R44 down Rio de Janeiro

[Torquetalk]

It's clear that the pilot has LTE: But is that really the problem? I would bet good money that the low RRPM horn went off around the time "LTE" started and that the pilot ran out of power, which initially expressed itself as right yaw. The so-called LTE video in Australia is a good example of this, with in-cockpit evidence of how the event sequence developed.

AnFI
It is a while since I read the Gazelle accident in Yorkshire, but I can't remember that it was attributed to LTE in any singular and causal sense. The decision to fly given the dangerous wind conditions, together with the pilot's inexperience, were fundamentally what killed Paul and his wife.

In the Rio video, the pilot had surely passed the commital point without realising he was about to crash. LTE caused the aircraft to spin, but what caused the LTE and why did the aircraft crash? There is surely more afoot in this video than LTE.

[ReverseFlight]

Hi Torquetalk, you said:

I would bet good money that the low RRPM horn went off around the time "LTE" started and that the pilot ran out of power, which initially expressed itself as right yaw.

I appreciate this happening. On the other hand, do you (or any other Ppruner) envisage any situation where the low rrpm horn might not be activated throughout the process of LTE building up faster and faster into the spin ?

Thanks in advance.

[AnFI]

Basic Handling Education - I think......

LTE in this case is clearly Lack of Tailrotor Education

The R44 tail rotor does not run out of effectiveness

The R44 tail rotor does not run out of effectiveness

(unless there is some other factor: blocked pedal with telephone .... etc)

It is a common error to get the wind 'wrong' by 180 deg....
... when the behavior of the helicopter no longer makes sense the pilot's brain can seize.

He does press the left pedal but is too timid - he fails to get the response he expects - worse : he appears to get the opposite effect , as the weather-cocking increase beats his yaw response rate - the RIGHT yaw rate increases co-inciding with the (timid) rate at which he is applying LEFT pedal - the pedals appear to be working in reverse - he changes his strategy (after about 120degrees) presses the right pedal - the yaw continues through 'into wind' to 'tail wind' again and the pilot is out of control.

(Just like the Australian Video - link please).

(spinning helicopter, airspeed tends to zero - more power is required to sustain a hover - more left pedal is required than would previously have been sufficient (still no shortage of available T/R thrust))

If the pilot attempts any drastic actions at this stage he will probably be causing himself further problems (... like the Australian case where the pilot CLOSES THE THROTTLE - the RRPM fall to an extra-ordinary low rate, 50%!? (measure it..) fortunately there is enough time for the pilot to stop trying to do anything and the pilot discovers that everything is working just fine, without any pilot input, recovery results).

In Rio at 23.7 seconds this pilot attempts quite a hard but brief press on the left pedal which results in a small RRPM droop - the horn and buzzer come on (futher overloading our cautious aviator's brain) - at 24 seconds the pilot responds (almost instantly) to the horn by dumping the lever (as he has been pre-programmed to do) watch the helicopter drop sharply by about 10feet corresponding to an almost complete dumping of the lever for a short time.

The helicopter approaches the (not so) soft landing cushion and its pilot is already mentally committed to crashing because he is so confused. He fails to realise that the helicopter is not really yawing much anymore and is in a totally controllable state - resigned however - and with insufficient height to have the time to realise NOTHING IS WRONG - he continues with his pointless crash.


This is L T Ed

It is a while since I read the Gazelle accident in Yorkshire, but I can't remember that it was attributed to LTE in any singular and causal sense.

Correct - the AAIB did not conclude that - however it is fairly clear that was a highly probable cause ... radar trace shows approach down(40kt)wind, probably unintended. Rapid unexpected weather-cocking in a Gazelle is dramatic - large fin/long arm.
BUT i don't know - i wasn't there....
They are unlikely to conclude that since "LTEd" is not really recognised/taught.

I think the recommendations implied the Yorkshire accident was something to do with being taught in a "Registered Facility" on a Turbine instead of at a Type Rating Training Organisation - I think - and paperwork had not been correctly addressed and so it was recommended that there should be more oversight of training by the NAA - some rules were changed etc...

The R44 tail rotor does not run out of effectiveness


.... does anyone know the PA and temperature of this accident?

[rotorboater]

I don't agree I am afraid, the TR at full left pedal eats the rrpm and the horn goes off, possible to get out of at a few hundred feet but tricky at 50 feet, it happens very very quickly

[ReverseFlight]

The R44 tail rotor does not run out of effectiveness

I definitely remember Frank Robinson saying this ...

[AnFI]

Disagree Rotorboater....

It is ONLY pilot handling inexperience/inability through lack of exposure.

Pressing the left pedal (see my long boring analysis of the accident) did result in droop and at 24secs the pilot 'dumped the lever' for 1 second (unnecessarily) in response - all part of being out of control.

No height need be lost - if you use the lever to keep the height and the cyclic to keep level and press pedal as required to stop yaw - you will not have a problem.

