Restricted takeoffs, VRS, and ground effect
Hello all! I've come across an interesting situation that could lead to some good discussion. Thanks in advance for any input!
I fly a dual engine Huey out of a large city. We have a helipad sandwiched in the middle of the city at ground level that presents some interesting challenges, both on takeoffs and landings. This thread is specifically related to the takeoffs we do to try to give ourselves decent aborts and single engine options while trying to minimize risk to the surrounding populace.
We regularly have to come in and out of an approx 200'x200' helipad in the middle of the city, heavy weight with about a 5-10% power margin for OGE. The helipad is surrounded by 100' obstacles in the immediate area with taller buildings (up to 200' or so) within about 3-400' in some takeoff directions. On takeoff, we often come straight up vertically (sometimes backing slightly) to about 150' or so before moving forward to give ourselves the ability to clear obstacles OEI in the event of an engine failure. If we had any issues before this committed point, we would attempt to abort straight down, or down and slightly forward, to avoid the nearby populated areas.
If I had an engine failure right at about 150' before moving forward, I would pull into single engine power and attempt to come down to the pad, pulling cushion as necessary at the bottom to try to hit the ground softer. This scenario raises what I think are a few interesting questions.
By pulling single engine power while descending in this manner, could I potentially get into VRS? Would I come out of it at about 50' when the aircraft starts to reenter ground effect, or ride it all the way into the ground?
I'm guessing we wouldn't get to a high enough rate of descent to enter in the first place, but it's still an interesting question IMO. Would the downwash velocity decrease as you entered ground effect, allowing you to decrease your sink slightly but still negating your cushion?
As a sidebar, does anyone else have to deal with similar LZs? What are your preferred methods of dealing with them? Thanks again for the input!