PAG

12th May 2018, 13:21

Hi Guys,

There is something I don't get right with Take-Off performance. I fly boeings but I guess it's same for every type. When we use Onboard Performance Tool, it gives us a longer ENGINE INOP GO DISTANCE, with FULL DERATE than DERATE AND ASSUMED TEMPERATURE

Here are some figures from OPT to illustrate:

Airport is RAK, RWY10, DRY, 0 WIND, 15°C, Q1015, Flaps 5, A/C AUTO, A/I OFF

FULL 24K 94.6% V1 138 VR 139 V2 146

R-24K 31°C 93.4% V1 140 VR 140 V2 146

Here is the thing I don't get:

24K MAX TAKE OFF POWER

Engine inop go distance 3051M

ASDR 2069M

all engine go distance 2027M

24K Assumed

Engine inop go distance 2165M

ASDR 2238M

all engine go distance 2210M

How come we need a longer distance engine inop go with FULL than ATM ?

thx for your help

ANSWER:

"With full 24K there is a range of V1 options between v1min and v1max that will satisfy minimum regulatory margins (obstacle clearance, 2nd and 4th segment climb, screen height etc.) The driver for the engine inop go distance is the v1min, in this case 94kts. This means that aircraft will accelerate to 94kts (relatively quickly) and can continue with a longer engine out ground roll to Vr. On the other hand the driver for the ASD is the V1max.

The V1 selection is impacted by the weight and the thrust. With a lower thrust set we are no longer presented with a range of V1 speeds but with V1 speed that will just satisfy both the go case and stop case. (balanced field). So in answer to your question the OEIGD 24K is greater than the OEIGD R24K due to lower V1min.

Ryanair’s policy on V1 selection is OPTIMUM. Optimum gives the return on weight when factoring in available clearways and stopway. For OPT to choose the optimum V1 there needs to be a range of V1 speeds possible "

There is something I don't get right with Take-Off performance. I fly boeings but I guess it's same for every type. When we use Onboard Performance Tool, it gives us a longer ENGINE INOP GO DISTANCE, with FULL DERATE than DERATE AND ASSUMED TEMPERATURE

Here are some figures from OPT to illustrate:

Airport is RAK, RWY10, DRY, 0 WIND, 15°C, Q1015, Flaps 5, A/C AUTO, A/I OFF

FULL 24K 94.6% V1 138 VR 139 V2 146

R-24K 31°C 93.4% V1 140 VR 140 V2 146

Here is the thing I don't get:

24K MAX TAKE OFF POWER

Engine inop go distance 3051M

ASDR 2069M

all engine go distance 2027M

24K Assumed

Engine inop go distance 2165M

ASDR 2238M

all engine go distance 2210M

How come we need a longer distance engine inop go with FULL than ATM ?

thx for your help

ANSWER:

"With full 24K there is a range of V1 options between v1min and v1max that will satisfy minimum regulatory margins (obstacle clearance, 2nd and 4th segment climb, screen height etc.) The driver for the engine inop go distance is the v1min, in this case 94kts. This means that aircraft will accelerate to 94kts (relatively quickly) and can continue with a longer engine out ground roll to Vr. On the other hand the driver for the ASD is the V1max.

The V1 selection is impacted by the weight and the thrust. With a lower thrust set we are no longer presented with a range of V1 speeds but with V1 speed that will just satisfy both the go case and stop case. (balanced field). So in answer to your question the OEIGD 24K is greater than the OEIGD R24K due to lower V1min.

Ryanair’s policy on V1 selection is OPTIMUM. Optimum gives the return on weight when factoring in available clearways and stopway. For OPT to choose the optimum V1 there needs to be a range of V1 speeds possible "