Stopping the damn thing

[Simon Chaddock]

As an older gentleman and an ex full size flyer I agree a knife edge will cause the model to loose height quickly but I not so sure it will do much, if anything, to slow it down.

In a conventional landing approach you slow down first then use means (throttle, air brakes &/or side slipping) to contol the angle of the glide path but keeping the air speed the same. The problem you have in a model is judging its speed accurately, as you want as slow as possible for the landing but too slow and you crash. As we don't have remote reading air speed or stall warning indicators on our models (yet!), as advised, you will have to learn the safe speeds and glide angles simply by the look and response of the model.

As my gliding instructor always said  "Watch the attitude" and he meant the glide angle, not about being bitchy to fellow pilots!

[Paul Williams]

Thanks Simon, it was also a proper pilot that suggested I use rudder then counteract this using wing control, I did try that but found it difficult to stay on the flight path so to speak.

[Former Member]

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[Rick Tee]

I agree with Evan, on finals your air speed is controlled by the elevator and your rate of decent by throttle, get this right and except where Eric has mentioned cross wind landing, you've cracked it. The mistake i think many learners make (me too cause i'm more of a glider guider then power flyer) is to throttle off to tick over on the downwind turn and fly the aircraft in, more a dead stick landing then a power landing.

[Evan Pimm]

Cross wind landings do not required the use of 'sideslip' to centre the runway. Simply put, the model must be pointing a bit into the cross wind, and flown as normal, the x wind component will make the model appear to slip all the way down to the runway. What you will need to learn is how much rudder you need to straighten the model so it points straight down the centre line just before the mains touch, and how much 'aim off' into the wind you need on finals. Again this is real easy sitting in the cockpit, but takes a fair bit of practise standing on the side of the strip.

Evan. 

[Former Member]

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[Evan Pimm]

No, as far as the aeroplane and pilot are concerned the airplane is flying normally, there is no rudder input, no 'crossed control' aileron application. The 'Track made good' over the ground is straight too. You are confusing the apparent attitude of the model to you, the ground based observer, and the bit of ground you are standing on. Without the rudder and aileron application, there is no 'sideslip', so the model cannot be 'slipping'. That the model is not going in the direction it is pointing, 'relative to the ground'  is because the model is flying in  a bit of air that is also moving, relative to the ground. Confusing, I know, but to land any aeroplane with a cross wind component on the strip there is no need to apply any sort of deliberate slip with rudder and aileron. Read the previous bit again, point the model into the wind a bit, and the combination of the models foward motion and the air's movement is the direction you want to fly.

[Former Member]

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[Andy Harris]

Hello thread.

 I might have sent you up the wrong path with all this rudder business ... 

 I spent a few hours today at the Paul Heckles school.  As I landed from the first flight I used full rudder and quite frankly was looking for more to get the speed off.

 This gave rise to a conversation as to why I did this... basically it worked for me on light electric models.  It feels safe a secure to use lots of rudder (I did learn a fair bit on my own).

 I had a whole session on landing without the rudder, and doing several other manuvers 'rudderless'.  In fact the guys dialed out the rudder so I couldn't use it.

 Also the first time I've flown IC powered models (other than the odd 4 minute try out). Of course these are heavy and have momentum.

 Basically I was taught to put more and more elevator in as the plane came in, this strategy certainly worked.   

 So I've got to bite the bullet and transfer these new skills to my models.  

Andy 

[Evan Pimm]

I have flown one of those light electric models, after my Sicroly it was very light, and the old up elevator trick very nearly stopped it dead. With little weight/momentum, aerodynamic drag has a huge effect on the foamie things. Be gentle the first couple of times.

Evan. 

[Paul Williams]

Landing the edf jet has always been a heart in mouth expearience, it comes in lke a dark and soon eats up 100m landing strip this is not made easier with nearby trees preventing a gradual hieght loss. I had a play yesterday and set up the flap switch to give 10 degree down on ailerons with 5 degree up on elevator. Much better result I can drop to quarter throttle or less and not stall. Do you ever stop learning?

[Tim Mackey]

Nope.... never.

[Former Member]

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[Jim Newman]

Paul Williams.....

Listen to Evan Pimm, my aviating friend. HE is the only one making sense...and when I saw him mention Private Pilot Licence , I fully understood. 

At very low airspeeds do refrain from using the ailerons. Make liberal use of the rudder instead. The down-going aileron increases the Angle of Attack and so you have the grave risk of stalling that wing tip and entering a low altitude incipient spin.

I will refrain from mentioning my own long career, because we have far to many with "I trouble" as it is. Yes! I am an old, old  Grey Eagle perched here......

 May I, sir, respectfully refer you to my fully illustrated article,Landing with Flaps in RCME, May 2008 issue, page 52. Merely delete the references to flaps. All else applys.

