Engine3firehandle

12th Jul 2007, 09:04

Hi,

I first posted in the wrong forum...

now here is hopefully where the Performance Gurus are hidding. :)

I got the following question and I am still a little puzzled about it.

If you got a flatrated engine ( as most engines are nowadays ) and you are doing T/O calculations, your data will give you most probably a flex Temp and a V1 Vr and a V2 speed.

now there are two formulas:

1. Per each 10 degrees difference between OAT and Flex you got 3% more stopping distance then calculated out of the TAS ( True Airspeed Speed ) Effect.

( A high Flex Temp at 40 degrees and an OAT of actual 10 degrees brings an 9% margin on the Accelerate Stop distance or was it the TOD ?

That was the first question.

2. The other rule of thumb is: Per 1 degrees celsius Delta between Flex Temp and OAT, you got another 10m more stopping distance.

What if you got a high elevation (3000ft, engine is flatrated 32 degrees and the Flex Temp is 60 and the OAT at 3000ft is 9 degrees C )

That would mean another 510 meters stopping distance. Is this correct ?

From 60 to 29 is the Flex Range. ( At higher GW the Full T/O thrust has to be used )

Might it be only the 31 degrees times 10 meters ? so is it a plus of 310meters stopping distance ?

---------------------------------------

So is this correct ?

you FLEX on T/O and got an OAT of 10Celsius and your calculated FLEX is 60.

Now the stop margin shows 2 meters only.

But you got a margin actually from about 500meters due to the TAS effect.

So you brief for RTO we got a stop margin of 502 meters.

This is common practice in my company and I am not sure if this is o.k.

Any ideas ?

I first posted in the wrong forum...

now here is hopefully where the Performance Gurus are hidding. :)

I got the following question and I am still a little puzzled about it.

If you got a flatrated engine ( as most engines are nowadays ) and you are doing T/O calculations, your data will give you most probably a flex Temp and a V1 Vr and a V2 speed.

now there are two formulas:

1. Per each 10 degrees difference between OAT and Flex you got 3% more stopping distance then calculated out of the TAS ( True Airspeed Speed ) Effect.

( A high Flex Temp at 40 degrees and an OAT of actual 10 degrees brings an 9% margin on the Accelerate Stop distance or was it the TOD ?

That was the first question.

2. The other rule of thumb is: Per 1 degrees celsius Delta between Flex Temp and OAT, you got another 10m more stopping distance.

What if you got a high elevation (3000ft, engine is flatrated 32 degrees and the Flex Temp is 60 and the OAT at 3000ft is 9 degrees C )

That would mean another 510 meters stopping distance. Is this correct ?

From 60 to 29 is the Flex Range. ( At higher GW the Full T/O thrust has to be used )

Might it be only the 31 degrees times 10 meters ? so is it a plus of 310meters stopping distance ?

---------------------------------------

So is this correct ?

you FLEX on T/O and got an OAT of 10Celsius and your calculated FLEX is 60.

Now the stop margin shows 2 meters only.

But you got a margin actually from about 500meters due to the TAS effect.

So you brief for RTO we got a stop margin of 502 meters.

This is common practice in my company and I am not sure if this is o.k.

Any ideas ?