Expert: Capt Paul - 6/5/2004

Question
Respected sir
How are you? I am Faisal nazir flight dispatcher from Pakistan, as you remember, you given me easy and straight answer of my questions many times before.
Today,I want to ask some questions about takeoff performance of an aircraft.

We normally use runway regulated takeoff gross weight charts (RTOGW) to calculate performance limited takeoff weight.in this chart we find TREF (temperature refrence) or flat rating temperature and TMAX (temperature maximum) or maximum certified temperatuere.i want to know what is TREF and TMAX,and what is diffrence between them.and what is its importance during calculating RTOGW?

My 2nd question , we find codes limitation on the top of this chart.for example,
1 for structure , 2 for 2nd segment , 3 for rwy OEI  and 4 for obstacle etc.
when an aircraft is limitied by code 2 and 4 at a certain weight,what is it mean?

What is felexible take off?

Soonest reply of above questions will be apriciated.
Best regards
Faisal nazir
Flight dispatcher.
Airblue
Karachi, Pakistan.  

Answer
What types are aircraft of you dealing with, and different types have different references.  

Without this information, I will be guessing at the answer.  That said, I think you will find that TMAX is a hard number, and is the Maximum temputature that the aircraft can operate in.

TREF, is probably a "Conditional" tempurature used to extend engine life, and reduce operating costs.  

Airbus Industries used a maximum tempuature, and a "Flex" tempurature.  Flex is a tempurature assumtion, used for the purpose described above.  

Let me know what types of equipment you are operating, and I can better answer.

Cheers