Cheers mate I failed my first ppl because I forgot how to do weights and balances and weather got 65% the seconded time I got 68% I new it but silly mistakes ... I will sit it again in 2 weeks agrrrr I've done all your ppl cyber exams 68%72%90%65%68% ...
Man so stressful one day I'm happy the next day I feel like I don't know it ...up down up down....I've noticed on a few of your cyber exams for example you will have a distance from one place to another on WAC I've measured it and the minimum is 92nm and yet yours will have 87nm I can't remember the Questions but some are way out with your WAC distance from one town to another...anyway I am praying I'll pass the next PPL CASA exam.
See ya.

Hi,

just a quick question about the density height drill exercise:

Elevation = 13800 ft, QNH = 1022, OAT = 22 degree celcius. [b]Find Density Altitude.[/b]

I have found the pressure height, but have some problem with ISA temp (negative 12 in answers) and ISA deviation (34 in answers).

Can somebody guide me to the right path?

Cheers ,
Nikita

Hi Nikita,
The -12° is what the ISA temp should be at 13,530' based on the standard lapes rate of 2° per 1000'. So the difference between ISA MSL temp +15° to the ISA temp of -12° at 13,530' is 27°.
The deviation in this question is found by subtracting the ISA temp -12° from the actual, or, ambient temp of 22°. This gives you the answer of 34° deviation.

Hope this helps.

Cheers,
Mister W.

Hi Nikita,

The pressure height is 13530 ft. The expected temperature in ISA at 13530 ft is closest to -12 degrees Celsius (15 - [2 x thousands of feet] = 15 - [2 x 13.5] = 15 - 27 = -12). We have 22 degrees OAT so that means we are 34 degrees warmer than the ISA temperature. Think of a thermometer. Count how many notches there are between -12 and 22 degrees Celsius on the scale.

Each degree of warming has the same "thinning" effect on air density as going up 120 ft in altitude so the temperature reduces the density by [34 x 120] ft or, 4080 ft.

We now adjust the pressure height by 4080 ft to get the final density height of 13530 + 4080 = 17610 ft. That means even though the aircraft is flying at 13800ft, it will actually perform as if it is in air at 17610 ft.

Cheers,

Rich

Ah cross-posted with Mr W 🙂

ISA+34, WOW that's an awful hot day. Looks like global warming is well and truly here!

I think I need to tweak the insanity limits on the Density Altitude Problem Generatoratron...

I used to think of a Beer glass when applying the deviation in density height calculations.

The cold,dense parcel of air at the bottom and the same parcel of air at the top just hotter and thinner and gives us the beer glass shape.
Like all good beer glasses the Australian Hotels Association logo (AHA) is on the side.
AHA stands for:
[b]A[/b] - Air
[b]H[/b] -Hotter
[b]A[/b] - Add

Air hotter than what it should be, I add the deviation.

Cheers,
Mister W.

Thanks for the quick response Mister W and Richard. The beer analogy is easy to remember!

It usually does with Pilots. :laugh:

One more question to the experts:
When doing 1-in-60 exercises I am having a problem to calculate the New HDG after Intercept (M).
For example:
Given
[b]FPT= 273 M, Heading held= 274 M, Distance along Track= 80 nm, Distance off Track = 13 nm left, Distance to re-join Track= 50 nm.[/b]
I have found Track Error= 10 , TMG = 263 , Drift = 11 left, Closing angle = 16, TTI = 289, and HDG to Intercept = 300 M.
I just missing the step of how to calculate the new HDG after Intercept.

Cheers,
Nikita

Hi Nikita,
Now that you have calculated the drift, 11° in this example, you can now apply it to your FPT. This will give you a new HDG which should keep you on track much better than what you originally planned. So we end up with planned track of 273° + 11° to the right = New HDG 284°.

Always found DR nav to be the most fun to do and it has saved my neck more than once when things like GPS and navaids failed.

Hope this helps.

Cheers,
Mister W.

It is clear now
Thanks Mister W 🙂

Hello all,

My first post ever - and hope that there will be many more.

Just on the Pressure Height calculation, I got 13,740. That is 1013-1015 = -2x30 = 60 and 13800-60 0= 13740

How did we get 13510? What am I missing?

cheers