You will note that I do not make use of fancy 'teen inspired abbreviations out of respect for your limited experience. THOSE things are best left over a beer in the club house, AFTER flying is done for the day, when we can tell outrageous lies and "line shoots" as much as we like before happily heading homewards, as the sun sinks slowly in the west (of England)......

 Happy (slower) landings.

 Per Ardua.....

Jim

[Paul Williams]

Jim,

you wise old bird, your advice is gratefully accepted and I bow to your vast knowledge. I have only one problem with it I don't have a rudder!!!!! ha ha

[Jim Newman]

Paul, my kindly friend!

I fear that in my advancing years mine is now a little over generous.......!!!

Is there any way that you can do a "mod" and install one, with an additional servo? You will find that it opens up a whole new aspect of RC flying. Nevertheless, for about five years I did fly prototype kits of an Me. 109,  Zero and P-51...all Cox .049 powered and only aileron and elevator. They still were a lot of fun , but often I yearned for a barrel roll and a stall turn that requires co-ordinated rudder input.

Jim

[Rick Tee]

Hmm what rudder input do you need for a barrel roll? I use aileron elevator only, and my slope soarer will stall turn without rudder just fine.

[Jim Newman]

Greetings, Mr. Tee.....

On with my flying instructor's hat, I fear.......

A properly executed Barrel Roll is a horizontal helix. It is, in fact, a  properly co-ordinated turn, using all three controls, all along a horizontal axis, using a little 'up' elevator tto help along the road to success.   

When I am messing around on a severe clear sunny afternoon, in a Decathlon, I pick a straight road along which to fly (at about 3000 feet I will add!).

Then I will make a turn (say to the right) until we are at  30 degrees to the road's heading, then immediately feed in a 'up' elevator to initiate a climb of about 30 degrees.

At the same time I smoothly apply a co-ordinated amount of left aileron and left rudder, and keep the roll going until we have the green and the blue in the proper relationship once more. (Blue is up, green is down, by the way.)

Properly done, you will end up at the end of the helix...still 30 degrees off the road heading....and with the ball of the Turn and Slip Indicator still centered (indicating that my helical turn was without Slip nor Skid. (Draw a freehand helix and road to see. )

 If you have a buckshee plastic model Spitfire at hand, "walk through" the maneuver, using the edge of a table for reference. I will not "tell on you" if you purse your lips and make suitable Merlin noises -  with a few backfires and hiccups while inverted.

NOTE: When  you approach the inverted,  you will likely need to momentarily relax the back pressure on the stick.... to avoid dropping the nose (dishing) out of the roll.

Tally Ho, chaps!  Watch for the Hun in the sun. 

Jim

[Paul Williams]

Jim, where you ever in one of those camp places where they did experiments on people?

I love your sense of humour takes a lot to make me smile first thing in the morning, but I would defy you to put a little any control in whilst rolling this jet. You would need reactions quicker than a Pentium 6. I can hear your reply as I type "slow it down old boy" but then it would not be a jet would it.

tally ho Biggles.

[Rick Tee]

Thanx Jim, i'll certainly be trying that out, hopefully i can improve my barrel roll, though not with that particularly glider . Though many models have a fair bit of dihedral applying rudder for the roll can result in a much tighter and faster roll than intended (it is possible to fly some of these models with out aileron input at all). Come to think of it most trainers (certainly mine will) would complete a roll without any aileron input. Not sure if this could be described as a barrel roll or come to that an axial roll either. I don't usually use rudder in turns like on full size, more often opposite rudder is used to keep the nose up in a steeply banked turn (60deg+), Using rudder in the same direction generally causes the nose to drop quite badly in a turn (slipping in or out of a turn is not much of an issue with small models), does depend on the model some though. Large span gliders (2.5mtr+) for example generally need some rudder in the same direction as the turn, or they slip out of the turn, small powered aerobatic aircraft need opposite rudder or they will drop their nose. (small = under 2mtr span, not flown bigger powered models yet.) In which case shouldn't i be using opposite rudder on the up side of the spiral and reverse that on the down side in order to maintain heading? Elevator is either released altogether at the top or a small mount of down elevator used (like in a loop) to prevent the nose dropping and the aircraft tucking under and the roll looking more line a '9' from behind/in front instead of an '0'.

Just to check i have this right, a perfect barrel roll describes a circular spiral while the aircraft maintains a constant heading? Rudder, i think with my aerobatic powered model, would cause the tail and nose to describe slightly different circles (off centre) from that of the centre of the fuselage. In other words viewed from behind in an anti clockwise barrel roll the nose would point left at the start, down on the up side, right at the top, and up on the down side.

One of our club members fly's for the Ripmax aerobatic team, i'll have a word with him next time he's up the field. He was doing some great barrel rolls the other day with another members Sea Fury. I really would like to get this manover tidy before i buy my first warbird.

