I had the pleasure of speaking with the Director of Flight Operation of a very large EMS helicopter company. We were discussing crashes. I mentioned that I had read a pilot's report to the NTSB stating that he had felt like his approach was fast and steep, as might occur if one was landing with the wind or "downwind" prior to initiating a go-around. As the pilot applied power to climb and accelerate, the aircraft began an uncommanded yaw that turned into several rotations in the yaw axis, loss of control, and a crash. People were killed.
The D.O. stated that this has happened more than once. Pilot's preparing to land at 2:00 am don't perform as well as they might at 10:00 am, and this is made apparent by studying HEMS crashes and hospital security-camera feeds.
All pilots know that they should go through a deliberate set of steps prior to landing. A before-landing-check should be verbalized, a statement of the planned path in (and out) should be made with an announcement of any hazards observed. If you only have one motor, the forced landing location(s) should be announced so that you and all others on board know where you are going when the engine quits.
Sidebar: If your pilot has not announced a visible hazard, like a tower or wires or a vehicle - she might not see it. You must announce it.
And - very importantly - the pilot should announce his or her opinion of where the wind is coming from and how it might affect the helicopter. Often when we land there is no wind sock on scene. So we must determine the wind direction and velocity through other means. If I state where I think the wind is coming from, and you disagree, now is the time to speak up.
Unfortunately for us, when we are out in the wee hours, we don't perform as well as we do during the day when fresh and rested. It's a proven fact. Read the NTSB reports. Our mood, performance, and judgement are degraded.
And that's why we tend to crash more in the middle of the night. When tired we just do the minimum to get by; to get the aircraft, crew and patient to the destination.
We can miss the details.
|If we are landing, and you see smoke from a stack flowing in the|
same direction we are flying, call a go-around. Landing downwind
leads to vortex-ring-state and loss of tail-rotor effectiveness
For this reason, at night
is when established procedures, protocols, checklists and company best-practices must
be adhered to. Like performing a high recon, like knowing where the wind is from, Like getting the aircraft slowed down per company policy. Like flying the correct angle.
Note that if I am falling short on any of these items, the only persons who can point this out to me are you two or three crew members flying with me. There is no second pilot to catch my mistake.This means you have to know how things are supposed to look and feel, and speak up if something is off. I am a damned good pilot. And I haven't crashed.
This makes me just like your pilot.
As a human being, I am subject to make a mistake, like a guy in Texas did. He initiated a go-around, aborting his approach because it didn't feel right. And it led to a crash. In another event - on video - another guy did the same exact thing and got into the yawing spin. That helicopter went around about 45 times, yes forty-five
times, before the pilot initiated a climb in desperation. He got some altitude , reduced power, and let the helicopter fall off to one side. The aircraft weather-vaned, stopped spinning, and he was able to fly out of it.
"Well pardon the crap in my pants..."
So, perhaps we should focus on getting it right the first time in - especially at night. Some aircraft are more susceptible to loss of tail-rotor effectiveness than others, but they are all subject to vortex-ring state, and hitting things. In any helicopter, a small decrease in rotor RPM - such as might occur during a massive power increase when aborting an approach and starting a climb - will equate to a much greater loss of tail-rotor/fan RPM and authority. In a BK the ratio is 8 to 1 TR to MR. And when that tail rotor stops being effective we will push more pedal until it either is effective or it stalls.
Note: In the first event referred to here, the pilot reported that he did NOT apply FULL pedal against the yawing spin. We should be ready to apply full
pedal to control the aircraft. This has never happened to me, but experts say full pedal will arrest the yawing motion. Both pilots reported that "the cyclic stopped working." This led the DO to surmise that the aircraft, when spinning rapidly - on the order of 360 degrees per second
- can get out of sync/phase with cyclic inputs. If the nose is down, and the pilot inputs aft cyclic, the delay in cyclic effect means that the aircraft has spun to the point that the input is reversed. This is something to consider, and more reason to avoid letting the yaw get away from us. Apply full pedal against yaw as required...
Crews can assist with determining wind direction. Look fo flags in the wind, smoke from stacks, groundspeed versus airspeed comparisons, and wind correction headings inbound to the destination. All these serve to tell us the wind direction and speed. Wind can change near the ground, and we have to be ready for this, and ready to call a go-around.