By Ryan Ferguson
(cont'd from Page 1)
Starting the Twin
It's straightforward – very straightforward. And despite the fact there's a maze of switches, a lot of them are doubled for the left and right engines – a closer examination reveals that there's nothing new here, except a 'crossfeed' setting on the fuel selector. The starting procedure is just the same as a fuel-injected Lycoming-powered piston single:
- Rotating beacon: on
- Alternators: on
- Master: on
- Mixtures: idle cut-off
- Throttles: halfway forward
- Left fuel pump: on
- Left engine mixture: rich
- Wait for a 4-6GPH flow on the left engine fuel flow indicator
- Mixture: idle cut-off
- Left engine throttle: crack to ½"
- Left engine mags: on (they're switches instead of key detent positions like in your single-engine piston plane.)
- Clear prop!
- Crank the starter (you depress the two-way starter switch to the left to start the left engine – a keyless start!), wait until the engine starts to fire, and smoothly bring the mixture to full rich.
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Finally, we're getting somewhere! Now, don't relax – this is a twin and you've got to pay attention at all times. As soon as the engine is running, focus on the left engine's RPM gauge. Now that the engines are out on the wings instead of directly in front of you, it's going to be a lot quieter in the cockpit. Therefore, it's easy to be sitting on the ramp with the engines roaring away at 1500 RPM, while you're standing on the brakes wondering why the plane keeps wanting to creep forward.
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"Flying a twin means a lot of redundant systems, and this can translate into increased flight safety – but that also means there are other systems which you may not be intimately familiar with that come into play in the event of a failure on one side. Be familiar with your aircraft systems."
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After startup, pull the power back so that the engine is smoothly idling at no more than 800-900 RPM. Immediately check your oil pressure gauge – it should be coming up within 30 seconds. If it doesn't, you'll need to shut down. (Nothing different from starting a single, right?) Once you've verified that the oil pressure indication is in the green, check your suction gauge. You should be reading positive suction and "one ball out." Yep, even the suction gauge is different in the twin. You have two vacuum pumps, and therefore you'll need an indication as to their health. Two small "balls" in the face of the gauge are sucked out as their respective vacuum pump fires up along with the engine. So, as soon as the left engine fires, the left engine "ball" should disappear from view, while the right "ball" will still be patiently waiting for you to start the right engine.
If the ball doesn't disappear, you've got a suction problem. Side note: if you start up the left engine and both balls disappear from view, you have a problem with the one or both of the valves isolating your vacuum pump lines. If this happens, you'll have lower suction than normal if one of the two pumps fail, because air from the pump will be escaping into the unclosed vacuum line leading from the other pump. Flying a twin means a lot of redundant systems, and this can translate into increased flight safety – but that also means there are other systems which you may not be intimately familiar with that come into play in the event of a failure on one side. Without exceeding the scope of this article, I'll summarize by saying: be familiar with your aircraft systems. Your examiner will have plenty of systems-based questions for you on checkride day – and for good reason. Be ready to answer them in detail.
Back to our twin idling on the ramp with one prop spinning. Now, you simply repeat the process for the right engine. Follow up by shutting down both electric fuel pumps as soon as you verify that both engines' oil pressures are in the green. Phew! It seems like a mouthful, but the starting process is actually exactly the same as what you're already used to in fuel-injected aircraft, with just a few additional tasks along the way.
When you taxi out, keep in mind that you will only need slightly more than idle RPM to maintain your forward motion. You now have two engines pulling you along the ground instead of one. The cardinal sin is riding the brakes. Avoid it by keeping an eye on the RPM gauge.
You'll find you can use differential amounts of engine power to help the plane turn left or right, or maintain a straight taxi course with a crosswind. Cool, eh? Be careful not to make such a tight turn that the nosewheel will drag. Usually, they can only turn approximately 20 degrees to in either direction.
Let's take out our checklist now, shall we?
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