Fuel Burn in NavLog is all wrong

[Airliner]

Okay, in a completely unrelated matter...

This is really confusing me - maybe it's because I'm an idiot - maybe not!

Anyway, using the default flightplanner with FS9, I ran a short flight from KBOS-KMDT. I never paid attention to the NavLog after the flight
before but this time, I decided to check it out. I found this fascinating.

My estimated fuel burn for the entire flight was 857.3 gal. According to the log, my total actual consumed was 1052.8. Okay, so I went a
little over. But here's the thing - on climbout to FL180, I was estimated to burn 215.5 and my actual was 829.1!! HELLO?! It gets better -
I was doing almost 200 knots BELOW the estimated GS for that leg! Even more - For the final 7 segments of the flight, totalling some
124.8 miles, the log reports that no fuel was burned! (From SAX(115.70) all the way to KMDT)

I certainly didn't cut the engines and coast for 125 miles!

Here are my fuel burn values, side-by-side

Est Act
4.0 0.0
215.5 829.1
55.5 95.9
119.0 127.8
117.0 0.0
57.1 0.0
37.4 0.0
111.4 0.0
69.2 0.0
28.5 0.0
42.6 0.0

857.2 1052.8

Curious - I was also getting overspeed warnings but as my GS values were well below the cruising speed of 518kts (I averaged about
425kts, according to the log), how could I have exceeded max? I had the needle pinned for a while which should have been reflected at
least for one leg.

Anyway, the fuel thing is what's bothering me. Any thoughts?

[Ryanamur]

First, don't trust the fuel values of the FS2004 log... for reasons that you've already figured out.

I've had instances were I supposedly would burn 1200# in my Baron and it turned out to be less then 800! That's 50% over.


Now, the overspeed. Grounds speed CANNOT be used as an indication of overspeed. You can only look at your Indicated Airpeed (IAS). If
you have a strong headwind, your groundspeed will go down but you are actually travelling faster through the air. Also, don't forget gusts
and don't forget that your max speed decreases as you go up. So it's quite possible that you would have exceeded it.

[WBHoenig]

Yeah, when flying from KBWI to KLAX earlier today, my usage was just over half of what the NavLog said it would be.

[xvxmatthewxvx]

The fuel planner is terrible.

If I am flying a big airliner it is always wrong. Every single time I have trusted it for using an airliner I always have to make an emergency
landing or if I am flying over the pacific, a crash into the ocean. So when I am using a big airliner I will always add 30% more than it
says. Sometimes 40%.

Heck, the fuel planner would probably say 100LBS would be enough to go to the moon.



Post Edited ( 12-25-05 01:45 )

[ste9889]

ahhh yes, dont we love the flight planner? but i must admit it is funny to see how wrong it is after an FsP flight.

All The Best
Ste

[lightrail]

For a plane I don't know, I take the amount of fuel that is indicated in the Navlog and divide by the number of minutes in the flight, then:

1. for cruise - use this value times number minutes in cruise
2. for climb - Jets, times value by by four; turobo-props - times value by three; props times value by two - all times the number minutes expected in
climb
3. then I add taxi (5-10 minutes or longer if congested airport), hold - 20 min, approach (15-20 minutes usually), alternate - 30 minutes and reserve
45 minutes

After using a plane for a while, I use the fuel burn per minute shown in the FS Passengers log as an end ot end fuel burn including taxi and approach
(all planes need to climb and desend, so it averages out) - and then add the, hold, alternate and reserve at the same rate.

Beware that the FS fuel calculations can be way off - I've ran out of fuel because of it, even after doing the above.

[Airliner]

Okay, I think I may receive the "kick me" award for this one!

I was in my settings yesterday and noticed a box ticked which I thought I'd unticked - UNLIMTED FUEL!

DOH!

I guess THAT would account for the several legs of zero fuel burned on the report - there was none! And since it wasn't an FS
Passengers flight, I never received the low fuel warning.

So the fuel planner is NOT all that bad - it reported accurately. I just need to check my settings.