ROC question

[mickypitch]

Hi I have this question that I need the explanation to if possible:ugh:

An a/craft has a gradient of 3.3% flying at IAS of 85knts at a pressure Alt of 8000ft temp 15 degrees will have a rate of climb of ??

I have the answer of 334Ft/Min

What is the formula to get there?
I have tried ROC= V sin Y but do not get 334

I need someone to help me see how to get to this figure.
Cheers

[Alex Whittingham]

Did you work out the TAS?

[HN1708]

1 in 60 rule do it? I'll find me whizz-wheel and have a go!

Converted IAS to TAS, then converted the gradient of 3.3% to and angle of 1.98 degrees, then worked out the distance gone in 1 minute as feet, then transposed it into the 1 in 60 rule and came out with 331ft/min, which is fine if the possible answers are far enough apart!

Perhaps the long way round, but proves how handy the 1 in 60 is ;-)

[mickypitch]

Hi I did work out the TAS using the 8000/1000 + IAS = 93knts
but I really need talking through the figures to understand it.
Cheers

[Flying Wild]

Using a CRP-5, set 8000ft against +15C. Then look at the inside scale for 85kt IAS. This gives you approximately 99kts TAS.

Then, using the 1 in 60 rule:

(Height/Distance travelled)x100=Gradient in %

so: (Height/10032ft)x100=3.3% (you get 10032ft from (99/60)x6080)
Height = (3.3/100)x10032
Height = 331ft - near enough to your given answer.

[mickypitch]

Hi thanks for this I think the 1 in 60 rule is close enough to the answer.
Appreciate the replies.
Cheers ::O