Tailwind component

[OB-5656]

Hello guys! Just a simple question, in my country we have many airports in which we have to operate under tailwind conditions during takeoff, because there is only that rwy available due tu terrain.

My question is that if the gust should be included when finding the tailwind component for takeoff? We are normaly limited to 10kt by boeing or sometimes 5kt due to performance.

Best regards,
Nico

[nbairlines]

In daily ops we use the least favourable wind for our T/O performance calculation, including gust. If this exceeds applicable limits (FCOM/OM-C/ perf.requirements) we stay home :)

[Intruder]

If terrain is a factor, DEFINITELY use any gust component for tailwind! generally, the winds will increase as you climb, decreasing your margins.

[framer]

In my Boeing manual it says to include the gusts. We can take 15kts.

[RAT 5]

Pre-pad performance OPT's the paper tables produced assumed 50% of head wind & 150% of tailwind for their calculations; so I was told by our performance engineer. They didn't mention gusts.
Broadening the discussion slightly, I asked, and never received an answer to what to do with gusts in calculating the allowable tailwind for landing: i.e. the 10 or 15kts limit. Gusts were included in head & cross wind calculations, but not tail. The performance engineer had no answer and over the years of asking the manufacturer it seemed it was up to the airline; who also had failed to provide an answer. Bon Chance. It seemed a grey area was preferable, until you went of the end and then it was your fault.

[OB-5656]

Thanks for the answers guys, i also stay always on the conservative side and prefere to include the gust for my perf limits, unfortanetly my company haven establish any policy and some people does not take in consideration the gust!

Best regards!

[vilas]

RAT 5
Tailwind limits for landing are for steady tailwind. Any gusty tailwind beyond the limit tailwind you shouldn't be landing. There is no cushion of Vref addition for tailwind so it's not safe.

[16024]

Vilas, I'm not saying you are wrong, but that is a sweeping statement.
I'm sure Rat5 is looking for hard evidence to back all that up, and I'm not so sure either, and between us we've probably got 50 years experience. Plus the manufacturer, FCTM and the performance gurus all have slopey shoulders on the subject.
As it goes we use steady wind for perf calculations at our place, at the planning stage at least.

[underfire]

Pre-pad performance OPT's the paper tables produced assumed 50% of head wind & 150% of tailwind for their calculations; so I was told by our performance engineer. They didn't mention gusts.

RAT, wouldnt 150% account for gusts?

[RAT 5]

wouldn't 150% account for gusts?

That's for landing & performance distance calculations. I am looking for legal operational limits regarding gusts. They are there for head & X-winds, but not tail. There are only steady tailwind limits. e.g. RW36. ILS: Wx below limits for circle RW18. W/V 180/14G28. Heavy rain & turbulence. RW36 has 15kt allowance & is extra long. I diverted, others from company landed within 15 mins afterwards. Asked company for guidance on calculating tailwind limits. No answer, save from performance dept.

[vilas]

16024
I am not talking about GA or landing performance but approach itself in tailwind. The manufacturers provide additives only for headwind gust, that even in crosswind caters for headwind component of the crosswind. Can you make an approach with out any additive for gust? Landing in tailwind has authorisation and that only permits you to do so in a tailwind of maximum say 15kts. then to exceed that would require hard evidence and not the other way round. Nobody takes away due credit for the years you can also include me to contribute to that score. Experience alone is not everything as Bangalore, SFO and Air China 747 barrel role suggests.

[underfire]

From FAA 8400.9 NATIONAL SAFETY AND OPERATIONAL CRITERIA FOR RUNWAY SELECTION PLANS AND NOISE ABATEMENT RUNWAY USE PROGRAMS.

10. OPERATIONAL SAFETY CRITERIA FOR RUNWAY USE

d. Maximum tailwind component (including gust)
i. Dry Runway: 10 kts
ii. Wet Runway: 10 kts
iii. Contaminated Runway (< 8000 ft) < 3 kts (reported as calm)
iv. Contaminated Runway (> 8000 ft) 5 kts

Per the FM, the "maximum allowable tailwind component" is just that, maximum...

[safetypee]

Some background reports on the issue.
Tailwind gusts might not be a significant performance issue, but for aircraft handling there could be a few surprises.
Airbus now includes gusts; a point to note and heed their approach to safety.

http://www.nlr-atsi.nl/downloads/safety-aspects-of-tailwind-operations.pdf

http://www.nlr-atsi.nl/downloads/safety-aspects-of-aircraft-operations-in-cross.pdf

http://www.nlr-atsi.nl/downloads/analysis-of-existing-practices-and-issues-rega.pdf

[vilas]

That was exactly what I am saying. The tail wind limit is all inclusive and nothing over and above.