Prop, partial power and rudder coordination
Prop considerations:
Great point regarding the type of propeller fitted. That will have a huge impact on glide performance. We haven't discussed drag associated with controllable types. The modeling in the app accounts prop drag to the extent the "about right" solution is correct. There are two drag "tweek" calibration features the user inputs.
The entire turnback from failure to touch down is less than a minute (admittedly, seems a LOT longer with temporal distortion when the adrenaline kicks in). The "I'd maintain aircraft control, analyze the situation and take the appropriate action" matrix is so condensed, that the "maintain aircraft control" part is going to take up most of the brain bytes. If the pilot exercised good checklist discipline prior to takeoff and is operating with a sufficient supply of clean fuel, there isn't much troubleshooting to be done. There is certainly nothing wrong with a couple of bold face (memory) items...boost pump, ignition and gas are obvious contenders; but not at the expense of aircraft control.
The app will model the drag of a windmilling propeller at high RPM (fine) pitch, so that means that condition is accounted for in the physics. I'd never fault a re-start attempt, but if I was in that situation, my boldface would be to reduce prop RPM and maneuver for landing. As we pointed out previously, CAFE testing has shown that there is no tactical advantage to trying to stop the prop to reduce drag for a power-loss event below 3000' AGL. Similarly, there is a minimum altitude below which troubleshooting is likely to channelize attention and reduce overall maneuvering SA (i.e., maintaining aircraft control). Obviously, the later will vary from pilot to pilot and situation to situation. It's a good place to establish a personal minimum. Mine are pretty straight forward: I'm below emergency bail out altitude, so my only option is to fly the airplane to the crash, and I prioritize accordingly.
Partial Power Loss:
When I was a young CFI in the late Paleozoic, I lost a jug in a Piper Cherokee shortly after takeoff when a valve exited the cylinder head through the valve cover. The remaining three continued to run until all of the oil leaked out--a good couple of minutes. Sufficient to maneuver to low-key for an alternate runway. The engine flamed out on final, but we had sufficient energy to land and clear the runway. By the same token, we lost an F-15 pilot in an RV-6 after a partial loss that turned into a complete loss of power. He maneuvered to low key in attempt to return to the departure runway in a low energy state, almost made the airport, but departed controlled flight at low altitude trying to stretch the glide end game and impacted the ground in 90 degrees of bank.
The takeaway is there is no one right game plan. It's probably best to assume complete power loss at any time and maneuver accordingly. A basic hip pocket will be to turn base for an alternate runway or maneuver to low key for the runway just departed. The app will actually do the math for the runway departed, and indicate when you are at low key with sufficient energy to make the runway.
For folks not familiar with the terminology, "low key" is the point on downwind that the airplane can glide to the runway out of a continuous base turn. The place your instructor would pull the throttle and say "just maneuver to the runway and land."
Rudder coordination:
Everyone that points out the need for proper training is spot on. Fail to coordinate, exceed critical angle of attack and the airplane is going to depart controlled flight. With an unintentional skid input it happens fast: https://youtu.be/cLg_LGjpL9Q. Likely non-recoverable at low altitude. If the airplane is properly coordinated and inadvertently stalled at low altitude, a recovery may be possible: https://youtu.be/BPD5xk1wgOw. This is why we move the AOA tone with the ball in the sound field (i.e., you hear it when the airplane isn't coordinated properly) and put a slip/skid ball on the visual display. It's critical for the pilot to have SA, especially in an airplane like an RV that doesn't provide much (or any) buffet cuing at low G.
Having said that, if the critical angle of attack isn't exceeded, then the airplane can't depart; so ultimately it's AOA awareness that is the key to maintaining positive aircraft control when you are maneuvering near the aerodynamic limit.
v/r,
Vac
Prop considerations:
Great point regarding the type of propeller fitted. That will have a huge impact on glide performance. We haven't discussed drag associated with controllable types. The modeling in the app accounts prop drag to the extent the "about right" solution is correct. There are two drag "tweek" calibration features the user inputs.
The entire turnback from failure to touch down is less than a minute (admittedly, seems a LOT longer with temporal distortion when the adrenaline kicks in). The "I'd maintain aircraft control, analyze the situation and take the appropriate action" matrix is so condensed, that the "maintain aircraft control" part is going to take up most of the brain bytes. If the pilot exercised good checklist discipline prior to takeoff and is operating with a sufficient supply of clean fuel, there isn't much troubleshooting to be done. There is certainly nothing wrong with a couple of bold face (memory) items...boost pump, ignition and gas are obvious contenders; but not at the expense of aircraft control.
The app will model the drag of a windmilling propeller at high RPM (fine) pitch, so that means that condition is accounted for in the physics. I'd never fault a re-start attempt, but if I was in that situation, my boldface would be to reduce prop RPM and maneuver for landing. As we pointed out previously, CAFE testing has shown that there is no tactical advantage to trying to stop the prop to reduce drag for a power-loss event below 3000' AGL. Similarly, there is a minimum altitude below which troubleshooting is likely to channelize attention and reduce overall maneuvering SA (i.e., maintaining aircraft control). Obviously, the later will vary from pilot to pilot and situation to situation. It's a good place to establish a personal minimum. Mine are pretty straight forward: I'm below emergency bail out altitude, so my only option is to fly the airplane to the crash, and I prioritize accordingly.
Partial Power Loss:
When I was a young CFI in the late Paleozoic, I lost a jug in a Piper Cherokee shortly after takeoff when a valve exited the cylinder head through the valve cover. The remaining three continued to run until all of the oil leaked out--a good couple of minutes. Sufficient to maneuver to low-key for an alternate runway. The engine flamed out on final, but we had sufficient energy to land and clear the runway. By the same token, we lost an F-15 pilot in an RV-6 after a partial loss that turned into a complete loss of power. He maneuvered to low key in attempt to return to the departure runway in a low energy state, almost made the airport, but departed controlled flight at low altitude trying to stretch the glide end game and impacted the ground in 90 degrees of bank.
The takeaway is there is no one right game plan. It's probably best to assume complete power loss at any time and maneuver accordingly. A basic hip pocket will be to turn base for an alternate runway or maneuver to low key for the runway just departed. The app will actually do the math for the runway departed, and indicate when you are at low key with sufficient energy to make the runway.
For folks not familiar with the terminology, "low key" is the point on downwind that the airplane can glide to the runway out of a continuous base turn. The place your instructor would pull the throttle and say "just maneuver to the runway and land."
Rudder coordination:
Everyone that points out the need for proper training is spot on. Fail to coordinate, exceed critical angle of attack and the airplane is going to depart controlled flight. With an unintentional skid input it happens fast: https://youtu.be/cLg_LGjpL9Q. Likely non-recoverable at low altitude. If the airplane is properly coordinated and inadvertently stalled at low altitude, a recovery may be possible: https://youtu.be/BPD5xk1wgOw. This is why we move the AOA tone with the ball in the sound field (i.e., you hear it when the airplane isn't coordinated properly) and put a slip/skid ball on the visual display. It's critical for the pilot to have SA, especially in an airplane like an RV that doesn't provide much (or any) buffet cuing at low G.
Having said that, if the critical angle of attack isn't exceeded, then the airplane can't depart; so ultimately it's AOA awareness that is the key to maintaining positive aircraft control when you are maneuvering near the aerodynamic limit.
v/r,
Vac
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