Chairmanofthebored
24th May 2005, 16:59
This is a copy of an internal memo from a helo operator of the S76. I came to me from a friend. I find it hard to believe that a safety officer can circulate this to other pilots and be taken seriously. Talk about announcing that you don't know a thing about your job and forwarding a lot of misleading drivel. :(
Vortex Ring on approach to ..............h?
It was the strangest feeling: 100% torque on both engines (T5 was OK), 15 degrees nose up, over the heliport already (at 75 feet or so) and we still had a 500 FPM rate of decent. Now what?
Let me back up a bit. We had an uneventful flight on a decent enough day. The descent checks were done about 15 miles back while going past the airport. Started slowing down and we completed the landing checks. I was planning on being at the cardinal position of “1000 feet, 1 mile back”, and was, thank you very much. For me, I know I’m on the proper approach slope if I put the base of the windshield wiper (where it comes out of the nose) right on the heliport edge closest to me. When I do that, I am always going over the fence exactly as I am pulling through single-engine power (55% torque). A little flare (no more
than 10 degrees) and whammo…we’re there. Every time! And today seemed no different. When we intercepted the ingress track, the F/O indicated that we had a slight head wind and pointed out the flag on top of the hospital. I quickly glanced over and sure enough, he was right. Yet, when we were going over the fence and I needed more power, he called “limits”. What? Nothing left? It felt like any other normal approach. Could it be vortex ring? Not me. Then my mind shot back to my training: to get out of vortex ring, lower the collective (can’t do that here; too low), or fly out of it by pushing the cyclic forward. So that’s what I did. I decided to go around. My right hand began
moving forward but before I could announce “going around”, something strange happened. It was like someone deployed a drogue chute. The rate of descent zeroed out instantly. I was still 15 degrees nose up and at the far end of the heliport, so all I did was level the machine and backed up a bit, and it was over. I couldn’t believe it. Just an inch or two on the cyclic and it made the world of difference.
We discussed it as a crew and nobody noticed anything unusual. I was the only one shaking. They thought it was just a botched approach with too much speed. Only I knew the combination of effects and “felt” the machine (being the sloppy link that connects the cyclic to the collective and pedals).
While we were waiting for our 2 minutes before shut down, the F/O pointed up to the flag and the windsock. Both were now showing the wind as opposite from where it was on final (which would have put us downwind). Did the wind change that much in just a few seconds, or did we both see it wrong? The weather was unsettled that day, and the forecasts were calling for a wind shift. But that fast?
Since then it was pointed out to me that the logging guys have another method of getting out of vortex ring: move the cyclic laterally if you have no room to move it forward. This will also allow you to fly out of your own downwash…just sideways! So, if you can’t arrest the rate of descent, or it increases with an increase in collective pitch, THINK VORTEX RING AND DO SOMETHING ABOUT IT! NOW!
Vortex Ring on approach to ..............h?
It was the strangest feeling: 100% torque on both engines (T5 was OK), 15 degrees nose up, over the heliport already (at 75 feet or so) and we still had a 500 FPM rate of decent. Now what?
Let me back up a bit. We had an uneventful flight on a decent enough day. The descent checks were done about 15 miles back while going past the airport. Started slowing down and we completed the landing checks. I was planning on being at the cardinal position of “1000 feet, 1 mile back”, and was, thank you very much. For me, I know I’m on the proper approach slope if I put the base of the windshield wiper (where it comes out of the nose) right on the heliport edge closest to me. When I do that, I am always going over the fence exactly as I am pulling through single-engine power (55% torque). A little flare (no more
than 10 degrees) and whammo…we’re there. Every time! And today seemed no different. When we intercepted the ingress track, the F/O indicated that we had a slight head wind and pointed out the flag on top of the hospital. I quickly glanced over and sure enough, he was right. Yet, when we were going over the fence and I needed more power, he called “limits”. What? Nothing left? It felt like any other normal approach. Could it be vortex ring? Not me. Then my mind shot back to my training: to get out of vortex ring, lower the collective (can’t do that here; too low), or fly out of it by pushing the cyclic forward. So that’s what I did. I decided to go around. My right hand began
moving forward but before I could announce “going around”, something strange happened. It was like someone deployed a drogue chute. The rate of descent zeroed out instantly. I was still 15 degrees nose up and at the far end of the heliport, so all I did was level the machine and backed up a bit, and it was over. I couldn’t believe it. Just an inch or two on the cyclic and it made the world of difference.
We discussed it as a crew and nobody noticed anything unusual. I was the only one shaking. They thought it was just a botched approach with too much speed. Only I knew the combination of effects and “felt” the machine (being the sloppy link that connects the cyclic to the collective and pedals).
While we were waiting for our 2 minutes before shut down, the F/O pointed up to the flag and the windsock. Both were now showing the wind as opposite from where it was on final (which would have put us downwind). Did the wind change that much in just a few seconds, or did we both see it wrong? The weather was unsettled that day, and the forecasts were calling for a wind shift. But that fast?
Since then it was pointed out to me that the logging guys have another method of getting out of vortex ring: move the cyclic laterally if you have no room to move it forward. This will also allow you to fly out of your own downwash…just sideways! So, if you can’t arrest the rate of descent, or it increases with an increase in collective pitch, THINK VORTEX RING AND DO SOMETHING ABOUT IT! NOW!