Crosswind 90 degrees. Which Way?

[Grogmonster]

I have a question for all you pilots out there. This question is one I have put to many people and I never get the same answer.

You are flying a high performance American single, ( A36, C210, SR22), or similar. The wind is blowing across runway 18/36 at exactly 90 degrees relative to the runway. Which way would you think it would be safer to take off ????? Assume the wind is just on the maximum demonstrated crosswind limit for your aircraft.

Think carefully before you answer. This old chestnut came up again as a result of the Avalon post that stated that a Mustang had to abort a take off and ended up in the grass off the side of the runway.

I will be watching the replies with interest.

Groggy.

[AerocatS2A]

Assuming the runway is physically the same in both directions (slope, obstacles, etc) then anyway will do. Why do you think one way should be better than the other?

[waren9]

For the singles you mention, I hardly think they face the same issues as the mustang when it comes to crosswind sensitivity from one side compared to the other.

Whats your point?

Give Tim Wallis a call. Im sure he'll have some sympathy for our Mustang pilot today.

[Arnold E]

American or English engine?

[Icarus53]

Takeoff with the wind from the right. I've got at least a 50% chance of getting it right (unless it's a CASA exam in which case there will be a more correct answer because of some grammatical intricacy):{:p


I do actually have a logical basis for my answer but like Grogmonster I'm happy to fish for the moment!:E

[AerocatS2A]

Well sure, if it's a taildragger take-off with the wind working against the torque and slipstream effect, but for a supposedly "high performance" single like a C210 I'd just use the runway that was most convenient. The max crosswind figures don't say "valid for a right crosswind only."

Any talk of torque and slipstream is irrelevant if you're aborting the take-off anyway.

[Roger Copy Ta]

This is a trick question right?

The answer is use 09/27 you bloody idiot! :rolleyes:

[Altimeters]

The only thing that I can think of that Grog may think is a 'trick' would be the fact that on take off in a single we have the slipstream effect. Add to that a xwind from the left and the problem is exacerbated by the aircraft weathercocking even more so to the left. So I think a xwind from the right should even out the slipstream effect.....right? :confused:

[AussieNick]

on a tailwheel with a anticlockwise rotating engine you want a right crosswind, and vica versa for a clockwise rotating one.

not as much of a problem in a tricycle UC

offtopice slightly, how did trappo's P51 fair after its excursion into the ditch?

[tmpffisch]

I'm with Altimeters. May as well use the xwind to counteract the slipstream effect. But when it comes down to it, it doesn't really matter.

Go in the direction you're intending to depart towards?

AV tower was giving the option of either direction today as for a while it was at 90 degrees or so.

[Arnold E]

I'm with Aussienick, hence the question about the engine

[Extra260]

This is a trick question right?

The answer is use 09/27 you bloody idiot!


Ahh... bit hard when someone built a damned shopping mall, 3 car parks and 5 office buildings where 09/27 used to be:bored:

[Joker 10]

So right hand tractor or left hand tractor, which way the engine goes detimines the best way to handle the way the wind blows.

[MakeItHappenCaptain]

If we're talking about a tailwheel, and especially one with such a large rotating mass and arm as a mustang, you'll need to consider both p-effect and gyroscopic precession, both for raising the tail and for rotating.
I would suggest that a clock-wise rotating prop, having a left tending p-effect and precession raising the tail would benefit more from a right x-wind and vice versa. The slipstream effect will exaggerate this before the aircraft accelerates. The take-off rotation would be the lesser consideration.

[ForkTailedDrKiller]

I read recently that "you can run out of rudder taking off in a left x-wind in a V-tail Bonanza"!

I thought that was kinda interesting cause I almost "lost" the FTDK taking off at Karumba in a howling left x-wind - not long after I got it. Closest I have come to bending one.

I got it straight again - so I don't think I had "run out of rudder" - just a once in 30 yr brain fade!

I have taken off and landed the Bo in strong gusty x-winds - can't say I have noticed any difference, but I did flat-spot a tyre last year landing at YTWB in 20kts gusting to 35 - all x-wind. One of those times when being on the ground had much more appeal than being in the air. Fortunately the tyre was due for replacement at the next 100 hrly.

Dr :8

[glekichi]

The direction with the shortest taxi/backtrack! :ok:

[the wizard of auz]

Watch for the occasional gusts and take off into them. they are sure to be one way or the other.

[Lodown]

Having experienced an attempted takeoff with a 'strong' crosswind from the left, as the speed builds on takeoff, you'll very quickly find that right rudder is not required and then shortly after you can't put in enough left rudder to stop the drift to the right. (With a nosewheel, it doesn't feel so much that you run out of left rudder; more that the left rudder just doesn't seem to work at all or still has the rudder lock in place, if that makes sense - in my case, I hadn't got to the point where the nosewheel was off the ground yet and it wasn't going to steer left no matter how hard I pushed). The aircraft will just go further to the right as the speed builds and there is absolutely nothing you can do about it without reducing the power/speed. You'll be in one hell of a bind if you continue with the takeoff: aircraft drifting further from the runway direction and getting a stronger tailwind component at the same time. Abort the takeoff (control comes back very quickly when power is cut), go to the other end of the runway, put the wind on your right and it's a straightforward takeoff. Makes you wonder whether you were imagining things with the wind from the left. Reverse the directions for a Tiger Moth.

