Tips & Traps

By Jim Davis

When I did my PPL in a little yellow Piper Cub, in 1963, there were no vital actions. The Cub didn’t even have a master switch because there was no battery to switch on. You did a run-up, set the trim and opened its little 65hp throttle.

But as aeroplanes sprouted flaps, gyros, radios, electrics and multiple fuel tanks it became necessary to have a list of things to check, which someone sensibly called ‘vital actions’.

At first everyone had their own list of vital actions, but gradually we all sort of standardised on a modified RAF list. There was, and still is, much debate about whether to do the run-up before or after the vital actions. I still don’t know the answer, but I’ll give you the pros and cons as we go along.

The vital actions list that most pilots seem to use is as follows:

• Hatches;

• Harnesses;

• Electrics;

• Trim;

• Throttle friction;

• Mixture;

• Pitch;

• Fuel;

• Flaps

• Gills;

• Gyros;

• Autopilot;

• Altimeter; and

• Controls.

That’s the basic list, then there are add-ons about passenger briefings and crew briefings and discussing departure clearances and take-off speeds and what to do if a donkey dies on you – which we will talk about some other time.

First, where do you do all these checks? Well, I’ll give you a bunch of the things to help you decide how to position yourself for the vital actions. You can seldom get them all right – so just make the best of what you can.

Ideally, when you conduct the vital checks you want to be:

• At the threshold.

• Facing into wind – for engine cooling.

• Facing so you can see both base and finals (this might be difficult with high wing aircraft).

• Facing so you can see the windsock.

• Facing so that you don’t blow muck at other aircraft when you do your run-up.

• Facing so the sun doesn’t flicker through the prop. Idle revs are about the right frequency to make folks who are prone to epilepsy foam and do jungle dances.

• Facing so you can get out of the way if one of these long-winged gliders, appears on finals pointing straight at you because of the crosswind.

Vital actions and the run-up
Okay, now to the run-up. If you do the run-up before the vital actions, here are your problems:

• The engine may not be warm enough (Continentals like the temperature to be in the green; Lycomings don’t care).

• Once you have checked that everything is fine with the engine, it’s stupid to start fiddling with things that might make it not fine.

• You can easily pick up carb ice while you are doing the other checks.

• The plugs may have time to foul while you are doing the vital actions.

But if you do the run-up after the vital actions:

• You may be sitting for quite some time with the hatch closed on a hot day.

• You may blow a stone up and jam the elevator hinge, after you have checked controls free. Jeff Towill crashed an Aeronca because of this.

There’s no right answer to the question of whether to do the run-up first or last. I do it last, but that’s my personal balancing of the pros and cons.

The next question is should you use a general list that applies to all (or most) light aircraft, or should you use a specific list for each aircraft you fly? Again, there are pros and cons and the choice is yours. I think it depends largely on how many types you fly.

Personally, I like the general one, and I believe it should be a written list – not a memory thing. It’s best to use your memory for checks in the air, and a written list for your vital actions on the ground.

Now let’s get down to the nitty-gritty.

Do it properly, do it yourself, understand the mechanism, don’t trust anyone else – blah blah blah.

I once took off from Youngsfield, near Cape Town, in a Cherokee. Actually my nervous student, Dr Aubrey Michaelovski, did. At about 100ft there was a bang and a rushing of air which told me the door had come unlatched – again.

Not thinking of Aubrey’s reaction to this new and frightening experience, I undid the top catch and pushed the door out into the slipstream to slam it. At the sight of me opening the door Aubrey abandoned the controls, flung his arms around me and begged, “Don’t leave me now!”.

“Relax, Aubrey,” I told him, “I’m just going for help.”

A little while ago a Cherokee in England had the same problem, except that it crashed and killed both people. It seems they had been so busy trying to shut the door that they forgot to fly the aircraft.

On most aircraft, a door popping is a non-event – but not always. I have heard Bonanza pilots say it is no problem, but I had an almost uncontrollable V-tail on my hands when it happened to me near Kimberley. It took a very strong passenger to hold it in before I got sensible airflow over the tail, and landed.