It does not matter if the droop causes the horn to come on - since the engine is able to deliver more power the governor will add it (even if the pilot does not help it by adding throttle as required) the temporary RRPM droop does not threaten flight (and need not alter the height at all).

Ideally pilots should be able to distinguish the difference and preserve RRPM when the engine cannot deliver sufficient power to maintain RRPM - if the engine is working and the droop is temporary due to rapid pedal application then lowering the lever does not really help - it just makes you go down... remember lowering the lever closes the butterfly also...

You do not need to lose height when you lose 'grip' of the yaw...

It is more appropriate to stop yaw by using the pedals than keeping them still and lowering the lever!

It is only pilot mis-handling...

[AnFI]

unless

there was a defect or if hot and high? Carb or Injected?

[hillberg]

The Problem is not tail rotor,The problem is not power,The problem is people with $$$$$ and no piloting skills or any idea on what's safe, A total waste of a nice machine.

[AnFI]

hillberg

true true - (though some good people do not have the handling skills)

[Memphis_bell]

Fly aeroplanes....there much safer Helicopters FREAK ME OUT

[[email protected]]

The R44 tail rotor does not run out of effectiveness

unless you decay NR (for whatever reason) - when every TR in the world will start to lose effectiveness.

Unless this guy was hot and high it seems unlikely that he runs out of power (he is single pilot, no pax) unless he has some sort of engine/magneto problem.

[6th Gear]

You'll be saying that then to the HEMS chaps when there about to get you to hospital after your shunt on the motorway I take it?

[AnFI]

Crab - strictly true but not relevant since...

the engine also is capable of producing less torque (approximately linear with RPM) - the tail rotor is so over capable that it still has the capacity to counter the torque... even at a hideous level of low RRPM

(T/R effectiveness being proportional to the Square of RRPM.... the 'crossover' is VERY LOW)

[Old Age Pilot]

Fly aeroplanes....there much safer Helicopters FREAK ME OUT

Clearly the words of a professional

Just needs to go back to school and learn to spell.

[Torquetalk]

Reverse - If LTE is caused by an unfavourable vector, the aircraft torque reaction will accelerate to a given rate in nil wind. “LTE” caused by low TRRPM isn’t really LTE in this sense. In a moment of particular stupidity, I presented the TR of an R22 to a 40 KT wind and it spun so hard that it was clear that fighting the yaw with the pedal was pointless: it was easier to catch as the boom came back into wind: Pilot-induced LTE

The cause of the Rio accident remains to be determined. But there are a LOT of R44 accident videos which appear to share the same problem: over-pitching on approach to land. The “LTE” in these videos may be a secondary symptom of running out of power: More collective, excessive coning angle; decaying RRPM, more yaw;. As Rotorboat has pointed out; when this starts it will develop very quickly.


Crab - The correlator/governor system in the R44 can be response-rate variable aircraft-to-aircraft, and droop is, in-any-case, not hard to bring about. With 3 PAX and half a tank of fuel at sea level it is easy to over-pitch if the power requirement is high. A bit odd if only one person onboard admittedly; but downwind, high, hot; rapid lever application: still wouldn’t rule it out. There is a very unhappy conjunction with respect to the R44 involving poor training and overconfidence in the performance of the aircraft.

AnFI - I don’t know where you get the idea that the pilot in the Australian “LTE” video closed the throttle. Having seen the video many times and used it for teaching: this is news to me. The Yorkshire Gazelle accident is also not to be hijacked as an LTE accident: the investigators looked at a variety of possible factors which may have been contributory, of which LTE was discussed. Of no less importance was the stability of the aircraft type in difficult wind conditions (which were certainly present); and instructor over-confidence in a highly confident pilot with virtually no rotorcraft experience. Having known Paul, the report struck me as a thorough and balanced assessment of the information available. It was a very sad and unnecessary episode. Please do not cherry-pick a report to indulge in your current favourite subject.

[ReverseFlight]

Torquetalk, I agree that in a lot of R44 accidents the cause of the low rrpm horn going off were probably as a result of over-pitching rather than the LTE itself.

Assuming nil (rather than your 40 kt) wind then, could full LTE develop without the horn going off ? Picture the MRs turning anti-clockwise for the R44 and the main fuselage turning clockwise during LTE. Is the MR rrpm not referenced to the fuselage ? As the fuselage is turning the other way (clockwise), the tacho could sense that rrpm is sufficient. However, aerodynamic wise, the MR blades could be turning much slower (even without over-pitching) and this may not be sufficient for continued flight, even though the LTE itself would have the effect of off-loading power from the TR (thus producing more power for MR thereby creating lift).

This is just a theory as I have no figures to back up. Maybe someone out there does.

[loachboy]

In Summary ? - And One way pads.

Firstly here's my 2 cents worth.

Not to be too nit picky,

[email protected]

(he is single pilot, no pax)

The Journalist mentions 4 people inside the helicopter.

Torqutalk

AnFI - I don’t know where you get the idea that the pilot in the Australian “LTE” video closed the throttle. Having seen the video many times and used it for teaching: this is news to me.

