No Rudder Control - Cross wind landings

[Martyn K]

Hi folks.

Looking for a bit of sound anti-crashing advice.

I was flying my AcroWot on Saturday with the wind blowing cross strip about 75degrees with strongish gusts.

I was taking off and landing from Left to Right

Take off was not a problem, hit the laughing stick hard, a touch of left rudder, it tracked straight, hammered down the strip and was airborne.

Landing was a nightmare, rectangular approach was OK, but as soon as I started to bleed off speed on final approach, the model weathercocked to a frightening amount, ie it was tracking more or less straight down the strip but pointing into wind. No amount of rudder control would nudge it round for landing, but it did appear to push it towards a stall

I tried to come in faster but with the GF undercarriage the landing resembled more like one of Barnes Wallis's creations. In 8 landing attempts, I never got it anything like reasonable. In fact on the last landing, the undercarriage actually snapped in 3 places - that was a first for me.

I have landed other models in strongish crosswinds without this problem, I think the issue was that without a headwind and almost idle throttle, I lost ruddder authority, flying faster got it straight but then it wouldn't land..

Any suggestions (besides don't fly it in a crosswind) would be welcome.

Best wishes

Martyn

[Martin Harris - Moderator]

First thought is that models (or full size) do not weather cock in crosswinds while free of the ground.

Heading corrections on the approach should use co-ordinated aileron/rudder - the only (mainly) rudder only input is the final correction during the round-out to kick off drift when flying a crabbed approach.

I doubt if the wing low technique would cope with that much crosswind. If conditions are too much for the model/field layout then perhaps you should call it a day if you can't arrange to land more into wind - remember that full size aircraft have pre-defined crosswind limits...and our crosswinds are typically 5 or 6 times the magnitude in comparison.

Having re-read your OP it could be that it's the final heading correction you're referring to?  If so, the only way you'll get more rudder effectiveness is with a (very quick and well timed) blast of throttle.

 

 

Edited By Martin Harris on 23/04/2013 15:35:14

[Martyn K]

Hi Martin

You are probably right. One other guy was landing through some downwind trees and landing cross strip, but that looked too dangerous for me (in fact he nearly hit me while I was flying - I was *not* impressed). I have flown in stronger crosswinds without too much difficulty, I have never had a model that is as much as a handful as this one though.

Martyn

Edited By Martyn K on 23/04/2013 15:39:13

[Biggles' Elder Brother - Moderator]

Some models are just not particularly responsive to rudder - especially at low speeds. I have a small Spit like that - you can waggle the rudder as much as you like, it wont have much effect!

We fly a lot of aerobats (Extras, Yaks, Zlins etc.) these days, with huge rudders and massive throws and we do tend to get used to very positive rudder response. But not all models are going to give you that.

What was the model Martyn?

BEB

[Martyn K]

Hi BEB

It's an AcroWot - with a huge fin and rudder (although the coupling is quite tight), which I suspect is part of the problem. With the model on tickover on approach the rudder is not getting much authority due to the airflow generated by the prop.

Quite a few people were watching this on Saturday, it was quite worrying at times. No-one could offer a solution either - come in fastish and it was OK, normal approach speed and the heading was dependent on wind strength and direction.

Landing into wind really isn't a problem for it, it comes in quite slowly (ground speed), it' s just seems a problem with strong crosswinds. As I explained in the opening post, with the engine on full bore, tracking isn't a problem either..

Happy to put it down to inexperience and learning a new model, but I could not get it to straighten up properly just before touchdown unless the airspeed was higher.

BW

Martyn

[Chris Bott - Moderator]

Martyn can you add any form of flapperon/spoileron to keep the speed down while you keep a little power on. The power keeping propwash accross the rudder.

I've heard both sides of the story, on the one hand that both ailerons down will add some drag and help keep the landing speed down while adding a little lift. On the other, that both ailerons up reduces lift meaning you have to fly at a higher angle of attack which gives you the drag you need, apparenly the argument goes that this is less likely to exacerbate any tip stalling tendancy.

Not much help am I? But something to think about.

[Martyn K]

Hi Chris

Ailerons up sounds safer to me. At the moment, I have bother aileronslinked via a Y lead, but it is about time that I started playing with some of the computer facilities in my transmitter. How much 'up' is required?

Martyn

[Greybeard]

Posted by Martyn K on 23/04/2013 22:37:39:

Hi Chris

Ailerons up sounds safer to me. At the moment, I have bother aileronslinked via a Y lead, but it is about time that I started playing with some of the computer facilities in my transmitter. How much 'up' is required?

Martyn

Just enough is the unhelpful answer, and when you have found how much is needed please let me know.

[Chris Bott - Moderator]

Posted by Martyn K on 23/04/2013 22:37:39:

Hi Chris

Ailerons up sounds safer to me. At the moment, I have bother aileronslinked via a Y lead, but it is about time that I started playing with some of the computer facilities in my transmitter. How much 'up' is required?

Martyn

I think it's something that needs experimenting with little by little on calm days. Only using it on a windy day once you've had plenty of practice and are completely used to it.

Ideally you ought to be able to add the right amount of elevator compensation.
Of course, how it behaves will also depend on the speed you're flying at and how much throttle you use.

I think a good few tests high up would also be a good idea. Including stall tests.

PS - Don't blame me if it all goes pear shaped

[Martyn K]

Posted by Chris Bott - Moderator on 24/04/2013 08:10:34:

Posted by Martyn K on 23/04/2013 22:37:39:

PS - Don't blame me if it all goes pear shaped

I wouldn't dream of blaming anyone. I appreciate the advice from you all.

Thanks

Martyn

[Alwyn Gee]

Hi Martin

My twopeneth, for what it's worth.

You might try adding a little weight just at the centre of gravity (using some easy fix and remove method) which will then give the model a better sink rate at a faster landing speed. I have successfully done this with several models, not for crosswind so much but more for stronger winds of any direction when the model did not want to settle in the glide and just floated on. I did it by increasing my flight battery size so as not to carry dead weight but some removable lead could serve the same purpose. The slightly more throttle required to control the sink rate and the faster approach may then give you the rudder authority that you need. Otherwise as others have indicated, it's horses for courses and maybe this model should be left in the hanger in a crosswind.

Alwyn