JasonC wrote:
Yes but as Dave says, and many of us said earlier
True, and I acknowledged from the beginning that the final outcome could be exactly the same, though I would hope someone has tested it… 
Any effect within the boundary layer will have an integrated effect outside the boundary layer otherwise it would have no effect.
Ted wrote:
Any effect within the boundary layer will have an integrated effect outside the boundary layer otherwise it would have no effect.
Perhaps. But not on the stall warner.
JasonC wrote:
Perhaps. But not on the stall warner.
Who knows? It certainly depends on the stall warner. A stall warner isn’t usually an AoA probe that actually measures the AoA, and is positions somewhere on the nose (on fighter jets for instance). A stall warner on the wing will also be affected by the change the VGs cause. A pitot on the wing may be affected, so the IAS is also affected. Theoretically all, or most of the reduction is stall speed, may only be errors caused by the now erroneous pitot. Not very likely, but plausible. On the other hand, only the stall warner may be affected, so it signals correct, even with VGs. It all depends, but I also believe the changes to be very small in most cases.
Any effect within the boundary layer will have an integrated effect outside the boundary layer otherwise it would have no effect.
Indeed
The boundary is at infinity… or perhaps more accurately at the edge of the atmosphere
On the subject aircraft the pitots are on the nose, so unlikely to be affected.
Timothy wrote:
Jacko wrote:
Otherwise, you can just fly exactly as you do now
This is the difference between locating the aircraft 15 or 60 mins from the owner’s home. I have to get that balanced field length down, and 77kts, as opposed to 87, is the way to go. I have to take advantage of the VGs, but would prefer not to hear the stall warner.
I couldn’t agree more about 15 v 60 minutes, but (teaching granny to suck eggs), it all depends on the 15 minute runway. If it’s an ideal runway like Glenswinton with no obstacles on approach, we don’t have to fly the approach slower, we can just move our glide path so that we will flare another 20 yards or so short of the threshold. In other words, we can leave room to “take advantage of the VGs” after the flare and before the threshold.
If we have to drop over trees, wires etc. at the threshold, we aim to fly as steep and stable an approach as we can, at minimum safe ground speed. We’re unlikely to look at any instrument on short final, so the occasional cheep from the stall horn just confirms that we’re at 1.2 Vso, or wherever it sounded when we did a test stall as we descended to circuit height.
Since this is a public forum, it’s perhaps worth pointing out that these techniques, and particularly the latter one, may need a bit of practice/instruction – and readiness to go around as many times as it takes.
This is to do with take-off, not landing. Sorry if that was not clear.
The subject airfield is 800m with no significant obstacles.
