RSV Fuel and FD ON Ils approach

[bluestrip]

Hi all i have a question about Reserve fuel.

I usually just hang around the forum and read some topics, most of which i learn a lot. Im not an airline pilot yet, just a PPL and currently work as an ATC, so please dont bash me about being a flightsim pilot and call me a troll.

Ok so lets take the MD80 for example. I've read that once total fuel quantity reaches 5000lbs, you will get a Low Fuel level alert on the EOAP. Now, lets say for example that on a particular day, 45minutes reserve fuel is 3000lbs, and alternate fuel and all the other stuff such as go around at altn and blah blah amounts to 1500lbs and trip fuel is 15000lbs.

Question is, when dispatch does the fuel planning, would the total fuel required at pushback be:
15000 - trip (incl taxi)
+1500 - Altn and blah blah
+3000 - 45 Min Rsv.
=19500lbs at pushback and 3000lbs total minimum at landing at altn.

Or, would the 5000lbs that would cause the low fuel level alert be added to the calculation to make the total at pushback 24500lbs and 8000lbs total minimum at landing at altn.


second question i heard 2 people debating about which got me thinking.
On the Airbus, if the AP are disconnected at say 300ft RA when LAND green, and the FDs and ATHR are left on, what would the FMA revert to? Would it remain in LAND or would it change to TRK/HDG VS/FPA?

thanks for your answers

[Double Hydco]

The FMA continues to read LAND, and reverts to Cat1. If it's still got a valid ILS signal then the FD will remain coupled.

DH

[bluestrip]

@mig3
So does that mean, that its OK to intentionally go below 5000lbs total fuel quantity?

@Double Hydco
If the FMA continues to read LAND and the ATHR remain ON, does it mean then at the appropriate height the autothrust will still retard the thrust automatically, or will it still remain in SPEED mode?

[Checkboard]

You're welcome on this forum as a sim pilot, with a genuine curiosity - as long as you are honest enough to admit you are a sim pilot :ok: People are only put down if they attempt to claim experience they don't have.

Your flight (I'm on the 737, forgive the differences):

15000 lbs trip
+ 750 lbs contingency
+ 1500 Alternate
+ 3000 Final reserve (30 mins, in my company)

Gives a Block fuel of 20250 lbs (which is what you would tell the refueller to load).

You would expect to arrive at your destination with 5250 lbs, a bit more with short cuts, a bit less with weather manoeuvring.

You would set your FMC fuel alarm at 4500lbs - the minimum to divert to the alternate. The aircraft low fuel alert in the 737 triggers at either 907kg/tank or 453 kg/tank (depending on the modification). Say it's 907kg (times 2, times 2.2 lbs/kg =) 3990 lbs.

Now say you arrive, and are given unexpected holding. Once the FMC predicts the fuel at arrival at the runway is below 4500 lbs, it will trigger a "Using Reserve Fuel" message. For this to be accurate, you must have correctly programmed the hold (including the Expected Approach Time), and expected vectoring after the hold. At this point (actually well before this point!) a decision has to be made about which airport you must commit to - commit to destination, or commit to a diversion on minimum fuel. At my company an Air Safety Report is also required - so we are now into having to complete extra paperwork (something every pilot tries to avoid!)

Let's say you decide to commit to the destination. I would reset the FMC alert to "final reserve + 100 or 200 kg."

Continue to hold, and at 3990 lbs the aircraft low fuel level will annunciate - this is a QRH procedure to ensure all of the remaining fuel can be used - turning on pumps, opening crossfeeds and the like.

Continue to hold, and the FMC annunciates "Using Reserve Fuel" again! :eek: Again, given correct FMC route programming, it now looks like you may use your final reserve (may, due to the added 100/200kg above) - this warning is a mandatory "PAN PAN PAN" urgency call to ATC for priority vectoring.

Continue to hold, or get poor vectoring, and it now is definite you will use final reserve fuel - this is a mandatory "MAYDAY" call - and a trigger for me to first stress in the strongest possible terms I need a direct route to an immediate approach, or in the final instance, to force the issue by flying a direct route, with a general broadcast to other traffic (ie ignore ATC).

[bluestrip]

Checkboard

That answered my fuel question perfectly and then some! Thank you very much!

[Checkboard]

You're welcome. :)

[Double Hydco]

No, in manual flight the autothrust will require you to reduce thrust to idle, although it gives you a "retard" call at 20'. So, if you flare at the appropriate point but leave the thrust levers in the CLB detent, the thrust will come up to maintain the speed.

During an autoland the thrust will automatically reduce to idle, but still gives you a "retard" reminder at 10' to remind you to set the thrust levers to idle.

DH