Plane & Pilot
Tuesday, October 23, 2012

Say When


When you should retract gear, reduce power, stop climb, initiate descent and more


I'm one of the world's luckiest pilots. On occasion, I'm allowed to fly some of the best new airplanes in general aviation. They're all different in many respects, yet they all share a number of characteristics. Fortunately, there are a few rules of forefinger that can help you in handling a variety of types. Not everyone will agree with me, but that's okay. As you cleverly guessed, I call my list, "Say when."

1] When should you power-up a cold engine for takeoff?
Depends on who you ask. I know of some pilots who feel you can run up any time the engine will take the power without stumbling; then, take the runway and leave town. On the other hand, I have several friends in the engine- overhaul business who feel you shouldn't even consider doing the run-up until the oil temp reaches 100 degrees F. Piston engines are made of a variety of metals, and all those materials must be up to temperature before you apply major power.

Fortunately, most modern airplanes are fitted with accurate digital engine analyzers that allow reading the temperature to the nearest degree. Those antique peanut gauges are rarely accurate enough to suggest when you're at 100 degrees.

2] When should you retract the gear after takeoff?
You'll hear a variety of opinions on this question, and it may seem hard to arrive at a logical answer. The premise isn't to retract the wheels until you know you won't be able to use them for an aborted landing on the remaining runway.

You can discard a few answers out of hand, however. One rule is to always wait until you're 500 feet AGL. Not such a bad idea, but on some airplanes with high drag signatures when gear is down, that could compromise climb performance at a critical moment when you need max altitude in minimum time.

Another old saw suggests, "Retract the gear when you can no longer see runway over the nose." Pretty dumb. How tall are you? Is your seat adjusted to the highest setting or the lowest or are you sitting on a cushion? Are you climbing at Vx, Vy or a cruise climb speed, all of which will demand different nose attitudes and provide a different slant-range view straight ahead? What's the slope of your top cowling, level, downhill or uphill? Answer all those questions, and you can see the "runway ahead" directive could vary by several thousand feet on the same day with the same load into the same wind.

There's a logical solution that doesn't demand much calculation, however. Look at your POH, and examine the takeoff and landing distance over a 50-foot obstacle. According to my Mooney's handbook, I need 1,384 feet for takeoff and climb to 50 feet and 1,786 feet for landing from the same height on a standard day at gross and sea level. Add, say, five seconds at 80 knots to recognize a failure (135 fps x 5), and you'll need to increase that total distance by about 700 feet. Assuming you have lightning reflexes, your brakes are brand new and you do everything else perfectly, you'd need roughly 3,900 feet of runway to land and stop. More realistically, considering that you probably didn't depart from the first few feet of runway, figure 4,000 feet to depart, climb to 50 feet, lose the engine and get your airplane back on the ground safely with nothing more than burned rubber. (Yeah, right.)



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