Ask a cropduster pilot and they'll tell you the same thing.

Having said this, at max demonstrated crosswind, your aircraft should be able to take off safely in either direction.

[gassed budgie]

As I was skittering sideways in the wet down 18L departing Avalon, the tower decided to let everyone know the crosswind wind component was bang on 38kts. No wonder I couldn't keep it straight!
If he'd been 30 secs earlier with that bit of info, I could have launched right out of taxiway foxtrot, straight across 18L and got the 172 airborne before I got to the other side of the runway!
I might add that the two twins behind me declined the towers invitation to line up and depart.

I read recently that "you can run out of rudder taking off in a left x-wind in a V-tail Bonanza"!

Haven't experienced that before Forky, but I can tell you that with exceptionally strong crosswinds and a forward C of G you can run out of elevator authority in the V-tails. Used to fly KWK a quarter of a century ago and can remember that happening once or twice.

[tinpis]

If we're talking about a tailwheel, and especially one with such a large rotating mass and arm as a mustang, you'll need to consider both p-effect and gyroscopic precession, both for raising the tail and for rotating.


Oh good oh. I'm presented with this dilemma daily when taking the old P-51 out for a gallop :rolleyes:

[Critical Reynolds No]

I did enjoy, after the front appeared, on Saturday with a certain Piper single attempting to land.

Avalon tower: "VH-ABC be advised that the crosswind on Runway 18 is now 36 knots".

VH-ABC: "HALLELUJAH!"

Points for having a go but there was no way. Back from whence he came.

[waren9]

So, whadaya reckon grog? Are we all on the money or are we losers?

[ForkTailedDrKiller]

I can tell you that with exceptionally strong crosswinds and a forward C of G you can run out of elevator authority in the V-tails

I have also read that elsewhere. Don't know about the earlier models, but it would be a challenge to load a V35B anywhere near its forward C of G limit.

Full fuel and Chuckles and I up front get nowhere near it - full fuel and 235kg in the front seats puts you on the forward limit!

Dr :8

[VH-XXX]

This came up for me yesterday when departing from Avalon East with some 15+ crosswind. In my particular aircraft I need a right crosswind versus a left and I was happy to see that 17 was in use. With a left crosswind I get issues with the torque of the engine combined with the left crosswind weather-cocking me into the wind particularly when I lift of the nose wheel early as per normal operating procedure.

[YPJT]

If it is at or just after sunrise or just before sunset: with the sun behind you.:cool: Torque and weathercock issues aside, I'm with Glekichi and his reasoning. The only other one I could think of would be if other traffic are already established in the circuit, you would use the same runway.

[PyroTek]

Now would it be more advisable to be heavy with a crosswind? or Light?
Or does it not really matter? (speaking in loads on light a/c)

[Fr8dog44]

I can't beleive what I am reading here!! Me thinks all of you have way too much time on your hands!!!

Clearly there is both an academic side as well as a "real world" scenario. Give the academic answer on the test and give the interviewer an answer that will save the company money!! It's that simple, don't complicate it! :):)

[b_sta]

How strong are we talking? Strong enough and I'll take off on the runway, facing into the crosswind, Harrier style :}

[Jabawocky]

I got it straight again - so I don't think I had "run out of rudder" - just a once in 30 yr brain fade!

Or just the one.....while taking off in a big X-wind at Karumba :}:E

[Grogmonster]

Altimeters, Arnold E and a few others were right on to it. No trick to it. If you let the wind counter the P factor you will have more control authority especially so in something like an A36 Straight tail or FTDK's V tail. I was just interested to see what you all thought. Thanks for the replies.

Groggy

[Angle of Attack]

The original thread was about a 90 degree x/wind, quite frankly in that case you take off in whatevrer the hell is the most convenient direction to depart! Because there is no difference at all! if its 90 degrees to the runway! Simple really!

[FRQ Charlie Bravo]

Whichever way is easiest to join given your current heading (join midfield crosswind and save time rather than doing a 180 and coming from the "dead side".

Failing that just try to remember which tyre is in the worst shape and spread the wear and tear around between L and R. (OK this one is mostly a joke.)

FRQ CB

[sockedunnecessarily]

The comments regarding propeller torque are valid for the mustang or something similar, but should not be a problem on your light single like a C210. It has a certified crosswind limit (which you should not be exceeding unless you want to void your insurance policy), and that crosswind limit (as someone has said earlier) does not have direction limitations. The aircraft has been demonstrated as capable in that crosswind from either direction, so it can be done safely.

However....

