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Bob Grimstead
Captain

Gender: Male
Location: Perth, Western Australia or West Sussex, England
Registered: Dec 2006
Status: Offline
Posts: 1669

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Posted Tuesday, January 26, 2010 @ 11:27 PM  

Hi Guys,

My Forum ramblings here eventually became a fully-fledged article, and in the nature of things, that manuscript became a living document, with amendments and additions in the light of experience. So here's the version current at the beginning of 2012, and with the experience of 121 displays behind me.

Practice Makes Perfect
by Bob Grimstead

My previous article was about designing an aerobatic display that would be a personal expression of flying artistry, a pleasure to watch and rewarding to fly. The next stage is to put theory into practice. I start by climbing my aeroplane to a great height (3,000 feet or more) and flying part of my new routine – say, the first half, or the first couple of passes – to see how it goes and to find any awkward elements. Next, I do the same with the remainder of the sequence, bit by bit, until I am happy it is all practicable. Then I try stringing the whole thing together.
After flying the sequence a dozen or more times above 3,000 feet to establish which will be the tricky figures and combinations, I re-write it until it becomes easier and stays more or less in place over the ground.
Do not expect your own first ideas to be perfect. I often have to modify, or even re-write a planned sequence several times before it becomes feasible, let alone entertaining or visually interesting. Later, after I have a workable routine, I will undoubtedly make repeated changes and minor adjustments to make it more practical, safer or simpler - or suited to different venues with longer or shorter crowds or angled display lines. Over my seven years of low-level aerobatic display flying, this has been a continuous process of evolution.
Next, when I am satisfied the whole thing is workable, I can string it all together and practice it fifty times, experimenting with maximum and minimum airspeeds for the various figures and combinations. This is important. Flying high-energy, high-speed aerobatics is super-safe, but squanders your height. Conversely, flying all the figures at their minimum speeds minimises height loss, but courts disaster. Nevertheless, you do need to be aware of the safe entry speed band for every manoeuvre. Because I fly two otherwise identical aeroplanes but with ASIs in knots and mph, and because, in the hurly-burly of a display it can be difficult to recall numbers instantly, I’ve marked a safe speed bracket for all normal manoeuvres on both ASIs.
Flying my finalised sequence forty or fifty times also helps to fix it in my mind. If it does not happen naturally during rehearsal, then I deliberately botch or miss out a figure here and there, to establish a safe alternative sequence afterwards. I also intentionally snap my throttle shut at various awkward points through the routine to practice my pre-planned recovery from engine failure.
It’s tempting to skip this step, and it takes guts, but you should already be well-endowed with courage if you’re going to be a low-level display pilot. In 2009, two Samson Pitts pilots crashed while relying on their engines to pull them out of a low-level ‘cobra’ manoeuvre. One big radial merely coughed, the other shed its propeller. One pilot was badly injured, but the other - Australia’s foremost contest and display pilot - died. Practising for power failure is important.
Luckily, in a long-winged, low-drag Fournier like mine, providing I am flying over a runway, I can be fairly sure of gliding in to a safe landing, although completing some manoeuvres without power can be exciting as the airspeed falls. Closing a Fournier’s throttle while passing through the vertical pulling up into a loop or stall turn can be most instructive!
It is not easy to confirm one’s positioning up at 3,000 feet, so I gradually come lower to see how things go. At first I bring it down 500 feet at a time then, approaching my legal minimum, I reduce the height by 100 feet at a time, carefully noting safe gates for each figure.
By now I should be able to fly this sequence in my sleep, in any possible combination of wind directions, with pre-planned recoveries for any mistakes or unexpected problems, and the ‘safety energy’ (height and speed) gates absolutely fixed in the forefront of my mind. This should give me spare mental capacity to deal with the unexpected ‘on the day’. And don’t kid yourself; the unexpected and unplanned always happen.
All these heights are of couse not above the ground (or runway) level, but above the highest obstacle in at least a 500-metre radius of the centre of your display. Before you fly, take a good look around. Estimate the height of the highest nearby obstacle -- hangars, tall trees, grandstands, TV screens -- and wind your altimeter down below zero by at least that height. Then it will read zero when you are at tree-top or hangar-top height, not as you are trying to avoid them. And beware the cherry picker with its TV camera that is retracted when you make this assessment!