And then there are baggage doors. On some light twins these can be life-threatening, particularly if your pigskin suitcase escapes and leaps into the prop.

A final word on hatches, I like to leave the boot door unlocked – one day you may need to get out that way.

In the mid-60s Johnnie van Rooyen crashed into a river because the seat of his C172 slid back. He survived the crash, but couldn’t open the main doors. The boot door was locked so he drowned as the aircraft sank nose first – leaving the tail sticking out of the water.

Doug Duncan ran my beautiful little red Grumman AA1B Trainer into a ditch after landing. I doubt if he was doing even 10mph when it happened. The aeroplane was not greatly damaged, but Doug’s face shed serious blood on the panel. He had unwisely chosen not to use the shoulder harness.

Another pilot told me, before take-off, that he didn’t like the shoulder harness, but would put it on if he needed it. Really?

There is nothing on the checklist about seat locks, so this is a good place to do it. Johnnie van Rooyen is not the only guy to die when a seat lock failed.

Again, don’t trust passengers – check them. I had a passenger in a C182 whose seat slid back after take-off. What did he do? He unbelievably grabbed the stick to pull himself forward. It just makes you wonder, doesn’t it?

Finally, be sure you can reach everything, including the fire extinguisher, with your harness on.

This covers many goodies – circuit breakers, rows of switches, mags on both, alternators charging, avionics, frequencies and so on.

I’ve told this story before – but maybe you weren’t paying attention. Bob Kershaw and Peter Anderson, and their wives, splattered their flapless, wheelless, engineless Twin Comanche, ZS-FAW, down a country strip. Why? Because Bob forgot to switch the alternators on.

This caused the battery to run down, the radios to pack up, the tip-tank selection solenoids to close – stopping both engines. Then their beautifully planned forced landing was spoiled by the fact that the undercarriage and flaps would both have enjoyed some electricity.

This means all the trimmers – some aircraft have three. Trim seems such a little thing – a minor add-on to take a bit of pressure off the stick. Hardly worth bothering about, right? Wrong. It can also be mighty powerful. A Dakota crashed just after take-off in Pretoria because the elevator trim was fully aft.

Then there was a low-hour pilot in a Baron on the Natal south coast. The pilot and passengers became airborne prematurely, drifted off the side of the runway and crashed, injuring all four occupants. Investigators also found that this aircraft was trimmed nose-up – presumably from the landing.

If you don’t trim it right you have to be very wide awake – and sometimes very strong to prevent the aeroplane from crashing.

Throttle friction
Another silly little thing to fiddle with. I mean, why worry about throttle friction when you will have your hand on the throttle anyway?

Two reasons - you might need to take your hand off the throttle. Or perhaps the throttle friction does something else. This is what caught me.

I came this close to throwing a Twin Comanche into the ground at Kimberley because I was young and smart and didn’t really need checklists.

I was accelerating along Kimberley’s ruwnay 28 and had just got airborne when the aircraft went all sideways, drifted off the runway and lost interest in climbing away from the boulders and desert floor.

This was both puzzling and frightening. At first I thought I was being eaten by a whirly-gig. Then just as I was accepting death as inevitable I spotted the right hand pitch lever had moved itself from fully fine to somewhere near feather.

Duuur – so throttle friction is sometimes also mixture and pitch friction, and can easily kill you.

Now this is a tricky one, and has been responsible for much death and misery.

What are you meant to do with the mixture? Well, set it so that you get all the power you can for take-off. But now here’s the problem – you have no way of knowing where to set it until you have full throttle. And you don’t have full throttle at this stage, or during the run-up, so what to do?

Well, if you really need every ounce of power because it is hot and high, then you must take full power while lined up against the brakes and lean out before brake release.

Fine, that’s the way to do it, but remember this: leaning correctly only applies to those specific settings. If you move the throttle one millifrac the mixture can be entirely wrong.

So if you do lean at full power for take-off, then make sure you richen the mixture slightly before any power reduction. You see, carburettors have a power enrichment jet which gives extra richness, for cooling, at full throttle. This means that if you lean at full throttle and then later throttle back slightly, the mixture will be far too lean.

