Jump to content

Sign in to follow this  
Guest Vagabond78

Long Range Pacific Flights

Recommended Posts

Guest Vagabond78

Hi folks,I have some questions about long range pacific flights. I am trying to duplicate Qantas fligth QF12 which services YSSY from KLAX but I am running into a few problems. I am trying to use FS Build 2 to do the fuel calculations for me but it keeps providing a fuel load that is greater than the capacity of the 744. It is requesting 408603 lbs of fuel. I am using an actual flight plan used by QF12 from http://flightaware.com.Here is the properties of the flight.FP: KLAX PERCH9 FICKY B581 AFONE B581 CAMOS B581 WACOS B581 BAXIL B581 NN A579 TESAT A579 NATLI ABARB SHARK N774 SY YSSYALTN: YBBNPayload: 71,880 (It seems it is impossible to fly with 2/3 PAX/Cargo loading without exceeding the maximum T/O weight of 875,000 lbs.)I am using %10 Reserve fuel with :30 minutes of hold fuel.I also used winds aloft data from ActiveSky 2004.5, I averaged the wind out based on the flight plan generated by FS Build and it is around 34kts.So here is where I stand; my fuel load is approximately 20000 lbs over the maximum capacity of the 744 and I must take less than the 2/3 PAX option in the load manager. I have tried doing the fuel planning manually as a backup but I am running into trouble calculating the contingency fuel. Specifically, I don't know the lbs/hr for holding.One thing that I have come up with as a cause of the fuel situation is that the FS Build performance file and the fuel charts provided by PMDG are for the high speed cruise of M.86. I was looking up information on the PS1 website and it speaks of alternate charts that are based on M.80 cruise, however I can't locate these charts. So how are we supposed to calculate fuel requirements for LRC which have slower cruise speeds than M.86? I have read that it would be around M.84 but I am not sure this would make much difference. It doesn't seem logical that an airline would calculate fuel requirements based on M.86 cruise when using MRC or LRC.My final question is this; How do the airlines load passengers and associated luggage for these long range flights? If I am doing everything correctly, it seems like there will be alot of empty seats and cargo space on these flights since you are required to carry so much fuel. When I used 2/3 PAX I was exceeding 1 Million lbs for the gross weight. (As calculated by FS Build)Thanks in advance for looking and any help provided.Happy New Year

Share this post


Link to post
Guest

there are a few fuel calculation programs in the library that will probably give you a more accurate number

Share this post


Link to post

>My final question is this; How do the airlines load passengers>and associated luggage for these long range flights? >One fact is certain - they have much better tools and much more accurate methods to make fuel calculations. I am not a fan of those long range flights but if I were to attempt one I would did the best job using the fuel calculation that is available to us (if based on 0.86 Mach so bid) and then flew in the LRC mode as an additional backup. And then I would carefully monitor the fuel flow, remaining fuel throughout the flight and I would not despair if I had to land short of the destination. If you accomplish such a flight and manage to reach the destination this could serve as an invaluable source of fuel-calculation data for your next long haul flight. You could even share your tips with others. Nobody said you have to get it right first time - not in a simulated flight ;)Also be careful when borrowing flight plans from flightaware. Although these are real-life flight plans they are only valid for a given date. There may be significant differences based on prevailing winds specially on those transoceanic flights. If you use a flight plan that was executed on a date when winds were significantly different from your (sim) winds you may actually be making things even worse. However if you managed to grab a flight plan for a given date and then fly it with archived weather data (if you have ASV) then you could be a big winner. Airlines know very well how to find wind-optimal routes.And last but not least I believe Qantas is using the extended range version of the 747-400 on this route - it gives them hundreds of extra miles in range. PMDG's version is not the -ER.Michael J.http://www.precisionmanuals.com/images/forum/pmdg_744F.jpghttp://www.hifisim.com/images/asv_beta_member.jpg


Michael J.

Share this post


Link to post
Guest Vagabond78

Thanks for the info Alex, I found the programs that you suggested.Michael, thank you for the wealth of information that you provided. I had noticed on the Qantas website that they were using the 747-438 Longreach. I guess that may be more of a factor than I thought. Do you know if I can get archived weather in AS2004.5? If not I guess that I could save the weather on the day that I look up the flight plan on flightware. That brings me to another question; Will FS Build provide an efficient flight plan using imported winds aloft data? (Maybe a question for the FS Build forum)Finally, does someone have access to the alternate cruise charts?

Share this post


Link to post

>Do you know if I can get archived>weather in AS2004.5?Check if you own it. I think you can.> Will FS Build provide an efficient flight plan using imported winds aloft dataFrankly I seriously doubt it, based on my information they don't attempt to customize flight plan route based on winds. But you may double check with them. The wind-optimal route computations are actually quite complex. Your best bet is using flightaware flight plans with matching winds (bu make sure they match!).Michael J.http://www.precisionmanuals.com/images/forum/pmdg_744F.jpghttp://www.hifisim.com/images/asv_beta_member.jpg


Michael J.

Share this post


Link to post
Guest Darren Howie

G'day EricFirstly drop your 10% variable.Long range flights use a thing known as refile for computation of VR on flightplans.What this means is that effectively the VR is based off the most critical diversion point along the route.So YSSY-KLAX would be 10% of the flightfuel to go from the critical point from PHNL-KLAX.assuming this is say 1100nm or so and 40000lb/hr at say 500kts.Call it 2.2hrs so your VR would be 8800lb.This is opposed to 10% of the total flightfuel or some 35000lb.As you can see it makes a big difference.The most critical point for fuel is always the depressurised one with a diversion at normally 10000'.QF 744's are fitted with extra Oxygen bottles or this very reason to lower the fuel required as they can divert at altitudes well above ALL other airlines and hence can carry more payload on sectors flown by other companies.HTHDarren

Share this post


Link to post
Guest Vagabond78

Darren,Thanks for the awesome information about Qantas flight operations. I was unaware that the 10% was from the critical point of the flight and not the entire flight. I am however a little confused about the depressurized diversion you spoke about. I don't understand what the oxygen bottles have to do with the fuel required for the flight. At first I thought you were saying that Qantas pressurizes the tanks but that seems like a really bad idea with oxygen and doesn't make any sense to me at least. Could you please clarify what you are talking about and how the extra oxygen bottles reduce the fuel required for a diversion?Also do you know if it is common for Qantas' flights from KLAX to YSSY to not be full of passangers and to have alot of empty seats or do they send baggage on a different flight?Thanks in advance.

