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 Safety, CRM, QA & Emergency Response Planning A wide ranging forum for issues facing Aviation Professionals and Academics

 1st Jun 2006, 10:47 #1 (permalink) Thread Starter   Join Date: May 2006 Location: High in a tree... Posts: 14 Contingency fuel... When using the Jeppesen flt planning system to calculate max payload, fuel required for given payload etc. Why does the system assume that the 5% contingency fuel is burnt by the time you arrive. The fact is that this fuel is a buffer of extra fuel in case the situation arises where you might need it, but if this situation doesnt arise, then you arrive at your destination with it still in the tanks. If you are arriving at max landing weight, the reality is that you are arriving at your max landiing weight, plus the weight of the contingency fuel. In other words an overweight landing, which could be several tons over your max ldg wt. This is concurred when the loadmaster completes his loadsheet, where the maths don't lie. His loadsheet in this case will show an overweight landing...
 1st Jun 2006, 14:11 #2 (permalink) Join Date: Mar 2005 Location: U.K, I think..... Posts: 26 Not sure if all flight planning systems do the same...ours isn't Jepp but it also assumes you will have burnt CONT fuel by the end of the trip. Doing lots of short sectors we often come up against this problem but its easily solved at flight planning stage by working forward... Simply add TRIP fuel figure to MLW and bingo you have a figure for MTOW. If you burn your CONT fuel then all is well. If you make fuel on the trip then you have to consider options for burning off fuel prior to landing but thats life.
 1st Jun 2006, 16:11 #3 (permalink) Thread Starter   Join Date: May 2006 Location: High in a tree... Posts: 14 Contingency fuel I take your point, but you shouldn't have to look for ways to increase your fuel burn in order for the a/c to land within limits. In a lot of situations it is not practical to do, and it certainly is not professional from an aviation point of view. Also, in this situation, as the loadsheet speaks the truth, the Capt wont sign it as it shows an overweight landing. So the loadmaster then has to falsely increase the fuel burn in order to reduce the landing weight, to give the appearance on paper that the a/c is arriving within limits, but in reality it is still landing at the MLW plus the weight of the contingency fuel. Three things have happened here: 1. The a/c has been operated illegally, 2. The loadmaster has falsified an official aviation document. 3. The Capt has signed a falsified document. If there was an accident and these issues came to light, where would the company stand from an insurance point of view ?
 1st Jun 2006, 16:41 #4 (permalink) Join Date: Nov 1999 Posts: 2,272 I might be missing something here, but wouldn't you just add the the contingency fuel to your max landing weight figure ( or any other method that suits ) and load fuel accordingly ? I appreciate that on any given day the loadsheet and the reality may well differ to some degree as it concerns the actual fuel burn. The former is obviously based on the planned situation. Clearly if the situation results in a fuel saving such that the max landing weight would be exceeded then that needs to be addressed to rectify the situation en-route. 1.The aircraft hasn't been operated illegally since the initial consideration would be the max take off weight. The fuel burn en-route can only be an estimate and can be modified as necessary to ensure the max landing weight is not exceeded when that landing actually takes place. 2.The loadmaster has falsified an official aviation document how ? The captain is responsible for signing the document and liasing with the dispatcher. If he decides it is acceptable to up the burn and likewise ensures the MLW will not be exceeded what is the problem ? 3. A bit of a nonstarter since the Captain is agreeing to an increased fuel burn the document is not "falsified". So unless this theoretical accident was as a result of actually landing overweight it would hardly seem relevant. The main reasons for landing at MLW are because the sector length is relatively short or because of a desirabilty to tanker fuel. In the latter case there is little point in tankering to the limit if there is a reasonable chance of then having to burn off any fuel saved. A reduction to the tankered fuel would be sensible and justified in these circumstances. In the case of a MLW restriction that limits payload then that would only be an issue at the planning stage, since arriving with too much fuel would become apparant during the flight and the relevant action taken during the latter part of the cruise or descent.