Me too.

AnFI

In Rio at 23.7 seconds this pilot attempts quite a hard but brief press on the left pedal which results in a small RRPM droop - the horn and buzzer come on

Am I missing something here ?
Where do you get this info from or is it speculation ?

In Summary - Do we have a general consensus on what more than likely happened here ?

Un-arrested right yaw - Caused by lack of left pedal, due to machine weather cocking ?

Overpitching leading to LTE

LTE - due to a quartering tail wind ?

Because to be honest I am stumoed after reading all of this.


Please note: Definitely not having a go or being rude toward anybody here, just looking to learn.

Now to my original question.

How to land at a one way pad, heavy with the wind behind you without getting into this situation ?

(Admittedly if this guy was trying to land downwind he had way too much G/S on.)

Here's a brief run-down.

1.Come to a hover into some degree of headwind element perpendicular to the pad or so.

2.Pedal turn toward pad

3.And very slowly drift in over the pad to land.

Look forward to everybody's genuine input.

Regards

Loachy

[Torquetalk]

Reverse – The torque reaction is resolved by removing engine power: closing the throttle or entering auto. The disk fuselage may then follow the rotor direction then due to friction (right pedal needed in auto). Torque reaction shouldn’t be a function of RRPM but an opposite and equal reaction to the power supplied by the engine to overcome total drag.

My understanding is that LTE is independent of RRPM as its cause is unfavourable wind vectors and affects certain aircraft more than others. In the same sense, it’s hard to see how it could occur in nil wind if not in connection with overpitching/running out of power.

Loachy – thanks for the clarification re. numbers: If that is so, then it was always going to be a difficult approach and landing and the pilot was stupid to approach downwind. If that was the only available approach, then it should only have been attempted with less weight and having conducted a power check to assure a sufficient power margin. My [genuine] take on it is than this is basically a power/overpitch problem. The tail boom may have been pushed by the wind and he may have reacted too slowy etc etc: but the odds of running out of power with 4 in an R44, downwind, steep, into a confined area are very high indeed. Of course, this IS speculation: we won't have the facts until the report is out. But as said before, it bears all the hallmarks a dozens of similar R44 crashes.

Re. approach method: TBH it doesn’t really matter if you haven’t got the power to carry it out…

[hillberg]

At 90% Rotor RPM the tail rotor will never keep heading when you're pulling max pitch, With a full load, At High DA & A tail wind.

The Low RPM horn is too late when you have allready lost control.

[AnFI]

Hillberg

A tail wind

do you mean a tail wind or do you mean negative airspeed ie Flying backwards through the air ... in which case you could just turn 180deg and be flying with positive airspeed and yaw stabilisation from vert stabilizer, also at airspeed less power is required and so you cannot run out of the anti torque you might need ... or do you mean inadvertently zero airspeed?

pulling max pitch

Do you mean Collective lever hard against the TOP CONTROL LIMIT or do you mean lever at Full Throttle Operation...

With a full load

Does it make any difference what the load is if you have the lever at MAX PITCH?? (I suppose it does a little...)

and.....

Does the High DA make much difference to yaw control - since the engine and TR both perform proportional to Density?


At MAX PITCH and at High DA (low engine power?) with the RRPM already at 90% (and being at max pitch presumably decreasing rapidly....? ) the last of your worries is yaw - since you are crashing anyway for other reasons - but I still think the TR is powerful enough to counter any yaw short of actually having to crash to prove the tail rotor inadequate...

This guy in Brazil may have had any number of reasons to be unable to control his yaw - pax interference, wide shoes, object jammed in control run, mis-rigged pedals. BUT running out of T/R authority ain't one of them.


I think (almost) all pilots will have a similar problem to this when they encounter whilst inexperienced the extreme unexpected yaw of an unexpected tail wind catching them out. Most are lucky ....


In Yorkshire arriving at minus 20kts whilst not expecting it would be a schock ... that type is very stable into wind - the windier the better - the simple common pilot error of arriving downwind - makes the type very unstable in yaw at negative airspeed.

There are so many yaw incidents - Auz, redhill120, swansea120, gazelle, rio, irish wedding, - there might be some advatange into recognising a cause and helping people with some helpful advice - like:


some ideas....
Fly with the 'relative wind' on the nose - ie crab as required to prevent need for sideways and backwards airspeeds....
Dont be shy to use the pedals more aggressively if you need to assert yaw control.
If you don't understand what they are doing then be calm, smooth and respond slowly if you need to.
Stay level with the stick - regardless of the yaw rate.
Keep the height with the lever.
It's probably not a T/R failure.
It's probably not an Engine Failure.
Don't just give up and crash.
The lever controls your height and the cyclic keeps the disk level - you'll figure out the rotation eventually....
Don't misdiagnose engine failure, if you hear the horn - be smooth.
If you really have run out of pedal and it still just keeps yawing - then gently reduce the lever a little - and see if it helps - don't crash.
Are you sure you are using full pedal and still spinning?

Get more experience - soon