FLYING HEAVY ... ADDENDUM

Acknowledgements: Thomas P. Turner (Mastery Flight Training Inc.)

Reader and well-known flight instructor Zdravko Podolski writes about last week’s LESSONS on airplane weight, centre of gravity, stability and control:

“One minor correction to an otherwise excellent FLYING LESSON. For any given weight, an aft loaded conventional airplane will actually fly at a lower angle of attack than if it was forward loaded. One of the reasons why the Bonanza was so efficient... Happy to go into it in more depth if you wish, but if in doubt just remember what the horizontal stabilizer does”.

Tom responded: 

... You’re correct: if the pilot maintains a constant vertical speed an aft-loaded airplane will fly at a lower angle of attack. To visualise this, think of an airplane maintaining altitude while loaded at the rear of its envelope. It will tend to pitch upward compared to a more fully forward loaded airplane. Because it pitches upward, it tends to climb. Consequently, the pilot must trim the nose further down- to a lower angle of attack - to maintain altitude. 

What I meant to emphasize is that the aft-CG airplane will tend to pitch up, increasing its angle of attack, unless the pilot provides more forcethan normal for the vertical speed he/she desires. Apply the “usual” pressure necessary to flare for landing in an airplane loaded farther aft that you’re used to, and the angle of attack will increase more than you’d normally expect. The lower breakout forces and reduced pitch stability (both described in last week’s LESSONS) make this an even greater hazard for the pilot not used to flight at the aft limits of the loading envelope. Thanks for helping me clarify and emphasize this point, Zdravko.

FLY SAFE!