 1st Jun 2006, 18:22 #5 (permalink) Thread Starter   Join Date: May 2006 Location: High in a tree... Posts: 14 Contingency fuel Ok Bealzebub, here's the deal. I run a plan for say a 6 hour sector, requesting max payload to land at MLW. The system gives me my payload, say 70,000 kgs, and tells me my trip fuel, something like 62,000 kgs, of which contains the expendibles, i.e burn fuel and taxi fuel. What is left in the tanks after landing is the alternate fuel + 30 min hold fuel at alt , also the 5% contingency fuel, which typically would be around 2,500 - 3,500 kgs. The Jepp system calculates that this conting fuel is burnt, but as stated earlier it is not burnt. So we will land 3,000 kgs overweight. Even though the burn fuel is approximate, by increasing the burn on paper by 3,000 kgs is a falsification of a document, and is morally devious which ever way you look at it. If it wasnt an issue, why wont the Capt sign the loadsheet when it shows the a/c to be landing 3,000 kgs over the MLW? And, by the way we are still at the planning stage here, so this is avoidable if we offload frt to equal the weight of the conting fuel. Finally, having dicussed this with many Capt's, I can assure you that it is often almost impossible to burn off the extra fuel en route, also very impracticable. Are you going to request a lower fl to burn more fuel ? are you going to put your gear down with 100 miles to run ?, I dont think so. I know for a fact that there have been many, many overweight landings because of these circumstances..................
 1st Jun 2006, 20:34 #7 (permalink) Join Date: Jun 2001 Location: UK Posts: 1,179 Maybe I've missed something in the above but, as contingency fuel is 5% of the trip fuel, after the trip fuel has been used (ie. the end of the trip) there's no need for it to be there so, in computer flight planning terms.....it isn't! At the end of the trip other reserves come into play and contingency fuel is history. In reality if you are planning to land at/near max landing weight, you need to bear in mind that your contingency fuel probably will/might still be in the tanks.
 1st Jun 2006, 20:43 #8 (permalink) Join Date: May 2006 Location: Manchester Posts: 55 Our computer generated flight plan show the 5% contingency fuel on arrival. I have always worked on the policy that this fuel is a buffer should you need it. Why not get Jeppesen to amend your programme to show the 5% contingency on arrival, which is normally the case. I have no idea what type of aircraft you are flying, as a matter of interest how is your landing speeds calculated ?
 1st Jun 2006, 21:16 #9 (permalink) Thread Starter   Join Date: May 2006 Location: High in a tree... Posts: 14 Congintency fuel (ok, a glass or red going down nicley...) Thanks for replies guys. I don't think i'm making my point as clear as I should be. Will come back at a later stage, please watch this space. Regards.....
 2nd Jun 2006, 09:07 #10 (permalink) Thread Starter   Join Date: May 2006 Location: High in a tree... Posts: 14 Contingency fuel......... The fuel burn is estimated by the Jepp calculation with the given A/C limitations, met conditions, sector time/distance, alternate info, and payload requirements. When the Capt instructs the LM to increase the burn by the weight of the conting fuel, he is only doing it so he doesnt have to sign a loadsheet which shows an overweight landing. I take your point about ways of actually physically increasing the burn en route to bring the A/C to within limits for landing, but I can assure you that this never happens and there are no intentions to do so. So the A/C lands overweight at destination. This always happens when we request max payload to arrive at MLW. Also, you have touched on re clear planning, again that option in this situation is never considered. The only time a re clear is considered is when we try to run a payload request on the Jepp system and it wont allow the requested payload because of sector length. Frt is never offloaded as long as the Jepp plan shows the A/C operting within limits, but of course this comes back to my original argument that the Jepp system assumes that we burn the conting fuel when we actually dont. Finally, reports are never ever submitted concerning an overweight landing.
 3rd Jun 2006, 08:44 #13 (permalink) Per Ardua ad Astraeus   Join Date: Mar 2000 Location: UK Posts: 18,603 As bealzebub and Schmoogle said, the MTOM calculation SHOULD take that all into account on the loadsheet, so if your 'loadmaster' is not doing that he/she will trip up in any case at the loadsheet stage - and should be shot or hung by the neck. In my experience most trip plans assume cont to have been burnt at touchdown. In any case most wise pilots always reduce trip fuel by x% for MLW calculations anyway in case the route is shortened or winds/levels are BETTER than planned so as not to arrive 'overmass' as I believe I have to call it now
 4th Jun 2006, 23:21 #14 (permalink) Join Date: Sep 2005 Location: ??? Posts: 209 Schmoogle u as the pilot give the LM the loadsheet info. so it is up to u as the pilot to provide them with the correct trip fuel figure so that exceeding MLW will not be a problem. ie if 5% is included into the trip fuel calculated by ur program then minus 5% from the trip fuel figure that u give to the LM. So that if u dont burn it u will land at MLW and if u do burn it u will have more of a margin over it. Ie plan on the safe side.
5th Jun 2006, 05:13   #15 (permalink)

