AUDIO♫: When the pedal hits the stop

Bell UH-1H Iroquois helicopter
image: © Commonwealth of Australia

My first posting as a brand new RAAF helicopter pilot was to 35 Squadron in Townsville, north Queensland, to fly the Bell UH-1H Iroquois. Day-to-day work was largely army support in the High Range military training area northwest of Townsville. At an average 1500—800 ft AMSL and with summer temperatures of 35 degrees and 100 per cent humidity, the Iroquois often came very close to its performance limit for approach and departure from pads when carrying loads. Towering take-offs or out-of-ground-effect (OGE) hovering with anything but the lightest load were rarely possible unless they occurred early in the cool of a morning.

This particular day I was required to do an ‘admin move’ for a four-man army survey team and their equipment. It was a mid-morning start and the task would be over quickly—a perfect opportunity for me as a junior pilot to get some command experience.

My co-pilot was an older fellow with previous Caribou experience, but with very little time as an Iroquois pilot. As we approached the designated landing zone (LZ) it became apparent that it was an OGE pad in a very small circular opening in the forest. The trees were perhaps 30m tall on the crest of a flattish ridge, and the approach would require coming to a complete stop in an OGE hover at tree-top height and then descending vertically down. The prospect of this required a few important checks before committing to the approach.

Approaching to an OGE hover without the requisite power margin would be disastrous, as there would not be enough power to hover nor to go-around; a crash into the trees would be inevitable. We circled around the pad as we calculated the power margin, outside air temperature and spoke with the survey team by radio regarding the weight of their equipment. The prevailing wind conditions would also be critical so we asked the survey team to throw a smoke grenade to allow us to judge the wind direction and strength. The brightly coloured smoke lifted slowly above the trees and then gently dissipated to the southwest.

Listen to this close call:

Once all these details were settled and we were confident we could get in and out of the pad, I made the first approach towards the north east into the very light wind. The first approach went smoothly and we descended vertically into the hole amongst the trees to lift three soldiers out with a small margin of excess power. As was the custom, I then swapped over flying with the co-pilot who took a turn to fly the approach and shift the next load. He copied everything I had done the first time, and the move was uneventful.

For the third and final approach, I had control once again and flew to the LZ exactly as we had done previously. As I approached the hover point above the opening to the pad, the crewman was leaning out of the rear door calling the clearance from the trees, and my co-pilot was calling the amount of torque I was using so that I had an idea of the power margin available to me. As I pulled in the collective and flared slightly to stop in the hover, something didn’t quite feel the same as before; I felt uneasy and couldn’t work out why. The co-pilot was calling torque readings slightly higher than we had used before, but something else was worrying me. Then I realised what it was—my left leg was extended much more than my right—I was using a lot of left pedal to stay aligned with the landing direction.

Just as I figured that out, the crewman called a small ‘tail right’ adjustment to keep my tail rotor away from a tree top below us. I applied the tiniest pressure on the left yaw pedal and felt something under my left boot that made my blood run cold—the pedal stop.

The events that followed took place so fast that they stand as a testament to the fine balance of forces that allow a helicopter to fly and what happens when one of those forces is no longer controlled. The turbine engine on an Iroquois drives the rotor blades to the left, but at the same time tries to rotate the fuselage to the right; the application of left yaw or anti-torque pedal prevents this—to a point.

Running out of left pedal means the aircraft will immediately start rotating uncontrollably to the right, and this is exactly what happened in my case. In the split second after my left foot hit the pedal stop, the aircraft started to rotate right; very fast. I don’t remember how many turns we did, as the spin was so fast I lost any reference point to the trees and I just struggled to keep wings level with the horizon.

As the pilots sit about two metres forward of the aircraft centre of gravity, centrifugal forces were pushing me outwards or towards the instrument panel. My mind raced in that clichéd way—time seemed to slow and I recalled the loss of tail rotor authority emergency procedure; roll off the engine throttle and settle down onto the ground. Removing the engine torque would stop the fuselage rotation and allow directional control to be regained, however, the one major downside of this procedure was that you were now without engine power and so a quick autorotation to the impact point would be the inevitable outcome.

So here I was above tall trees, left foot to the stop, spinning right, and to make matters worse, I was now beginning to lose height. Instinct made me pull up more on the collective, but this just increased the spin rate. I had to make a decision very, very quickly before we hit the trees—was I going to roll off the throttle and settle into the trees as directed by the flight manual? Yes or no? I am not sure where my next action came from, but the option of deliberately crashing was too much to bear.

I eased in some forward cyclic and unloaded the collective a little. It was a gamble, but I wondered if I could regain some control by getting the chopper into forward flight—like a weathervane effect. The trees were very close beneath me, but they did fall away slightly from the shallow ridgeline—I might just have enough height.

Moving the cyclic forward meant the aircraft started to do forward spirals rather than spinning on the spot and I managed to get some airflow over the fuselage. Unbelievably, it worked. Just prior to the skids hitting the trees, I regained forward flight, the left pedal came off the stops and there was that wonderful shudder of translational lift. We flew away from the trees. There was complete silence over the intercom. The crewman was the first to speak, ‘what the [bleep] was that?’

I felt physically sick. I had just escaped what almost certainly would have been a catastrophic accident with fatalities, and it would have been my fault. We did a wide level circuit to talk about things, check the aircraft configuration and settle my heart rate down. We noted the OAT had increased at least 10 degrees since we had started this morning and the wind was now quite a strong easterly. This accounted for using more left pedal on the NE approach to avoid weathercocking and using more power than before. The touch of left pedal to avoid the tree was the last straw, and we had exited the controlled flight environment. Luckily, it wasn’t a permanent exit.


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