Tailwind landings

[rt777]

Situation:

You are a new CPL, flying an IFR 172 into a fairly large airport with a runway over 5000ft long. It only has a precision approach to one side of the runway, and the cloud cover is at 500' AGL. There currently is a steady 5kt tailwind directly down the runway for the precision approach. Since circling or a visual is out of the question, you must land with the tailwind.

What do you do? How will the tailwind change your approach and landing?

Totally hypothetical, but I am curious to hear what people say.

[DanWEC]

Oh boy, you asked this question in the right forum. Variable tailwinds? Wait for it... Waiiiiit for it.....

[GyvAir]

Oi..

[lownslow]

As long as five knots off the tail is fine by the POH, I'd expect to use a touch less power on glideslope than usual and I'd be aware of the illusion of a higher airspeed once I'm visual. No big deal, really.

...Unless those tailwinds were variable, then I'd probably start to panic. I've heard they're the cause of nearly every accident ever.

LnS.

[rt777]

Oh boy, you asked this question in the right forum. Variable tailwinds? Wait for it... Waiiiiit for it.....

Whats wrong with the question if you don't mind me asking?

[DanWEC]

Oh boy, you asked this question in the right forum. Variable tailwinds? Wait for it... Waiiiiit for it.....

Whats wrong with the question if you don't mind me asking?

Nothing at all, in reality a good question- but relates to a source of an esoteric running chuckle on this forum for a while. Lownslow alluded a bit to it.

Now... outside of this intraweb thing, you may find yourself a little high on GS. Keep an eye on A/S, the approach will look fast once visual. Expect to use a lot more runway obviously.

Cheers,
dc

[Airmanship Police]

Once those steady tailwinds start to vary, turn off your transponder and inflate your swimaids!!

[Colonel Sanders]

5 kts of tailwind is nothing for a 172
on a 5000 foot runway. I would be quite
happy with a 20 knot tailwind in a 172
on a 5000 foot runway. Expect to see
a bigger number on the VSI on the ILS.

Most people approach far too fast anyways.

Before the white shirt/gold bars start their
harrumphing ...

It doesn't matter how fast you fly the ILS.
Faster is less boring.

As far as taking a 20 knot tailwind on touchdown,
airspeed on a 172 should be around 65 knots
over the runway threshold. With 20 knots of
tailwind, that's only 85 knots of kinetic energy
for 5000 feet of pavement. That's slower than
I approach a C421 at, and MUCH slower than
the 125 knots for an L39, both of which I land
on 4000 feet.

I remember doing an airshow in Honduras,
we did head-on takeoffs and landings, I had
the 20 knot tailwind for both.

[complexintentions]

Is there a published limitation for a C172 for tailwinds?

My only tip would be to monitor your technique in the flair to ensure you don't float, as the higher G/S will use up runway faster but 5,000 feet at C172 approach speeds still seems like plenty.

[Colonel Sanders]

Read this carefully:



From a practical standpoint, what would matter
is nosewheel shimmy from lowering the nosewheel
at too high a speed, which is what most people
do in a 172 anyways.

[complexintentions]

I WAS gonna ask, "what are the other variables" in my initial post. High/hot/heavy? But I didn't know if these were particularly limiting on a Cessna. They sure don't appear to be on a 5,000ft runway. So my answer to the original poster would be, I don't see a problem whatsoever, as long as you are operating within your personal experience and comfort limits, there should be no threat to safely landing.

Technique aside, is there a specified speed below which the nose wheel should be lowered?

Chart attached for those who might be interested in the contrasting distances for the other end of the weight spectrum. It does help illustrate the effects of higher temperatures and elevations. Even now I'll occasionally fly with someone who doesn't fully respect the effects on TAS and accompanying higher descent rates.

(Distances are in metres.)

[Colonel Sanders]

is there a specified speed below which the nose wheel should be lowered?

172S POH says on p 4-42:

The main wheels must touch the ground before the nosewheel. The nosewheel must be lowered to the runway carefully after the speed has diminished to avoid unnecessary nose gear loads.

[GyvAir]

What are the physics/math behind the headwind/tailwind numbers?

Take the first line in 777 chart:
10 knot headwind = 40m shorter landing than in calm air.
but a 10 knot tailwind = 130m longer landing than in calm air.

The ratio is even greater for other configurations in the chart... the C172 numbers, even more.

Why does a tailwind make a landing so much longer than a headwind will shorten it?

Aviation Safety Letter 1/2005 Wind at Your Back - The Hidden Dangers of Tailwind
https://www.tc.gc.ca/eng/civilaviation/ ... 4-2901.htm

[Colonel Sanders]

http://en.wikipedia.org/wiki/Kinetic_energy
is a function of velocity SQUARED.

I think you are assuming linear.

