Aviation Safety Corner
GREETINGS! For this month's topic, I would like to start a new
discussion on, "Initial Climb Strategies." Exploring the pros and cons of using your airplane's best-rate
versus best-angle climb speed after liftoff. This is Part I of IV.
Now. Let's start our discussion, "Close to Stall." After leaving the runway on takeoff, why should you climb at Vy (best rate of climb airspeed) or Vyse (best critical-engine out rate of climb airspeed in a twin), rather than climbing at Vx (best angle of climb airspeed) or Vxse (best single-engine angle of climb airspeed? Here are some good arguments for making the initial climb at the appropriate Vx airspeed even under "normal" conditions. Here's a list of points to ponder.
1. At Vx (or Vxse), the airplane stays closer to a familiar, safe landing area (the airport) until a safe altitude is reached.
2. In case an engine fails shortly after takeoff, if you're climbing at Vx, there will be more runway remaining ahead on which to land.
3. The lower ground speed on a Vx climbout means that less "emergency" runway ahead will be needed for stopping after landing.
Recently, I've seen other publications recommend that you maintain Vx until you've climbed higher than any obstacles ahead, then accelerate to Vy. The trouble is that, for an intentional initial climb at Vx, you will have to set a pitch attitude considerably higher than what's needed for acceleration to Vy. Then, when you decide to transition to Vy, you will have to lower the nose to accelerate. That's a lot of adjustment of both pitch attitude and airspeed right after liftoff, while in initial climb.
The data in the takeoff distance chart or graph in your AFM (aircraft flight manual) are usually based on lifting roll at a prescribed airspeed, then establishing a pitch attitude that allows the airplane to accelerate to 1.2 times the stall speed at 50 feet above the ground. But Vy for most airplanes is approximately 1.4 times the stall speed. So, even that AFM takeoff chart would have you initially climbing at a rather low airspeed. (Which is why it is not a good idea to try to duplicate your AFM takeoff data.)
Your actual Vx climb airspeed may be even closer to stall speed than a factor of 1.2. That Vx figure doesn't take into account the possibility that you may react slowly to a sudden engine power loss during that very-nose-high initial climb. Nor does it account for the possibility that you might be late, or too gentle, in pitching over to a glide attitude that will enable you to get back to the surface in shape to land, with enough residual airspeed to glide and then flare for touchdown.
If your Vx is low enough, the pitch-over might just require a zero-G maneuver to preserve enough airspeed following a power loss. In general, the AFM-recommended landing approach speed is usually at or above 1.3 Vso (stall speed in landing configuration). Best rate of climb airspeed, Vy, is usually about 1.4 Vs (in climb, usually clean, configuration). Best glide airspeed (dead engine) also is usually about 1.4 Vs (in the clean configuration).
We already noted that the regulations require the take-off data in your AFM to allow 1.2 Vs (takeoff configuration) at the 50-foot altitude in initial climb. Unless you try extra hard, your slowest landing touchdown speed--even in a taildragger, and even if you're trying for that fabulous "full-stall" landing--is probably no slower than 1.1 Vso (landing configuration, full-idle power).
Nobody really lands fully stalled, except experienced bush pilots, and they only do it with the tail wheel already on the ground. Now in Conclusion, Remember what happens if you're fully stalled: The nose is dropping, and you're usually out of aileron control. That's no way to be touching down, and you don't want the nose to be dropping in the flare, two feet above ground level.
Don't miss next month's Aviation Safety Corner, when we'll discuss, "Mysterious Relation" and "Vanishing Horizon." This will be Part II of IV.
Happy New Year! SAFE FLYING!
Larry G. Harmon
FAA AVIATION SAFETY COUNSELOR
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