Tailwheel takeoff - best side for crosswind?

[rusty sparrow]

A couple of weeks ago I landed my Jodel D120 on a grass strip with a slight crosswind. No problems - straight down the centreline to then park and have a cup of tea. On leaving, the wind had shifted to a right angle crosswind from the left and increased to that the windsock was nearly horizontal.

The runway direction had not changed so, with into wind elevator down and right (edited - I had typed left) rudder applied as standard, I gently started the takeoff run and slowly rotated to the left as I weathercocked due to the wind against the fuselage. A short crosswind runway was available and I was allowed to leave on that.

Here's my question:

As a tailwheel has a tendency to turn left, I think that, were the crosswind runway not available, I'd have been better to take off in the opposite direction with the crosswind coming from the right hand side. Then it would have been easier to counter the crosswind.

-------

Thoughts and comments? All part of the learning process!

[Lord Spandex Masher]

crosswind from the left

left rudder

Here's your problem;)

[rusty sparrow]

Yes - that wouldn't help! Meant RIGHT rudder

[Shaggy Sheep Driver]

Lord SM has it! Surely a Jodel requires right rudder on take off, assuming it has an American flat 4 engine? A x-wind from the left will call for more right rudder than usual, one from the right for less right rudder than usual.

In our Chippy, of course, it's the other way around.

[rusty sparrow]

Yes - I meant right rudder. Now corrected the post. I fly better than I type!

[Pull what]

Just to help-use the rudder on the opposite side from the runway lights you are just about to demolish.

[Humaround]

You're right, sometimes with a left crosswind the added swing left from the prop gyro effect can get you into the long grass. It definitely is easier with a right crosswind (prop running anticlockwise from the front).

I've recently tried a different technique which seems to work well in our Jodel DR1050. The gyro effect is greatest when lifting the tailwheel. I find the aircraft is equally happy taking off without raising the tailwheel - just hold the stick slightly back until you unstick. It tracks straighter with the tailwheel on the ground.

[rgsaero]

"As a tailwheel has a tendency to turn left,..."

Er - No!!!

The tendency depends on which way the engine turns! Nothing to do with a tailwheel, tricycle or otherwise.

If you fly something with an engine which runs the other way - and some do - the yaw tendency will be opposite, regardless of undercarriage configuration.

[Daysleeper]

I've always preferred a crosswind from the left, on the basis that, theoretically, any gusts will make it more of a headwind as the wind direction veers.

[Monocock]

If the engine torque effect and crosswind both conspire to work against you (as I understand your initial post to read), you should have enough rudder authority to combat it as long as you are ready for it. Once the swing starts you bare fighting a losing battle. As younfeed the power to full, have some rudder feeding in at the same time.

Also, in these circumstances, if you try and get your tail up as early as you would on a normal take-off there is an increased chance of the tail swinging round as the tailwheel leaves the ground. One way of dealing with it is to hold the tail down for a little longer than normal on the take-off roll. This reduces the chance of any early weather-cocking and when you do bring the tail up, your forward airspeed (combined with the ongoing prop thrust) will mean that your rudder authority will be powerful enough to control the weather-cocking more easily.

In really strong crosswinds, I sometimes go for a three point departure to guarantee no swinging around with the tail in the air. Just be careful if the strip is bumpy as it can hammer the tailwheel and spring though.

[irish seaplane]

On leaving, the wind had shifted to a right angle crosswind from the left and increased to that the windsock was nearly horizontal.

If you had a 90 degree, full sock crosswind and an american engine airplane then you perhaps learned your lesson on this day out. Nothing broken and hopefully something learned. While pilots getting in on tailwheel airplanes feel more comfortable side slipping to the left, the reality of it is that a taking a crosswind on from the right hand side offers alot more options*. Indeed ask someone to do an aileron roll, and most will go left. A 25kt right hand crosswind is not a big deal in the Cessna tailwheel I fly, as one large application of power straightens the aircraft.

Presuming the basics are right then you can practice this all day, just air taxing up and down the runway on one wheel. If you want the level of competency that truly makes xwinds a non event, just go out and get that trick right!

