I have my CPL flight test coming up and I'm a little confused about the calculated approach speed that the FTG makes mention of. Am I to simply take 1.3 Vso and convert that KCAS into KIAS?

I don't understand the note in the FTG:

1.3 Vso KCAS (max gross wt) x Root(landing wt/gross wt) = 1.3 Vso KCAS (predicted landing wt)

I don't know which terms in brackets are just notes and which terms I'm supposed to actually substitute in the number it represents.

Can someone provide me an example?

Cheers.

If I remember correctly, this is using a 172.

Vso KCAS @ max gross wt is 44kts (right outta the poh)
max gross =2300lbs
landing wt = 2100lbs for example purposes

1.3 Vso KCAS (max gross wt) means 1.3 X 44 = 57.2
Take that 57.2 X Root(2100/2300) = 55KCAS

1.3Vso is you minimum approach speed at gross wt. This converts it into the speed for your intended landing wt.

AUGER9 wrote:If I remember correctly, this is using a 172.

Vso KCAS @ max gross wt is 44kts (right outta the poh)
max gross =2300lbs
landing wt = 2100lbs for example purposes

1.3 Vso KCAS (max gross wt) means 1.3 X 44 = 57.2
Take that 57.2 X Root(2100/2300) = 55KCAS

1.3Vso is you minimum approach speed at gross wt. This converts it into the speed for your intended landing wt.

Ah! Thank you very much! That makes all kinds of sense now.

Let me try and help you out.

First of all, in the decades I have been flying not once have I seen a mark on the AI showing 1.3 anything.
Not once. Blue lines, red lines, all sorts of things. And, as the stall speed will change, not only with power and flap settings, but with weight and C og G, this kind of calculation is simply a basic error. Also, if the wind becomes a factor, the approach speed will have to be adjusted during the approach phase. Not a time to be playing mental gymnastics.

Use the approach speed GIVEN IN THE POH. (or AFM ).

If you are asked on the flight test how to calculate it, tell the examiner you referred to the AFM.

Now, pick an actaul speed. Not something like 71 0r 82 or 117. Use 70, 80, or 120 for example. Easy to scan and much much better to control your speed precisely.

There was a reason, many mnay moons ago for the 1.3 calculation, but I wont go into it here.

Good luck on your flight test

Just remember that you are required to fly the normal landing approach at that speed. I have seen examiners fail students for not maintaining that speed.

Hope that helps you out, if you need to, take your instructor out and practice it.( a good instructor should have covered it all ready. )

Thanks for the help guys. I passed my flight test with flying colours!

Congrats

Now the fun begins

Lurch