Two Turbo Cirrus pilots realize they have not always been in level cruise flight

Cirrus SR22TN-G3 Turbo, smooth air 10,500 feet above the GA traffic, blue sky, photo credit wikiWings
Cirrus SR22TN-G3 Turbo, smooth air 10,500 feet above the GA traffic, blue sky, photo credit wikiWings

I know two pilots that have flown a Turbo Cirrus for about 3 years.  And, they recently realized their Cirrus has not always been established in best performance cruise flight based on reading AOPA Pilot and letters from fellow aviators regarding Barry Schiff’s article “Stepping Along, ‘On the Step’ Fact or Fiction.”

Barry says, ” many pilots tend to prematurely and impatiently reduce power after leveling off.  The throttle often is retarded before the airplane has had a chance to accelerate to normal cruise speed.  In a sense, the airplane is established in a subtle form of mushing flight.”

When entering a selected cruise altitude from below, a Cirrus SR22TN Turbo may require up to 2 minutes at full power to pull the airplane into level cruise flight.  But have you ever listened to a turbocharged TCM IO-550 engine at full power in level cruise flight?  If you have then you understand why some pilots may pull the power back after about a half-minute.  In less than a minute a turbo Cirrus will accelerate and appear to be in level flight. 

But has the plane accelerated to best cruise speed?  What airspeed do you check?  The knots indicated airspeed (KIAS) will be slowing down.  But for a piston aircraft capable in the flight levels, True Airspeed (TAS) is the acceleration indicator the pilot should be watching.  True Airspeed will continue to advance when KIAS shows signs of losing pace.  Leave in full throttle and you’ll notice a subtle pitch lower of the nose and a better TAS.

Powering to best cruise speed in a climb from below can be affected by a number of variables; such as, airplane weight, balance, and density altitude.  That’s why a pilot that choses a routine altitude but with more fuel or an extra passenger in back or baggage (weight & balance) or hotter day (density altitude) may require a change in process to establish best cruise performance. The time required at full power may change.

Entering cruise altitude from slightly above reduces the variables required to reach best cruise performance.  The procedure lowers the nose and uses airplane momentum to accelerate up to or past the best True Airspeed. Getting “on the step” from above can be a good process check.  You’ll be able to compare TAS and pitch against your procedure for entering cruise in a climb from below.

We’ll look at Cirrus Aircraft operating manual instructions to establish cruise, and later at a procedure to get “on the step” from slightly above a selected altitude.

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