ILS with a Tailwind
 

There are a lot of small controlled airports out there (even some uncontrolled ones) that have an ILS serving only one runway. Let's say the minimums are low (right around 200 and 1/2) but the wind is favoring the opposite runway. To what extent (in terms of tailwind), considering the airplane being flown, would you try to negotiate with tower to push for a straight-in landing to get in, if at all? I am just curious what others out there would do in this situation, since it isn't really an uncommon scenario.

The controllers at the airport understand approach minimums and tailwinds. If there is only 1 approach that is going to get you low enough to land (even with a tailwind) that's probably will be the one you'll be assigned when you check in with approach. If not, just ask they'll accommodate you.

This is not all that uncommon anyway. This happens at DCA all the time. Weather is too low to make it in on any of the 19 approaches, so they'll land and depart on 1 with a tailwind. Some of the larger aircraft can't takeoff on 1 with the tail wind so they'll launch against the traffic flow on 19.

Potomac Approach controllers build enough of a gap in to accommodate runway 19 departures with only a short delay. It helps that DCA Tower and Potomac Approach have mad skillz. Best ATC I've ever seen hands down and that includes NYC and ORD (nothing against those guys though).

If the tower is trying to "sell" the winds to favor a runway I'm biased to go the alternate. More than 5 knots (AFM limit) I'm outta there since in your WX scenario circling isn't an option.

Usually the airports I fly into there is not much negotiating. They are landing what they are landing and thats it. With that being said..I will accept a runway with a tailwind providing it is within the aircraft limits and we can get landing numbers that provide the appropriate safety margins.

If we start having to work magic to make it happen then it is time to go to the alternate. JFK loves a good tailwind of max limit crosswind.

If only there was this thing, that maybe I could use to predict landing distance, corrected for variables like a tailwind or headwind..... Then if landing distance was greater than available ruwnway I could make an educated decision.

Anyone want to invent such a thing? We could call it something off the wall, like "landing performance chart". Or "distance". We'll discuss details later.

A lot of landing distance charts/tables for light aircraft don't even account for a tailwind. Either you have a table with 0, 5, 10, 15 mph etc headwind or a percentage correction factor to the distance that is only meant for a headwind. This is similar to the situation where you're taking off from airports in the mountains with density altitudes in excess of 8,000 ft or so. The takeoff distance chart typically only goes to 7,500ft or so DA. You can use those Koch charts or whatever in that case....but the moral of the story in either case is that you are venturing outside the numbers of the POH.

Yes, for larger aircraft you will typically have a chart as opposed to a table that can account for either a headwind or tailwind, but just because some aircraft have it available doesn't mean that all aircraft have it available. Then again, I'm assuming you were being serious. If you were being sarcastic, I recommend you take a look at some actual takeoff/landing distance charts for different aircraft.

be a butt about it

If you decide to do this, also be aware of the difference that you will likely experience on the approach itself. Things will be happening at a different pace coming down the glideslope with such a higher groundspeed and the ROD will not be what you are used to seeing either while you are scanning your instruments. All of this together could be a factor in being stabilized for the approach to landing. I was shooting some ILSs the other day with a nasty tailwind and it was a little bit of a battle down the chute. I'm glad I wasn't in the weather and having to break out and land!

USMCFLYR

I've flown planes from a cessnas, piper, BE400, T-37, C-5, C-17, B737, and 757/767. A 10 knots tailwind has always been a limit of some sort. Don't let some folks here talk down to you. You asked a very realistic question. Also, big planes don't use "charts" for takeoff and landing data.

Also something to think about...if the weather is truly at mins (say 200 and 1/2) the chance the wind is blowing more than 10 knots is small. Typically when weather is that low winds are bill.

I hope this helps. Feel free to PM me.

You mentioned that it happens at some smaller controlled field. Chances are if it is actual IFR (since you NEED to use the ILS) it is probably not going to be super busy. Maybe a few corporate jets coming and going. Don't buy into too much of they "If they are landing one way, that's all there is to it." If you need an approach to get down to mins to get on the ground, do it! They should have an idea with the weather. If tower is reporting OVC003 and one way has an ILS and the other a VOR only only good to 600', they should know that only one of those approaches is going to be useful.

A lot depends on the situation. If I was in a light single shooting an ILS to a nicely sized runway, I probably would take the tail wind up to 10 or 15 knots. I would be hesitant to go much over that. A rule of thumb is what ever the distance that headwind saves you, give up that amount times THREE in tail wind. IE if a 15 knot headwind saves you 400 feet, assume it will take 1200 feet EXTRA to land.

The other thing you might have to worry about is wet runway. If the weather is at mins, you could be dealing with wet or damp runways which may affect your breaking. Couple that with a tail wind you could be looking at really using up a lot of runway distance. Make sure you really hit your touch down zone and not try to make a greaser.

Finally before I step off the CFII soap box, winds will probably be stronger aloft and lighter near the surface. So they may be 10 knots or so at the surface but could be as high as 50 knots at the marker. A light single doing 80 knots needs roughly 400fpm no wind. Add 50 knots, you need almost 700 fpm. If you are not used to that it could be easy to get above and stay above glide path. Then as you get closer you try to correct, over correct (especially when the beam gets narrow, say, at mins) and, well...

tl;dr - tell tower what you need. give yourself plenty of extra landing distance. realize your descent rate will be different and will change throughout the approach.

Sarcasm detector inop?

Correct re: takeoff data.

Incorrect re: landing data.
We use landing data tables about 95% of the time on the MD-11. Go in with your landing weight and you get an approximate landing distance based on final flaps, wet/dry runway and up to 10 knots of TW.

Certain situations preclude using the quick ref data like: high OAT, high altitude airport, low vis, runway conditions worse than wet or MEL restrictions on systems needed for landing. In these situations we are required to use the computer program normally used for takeoff data.

I detected it, didn't I?

SARCASM:

1. harsh or bitter derision or irony
2. a sharply ironical taunt; sneering or cutting remark