Share this post


Link to post

>about and how the extra oxygen bottles reduce the fuel>required for a diversion?He probably meant to say that when they have additional oxygen they can divert using higher flying altitudes, diverting at 10000 ft alt for reason of depressurization would be very costly in fuel.>Also do you know if it is common for Qantas' flights from KLAX>to YSSY to not be full of passangers and to have alot of empty>seats or do they send baggage on a different flight?I would bet my house that Qanats is able to fill every seat on this flight, and luggage. No airline would assign an aircraft to a route that would cause serious operational disadvantage.Michael J.http://www.precisionmanuals.com/images/forum/pmdg_744F.jpghttp://www.hifisim.com/images/asv_beta_member.jpg


Michael J.

Share this post


Link to post
Guest Vagabond78

>I would bet my house that Qanats is able to fill every seat on this flight, and luggage. No airline would assign an aircraft to a route that >would cause serious operational disadvantage.Does this mean that the -400 and -438 are that much different? I will have to go back and run the fuel calculation again with a full load of passengers and cargo to see what kind of fuel load is required for the -400. Additionally, I will try and dig up more information on the -438 Longreach.Thanks for your time.

Share this post


Link to post

Eric,I've done both QFA 12 and 26 (To NZAA) from LAX and have no problem with fuel. I also use FSBuild and get the 400+ thousand fuel number. To YSSY I go with full tanks and end up overhead with around 30,000 lbs left. I also approach this as a sim. If I run out of fuel, so be it... :-)Scott


Kendall S Mann

Still Telling Pilots Where To Go!!

Share this post


Link to post
Guest Vagabond78

Hey there Scott, Thanks for you thoughts on this subject. I too realize and approach this as a sim. The question was to broaden my knowledge of the subject and to save my self some 14.5 hrs of flight time. I know I could have "refueled" in the air but I just wanted to understand the capabilities of this great sim and also airline flight operations. :) Since I now know that I can make the flight, I have one more question for you. Did you use M.86 cruise or did you set the cost index to 0 for MRC or a little higher for LRC? I am anxious to get this bird off the ground, I've been grounded for two days now. :(I'm still wondering if anyone has access to the alternate cruise charts that are used for long range flights.Thanks for the help so far everyone.

Share this post


Link to post
Guest Darren Howie

G'day EricBy installing extra oxy bottles on board the Qf 400's it means that.The aircraft can divert from the most critical point on its flightpath after a depress at a higher altitude than other carriers.Normally the aircraft must descend to 10000' as the pax only have limited oxy supply.By putting in extra bottles QF can divert at higher altitudes than 10000'.This means a lower fuel burn on the diversion and hence far lower fuel usage on the diversion and reserve fuel required.Hence the aircraft carries more payload and less fuel legally.It also allows QF aircraft to fly more direct tracks though Asia particularly around the Himalaya's saving thousands of dollars in fuel every week.As the aircraft can maintain higher altitudes after a depress it means it can accept higher lowest safe alts on sectors.The cost of the extra cost/weight is more than offset by the savings.CheersDarren

Share this post


Link to post
Guest Vagabond78

Thanks Darren,Your explination is crystal clear now. I am back to one of my original questions. I had chocked up the fuel load for the Qantas flight exceeding the tank size due to the operation of -438 Longreach series of aircraft, however I was looking into a Cathay Pacific flight which goes from KLAX to VHHH and I can meet all the fuel and loading requirements if I take less than 2/3 PAX on the load manager. This was 71880 lbs for the entire payload. This still doesn't make sense to me that I cannot take more passengers. As Michael said above, the airlines wouldn't run a trip like this with too many empty seats. It seems like Cathay Pacific is operating -412 series aircraft on this route according to airliners.net. Is there a large difference in the fuel economy of a -412 vs. -400? If not why am I not able to take more people on board? The average wind speed was a head wind at about 68 kts.Thanks for the help everyone, sorry I am still confused.

Share this post


Link to post

Or you can use a 777-200LR and be better off. Sorry, w/ my screen name I could not resist...I am j/k of course.


Eric Fisher  

 

 

Share this post


Link to post
Guest Vagabond78

LOL no problem, I understand.

Share this post


Link to post

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  
  • Tom Allensworth,
    Founder of AVSIM Online


  • Flight Simulation's Premier Resource!

    AVSIM is a free service to the flight simulation community. AVSIM is staffed completely by volunteers and all funds donated to AVSIM go directly back to supporting the community. Your donation here helps to pay our bandwidth costs, emergency funding, and other general costs that crop up from time to time. Thank you for your support!

    Click here for more information and to see all donations year to date.
  • Donation Goals

    AVSIM's 2020 Fundraising Goal

    Donate to our annual general fundraising goal. This donation keeps our doors open and providing you service 24 x 7 x 365. Your donation here helps to pay our bandwidth costs, emergency funding, and other general costs that crop up from time to time. We reset this goal every new year for the following year's goal.


    2%
    $540.00 of $25,000.00 Donate Now
×
×
  • Create New...