[rt777]

Ok makes sense, now with CAR 602.96,3.(e): "where practicable, land and take off into the wind unless otherwise authorized by the appropriate air traffic control unit", does this mean if ATC clears you to a runway with a tailwind, and you accept, you are now clear of this regulation?

[GyvAir]

http://en.wikipedia.org/wiki/Kinetic_energy
is a function of velocity SQUARED.
I think you are assuming linear.

Ah yes, I was. Thank you.
The old story that hitting the oncoming truck is going to hurt way more than twice as much as hitting the wall.

[Colonel Sanders]

where practicable, land and take off into the wind

Note "where practicable". Even without ATC
authorization (eg at an uncontrolled airport)
this is done all the time.

For example, you might have a short runway
which is directly into wind, and a faster, heavier
aircraft chooses to take a longer runway with
a crosswind. CYGK with a west wind.

Other times I have chosen tailwind:

- uphill/downhill
- obstructions at one end of the runway
- setting sun
- as OP mentioned, instrument approach
with lower ceilings. Circling not possible.

[Rookie50]

I actually did an inadvertent 10 knot tailwheel landing recently on a long runway, because the MF gave me the wrong winds -- or there was a heck of a last minute shift. Anyway it was a long runway, which is good as I was also high for traffic, and it was likely a 20 knot tailwind at 1000 feet, which means I used half of it. Floated awhile at idle, then checked the windsock after, 10 knot tailwind.

No biggie, but anymore would be an issue for me as the RG has quite small tires, and doesn't appreciate high runway speeds at all. Me thinks a quartering 15 knot tailwind would get real interesting in my bird.

[Liquid Charlie]

Obviously one does not intend to set yourself up to do a downwind approach but unless you always have the choice of being a fair wx pilot (which is not a bad thing if you a hobbyist) - having said that you should know your airplane for the day you might get caught and being in mind the circling approach is likely one of the most dangerous procedures. Most aircraft have 10 kts and the odd one 15 kts tailwind as max in the limitations -- I suggest you know what you can land downwind you can handle (hang the hand book) maybe even up to maximum wind you would consider to go flying in especially if you don't have optional runways handy to divert to --

A tragic example happened in Frob many years ago -- a DCC3 landed downwind of the ILS - no issues -- a Twin Otter decided to circle because of the tailwind and killed 9 people in a CFIT --

[cgzro]

No biggie, but anymore would be an issue for me as the RG has quite small tires, and doesn't appreciate high runway speeds at all. Me thinks a quartering 15 knot tailwind would get real interesting in my bird.

I used to be deathly afraid of tailwind landings until I watched CS effortlessly doing them which seriously pissed me off so I set out to try some and frankly apart from the longer landing and higher speeds they were a non event. Ive been up to 20 mph tail wind in a teeny squirrelly S1 and even quartering its not outrageously hard but it does require concentration. My mains are tiny, and are 4 feet apart and a wheel landing is 90 mph or so, so thats 110mph GS with 20mph tail wind ... great sport

[x-wind]

For the poster. Landing with a tail wind is harder on the aircraft mechanically. The slower the landing the easier it is on the aircraft. It's should be a small part of the consideration.

[oldtimer]

Other than the extra stress on the tires and brakes, I found I had the most challenging was when the airplane slowed to taxi speed. Mind you this was not serious and it was with a taildragger but I found this is when a pilot will sometimes let his guard down and could get a bit of a surprise. Just remember to keep flying the airplane until the last piece stops rotating.

[complexintentions]

Great point oldtimer. The flight isn't over till the thing is tied down or chocked.

Also Rookie50 brings up another good point, tire speed. Lots to consider. But I'd still take a small tailwind on a straight-in ILS over a circling approach, statistically speaking.

Oh and the B777 perf charts incidentally, are only there as a backup, the landing performance is usually done with the Onboard Performance Tool, or OPT. Basically a customized laptop. I do know that the OPT only considers half of the headwind component you input, but all of the tailwind. Conservative. I would imagine the paper charts are the same, so could also explain the discrepancy of why the tailwind is so penalizing but the headwind isn't as helpful.

[Colonel Sanders]

There are three very different kinds of limitations:

1) real limitations of the airframe/engine which
are determined by the laws of physics courtesy
of Sir Isaac Newton et al;

2) limits determined by lawyers and bureaucrats

3) limits of the pilot's ability to fly the aircraft

When the chips are down, it's nice to know which
limitations you are dealing with. You might have
guessed that I am not a big fan of #3. Try really
hard not to be the weakest link.

At the risk of getting screeched and honked at here,
sometimes you have to disregard #2, as well. See
Liquid Charlie's Twotter fatal circling choice.

[MaximumAmazing]

Doesnt this belong in the flight training forum?