The nose of our Twin Comanche points straight down towards the Cape Recief lighthouse, which is rotating in the windscreen. I advise my student to throttle both engines fully back and recover. He tries. There is a shudder and we are spinning the other way.
“OK, I’ve got her,” I say, and confidently do all the right things to restore sanity to our revolving world. Again she shudders and the lighthouse reverses its rotation. Only it’s getting bigger now.
I am more puzzled than alarmed. Then I remember Mike Van Ginkle telling me that he had suffered an identical disappointment in another Twin Comanche – also with full tip tanks. He recovered by chucking out the gear and flaps – and then doing everything v-e-r-y g-e-n-t-l-y. Mike’s solution proves effective and we ease out of the dive, still on the edge of a shudder, and with the water barely 50ft below us.
What you need to know
To be a safe pilot you need two things - sensible thinking, and the ability to handle the aircraft at low speed. The first is called airmanship and it takes time to accumulate – that’s why we have rules. The second, which should form a big chunk of the PPL training, mostly doesn’t.
We should be relaxed flying the aeroplane in the range that spans 20kts either side of stall speed. If you haven’t flown below stall speed it’s time you learned about it.
First you need to understand what stall speed means. If your POH says the clean stall speed is 6Okts, that means it will stall at this speed when the aeroplane:
• Is at gross weight, with the gear and flaps up;
• Flying straight, with the wings level and the ball in the middle;
• Has the engine idling; and
• Is being maintained at a constant altitude.
So you throttle fully back and prevent the aircraft from losing height by steadily easing back to compensate for the lift being lost by the decreasing speed.
If you are at less than gross, or flying at less than 1G, you will stall at less than the published speed; and if you are pulling more than 1G the stall speed will be greater than the book figure. This means you can stall it at any speed. But in practice you are not likely to stall at more than about 15kts either side of the POH figure – unless you are doing aerobatics.
In a steep turn, or pulling out of a dive, you might get a stall shudder at around 75kts. And if you climb and then move the stick forward so that you feel light in your seat, you may see 45kts without any sign of a stall.
However, in day to day flying, low-G, low-speed flight is not common because most pilots don’t venture there, and it’s uncomfortable – particularly for your pax.
But the range between the published stall speed (we’ll stick with 60kts) and your approach speed of 1.3 x the stall speed (making it 80kts) is the bit that really counts. This is where you find yourself near the ground, just before landing, or just after takeoff. It’s when you need to fly most accurately, but it’s also when the aircraft is behaving at its sloppiest. And it is a time when you are most vulnerable to the wind.
But worst of all, it’s the bit at which you have the least practice, and the only time you are close to something hard.
So let me give you a couple of exercises that can make a huge difference, not only in your handling when you are low and slow, but also in making you feel comfortable there. Once you have got them right you will be able to get back onto centreline when the wind drifts you off; you will be happy to sort it out when the aircraft balloons in a gust; and you will have it all under control when you do a go-around.
First, read through these exercises and decide whether you are relaxed about doing them alone. If not, take a good instructor with you - one who is comfortable with spins and incipients. You won’t be doing them, but if the instructor is a bundle of nerves around the stall you are wasting your money.
Next, you need to understand a bit more about the stall speed. In this case the handbook says it will stall at 60KIAS. It’s the indicated bit that’s important. Most aircraft that have the standard L-shaped pitot, with a pipe pointing forward, will not indicate correctly. When a C152 tells you it is doing 40mph it is actually doing 58! A massive lie.
Pipers, with their stubby little matchbox pitots, have no significant errors throughout the speed range. So a similarly loaded Cessna 152 and a Cherokee 140/160 probably touch town at about the same speed regardless what the ASIs say.
From a handling point of view it makes little difference what the needle shows at the stall – it’s just a reference point, not necessarily an accurate indication of your progress through the air.
Right, let’s get on with the flying. Find yourself a quiet bit of sky and some altitude, and slow down to your flapless approach speed – 80kts. Use enough power to maintain altitude and enough right rudder to keep the ball near the middle. Trim.
Now imagine you are following a gently winding river. Follow the turns left and right. Do it for a few minutes. Feel okay? Sure it does. Notice how you do need a bit of rudder to keep the ball in the middle as you go from one turn to the next.
Now make the turns a little sharper and you will see quite a serious need for rudder with aileron as you roll from the left to the right, and back again.
The next step is to do the whole thing again but 10kts slower – at 70, which is 10kts better than the published stall speed. Okay, it feels a bit soggy, and it needs plenty of rudder, and the stall warning bleats – particularly as the wing with the sensor moves down. But you are still in control.
Maintaining 70, do your HASELL checks, pull the power right off and try to hold altitude by easing the nose up. The stall comes almost immediately. Note the speed, it will probably be below the published 60kts, unless you are at gross.
