Zero wind

[ollycopter]

Hi all,

I recently had a captain get rather cross because I calculated Take off distance using zero wind when we had a light headwind (not more then 10kts). We were not take off field limited in anyway and were light. The captain informed me that doing this could kill us.

I understand fully that if we are take off field limited then using headwind for the calculations is required. I know many operators allow for zerowind calculations and its acceptable. I also know its still at the captain's descretion.

Is using zerowind in a headwind situation illegal? Will a ramp check be a problem in this instance?

Any feedback or articles on the matter would be appreciated

Thanks

Copter

[Gin Jockey]

I would suggest Captain X re-assess his understanding of a threat to his operation and look in the mirror.

Surely logic would suggest that using less headwind in a calculation than is actually present results in less de-rate and therefore more thrust. So to suggest that using less headwind in a reduced thrust calculation than is actually present and "doing this could kill us" shows a distinct lack of understanding of the principles of a reduced thrust take-off.

Using less headwind in calculations and therefore more thrust would result in a more conservative operation. Hardly something which a "ramp check" would have a problem with.

Also if you use nil-wind and you get out to the runway in a light wind situation and the windsock is limp, you won't need to rip out your performance manual at the threshold and re-calculate your thrust.

[SNS3Guppy]

He's the captain, and thus you're best doing as he requests. However, that said, calculating for calm conditions when you have a headwind means that you've planned for extra runway. If anything, your calcualtion is conservative, as a headwind will reduce the actual takeoff roll from what you've planned.

How one could arrive at the conclusion that making a conservative calculation will "kill" you is somewhat of a mystery.

[ollycopter]

I know. I discussed the matter and gave my point of view, and then went along and calculated the figures with the actual wind. Its not a very synegistic cockpit.

[TheGorrilla]

Grief... you should have said "if you want performance with actual wind, go ahead, CALCULATE IT YOURSELF!". Then see what expression he makes, let the old fart turn red.

[hoover1]

i rarely ever use winds in my calculations. if it is that close where you need a couple hundred pounds then i will. but a couple hundred pounds on a 737 is not going to kill anyone.my lack of piloting skill accounts for more that a couple hundred pounds over. nobody can fly the plane like the book demands it. the captain is just trying to show you that you do not need to be smart to be a captain just an asshole.

[TheGorrilla]

No, a little pragmatism/common sense/mutual respect(?) would help. I'd suggest the captains job is to look at the bigger picture, to identify real threats. Personally I can't get worked up about the Qnh dropping by 1 or 2, the temperature rising by a degree or two either.... When I've got 4000m of tarmac infront of me. 1300m then i'll be paying attention.

Bet the guy still took off with a de-rate?

[ollycopter]

Nah, we fly a C-750. We did take off with the actual wind calculations, but lets just say we had more than enough runway before I started opening the manuals again.. The best bit Cap wanted me to calculate distance for departure from our destination airport with weather that would be a good few hours old come departure time. Its kind of a long story really. Every flight a new story. Same Cap thinks the EPGWS function fries peoples nuts on the apron.. Wont listen to reason.. No maybe thats the best part

[Cloud Chaser]

Certainly no danger of killing yourselves! As the others have said, rounding down the wind (ie reducing a headwind and increasing a tailwind) is increasing the safety margin and for that reason, is the way it should be done.

Only possible defence for the Capt I can think of is, if the headwind was say 7 or 8kt and you had data for 5kt, you should really have used that, since flexing whenever possible will same your company money in terms of fuel burn and engine wear. {Some people think that if you can only derate a little, why bother. Fact is it's the first few percent that make the biggest difference.}

Regarding using data a few hours before you were ready to go, were there any issues with wanting as much fuel as possible or a heavy payload, and wanting the figures early to work out how much fuel to order?????

With the EGPWS, can't think of any problem with that. Usually only the weather radar you have to be careful with (that does fry peoples nuts!!). Don't think a EGPWS test would affect that, but no experience of Citations so can't say for certain.

[BelArgUSA]

Hola ollycopter -
xxx
Your takeoff computation was more conservative. Do not see anything wrong.
I personally only included wind, if/when we needed extra for heavy weight.
Other thing as an example... for temperatures.
Suppose we compute a takeoff at noon, but the 11:00 ATIS gives 10ºC.
Nothing wrong to use 12ºC, assume a likely increase in temperature. Again, conservative.
Tell your captain... sorry - it is a bad word.
xxx

Happy contrails