Hi,

Would yous please help me with the following?

In summer an aerodrome’s Density Altitude is 4060 ft with ISA of +7°C.
In winter the same aerodrome’s DA is 3060 with ISA of +9 °C.

How do I decide which one is the ‘worst case’ season?

A detailed answer will help me to have some more knowledge. I am new to this course

Quick question - can you check for a typo - is the summer deviation intended to be +17 ?

Either way, the summer case is the more critical for performance as it results in the higher DH.

thank you for the answer

but how did you end-up getting +17?

DA = 4060 and I have rounded that to 4100 ft
so, 15 - (4.1*2) = 6.8 round that to +7. isn't it?

am I doing something wrong?????

There seems to be something wrong with the question (unless it's a 'trick' question).

The question gives two DENSITY HEIGHTS. Therefore the temperatures are irrelevant since temperature is already considered in determining density heights. DH 4060 is a worse case than DH 3060.

Note also that 'density height' and 'density altitude' are interchangeable terms.

My apologies - I misunderstood your first post to be referring to ISA deviations. Suggest you rework your calculations starting with pressure height rather than density height.

As to whence the 17 degrees - that was based on the above presumption.