[Jim Newman]

A good, drab Michigan morn to you, Paul!

Long, long ago, I was in many of those camps where they did experiments on people. The "experimenters" were called Drill Instructors who could inflict untold cruelties with their wish for perfection of the race.....and with comments from over one's shoulder and into one's ear such as, "Am I 'urtin' your, Sir?   I ought to be....I'm standin' on your 'air........Sir!"

I thank you deeply for your kind remarks concerning my humour. Many moons ago, when RCME was barely out of the wood pulp stage, if you are old enough you will recall my many cartoons in Aeromodeller, RCME and Norm Butcher's Radio Modeller. However, a greatly concerned commanding officer saw fit to "suggest" that for one of HM's clean shaven little lads (in a little blue suit with brass buttons) to be seen  publishing humour (and getting paid for it while HE wasn't receiving a "cut")  was more than crass. So I took up a  "pen name" that I am too embarrased to quote. THEN I found that a well known Wing Commander also was publishing, so I uttered a well known and fashionable word of the day, and went back to my own "handle'!

As for control inputs, no matter what the speed, all it takes is, practice, practice, practice...and when you feel you have it '"Orl Krect"...practice some more! The term for it is, Hand/Eye Co-ordination!

Stay ten mistakes high while you are  at it. You might care to keep a large plastic bag handy, too...............

Jim

[Jim Newman]

....and a very good morning to you, too, Rick,

Your opening paragraph took me back to my own, very  early, RC days when my TX wooden box was resting on the ground and about the size of a wheel barrow...and weighed a ton or three with its huge 120 volt and 2 volt batteries. The ariel was a massive, tubular vee that, I swear, was purloined from the Dew Line radar site. Control was by a single press button on a six foot lead.......

Models of the day boasted only a rudder (driven by a wire crank turned by a wound up rubber band)  but with lots of wing dihedral. In that form we accomplished loops, rolls.... and turns of various diameter achieved by "blipping" the push button. The rudder "cycled", going left - neutral - right - neutral - left, etc.

The use of generous dihedral produced what is known as Yaw/Roll coupling. Apply rudder... and the model yaws....the appropriate wing rising under the action of dihedral. Keep that turn going very long and your model assumed a fast, spiral dive. Remove one's digit from the button...even "blip" a little opposite rudder... and the model would zoom upwards, caused by the accumulated airspeed...and over the top she would go.

 Of course, she would not recover to straight and level, but would attempt a second loop because of the excess airspeed. The trick was to give a quick blip of left or right rudder to enter a turn, in order to bleed off excess airspeed. In the Big Boys Toys we called that Energy Management!

Barrel Rolls were achieved from those beginnings, since in "rudder only" there was no such animal as an Axial Roll, in which the nose stayed nailed firmly on a point on the horizon. Start a slight spiral dive, centre the rudder ( the speed giving  a shallow climb), apply rudder...and round she went .... hey nony no!!!!!!!!

To answer your query....The barrel rolling model is NEVER on a constant heading...it is effectively making a co-ordinated turn all through the barrel roll.

 If you will, imagine a huge, horizontal coil spring in the sky...your model is following the wire of the spring. Its track across the ground is a straight line (the center line of the coil), but its path through the air is a spiral (helix) - until you straighten it out and continue to follow the heading of that convenient road I mentioned at the start of all this.

 For you to be using opposite rudder in a turn is courting a potential "spin in", since your control movements are now unco-ordinated. Cross controlling is the classic entry to a Snap Roll in which one wing stalls violently. If the nose is dropping, it is because you are effectively losing lifting area.

Remember! Lift always acts at 90 degrees to the lifting surface. A line drawn at 90 degrees to the wing's upper surface  would be called a Lift Vector. If you bank that wing, that vector is no longer pointing vertically upwards towards Mars, so you effectively have "lost" some lift.

Imagine a bright light shining directly downwards on your model. The shadow on the ground will be that of your model.  Now steeply bank your model. Notice how the shadow of the wing becomes shorter? Effectively - there goes some of your lift!

 May I respectfully suggest that you gradually center the rudder, as you become deeper into the tight turn....and use more "up" elevator as you do so.

One of my soaring sites used to be at Cherhill's White Horse monument , alongside the A4 near Calne, in Wiltshire.

Thermals... and happy soaring to you, Rick. ....Now back to my digitally controlled Bath Chair!

Jim

 ,

[Rick Tee]

Thanx again Jim, nice piece of history too, i too remember those days but at the time opted for control line or 'radio interrupted flight' Think i have an old book some where which gives info on early attempts at proportional control via something called 'Galloping Ghost' . There are still plenty of trainers available with rudder/elevator only control.

[Former Member]

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