David Rogers, a Beechcraft Bonanza F33A pilot, believes there is a step. He’s written about getting his normally aspirated airplane “on the step” for best cruise performance at 15,000 feet (FL150).
David mentions the problem some pilots can have when climbing and then “[rolling] the prop back to 2300 or 2100 rpm without allowing the aircraft to accelerate . . . .” Power reduction too soon can cause the plane to settle into less than optimal cruise speed. Other pilots describe the problem as a slightly nose high and tail low, which results in the plane mushing along in cruise. It’s not always obvious to pilots.
At higher altitudes such as FL150 it can be harder to get a plane into level cruise flight. Based on David’s article, the available cruise power for a Bonanza F33A at FL150 is limited to about 45% – 55%. He says, “Getting ‘on the step’ occurs when the aircraft is at the maximum velocity for the particular altitude and power available.” He believes using aircraft momentum from slightly above the selected cruise altitude is a best practice to accelerate the plane into optimal cruise speed.
In a climb to cruise from below, how long does it take for a normally aspirated Beechcraft Bonanza at FL150, with just 55% power, to achieve best cruise speed? David doesn’t say. And, I’ve not flown a normally aspirated plane at that altitude. But I do fly a turbo-charged Cirrus in the flight levels and at 100% power it can take up to 2 minutes to reach best cruise speed when climbing from below into the selected altitude.
David Rogers full article is available online.
Pilot Observations
- Several variables can affect getting an airplane into best cruise performance, these include; pilot process, temperature, density altitude, weight and balance.
- If you’re on an IFR flight plan obtain ATC approval for deviations above your assigned altitude.
References
Rogers, David F., “Is There a Step?” Internet PDF, URL , 1996
Rogers, David F., Short Biography
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