:ok:


* American engine assumed

[overun]

x wind from the right on cubs, the flap lever plus leg width restricts aileron movement.
Oddly, for similar reasons, from the right also for Atr`s.

[rusty sparrow]

Thanks for all the comments - learning to fly a tailwheel is very rewarding but sometimes challenging :)

Yes, I meant a clockwise rotating propellor (from pilots view). So, in that case there are several forces that will cause the tendency to turn left.

I also fly a Jodel D9 with a tailskid and no brakes - that's fine in crosswind takeoffs but tricky to taxi. In contrast, the Jodel D120 with castoring tailwheel and brakes is easy to taxi but more of a handful in a crosswind takeoff.

I always find turing to the left and slipping to the left more natural - so Irish Seaplane's comments are worth remembering. And, yes, I know which side to have the crosswind from when I next have this situation.

Didn't know that about the cub overun - I've only got a couple of hours in cubs and never had a strong crosswind to deal with.

[Mark1234]

Whilst the engine rotation determines the direction of the swing, the wheel configuration does add gyroscopic procession to the picture as the tail comes up - if that's at the wrong moment it can be the extra straw.. But frankly I'd request the different runway every time.

I'd always assumed the reason everyone rolls left is 'cos everyone teaches it to the left :hmm: The theory advanced at the time was that the prop 'helps' the roll.

[India Four Two]

any gusts will make it more of a headwind as the wind direction veers.

Daysleeper, just remember to change your rule if you ever fly Downunder ;)

[IFMU]

Pull what gives sound advice. We had a big left crosswind at Harris Hill today. I was towing in the Pawnee. I don't care which way the propeller spins, the key thing is not running out of rudder. We only had about 10 kts direct crosswind so it was not too bad. If it is bad enough that you need a right crosswind versus a left crosswind to not run out of rudder, leave it tied down!

In the cub with a left crosswind I don't use flaps at all.

-- IFMU

[hatzflyer]

At an airshow at Rougham some time back I was watching a display by a well known Yak . The commentry is I believe given by his partner .
She emphasised on take off that the engine on the Yak turns the opposite way to " EVERY " other aircraft !

I wonder what direction he takes on a stiff cross wind? :ugh:

[OpenCirrus619]

A question posed by one of the (trickier) instructors at my club:
Which way does a Tiger Moth swing during takeoff?


The answer he's looking for:
It doesn't - because you taught me to do it correctly.

:ugh::ugh:

[overun]

IFMU, l can well understand that with the Cub. The only aircraft l failed to like, with not one redeeming feature, despite it`s cub wings, was the pawnee.
ln a limited space the difference between floating and getting on the back of the drag curve, and arriving like a sack of sh** was about 7kts.
Off thread, sorry.

[Nubboy]

Brian Lecomber wrote some excellent articles for PILOT magazine in the UK some (nearly 30 years ago:eek:).

He very accurately described the four forces that conspire against taildragger pilots from keeping to the straight, and hopefully not too, narrow.

Propellor blade rotation direction is the most visible. Clockwise, from the cockpit is as most have already written, mainly american based engines. Anticlockwise tends towards older, antique, british engines. The force generated is due to torque. Turn the prop clockwise, and the fuselage will want to rotate anticlockwise. This will put more weight, and therefore drag from friction on the left mainwheel, and turn the nose to the left. Right rudder needed to track straight.

Next is assymetric blade effect. Because the fuselage is tail low, the thrust line of the engine is tilted nose up. This gives the down going blade a greater angle of attack than the up going blade. The thrust line of the propellor is therefore moved from the prop. centre line to the side where the prop. is going down. In the case of a clockwise engine, this will move the nose to the left. Right rudder needed to track straight.

Now comes propwash. The propwash doesn't go sraight back ove the fuselage. Because the prop is rotating, so is the propwash. It therefore hits the fin and rudder at an angle, cusing a yawing moment. If again the prop turns clockwise, it will hit the right side of the fin, causing the nose to move to the left. Right rudder needed to track straight (notice anything yet?).

