EFFRA

[elpilote]

hi , i am actually looking for informations, explanation about EFFRA.
I can't find a lot about it in my OM, so may be somebody can explane me more about it and also on the cost index.

thanks in advance

elpilote

[Empty Cruise]

EFFRA - or Engine Failure Flap Retraction Altitude - is an altitude between two extremes:

1) Mininmum flap retraction altitude - the lowest altitude where you can accelerate the aircraft to minimum clean speed while still maintaining your engine-out minimum obstacle clearance (35' with turns no greather than +/- 15 deg. - and 50' if turns greather than 15 deg. are needed). This value is typically determined by obstacles relatively near the runway (say, up to 6-8 km. from brake release), but it cannot be lower than 400 ft. AAL.

2) Maximum flap retraction altitude - the maximum altitude where you can still accelerate to clean the aircraft up without limiting your en-route climb performance on 1 engine. This can be limited by engine thrust limitations (5 or 10 min. TO thrust) or distant obstacles.

Typically, you company will choose a standard altitude for this purpose that is lower than max flap retraction altitude on all the airports on its route network, and higher than minimum flap retraction altitude on most airports. To make life simpler, many companies also choose an EFFRA that will co-incide with the normal 2-engine flap retraction altitude, normally limited by noise abatement. So you often come across the figures 1000' or 1500'.

Cost index - without becoming too theoretical, you can view total operating cost as made up of three different "parts" - fixed cost (cost per flight, e.g. airport & passenger charges, airway charges, insurance, overheads for administration, some maintenance such as items overhauled by cycles or dates, basic crew pay & pensions and flat rate leasing costs), variable cost (cost per flight hour, mostly maintenance that runs per flight hour, and "power-by-the-hour"-leasing - and finally fuel.

Fixed cost is best recovered by flying as fast as possible, since more rotations can be fitted into the schedule per day, but there is an upper limit to the gain, especially if up against slot allocation numbers, so most of the time only moderare speed increases can be justified. The principle of less airborne time also goes for variable cost, since fewer hours are spent in the air, and therefore less money has to be paid. Fuel, on the other hand, cost you more thefaster you fly (above LRC).

The cost-index therefore reflects the total of these expenses. When fuel prices are high (like nowadays), the CI tends to be low = we fly at a speed not much above LRC. If on the other hand your company has a raw deal on a chartered aircraft, the variable cost is so high that you need to minimise the airborne time, and therefore you'll operate this aircraft at a higher CI (= we fly a good deal above LRC) than the rest of the fleet that the company perhaps owns.

Hope this helps - cheers!

[elpilote]

thanks for your answer,
for cost index i will try to resume t be sur i anderstand it in the right way.

for Fixed cost: the more your fly ( as many rotation as possible), the cheapest it will be

for variable cost: the les airborne time you have the best it is.

CI= fixed + vairable costs

--> .... i don't anderstand very well your conclusion so may be if you can explane me it in an other way i would understand.

thank you very much


elpilote