Starting your big-bore Continental or Lycoming engine

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A Cowboys Guide to Starting your big-bore Continental or Lycoming engine

Many of us struggle with the techniques appropriate to starting our fuel-injected, big-block Lycoming and Continentals -especially when they’re hot! Quite apart from the frustration and embarrassment, improper starting techniques can result in flooded engines, fires, cooked starter-motors, airframe and engine damage, flat batteries and even (potentially) personal injury or fatalities. Generally speaking, cold-starts are not an issue, whilst it appears that many of the difficulties associated with hot-starting these engines stem from the tendency of the fuel in the lines to vaporise due the residual heat in the engine.

Cold Start:

  • Master: ON
  • Mags: ON
  • Mixture: FULL RICH
  • Throttle: FULLY OPEN
  • Boost Pump: PRIME  -watch for the fuel-flow to rise from zero, allow it to stabilise for ½ second, then boost pump OFF
  • Mixture: IDLE CUT-OFF
  • Throttle: CRACK OPEN ½ INCH
  • Start
  • When the engine fires, smoothly slide the Mixture to FULL RICH

If the engine starts to die again, it may be necessary to “catch it” with brief bursts of the pump. Rarely an issue on a cold start.

Hot Start:

As previously mentioned, vaporised fuel in the engine fuel-lines is frequently the cause of difficult hot-starts. The simplest & best solution is to replace that fuel, with clean, cool, raw fuel.

  • Master: ON
  • Mags: OFF
  • Mixture: IDLE CUT-OFF
  • Throttles: CLOSED
  • Fuel Pumps: ON  allow the pumps to run for around 30 seconds to 2 minutes
  • Fuel Pumps: OFF
  • Fuel Tank Selector: CHANGE TANKS if possible.  This prevents you drawing the just-expelled warm fuel back into the engine.
  • Proceed as per Cold Start

Another method you may find of benefit, if you don’t want to run your fuel pumps:

  • Master: ON
  • Mags: ON
  • Throttle: FULLY OPEN
  • Mixture: FULL RICH – look for a quick spurt of fuel flow
  • Mixture: IDLE CUT-OFF
  • Throttle CLOSED, then OPEN ½ inch
  • Start

Flooded Engine Start

Some people advocate flooding the engine to achieve a hot-star Some manage it without malicious afore-thought… due the risk of catastrophic damage to the engine and potential loss of the airframe in a fire, it’s not a technique I recommend deliberately trying. However, should you find yourself with a flooded engine, proceed thus:

  • Master: ON
  • Mags: ON
  • Throttle: FULL OPEN
  • Mixture: IDLE CUT-OFF
  • Crank the engine until it fires
  • Mixture: to FULL RICH smoothly, whilst
  • Throttle: CLOSE briskly, set desired IDLE RPM
  • IMMEDIATELY allow the aircraft to taxi forward 1.5 aeroplane lengths, in case excess fuel has been pumped out onto the ground and lit up during the start.
  • Should you experience a cowling or induction system fire as a consequence of raw fuel all over the place from flooding it, KEEP CRANKING the engine to draw the fire back where it’s supposed to be! Get the engine checked.

CAUTION: Check your AFM -there will probably be a time limit on how long you can continuously crank your engine without it starting. DO NOT EXCEED that limitation. The consequences of exceeding may include:

  • Melting the lead plates in your battery
  • Melting your battery
  • Melting your Starter Motor

Your AFM will specify how long you can crank the engine for without risk of damage, and specify “rest” cooling-off periods between consecutive start attempts.

Flat Battery Starts:

I’m not going to try and tell you how to jump-start your aircraft -there are subtle but important differences in every airframe.  You’ll need to refer to your AFM for the good oil on how to proceed with an External Power start.

This however, is a technique that has worked well for me in the past when I have had an aircraft with a weak battery refuse to start in cold wx conditions. It’s based on the assumption that drawing massive current from the battery, as during an engine-start attempt generates heat -Lots of heat, which we are going to use to our advantage.

You’ll generally find out that the cold has sapped your battery when you make your 1st engine-start attempt of the day. That sickening, weak grinding of the starter-motor will tell you, as will the sight of a near-stationary propeller blade. Frustrating. However, all is not lost.

Now, if you’re cold-soaked battery is in a twin, pick the engine that usually starts most easily -there’s always one a bit more willing. It's also helpful to know what sort of Magnetos your engine is equipped with: Bendix, Impulse, Shower-of-Sparks etc. Your Impulse will usually be on the L Mag -start on that Mag alone. Similarly, if you have a Shower-of-Sparks mag, likely that's on the Left too. If it is a Shower-of-Sparks, you'll need to have the starter selected there too, even if you're doing an Armstrong start.

Basically what you want to do is:

  • Set your aircraft up as usual for an engine start, leaving off any unnecessary electrical items
  • Crank the engine within the limitations of your AFM, or until the battery simply will not turn the engine any further
  • Turn EVERYTHING (especially the Master) OFF
  • Walk away from the aircraft. Go make a coffee or something

Give it a good 10 minutes or so, which will allow the heat generated by your failed start attempt to warm the battery. When you get back to the aircraft, proceed as you usually would for a normal, cold-engine start. When (if!) it starts, get your generator or alternator on-line smartly, before attempting to start your second engine.

Of course, if this doesn’t work, you’ll need to jump-start your aircraft from an external power-source or an Armstrong start. Proceed as per your AFM.


As always, use all of the above advice at your OWN risk.