Holding pattern wind corrections/timing?
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Holding pattern wind corrections/timing?
Hi guys i am carrying out my IR Revalidation soon and have forgotten parts on how to carry out the wind correction angle and timing for the hold
I'll take an example to see if i am right are if anyone can correct me on this;
Say the holding winds where 065/30kts and i am looking to hold on the 119R. So first find the difference between 119 and 065 being 55 degrees and from the drift clock that i have, i can see that 55 degrees is approx 90% of wind speed which is 27kts therefore outbound would be a heading of 92? are would it be 27/2 = 14 therefore an outbound heading of 105? not quiet sure whether you divide this or not?
I think i remember you divide it by 2 for inbound and not to divide it for outbound and is it if the winds 30 degrees are more off the heading this affects your calculation also?
As for timing do you take the new wind corrected heading to calculate how much the wind is off your heading are would it just be calculated from the 119R? Say i take the wind corrected heading of 105, from my timing clock/graph that is 40 degrees difference and approx 85%, so 85% of 30 is 25 and as its a head wind the outbound time would be 1:35 sec is this right?
Thanks
I'll take an example to see if i am right are if anyone can correct me on this;
Say the holding winds where 065/30kts and i am looking to hold on the 119R. So first find the difference between 119 and 065 being 55 degrees and from the drift clock that i have, i can see that 55 degrees is approx 90% of wind speed which is 27kts therefore outbound would be a heading of 92? are would it be 27/2 = 14 therefore an outbound heading of 105? not quiet sure whether you divide this or not?
I think i remember you divide it by 2 for inbound and not to divide it for outbound and is it if the winds 30 degrees are more off the heading this affects your calculation also?
As for timing do you take the new wind corrected heading to calculate how much the wind is off your heading are would it just be calculated from the 119R? Say i take the wind corrected heading of 105, from my timing clock/graph that is 40 degrees difference and approx 85%, so 85% of 30 is 25 and as its a head wind the outbound time would be 1:35 sec is this right?
Thanks
Join Date: May 2005
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Hi,
Where you doing the reval? The instructor will be able to tell you what to use...
edited:
take about half the crosswind for drift. You can use the formula
max drift = 60 x WIND/TAS if you want to work it out a bit more accurately, but you'll see for most light twin speeds, halving it works well.
For hold IAS of about 130kts, I was taught:
For a small hold (<4nm) use 3 times the drift outbound and 1x drift inbound (or in reality, just get on to the inbound track and hold it).
For a large hold (>4nm) use 2 times the drift outboud and 1x drift inbound.
For outbound timings:
add 1 second for every kt of headwind. subtract 1 second for every kt tailwind. For the tailwind case I'd almost be inclined to not take off much time - sure your timing will be out a bit but it will give you more time to get back onto the inbound. The holds are designed for fast jets so a 130kts twin prop is not likely to get outside the protected zone in this case!
Good luck,
Where you doing the reval? The instructor will be able to tell you what to use...
edited:
take about half the crosswind for drift. You can use the formula
max drift = 60 x WIND/TAS if you want to work it out a bit more accurately, but you'll see for most light twin speeds, halving it works well.
For hold IAS of about 130kts, I was taught:
For a small hold (<4nm) use 3 times the drift outbound and 1x drift inbound (or in reality, just get on to the inbound track and hold it).
For a large hold (>4nm) use 2 times the drift outboud and 1x drift inbound.
For outbound timings:
add 1 second for every kt of headwind. subtract 1 second for every kt tailwind. For the tailwind case I'd almost be inclined to not take off much time - sure your timing will be out a bit but it will give you more time to get back onto the inbound. The holds are designed for fast jets so a 130kts twin prop is not likely to get outside the protected zone in this case!
Good luck,
Last edited by Darth_Bovine; 30th Jan 2013 at 08:16.
