This blog was formatted from comments on last week's Energy Management blog (>35, pitch/power discussion). Rich Stowell checked in and his comments, reprinted here, are especially valuable for all pilots and educators. His FREE "Learn to Turn" course offers even more extensive guidance.
The first principle of flying light airplanes is “Pitch + Power = Performance.” This succinct statement points to energy management. But it is so much more than that. Substitute angle of attack (AOA) for Pitch; thus, “AOA + Power = Performance.” Airspeed (V) and G-load (G) are proxies for AOA. Hence, “V + G + P = Performance.”
We can map out a go-around. Say, for example, we add go-around power while at 60 knots. Achieving max ROC is important in this example, which is a touch over 70 knots. Pushing the elevator control forward allows us to climb at a faster rate. This is counterintuitive (just like stall recovery) unless we understand the V-P relationship. Similarly, there are speeds on either side of Vy that, with go-around power applied, result in the same ROC albeit slower than max ROC. In one instance, we would have to push to speed up and thereby climb at a faster rate; in the other, pull to slow down and thereby also climb at a faster rate. Again counterintuitive, but normal in terms of the V-P relationship. We can correlate key speeds like Vy with their corresponding pitch attitudes, too, should we ever lose our airspeed indicator.
We can even map out and discuss a complete engine failure (P = 0), in which case the V-P diagram flips and becomes a Rate of Descent vs. Speed diagram (ROD-V). Correlate the glide attitude with your best glide speed here, too.
The V-G diagram, on the other hand, illustrates maneuvering performance within the confines of the airplane’s aerodynamic and structural limits. The same Vne line from V-P transfers to V-G. The same Vs line transfers as well, but the V-G diagram shows us all the stall speeds from zero G to the design limit G.
Whatever we say about the V-P diagram must be consistent with, and transferrable to, the V-G diagram and vice versa. Does anyone think we can substitute power settings along the V-axis on the V-G diagram, making it a P-G diagram?
When they happen to be discussed, V-P and V-G are presented as totally unrelated pictures. The reality is that three parameters tell us what the airplane is doing at any point in flight: V, G, & P.
The interplay between pitch and power on performance should be clear, as should the primary use of elevator and throttle controls. Also note that pitch is assigned as AOA/speed control and power as altitude control during the most critical of flight operations:
- The mountain, canyon, and backcountry flight environments (Mountain, Canyon, and Backcountry Flying, Amy L. Hoover & R.K. Williams; Mountain and Canyon Flying Training Manual, Lori MacNichol)
- The technical logic of airplane performance (Performance of Light Aircraft, John T. Lowry)
- AOPA articles (Fatal Instinct and Power and Pitch, Barry Schiff)
- The flippers and the throttle (Stick and Rudder, Wolfgang Langewiesche)
- Fundamentals of flying technique (FAA)
- Fundamentals of stall recovery (FAA)
- Go-around/Rejected Landing (FAA)
Likewise, airplane manufacturers assign pitch for AOA/speed control and power for altitude control during critical flight operations and emergencies in their airplanes. For example, see the amplified procedures in the Cessna 172P:
- Short field landing
- Landing without elevator control
- Glassy water landing (floatplane version)
- Engine failure
- Emergency descent through clouds
- Recovery from a spiral dive (in clouds)
Teaching Pitch and Power
Pitch. The elevator control moves fore and aft. The airplane’s response is seen as head-to-feet movement by the pilot. The primary effect is on angle of attack, which presents as changes in at least a couple of these: V, G, attitude, flight path. Possible secondary effects might include changes in rigging and engine effects, gyroscopic precession, angle of bank, and altitude.
Power. The throttle moves fore and aft. The primary effect is to move the airplane here-to-there (taxi from one location to another on the airport; fly from airport A to airport B; climb or descend from one altitude to another). Possible secondary effects might include changes in torque, p-factor, slipstream, and airspeed.
Do we inadvertently, negatively reinforce “use the secondary effect of pitch for altitude” as the norm, which by default makes all the above scenarios the exceptions? Or is “using the secondary effect of pitch for altitude” really the exception, especially since we must be in just the right slice of the envelope, close to the correct altitude profile already, and with speed that we either don’t need or don’t really care about to achieve the desired effect?
Does our approach to teaching the V-P relationship along with the trainee’s practical experience spent mostly in one part of the envelope contribute to the potentially dangerous pull response in other parts of the envelope? How do we push learning to the correlation level for the entire performance envelope?
Stripping away the apparent complexity in the FAA’s energy management chapter—especially with regard to the most critical energy state scenarios—returns us to the primary roles of pitch and power as illustrated on V-P and V-G diagrams. Hence my motto: “Pitch for the speed you need.”
