At Vx in DA4x on does hear stall warner all the way on the climb, Vx is VS0+3kts and the stall warner comes OFF at VS0+10kts
On TnG in hot days, it’s easy to mush stall DA40 on go-around with steep climb at Vx in turbulent air, it keeps wing level before it starts mushing toward ground and touch again, unless you relax back pressure or cushion against ground effect
While the stall warner is twitchy and comes on way before the stall, doing nothing about it does not seem healthy setup, the pilot head starts to get wired to ignore it…I think these are the few reasons why Vx is raised toward Vy? other than Vx climbs are usually unsafe and way less robust to distractions or gusts !
For DA42 it looks obvious to me, than at Vx you are unsafe in case of loss of power. For DA40, I would say that, as it’s very front centered, once you are in the stall it will get quickly the nose down for you, too quickly to get it flying if you are close to the ground. A part from that tendancy, DA40 are very safe, and a 6 pack of water in the trunk will help.
It’s true that the stall warner is acting a bit high, and when at flying school they don’t like you to stay too much in it, especially when you want to to a short field landing.
DA40D AFM doesn’t even mention Vx. As good old instructors are used to say “Ce n’est pas une situation d’avenir”.
greg_mp wrote:
For DA42 it looks obvious to me, than at Vx you are unsafe in case of loss of power.
Is true of any GA airplane near the ground. Just with twins, you’re probably slower than Vmca, and should immediately reduce power on the remaining engine too!
The previous reference to the height/velocity chart for a helicopter is important, and it is what I teach fixed wing pilots during this training. It is exactly that principle for airplanes too, though the values change a little. As is obvious for the helicopter, it should be similarly appreciated for the airplane, if you are slower than a certain speed (Vy or faster) and low, an engine failure will result in your reaching the ground with inadequate energy to arrest your rate of descent in time. I have said with certainty to both Transport Canada and the FAA certification departments that airplane flight manuals should be required to have height/velocity curves published just as helicopters are required.
Remember that all of these values are determined for certification based upon “average pilot skill and attention”. That’s what we want. When I sign off on demonstration of a design requirement, I want to be confident that what I have just done could be done by most pilots with slightly rusty skills, with a small amount of distraction. When I was taking training in the MD 500 helicopter, we were doing hovering autorotations. The flight manual tells that if you’re hovering higher than 5 feet AGL, you’re outside the “safe” part of the H/V curve. Lower than 3 feet, an engine failure is a non event, just correct for yaw with the pedals, and let it settle. At 5 feet, some reaction with the collective control is required, or you’re going to reach the groud with too little rotor RPM to arrest the fall. Once I had that masters, and because this was leading to training for carrying a load on the hook (you have to be more than 5 feet in the hover!), my instructor trained me for hovering autos from 10 feet. ’Lots of quick reaction, and pedals and collective have to be aggressively used, but it can be done. A very important skill for those times when someone is under the helicopter hooking up the load!
Awareness and practice! I’ll be teaching Vx/Vy engine failures to an instructor in the 185 amphibian on Monday…..