[Edit by Bob Grimstead on Tuesday, January 3, 2012 @ 10:45 PM]

Bob Grimstead
Captain

Gender: Male
Location: Perth, Western Australia or West Sussex, England
Registered: Dec 2006
Status: Offline
Posts: 1669

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 Tuesday, January 3, 2012 @ 10:48 PM  

Inviting a critic
Now it is time to persuade an aerobatic expert to watch you. You might think you know what your sequence looks like, or how safe it is, but only a knowledgeable aerobatic performer, critically regarding your flying from the crowd’s point of view, can truly determine what your sequence looks like, how accurately you are flying the figures, and how safe you are. This is another vital step which takes courage, and also one you might prefer to skip, but all professional display pilots and aerobatic competitors invite such critiquing. Believe me, it not only improves your flying and the look of your presentation, but it might well keep you alive. Several such sessions with different critics will help even more.
It is tempting to practise early in the morning or late in the afternoon, when the wind drops to a zephyr and the temperature is low, giving both your engine and your wings their best performance, and this is certainly the easiest way to start. However, I believe it is much more important to practise in the worst possible circumstances, so that you are used to them, and do not find yourself suddenly confronted with difficult conditions for the first time during a display, when your mind is already preoccupied.
High temperatures rob your engine of power, your propeller of thrust and your wings of lift. Strong and gusty winds need lots of small, sharp and draggy control inputs, while a steady on, or off-crowd wind requires you to make many corrections with occasional sideslips in some manoeuvres. All this robs you of energy.
Worse from the point of view of sapping your aeroplane’s get-up-and-go, is a strong along-crowd wind, which will probably force you to fly at higher than optimum speed into wind, to prevent being blown away. The problem is that, whenever you are flying at more than your aeroplane’s steady maximum speed, you must be descending and eating into your total energy margins, so you need to start higher on a breezy day.
A thirty-knot wind at 1,500 feet forces me to fly an extra two miles during a four-minute display. Not only might it make me over-run my time slot if I don’t remove at least one pass from my sequence, but it might bring me lower than expected. A gusting wind or thermal turbulence reduces stall margins, so I have to fly either faster or more carefully (or both). All this robs the routine of energy, so I need to start higher than normal and perhaps fly more precisely than usual on a windy day.
Most difficult of all is the fierce on-crowd wind. For obvious reasons, a gap is drawn between the crowd line and the display line. It is important not to cross the display line, but the crowd line is absolutely inviolate. Not only is it vital to practise with an on-crowd wind, but I find myself most closely studying my routine, the site and other performers in those conditions. Low-speed aeroplanes get a small margin of just 100 metres between display line and crowd line, but these are the types most affected by the wind, so it is prudent to give yourself an extra fifty metres or so of margin in breezy conditions.
On the day, if you do get blown across the display line, it is far better to roll wings level, open the throttle wide, climb diagonally over the crowd and apologise later, than to pull hard trying to avoid them – although resisting this impulse in the heat of the moment can be very difficult. Once again, practice is the answer.

--------------------

Bob Grimstead
Captain

Gender: Male
Location: Perth, Western Australia or West Sussex, England
Registered: Dec 2006
Status: Offline
Posts: 1669

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 Tuesday, January 3, 2012 @ 10:50 PM  

Best use of the worst of conditions
For all the foregoing reasons, whenever possible I try to fly my low-level practices just after lunch, in the worst hot, bumpy, gusty, breezy conditions. That way I am confident to fly in these circumstances when I encounter them. Doing this also gives me a good idea of how much height to add at the beginning of my routine if I happen to find the air rough at a particular display.
If I do get blown downwind, just once, in the middle of my routine, I can keep the throttle wide, gently pitch up thirty or forty degrees and then pitch down again when the airspeed gets low. This gives a kind of humped figure that looks to the uninitiated as though it might be some sort of aerobatic manoeuvre. It takes ten or fifteen seconds and is all flown at below 100 mph, so it actually gains a useful hundred feet of height as well as getting me a quarter of a mile back to windward.
If I become really low, I stop aerobatting and fly a balanced 360-degree turn. This takes twenty seconds, gains me 200 feet, and only the experts know it’s not a proper manoeuvre. Believe me, I’ve done it and been congratulated by the organisers on my ‘thrilling display’.
From time to time, on show day the visibility will be limited, robbing you of a clear horizon reference, or there will be a low cloudbase, limiting your start height. Again, it is a vital to have encountered and practised in these conditions beforehand, and I always carry a ‘flat’ sequence card in my overalls. This features merely a succession of loops and barrel rolls, and one full cloverleaf, with gentle wingovers and steep turns as the turn-around manoeuvres at each end of the display line. I can fly all these figures without losing any height, even in the most difficult conditions.
Yes, it is more boring to watch than my usual routine, but it is better for the poor, sodden crowd than just looking at my rain-soaked aeroplane parked on the flight line. And we Fournier fliers have two advantages over the bigger, heavier types. With a small 100-metre looping and turning diameter, our low speed enables us to stay within the crowd’s visual range on a murky day, so we can perhaps fly when the unlimited competition machines, warbirds and jets cannot.
It is essential to practise these ‘flat’ routines, initially in fairly good weather, and then in poorer weather, so you can become used to the myriad unexpected difficulties (like water droplets streaming back over your canopy or spraying on you through the gaps, or condensation from your exertions forming inside it) and the visual illusions of reduced visibility and cloudbase. Then you must stick to your personal limits, rather than guessing whether or not you can fly on a particular occasion. And, believe me, there is a very strong temptation to go ahead and fly your display when you’ve practised for months but the weather is poor and everybody else seems to be getting on with the show.

