Originally Posted by
nomorehelosforme
In its final report into the incident, the National Transportation Safety Board (NTSB) in the US concluded tailwinds, potential downdrafts and turbulence were the probable cause of the loss of control of the aircraft.The "most significant factor" affecting survival of those on board the helicopter was the post-crash fire, according to the findings.
The aircraft was "not equipped, nor was it required to be equipped, with a crash-resistant fuel system".
After the crash, the helicopter company announced that it would fit crash-resistant tanks to its fleet.
https://www.bbc.com/news/uk-england-sussex-55674015
I followed Watson's instructions. Here is the
actual NTSB report . It is astonishing to hear that the same operator had done 180,000 landings between 1999 and 2017 at the same location without any accidents. The mishap pilot himself had done 581 landings at that spot, presumably in the same type and for the same mission (sightseeing with 6 or 7 pax). This was the second landing at the same location for the mishap pilot on the accident day. And it wasn't hot neither (actually 12 deg C, winter in Arizona). The a/c weight at the time of accident was declared as 5,022 lbs (300 lbs below MTOW). Compared to a hot summer day in the canyon, on that winter afternoon in February they must have had plenty of excess power to shove into this Fenestron.
The report basically accepts that a freak wind caused the accident.
Maybe doing the same thing again and again without a problem causes complacency to creep in? A priori, the approach to the west helipads would be flown with visual reference to the terrain. Add a strong tailwind or gust, and take your eyes a moment off the airspeed, and within a second he might have lost effective translational lift.
However freaky the gust, it wasn't entirely unexpected.
The seventh pilot to land entered the canyon at 1709. During his approach to the west pads, his intended destination, he recalled that the helicopter's tail swung rapidly due to strong winds and he applied significant right pedal and crabbed the helicopter to maintain the approach.
The last helicopter to land before the accident entered the canyon at 1710 and touched down about 2 minutes before the accident occurred. The pilot had experience flying in mountainous terrain, knew of the presence of 15-20 kt winds from the east, and thus anticipated windshear during the approach. While turning toward the west pads, he experienced a strong wind that swung the nose of the helicopter about 90° to the left.
90 deg swing (yaw) in a sightseeing flight while approaching to land with the gorge opening underneath? That certainly has the potential for the tourists to spill their champaign! Why didn't the pilots of the two prior flights radio a caution to the colleague coming right behind (5 minutes)? What culture is that that doesn't oblige you to report such, or at least encourages you to do so?
Maybe the mishap pilot did everything possible to avoid the crash, to no avail. There is something strange though:
A pilot on the ground at the landing site reported that the accident helicopter began to decelerate as it approached the landing pads and entered a nose-up attitude, then turned left toward the landing pads, transitioned through several pitch oscillations, and drifted aft.
I am not sure to understand what this "drifting aft" could mean.
Either way, the pilot coming in just 5 min before the mishap pilot, reported that he managed to handle the situation as per text book (increase airspeed, give the Fenestron the boot). Somewhere else we read that this pilot now has misgivings that he didn't alert is fellow pilot. I would feel the same. Here is what this pilot told the accident investigators:
The airspeed rapidly decayed and it required all of his effort to maintain control of the helicopter. As the helicopter began to descend, he increased collective to arrest the descent and was able to maintain control by pushing the cyclic forward and right to increase airspeed while applying full right pedal to keep the nose straight. He successfully landed the helicopter on one of the west pads.
(By the way, not sure whether maybe
decreasing collective instead of increasing torque, and pushing cyclic to the left, that is
into the torque-induced turn and in this case away from the terrain, would be a better approach? But hey, he survived, and I wasn't there...)
The mishap pilot had 2,400+ HRS TTRW, of which 1,000+ on type. The latter acquired over the past four years flying for this operator. However, he only flew 2 HRS in the past 30 days before the accident. The report doesn't dwell on this any further.
Another point that puzzles me is that 2,396 HRS of 2,423 HRS TTRW were PIC. That only leaves 27 HRS dual instruction over his entire flying career. These are also the numbers stated in the "Accident Report" (not the investigation report, but the initial report to the FAA). Don't they record recurrent training and line checks as "Dual"?
So what do we learn?