Thomas P. Turner analyses an often overlooked phase of flight
‘Battery master switch: ON.’ Thus begins another flight, another adventure in the air for recreation, travel or business. Sadly, for many pilots, taking-off is mere preamble. They breeze through checklists, impatient to propel themselves aloft. They make control inputs by rote, not giving their actions the masterful attention they deserve. In short, for many there is no artistry in the actions from powering up to settling into climb. Let’s revisit the whys of what we do in the first phases of conducting a flight, and the importance of mastery and artistry when launching into the blue.
FROM RAMP TO RUN-UP
A successful take-off begins even before you board. This is when you evaluate the aeroplane, pilot technique and environmental factors that will affect your take-off performance. How much distance will your take-off require, and how long is the available runway? Are obstacles or rising terrain on your departure path? What’s the plane’s weight? How strong is the wind? What is the proper technique for this particular take-off? Should you use flaps or not? Answer these questions, and those from the remaining phases of a take-off, in the pre-take-off phase.
For this purpose, we’ll assume that pre-flight planning and the walk-around pre-flight inspection is complete with no discrepancies.
A vital, yet rarely addressed, step of a before-start check is the passenger safety briefing. This is often overlooked, but passengers frequently have no idea how they would get out of the plane in an evacuation. Some pilots think reviewing safety items, including keeping clear of the controls, refraining from conversation when near the ground but calling out the location of other aircraft at any time, and especially how to evacuate the plane in an emergency, will frighten a passenger. But it’s vital information they need to know, and it’s up to you to tell them.
Several of the more important steps of the engine-start checklist happen after you get the engine running. Immediately after the engine fires you should check the oil pressure. If it is not registering as you’d expect, you should immediately shut down the engine. If the engine is very cold, you will see high pressure initially because the oil is not as viscous, with the pressure dropping as the oil temperature rises. Most aeroplanes have a minimum oil temperature limit for take-off, and some have a lower minimum for taxi—usually advised, if you delve deeply enough into the literature, for any operation above 1200 propeller rpm. ‘Just running smoothly’ is not enough for take-off. You need enough oil flow to ensure it will continue to run smoothly at high power during take-off and climb, and that any oil-dependent systems (for example, a controllable pitch propeller) will work correctly.
Check the electrical system, whether your plane uses an ammeter, a loadmeter, or some combination of gauges. Engine starters draw a great deal of electrical power and will quickly overheat, perhaps even catching fire, if they remain engaged too long. Starter relays have been known to stick; ignition switches known to fail to a ‘hot’ position. If that happens, you’ll see a massive electrical discharge on the ammeter or fully pegged loadmeter. Either are grounds for immediate shutdown before the starter overheats and starts a fire.
Also check the vacuum or instrument air system if your plane still employs one to drive flight instrument gyroscopes. If you’ll be flying in low light or restricted visibility conditions, you need your gyros spun fully up to speed before you take-off. If a pump has failed or a regulator is set too low, you need to know before you take-off.
Finally, many planes call for moving the fuel selector between independent tank positions to ensure you have good, usable and accessible fuel in all tanks for take-off. Some POHs suggest starting on one tank and switching to the other before the engine run-up. There may be enough fuel between the selector and the engine to get you barely off the ground before the engine quits, and you know the tank used for run-up will support relatively high-powered operations. So whatever you do to test fuel selectors before the run-up, always take-off on the tank you used for engine run-up.
There are three important things to do during taxi:
- Keep your eyes outside. Collisions and taxiway excursions are common. They seem to be more common now that so many aeroplanes are equipped with GPS and other button-intense equipment. Entering flight plans or otherwise programming avionics is a big distraction, akin to texting while driving. My suggestions are program then taxi, or taxi then stop and program, but do not program and taxi at the same time. Your panel or notebook computer might have a map that shows your position—these are a great orientation aid, but they can’t warn you of other aircraft or obstacles, and they don’t have the resolution needed to keep you from running off the pavement. I suggest using a georeferenced taxi diagram the same way you’d use a GPS in your car in heavy traffic—glance at it occasionally to confirm your position and where you’ll go next, but keep looking outside virtually all of the time.
- Check your flight instruments. This is the exception to the ‘eyes out’ rule. Glance quickly at your attitude, heading, and turn quality instruments as you make turns during taxi. Check that your attitude indicator remains erect in turns; the heading turns in the proper direction and indicates known headings; that the turn coordinator or needle indicates turns in the proper direction and the slip/skid indicator goes to the outside of the turn; and the altimeter is within tolerance with a current altimeter setting. If you are launching into IMC or night, or will be flying in any reduced visibility later in your trip, you need to know the instruments are working properly before you take-off.
