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Bob Grimstead
Captain

Gender: Male
Location: Perth, Western Australia or West Sussex, England
Registered: Dec 2006
Status: Offline
Posts: 2027

Click here to see the profile for Bob Grimstead Visit http://www.redhawksduo.co.uk Send email to Bob Grimstead Send private message to Bob Grimstead Find more posts by Bob Grimstead Edit or delete this message Reply w/Quote
Posted Wednesday, November 4, 2009 @ 12:27 PM  

Hi Guys,

The RF4 is a great airplane for display flying because it is unusual, and because it is so cheap to operate you can get lots of practise and polish your routine to perfection. However it also has many disadvantages, so I believe it is important to ‘play to its strengths’.

DISADVANTAGES
No Fournier will ever compete head-on and win against an Edge, Extra, Laser, Yak, Sukhoi, Pitts, Eagle or any other dedicated aerobatic machine. It just isn’t strong enough, rigid enough or powerful enough. Nevertheless, over the years, Fourniers have been invited to display among all the above types, and have often won the crowds’ admiration over those others because they are so different.
The Fournier has very low power, limited strength and a glacial roll-rate, so its display just cannot incorporate the snaps, sharp corners or rapid rolls of ‘proper’ aerobatic types.
The Fournier flies comparatively very slowly, so it is seriously affected by even the gentlest breeze.
That Rectimo VW motor could never sound loud and powerful, however big its cylinders.
Any time you are flying at over 100 mph you’re losing energy and going downhill, so you must not pause for more than a moment between each manoeuvre.

ADVANTAGES
On the other hand, the RF4 has very long wings, so you can do something none of those others can. You can have smoke streaming from your wing-tips to give a more three-dimensional picture of your path through the air than ordinary engine-generated centreline smoke does. And your smoke can be orange, not grey. Actually, it HAS to be orange, because that’s the only colour legally available off the shelf. How brilliant this particularly is for Sam in his yellow & orange RF4.

Rather than regarding the RF4’s slow roll-rate as a disadvantage, we can make a virtue of it, and fly graceful, gentle aerobatics.

That requirement to minimise time spent above 100mph compels us to fly a fluid sequence, in which we are always pitching, rolling or yawing (or both, or all three). Many display pilots have a competition background and insist on drawing a short straight line in between all their manoeuvres. Guess which the crowds prefer!

Because it flies so slowly, your sequence can be compact, right in front of crowd centre, and we can display in tight, confined venues where faster airplanes cannot.

Instead of being disappointed at the VW’s lack of airshow noise, we can get the organizers to play gentle, lilting music to compliment the RF4’s slow, balletic flying and be sure that our engine/propeller combination will not drown it out.

Okay, in the cockpit you are grunting and heaving with the best of them; you can be pulling up to 5 or 6g and pushing 3g, and things can seem very hectic as you try to construct those precise shapes and follow the correct lines, particularly in a strong wind, but from the spectators’ point of view, however hard the pilot is working, Fournier manoeuvres appear gentle. Accept this and work with it.

Careful research has shown that the longest time a crowd will watch a single airplane performing aerobatics is four minutes. After that, they get bored and look away so you’re wasting your time. As with all entertainment, you should stop with them wanting more, not sated. It so happens that four minutes of full-throttle Fournier aerobatics starting at 140 mph and 2,000 feet will nicely get the base of your final manoeuvres down to 500 feet. With practice, you can start a little lower, but the one thing you cannot do is climb.

It so happens that the easily-obtainable marine distress smokes last either three or four minutes, so this sets a perfect limit on your display duration. Add two or three smoke-free minutes on at the end for a fifty-foot sideslipping waving pass along the crowd-line before you land and you achieve several things. You allow your engine to cool down a little. You ensure the smokes have completely burned out, so there’s no chance of a fire after landing, and most importantly, you make personal contact with your audience. It is always surprising to me that so few pilots wave to their crowd. Anybody could be flying that airplane if you don’t let them see you, and they love to wave back in applause. That makes them feel a part of the show, rather than mere spectators.

