying an A330-300 with full pax and cargo surely it's going to burn a hell of a lot more fuel than say a empty 737-800 on a line training sector ,surely aircraft type /weight/cost index play a part in a pilots decision to decend/climb.........no ?
also i merely mentioned the A330 as an example as it's a common type operated by asian airlines who possibly fly this route.

but hey folk remember....

I AM NOT QUALIFIED TO COMMENT ON THIS AS A MERE STUDENT AND SIM PILOT!!!! SO DONT TAKE THIS AS A PERSONAL CHALLENGE FOLK.

For me it's just an interesting decision which if i was running an airline or as a dispatcher or a responsible pilot i would want to examine this decision very carefully with todays fuel prices.
I wonder if this is why airlines are scratching their head when they go spread eagle....pointing fingers at Pilots/pax and market conditions when common sense would dictate their single biggest operating overhead could be greatly reduced by leaving the decision tho the folk who operate the aircraft on the cutting edge.....no ?
Perhaps some pilots couldn't care less as long as their legal upon landing to hell with the suits and pax hey...whats another 2hr added to the trip and £15000 's worth of A1 as long as im in time for last orders at the hotel bar he says lol

just my wee bit lol probably bs but i'd like to hear the reality from like minded pilots or dispatchers, either way folk it's a problem were all going to face as pilots sooner or later in our flying career with dwindling oil supplies i suppose it depends whos paying lol......

[Wizofoz]

In practice, you would not dream of descending that far.

Why on earth not? If it gives you a better specific fuel burn AND a better ground speed it is the place to be!!

I've flown SYD-MEL at FL 220 in a 737 before now, as it offed the best fuel burn and a lower flight time. Jets don't HAVE to fly in the 30s and 40s, they still WORK down lower!!

[TopBunk]

Paweas

I wasn't saying that fuel burn was unimportant, or that we would deliberately to operate inefficiently by that statement.

I will try again .... the type is irrevelent to the decision. You take the fuel flow and groundspeed for the type/any type at the different levels and do the maths. If it makes sense to fly lower and there are no other considerations, then go for it. The fact that a 747 may burn 10 tonnes/hour and a 330 only 4 and an empty 737 2 tonnes is neither here nor there, it is the efficiency for whatever you are flying that counts.

Most airlines in this day and age have very sophisticated flight planning systems in place in order to minimise total costs. As well as considering winds and levels they will consider flight time for maintenance (and crew overtime costs), for schedule regularity, for ATC overflight charges, air temperatures (think BA777 Jan08!) and other things. As a B747 Captain, I endeavour likewise to deliver the passengers on time having had a comfortable and enjoyable flight having been well looked after adn to have used minimum fuel - ie at least cost to my employer (and the worlds oil reserves).

[Wizofoz]

It doesn't work on the vast majority of occasions in real life.

Rainboe,

I think you might be assuming that the vast majority of YOUR life is the same as the vast majority of everywhere else!!

What you say may be true Trans-Atlantic or over India, but domestic ops in the US, Australia, Japan, Africa and over much of Asia are often operated at lower levels to avoid the winds.

[gimmesumvalium]

Some Lateral thinking required here, gentlemen:
Let's stay at FL370 and make some overtime.
(coz the company ain't gonna thank you when they furlough you!)

[enicalyth]

corrections needed first

VHHH is not a long hop, only 1680nm and mostly on airway A1 which by regional consent is westbound FL 280 300 340 380 400. Notice no FL360. And certainly no FL370 or 240 come to that.

My answer at a board would include West Pac South China Sea weather in general; what constitutes a Large Scale Weather Deviation and what doesn’t; show familiarity with the relevant AIPs and the terms FLOS, FLAS and No PDC; demonstrate local route knowledge and how good the Ops people are at planning; I’d cover fuel reserves in general and what my airline and/or the one I’m boarding for lay down. I’d express the view that for RJAA VHHH I’d be expecting FL340 all the way and a higher load factor than the fuel burn suggests. (It should be a popular route). The low fuel burn invites some mention of buffet if you outclimb the airframe capability. But if the winds took a turn for the worse I’d ask for lower expecting to be granted either FL280 or FL300. Providing that I wasn’t right on top of my ToD of course.

If you'd like to see more of what is involved drop me an e-mail.

Best Rgds

The "E"

[john_tullamarine]

As an aside, it is a lemma that some of us tend to be more relaxed than others .. or more serious ... depending on which side of the table one sits.

Some of us write in a more "serious" style than others and comments can be misinterpreted in respect of intent.

Main aim here, though, is to consider all comments with a degree of respect and acceptance which reflects the fact that we represent a wide spectrum of individual and social differences.

Sometimes it is a fine line which separates acceptable banter from unacceptable sarcasm and the like. Generally, the good folk here are able to stay on the preferred side of that line ...

[Semu]

Wow Rainboe, you seemed to operate in a pretty confined world for a longhaul pilot. While your comments are certainly true concerning India in rush hour, they fail to hold true in much of the world, or even over India in off peak times.

As to a number of peoples comments about the accuracy of computer flight planes, true, often. Had a twenty-five knot stronger headwind than forecast on a KMEM PANC leg last week, and that is in the part of the world with good weather forecasts and reporting. More then once I have found the weather forecast worse than useless at the end of an eight hour flight (admitadly a bit off of the original topic).

[Capt Fathom]

or even over India in off peak times.

I didn't realise India had an off peak time!

[john_tullamarine]

moderation is obviously a black art to me

.. as, indeed, it is for us as well.

I don't set out to censor posts unless they be offensive, against site policy direction, or totally silly.

I had presumed that the post cited had significance to some of the readership even if I, like you, had no idea what that significance might have been.

In short, we can't please all of the people all of the time .. and, at times, we probably get many/most off side. That's the nature of the moderation beast, I'm afraid.

[john_tullamarine]

except for the 2 relevant posts and keep on the subject?

I don't propose to do that and it is appropriate to identify my reasoning - it is not the moderator's place to dictate thread content and direction (except within the sort of boundaries I indicated before). We are there to give Danny et al a hand .. that's all (OK, most of the time it's good fun as well).

The result is that one pleases some of the people

(a) most of the time

(b) some of the time

(c) never.

.. goes with the job, I'm afraid.

I see that nosewheelfirst has chosen to delete his/her posts .. his/her decision is respected but I would ask that he/she consider reinstating them as there will be others who would appreciate the answer to the cryptic question ..