If runway length & obstacles are a consideration, have a good think about the wind direction at a few hundred feet.
This is because the wind direction just a few hundred feet above the ground can be quite different to the pure crosswind you have on the ground. The change in direction and increase in strength of the wind with altitude is known as wind gradient.
If it was a nice long runway, I'd take either. If it was a marginal length runway, I'd have a look at the area forecast wind direction at 2000', and make sure I was taking off into wind.
And if I was landing on same marginal runway with pure crosswind, I'd fly a couple of crosswind legs over the top of the runway first and find which way I'm holding drift. This allows you to work out which way the wind is above the ground, and avoid tailwinds on final or increasing tailwind with altitude during a missed approach.

[Warbo]

In an American built aeroplane (ie the propellor spins clockwise from the cockpit), the torque effect will need right rudder to keep the nose straight down the runway. A crosswind from the right helps to nullify this effect, a crosswind from the left exaggerates it. That said, the only aircraft I have flown that has even come close to being a concern is an Airtractor 802. (I have not flown a high performance warbird.) They can nearly run out of rudder on takeoff in a strong left crosswind, however they are fitted with rudder trim. It is generally only when you forget to set the trim before takeoff that you start to worry. Therefore, I would surmise that the direction of crosswind should be of little concern to any reasonably skilled pilot unless:
a) You are flying a tailwheel aircraft and,
b)it has a lot of horsepower.

[Mach E Avelli]

If you are flying a taildragger which has no differential braking system, then even if it's low horsepower, it can bite. Therefore if everything else is equal, put the crosswind on the favourable side to counteract any torque or gyroscopic effect. Other trick when it's right on the limit is to take off at a slight angle across the runway (if it's wide enough) to reduce some of the crosswind component.

[Biggles_in_Oz]

Mach EOther trick when it's right on the limit is to take off at a slight angle across the runway (if it's wide enough) to reduce some of the crosswind component. I'm not so sure that that technique actually helps a lot.
eg. assume somewhere like YSSY with a 45m runway width and (say) you need 500m to get airborne, if you start at the far edge of that runway and reach the other edge when airborne then the angle offset is about 5 degrees, which will decrease the 90 degree crosswind component by about 0.4%.
With a 'normal' GA airstrip, the width is usually 30m and the angle offset becomes about 3.4 degrees and a 0.18% xwind component improvement.
Now as for an 18m wide strip......

[MakeItHappenCaptain]

Oh good oh. I'm presented with this dilemma daily when taking the old P-51 out for a gallop

Yeah, well RT(first)FQ. That was how this thread started, yeah?:}
PS. Come for a buzz in my Seafury one day. That'll screw you six ways left of sunday!:E

[HarleyD]

Some of my considerations for runway selection with 90 degrees of X-Wind
Sun direction and elevation
Winds aloft
Terrain on departure
Houses/buildings/populous areas
Circuit direction, First turn into wind may help
Established traffic pattern
Preferred circuit direction – ERSA
Torque/P effect etc
Runway slope
Airspace proximity
terrain/structures on windward side that could generate shear/turbulence
If Ag strip, where is the loader?, land toward depart away from
Direction of departure/arrival
Which end are you parked on/vacating to
Where is the Bowser/Hangar
If runway 13/31 , avoid 13, this could mean bad luck
If wind is too strong, where is nearest pub?BTW, the AFM/POH will contain a DEMONSTRATED maximum X/W value, not a certified one, this will determine alternate requirements not actual real world cross wind capability.

HD

[Captain_djaffar]

given engine torque, P- factor and slipstream on a single engine aircraft, I would try to take-off using the rwy with crosswind counter-acting these effects...even slightly....but there's lots more to take in consideration...I would say rwy slope & obstacles are main issues...

[flyhigh744]

Propellor slipstream?

[AerocatS2A]

Some of my considerations for runway selection with 90 degrees of X-

Wind
Sun direction and elevation
Winds aloft
Terrain on departure
Houses/buildings/populous areas
Circuit direction, First turn into wind may help
Established traffic pattern
Preferred circuit direction – ERSA
Torque/P effect etc
Runway slope
Airspace proximity
terrain/structures on windward side that could generate shear/turbulence
If Ag strip, where is the loader?, land toward depart away from
Direction of departure/arrival
Which end are you parked on/vacating to
Where is the Bowser/Hangar
If runway 13/31 , avoid 13, this could mean bad luck
If wind is too strong, where is nearest pub?


That's nice. Here are mine, "does it look good?" Yes, do it. No, use the other runway. Still doesn't look good? Go back to the hanger.

The Grogmonster talks about using the wind to counter the P-factor and torque (which someone guessed before I did, was the "trick"), but in an abort situation, which is what he said sparked the topic, the throttle is at idle, P-factor is nill, as is torque, however you still have just as much right rudder trim applied, so perhaps you should be taking off the other way hmmm :E.

Or perhaps we should all realise that crosswind limits are valid for crosswinds from both directions and we should take which ever runway seems most suitable at the time. If that is decided by a shorter taxi, prevailing traffic, or lack of sun in the eyes, then so be it.