Police Helicopter loss of tailrotor authority 2019
 

Not sure if this one has been shown, I did a search and couldn't find it, a very interesting video

Interestingly no mention of performance planning or checking - with the reported aerodrome figures on 1064 amsl and + 28 deg, some straight line and basic interpolation would give 8000'amsl and + 14 deg at the accident site ( approx) and a DA (again approx) of just under 10,000'.

They had recently taken on fuel and had several people in the back - where was either the proof of HOGE performance or the questioning that it was available?

For mountain SAR, you want more than just HOGE because you will be hovering and may not be able to do so perfectly into wind. Did they have that?

Also it is noticeable that the pilot has far fewer overall hours both total and on type than the co-pilot - who should have probably been the HP in tricky conditions???

Insufficient mountain flying training at high DAs perhaps - low time on type pilot in a heavyish aircraft - perhaps a dummy approach to a higher hover to assess the TR performance prior to getting close to the ground? Plenty of ways to avoid this incident - they were all VERY lucky.

There is no such thing as LTE. Its a Myth!
This looks like a classic RH pedal turn in a B212/412 (Torque Turn) followed by a failure to enter sufficient left pedal (power Pedal) to stop the yaw.
There is not a helicopter built that the yaw cannot be stopped if sufficient pedal is applied.
There are no aerodynamic conditions that equate to LTE or TR Stall.

It is quite possible he just ran out of physical TR authority - much more likely on a Bell - or simply didn't put enough left pedal in to counter the large MR Tq demand at the DA coming to the hover.

LTE was a Bell myth because their TRs weren't powerful enough.

CRAB, not so sure about this. The classic conditions are to pedal turn with MR torque, the wind catches the pilot out at the 220 degree position in the turn then failure to apply, sufficient power pedal to arrest the yaw. You can see the cab does about a 360 before the hard landing. Then

miraculously it lifts into the hover with stable zero yaw. You are right about the Bell Myth though. If the torque was already high then the result could be a slight overtorque but that is preferable than a hard landing with undercarriage damage. My armchair assessment is yawing rate to high for the conditions and the failure to apply opposite pedal to arrest the yaw. Its a big movement of the LH pedal in the big bells to control the yaw.
This is why we should always guys to do spot turns in strong winds in the real helicopter as it exposes those for whom their feet don't dance quite quick enough. The FSTD doesn't cut the mustard for this kind of practice. There is a very good presentation for EASA on this at the following link: (LTE=Big Myth)

Where's Nick? Little Bell tail rotors are up for debate again !

DB - we are singing from the same hymn sheet here but I see very little right yaw before the loss of control - I think he has failed to anticipate the loss of ETL as he slows down and as the power comes in, the TR position just isn't enough to counter the MR Tq.

I know you have flown the 412 and it is noticeable on ours how, with a crosswind, it gives a nasty kick as you slow down to the hover as the fin loses effectiveness and the TR starts to take the anti-tq load - I just think the Bell 2 blade TRs often need more pedal than you would expect at low speeds.

I have been put in a 'reaching full left pedal' scenario at high DA in Cyprus in a Wessex and it looks just like the accident video here - fortunately I had height to take control and dive on speed where these guys didn't.

I would like to see their pre-flight performance planning

At 21 mins in the EASA video, there is a slide which perfectly explains how these guys got caught out.

But, he later states that right yaw with full left pedal cannot happen - I know from experience that it can but he is making things fit his (overall accurate) story - that is a shame because a 'one size fits all' solution is only 90% of the truth.

And this is one of the reasons we can never get air assistance on SAR missions around here anymore.

Got to agree with Crab here: In a Bell 206, right yaw with full left pedal absolutely *can* happen! If you're OGE (even down low) with a strong wind off your five o'clock and your left leg is extended way out, you best be ready for some uncommanded yaw as that thing may very well decide to point itself into the wind. On the ground with the ship not running, walk back and stand about 15' behind a 206 at the 4-to-5 o'clock position, and see how much inflow to the tail rotor is blocked by that big dang fin. It's an eye-opening experience.

I think you have misunderstood. The aerodynamics, wind etc dictate that when the cab is yawing right (unanticipated yaw) full left pedal will stop the yaw without further recovery action. (In Counter c/w rotors). Now if the wind when x-wind exceeds TR authority it won’t happen in that heading but further around. In extremis as the cab yaws downwind or back into wind the yaw will stop if sufficient pedal is applied. This is the only valid teaching point and it’s sole aim is to prevent the hard landing we saw in the video. As the presenter states, as the rapid unanticipated yaw occurs to the right the inexperienced pilots arse falls out as he misdiagnosis a TR Thrust failure. The TR PEDAL CURVE tool aptly describes when the yaw is rapid at the key hog point if opposite pedal not applied quickly enough.

you can’t argue that any helicopter design is not capable of holding heading with yaw at least into wind otherwise fwd flight would be impossible.

the rest of the argument is hot air and misunderstanding. If you still believes in LTE then you are a statistic waiting to happen.

When you are in the situation of full left pedal and still yawing right, the only thing that will save you is when the aircraft weathercocks back into wind and the aerodynamics move you back to the pedal curve by dint of the new wind azimuth.

Full opposite pedal will stop the yaw - but that has to be caveated with the understanding that it might happen not immediately and more right yaw is likely to be experienced before you finally stop.

The problem is having the nouse to apply full pedal and leave it there until the yaw stops.

However, if the wind is zero or vey light and you are at a DA and AUM where the TR has reached the limit of thrust - you will keep going round until something else changes.

Certification for light helos only requires demonstration of adequate yaw control up to 17 kts crosswind but plenty of pilots fly in more than that, probably without considering the implications of that certification.

CrabI we are aligned dodododododo...........the twiglet zone!

Possibly on more than one thread DB:ok:

N2/NR trimmed at the "top of the green" makes a big difference. Never flown a UH-1 but have about 1500 in a 205A-1 and the Nr sounds a little slow or not trimmed up to max to me.

Must have been wind direction and attempt to HOGE as it pulls off a 540 and then happily flies away in the opposite direction from IGE?

Doesn't sound like the N1 topped as no NR decay. Life gets even more interesting when you are close to TR control limits and N1 tops!!

Up and under approach is sometimes better - set max power first, approach climbing up the hill facing straight at it, as the speed decays you can judge easily if you will have HOGE and if not just let the thing turn around and go back where you came from!

RVDT - I agree with your last sentence as it is assessing likely performance before you get to the hover - I have always advocated a level decel for exactly the same reasons as you describe, if you get to a speed where you reach max Tq/N1/N2/ITT, you throw it away early.

Flying the single engine Huey on SAR work we had a simple landing guide as to performance capability, although forget the numbers now. Straight and level at 60 knots 500' above landing site and note TQ, pull to rotor bleed or reaching engine limit and note TQ. If TQ difference exceeded a particular figure (forget) OGE was possible, if below but above another figure (forget) IGE was possible, if below a certain figure (forget) a run on would be required, other figures gave a zero/zero capability. Naturally you only applied if you were into wind. :E

Megan - we had a very similar process for the Wessex back in the day.

Performance issues aside, had it all gone seriously Pete Tong, those unsecured rucksacs in the cabin with various sharp and pointy ski poles & ice axes protruding would have been unwelcome to say the least.

Pilot asleep on the pedals, classic LTE.