The Right Thing At The Right Time

by Gary Wiblin

I popped down to our local flying club primarily to have a beer, but also in the hope of gathering some fodder for this column. I didn't have long to wait.

One of our more experienced PPL's had a captive audience under his spell as he regaled his eager listeners with his own version of after-take-off checks. They were enthralled. So was I! I listened on with incredulity.

Our fearless aviator was trying to have us believe that power should be reduced to the cruise-climb setting as soon as possible after lift-off. Only then should the wheels be retracted. I couldn't believe that an otherwise intelligent person would dream up such an insane procedure. I asked him to elaborate. He said that because the aircraft handbook specifies that the engine should not run at full power for more than five minutes, he had decided that it was obviously bad for an engine to do so and therefore the power should be reduced as soon as possible after take-off. This is definitely not the case for a number of reasons, two of which deserve discussion.

Most aircraft piston engines are indeed rated for full power for only five minutes. In normally aspirated engines (not turbo-charged) this is only really a consideration at or near sea level. Those pilots flying aircraft with normally aspirated engines from airfields with elevations in excess of 4000 ft have nothing to worry about. Their aircraft engines will be unable to develop more than about seventy-five percent power anyway.

Aircraft engines are in any case designed to work hard and continuously and a good 'burn' on every take-off is good for the engine. It helps to remove any glazing off the cylinder walls normally caused by continuous operation at low power settings.

Another thing about piston engines is that if something is going to go wrong with it after take-off it will normally be as you reduce power. In other words, don't fiddle. Leave well enough alone until you have reached at least 1500ft AGL.

You do not want to be burdened with unnecessary menial tasks shortly after getting airborne. Why create more work when you have enough going on as it is? Up until the gear retraction point you should still be ready for the possibility of an abort. Beyond gear retraction it is all systems go and you want to be gaining precious altitude as quickly as possible. You definitely do not want to be reducing power at this stage.

Remember too that one of the busiest times for a pilot is shortly after take-off. You are leaving ground-effect in a possibly heavily loaded aircraft, you need to be wide awake for the possibility of an engine failure after take-off, you need to initially maintain runway center-line, and of course you need to comply with the clearance given to you by ATC.

The drill for engine failure in a light twin is to immediately stop the yaw caused by the failed engine, select the attitude required to attain and maintain blue line speed (vyse, best rate of clime on one engine), confirm that the good engine is developing full power, retract the flaps to optimum (in the case of a go-around), and retract the undercarriage. We would then have to: Identify, Verify and Feather. As can be seen there is quite a lot to do and even a well prepared pilot can have his hands full avoiding pending disaster in such a situation. This is why we need to reduce the workload as much as possible for the after take-off segment. There are two ways we can do this:

We can choose a gear retraction point and if anything goes wrong before that point, we can abort the take-off. This point may very well be at some height above the runway, but with sufficient length remaining to land back on the remaining runway. This means that if an engine now fails after gear-retraction point, we will not have to worry about retracting the undercarriage as part of the clean-up drill.

If we leave the engine running at full power until at least 1500ft AGL and then experience engine failure we will also not have to apply full power on the good engine as it will already be developing full power. All that will be left to do will be to identify the failed engine (dead leg, dead engine), verify it (EGT, fuel flow, throttle back and check no change in rudder pressure), and feather.

Personally I never reduce power after take-off on a normally aspirated engine, even when taking off from sea level. I have found that by the time I climb through about 4000 ft the manifold pressure has reduced to about 25 In. anyway and I am then able to reduce the rpm to that required for continuous climb, thereby negating the need to reduce power after take-off only to have to again increase the power as the engine begins to lose manifold pressure due to the constantly increasing altitude.

In the training environment students should be made fully aware of the dangers of over-boosting an engine and using the correct power settings in the cruise, but should also be taught to prioritize tasks shortly after lift-off and not be fixated on reducing engine power. Leave it running flat out for a while. It likes it so.

(Gary WIblin is fast becoming one of our favorite contributors on issues of aviation safety. You can subscribe to his Aviation & Safety Magazine by contacting him at the email address below -- ed.)

FMI: garywiblin@new.co.za