Bob Grimstead
Captain

Gender: Male
Location: Perth, Western Australia or West Sussex, England
Registered: Dec 2006
Status: Offline
Posts: 2027

Click here to see the profile for Bob Grimstead Visit http://www.redhawksduo.co.uk Send email to Bob Grimstead Send private message to Bob Grimstead Find more posts by Bob Grimstead Edit or delete this message Reply w/Quote
Posted Wednesday, November 4, 2009 @ 12:34 PM  

Elsewhere on this forum I have listed all the manoeuvres I believe are feasible in an RF4. I try to make the first part of my display a demonstration of all these things an RF4 can do, strung together in a sensible way, so the experts can see what a surprisingly capable little airplane it is. The second part, down low, is simple stuff for safety.

Those difficult bits are all done up high, above 1,000 feet, where there is space below to recover from a botched figure. And believe me; I’ve been grateful for that height on many, many occasions. I will admit here in public that I don’t think I have ever completed a display by flying my routine precisely as it is written. I frequently fall out of a humpty-bump or a hammerhead, and the propeller often stops, so I have become adept at recovering from finding myself with the engine stopped and pointing in the wrong direction. Having re-started the motor, often I simply delete the next line of figures and carry on. Sometimes I have to improvise by throwing in a turn-round manoeuvre to get the orientation right and go back to before the cock-up. What I do on the day depends on the mistake and the available remaining height.

CONSTRUCTING A ROUTINE
When writing my routines, I start with a blank sheet of paper and a dozen or so tiny Post-it strips, on each of which I’ve written a figure: loop, slow roll, etc. I arrange (and re-arrange, and re-arrange) these Post-its on the paper in the order I want to fly them until I have run out or, more usually, have a few crowd-front figures left but no more turn-arounds. That’s when I have to try and ensure the hammerheads and wing-overs are separated by as many other figures as possible, so that the sequence doesn’t become repetitive.

As a general rule, I try to fly one or two figures in front of the crowd when I am high, and keep it to a single mid-crowd figure when I’m lower. I try to fly all loping figures into wind, and most of the rolling ones downwind to keep their shapes good, although a four-point hesitation roll takes so long and uses up so much distance that I now fly that into-wind.

I link these mid-crowd figures with turn-round manoeuvres (quarter-up, quarter-down humpty-bump, hammerhead, half-Cuban, reverse half-Cuban, wing-over etc).
I try to get in a few manoeuvres on the B-axis (Y-axis for the Yanks) so for these I need a 90-degree heading change, and a quarter-clover is ideal for this. Alternatively a humpty-bump or a hammerhead with a quarter upward or downward roll works too, although nowadays I try to minimise the hammerheads below 1,000 feet because I fall out of too many of these.

Once I am satisfied I have a flyable sequence that is not too repetitive, I draw it all out in Aresti on a sequence card. If the picture goes off the card downwind, I need to start all over again. If it traverses into-wind, that’s great. In four minutes a fifteen-knot wind will blow you a full nautical mile downwind, and in our slow airplanes it’s important to allow for this in your planned sequence, because motoring into wind between manoeuvres breaks up the rhythm and loses height.

In a pinch, if I do find myself being blown downwind, I keep the throttle wide, gently pitch up thirty or forty degrees and then pitch down again when the airspeed gets real slow. This gives a kind of humped figure that looks to the uninitiated as though it might be some sort of aerobatic manoeuvre. Since it takes ten or fifteen seconds and is all flown at below 100 mph, it gains you a useful hundred feet of height as well as getting you a quarter of a mile back to windward. You can see the three Skyhawks doing precisely this on their YouTube clip.

Once I have a sequence that I think will work, I fly it a dozen or more times at 3,000 feet to see how my positioning goes and try to establish which will be the tricky manoeuvres and couples of manoeuvres. Then I re-write the sequence until it becomes flyable and will stay in place over my chosen practice area.

Then I fly that revised, finalised sequence forty or fifty times to fix it in my mind, occasionally deliberately botching or missing a figure to establish a safe alternative sequence afterwards. I also deliberately snap the throttle shut at various points in the sequence to practice my re-planned recovery from engine failure. In the Fournier, providing you are flying over a runway, it is a given that you can glide in to a safe landing, but completing some started manoeuvres without power can be exciting as your airspeed gets low. Try closing the throttle as you pass through the vertical pulling up into a loop and see what happens!

Then I can start coming lower.

After maybe a hundred fly-throughs of my new sequence, I am ready to display it.

God for it, good luck, have fun, and stay safe.

Yours, Bob

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