--------------------

Bob Grimstead
Captain

Gender: Male
Location: Perth, Western Australia or West Sussex, England
Registered: Dec 2006
Status: Offline
Posts: 1669

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 Tuesday, January 3, 2012 @ 10:55 PM  

Setting your personal limits
As I approach my one-hundredth display, my personal limits are now 2km visibility and an 800-foot cloudbase, with only light drizzle at the most. Any more precipitation will damage my wooden propeller at airshow rpm. Similarly, having a monowheel undercarriage, I will not take off in more than a 25-knot wind or a 15-knot crosswind, nor will I display in a temperature over 40°C. But I do regularly practice in those conditions, so I will not be out of my depth when I encounter such bad weather.
If poor weather prevails at a venue and I have not practiced in those conditions during the past month, I will not fly. It is disappointing, but much less disappointing than frightening yourself and the crowd, or worse.
When assessing the suitability of your routine for a particular site, do try to bear in mind the sun’s direction. In an ideal world, all northern hemisphere airshows would put the crowd to the south-west of the display area, and schedule your flight for late in the afternoon, when the sun’s low rays make your aeroplane and its smoke glow golden against an azure sky. In harsh reality, many sites have the poor spectators squinting into-sun, so you need to consider your positioning and the sun’s azimuth to ensure they can even see you against its glare.
I believe you should practise not only in the worst wind, cloud and visibility conditions you might encounter, but also late in the day. Airshows often run behind schedule, and if you’re the last act, you might find yourself flying as much as half an hour later than planned. Low sunshine can blind you at an unexpected moment, and a bright, clear upper sky contrasts greatly with gloom down where the hard ground is.
I recently witnessed a nasty moment when an able pilot flying a top-notch aeroplane had to display later than intended. The location was over calm water ringed by tall buildings. By the time he was called on, the sun had set, although the sky was still bright and his spiralling smoke trail stood out clearly for us spectators.
His first manoeuvre was a torque roll – a figure with no clearly defined completion height. He followed this with two downward vertical aileron rolls – an extremely unwise combination. It was immediately clear that things had gone wrong. Heading straight down, he must have been confronted by a dark, bottomless pit, with absolutely no surface clues from the flat, black water. So he stopped rolling and pulled to the horizon. So hard did he pull that he got several wing-drops, while condensation vortices streamed from his wingtips. You can see this on YouTube: http://www.youtube.com/watch?v=Au-UIUGmLxI& This just goes to show that, whatever your experience, you can still be caught out, but it behoves us all to think through our sequence carefully, anticipate problems, and prepare as thoroughly as possible.
Although it costs money, there is good reason to fly at least some of your practices with smoke. As with all these other scenarios, it is best to experience the possible failure modes for the first time without an audience. Will your cockpit fill with eye-watering noxious vapours during certain (or even all) manoeuvres? Will you repeatedly have to switch the smoke pump on and off to prevent this? Is there a fire risk?
I use orange marine distress smokes in wing-tip pods, and the first time I got a ‘flamer’ was towards the end of a display over the river right outside our front door. Glancing to my right, I saw a foot-long blaze roaring off my wing-tip. About to execute a stall turn (always to the right in a Fournier) I was momentarily frozen. Should I splash down in the river before I fried? How would I turn around? Eventually my brain responded, I executed the gentlest-ever wing-over and stayed on station above the water for an extra minute until my smokes were completely expended. A little prior exposure to this phenomenon would have saved an uncomfortable fright and distraction.
But by far the best reason to practice with smoke is the thrill of flying through your previously-laid trail. It’s sad I know, but I still get the biggest buzz from blasting back though my own smoke.

--------------------

Bob Grimstead
Captain

Gender: Male
Location: Perth, Western Australia or West Sussex, England
Registered: Dec 2006
Status: Offline
Posts: 1669

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 Tuesday, January 3, 2012 @ 11:02 PM  

En route to any event, I always squeeze in a final practice over a feature aligned with the venue’s display axis – a stretch of railway, an isolated tree line, a quiet country road, anything of similar length and pointing in approximately the same direction. This way I can get a feel for the conditions, and assess the likely wind and its effects between 1,500 and 300 feet, as well as ensuring I’m up to speed and as current as possible. If the site is off-airfield, and particularly if it is over water, near hills, or in any other visually unusual setting, I find somewhere similar for a quick, final, low-level practice.
For Perth’s Red Bull Air Race, held over a stretch of the Swan River so wide as to be lake-like, I found a similarly-shaped bay in a body of water 50 miles south and practiced assiduously over that, both for a couple of weeks beforehand, and on the morning of the big show. For London’s event, held over a short, narrow, slightly curved stretch of the Thames, I found a similarly-orientated creek in an unpopulated area near Tilbury and flew my routine a couple of times over that. The more practice you can get, and the more realistic that practice, the better.

We fly aerobatics because we enjoy both them and our feeling of mastery over our machine, plus the freedom of using all three of the sky’s dimensions. So, practising our routine should be a pleasure we are happy to repeat again and again. I have never found that practice makes perfect, but it continually helps me to improve, and I love doing it.

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