Pilot Complacency and Use of the HUAL Gauge
They say that confession is good for the soul, and that's probably more applicable to aviation than to any other endeavor.
Pilots tend not to share their errors and oversights, the human foibles that every one of them makes but keeps secret.
But those mistakes can serve a useful purpose.
For one thing, it's important to younger pilots to hear from veterans that even we have been there done that when it comes to embarrassing ourselves in our flying careers.
For another, transparency in human factors always helps the designers refine their products, so a good thing.
My career was blessed with very few errors.
I flew for 35 years without a scratch.
More specifically, that means no scratches or dings on the aircraft.
It doesn't mean I wasn't bright red with shame once or twice, realizing I'd screwed up, and the aviation god had looked out for me, while I sustained a serious ding to my ego.
In short, there was nothing wrong with the HUAL, Head Up And Locked gauge.
I just ignored it.
Here's an example of what can happen when inexperience, complacency and oversight meet up in the cockpit, and what a close call looks like.
The helicopter I flew was a French machine called an AStar.
Its actual nomenclature was AS350, referred to in industry circles as an Ecureil, the French word for squirrel.
They named it right; in certain flight regimes the machine was downright, well, squirrelly.
No other word for it.
Overall, the AStar is a fine helicopter, but it does have a few design flaws.
Like every aircraft, at least those designed and built by humans, which is most of them, the AStar's flaws and traps were cleaned up and refined over time, following input from the field.
One such design trap nearly cost me at least the embarrassment of a forced landing, if not something worse.
Regardless, the bottom line was, that the incident, had there been one, would have been a collaboration between the French engineers and yours truly.
It centered around the original AStar's white plastic oil reservoir.
To save weight and cost, always considerations in aircraft design, particularly for helicopters, the AStar originally arrived for duty with an oil reservoir made of opaque white plastic, sort of like a full milk jug.
This oil jug had a sight gauge on its side which, in every AStar I ever flew, was conveniently hidden halfway behind the reservoir.
It took an open cowl, a flashlight and a small ladder to view the gauge, plus several seconds start to finish.
My usual method of checking the oil level was to glance at the actual level of oil in the tank, which dark line was visible through the plastic.
Which was what I did one morning in early Spring when, on a hospital contract, I was dispatched for an emergency flight shortly after reporting for duty.
The beeper barked, I checked the destination, raced to the helipad and met the flight nurse.
Walking around the helicopter, I did my usual preflight of the big parts, most of the smaller parts, and all the fluid levels--I thought--then jumped into the cockpit.
I cranked the engine, flipped on the radios, and shortly I was ready to commit aviation.
I thought.
Takeoff was nominal, climbout simple, and soon I leveled at 2,500 feet.
Then, with no warning, five miles from the takeoff pad, the torque needle did a little whifferdill, bobbing down once, twice, then bouncing from zero to high, and back again in a curious imitation of a metronome.
This was not a good thing.
I watched the gauge with some interest, and sure enough the dance continued, with the torque needle all over the gauge, never settling on any particular value.
I informed the nurse that we were heading home, and then I did the standard 180 degree turn back to the helipad to sort things out.
I landed, shut off the engine, and went through my mental checklist of what the problem might be.
It could have been the gauge itself; they have been known to fail.
Perhaps the connection was loose? Helicopters do rattle and hum a bit, causing attachments to come undone.
Maybe the oil..
? I considered the design of the torque system: In the AStar, the torque indicator is called a wet gauge, since it relies on fluid pressure to work.
I mentally traced the routing of that oil line, and, starting from the gauge back to the engine, arrived at the reservoir itself.
The subsequent revelation increased my store of experience, and hopefully that of a few other AStar pilots' as well.
Lifting the cowl, I grabbed my step stool, a flashlight, and a wrench to check the actual level of oil in the reservoir.
To my amazement and chagrin, the tank was nearly empty.
A puddle of oil, enough to cover the bottom of the tank, was present there.
I looked again.
The 'oil level' I'd seen on preflight was nothing more than an oil stain on the interior of the plastic tank, embedded there after several fill ups, always to the same height.
The plastic had absorbed just enough of the oil to mark what looked for all the world like a tank with plenty of fluid.
I shook my head, cringing at the possibilities.
A modern gas turbine engine is cooled by two things: compressor air, and oil.
Diminish either of those two, and a turbine will quickly overheat.
At a certain point the heat will cause the engine to fail.
I had no idea how close I'd come to an engine failure that day, but it had to have been a matter of minutes at most.
It's one thing to run out of gas; running out of oil can cause similar adventures.
The bottom line was, that there wasn't a thing wrong with the other, equally important gauge in the cockpit--the HUAL, or Head Up And Locked gauge.
It was working fine; I just chose to ignore it, assuming that the oil level was okay, as it had been previously, and took off.
From that day on, I made sure I was looking at real oil instead of a stain and residue on the side of a tank where oil used to be.
I filed a report with the manufacturer about the potential for similar incidents.
Whether from my documentation or not I can't say, and rather doubt, but later model AStars arrived for duty with metal oil tanks, and a non-stainable sight gauge that forced pilots to physically check the level.
