...isn't. Sometimes. However, it may be the ultimate “it depends” scenario. Foremost, if you have a power loss during initial climb and a suitable landing surface is in front of you, use it! If that’s not the case and you are looking at a face full of trees, or worse, houses and school buses, AND you have sufficient energy to maneuver, then some degree of maneuvering to a suitable off-field landing surface may be warranted. If there are zero point zero options within glide range other than the airport you just departed from, you have the right training, the airplane has sufficient performance, ambient conditions are favorable and you have considered the option pre-flight, you may elect to try to return to the airport or runway. Energy at touchdown (wherever that may be) is also critical. It may be a better choice crash landing off-field at lower speed than trying to land on-field with a significant tailwind.
Here's a look at the factors that impact the ability to turn back to the takeoff runway after losing power. Keep in mind not all aircraft have the performance capability to execute a turn back, regardless of ambient conditions. And ALL aircraft, regardless of how well they perform are impacted by ambient conditions: https://youtu.be/2_Xb3CAXfzM
And to paraphrase Bob Hoover, you must fly the airplane all the way through the crash. Manipulating the controls doesn’t stop until what’s left of the airplane does. Data show that if you maintain aircraft control (that is don’t stall), your odds of surviving the landing are good. If, however, you exceed the critical angle of attack prior to touchdown your odds of becoming a statistic are significant.
The actual physics of the turn back are straight forward, but since so many factors are involved, it’s difficult to make an informed guess as to whether a turn-back is a feasible option. I’ve recently been testing an iPhone-based performance app called “TLAR.” That’s military slang for “that looks about right.” A beta version integrates real-time METAR data (or manual inputs) and actual aircraft performance updated once per second to calculate a “fly/stop” cue (i.e., the point at which I can still land straight ahead on remaining runway) and a “turn back” point if the airplane possesses sufficient performance under ambient conditions. A first-opportunity, low-altitude turnback to a short runway is a “maximum performance” maneuver: https://youtu.be/F_RFKlUhdeE. In this test, you hear me apply flaps—that is purely to compensate for the residual power produced by my fixed pitch prop. My flaps 40 IDLE glide angle is the same as my flaps up, engine off glide angle.
Here's a plot of AOA and stall speed margin from the turnback through touchdown:
In the video, you may have noted the stall warning tone as I “square the corner” (intentionally applying G to bleed some energy). That corresponds with the AOA peak in this figure. Note that my speed margin is reduced to about 4 knots and actual AOA is within 2 degrees of critical AOA.
An important concept in aircraft handling is that AOA correlates directly with G. When we apply G, AOA increases. Optimum bank angle for maneuvering during a turnback is 45 degrees, and even in a glide, that’s about a 1.4 G maneuver. It’s this small increase in G that gets folks in to trouble and can lead to an accelerated stall. This figure plots both AOA and G for the maneuver. Note that every time there is a G peak, AOA peaks as well:
Another way to see that is to plot AOA and G rates. Note how the two marry up:
One of the critical factors impacting the ability to turn back is climb performance. Our RV’s are pretty good climbers, but that’s not the case for all airplanes. Shortly after flying this test, I took off in a Cherokee from the same runway under similar ambient conditions. In this case, the TLAR solution said a turn back simply wasn’t an option:https://youtu.be/t7OwK3LPtBU.
Since stall is the enemy and not everyone is equipped with AOA, nor is everyone trained or comfortable max performing the airplane close to the ground, the app allows you to adjust bank angle and Vref for the turnback calculation. By decreasing bank angle and increasing speed, it may eliminate a turn back option, but it will keep you within your own comfort envelope.
Fly safe,
Vac
Here's a look at the factors that impact the ability to turn back to the takeoff runway after losing power. Keep in mind not all aircraft have the performance capability to execute a turn back, regardless of ambient conditions. And ALL aircraft, regardless of how well they perform are impacted by ambient conditions: https://youtu.be/2_Xb3CAXfzM
And to paraphrase Bob Hoover, you must fly the airplane all the way through the crash. Manipulating the controls doesn’t stop until what’s left of the airplane does. Data show that if you maintain aircraft control (that is don’t stall), your odds of surviving the landing are good. If, however, you exceed the critical angle of attack prior to touchdown your odds of becoming a statistic are significant.
The actual physics of the turn back are straight forward, but since so many factors are involved, it’s difficult to make an informed guess as to whether a turn-back is a feasible option. I’ve recently been testing an iPhone-based performance app called “TLAR.” That’s military slang for “that looks about right.” A beta version integrates real-time METAR data (or manual inputs) and actual aircraft performance updated once per second to calculate a “fly/stop” cue (i.e., the point at which I can still land straight ahead on remaining runway) and a “turn back” point if the airplane possesses sufficient performance under ambient conditions. A first-opportunity, low-altitude turnback to a short runway is a “maximum performance” maneuver: https://youtu.be/F_RFKlUhdeE. In this test, you hear me apply flaps—that is purely to compensate for the residual power produced by my fixed pitch prop. My flaps 40 IDLE glide angle is the same as my flaps up, engine off glide angle.
Here's a plot of AOA and stall speed margin from the turnback through touchdown:
In the video, you may have noted the stall warning tone as I “square the corner” (intentionally applying G to bleed some energy). That corresponds with the AOA peak in this figure. Note that my speed margin is reduced to about 4 knots and actual AOA is within 2 degrees of critical AOA.
An important concept in aircraft handling is that AOA correlates directly with G. When we apply G, AOA increases. Optimum bank angle for maneuvering during a turnback is 45 degrees, and even in a glide, that’s about a 1.4 G maneuver. It’s this small increase in G that gets folks in to trouble and can lead to an accelerated stall. This figure plots both AOA and G for the maneuver. Note that every time there is a G peak, AOA peaks as well:
Another way to see that is to plot AOA and G rates. Note how the two marry up:
One of the critical factors impacting the ability to turn back is climb performance. Our RV’s are pretty good climbers, but that’s not the case for all airplanes. Shortly after flying this test, I took off in a Cherokee from the same runway under similar ambient conditions. In this case, the TLAR solution said a turn back simply wasn’t an option:https://youtu.be/t7OwK3LPtBU.
Since stall is the enemy and not everyone is equipped with AOA, nor is everyone trained or comfortable max performing the airplane close to the ground, the app allows you to adjust bank angle and Vref for the turnback calculation. By decreasing bank angle and increasing speed, it may eliminate a turn back option, but it will keep you within your own comfort envelope.
Fly safe,
Vac
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