- Employ proper crosswind taxi controls. ‘Climb into the wind and dive away from the wind.’ Not only will following this mnemonic position the ailerons and elevator to oppose a strong wind’s efforts to flip your plane, it also reinforces your awareness of the wind’s direction relative to yours and your required actions for crosswind control for take-off (and landing). In other words, having ‘wind awareness’ and the discipline to move the controls correctly, even in the lightest winds, is good training for avoiding loss of control in crosswinds on the runway.
Most before take-off checklists have a lot of steps, but they generally consist of four parts:
- Cabin and occupants check—ensure seat belts and shoulder harnesses are secure, doors and windows are latched, and the fuel selectors and similar items are set properly.
- Engine operation check—puts the power plant through a fairly high-power test, allowing you to confirm temperatures, pressures and flow rates, and confirm the proper operation of redundant systems such as the ignition. Why does the rpm drop when you select a single magneto instead of both? Because the engine develops less power on a single magneto. If you have an all-cylinder engine monitor, though, you’ll see each cylinder’s exhaust gas temperature (EGT) goes up on a single magneto and back down when you return to the ‘both’ position. Why is that? Although the engine develops less power on a single magneto, the combustion event takes longer also. When a cylinder’s exhaust valve opens at the end of a cycle the fuel/air charge is still burning as it is drawn out of the exhaust—it hasn’t had time to fully combust before the exhaust valve opens. The burning exhaust flows over the EGT probe, giving a false, higher indication on the cockpit gauge. This indication is false. But it means the ignition system is responding correctly when you move the switch; if you do not see an EGT rise then there is an ignition problem with that cylinder.
- Control systems check—includes the ubiquitous ‘Controls: Free and Correct’ movement. It also includes operational checks of an autopilot and/or an electric trim system if installed. There’re usually before take-off checklists in the Pilot’s Operating Handbook (POH) supplement for autopilot and trim systems … take a look to see what applies to your plane, and perform the check.
- Instruments and navigation check—ensures everything is set for take-off.
LINE-UP TO FLAPS-UP AND BEYOND
Is your plane producing maximum available power? You won’t know unless you’ve established some power targets. In a fixed-pitch propeller aeroplane you should know the static rpm—the tachometer indication at full throttle and with no forward motion, and compare that to what you see at power-up. If your plane has a manifold pressure gauge, know what to see at full throttle. Most engines lose about one inch of air pressure around a fully-open throttle … so a wide-open engine at sea level should get around 29 inches of manifold pressure most days. What’s the optimum take-off mixture? Check your plane’s POH for specific guidance, but in general, fixed-pitch propeller engines need to be leaned for maximum propeller speed at full throttle. Those with controllable pitch propellers should be leaned per POH fuel flow tables (often placarded on the plane’s fuel flow gauge) or for a target exhaust gas temperature (EGT) setting. Regardless, know what indication you’re leaning for, and lean the mixture for that setting before beginning your take-off roll.
Does it feel right? A better measure of acceleration is to visualise, beforehand, the point at which you expect to reach rotation speed. A rule of thumb is that you should be at 70 per cent of lift-off speed when you pass 50 per cent of the anticipated runway distance.
Reaching your rotation speed target at the predetermined distance down the runway, raise the plane’s nose to the necessary attitude. Whether visually or on instruments, there is one best attitude that provides optimum climb performance. Reach that attitude (Vx or, if runway distance and obstacles are no factor, a lower Vy attitude), and the plane will climb smartly. A few degrees more nose up and induced drag may seriously degrade climb performance. A few degrees more down and climb rate may also be significantly eroded.
If you’ve used flaps for the take-off, leave them set until you’ve confirmed a positive rate of climb and have cleared all obstacles. Don’t pull up retractable landing gear too soon, either; many retractable gear designs suffer from a significant, climb-robbing drag increase while in transit. Have a pre-take-off idea of your expected climb attitude and vertical speed. Compare ‘real’ to ‘expected’ to decide if your take-off is going as planned.
You probably made your first take-off in your first flying lesson (under the watchful eye of your instructor). But it took hours of practice to learn to make passable landings. Consequently, we think take-offs are easy. The reality is that take-offs done right, with mastery and artistry, require a great deal of preparation, skill and thought. One characteristic of masters is they make complicated things look easy. Making it look easy while masterfully controlling the many variables, is the lost art of taking-off.