So when you get to M for mixture – think carefully. You want the mixture correct for idling, so as not to foul the plugs. Then if you do your run-up after the vital actions you will check the mixture’s operation. And finally you will set it wherever you need it for the take-off.

Some pilots like an extra M here for Mags on Both. This only makes sense if you did the run-up at the beginning.

Pitch – fully fine (or high rpm as they say in the United States). Actually I don’t like to say high or low to a student unless I am talking about vertical position.

This is a minefield of different aircraft, different systems and different ideas. Enough for a whole article on its own, so I am not going to delve into it now. The main thing is to know the system, and then think.

I am not keen on changing tanks at this stage – to ensure that both tanks are working. The problem is that you don’t know how long your engine keeps running on the fuel in the lines, if the second tank isn’t working. It might just get you off the ground before quitting. I would rather find the problem at 3000ft than 300ft

Probably the best plan is to start up on one tank, then taxi, do the run-up and taking off on the other.

Of course, you don’t only check tank selection, you also check that the pump is on (or off on some aircraft) and the fuel pressure or flow is where it should be.

Another tricky one. If you select flap now you might blow stones into them during the run-up. If you put them on standby you might forget them.

I did this once on a short farm strip near Cape Town and had some fragrant moments when it went all soggy on me instead of leaping over the trees.

Open – that’s it.

Before setting the DI stop and think. If you set it, as you should, before taxiing, perhaps five or 10 minutes ago – see how far it’s wandered. This gives you a good indication of its health. Then confirm that the suction is where it should be at idle, make sure the little aircraft on the AH is vertically set, and there is no warning flag on the turn coordinator.

Be careful about setting the DI to runway heading. Runway numbers are not always reliable. For instance, Perth’s runway 03 should actually be 01 – it’s magnetic heading is 014°. The problem is that magnetic North has wandered over the years. And they won’t have 02/20 because it confuses everyone, apparently.

Auto pilot
Off, or programmed for after take-off. Remember that immediately after take-off is a stupid place to test the autopilot – particularly if it is at night or you are climbing into the muck.

Set to what? Threshold elevation can be very different from apron elevation. And, of course, it should tie up with the QNH. At Rand airport, near Johannesburg, runway 17/35 has a difference in threshold elevations of 136’.

Full and free movement in the correct sense. Three quick stories about this.

The first was a prototype Lancastrian – a civvi version of the Lancaster bomber. It took off in England on a calm, clear morning, rolled slowly, inverted and dived into a small lake, killing all on board.

Then there was a single Comanche at Wonderboom, just North of Pretoria, that also took off, rolled shiny side down and crashed.

Finally, I had to do a test flight on a rebuilt Bonanza near Port Elizabeth. When I got to the threshold I discovered that the ailerons were reversed.

Mechanically it is very easy to cross the aileron cables. Don’t let it happen to you. If it does, here are two methods of surviving. Hold the shaft of the control wheel and use that for elevator, then use the rudders only for roll control. The second way is to grab the inner portions of the two wheels and fly normally – right hand down for right wing down, left hand down for left wing down.

No, instruments is not on my checklist. And for a very good reason – it’s a pet hate of mine. Whenever anyone says “instruments” they go all stupid and gaze vaguely round the cockpit wondering which instruments to check.

If it is on your list, think of something better.

The engine instruments should be checked during the run-up. You do the gyro instruments under “gyros”. And the pressure instruments should have been checked during your round-the-cockpit check at start-up.

When I was hanger boy for the Piper agents in the 60s I used to fly as a sort of safety-pilot cum bag-carrier for the boss – Piet van der Woude. Piet was no stranger to alcohol and often an early morning departure in his Twin Comanche would be preceded by a bleary eyed look round the cockpit followed by a declaration that, “All ze clocks seem to be vorking – ve go”.

With that he would push everything forward and grip the stick grimly with both hands. On such mornings it was wise to get to the aircraft well before old Piet and do some unorthodox cockpit preparation.

I looked after old Piet, and God looks after old ladies and student pilots. The rest of us need to do our own vital actions checks. And do them properly.

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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