A Safe Pilot Is Always Learning
Training tips for students and pilots
Gauges Green, Airspeed Alive…
You’ve dutifully calculated your weight & balance for your flight. Weight and CG are within limits. You’ve completed a conservative performance estimate for all runways at all airports to be utilized. All are within limits for your aircraft and within your personal minimums.
On paper, the planned flight will work. As you’re rolling down the runway, though, how do you know you’re actually getting the performance needed for takeoff in the distance available?
Once the throttle is full, take a quick glance at the engine instruments. Just a quick glance is all you need to know if everything is in the green and where in the green everything is. Primarily, check RPM, oil pressure, oil temperature and fuel flow.
If you see anything out of the ordinary for the given conditions, immediately reject the takeoff by maintaining directional control, reducing throttle to idle and braking while smoothly adding back pressure and retracting the flaps. The key is knowing what ‘ordinary’ looks and feels like and being able to determine out of the ordinary with a simple, quick, non-distracting glance.
It’s not just about the gauge; it’s about the acceleration. Here, there can’t be too much of this good thing, but how do you determine if there isn’t enough? The rule of thumb I use was developed by Sparky Imeson and shared in his book, “Mountain Flying.” It’s known as the 70/50 rule and works as follows:
If you have not attained 70% of your lift-off speed by the time you have reached the 50% mark of the runway, reject the takeoff.
This works because most airplanes stop much better than they accelerate. In our Cessna 172S, we lift off somewhere around 55 knots. Seventy percent of this is 38.5 knots. Keep it simple and conservative and call it 40 knots. If you haven’t reached 40 knots by halfway down the runway, reject the takeoff.
This rule of thumb will not guarantee a climb rate sufficient to clear the trees or other obstacles on the far end. Plan ahead and be conservative.
Know your machine, the environment and your limitations. Of course, never feel forced to make or continue any flight because of pressure stemming from passengers or for any other reason.
Have fun out there!
Be safe, have fun and keep learning!