Join Date: Oct 2004
Location: 3rd Rock from the Sun
Age: 55
Posts: 33
Quote:
 Originally Posted by Schmoogle When using the Jeppesen flt planning system to calculate max payload, fuel required for given payload etc. Why does the system assume that the 5% contingency fuel is burnt by the time you arrive. The fact is that this fuel is a buffer of extra fuel in case the situation arises where you might need it, but if this situation doesnt arise, then you arrive at your destination with it still in the tanks. If you are arriving at max landing weight, the reality is that you are arriving at your max landiing weight, plus the weight of the contingency fuel. In other words an overweight landing, which could be several tons over your max ldg wt. This is concurred when the loadmaster completes his loadsheet, where the maths don't lie. His loadsheet in this case will show an overweight landing...

We use the Jeppesen Flight Planning system at my airline. I've read through most of this thread, and have to apologize if I offer some redundant information, as I got a little lost in all the postings.

The Maximum Landing weight calculated in the Jep System is the Take-off weight, minus the "Trip Fuel" and "Taxi Fuel". The "Route Reserve" (Contingency) is included, along with the Alternate and final reserve fuel in the landing weight computation, and is assumed to NOT be burned during flight.

In the Airbus there is a simple test to prove this. In the FMS (MCDU) INT-B page, set all the fuel parameters as indicated on the Jep Flt plan (Trip fuel and alternate are computed, but normally the same as the Jep System), and the others can be manually entered.

Then, read the landing weight with a 5% route reserve. Now, set the route reserve to 0% and read the landing weight. It will indicate No change to the original weight, but the "Extra Fuel" available will show an increase.

This was confirmed when I asked a dispatcher to run two flight plans for the same route, but with different Route Reserve (contingency) settings. 5% and 0%.

Not sure why you have different numbers on your load sheets though. Possibly your Jep Sys, and Load Planning System are not configured in a compatable manner.

Hope this simplifies the answer for you.

Cheers

 21st Jun 2006, 12:59 #16 (permalink) Only half a speed-brake   Join Date: Apr 2003 Location: Looking for a job ... Age: 40 Posts: 1,816 Our Jepp planning show landing fuel as final reserve + alternate + full contingency. Whether it had been modified to do so, I do not know. But that is the way it works. What strikes me is the large amount you describe. If you are a JAR-OPS operator, I believe you can at least halve the figure by using either "en-route alternate" or "pre-determined decision point" scenarios. I believe other OPS regulations have similar provisions. If this is wise, I would rather not comment neither am I a commander to do so. FD. (the un-real)
21st Jun 2006, 13:03   #17 (permalink)

Join Date: Oct 2004
Location: 3rd Rock from the Sun
Age: 55
Posts: 33
Quote:
 Originally Posted by FlightDetent Our Jepp planning show landing fuel as final reserve + alternate + full contingency. Whether it had been modified to do so, I do not know. But that is the way it works. What strikes me is the large amount you describe. If you are a JAR-OPS operator, I believe you can at least halve the figure by using either "en-route alternate" or "pre-determined decision point" scenarios. I believe other OPS regulations have similar provisions. If this is wise, I would rather not comment neither am I a commander to do so. FD. (the un-real)
I guess I missed that point in my previous post. Yes, ours does the same thing.