A question for 604 pilots please
Thread Starter
A question for 604 pilots please
6 months ago I started as a skipper on a Challenger 604. I have a few concerns but one which is a bit more concerning to me than the others regards fuel indications.
We often fly the aircraft to the full extent of its range so fuel management obviously becomes a concern. The issue I have is this - and I know it may have been addressed by a software change, but not on my beast.
At any stage I can obviously lookt at my screen and see my fuel remaining. If I then go into the FMS and put Flight Plan Progress up on my nav display I get all the waypoints with their predicted fuel remaining, or, if I have already passed the waypoint, its actual fuel remaining. This figure is taken from fuel flows so should be fairly accurate, if not spot on. I have been diligent in inserting all winds and ISA temps - both from the forecst and the actual observed.
Problem I have is huge discrepancies between what is showing on my fuel guage screen at each waypoint, and what Flight Plan Progress is showing. As we fly they do come back closer together, but in the first few hours of an 8 and a half hour flight it is quite concerning. The discrepancy has been as high as 900lb, but generally it is around 600 or so.
This will become of real concern to me should I go to an island type destination with limited enroute alternates. Coming back to home base not such a problem, but if I ever show less than 30 minutes reserve on one of them, which one is actually correct. Coming home, if both the guage and the flight plan progress look grim, I drop into an alternate for fuel.
My last trip home resulted in a landing with flight plan progress showing a bare 1000lb, but the guage showing 1700lb on arrival.
So beyond the obvious of trusting the more pessimistic of the two, I am wondering if anyone else does or has experienced this. Is the guage accurate, should I trust the flight plan progress? Was there a software mod which fixed this?
Any help much appreciated.
We often fly the aircraft to the full extent of its range so fuel management obviously becomes a concern. The issue I have is this - and I know it may have been addressed by a software change, but not on my beast.
At any stage I can obviously lookt at my screen and see my fuel remaining. If I then go into the FMS and put Flight Plan Progress up on my nav display I get all the waypoints with their predicted fuel remaining, or, if I have already passed the waypoint, its actual fuel remaining. This figure is taken from fuel flows so should be fairly accurate, if not spot on. I have been diligent in inserting all winds and ISA temps - both from the forecst and the actual observed.
Problem I have is huge discrepancies between what is showing on my fuel guage screen at each waypoint, and what Flight Plan Progress is showing. As we fly they do come back closer together, but in the first few hours of an 8 and a half hour flight it is quite concerning. The discrepancy has been as high as 900lb, but generally it is around 600 or so.
This will become of real concern to me should I go to an island type destination with limited enroute alternates. Coming back to home base not such a problem, but if I ever show less than 30 minutes reserve on one of them, which one is actually correct. Coming home, if both the guage and the flight plan progress look grim, I drop into an alternate for fuel.
My last trip home resulted in a landing with flight plan progress showing a bare 1000lb, but the guage showing 1700lb on arrival.
So beyond the obvious of trusting the more pessimistic of the two, I am wondering if anyone else does or has experienced this. Is the guage accurate, should I trust the flight plan progress? Was there a software mod which fixed this?
Any help much appreciated.
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Hi Trevor
From memory, the numbers you see when airborne are only a comparison to the "predicted" figures that are calculated by the box when you first program it on the ground.
The + or _ numbers you see when in the air are + or _ the amount the box calculated / predicted, you would have had at that waypoint before you started engines.
So in theory, if you input all of the "planned" information when you first program the box, the numbers should be more accurate when you are in the air as then the box is comparing the actual wind, temp deviation and fuel flow to what you told it was likely to be the case when you were sitting on the ramp, drinking coffee.
If you don't get the flight level when airborne you told the box you were going to get when you were on the ground, the numbers kind of become meaningless until you do get the level..
Also unless there has been a software change, (or memory failure on my part) in the perf init pages, there is nowhere to enter step climbs and the box cannot "predict" a change in flight level down route, so for very long flights, there will always be a discrepancy when you begin the flight as the box on the ground assumed the whole flight would be at say FL350.
(I'm really scratching around the memory banks now but i think that if you change the flight level on the legs page at the waypoint you would arrive at first at the new altitude after a step climb, the box assumes the whole flight will be at that (new) level......can't remember now)
As we know, garbage in..... garbage out and being just as likely to punch a wrong button as the next man, using a jepp plan gave me peace of mind as i could compare Mr Jeppesen's results with Mr Collins's results and if they were within 200-400 lbs of each other, we celebrated and did all the high fives, slappin' each other on the back s**t!!!
We did have to (default) bias the jepp plan quite a bit though but after 12 years on the aircraft, i think we got it about right.
Was taught at a young age, plan the flight, fly the plan. Just looked in my logbook, longest flight i did was 8.3 airborne time, Dubai to Farnborough and that was more than enough for my sphincter. Landed with 1,700 Lbs according to the notes. It was definitely Miller time after that.
Hope that helps.