I certainly did after that.
And I paid more attention to the HUAL gauge as well.
Pilots tend not to share their errors and oversights, the human foibles that every one of them makes but keeps secret.
But those mistakes can serve a useful purpose.
For one thing, it's important to younger pilots to hear from veterans that even we have been there done that when it comes to embarrassing ourselves in our flying careers.
For another, transparency in human factors always helps the designers refine their products, so a good thing.
My career was blessed with very few errors.
I flew for 35 years without a scratch.
More specifically, that means no scratches or dings on the aircraft.
It doesn't mean I wasn't bright red with shame once or twice, realizing I'd screwed up, and the aviation god had looked out for me, while I sustained a serious ding to my ego.
In short, there was nothing wrong with the HUAL, Head Up And Locked gauge.
I just ignored it.
Here's an example of what can happen when inexperience, complacency and oversight meet up in the cockpit, and what a close call looks like.
The helicopter I flew was a French machine called an AStar.
Its actual nomenclature was AS350, referred to in industry circles as an Ecureil, the French word for squirrel.
They named it right; in certain flight regimes the machine was downright, well, squirrelly.
No other word for it.
Overall, the AStar is a fine helicopter, but it does have a few design flaws.
Like every aircraft, at least those designed and built by humans, which is most of them, the AStar's flaws and traps were cleaned up and refined over time, following input from the field.
One such design trap nearly cost me at least the embarrassment of a forced landing, if not something worse.
Regardless, the bottom line was, that the incident, had there been one, would have been a collaboration between the French engineers and yours truly.
It centered around the original AStar's white plastic oil reservoir.
To save weight and cost, always considerations in aircraft design, particularly for helicopters, the AStar originally arrived for duty with an oil reservoir made of opaque white plastic, sort of like a full milk jug.
This oil jug had a sight gauge on its side which, in every AStar I ever flew, was conveniently hidden halfway behind the reservoir.
It took an open cowl, a flashlight and a small ladder to view the gauge, plus several seconds start to finish.
My usual method of checking the oil level was to glance at the actual level of oil in the tank, which dark line was visible through the plastic.
Which was what I did one morning in early Spring when, on a hospital contract, I was dispatched for an emergency flight shortly after reporting for duty.
The beeper barked, I checked the destination, raced to the helipad and met the flight nurse.
Walking around the helicopter, I did my usual preflight of the big parts, most of the smaller parts, and all the fluid levels--I thought--then jumped into the cockpit.
I cranked the engine, flipped on the radios, and shortly I was ready to commit aviation.
I thought.
Takeoff was nominal, climbout simple, and soon I leveled at 2,500 feet.
Then, with no warning, five miles from the takeoff pad, the torque needle did a little whifferdill, bobbing down once, twice, then bouncing from zero to high, and back again in a curious imitation of a metronome.
This was not a good thing.
I watched the gauge with some interest, and sure enough the dance continued, with the torque needle all over the gauge, never settling on any particular value.
I informed the nurse that we were heading home, and then I did the standard 180 degree turn back to the helipad to sort things out.
I landed, shut off the engine, and went through my mental checklist of what the problem might be.
It could have been the gauge itself; they have been known to fail.
Perhaps the connection was loose? Helicopters do rattle and hum a bit, causing attachments to come undone.
Maybe the oil..
? I considered the design of the torque system: In the AStar, the torque indicator is called a wet gauge, since it relies on fluid pressure to work.
I mentally traced the routing of that oil line, and, starting from the gauge back to the engine, arrived at the reservoir itself.
The subsequent revelation increased my store of experience, and hopefully that of a few other AStar pilots' as well.
Lifting the cowl, I grabbed my step stool, a flashlight, and a wrench to check the actual level of oil in the reservoir.
To my amazement and chagrin, the tank was nearly empty.
A puddle of oil, enough to cover the bottom of the tank, was present there.
I looked again.
The 'oil level' I'd seen on preflight was nothing more than an oil stain on the interior of the plastic tank, embedded there after several fill ups, always to the same height.
The plastic had absorbed just enough of the oil to mark what looked for all the world like a tank with plenty of fluid.
I shook my head, cringing at the possibilities.
A modern gas turbine engine is cooled by two things: compressor air, and oil.
Diminish either of those two, and a turbine will quickly overheat.
At a certain point the heat will cause the engine to fail.
I had no idea how close I'd come to an engine failure that day, but it had to have been a matter of minutes at most.
It's one thing to run out of gas; running out of oil can cause similar adventures.
The bottom line was, that there wasn't a thing wrong with the other, equally important gauge in the cockpit--the HUAL, or Head Up And Locked gauge.
It was working fine; I just chose to ignore it, assuming that the oil level was okay, as it had been previously, and took off.
From that day on, I made sure I was looking at real oil instead of a stain and residue on the side of a tank where oil used to be.
I filed a report with the manufacturer about the potential for similar incidents.
Whether from my documentation or not I can't say, and rather doubt, but later model AStars arrived for duty with metal oil tanks, and a non-stainable sight gauge that forced pilots to physically check the level.
I certainly did after that.
And I paid more attention to the HUAL gauge as well.
Source...