Finally gyroscopic precession. The spinning prop has some properties of rigidity, as in a spinning gyroscope. We start of with the prop. disc tilted, nose up. When we raise the tail during the take off run, we effectively apply a force to the top of the prop disc to tilt it to the vertical. The results in a movement of the disc, 90 degrees later. In a clockwise (last time) spinning prop this means the nose will swing to the left. Right rudder needed to track straight.

All these four forces are additive, and are at there strongest at high power settings and low airspeeds. Your only balance control against them is the rudder, which is least effective at low airspeeds and tail down, blanketed by the fuselage.

Clockwise turning engines means you have significant RIGHT rudder applied, before any crosswinds are taken into account. Crosswind from the left merely adds to the mix.

Short coupled aeroplanes, castoring tailwheels which can't be locked, high power engines, big (heavy) propellors, high nose high angles, smooth tarmac or short grass, healthy crosswinds, putting power on too quickly, raising the tail too early, inexperience or lack of currency on type, all add to a spectators entertainment. Enjoy;)

[overun]

So would that be left or right then ?

We can buy our own books, could l sell you a signed one by Neil Williams ?

[rusty sparrow]

The theory is very well explained in The Complete Taildragger Pilot http://www.amazon.com/Compleat-Taildragger-Pilot-Harvey-Plourde/dp/0963913700

What I learned the other day is that one side is better than the other for crosswind takeoffs. Luckily there were no spectators :)

[Mark1234]

I know we answered the original question a while back, but continuing the drift a little, the place I did my tailwheel had a training aid - a smallish 'bmx' wheel mounted on a handle (one of those big 'pegs' the youf of my time had to stand on and do tricks).

You held the handle, the instructor spun it up, make the pitch change via the handle. I thought it was very effective both in cementing the idea of procession, and the suprising magnitude of force from even a small, light wheel at low speed. What a big prop tries do do to the crankshaft in tumbling flight must be pretty impressive..

[Pilot DAR]

I certainly agree that pilots must be prepared for taildraggers to swing, and that understanding, and anticipating the factors which could affect this is a good thing.

However, once we've considered the torque, P factor, Coriolis affect, tides, and colour of the rudder, I think it is even more important to remind ourselves that the key is to simply be prepared for a swing at all. Sometimes you can analyze things in excess. Then you form an opinion as to what to prepare for, and forget to prepare for the other possible event too. Then "the other thing" happens, and surprises you even more.

Whenever I fly the taildragger, I figure that it is it's only mission in life to have me going off the runway sideways. So I'm going to watch for every clue, and fight back by simply keeping it straight and centered on the runway. Yup, I've scared myself a few times (particularly in the jump 185, which I later found to have no steering whatsoever). All you can do is stay sharp, and expect the worst. If the plane you're flying has an advantage with the wind from one side, or the other, that's good to know, play to that, but never take your eyes off it on the runway!

[Jumbo Driver]

rusty sparrow, there is another performance factor you may wish to consider - and I am rather surprised that nobody has mentioned it so far.

Meteorologically speaking, in the Northern Hemisphere, the wind will tend to veer and increase on the climb-out. Therefore, taking-off with the crosswind from the left will result in an increasing headwind in the climb, thus improving the climb angle. Conversely, a crosswind from the right will mean climbing into an increasing tailwind which will produce a reduced climb angle.

This is certainly worth considering, especially if obstacle clearance is a problem on departure.

JD
:)

[overun]

Personally l use the rudder to keep straight and the ailerons to balance on the into wind wheel and let it fly when it`s ready, or land ...... the process is the same. Of course in the first instance the throttle is open, and in the second closed.

But that`s just me.:)

[overun]

lt`s not in a slip, balanced on one wheel is the way to go, l did assume that the tail had been raised. l see the confusion !

My experience has been that the lower the power the greater the need for "talkies" with the aircraft in a cross wind.