GW
From memory, the numbers you see when airborne are only a comparison to the "predicted" figures that are calculated by the box when you first program it on the ground.
The + or _ numbers you see when in the air are + or _ the amount the box calculated / predicted, you would have had at that waypoint before you started engines.
So in theory, if you input all of the "planned" information when you first program the box, the numbers should be more accurate when you are in the air as then the box is comparing the actual wind, temp deviation and fuel flow to what you told it was likely to be the case when you were sitting on the ramp, drinking coffee.
If you don't get the flight level when airborne you told the box you were going to get when you were on the ground, the numbers kind of become meaningless until you do get the level..
Also unless there has been a software change, (or memory failure on my part) in the perf init pages, there is nowhere to enter step climbs and the box cannot "predict" a change in flight level down route, so for very long flights, there will always be a discrepancy when you begin the flight as the box on the ground assumed the whole flight would be at say FL350.
(I'm really scratching around the memory banks now but i think that if you change the flight level on the legs page at the waypoint you would arrive at first at the new altitude after a step climb, the box assumes the whole flight will be at that (new) level......can't remember now)
As we know, garbage in..... garbage out and being just as likely to punch a wrong button as the next man, using a jepp plan gave me peace of mind as i could compare Mr Jeppesen's results with Mr Collins's results and if they were within 200-400 lbs of each other, we celebrated and did all the high fives, slappin' each other on the back s**t!!!
We did have to (default) bias the jepp plan quite a bit though but after 12 years on the aircraft, i think we got it about right.
Was taught at a young age, plan the flight, fly the plan. Just looked in my logbook, longest flight i did was 8.3 airborne time, Dubai to Farnborough and that was more than enough for my sphincter. Landed with 1,700 Lbs according to the notes. It was definitely Miller time after that.
Hope that helps.
GW
Last edited by Global Warrior; 2nd Aug 2010 at 01:36. Reason: Added more text
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601 viewpoint
This was always the problem, never matching the FMS and real fuel.
In general the fuel gty gauge is more accurate. However they took perhaps 10 mins to settle down following refueling.
So we would set the FMS to the eventual gauge fuel quantity.
Get to TOC, and thern reset the FMS fuel qty, to match gauge fuel.
In the 601, the L and R fuel gauges would wander up and down, and show imbalance at start of cruise, but mostly when left alone would rebalance themselves before TOD.
We had biased data set for planning, so mostly had no major errors on fuel remaining. BUT there was still always a 500Lbs or so extra fuel on board after landing.
Currently on G550, the FMS learns more about the aircraft, but still we are 500Lbs or so up after landing based on even our TOD estimates. Progress.
glf (x 601)
In general the fuel gty gauge is more accurate. However they took perhaps 10 mins to settle down following refueling.
So we would set the FMS to the eventual gauge fuel quantity.
Get to TOC, and thern reset the FMS fuel qty, to match gauge fuel.
In the 601, the L and R fuel gauges would wander up and down, and show imbalance at start of cruise, but mostly when left alone would rebalance themselves before TOD.
We had biased data set for planning, so mostly had no major errors on fuel remaining. BUT there was still always a 500Lbs or so extra fuel on board after landing.
Currently on G550, the FMS learns more about the aircraft, but still we are 500Lbs or so up after landing based on even our TOD estimates. Progress.
glf (x 601)
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FMS Fuel vs Tankindication
Quote: Get to TOC, and thern reset the FMS fuel qty, to match gauge fuel.
This is not allowed in a CL 604 !
(Check AFM section 2 Limitations)
I'm not sure about the 601 that you refer to, but the original question is about the 604
regards
mj
This is not allowed in a CL 604 !
(Check AFM section 2 Limitations)
I'm not sure about the 601 that you refer to, but the original question is about the 604
regards
mj
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I first started to fly the 604 in 1999. It has always had this issue, in fact the 605 has the same issue. I have also flown the G-IV and it does not have the same issue as it has a fuel sensor that feeds how much fuel you have right to the FMS, while the 604 and 605 do not, what you tell the box is what it assumes you have and then bases the numbers on the PPH burn rate.
When I fly the 604 or 605, what you have to do is this. When you first set-up the FMS, you need to put how much fuel you have in the performance page. No matter how exact you are, it never keeps up, plus if you are on the ground for a few hours running the APU, the number will be wrong anyways if you did not change it. What you need to do is at cruise altitude, go to the performance page, and adjust the fuel number to match what you actually have in the tanks, the big reason to do this, is so that it can compute the correct REF Landing speed for you. You should check this every hour.
This should solve your problem
When I fly the 604 or 605, what you have to do is this. When you first set-up the FMS, you need to put how much fuel you have in the performance page. No matter how exact you are, it never keeps up, plus if you are on the ground for a few hours running the APU, the number will be wrong anyways if you did not change it. What you need to do is at cruise altitude, go to the performance page, and adjust the fuel number to match what you actually have in the tanks, the big reason to do this, is so that it can compute the correct REF Landing speed for you. You should check this every hour.
