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-   -   EC 130 down at the Grand Canyon (https://www.pprune.org/rotorheads/605275-ec-130-down-grand-canyon.html)

Robbiee 20th Jan 2021 18:11


Originally Posted by FH1100 Pilot (Post 10972083)
In the discussion of this accident in one of the Facebook rotorcraft groups, a guy - presumably a pilot but you never know - said, "I believe the primary cause of this accident was LTE."

It seems that there is a whole generation of pilots who've come to accept the myth of "Loss of Tail Rotor Effectiveness." They believe that the tail rotor can somehow get into a condition ("cavitation?") where it stops producing thrust and the helicopter will spin around like a top even with full power-pedal applied. This of course is nonsense. But pilots are loathe to apply and hold *full* pedal, even if it's called for. Because...I guess...if you do that in a hover when you're near a power limit, you could easily have an engine temperature or torque exceedance. And nobody wants that! But it's hard to understand why pilots would accept a crash as opposed to saving their skin.

The thing to remember...well, *two* things to remember are that: 1) The helicopter is a big weathervane and wants to point itself into the wind; and 2) As long as it's spinning, the tail rotor *never* stops working. If more pilots would just understand these two basic things, I'd bet there'd be fewer crashes where the pilot gets out and says, "It was LTE! The aircraft failed me!"

As a pilot who believes in LTE I can say that, the tail rotor does not stop producing thrust (the idea that we think that, is the myth). I am not "loathe to apply and hold full pedal" ,..that is completely ridiculous! The corrective action for LTE is full left pedal/forward cyclic. Why would someone who believes in LTE, not believe in its text book correction?

With LTE the airflow over the tail rotor simply becomes disrupted (and if not readily attended to by the pilot) can cause the nose to spin about. The tail rotor is still working just fine, but the pilot needs to be awake on the pedals, to prevent a loss of control.

LTE is not a "get out of jail free" excuse. The accident is still "pilot error", LTE just explains what he let happen.

,...but I'm just a poor 22 guy. :(

Wide Mouth Frog 21st Jan 2021 02:24

I think it's missing quite a lot to call this pilot error.

If you look in the docket at the Operations Factual Report you'll see this

There are two main approaches that the pilots make to the pads at Quartermaster. The decision of which approach to make is determined by the location of the pad the pilot decides to land. When landing on the east pads, the pilots maneuver the helicopter south over the river and continue over a saddle-shape in the terrain, referred to as “the notch.” After passing over the notch, the pilot makes a descending left turn and touches down facing to the west-northwest. The alternate approach, commonly used when landing on the west pads, entails the helicopter crossing over the river and entering into a 3,800-foot long box canyon; the distance back the pilot maneuvers into the canyon is determined by their assessment of the wind.
Now it's a little surprising that there's no mention of wind direction, but the inspectors won't have licked that up off the floor. Somebody gave them the idea that the approach was dictated by the pad to be used, and that is actually completely consistent with the observed arrival pattern of the helicopters. Now listen to the Chief Pilot

When the Chief Pilot was queried as to why the pilots are not provided any guidance on which approach to make and pad to land on, he responded that because the wind conditions are unknown, he would not be able to predict which pad/approach would be favorable. He stated that “as a commercially-rated, instrument-rated professional pilot, they've got to have some latitude to make” a decision as pilot-in-command and “have a degree of operational control… they have the final authority… and I expect them to exercise that from time to time.” Instead he ensures that the pilots are trained to always make an approach into the wind.
Sounds like common sense until you remember that three 'commercially-rated, instrument-rated professional pilots' late that day did exactly the same as the accident pilot, and the last one very nearly came to grief also. And then from the final report

Multiple Papillon pilots stated that the winds at Quartermaster were unpredictable and that the wind direction could drastically change during an approach into the landing site
Am I the only one sensing a disconnect between the chief pilot and those regularly flying the line ? As the final report says, Papillon has automated weather reporting systems at other nearby landing sites so why not this one ? And why not some landing limits that reflect the actual wind conditions at the site.

And what about that 'Letter of Agreement' between the operators to cut out 'unnecessary chatter' on the special frequency ? That doesn't seem to encourage pilot reporting of unusual conditions.

All these subtleties present in the operations report were airbrushed out in the final, in favor of freak wind and LTE. I don't think this was pilot error, I think it was an accident waiting to happen. And unless the operation has been altered as a result of this report, then it's waiting to happen again.

fdr 9th Feb 2021 03:16

Fire Safety

RHC's improvement in the tank design was commendable. Being Avgas, its a critical factor for survival post-impact where g and survival space have not compromised the outcome. Having a circular saw beside the inside of the tank would concentrate the corporate mind. The addition of foam inserts to remove explosive potential, and to further assist in fluid escape would add minimal weight, and reduce the fuel volume minimally. As an STC, it sucks to develop, but as the OEM, it is a straightforward enhancement.

I went through that issue with the B737 center wing tank and the aux tank fun and games. Compared to the OEMs inerting generator system, foam inserts made mode sense and saved more than cents. Foam seems to be desirable on any tank if you happen to ahve a chance of having bad days and being near by.

Fenestrons are neat.

There is a natural fractional delay in thrust response as the circulation effects are over a larger area than just around a TR blade. The surround helps in increasing directional stability in forward flight with the downside that quartering tailwind conditions will reduce stability more than having a smaller keel area at the tail rotor. That means the stability is slightly more dependent on wind vector than a common or garden TR. And they are still cool. The delay in developing thrust adds to a greater excursion if perturbed.



[email protected] 9th Feb 2021 06:45

As John R81 says and fdr states - a problem with Fenestron equipped aircraft is the size of the tail fin, designed to offload the fan in the cruise, which can aggravate the weathercock tendency when operating out of wind - this was true on the Gazelle and the 365.

To pick up on Robbie's point, yes you know that full pedal is required to stop that unexpected yaw but do you actually put in that full pedal - because it feels so wrong - when you need it?. Reports from other 'LTE' incidents indicate that pilots who were sure they applied full pedal actually didn't.

Another issue is that with experience of Fenestrons you learn to anticipate the different handling characteristics, just as you adapt to the steering or brakes on a new car.

I currently fly B412EP - standard TR but only 2 blades which is very hard work even in a moderate crosswind, compared to my previous ride, the AS365, which used to sit with a 40 Kts crosswind with no problems.

With the Grand Canyon crash it seems, as ever, to be a number of factors contributing to the accident - the unpredictable wind and poor wind awareness by the pilot plus comms and training perhaps - but I don't think the Fenestron is to blame.


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