explanations for tailwind takeoff

[hu]

Hello;
Is there any can explain how does the tailwind affect aircraft performance, flight path, pitch angle, and control techniques on tailwind(let say 8kt tailwind component) takeoff and land?many thnks!!

[Tinstaafl]

A tailwind will increase the take-off & landing roll, reduce the climb gradient (but not climb rate) leading to obstacle clearance complications. If strong enough may be limiting due to tyre speed limits during take off & landing. If really strong the tailwinds may cause handling complications during taxi such as weather cocking.

Turbine engines are often sensitive to tailwind components during start.


Many a/c performance charts allow for take-offs & landings up to a certain tailwind component eg 5 kts.





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[RatherBeFlying]

So once you've had an exciting low level tour of the opposite end of the runway, you will then find an increasing tailwind as you climb, which will decay your rate of climb until you regain your lost airspeed.

Wind gradient is good when taking off into wind and hell on your climb gradient when taking off downwind.

Tinstaafl is correct in stating that your rate of climb does not deteriorate in a steady state tailwind , but wind normally changes with altitude, especially in the first couple hundred feet, where there might be objects you need to get over:eek:

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...and can affect the RTO on a balanced runway.

[Young Paul]

Wind gradient may be important - but the wind might drop off or veer as you get airborne anyway.

Few aircraft are certified for >10kts tailwind. That doesn't stop airports like eg BRU transmitting a wind of 080/14 kts and a runway in use of 25 from time to time.

The fundamental problem is airspeed versus groundspeed. You take off at (say) 140 kts. With a 10kt headwind, this is a groundspeed of 130 kts. With a 10kt tailwind, it's 150 kts. The difference in kinetic energy between the two is substantial (a ratio of about 1.45). There is also a substantial amount of additional concrete required to accelerate that additional 20 kts of airspeed. Also, in the event of an RTO, all the extra energy has to be absorbed by the brakes - and the aircraft is being pushed along by the tailwind during the deceleration.

[Captain Stable]

RatherBeFlying, I think you're confusing rate of climb with angle of climb and airspeed with groundspeed.

[RatherBeFlying]

Captain Stable, I left out some details in the interests of brevity; so, here's a longer explanation.

Assume you have just lifted off with maximum power in a downwind takeoff, have attained best angle of climb and while climbing you traverse a windshear boundary and the tailwind increases 20 kt.:(

To regain your airspeed and best angle of climb, you must accelerate that 20 kt and will likely have to lower your nose. While you are accelerating back to regain airspeed, both your angle and rate of climb will be decreased.

Angle and rate of climb will be decreased during the acceleration segment; after the rate of climb will be restored and angle will be the resultant of still air angle plus a correction for the increased groundspeed.

[hu]

So the flight path will be shallow compared with the headwind takeoff, am I right? does the tailwind affect my pitch angle?

[Captain Stable]

No, hu. Pitch angle is dictated by your airspeed. Flight path is dictated by your groundspeed.