This should solve your problem
Thread Starter
Thank you guys, I appreciate your efforts very much. Thanks so much.
Global Warrior - thanks so much for your detailed response - I'm not so much concerned by the plus or minus figures on the FLT PLAN Progress page, more the actual number. The number at the waypoint passed shows I was at that point with, say, 10,200lb. And it will say + or - a few hundred. As I say I'm not too concerned about this aspect. What I am concerned about is that the number will say at waypoint SNOTTY I had 10,2000 lb, but on the fuel guage it showed 11,000lb. So its the difference betwen what the box said I had at the waypoint and the guage. I understand that the + or - is based on a prediction. I just need to know when I get to a waypoing and the box says I have 10,200lb left but the guage says 11,000 lb, which is right?
Batsky 2000 - thanks to you also. If at TOPC I put from the gauge the fuel figure into the PERf page, do you think the fuel flow sent to the box, plus this new figure, will now have my FLT PLN Progress fuel figure at a waypoint more accurately matching the guage.
Gotta say it - this is my 7th jet and I've never seen such a pathetic fuel system - fuel venting issues, no ability to set a refuel figure on a dial and then walk away and come back when it has reached that level, having to wait up to 8 minutes for fuel guages to read accurately post refuel, ie can't just say we'll stop it when the guage gets to the right level. I have an advisory wire which adresses fuel venting - just stop filling each wing 500 lb short of full (or something like that - don't have it with me right now). Well thats great when you need to fly 8 hours or more. Just short change yourself fuel. Thats not a fix - ar5e they joking.
Thanks again guys.
Global Warrior - thanks so much for your detailed response - I'm not so much concerned by the plus or minus figures on the FLT PLAN Progress page, more the actual number. The number at the waypoint passed shows I was at that point with, say, 10,200lb. And it will say + or - a few hundred. As I say I'm not too concerned about this aspect. What I am concerned about is that the number will say at waypoint SNOTTY I had 10,2000 lb, but on the fuel guage it showed 11,000lb. So its the difference betwen what the box said I had at the waypoint and the guage. I understand that the + or - is based on a prediction. I just need to know when I get to a waypoing and the box says I have 10,200lb left but the guage says 11,000 lb, which is right?
Batsky 2000 - thanks to you also. If at TOPC I put from the gauge the fuel figure into the PERf page, do you think the fuel flow sent to the box, plus this new figure, will now have my FLT PLN Progress fuel figure at a waypoint more accurately matching the guage.
Gotta say it - this is my 7th jet and I've never seen such a pathetic fuel system - fuel venting issues, no ability to set a refuel figure on a dial and then walk away and come back when it has reached that level, having to wait up to 8 minutes for fuel guages to read accurately post refuel, ie can't just say we'll stop it when the guage gets to the right level. I have an advisory wire which adresses fuel venting - just stop filling each wing 500 lb short of full (or something like that - don't have it with me right now). Well thats great when you need to fly 8 hours or more. Just short change yourself fuel. Thats not a fix - ar5e they joking.
Thanks again guys.
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Trevor,
Yes, if you keep updating the fuel on the performance page where you originaly entered it when you did your preflight, you will have a very acurate figure when comparing your trip sheet fuel burns. You just need to keep looking at it every hour or so just to make sure it is the same as your tank guage, if not, put in the correct amount plus a little, like 50 pounds just as a buffer, you will see that you will end up with a more acurate readout in the end.
Yes the fuel venting thing is a big issue, it is worse in the 605. I too have flown many other jets and this is the only one that I have ever flown that has a fuel venting issue. I have more time in Gulfstreams, and never have either one of these issues, or in the BBJ that I fly, but that is just the way the Challenger was built, people love them because of the wide cabin, but to me it is one of the slowest jets I have ever flown, i am sure with your 8+ hour legs, you must slow it down to .75 or less to get the range, super slow, even the BBJ LLC is .78.....
Oh Well, it still pays the bills, right.....
Enjoy
Yes, if you keep updating the fuel on the performance page where you originaly entered it when you did your preflight, you will have a very acurate figure when comparing your trip sheet fuel burns. You just need to keep looking at it every hour or so just to make sure it is the same as your tank guage, if not, put in the correct amount plus a little, like 50 pounds just as a buffer, you will see that you will end up with a more acurate readout in the end.
Yes the fuel venting thing is a big issue, it is worse in the 605. I too have flown many other jets and this is the only one that I have ever flown that has a fuel venting issue. I have more time in Gulfstreams, and never have either one of these issues, or in the BBJ that I fly, but that is just the way the Challenger was built, people love them because of the wide cabin, but to me it is one of the slowest jets I have ever flown, i am sure with your 8+ hour legs, you must slow it down to .75 or less to get the range, super slow, even the BBJ LLC is .78.....
Oh Well, it still pays the bills, right.....
Enjoy
