Dipole
30th Jun 2011, 20:21
Refer to CAP 697 MRJT Fig 4.4
Given?
DOM - 35000kg
Expected load - 12000kg
Contingency, approach and hold fuel - 2500kg
Departure aerodrome elevation - 500ft
Alternate aerodrome elevation - 30ft
Find (i) Final Reserve Fuel (Jet Aircraft) and (ii) Relevant Elevation
a. 2360 -- Alternate elevation
b. 1180 -- Destination elevation
c. 1180 -- Alternate elevation
d. 2360 -- Destination elevation
Haven't a clue where to begin... Any help much appreciated!
FlyingStone
30th Jun 2011, 20:46
Appendix 1 to EU OPS 1.255 - Fuel policy
1.5. Final reserve fuel, which shall be:
(a) for aeroplanes with reciprocating engines, fuel to fly for 45 minutes; or
(b) for aeroplanes with turbine engines, fuel to fly for 30 minutes at
holding speed at 1 500 ft (450 m) above aerodrome elevation in
standard conditions, calculated with the estimated mass on arrival at
the destination alternate aerodrome or the destination aerodrome, when
no destination alternate aerodrome is required.
So basically, the final reserve fuel for a turbine aircraft for a normal flight (with selected alternate) is used (should you require it) for holding at 1500ft over the alternate aerodrome.
CAP 697 provides data for fuel flow while in holding (note usually the holding is executed as a some sort of racetrack, so you don't have to reduce the fuel flow for straight-and-level holding). First, we have to calculate our gross mass when in holding overhead alternate aerodrome, which in this case is DOM + Expected load = 35000 + 12000 kg = 47 000 kg. You then check into the tables (interpolate as neccessary), while using pressure altitude of 30 + 1500 = 1530ft. The trick is, you mustn't forget to multiply the fuel flow by time required (half an hour in this case), so you get 2360 * 0,5 = 1180 kg. As said, the final reserve fuel is for holding overhead the alternate aerodrome.
References:
- EU-OPS 1 (http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2008:254:0001:0238:EN:PDF)
- CAP 697 (http://www.caa.co.uk/docs/33/CAP697.pdf)
Dipole
30th Jun 2011, 21:18
Really appreciate that FlyingStone! Good explanation! :ok: