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.  Continue reading “Two Turbo Cirrus pilots realize they have not always been in level cruise flight”

Here’s how I would define flying “on the step.”

The known definitions for the term flying “on the step” are summarized below:

Flying “on the step” definitions:

"Flying the step" B-24 Pilot Training Manual for the Liberator, published 1945, page 68.
“Flying the step” B-24 Pilot Training Manual for the Liberator, published by Headquarters, AAF, Office of Flying Safety, Winston-Salem, NC, Revised May 1, 1945, p68.
    1. (verb) Getting “on the step” is a term used by the military.  The military citations always involve using momentum from slightly above the selected altitude to accelerate the aircraft and lower the nose into best cruise performance.  The procedure is an assist to formation flying by reducing process variation. The earliest documented origin for the term is found in the B-24 Liberator operating manual circa 1945.
    2. (verb) A procedure used to set an airplane in level flight for best cruise performance. The procedure can be initiated properly from below or from above the selected cruise altitude.  If flown correctly, the final cruise speed is the same regardless of entering the selected altitude from above or from below.
    3. (noun) A condition or state in cruise flight that produces a higher cruise speed which can only be attained through a unique technique. Subject matter experts have asserted it to be a myth or old-timer’s tale.

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The military uses “on the step” for cruise flight

Northrop T-38, credit wikiWings
Northrop T-38, credit wikiWings

Getting “on the step” is a term and procedure used by the military.  We’ve reviewed several aircraft noted for using the procedure. These include: the B-24 Liberator, Northrop T-38, and the Lockheed U-2 “Dragon Lady.”

The B-24 Liberator is the earliest documented reference we could find. We posted page 68 from the B-24 flight manual that includes illustration and instructions. Flying the B-24 Liberator “on the step” is standard procedure for establishing best performance in level cruise flight. The aircraft manual states to “always level off for cruising from the top in both speed and altitude.”

Charles Thornburgh wrote about flying the U.S. Air force Northrop T-38 “on the step” in his letter to AOPA. And, it’s also said that the Lockheed U-2 spy plane enters best cruise by using momentum from slightly above its selected altitude to get on the step in flight levels FL600 – FL700.

Getting “on the step” by using aircraft momentum from slightly above cruise altitude reduces process variation in establishing best cruise speed, which assists formation flying. Trying to climb into the selected altitude from below requires more process variation to reach best cruise speed, which can be a drag on formation flying.

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How does a normally aspirated SR22 get into level cruise at FL17500?

On the Step Cirrus SR22TN Turbo Perspective credit wikiWings
“On the Step” 2008 Cirrus SR22TN Turbo Perspective, credit wikiWings

We’re continuing a review of articles written about flying an airplane “on the step.” These articles help us to better understand flying in level cruise flight. Simple right?

A number of expert instructors have pointed out that many pilots tend to prematurely reduce power after leveling off at their selected altitude, which creates a mushing along flight attitude with the nose slightly up and tail low. Cirrus pilots in normally aspirated SR22’s that reach higher flight levels have posted comments on this type of flight attitude.

At an altitude of 17,500 feet a normally aspirated Cirrus only has about 55% engine power.  So, can a normally aspirated SR22 climb from below into flight level 17,500, it’s ceiling limitation, and use just engine power alone to accelerate into best cruise velocity?  If the plane is set at full remaining power (55% of 310 hp), how long does it take to get the plane’s nose lower and accelerate into best cruise speed? Continue reading “How does a normally aspirated SR22 get into level cruise at FL17500?”

A Bonanza F33A pilot gets on the step at FL150

On The Step, Cirrus SR22TN Turbo FL190, flight level 19,000 feet
On The Step, Cirrus SR22TN Turbo FL190, flight level 19,000 feet

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. Continue reading “A Bonanza F33A pilot gets on the step at FL150”

Flying on the step in a U.S. Air Force T-38

U.S. Air Force T-38, credit wikiWings
U.S. Air Force T-38, credit wikiWings
In a letter to AOPA Pilot, Charles Thornburgh says all airplanes are not equal in regard to flying on the step. His experience occurred on a cross-country flight in a T-38 in 1974. Here’s an excerpt from his description:

“We were flying from our home base of Holloman Air Force Base, New Mexico, to Homestead AFB, Florida, with a stop in Houston for gas. We were able to take off and climb with our two-ship straight to our cruising altitude of FL470 or FL490 (can’t remember which).

After we leveled off, the power was set for cruise. We spent a few minutes level at Mach 0.91, and then gently, without losing Mach, eased up 200 feet. We then nosed over and descended 400 feet, all the while not touching the power. As we then slowly returned to our cruise altitude, we noticed our speed was now Mach 0.93, where it remained.  I thought it was pretty slick. Maybe you can borrow a T-38 and check it out!”

 

Reference

AOPA Pilot, “Letters from our May 2016 Issue,” Charles Thornburgh, Pooler Georgia, July 2016, pg. 12,

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Ernest K. Gann cited flying on the step in Fate Is the Hunter

Eastern Airlines DC-3, National Air and Space Museum, Washington, DC, credit wikiWings
Eastern Airlines DC-3, National Air and Space Museum, Washington, DC, credit wikiWings

In Fate is the Hunter, Ernest Gann described setting his airplane on the step after they departed from San Francisco bound for Honolulu in a DC-4A.  The first and second officer onboard previously served as pilots in the Navy.

We pass through ten thousand feet and for a moment steal an additional hundred feet so we can descend back through it.  In the doing the ship can be set flying in a slightly nose-down position. Thus, “on the step” we will add better than ten knots to our air speed and also satisfy our sensual appreciation of flight.  A mushing airplane, regardless of its speed, becomes a miserable contraption to any dedicated pilot.  He absorbs this unhappiness through the seat of his pants.  There is no reason to believe this will ever change regardless of aircraft design.  A good pilot becomes morose and irritable in spite of what the most modern instruments proclaim unless his ship is “on the step.”  He will work endlessly to achieve that delicate angle and for this once and only once will prove the instruments wrong and the hair tips of his sensory powers more honest.  When the instruments finally admit additional speed, then the pilot is doubly content, for he has proof that the instruments are not his absolute master and he is not as yet altogether a mechanical man.” Continue reading “Ernest K. Gann cited flying on the step in Fate Is the Hunter”

What’s the lexicon for the term flying an airplane “on the step”?

"Flying the step" B-24 Pilot Training Manual for the Liberator, published 1945, page 68.
Flying “on the step,” B-24 Pilot Training Manual for the Liberator, published by Headquarters, AAF, Office of Flying Safety, Winston-Salem, NC, Revised May 1, 1945, p68.

What is the origin for the term “on the step?” The earliest reference I could find was from a 1945 Air Force training manual.

The B-24 Liberator operating manual has only one approved method for establishing best performance in level cruise flight. The pilot is to climb above the selected altitude and then descend into level cruise flight.

The manual states to “always level off for cruising from the top in both speed and altitude. The purpose is to let the airplane build up full momentum for cruising. If you go directly from a climb to level flight with a B-24, and reduce power, it will mush along at a high angle of attack and in a high drag attitude while trying to gain speed. It will fly sluggishly and inefficiently. The heavier your load, the more important it is to level off properly.”
Continue reading “What’s the lexicon for the term flying an airplane “on the step”?”

There’s a right and wrong way to fly an airplane onto the step

We’re continuing a review of several articles written about flying an airplane on the step. These articles, from the past decade and current year, are valuable contributions to help us better understand flying – in level cruise flight. Simple right? Continue reading “There’s a right and wrong way to fly an airplane onto the step”