For the recovery we don’t want any of this wild SPL stuff of cramming the stick forward and flinging everyone against the roof. Simply e-a-s-e the stick gently forward until the shuddering stops. Don’t use power. The aeroplane is flying again. Savour the moment. Now, gently ease back again until you feel the first signs of the shudder. Now, gently forward again.
Do this several times until you are comfortable with easily drifting between the stall and normal flight.
If you have always been scared of stalls, it’s not your fault – your instructor was scared, and his instructor before him. So they all passed on this business of hauling the nose up, staring at the sky until your world disintegrated and then heaving the pole forward and cramming on full power.
It was a nonsense and it taught you nothing but fear.
You want to caress the aircraft past the edge of its flying ability and into a stall, control it with confidence, and gently ease it back to flight, in the same way that a good driver controls his car through a skid and back to normal.
Ignore those who tell you to pick up a dropped wing with rudder – that’s rubbish. I have flown around 150 types of light aircraft and haven’t found one that demands this treatment. You should use aileron and rudder together – all the time.
Comrades, Piper, Cessna and Beech put rudders on their aeroplanes simply to counteract two design flaws:
1. P effect - the aeroplane’s tendency to yaw left when you apply power.
2. Aileron drag - the aeroplane’s tendency to yaw towards the down-going aileron. So when you move the stick to the left, the right aileron goes down and causes drag which yaws the nose right. In other words the nose yaws the wrong way. Left stick and the nose yaws right.
To deal with these two problems they fitted rudders. So every time you use the ailerons, be it for entering a turn, correcting for turbulence, or picking up a dropped wing, you should move the rudder at the same time, and in the same direction, to counteract the aileron drag.
This is very noticeable at low speed – the slower you go, the more rudder you need.
So to get back to the point, if you drop a wing, either near the stall or in the stall, fly normally – pick it up with aileron and rudder together.
Right, we have got you controlling direction nicely at low speed; now lets work on height. Get her straight and level at 70kts, nicely trimmed and with the ball in the middle. Now maintain 70 and climb 500ft at climb power. Now level off, still maintaining 70. Now go into a glide at 70. When you have lost 500ft go straight to full power and climb 500ft again.
Then go straight into a glide. Do this several times – it’s brilliant practice for speed control and for doing a go-around.
It is a difficult exercise – you won’t get it right first time. If you are battling to get it smooth and accurate, level off between each climb and glide. Keep at it until you can do it smoothly, with the ball in the middle, and nail the numbers.
Now pat yourself on the back, apply full flap and do everything again. This time, of course, your airspeed will be much slower.
Say your full flap stall speed is 48KIAS, 1.3 will give you an approach speed of 64 – call it 65. So first do your river following at 65 and when you are happy with that then do it at 55.
Then do your HASELL checks, throttle back, prevent the nose from dropping and she will stall almost immediately. Recover as before by easing forward until there is no judder. Use no power. Now ease her into and out of the stall judder.
She may drop a wing, but so what? You handle it with aileron and rudder, and ease the stick forward to stop the shudder – no problem.
Now do the climbing and gliding thing with full flap and the airspeed at 55. You will find this is hard work. And when you think you have got it right, have a look at the ball during your power changes. Horrible. When you have really got it sorted – land.
The lazy eight
After quaffing a self-congratulatory beer you can now think about tomorrow’s exercise – the lazy eight, a precision exercise which takes you well below stall speed without stalling.
It consists of two wing-overs, one left and one right, forming a figure eight. There are noset speeds or angles of bank – you decide on our own targets and then try to stick to them. Here’s how it goes.
Pick a line feature and do your HASELL checks. Head about 20° right of the feature and either dive slightly, or increase power to achieve twice your clean stall speed. So we will make it 120kts.
Note your altitude. Now do a climbing turn to the left so that when you are at 90° to the line feature you are at maximum bank (make it 45° initially), maximum altitude, and minimum speed (50kts initially).
Gradually roll out of the turn and lower the nose so that your wings are level when the nose is about 20° left of the line feature and your airspeed increases to 120 as you cross the line, at your starting height – if you have got it right.
Now do the same in the other direction. You will notice the need for rudder during the speed changes.
When you can do it accurately, try with 60° of bank and the airspeed down to 40kts (20 below the stall). It doesn’t stall because you are pulling considerably less than 1G.
When you can do it well at the lower speed and 60°, retire to the club in the knowledge that you are on the way to becoming an extremely competent pilot.
Sip an icy ale and allow yourself a miniscule smile as you listen to the newest hero, who has no knowledge of slow flight or lazy eights, but is something of an authority on doing beat ups in his Baron.
Jim Davis has 15,000 hours of immensely varied flying experience,
including 10,000 hours civil and military flying instruction. He is an
established author, his current projects being an instructors’ manual
and a collection of Air Accident analyses, called Choose Not To Crash. Visit Jim's website by clicking here.
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