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## working out headwind or tailwind

• boeing777mark
• Topic Author

### boeing777mark created the topic: working out headwind or tailwind

Hi Rich and Bob

In the VFR day study guide on page1.2.14 question 12 it mentions that the wind is 350*M at 15kt, now i am aware the its either a head or tail wind but how do i work out if it is a head wind or tail wind, do i have to use a whiz wheel or is there another technique...

Kind Regards
Mark

• Posts: 1169

### Richard replied the topic: Re: working out headwind or tailwind

Hi Mark,

The wind is northerly (i.e. blowing from 350 degrees) and we have a choice between runways 18 and 36. Since the wind is nearly blowing straight down the runway at 15 kts we can't use runway 18 since that would mean we would have nearly 15kt of tailwind for take-off. Apart from the fact this exceeds the downwind take-off limits for the aircraft, why would you use runway 18 when there's a perfectly good into-wind runway? So, you would use runway 36 in this example.

To find out your headwind component you can estimate and say "The wind is only 10 degrees off the nose if I am lined up on runway 36 so I have all the wind as a headwind". However, the more accurate way would be to use the wind component tables in ERSA GEN-CON 6. There you'll find the headwind component is actually 14 kts. Not much different to our estimate.

So when you are looking at these kinds of questions, consider the wind strength and direction versus the runway direction to decide which runway you should use. Watch out for questions with light winids of up to 5 kt and a runway slope. In those cases, sometimes it is better to take-off downhill with a slight tailwind than to takeoff uphill with a headwind. If you are faced with a sloped runway and light winds it would be a good idea to check take-offs (or landings) in both directions.

Cheers,

Rich

• boeing777mark
• Topic Author

### boeing777mark replied the topic: Re: working out headwind or tailwind

Hi rich

Thanks so much for the quick response, have a better understanding now.

Appreciate the help mate.

Kind Regards

• Claw

### Claw replied the topic: Re: working out headwind or tailwind

Hi Richard, I understand the theory behind working out the Headwind/Xwind components and relating to the same pages that Mark is working on, I just want to know if I have got it right or is it a typo error in the BAK VFR book. Exercise 12.2 on page 12.15 it gives the example of RUNWAY 04/22 WIND 070 at 10kt .
The answer given is Use Runway 04 with a Crosswind of 7 kt from the Right.
Shouln't the answer be Runway 04 with a Crosswind of 5kt from the right.

Regards
Claw

• Posts: 1169

### Richard replied the topic: Re: working out headwind or tailwind

Hi Claw,

Well spotted! Your answer is correct. It should indeed be 5 kt of crosswind from the right and not 7 kt. Thanks for pointing that out. We'll get it changed in the next update.

Cheers,

Rich

• Claw

### Claw replied the topic: Re: working out headwind or tailwind

Thanks Richard for clarifying that. I am a very mature student(57) with about a dozen lessons under the belt and am enjoying the experience very much. Should have started a bit earlier in life but better late than never. One other point I would like clarification on please in the same publication VFR (DAY)study guide,
Re AIR LAW questions, Question 13 on page 10.31
The Answer given is (b) Before the first flight of each day.
Should it not be (a) Before each flight.
Regards
Claw(Gary)

• Posts: 2103

### bobtait replied the topic: Re: working out headwind or tailwind

Gidday Claw,

The checking of fuel tank vents is listed in the CAR Schedule 5 under daily inspections. So if a question says when MUST they be checked, the answer would be before the first flight of each day. Of course it would be a sensible item to include in a pre-flight check - especially for forward-facing fuel tank vents - but it is not a legal requirement.

Bob