Bob3
Short answer:
With a tailwind an aircraft will not flare so well, will be harder to keep straight during the initial part of the roll out and will take a lot further to stop
Long answer:
The effects of landing in a tailwind all stem from the extra speed over the ground.
BEFORE touchdown we need to remember the increased kinetic energy of the aircraft that will be present. The increased KE will, thanks to Sir Isaac Newton, mean that the aircraft is (marginally) less manoeuvrable for any given input. For pilots used to the IAS/TAS issues where at high altitude aerodromes the same effect is happening (flying usual IAS but higher TAS therefore more inertia) it will represent little more than a need to recognise the aircraft will be a tad more sluggish – especially in the flare. HOWEVER, inertia effects are of course V squared jobs, so with a Vref of say 140 with a headwind of 25 kts the inertia effects are related to 140 minus 25 = 115 which when squared is 13225. With the same 25 kt wind up your chuff the inertia effects are related to 140 plus 25 = 165. When this is squared we get 27225 i.e over a 100% increase when compared to the into wind case. Such an increase as that will certainly come through in the handling as a marked lack of response compared to what one is used to.
AFTER landing the higher ground speeds will (thanks to the same inertia business) mean the aircraft will be more reluctant to steer as accurately as you are used to at lower speeds. Again it will appear sluggish (or a bit as if the R/W is slippery).
I’m sure we don’t need to remind ourselves that all the extra KE will thrash the tyres and brakes when it comes to stopping, unless you really do have a LOT of length to spare.
Finally, for completeness there are tyre limiting speeds. But these are more likely to get into the high AUW high altitude take off case than during a fast touchdown.
Bottom line, there are some potential handling aspects to downwind landings that may need to be thought about as well as the obvious stopping issues.
JF
[This message has been edited by John Farley (edited 07 November 2000).]