[Vilters]

I flew a D-120 for quite some time.
During X-Wind take off, it was best to keep the tailwheel on the ground at the start of the take off run, as with most taildraggers.
Wind from the right is the worst. You automatically give right rudder for torque and by doing so, you put the rudder surface square to the right hand X-Wind. that + the big flat fuselage surface can give a nasty surprice if not prepared.
So ; keep the tailwheel on the ground, you need the wheel friction to keep things in balance. You can easily take off in 3 point, but mostly I pushed the nose over as soon as I felt solid rudder control.
Tip: grease the vertical axis well to take load of the springs to the rudder. it does not seem like a lot, but it makes a HUGE difference.

I never had a "worry" moment, but the man who bought it from me, had her on her nose 2 weeks later. +> NEVER BRAKE WITH BOTH BRAKES AT THE SAME TIME;

[rusty sparrow]

I find keeping the nose straight with the rudder and the wings balanced with the ailerons easy enough in a x wind landing (was a glider pilot years back). But the problem I had was the takeoff with wind from the left - while slowly accelerating I just gracefully weathercocked as I ran out of rudder. That's because I would have pushed forward to get the tail up and weathercocked on the main wheels - I should have kept the stick back until I got rudder control :O


Don't know how much torque is an issue? The Jodel D120 uses the C90 engine - wikipedia comments "While slightly less horsepower than the O200, many floatplane operators prefer the performance of the C90 over the O200, due to its higher torque at lower rpm. This is primarily due to the C90's camshaft design. The C90 is alo known by its military designation of O-205"

[rusty sparrow]

Vilters - re "Tip: grease the vertical axis well to take load of the springs to the rudder. it does not seem like a lot, but it makes a HUGE difference."

Sounds a useful tip - could you let have a little more detail i.e what/where you mean by the vertical axis?

[Shaggy Sheep Driver]

I think Vilters is referring to the tail wheel pivot. If not free to rotate easily it will add to rudder loads as you stretch the springs, and also you will not get sufficient 'steering' from the tailwheel.

Having said that, I much prefer the free-castoring tailwheel of the Chipmunk. Its unrestrained tailwheel allows the aeroplane to rotate almost in its own length; 360 degrees rotating around either mainwheel. In fact, it's great fun to do alternate 360s like that on the apron (not near parked aircraft though just in case the brake fails!).

It also makes it far easier to manhandle the aeroplane on the ground, in and out of the hangar for instance.

[Vilters]

Correct, but the Chipmunk does not have a FLAT fuselage. It is round, and has less problems with X-Wind.
A free castering tailwheel can not help you maintain direction as well as a steerable tailwheel.
1. Torque, indeed th C-90 has quite some torque and the engine in a D-120 has no offset to correct it.
2. The moment you lift the tail. That very moment the aircraft WILL veer to the left. (Gyroscopic precision), so actually you need MORE right rudder input, the moment you push the nose over.
3. Best practise when in doubt? Keep the tailwheel on the ground untill positive rudder control can be achieved, and be prepared to give more right rudder the moment you lift the tailwheel OFF the ground.
4. And indeed, use ailerons.

Yes, i was talking about the vertical ax at the tailwheel pivot point.

[overun]

4. And indeed,.use ailerons.

From the word go, get it up onto the into wind main wheel as soon as possible.

[hatzflyer]

In my experience it is the pilots that have preconceived ideas that have the most trouble.
It's a little bit like "going with the force ", it sort of becomes natural.
It does take time but make haste slowly and it will come.Its almost as bad being in front of the plane and overcontrolling than being behind and playing catch up.
Try to use smooth inputs rather than small jerky ones, keep your eyes focussed well ahead so as to pick up movement quicker and have more time to react.
In time you'll wonder what all the fuss was about.

[Echo Romeo]

[QUOTE] Personally l use the rudder to keep straight and the ailerons to balance on the into wind wheel and let it fly when it`s ready, or land ...... the process is the same. Of course in the first instance the throttle is open, and in the second closed.

But that`s just me.http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/smile.gif [QUOTE]

Well for me, the above says it all really :D